Volume 10, Number 3, September 2023 IEEE Power Electronics Magazine

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pelsmagazine.ieee.org

Vol. 10, No. 3 September 2023

For your engineering success

Features

14 U nveiling the Microworld Inside Magnetic Materials via Circuit Models

Han (Helen) Cui, Saurav Dulal, Sadia Binte Sohid, Gong Gu, and Leon M. Tolbert

23 Recent Advances in Capacitors Used in Wide Bandgap Power Circuitry

Ron Demcko

88 Departments & Columns        4 From the Editor New Developments in High-Frequency Passives Ashok Bindra        8 President’s Message Advancing Power Electronics Innovation and Industry Engagement Brad Lehman       64 PSMA Corner WiPDA Celebrates Tenth Anniversary Renee Yawger       68 Industry Pulse Consumer EV Standards and Voltage Trends Kristen Parrish and Stephanie Watts Butler

29 A ddressing Power Decoupling in High-

Performance, High-Frequency Applications Using E-CAP

Mukund Krishna and Luca Vassalli

36 W  ireless Inductive Charging

of Battery Electric Vehicles Is Coming

Darko Vracˇar, Sebastian Wüstner, and Alkiviadis Boulos

43 A Survey on Impedance-Based Dynamics Analysis Method for Inverter-Based Resources

Heng Wu, Fangzhou Zhao, and Xiongfei Wang

52 Future Directions of Commercially Available Supercapacitors

Compared With Rechargeable Batteries for Renewable Energy Applications Nadee Arawwawala, Nihal Kularatna, and Don Charles Uvindra Sirimanne

      73 Expert View The Ascent of GaN Alex Lidow

61 From “Power Electronics Inside” to

      76 Women in Engineering Women in IEEE PELS Katherine A. Kim, Yunting Liu, Stephanie Watts Butler, Sneha Narasimhan, Kristen Parrish, Mhret Berhe Gebremariam, and Christina DiMarino

Harish Sarma Krishnamoorthy, Philip Krein, and Brian Zahnstecher

      84 Students and Young Professionals Rendezvous  PELS Day 2023 Looks Back to Support Local Chapters John Noon and Joseph P. Kozak  The S&YP Spotlight Program Haifah Sambo, Bruna Seibel Gehrke, Ripun Phukan, Anshuman Sharma, Nayara Brandão de Freitas, and Joseph P. Kozak

“Human-Centered Power Electronics”

On the cover The focus of this issue is High-Frequency Passives. BACKGROUND—©SHUTTERSTOCK.COM/SAKKMESTERKE, FIGURE1— ©SHUTTERSTOCK.COM/SERGEI KORNILEV, FIGURE 3— ©SHUTTERSTOCK.COM/KARAKEDI35

      88 Society News   100 Event Calendar   104 White Hot More Stuff to Know Robert V. White Digital Object Identifier 10.1109/MPEL.2023.3305177



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IEEE Power Electronics Magazine Editor-in-Chief Ashok Bindra Austin, TX, USA +1 631 672-2875 [email protected] Deputy Editors-in-Chief Stephanie Watts Butler (Industry) WattsButler LLC USA [email protected] Leon M. Tolbert (Academic) Min H. Kao Professor Electrical Engineering and Computer Science The University of Tennessee 520 Min H. Kao Bldg Knoxville, TN, 37996-2250, USA +1 865 974-2881 [email protected] Magazine Advisory Board Leon M. Tolbert MAB Cochair Chairman The University of Tennessee, TN, USA Stephanie Watts Butler MAB Cochair WattsButler LLC USA Robert N Guenther, Jr GPEM LLC Marysville, Ohio, USA Jennifer Vining University of Washington Seattle, WA, USA Annette Mutze Graz University of Technology, Graz, Austria Soma Essakiappan University of North CarolinaCharlotte, NC, USA Tony O’Gorman PESC Inc. San Diego, CA, USA Yingying Kuai Caterpillar Inc. Mossville, IL, USA Alpha J. Zhang Delta Electronics Shanghai, China IEEE Power Electronics Society Officers Brad Lehman President [email protected] Liuchen Chang Immediate Past President Nominations Committee Chair [email protected]

Frede Blaabjerg Senior Past President Long Range Planning Committee Chair [email protected] Mario Pacas VP Global Relations [email protected] Pat Wheeler VP Technical Operations [email protected] Yunwei (Ryan) Li VP Products [email protected] Johan Enslin VP Industry and Standards [email protected] Jian Sun VP Conferences [email protected] Mark Dehong Xu VP Membership [email protected] Pradeep Shenoy Treasurer [email protected] Katherine Kim Constitution and Bylaws [email protected] Kevin L. Peterson Division II Director 2023 Members-at-Large Noriko Kawakami Toshiba Mitsubishi-Electric Industrial Systems Corp., Japan Yan-Fei Liu Queen’s University, Canada Yunwei (Ryan) Li University of Alberta, Canada Pedro Rodriguez University Loyola Andalusia, Spain Jennifer Vining University of Washington, USA Navid R. Zargari Rockwell Automation, Canada 2024 Members-at-Large Stephanie Watts Butler WattsButler LLC USA Shinzo Tamai Toshiba Mitsubishi-Electric Industrial Systems Corp., Japan Ulrike Grossner ETH Zurich, Switzerland Giovanna Oriti Naval Postgraduate School, USA Axel Mertens Leibniz Universität Hannover, Germany

Maryam Saeedifard Georgia Tech, USA 2025 Members-at-Large Vivek Agarwal Indian Institute of Technology Bombay, India Mahshid Amirabadi Northeastern, USA Christina DiMarino Virginia Tech, USA Philip Carne Kjaer Vestas, Denmark Hong Li Beijing Jiaotong University, China Sudip K. Mazumder University of Illinois Chicago, USA Technical Committee Chairs Luca Corradini TC 1: Control and Modeling of Power Electronics Christina DiMarino TC 2: Power Components, Integration, and Power ICs [email protected] Ali Bazzi TC 3: Electrical Machines, Drives and Automation [email protected] Mahesh Krishnamurthy TC 4: Electrical Transportation Systems [email protected] Juan Balda TC 5: Sustainable Energy Systems [email protected] Khurram Khan Afridi TC 6: Emerging Power ElectronicTechnologies [email protected] Alexis Kwasinski TC 7: Critical Power and Energy Storage Systems [email protected] Marco Liserre TC 8: Electric Power Grid Systems [email protected] Grant Covic TC 9: Wireless Power Transfer Systems [email protected] Kevin Hermanns TC 10: Design Methodologies [email protected] Tao Yang TC 11: Aerospace Power Sanjib Kumar Panda TC 12: Energy Access and Off-Grid Systems [email protected]

Advertising Sales Kathy Naraghi WelComm, Inc., [email protected] +1 858 279-2100 IEEE Power Electronics Society Staff Mike Kelly Executive Director [email protected] Jane Celusak Project Manager [email protected] Becky Boresen Technical Community Program Specialist [email protected] Megan Cichocki Program Specialist [email protected] Mary Beth Schwartz Publications Administrator [email protected] Jessica Uherek Editorial Assistant/News Editor [email protected] Brianna Fornaro Senior Society Administrator [email protected] Elizabeth Mahon Senior Administrator Conferences/Meeting Services [email protected] IEEE Publishing Operations 445 Hoes Lane, Piscataway, NJ 08854 USA Brian Johnson Journals Production Manager Katie Sullivan Senior Manager, Journals Production Janet Dudar Senior Art Director Gail A. Schnitzer Associate Art Director Theresa L. Smith Production Coordinator Mark David Sr. Manager Advertising and Business Development Felicia Spagnoli Manager, Advertising Production Peter M. Tuohy Director, Production Services Kevin Lisankie Director, Editorial Services Dawn M. Melley Senior Director, Publishing Operations

IEEE prohibits discrimination, harassment, and bullying. For more information, visit http://www.ieee.org/nondiscrimination. IEEE Power Electronics Magazine (ISSN 2329-9207) (IPEMDG) is published quarterly by the Institute of Electrical and Electronics Engineers, Inc. Headquarters: 3 Park Avenue, 17th Floor, New York, NY 10016-5997 USA, Telephone: +1 212 419 7900. Responsibility for the content rests upon the authors and not upon the IEEE, the Society or its members. IEEE Service Center (for orders, subscriptions, address changes): 445 Hoes Lane, Piscataway, NJ 08855-1331 USA. Telephone: +1 732 981 0060. Individual copies: IEEE members US$20.00 (first copy only), nonmembers US$109 per copy. Subscription rates: Annual subscription rates included in IEEE Power Electronics Society member dues. Subscription rates available on request. Copyright and reprint permission: Abstracting is permitted with credit to the source. Libraries are permitted to photocopy beyond the limits of U.S. Copyright law for the private use of patrons 1) those post-1977 articles that carry a code at the bottom of the first page, provided the per-copy fee indicated in the code is paid through the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923 USA; 2) pre-1978 articles without a fee. For other copying, reprint, or republication permission, write Copyrights and Permissions Department, IEEE Service Center, 445 Hoes Lane, Piscataway, NJ 08854. Copyright © 2023 by the Institute of Electrical and Electronics Engineers Inc. All rights reserved. Canadian GST #125634188 PRINTED IN THE U.S.A. Digital Object Identifier 10.1109/MPEL.2023.3305179

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MISSION STATEMENT: To educate, inform, and entertain our community of IEEE Power Electronics Society members on technology, events, industry news, and general topics relating to all electronic power conversions in any application or market and to further serve and support our Members in professional career development through delivering educational content and raising awareness of engineering tools and technologies.

From the Editor

by Ashok Bindra

New Developments in High-Frequency Passives

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n last ten years or so, wide bandgap (WBG) semiconductors have made significant progress that has resulted in rapid miniaturization with improved efficiency of power converters. Concurrently, the improvements in passive components, especially magnetics, such as inductors and transformers, have not kept pace with these advancements. While advances in WBG devices have certainly improved circuit efficiency and power density, the bottleneck now lies with magnetic components, with magnetics accounting for more than 30% of the cost and more than 30% of the loss in almost all power converters, according to experts. Magnetics design has become a critical issue for power electronics as trends towards high efficiency and high power-density continues. In the first cover feature article “Unveiling the Microworld inside Mag net ic Mater ia ls v ia Ci rcu it Models” by Han (Helen) Cui, Saurav Dulal, Sadia Binte Sohid, Gong Gu, and Leon M. Tolbert, the authors overcome the limits set by bulky and lossy magnetic components by proposing 1) radically new magnetic desig n tech n iques a nd 2) novel ma g net ic mater ia l s w it h i mpr ove d pr o p er t ie s , s uc h a s

Digital Object Identifier 10.1109/MPEL.2023.3303831 Date of publication: 26 September 2023

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higher saturation limit, higher permeability, and lower core loss. In this article, the authors address the challenges by investigating new magnetic material modeling capable of predicting component behavior. The article discusses a circuit model derived from the equation of motion for magnetic domains that concisely represents and illustrates material dynamic physics. The objective is to provide a new layer of foundation to ex pla in the non linea r complex behaviors in magnetic core losses and permeabilities. I n t he second cover a r t icle “Recent Advances in Capacitors Used in Wide Bandgap Power Circuitry” by Ron Demcko, the author presents new developments in passive components that are optimized to improve overall circuit performance in systems equipped with WBG semiconductors. Two of the most prolific such passive components are power film capacitors and ceramic capacitors. The article shows that improvements in electrode metallization of power film capacitors are attractive solutions for WBG applications for a variety of reasons. The third cover article “Addressing Power Decoupling in High-Performance, High-Frequency Applications Using E-CAP” by Mukund Krishna and Luca Vassalli shows that silicon capacitors are a better choice for decoupling as compared to conventional MLCCs.

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As battery electric vehicles (BEVs) are becoming more popular, so is research and development on inductive charging of these batteries. The fourth feature “Wireless Inductive Charging of Battery Electric Vehicles Is Coming” by Darko Vracˇ ar, Sebastian Wüstner, and Alkiviadis Boulos demonstrates the development of inductive charging system for a BEV manufactured by a well-known German car OEM. The next feature “A Survey on Impedance-Based Dynamics Analysi s Met hod for I nver ter-Ba sed Resources” by Heng Wu, Fangzhou Zhao, and Xiongfei Wang, the authors present the results of a survey conducted by an IEEE PELS/PES Task Force on Frequency-Domain Modeling and Dynamic Analysis of HighVoltage Direct Current and Flexible AC Transmission System, including questionnaires and responses from different stakeholders. While the results of the survey on impedancebased dynamics analysis method have identified gaps and challenges faced by different stakeholders, several emerging topics in this direction have also been summarized by the researchers. Going forward, the IEEE Task Force intends to organize more technical activities to facilitate collaborations between academia and industry in addressing these challenges. In the sixth feature “Future Directions of Commercially Available

Supercapacitors” by Nadee Arawwawala, Nihal Kularatna, and Don Charles Uvindra Sirimanne, the authors show that the current progress of the newer commercial supercapacitor families, such as hybrid types, are gradually moving towards the properties of high energy Li-ion battery chemistries, but without seriously compromising the cycle life. The researchers are looking forward to interesting developments in the next five years. Finally, the last feature “From ‘Power Electronics Inside’ to ‘HumanCentered Power Electronics’” by Harish S. Krishnamoorthy, Philip Krein, and Brian Zahnstecher, an IEEE FEPPCON XI presentation, investigates the human impact of power electronics.

News, Columns, and More In the column President’s Message, Brad Lehman discloses PELS remarkable progress in implementing diverse activities and initiatives that are shaping the dynamic landscape of

our society. Likewise, in the PSMA Corner, Renee Yawger focuses on the tenth anniversary of the workshop on wide bandgap power devices and applications (WiPDA). While in the Expert View, Alex Lidow examines factors impacting gallium nitride (GaN) adoption, and how they are being addressed and overcome in the industry. He concludes that barriers to mass adoption of GaN power devices are rapidly falling and early adopters will have a distinct advantage over their competitors. The Women in Engineering column by Katherine A. Kim, Yunting Liu, Stephanie Watts Butler, Sneha Narasimhan, Kristen Parrish, Mhret Berhe Gebremariam, and Christina DiMarino presents the progress women have made in IEEE PELS in last ten years or so. In the Industry Pulse, written by Kristen Parrish and Stephanie Watts Butler, the authors investigate consumer EV standards and voltage trends, and how they are impacti ng W BG sem iconductor needs in the market.

Similarly, in the White Hot column, Bob White explores hardware and software skills that power electronics engineers must acquire over the years to be successful in the industr y. “To be successful learn something new every day,” says White. Meanwhile, the “Students and Young Professionals Rendezvous” column highlights PELS Day celebrations around Chapters in all regions of the world. Plus, the same column reveals the S&YP spotlight program that shines light on PELS’ rising stars. A s u sua l, t he Societ y News brings activities from PELS chapters and student branches around the world, and the “Event Calendar” provides a year’s listing of conferences and workshops. Thank you for supporting the PELS magazine for the last ten years. Advertisers are coming back. And our commitment to bringing timely articles, columns and news of interest and value to practicing power electronics engineers worldwide is getting stronger year over ye a r. To s e r ve you better a nd keep this maga zine a va luable resource for working power electronics engineers around the world, we look for wa rd t o your feedback and suggestions. Now, we have a w e b s i t e ( h t t p s : // pelsmagazine.ieee.org/) which offers more than what is in the print, and where you can easily provide your feedback. Stay safe and healthy!



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President’s Message

by Brad Lehman

Advancing Power Electronics Innovation and Industry Engagement

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he IEEE Power Electronics Society (PELS) has been actively engaged in initiatives to support the careers of industry-oriented PELS members, while also creating opportunities for those more inclined towards research. PELS has made remarkable progress in implementing diverse activities and initiatives that are shaping the dynamic landscape of our society.

Activities of PELS Industry and Standards Under the leadership of Johan Enslin, our vice president of Industry and Standards, PELS has undergone a transformative program change to better serve our industry members and actively contribute to the development of standards. The newly formed Industry Standing Committee (IC), along with the existing Standards Committee (PELSC), now falls under the Industry and Standards Portfolio. To accelerate standards innovation and engage our Technical Committees (TCs) to help achieve our 2020 Strategic Plan. The goal is to promote the creation, development, standardization, and application of power electronics tech nologies while disseminating knowledge to our members, the professionals, and the public. Digital Object Identifier 10.1109/MPEL.2023.3299937 Date of publication: 26 September 2023

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By integrating standards, roadmaps, and program activities, PELS aims to engage more industry participants and fortify the mission of fostering power electronics technological innovation and excellence for the benefit of humanity. Thanks to the dedication of our active volunteers, the past year led to some notable achievements: ■■Restructuring Industry and Standards to integrate industry initiatives, roadmaps, and standards under a unified portfolio. ■■Achieving representation from all TCs on the Industry and Standards Portfolio. ■■Providing web-based tutorials and training in collaboration with IEEE SA to support our members in standards development. ■■Commencing the formation of a new PELS Roadmap on utility applications of medium and high voltage grids. ■■Finalizing several new initiatives in collaboration with SCC-21, including a white paper on grid forming converters, with a summary published in the PELS Power Electronics Magazine, June 2023. ■■Concluding the work of the Study Committee for the new IEEE-1547 and initiating a new Study Committee for IEEE-2030—Smart Grid updates. ■■Publication of IEEE-2800 Transmission Converters Standards. ■■Publishing various standard

IEEE POWER ELECTRONICS MAGAZINE z September 2023

updates, such as P389, P2996, and IEC-61007-P389, along with several ongoing projects. ■■Active engagement in the ITRW and ITRD roadmaps with working group activities. All these activities are now coordinated through the PELS Industry and Standards Committee (PELSC) and Industry Committee (IC). Their meetings, which takes place three times a year around PELS main conferences like IEEE APEC and ECCE, offer valuable oppor tunities for engagement. PELS encourages all members to actively participate in these activities and embrace the new Industry and Standards initiatives.

Activities in PELS TCs Under the guidance of Prof. Pat Wheeler, our vice president for technical operations, the PELS Technical Operations Committee plays a crucial role in overseeing the dynamic activities of our 12 TCs. The TCs offer exceptional opportunities for our members to connect with likeminded colleagues from around the globe, offering: ■■Regular Technical Webinars: PELS is actively planning to increase the number of webinars to four per technical committee each year. ■■Conferences and Workshops: Each TC organizes at least one flagship workshop or conference annually, with many committees hosting multiple events. 2329-9207/23/$31.00©2023IEEE

Several TCs arrange international competitions, such as the recently launched MagNet Challenge. ■■Technical Awards: To recognize the contributions of our members, we have a range of awards associated with the TCs, acknowledging their outstanding achievements. ■■Competitions:

■■Mentorship

and Routes to Becoming Fellow of the IEEE: TCs support career development and provide guidance on the path to becoming an IEEE Fellow (FIEEE). ■■Events and Meetings at Conferences: Look out for TC meetings at PELS conferences, including ECCE in North America and

APEC, as well as many other PELS sponsored flagship conferences. There are often student travel grants provided. ■■Online Meetings and Networking: Many committees hold online meetings and maintain active social media channels, fostering interaction and knowledge exchange. If you are interested in becoming more involved in the IEEE PELS TCs, I encourage you to sign up for membership and reach out to the respective TC chair. You can find the links and contact details on the TC website.

Activities in our Products Portfolio IEEE Open Journal of Power E l e c t r o n i c s (OJPEL) has achieved its first Journal Impact Factor of 5.8, as recognized by Clarivate. Launched in 2020, OJPEL is a 100% open access journal that publishes high-quality, peer-reviewed papers, covering the development and application of power electronic systems and technologies. The review time is blazingly fast, and usually less than 1 month! Additionally, the following IEEE publications have achieved impressive Journal Impact Factors: ■    IEEE Journal of Emerging a n d S e l e c t e d To p i c s in  Power Electronics (JESTPE): 5.5 ■    I EEE Power Electronics Magazine (MPEL): 2.3 ■    IEEE Transactions on Power Electronics (TPEL): 6.7 ■    I EEE Transactions on Transportation Electrification (TTE): 7 These high impact factors reflect the exceptional quality of our publications and their inf luence within the power electronics community. More impressive is IEEE Transactions on Power Electronics remains the most downloaded

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IEEE Transactions in all of IEEE, demonstrating its enduring popularity among PELS industry-focused members. This is a testament to the immense value it provides to the community. Moreover, PELS is actively working to provide opportunities for industry authors in our publications, such as the recently featured Letters Special Section on Patent-Related Short Articles in the June 2023 issue of TPEL. Additionally, OJPEL invites industry and application-oriented results, incor porating a special review criterion suitable for insightful designs and application topics in power electronics. It is also time to congratulate the 2022 TPEL Prize Paper Award recipients, as well as the winners of the TTE Prize Paper Awards and JESTPE Prize Paper Awards. I encourage everyone to visit our awards website for more infor mation on these esteemed accolades.

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PELS Awards One of the highlights of any presidential message is to congratulate all the PELS award winners in our society, recognizing several exceptional individuals with society-level awards. Please visit our Awards 2023 website for more information on the PELS 2023 Awards. The highest level PELS award within our society is the technical field award: the IEEE William E. Newell Power Electronics Award, which for 2024 has been awarded to Prof. David J. Perreault from MIT. Prof. Perreault’s groundbreaking work on very-high-frequency power converters has made a significant impact on our field. His contributions in modeling, design, and control of dc–dc converters operating at frequencies in the 100’s of megahertz have revolutionized power electronics. I encourage all readers t o del ve i nt o h i s V H F p ower

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converter research, as it represents a pivotal milestone in our understanding of this domain. (Notice his visionary papers were as early as 2008, at a time when most (of us) power electronics engineers were struggling with making our Si MOSFETs work in our dc–dc converters when switching at 250 kHz!)

Conclusion As we look to the future, PELS will continue to evolve and adapt to the changing landscape of our industry. By engaging industry professionals, promoting inclusivity, and driving standards development, we aim to position PELS as a leading force in power electronics. Together, we can shape the future of power electronics and create a positive impact on humanity. Contact me if you want to volunteer in any of these efforts! Brad Lehman; [email protected] 

©SHUTTERSTOCK.COM/GARRYKILLIAN

Unveiling the Microworld Inside Magnetic Materials via Circuit Models by Han (Helen) Cui, Saurav Dulal, Sadia Binte Sohid, Gong Gu, and Leon M. Tolbert

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 he progress made in wide bandgap (WBG) semiconductors has resulted in rapid miniaturization and increased efficiency of power converters. However, the improvements in magnetic components, such as inductors and transformers, have not kept pace with these advancements [1], [2], [3]. Although advances in WBG devices, novel

Digital Object Identifier 10.1109/MPEL.2023.3301408 Date of publication: 26 September 2023

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2329-9207/23©2023IEEE

topologies, control schemes, and hardware fabrications have greatly improved circuit efficiency and power density, the bottleneck now lies with magnetic components [4], with magnetics accounting for more than 30% of the cost and more than 30% of the loss in almost all power converters [5]. Magnetics design has become a critical issue for power electronics as trends towards high efficiency and high power-density. The limits set by bulky and lossy magnetic components must be broken by 1) radically new magnetic design techniques and 2) novel magnetic materials with improved properties (e.g., higher saturation limit, higher permeability, and lower core loss).

Why is it Difficult to Deal With Magnetics? The challenges of magnetics design and optimization are attributed to two main aspects, both of which must be addressed by magnetic material modeling capable of predicting component behaviors: First, deep understanding and accurate design tools are required in magnetic components to comply with the trend towards high frequency and high density. Instead of being satisfied with the performance given by an off-theshelf inductor, power electronics engineers nowadays are obliged to design magnetic components from scratch with highly customized cores and windings that yield better performance. This requires advanced knowledge of magnetic materials, loss analysis, high-frequency effects, and simulations that aid the design. Advanced electromagnetic simulators [6], such as 3D finite-element analysis (FEA) tools, are able to simulate linear performance factors governed by the Maxwell’s equations, including winding loss, fringing effect, geometry-based non-uniformity, and even numerical optimizations. However, there is one exception, and it is the major one that causes the discrepancies seen frequently between simulations and real prototypes: the nonlinear magnetic materials. Lack of accurate models and understanding of the material’s properties (such as dc bias- and frequency-dependent loss and permeability) when used as a power electronics component results in oversimplified

assumptions in magnetic design and then iterations of magnetics prototyping based on trial and error. Second, new magnetic materials are needed to break the ceiling of magnetic component performance set by intrinsic physical properties (e.g., saturation level, permeability, and loss density) of existing materials. To this end, component or even system level insights are essential to guide new materials development. However, magnetic components design is not a single-objective optimization process [7]; an optimal design balances several performance factors. For example, a material that has an infinitely large permeability, but low saturation level, doesn’t necessarily lead to improved component performance. An envisioned paradigm of material-component-system co-design needs to be facilitated by a simulation platform that links magnetic material properties component prototype performance metrics. However, magnetic materials modeling is never an easy job. The two most concerned performances of magnetic materials in power electronics applications are permeability and core loss, both of which vary significantly with frequency and the strength of the magnetic field (excitation signal) applied. Take the MnZn ferrite material N87 from TDK [8] as an example (Figure 1). The nonlinear permeability and core loss vary with frequency and ac excitation amplitude. Besides the nonlinearity with ac excitation, the effect of dc bias on the permeability and loss also strongly impacts the core performance [9]. Such complexities, rooted in the nonlinear dynamics of magnetic materials, hinder good agreement between designs and prototypes of magnetic components and lead to multiple trial and error in engineering practice. In practice, power electronics engineers tend to use empirical approaches to characterize magnetic materials based on large-signal measurements. Models to account for the core loss and permeability, mostly empirical, are extracted by curve-fitting experimental results measured from specific prototypes [10], [11], with measurements getting more extensive as more complex behaviors of the core are observed. Even the physics-based models

FIG 1 Nonlinear behaviors of magnetic material N87: (a) permeability versus frequency, (b) permeability versus ac excitation amplitude, (c) core loss density versus frequency and ac excitation amplitude [7], and (d) core loss versus dc bias [8].



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do not capture the nonlinear dynamics properly, as none of the model accounts for all aspects of the complicated physics. Prominent examples include the Jiles–Atherton (J–A) [12] and Preisach models [13]: The former attributes magnetic hysteresis to a single frictional mechanism— domain wall movement impeded by defect pinning, and the latter is based on the Stoner–Wohlfarth theory that concerns only the energy minimization with no regards by itself to the dynamics of the material system. Nowadays, assisted by powerful artificial intelligence (AI) tools, researchers are able to conduct large-scale measurements and model extractions to get more accurate performance predictions [14], [15]. However, the biggest issue with AI models is that they are only as good as the data they are trained on and provide no insights on how they arrived at their results. More desirable for the next-generation power electronics is a bottom-up solution (Figure 2), based on the physics underlying the behavior of magnetic materials in components, thus allowing for component behavior prediction in a wide range of operating conditions to enable design optimization. Moreover, physics-based magnetics modeling on the material level bridges the gap between the material science and power electronics communities by providing a common platform, on which the problems related to magnetization and loss mechanisms can be better framed, thus fostering innovations in magnetic materials research for power electronics. Nevertheless, the computational cost of physics-based magnetic material modeling can be prohibitively high, therefore trade-offs must be made at the onset. Fortunately, a mesoscopic view [16] provides appropriate trade-offs that enable, in principle, predictive

modeling at reasonable cost: while the atomic-scale origin of ferromagnetism, the exchange interaction between electron magnetic moments, is quantum in nature without a classical analog, a magnet is treated as a mesoscopic continuous medium described by magnetization M(r) as a continuously varying function of location r. The mesoscopically continuous medium is discretized into regions each described by local magnetization M, following timedomain differential equations describing their dynamics and coupling with neighboring regions. Such a region is sufficiently large on the atomic scale for quantum effects to average out, thus the differential equation is a classical, albeit nonlinear, one. The course graining and the relatively simple classical equation at the bottom level will enable this approach to capture the nonlinear dynamics at adequate accuracies at practically acceptable computational costs. This article describes a novel implementation of such a bottom-up solution. The nonlinear differential equation of a discretized region is mapped to a mathematically equivalent circuit model such that the collective dynamic response of the coupled regions to external field excitations is emulated by that of the coupled unit circuits to circuit excitations. Thus, the simulations will be performed using circuit simulators that power electronic engineers are already familiar with. Preliminary results are reported on some simplified cases to show the potential of such models in describing the nonlinear B–H hysteresis and loss behaviors. Use cases are presented to demonstrate the capability of the model for magnetics used in both power electronics and microwave applications. The model will be augmented and scaled up to include more physical mechanisms.

FIG 2 In contrast to the conventional “top-down” solution for magnetics modeling, we propose to develop a novel “bottom-up” solution.

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Physics Based Circuit Models for Magnetic Materials Every performance metric of a magnetic component originates from the response of its core material to external field excitations; the core is a soft magnet. Ferromagnetism originates from the magnetic moment of the electron spin. Strong but short-range exchange interaction aligns the electron spins within a distance in the order of 10 nm, but longrange interactions favor a random distribution of magnetization, which is the total magnetic moment per volume. The balance results in the formation of magnetic domains, each a region of uniform magnetization (Figure 3). The dynamics of a magnetic material boils down to the time evolution of the domains, which is described by the Landau–Lifshitz–Gilbert (LLG) equation.

LLG Equation The LLG equation [16] describes the dynamics of magnetization M, presumed uniform throughout a magnetic material sample or a region therein:

α dM dM = − µ0γ M × Heff + M× (1) Ms dt dt

saturation magnetization; both parameters are to be obtained from standard material characterization. Lastly, γ is slightly modified from the isolated electron value to account for atomic structures of specific materials. Equation (1) is written as three coupled differential equations in three Cartesian projections. Examining these equations, we see that they are formally the same as the set of equations describing a circuit of coupled elements: Each of the three equations, written in a form with all terms on one side and zero on the other, resembles Kirchoff’s current law (KCL) upon mapping M i , i = x , y, z, to linkages Λ i of three coupled inductors Li , and H z to excitation current I z ; Li are considered wound around a shared core just share the same flux. The mapping leads us to an equivalent circuit model shown in Figure 4 (more details below), where the three ports correspond to the three Cartesian projections, with the voltages Vi = dΛ i / dt  surrogating dM i / dt. To illustrate our bottom-up modeling framework, let us start with a fictitious single-domain inductor core ∆z long with a ∆x × ∆y rectangular cross section. Assuming an isotropic core material and neglecting the demagnetizing field for now, we have Heff = H = H z zˆ , where H z = I z / ∆z is due to the only excitation—current through the inductor

where the vacuum permeability μ0 is a physical constant. Here, we emphasize that Heff = H + He is the total effective field including the magnetic field H and the effective field He , which is the sum of effective fields that represent the material anisotropy, exchange interaction, etc. Without the second term on the right side, (1) is in the same form as the dynamics of an isolated electron magnetic moment dm / dt = − µ0γ m × H , where there is no distinction between Heff and H, and γ = 1.759 × 1011 C/kg is the electron charge-to-mass ratio, which is identical to the ratio of the moment to spin angular momentum, named the gyromagnetic ratio. This equation simply describes the precession of the electron spin angular momentum and, proportionally, m, driven by the torque exerted by Heff . The isolated electron spin precesses indefinitely because FIG 3 Illustration of magnetic domains of a soft magnetic the torque is always perpendicular to m. Since ferromagnematerial lining up when exposed to an external magnetic field. tism arises from electron spins, we can replace m with M, i.e., the sum of magnetic moments of all N electrons contributing to ferromagnetism in a unit volume of a material. Due to other effects in the material, however, the precession is damped, and therefore M gradually aligns w i t h Heff i n w h a t i s referred to as the magnetization process. To describe this lossy process, the second term is phenomenologically introduced to (1), where α is FIG 4 Equivalent circuit with parameters derived from the full LLG equation describing a magthe damping parameter netic domain’s movement in 3D x–y–z planes with external excitation field applied on the and M s = Nm = M is the z direction.

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winding (per Ampere’s law). Proportional constants in the above mapping of dM i / dt and H z to surrogate voltages Vi and currents I z can be chosen arbitrarily. Interestingly, by choosing mapping proportions such that H z → I z = H z ∆z and dM z / dt → Vz = µ0 ∆x ∆y ( dM z / dt ) , the current I z and voltage Vz in the equivalent circuit coincide with the current and the voltage per turn of the physical inductor (approximately for voltage given relative permeability µ r  1), allowing for direct integration of material modeling into a circuit simulator to simulate a physical circuit. The mapping of quantities in all three dimensions to the surrogate circuit quantities is as follows: dM y dM x Vx = µ0 ∆y∆z , Vy = µ0 ∆x ∆z , dt dt (2) dM z Vz = µ0 ∆y∆x , I z = H z ⋅ ∆z. dt



Substituting the circuit surrogates defined by (2) into the three differential equations re-written from (1) and then eliminating dM z / dt using the z-projection equation, the two remaining equations for x and y projections become: 0=

Vx 2 µ0 γ M z ∆z +

0=− +

+

∆yH z ⋅ ∫ Vy dt

µ0 ∆x ∆zM z

α M x M y ⋅ Vx µ02γ M s M z2 ∆z Vy 2 µ0 γ M z ∆z

+

+

+

α∆y ⋅ Vy 2 µ0 γ M s ∆x ∆z

α M y2 ∆y ⋅ Vy

(3)

µ02γ M s M z2∆x ∆z

∆xH z ⋅ ∫ Vx dt µ0 ∆y∆zM z

α∆x ⋅ Vx µ02γ M s ∆y∆z

+

α M x M y ⋅ Vy µ02γ M s M z2 ∆z

+

α M x2 ∆x ⋅ Vx µ02γ M s M z2 ∆y∆z

(4) .

Equivalent Circuit for LLG Equation Equations (3) and (4) are actually KCL equations at ports x and y of the three-port circuit when the excitation is applied only to port z. The total currents at ports x and y each consist of five components that add up to zero, expressed as follows in terms of the equivalent circuit elements labeled in Figure 4:

0=



0=−

Vy Vx ∫ Vy dt Vy V + + + x + (5) Zg Ly Ry1 Zm Ry 2 Vy Zg

+

Vy ∫ Vx dt Vx V + + + x . (6) Lx Rx1 Z m Rx 2

The inductors Lx and Ly with coupling to the z port is thus determined to be

Ly =

µ0 ∆x ∆zM z , ∆yH z

Lx =

µ0 ∆y∆zM z , (7) ∆xH z

along with additional elements: Rx1 and Ry1 are linear resistors, while Rx2 and Ry2 are nonlinear resistors across port x and y, respectively, given by

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Rx1 = Rx 2 =

µ02γ M s ∆y∆z µ 2γ M s ∆x ∆z , Ry1 = 0 , α∆x α∆y µ02γ M s M z2∆y∆z α M x2 ∆x

, Ry 2 =

µ02γ M s M z2∆x ∆z α M y2∆y

(8) ;

a gyrator with impedance Z g and a 1:1 transformer with all equal self and mutual impedances Zm couple ports x and y:

Z g = µ02γ M z ∆z,

Zm =

µ02γ M s M z2 ∆z . (9) α M x My

Notice that definitions of Vz and I z in (2) directly result in Lz = dΛ z / dt = ( µ0 ∆x ∆yM z ) / ( ∆xH z ) , which, along with (7), indicate that the three coupled inductor share the same flux φ that can be mapped to M z .

Modeling Results The equivalent circuit in Figure 4 can be constructed in any circuit simulator that allows user-defined terminal functions. The circuit requires one input at one port (z in the example) representing the winding current, the dimension of the single-domain core (i.e., Δx, Δy, and Δz), and two material properties α and Ms, both of which can be experimentally determined by measuring the frequency-dependent magnetic susceptibility of the material. The outputs of the model are the voltages and currents on each of the three terminals (Vx, Vy, Vz, Ix, Iy, Iz), which correspond to the magnetization and magnetic field along each direction as suggested by (2). By varying the excitation signal applied to the input side, the output can be measured in voltage and examined dynamically in time-domain that reflects what happens inside the microworld of the magnetic material. This serves as a valuable tool to transparently connect the material’s properties to its function and performance in a power electronics system in the language of circuits.

Nonlinear Magnetization Process As a preliminary test run of the model, a fictitious single domain with a size of 200 μm × 50 μm × 38 mm, damping constant of 5 × 10−4, and magnetization of 1750 Oe was used. An external dc magnetic field was applied to the domain in terms of a current source. The magnitude of the dc field was increased from 0 to 100 Oe in the z direction, and the domain was assumed to be aligned originally along the x direction by defining the initial conditions of the voltages on the three terminals. The magnetization process happens when the domain starts to rotate and gets aligned with the external field and eventually gets saturated, which can all be observed vividly from the waveforms of Mx, My, and Mz translated from the Vx, Vy, and Vz. As shown in Figure 5, this process is plotted in 3D showing the trajectory of the domain magnetization process from the initial state of alignment with x (Mx = 1750 Oe) that then slowly spirals to the final state of saturation along the z direction (Mz = 1750 Oe).

FIG 5 Time lapse and trajectory of a magnetic domain rotation starting with aligned on the x direction and gradually rotates to the z direction on which the external field is applied.

The complete 3D modeling of the domain rotation, rather than 1D or 2D, preserves the full picture of how the domain moves, providing interconnecting capability to simulate 3D couplings with multiple domains. To further showcase the capability of the model, we show that a hysteresis loop can be simulated (results shown FIG 6 Simulation results from the circuit model of a magnetic domain under an external magnetic field H along the z direction showing (a) nonlinear permeability and flux density B versus external in Figure 6) by simply field H and (b) initial magnetization curve and hysteresis loop. introducing an anisotropy field Hani , and that which directly links a magnetic material parameter to nonlinear M–H curve and nonlinear permeability can power electronics component behavior. be readily extracted from simulation results. A conThe LLG-based model has long been used in microwave stant anisotropy field is introduced by adding constant applications [16], and was more recently implemented with current sources to the ports to simulate magnetocrysˆ equivalent circuits. Compared to power electronics applitalline anisotropy that tilts the easy axis away from z. cations, microwave applications have a simpler scenario to As the external excitation field H z increases in time, address, where a strong dc field in one direction biases all M spirals towards the direction of Heff = H z zˆ + Hani domains near saturation thus the high-frequency field drivand thus Mz increases. The susceptibility is extracted ing M to precess at a small angle can be treated as a small by χ = M z / H z , and the relative permeability is simply signal. Therefore, the nonlinear resistors R x2 and Ry2 as µ r = 1 + χ , shown in Figure 6(a) as extracted along the curve as H z drops to zero after the saturation. As the well as the 1:1 transformer Zm in Figure 4 can be ignored. external field decreases and reverses, M moves away As an example, the frequency-selective limiter (FSL) is a from the zˆ direction as it precesses around the total waveguide loaded with a piece of magnetic material that effective field, giving rise to hysteresis. By reversing the utilizes the nonlinear insertion loss in magnetics to attenuexternal field twice, the full hysteresis loop is captured, ate input signals at different amplitudes [17]. The circuit as shown in Figure 6(b). These results demonstrate for model has been proven effective to predict the nonlinear the first time that the micro-dynamics in magnetic matelosses and time delays for the filtering performance as rials can be represented and simulated in circuit solvers, demonstrated in [17] and [18].

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Scaling up to Bulk Materials and Refining the Model The above examples showcase the potential of the proposed modeling framework, in simple cases where the core can be treated as having a uniform M. In the discussion of scaling up, we refer to a region of uniform M governed by (1) in a core material as a “domain,” which does not necessarily identify with a physical magnetic domain although conceptually similar. We first point out that a single-domain model can already simulate some special cases. A demagnetization field H d dependent on M can be added to simulate the shape anisotropy of a long, thin core made of a soft magnetic material, because the long-range interaction is embedded in the M dependence in H d . This can be implemented by utilizing ports x and y in Figure 4. At the relatively low frequencies of interest to power electronics (even for fastswitching converters enabled by future magnetic materials), the effect of initial M orientations is insignificant therefore the single-domain model is expected to achieve adequate accuracy. This model will work even better for a thin torus, with the cross section area and axial perimeter substituting ∆x ∆y and ∆z, respectively. Other core shapes can be simulated by using the appropriate H d versus M dependence in accordance with the demagnetizing tensors. Furthermore, a magnetocrystalline anisotropy field Hani can be added as exemplified above (Figure 6), with an orientation determined by the fabrication process. Worth pointing out is the flexibility afforded by the LLG equation in accommodating various physics through various effective fields. We mention in passing that H d , while acting similarly, is conceptually not an effective field, but rather a part of H, which is determined by the winding current per Ampere’s law. Multiple domains will be needed in general. For example, the easy and hard axes may be oriented in different directions with regard to the core geometry, requiring different Hani in different regions. In a multi-domain model, each domain n is represented by a three-port circuit simulating the dynamics of its magnetization Mn , and the susceptibility is extracted by χ = [ ∑ n ( zˆ ⋅ Mn ∆Vn ) / V ] / H z , where ∆Vn and V are the volume of domain n and the total volume, respectively. We expect the use of “domains” larger

than physical magnetic domains to lower the computational cost in most cases, as in a previous LLG-based model [19], where the (0.1 mm)3 discretized region is already much larger than typical physical domains while only a 16 × 16 × 8 array of such regions was modeled to represent a magnetic core orders of magnitude larger in volume. The on-going efforts of this work involve adding physical mechanisms for the model to be adequate in more and more application scenarios to predict core loss and nonlinear permeability with a small number of physically meaningful and measurable parameters, in contrast to the extensive curve fitting as currently practiced. Down the road, neighboring domain interactions will be incorporated as coupling circuit elements to account for domain wall motion under exchange interactions within a single-crystal material, a crystal grain of polycrystalline materials, or an amorphous material. Finally, the domain wall motion impeding effects of grain boundaries, as visualized in cartoon illustration (Figure 7c), as well as other defects, will be captured. This framework is versatile to accommodate various physical mechanisms through effective fields, thanks to the flexibility of the single-domain circuit (Figure 4): while the excitation is applied only to port z, ports x and y can be connected to current sources representing effective fields. Separately on the single-domain level, the stochastic process of thermal relaxation may need to be incorporated. Overall, the parameters of the circuit model will be physical properties that can be extracted from material characterizations such as saturation flux density, ferromagnetic resonance quality factor, etc. The loss and permeability of the magnetic core can be simulated and extracted as the real and imaginary parts of the input impedance seen by the excitation source in the circuit model. By fine-tuning the model parameters, the loss and permeability should match bulk material and component measurement results. This model calibration is fundamentally different from empirical curve fitting, in that our model parameters bear physical meanings. Therefore, the accuracy gained by model calibration will be transferrable to components based on the same material but of different geometries and under different operation conditions,

FIG 7 Illustration of the scale-up process from the circuit model of (a) single magnetic domain to (b) single-crystal materials and (c) polycrystal magnetic materials.

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the frequency- and amplitude-dependency in the magnetic material properties result naturally from the dynamics described by the LLG.

How Artifical Intelligence (AI) Can Help With Physics-Based Models? Physics-based models are powerful tools to predict and understand the root cause of magnetic material behaviors. However, they will reach a limit when practical issues such as material impurities or irregular microstructures are taken into account. This is the general issue with bottom-up solutions where scaling-up is the most challenging part. On the other hand, typical top-down solutions such as AI-based or machine-learning methods are being developed, typically with limited physical insights. Therefore, it would be ideal that AI and physics-based models could work together in a complementary manner to enhance the accuracy and efficiency of modeling magnetic materials. The following are two possible ways: 1) Data-Driven Modeling on Non-Ideal Physical Factors: AI algorithms can be trained on large datasets of experimental or simulated data. By analyzing the data, AI models can identify patterns and relationships that may be difficult to detect using traditional physics-based modeling techniques such as complex microstructures in the material. These data-driven models for equivalent microstructures can then be integrated with physicsbased models to assist the scaling-up and improve the predictive power. 2) Optimization and Design Process: AI algorithms can be used in conjunction with physics-based models to optimize the design of magnetics for specific applications. For example, AI models can be used to identify the optimal parameters for the circuit models that can enhance the entire performance of a power electronics

system, such as the optimal shape of a magnetic component or the optimal material’s structure. Overall, the integration of AI and physics-based models will help in developing more accurate, efficient, and comprehensive models for the complex behaviors in magnetic materials and facilitate the WBG applications. By leveraging the strengths of both approaches, the goal is to develop a physics-informed intelligent model that bridges the gap between material science and power electronics as illustrated in Figure 8. By integrating the two areas, systemlevel inputs on the component specification can be provided to guide the material development, while the physics-based model will facilitate the identification of new material and their properties predictions.

Conclusion Equivalent circuit modeling is expected to be an effective way to connect the material’s properties with their component behaviors in the power electronics systems. This article discusses a circuit model derived from the equation of motion for magnetic domains that concisely represents and illustrates material dynamic physics. The objective is to provide a new layer of foundation to explain the nonlinear complex behaviors in magnetic core losses and permeabilities. Single magnetic domain dynamics has been simulated, which serves as the basis for the hierarchical scaling that entails the incorporation of more physical mechanisms as couplings among the single-domain circuits. The circuit model can be integrated with system level simulations where the magnetic component is used, thereby providing a path penetrating the material properties and the circuit applications. As power electronics continue to advance, it becomes increasingly important to delve deeper into the underlying principles and behavior of these systems through fundamental research. By doing so, a more comprehensive

FIG 8 Equivalent circuit modeling scheme connecting material-level structure and component-level performance without need of trial-and-error prototype measurements; it also provides guidelines on material microstructure to expedite the material development and optimization process.



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understanding can be gained of the complexities involved and identify new avenues for innovation and advancement, enabling us to push the boundaries of what is possible and achieve new levels of performance and efficiency in power electronics.

Acknowledgment This work was supported by the Office of Naval Research under Grant Award N00014-22-1-2545 titled “A multiscale physic-based magnetics design framework for ship scale power electronics.”

About the Authors Han (Helen) Cui ([email protected]) received the B.S. degree in electrical engineering from Tianjin University, Tianjin, China, in 2011, and the M.S. and Ph.D. degrees in electrical engineering from Virginia Tech, Blacksburg, VA, USA, in 2013 and 2017, respectively. Upon graduation, she joined the Electrical and Computer Engineering Department, University of California, Los Angeles, CA, USA, as a Post-Doctoral Researcher to expand the knowledge of magnetics modeling for high-frequency RF applications. She has been an Assistant Professor with the University of Tennessee, Knoxville, TN, USA, since 2020. Her research interests include magnetic designs and integration for WBG device applications, advanced power electronics packaging, electromagnetic devices for sensing, and microscopic magnetics. Saurav Dulal received the bachelor’s degree in electrical engineering from Pulchowk Campus, Tribhuvan University, Nepal, in 2021. He is currently pursuing the Ph.D. degree with the Department of Electrical Engineering and Computer Science, The University of Tennessee, Knoxville, TN, USA. His research interests include magnetic modeling, modeling of power converters, and application of power electronics in electric vehicles. Sadia Binte Sohid received the B.S. degree in electrical and electronic engineering from the Rajshahi University of Engineering and Technology, Rajshahi, Bangladesh, in 2015, and the M.S. degree in electrical engineering from Bucknell University, Lewisburg, PA, USA, in 2019. She is currently pursuing the Ph.D. degree in electrical engineering with the University of Tennessee, Knoxville, TN, USA. Her research interests include power electronics and magnetic design. Gong Gu is a Professor of electrical engineering with the University of Tennessee, Knoxville, TN, USA. His research interests are in novel materials for electronic device applications. He received the Ph.D. degree from Princeton University, Princeton, NJ, USA, and the bachelor’s degree from Tsinghua University, Beijing, China. Leon M. Tolbert received the bachelor’s, M.S., and Ph.D. degrees in electrical engineering from the Georgia Institute of Technology, Atlanta, GA, USA. He is currently

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the Chancellor’s Professor and the Min H. Kao Professor with the Department of Electrical Engineering and Computer Science, The University of Tennessee, Knoxville, TN, USA. He is also an Adjunct Participant with Oak Ridge National Laboratory, where he previously worked from 1991 to 2020. His research interests include electric vehicles, application of wide bandgap semiconductors, and the utility application of power electronics for renewable energy and energy storage.

References

[1] J. M. Silveyra et al., “Soft magnetic materials for a sustainable and electrified world,” Science, vol. 362, no. 6413, Oct. 2018, Art. no. eaao0195. [2] F. C. Lee, Q. Li, and A. Nabih, “High frequency resonant converters: An overview on the magnetic design and control methods,” IEEE J. Emerg. Sel. Topics Power Electron., vol. 9, no. 1, pp. 11–23, Feb. 2021. [3] A. Hanson, “Opportunities in magnetic materials for high-frequency power conversion,” MRS Commun., vol. 12, no. 5, pp. 521–530, Aug. 2022. [4] P. Ohodnicki. Emergence of WBG Based Power Electronics and System Level Needs/Opportunities for Advances in Passives, Packaging, and Peripherals With Emphasis on HF Magnetics. Accessed: Aug. 2020. [Online]. Available: https://www.energy.gov/sites/prod/files/2016/06/ f32/06%20-%20OE%20ORNL%20Materials%20Innovation%20Workshop%20 -%20Ohodnicki%20-%20small.pdf [5] 2023 IEEE International MagNet Challenge, 2023 MagNet Challenge Handbook. Accessed: Mar. 2023. [Online]. Available: https://github.com/minjiechen/magnetchallenge/blob/main/docs/handbook.pdf [6] Ansys Maxwell User’s Manual V11. Accessed: Sep. 2017. [Online]. Available: http://ansoft-maxwell.narod.ru/en/CompleteMaxwell3D_V11.pdf [7] S. D. Sudhoff, Power Magnetic Devices: A Multi-Objective Design Approach. Hoboken, NJ, USA: Wiley, 2014. [8] TDK. (Feb. 2023). Ferrites and Accessories: SIFERRIT Material N87 Datasheet. [Online]. Available: https://www.tdk-electronics.tdk.com/downloa d/528882/990c299b916e9f3eb7e44ad563b7f0b9/pdf-n87.pdf [9] J. Muhlethaler et al., “Core losses under the DC bias condition based on Steinmetz parameters,” IEEE Trans. Power Electron., vol. 27, no. 2, pp. 953–963, Feb. 2012. [10] M. Mu et al., “New core loss measurement method for high-frequency magnetic materials,” IEEE Trans. Power Electron., vol. 29, no. 8, pp. 4374–4381, Aug. 2014. [11] J. Muhlethaler et al., “Improved core-loss calculation for magnetic components employed in power electronic systems,” IEEE Trans. Power Electron., vol. 27, no. 2, pp. 964–973, Feb. 2012. [12] D. C. Jiles and D. L. Atherton, “Theory of ferromagnetic hysteresis,” J. Magn. Magn. Mater., vol. 61, nos. 1–2, pp. 48–60, Sep. 1986. [13] I. D. Mayergoyz, “Dynamic Preisach models of hysteresis,” IEEE Trans. Magn., vol. 24, no. 6, pp. 2925–2927, Nov. 1988. [14] H. Li et al., “MagNet: A machine learning framework for magnetic core loss modeling,” in Proc. IEEE 21st Workshop Control Modeling Power Electron. (COMPEL), Nov. 2020, pp. 1–8. [15] T. Guillod, P. Papamanolis, and J. W. Kolar, “Artificial neural network (ANN) based fast and accurate inductor modeling and design,” IEEE Open J. Power Electron., vol. 1, pp. 284–299, 2020. [16] J. M. D. Coey, Magnetism and Magnetic Materials. Cambridge, U.K.: Cambridge Univ. Press, 2016. [17] H. Cui, Z. Yao, and Y. E. Wang, “Coupling electromagnetic waves to spin waves: A physics-based nonlinear circuit model for frequency-selective limiters,” IEEE Trans. Microw. Theory Techn., vol. 67, no. 8, pp. 3221–3229, Aug. 2019. [18] Q. Gao et al., “Demystify RF magnetics with linear and nonlinear equivalent circuit models,” IEEE Microw. Mag., vol. 23, no. 11, pp. 28–47, Nov. 2022. [19] H. Tanaka, K. Nakamura, and O. Ichinokura, “Calculation of iron loss in soft ferromagnetic materials using magnetic circuit model taking magnetic hysteresis into consideration,” J. Magn. Soc. Jpn., vol. 39, no. 2, pp. 65–70, 2015.



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Recent Advances in Capacitors Used in Wide Bandgap Power Circuitry by Ron Demcko

A

dvances in wide bandgap (WBG) semiconductor technologies and the active devices they enable, including power diodes and transistors, have directly contributed to recent improvements in power conversion efficiency, and given today’s power circuit and grid demands, these efficiency gains are more important than ever.

Digital Object Identifier 10.1109/MPEL.2023.3301379 Date of publication: 26 September 2023

2329-9207/23©2023IEEE

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WBG semiconductors can oper■         Are available in can and boardate at higher temperatures and mount styles and a wide range of Film capacitor across a wider range of operating case sizes, voltage and current ratmanufacturers have frequencies, which enables systemings, and capacitance values to suit level power density and operatto support broad application suitcontinued to drive ing performance improvements. ability. improved electrode Today’s designers can leverage WBG ■         Are smaller and lighter than comsemiconductors with higher power peting solutions, which can result metallization on ever ratings in smaller die sizes than comin decreased device inductance and thinner film peting technologies, and if similar improved high-frequency perforelectrical power ratings are the goal, mance. dielectrics. they can leverage WBG semiconduc■         Exhibit high dielectric strength and tors with dramatically smaller die high reliability. sizes than competing solutions. This ■         Offer improved volumetric efficiendownsizing not only allows designers to achieve significy and ease of use. cantly smaller and more economical active device form ■         Have high pulse ratings designed to maximize breakdown factors but also helps make green energy, distributed voltage. power generation, micro grids, and a whole host of other ■         Are available with extended operating temperature rangpower generation, distribution, and use scenarios more es spanning −40 °C to +110 °C, which effectively attractive and economically feasible. overcomes the biggest drawback of power film capacitor To support continued advances in WBG semiconductechnology. tors and the active devices they enable, both of which show little to no sign of slowing down, passive component Power Film Capacitor Advancements manufacturers have begun developing advanced product Film capacitor manufacturers have continued to drive solutions that are optimized to improve overall circuit improved electrode metallization on ever thinner film performance in systems equipped with WBG semiconducdielectrics. Today’s electrode-coated dielectrics have such tors. Two of the most prolific such passive components thin metallic electrode layers that if, any dielectric defects are power film capacitors and ceramic capacitors. present, the metallization will quickly evaporate and prePower film capacitors are attractive solutions for WBG cipitate onto the cool surrounding electrode material and applications for a variety of reasons. Depending on the effectively isolate the defect, causing only a slight drop in type, they: capacitance. This phenomenon is called self-healing, and it is an exceptionally attractive feature of film capacitors ■■Exhibit controlled self-healing, which makes them impersince it reliably prevents short circuit failures. A cross vious to short circuit failures. section of polypropylene power film capacitors is shown ■■Lack a catastrophic failure mode and continue to be in Figure 1, along with a depiction of low- and high-energy functional after the 5% decrease in capacitance defined self-healing processes. as failure.

FIG 1 Film capacitor self-healing. From top left to bottom right: (1) the cross-sectional structure of a polypropylene power film capacitor; (2) a dielectric defect; (3) film capacitor self-healing; (4) low-energy self-healing; and (5) high-energy self-healing.

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measure capacitance temperatures Thinner metallic film dielectrics in real use conditions. These theralso reduce capacitor volume and Failure is typically mocouples are commonly embedweight. Over the last few years, pasdefined as a 5% ded near the center of the capacitors sive component manufacturers have due to the proximity of potential hot developed film capacitors that are capacitance loss from spots; although, hot spot locations three or four factors smaller and the initial value and vary by capacitor type, value, and lighter than previous film capacitors configuration. A graph showing the and, thanks to self-healing, are also carries no risk of a relationship between capacitance impervious to short circuit failures. short circuit. value, rated RMS current, and Rth is As such, advanced film capacitors have experienced rapid growth in ac shown in Figure 3, but this type of filtering applications. Several manugraph varies by capacitor size and facturers are even offering advanced packaging. film capacitors optimized for specific applications. These small and simple single-can film capacitors There are currently four basic types of polypropylene are renowned for their safety and performance. Unlike power film capacitors optimized for common mediumaluminum electrolytic film capacitors, these film capacipower ac conversion applications: single-can power film tors don’t have a catastrophic failure mode. Instead, they capacitors, three-phase single-can power film capacitors, simply experience a parametric loss of capacitance. Failsingle-package PCB-mount power film capacitors, and ure is typically defined as a 5% capacitance loss from the miniature, safety-rated printed circuit board (PCB)-mount initial value and carries no risk of a short circuit. Power power film capacitors (Figure 2). film capacitors also continue to be functional even after this 5% decrease. Polypropylene film capacitor wear-out is related to the Single-Can Power Film Capacitors hotspot temperature of the capacitor and can be approxiSmall, ac-rated single-can power film capacitors based on mated using the following formula: a metallized polypropylene dielectric that operates from −40 °C to +85 °C are widely used for single-phase output filtering in ac power converters equipped with WBG semiθ hotspot = θambient + (Pd + Pt) × Rth conductors. These parts exhibit high dielectric strength and are typically rated for operating voltages extending in which from 250 to 690 Vrms, capacitance values extending from Pd (dielectric losses) = Q × tgδ 0 10 to 600 µF, and current ratings 6.5–50Arms. They are typically housed in simple radial aluminum can housings with diameters spanning 45–106 mm, lengths up to 247 mm, M8 tgδ 0 (tan delta for polypropylene) = 2 × 10−4 for frescrew terminals or fast-on/spade connectors, and an overquencies up to 1 MHz (independent of temperature) pressure disconnect system for added safety. The equivalent series inductance (ESL) of these single cans ranges Q × tgδ 0 = [½ × Cn × (Vpeak to Vpeak)2 × f] × tgδ 0 between 160 and 240 nh. Oftentimes, capacitor manufacturers will offer embedded K-type thermocouples that allow end customers to Pt (thermal losses) = R s × (Irms)2

FIG 2 The evolution of ac power film capacitors (from left to right): a single-phase/single-can film capacitor, three-phase single-can film capacitor, PCB-mounted film capacitor, and safety-rated PCB-mounted film capacitor.



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FIG 3 This graph illustrates the relationship between capacitance value, rated RMS current, and Rth for KYOCERA AVX FLA series ac filtering aluminum can capacitors rated for 250 Vac.

This hotspot calculation can be used along with applied working voltage to rated voltage ratios and a graph of expected lifetime versus hotspot generated to clearly show the positive effects of running capacitors at reduced voltages and temperatures (Figure 4).

Three-Phase Single-Can Power Film Capacitors To build upon the successful performance that small, ac-rated singlecan power film capacitors exhibited in advanced systems equipped with WBG semiconductors, passive component manufacturers developed a FIG 4 Lifetime expectancy versus hotspot temperature and voltage for polypropylene three-phase version that offers film capacitors. improved volumetric efficiency and ease of use. Like the single-can version, these three-phase single-can power film capacitors Cn is measured in Farads; have a metallized polypropylene dielectric proven to exhibit reliable performance in operating temperatures V stands for Volts; extending from −40 °C to +85 °C, are designed with the same overpressure disconnect system for added safety, Rth is measured in °C/W; and are available in Delta or wye configurations. See Figure  5—pinout diagram for three phase single can polyIrms is measured in Amperes; propylene capacitor. They are ideal for use in medium-power ac applications, R s is measured in Ohms; tend to be rated for 230–690 Vrms, and have a typical capacitance range of 3× 20.3 to 3× 335 µF since they’re equipped f is measured in Hertz; and with three capacitors that are not connected in series. Their estimated lifetime, the end of which is defined by a 5% drop θ is measured in °C.

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Miniature, Safety-Rated PCB-Mount Power Film Capacitors

FIG 5 A pin-out diagram for a three-phase single-can polypropylene film capacitor.

in capacitance, is estimated to be 100,000 hours at rated voltage and 70 °C, and they are typically housed in radial aluminum cans with diameters spanning 85–136  mm, lengths extending from 160 to 350 mm, and screw-style terminal connections.

Single-Package PCB-Mount Power Film Capacitors Single-package PCB-mounted power film capacitors are also based on metallized polypropylene dielectrics and exhibit the same self-healing characteristics as higherpower radial film capacitors. PCB-mount variants are specifically designed for printed circuit board mounting and are housed in UL94 V-0 self-extinguishing plastic cases backfilled with a UL94 V-0 self-extinguishing thermosetting resin. They are available in both two- and four-terminal designs with package sizes as small as 32 × 22 × 13 mm (L × W × H). As expected, these small package sizes result in decreased device inductance, typically spanning 24–38 nH, which makes their high-frequency characteristics attractive to designers. The small case size of single-package PCB-mounted film capacitors can also result in lower current ratings, with typical values ranging from 4 to 22 A. Typically, these components offer capacitance values spanning 1–50 µF and are rated for working voltages extending from 250 to 350 Vrms. These characteristics combined make single-package PCB-mounted power film capacitors ideal for miniature output ac filtering in power converters, uninterrupted power supply (UPS) systems, solar inverters, motor drives, and other advanced applications equipped with WBG semiconductors.

Miniature PCB-mount power film capacitors developed for use in ac applications have proven that the reliability of larger radial-can power film capacitors, whether single- or three-phase, can be successfully scaled down. Passive component manufacturers leveraged this discovery to develop miniature, safety-rated PCB-mount film capacitors optimized for use in active ac device applications equipped with WBG semiconductors. These safety-rated PCB-mount power film capacitors are based on the same consistent dielectric material system of metallized polypropylene film covered with extremely thin, vapor-deposited electrodes as the other power film capacitors I’ve addressed thus far, but there are a few notable differences between them. In addition to packaging, capacitance value, and voltage rating differences, safetyrated film capacitors are available with a wider operating temperature range than the other power film capacitors: −40 °C to +110 °C rather than −40 °C to +85  °C, which effectively overcomes the biggest drawback of power film capacitor technology. They also have high pulse ratings designed to maximize breakdown voltage, while the other three power film capacitor technologies I’ve addressed are designed for max current and peak current. These non-inductively wound, self-healing film capacitors are encapsulated in solvent-resistant and self-extinguishing UL94 V-0 thermoplastic cases sealed with epoxy resin, which creates a highly moisture-resistant package. They are available in multiple case sizes ranging from 13 × 11 × 5 to 41.5 × 45 × 30 mm (L × W × H) and are typically available with capacitance values ranging from 10 to 10 µF, a 305 Vrms working voltage rating, and dielectric strength optimized to 1,312 Vdc for 60 seconds or 2,000 Vdc for 2 seconds. Ideal applications include across-the-line line ac safety capacitors and EMI filters.

Power Film Capacitors—Present and Future Power film capacitors optimized for use in active ac devices equipped with WBG semiconductors have directly contributed to recent improvements in power conversion efficiency, which is an increasingly important benefit given current and growing power circuit and grid demands. Additional benefits of film capacitors that make them very attractive to advanced power device designers include self-healing and soft failure mode characteristics. The importance of film capacitors’ failure mode being just a 5% drop in film capacitance, rather than a short circuit, as is the case with aluminum electrolytics, cannot be overstressed. It’s also important to note that film capacitors continue to operate at reduced capacitance values, even as they proceed to fail beyond the 5% limit defined in manufacturers’ specifications, which allows end users to identify the “failure” and perform preventative maintenance to ensure the optimal long-term, failure-free performance of the circuit. September 2023

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and shock on the component, and some of these can be used in a way that also reduces capacitor inducParameter Film Technology MLCC Technology tance (Figure 6). Package Type Radial Can, Box, or SMT SMT Lead Frame, Through-Hole Stacked NP0 capacitors with Operating Temperature −40 °C to +110 °C −55 °C to +150 °C or +200 °C higher voltage and temperature ratRange ings are currently in development, Environmental Impact RoHS Compliant RoHS Compliant and it is reasonable to assume that Failure Mode Soft Short stacked NP0 MLCC capacitance values will increase by around one order of magnitude, that costs will drop significantly, and that higher temperature operating dielectrics will become readily available in the next few years. Although the capacitance values of NP0 components won’t match those of single- or multi-phase power film capacitors in the near term, the most demanding ac power active device applications—for example, flight systems—will likely make use of cuttingedge NP0 ceramic capacitors and stacked capacitor to satisfy efficiency and size targets for electrical circuitry. In addition, novel stacking schemes, such as horizontally stacked capacitors and vertical stacked horizontal arrays, FIG 6 A three-layer horizontally stacked NP0 capacitor (left) will likely use of high-CV emerging base metal electrode and a lead-frame NP0 MLCC (right). NP0 MLCCs as building blocks for advanced ac power applications. And as these use cases continue to become more mainstream, stacked ac MLCCs should continue to Future advances in power film capacitor designs will expand their capabilities and offer an even greater swath of continue to offer reduced inductance, smaller case sizes, beneficial characteristics optimized for WBG applications. and higher reliability, at least for the foreseeable future.

Table–– 1. A comparison between NP0 capacitors and ac-rated film capacitors.

Beyond Power Film Capacitors

About the Author

As passive component manufacturers continue to innovate in service of advanced, WBG-enabled active device designs, practical designs will begin to leverage new materials and packaging. The most notable of these non-film-capacitor components are currently high-voltage NP0 ceramic multilayer ceramic capacitors (MLCCs) and stacked NP0 MLCCs. Stacked NP0 capacitors regularly achieve capacitance values of 430 nF at 1 kV dc and 78 nF at 5 kV dc, and material improvements and process advances are increasing these values by significant ratios. Regardless of the specific form factor or capacitance value, NP0 dielectric capacitors can exhibit low-loss operation at operating temperatures up to 125 °C, or even 200 °C (Table 1), as well as high operating frequencies. Examples of high-frequency NP0 resonant capacitors include 400–800 Hz avionic ac line filters, snubbers, and high-current repetitive discharge circuitry. Stacked NP0 capacitor technology, which is the MIL version of C0G capacitor technology, also has the potential to reduce the equivalent series resistance (ESR) and equivalent series inductance (ESL) of capacitors intended for use in WBG circuitry, which effectively increases the frequency at which the capacitors can be used. Stacked capacitors commonly have lead frames that can reduce thermal stress

Ron Demcko ([email protected]) is a Senior Fellow with KYOCERA AVX in Fountain Inn, Fountain Inn, SC, USA. This role centers on projects ranging from simulation models for passive components to product support, new product identification, and applied development. Prior to this role, he was the EMC Lab Manager with AVX in Raleigh, Raleigh, NC, USA. This lab concentrated on subassembly testing and passive component solutions for harsh electrical and environmental applications. Before that, he was an AVX Application Engineer for products including integrated passive components, EMI filters, and transient voltage suppression devices. Prior to joining AVX, he worked as a Product Engineer and, later, a Product Engineering Manager in the electronics division at Corning Glass Works. In these roles, he supported the development, production, and sale of pulse-resistant capacitors, high-temperature capacitors, and radiation-resistant capacitors, developed high-frequency test methods, and co-developed hightemperature test systems. He received the B.S.E.E. degree from the Clarkson College of Technology (now Clarkson University) in 1982.

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©SHUTTERSTOCK.COM/TRZMIEL

Addressing Power Decoupling in High-Performance, High-Frequency Applications Using E-CAP by Mukund Krishna and Luca Vassalli

A

s one of the most basic and fundamental components in electronics, capacitors are used in large numbers across a variety of designs. A key requirement for applications such as mobile phones, IoT devices, and high-performance compute applications is to effectively address last mile power delivery challenges, such as

Digital Object Identifier 10.1109/MPEL.2023.3301415 Date of publication: 26 September 2023

2329-9207/23©2023IEEE

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require multiple low voltage (0.4–1.0 high-frequency power demands for the Vdc) power rails and tight adherence high-performance processors that The magnitude and they are inevitably based on. While to voltage regulation specifications, frequency of traditional multilayer ceramic capacitypically within ±1.0%. tors (MLCCs) have fulfilled the Board-mounted switching dc– instantaneous power requirements thus far, stricter condc converters offer a viable method demands are growing straints on power density are challengof provisioning high power direct ing the continued usage of the existing to computational devices such as in steps of 100% for model. FPGAs, GPUs, and neural network subsequent, placing a As system engineers look to processors (NPUs). deliver the promised and expected While the dc–dc converters unique and performance in smaller form factors, mounted on the PCB provide adechallenging stress on provision of the most efficient power quate dc power to these workloads, de-coupling solution is a critical their frequency of operation, and power integrity design consideration. In this article, hence bandwidth (which is the ability solutions. we examine the decoupling requireto respond to ultra-fast current tranments of typical high-performance sients), is orders of magnitude lower systems, consider how factors such than what is required. Further, the as equivalent series inductance (ESL) sheer volume of such solutions render and capacitance density play a key role in improving perthem being located at distances far enough away that any formance density. We then further illustrate how Empower ability to service fast transients is rendered useless by the Semiconductor’s E-CAPs can effectively address these high impedance to the processor. challenges. The electrical noise generated from transients, power supply ripple, and other noise artifacts can significantly impact the performance of the computational ICs and the Introduction other circuit functions. Signal integrity is tightly associated It is currently estimated that over 1 trillion capacitors are with power integrity in any complex application, and such produced every year, of which 800 billion [1] are surface artifacts can create “ringing” oscillations across the whole mount MLCCs also known as “chip” capacitors. system. Digital processors made with the most advanced These ubiquitous devices are used to address requireprocess nodes such as 5 nm have extremely tight tolerances ments across the complete power and voltage range in applion voltage supply to avoid “brown-out” at the lower end and cations, including energy storage, filtering, and decoupling “over-voltage” on the upper end. of power rails to filter out unwanted ripple and noise. The Analog ICs used in data conversion signal chains are parexponential growth in the creation of high-performance ticularly vulnerable to power delivery network (PDN) noise, computing led by the rapid advent of artificial intelligence with its power supply rejection ratio as a critical indicator (AI) and machine learning, has led to what are collectively of susceptibility. As any analog IC’s datasheet will highlight, termed high-performance compute applications. small variations of supply voltage can upset the function’s The magnitude and frequency of instantaneous power operation, for example, the introduction of jitter on clock sigdemands are growing in steps of 100% for subsequent, nals or the reduction of analog conversion accuracy. placing a unique and challenging stress on power integrity solutions. 

Decoupling Power Rails Challenges of Power Delivery for High-Frequency, High-Performance Applications When it comes to the latest data-intensive systems built around high-performance, high-speed processors, and multiple power domains that operate with fast transients and low voltages, designers are finding a growing number of challenges with conventional MLCC technologies. These processors are increasingly used on highly dynamic workloads, such as running AI algorithms and neural network models for machine learning and inference. For such applications, the peak current swings become significant, with instantaneous peak processor currents of 800 A to 1000 A in tens of nanoseconds becoming the norm. This results in extremely challenging (di/dt) current transients These high-performance devices usually

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As the last section highlights, minimizing transient, ripple, and noise artifacts from the PDN in high-frequency, highperformance applications is paramount. Decoupling PDN noise artifacts is an established engineering principle where multiple capacitors, typically MLCCs, of different values and case sizes, are placed across the supply rails. The aim is to provide a low impedance return path across a wide frequency range. To provide the most effective noise cancellation, the capacitors are placed closest to the noise sources and the power pins of sensitive ICs. Board layout will influence MLCC placement, a situation exacerbated by larger processor ICs requiring many tens of capacitors. At higher switching and computational frequencies, PCB trace parasitics and the equivalent circuit characteristics of the MLCCs also become significant.

Parasitic Characteristics Limit MLCC Selection for Decoupling MLCCs have fulfilled decoupling requirements for decades; unfortunately, as high-frequency processing applications become the norm, several factors will limit their abilities for specific applications.  Alas, no capacitor is ideal and suffers from several parasitic factors that will cause its impedance to change, most notably at high frequencies. Figure 1 illustrates the equivalent circuit of a capacitor, with the parasitic elements highlighted.  For example, the metal electrodes and end caps contribute to an equivalent series inductance (ESL) that impacts the capacitor’s resonant frequency. All things being equal, the lower the ESL, the higher the resonant frequency. Above its resonant frequency, a capacitor’s effective impedance becomes inductive in nature, or in other words, increases with frequency. Hence, there is an imperative to keep ESL as low as possible for capacitors used in high-performance, high-frequency applications.  Another critical issue is capacitor de-rating, with the key de-rating factors impacting MLCCs being voltage, temperature, and age.  An average MLCC, for example, will see its capacitance value reduce as the dc bias voltage increases [2]. Capacitance also reduces as the temperature increases, with the degree of change dictated by EIA code used to classify the temperature co-efficient [3]. AC or DC bias voltage has an impact on aging characteristics that produce a decrease in capacitance over time due to changes in the dielectric’s crystal structure [4]. To allow for these characteristics,

FIG 1 The lumped model equivalent circuit of a capacitor includes series inductance (ESL), series resistance (ESR), in addition to its capacitance.



design engineers are forced to increase the number of MLCCs specified significantly. This over-specification of the product’s BOM ensures that the necessary decoupling capacitance is provided over the product’s lifetime and across the entire anticipated range of operating conditions. In turn, accommodating the need for many MLCCs impacts the product’s mechanical design attributes, from form factor and power density to PCB layout flexibility, reliability, and cost. In general, the more capacitors that are deployed, the further away the capacitor network is likely to be from the processor itself, increasing the series inductance and introducing further opportunities for parasitics to impact system performance, especially at high frequencies. The product’s calculated reliability metric will also be lower since the overall component count negatively influences reliability.

Comparing MLCCs to Silicon Capacitors— What are the Differences? MLCCs have a typical construction as illustrated in Figure 2. The capacitors are formed by alternating plates of metal (electrodes) with a dielectric material in between. The long plates connect to the terminals on either side providing contacts to the outside world. Since parasitic inductance is proportional to length of the metal path that current or charge must travel along, the long electrodes within MLCCs lead to inherently higher ESL. Silicon capacitors are a relatively new innovation and can be illustrated by technology in which vertical trenches create capacitors in silicon using an ultra-fine lithography process. With this approach, many capacitors are formed in a very small space where electrodes are orders of magnitude shorter than MLCCs, providing the same order of magnitude reduction in ESL. A large number of such capacitor cells (100s or 1000s) are connected in parallel to form a single capacitor providing further reduction in effective ESL. Standard metal layers available in silicon-based semiconductor processes provide the ability to connect to the electrodes anywhere on the silicon die, enabling unmatched termination flexibility and performance. Utilizing silicon-based semiconductor processes also provides an inherent stability against variations in voltage, temperature and ageing that MLCCs struggle with, resulting in a much more stable and reliable product.

FIG 2 Multilayer ceramic capacitor construction—long electrodes contribute to higher ESL.

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Table 1 summarizes the technical differences between a conventional MLCC and a silicon E-CAP. As highlighted above, the de-rating, aging, and parasitic factors of an MLCC present hardware design engineers with serious considerations. The combined impact of an MLCC’s aging and de-rating factors is illustrated in Figure 4. Achieving a circuit’s desired effective capacitance value requires an MLCC or multiple MLCCs with a much higher nominal capacitance value. Note that the capacitor’s specified tolerance values are also considered. The table in Figure 4 showcases a 54 nF E-CAP compared to an example 100 nF MLCC. The effective capacitance achieves the required 44 nF, but the E-CAP achieves this with only the initial tolerance specification added and is far more resistant to aging. In this example, double the number of MLCCs would be required, impacting board space and layout. FIG 3 Layout density improvement achievable using E-CAPs compared to standard MLCCs. Another aspect of silicon capacitors is their impedance versus frequency characteristic. Figure 5 illustrates how the Table 1. Comparing the attributes of MLCCs against E-CAPs. –– low ESL attributes of an E-CAP offer excellent high-frequency Parameter Standard MLCC ECAP impedance characteristics DC bias de-rating 44% @ 3 V None above 50 MHz. For example, Temp de-rating -11% up to 85°C Negligible - ~0.3% (measured in an average MLCC may have an ppm/K) – equivalent to C0G ESL of 200 pH compared to an Aging ~5-10% / 10k hrs 100pH (100nF) 90%. Table 1. CPM specifications. ■■Charging of all types of passenger vehicles (sport, sedan, and SUV) with one common GPM. CPM parameter Value ■■Power transfer through materials (if GPM is buried). Ground clearance (full power transfer) 123–224 mm ■■Intelligent and safe [to comprise, e.g., foreign object Battery voltage range, full power transfer 525–825 V detection (FOD) and living object protection (LOP)]. Battery voltage range, power derating 470–525 V ■■Working with parking X/Y-axis misalignments of Cooling Liquid, forced ±75/±100  mm and angle-misalignment (e.g., yaw, pitch, and roll), respectively.

Inductive Charging System The era of wireless power transfer started more than a century ago with the work of Nikola Tesla [9], a Serbian-American scientist and inventor. However, research interest in this topic started to increase only in the last 22 years [10]. Having reviewed 15 review papers on the topic it was noticed that researchers’ focus was on: power transfer, efficiency increase, coil design, materials, control, compensation circuits, ancillary and protection features, standards, etc. [11]. The only topic that was not covered, in the analyzed literature, is the auxiliary power supply of the ground

FIG 2 High-level generic block-diagram of an ICS (power flow only) [11].

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Table 2. GPM specifications. GPM parameter

Value

Input power

3.7–11 kVA

DC link voltage range, full power transfer 650–850 V Ground-car clearance

Z1–Z3 height classes

Ambient temperature range

−40°C to 50°C

Cooling

Air, forced

FIG 3 The CPM (upper) and GPM (lower) modules of the first generation ICS 3.6 kVA. Source: BRUSA Elektronik AG.

efficiency maps. This is a common design way to present results because with ■■Testing, verification, functional The ICS efficiency is 3D plots one would not be able to see safety, and approvals evaluated for all key points. The efficiency maps of ■■Software 11 kVA ICS for Z-heights of 123 mm and it is difficult to evaluate (in %) different X/Y and 200  mm are given in Figures 4 how much each category adds to the misalignments and and 5, respectively. Here, one can see complexity. All are equally important that the delivered power to the high and challenging in order to bring an heights, and such voltage (HV) battery in the vehicle ICS to the mass market. results are called is always 10.1  kW. Also, we see that Specifications of the 800 V car pad the ICS efficiency varies depending module (CPM) and GPM are given in efficiency maps. on X/Y alignment, as expected. In Tables 1 and 2, respectively. Note that Table 3, a comparison between the the GPM can equally work with 400 V first and the second ICS generations and 800 V CPMs. Please be aware that is provided. Here, we can see that the ICS, described in this article, is part not only was efficiency improved, but also several new or of a commercial project, hence not all technical details may be improved safety and communication related features are revealed. Therefore, only representative photo of the first genimplemented in the new system. eration was allowed to be shown and is given in Figure 3. BRUSA systems use wireless bidirectional communiThe ICS efficiency is evaluated for different X/Y miscation between GPM and CPM to ensure that the GPM alignments and heights, and such results are called ■■Mechanical

FIG 4 The ICS efficiency map at Z = 123 mm height.

FIG 5 ICS efficiency map at Z = 200 mm height.



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Table 3. Comparison of the first and second Generation BRUSA ICS. Parameter

ICS first gen

ICS second gen

Input voltage and current

230 V, 50 Hz; 16 A

400/230 V, 50 Hz, 16 A 240/120 V, 50/60 Hz, 50 A

Input power

3.6 kVA

11 kVA

Efficiency range*

83%–88%

88.9%–91.9%

Connectivity

Wireless proprietary protocol

IEEE 802.11 ISO 15118

Positioning measurement range

Up to 300 mm

Up to 10 m

Positioning accuracy

±2 cm

Short range: ±2 cm

FOD detection sensitivity

5-cent coin

Paper clip

LOP detection sensitivity

Capacitive sensing

Radar sensing

Cooling, CPM

Air, passive

Liquid, forced

Cooling, GPM

Air, passive

Air, forced

Surface mounted

Yes

Yes

*From GPM input to HV battery in EV for all X/Y alignments and Z-heights.

FIG 6 Positioning system. Source: BRUSA Elektronik AG.

transfers right amount of power when requested by the CPM. The CPM further communicates with relevant vehicle control units thus ensuring maintenance of right state of the HV battery. In addition, the ICS second generation follows the ISO15118 standard series, in particular ISO15118-8:2020 and ISO15118-20:2022.

Auxiliary Power Supply The auxiliary power supply is called low voltage power supply (LVPS) at BRUSA. It supplies the microcontrollers, gate drivers, measurement circuits, and all other embedded hardware [13]. An active-clamped

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flyback (ACF) dc–dc converter was chosen as the topology; its specifications are given in [12] and [13]. Specific to the ICS application is that the LVPS has two input voltage ranges and two different loading states of its outputs depending on whether ICS operates in power transfer mode or stand-by mode [12]. In addition, since the ACF input voltage (i.e., dc link) approaches 880  V, including ripple, the 1700  V SiC switches had to be used. The SiC switches are cheaper and better choice than the Si counterparts [12]. More info on the LVPS solution and related challenges can be found in [12] and [13].

Ancillary Systems

Frequently Asked Questions

The ancillary systems perform safety related functions and are complex. They can be grouped into four categories: ■■Positioning system (POS). It uses the “time of flight” method and is shown in Figure 6. ■■Foreign object detection (FOD). It uses the “Impedance measurement” method, which is a well-known solution in the industry. ■■Living object protection (LOP). It uses radar and its coverage area is shown in Figure 7. ■■Various communication types are used (e.g., WLAN and CAN) with more new ones to come.

When discussing with engineering and/or academic audiences several typical comments or questions arise frequently. An overview, including our answers to those questions, is provided in Table 4.

FIG 7 Living object protection. Source: BRUSA Elektronik AG.

Future Steps and Challenges BRUSA teams are working on continuous improvement of our products. Upcoming ICS enhancements can be grouped into following areas: ■         Volume, weight, and price reduction. ■         Performance improvement. ■■Contributing to development of international ICS related standards. All standards are expected to be released in 2023. During development of complex and unique product like ICS many challenges arise like: ■         Finding suitable engineers, i.e., utilizing right engineering expertise for HW, SW, and simulation areas. The ICS is an emerging application, hence there is limited number of experienced engineers available on the market. We saw that more people are available with experience in research projects, but not in automotive ones (e.g., especially for products in series production). ■         Handling large number of customer requirements for HW and SW domains (e.g., 5-digits order of magnitude). ■         Global supply-chain problems.

Table 4. Typical comments and questions related to an ICS.



Comments or questions

Feedback

The ICS is just comfort convenience for drivers of premium vehicles without any other advantages.

■■Advantages

Why is primary coil not located at the front of the vehicle to have better coupling and hence higher efficiency? Such solutions exist for automated guided vehicles in warehouses.

There are many reasons for not doing that with passenger vehicles like: ■■Safety of people would be low because HV circuits would be in the vehicle crash-zone. ■■There is not much space in that area hence CPM would be accordingly small and more difficult to design. ■■Exposure of pedestrians to high magnetic fields ■■LOP would be more complicated and is likely to cause false triggers. ■■More design and operation challenges for vehicles with different heights (i.e., interoperability issues). ■■High costs.

Could a robotic platform be used to align GPM in X, Y, Z-directions and achieve better coupling with different types of vehicles?

That is not desirable due to increased cost, weight, complexity, maintenance, and safety risks. Moreover, in general, movable parts are not wanted in an ICS for passenger vehicles.

What will happen if someone passes by the EV, while the driver is away, and accidentally drops a metal coin causing charging to stop?

The driver would be notified, via SMS or an App, that the ICS has stopped working and that action is needed to resume charging of the vehicle.

are in person’s safety too since, to our best knowledge, no data are available on wear and tear of the charging cables for longer period of use. ■■For autonomously driven passenger vehicles the ICS is a desirable solution.

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■         Education

of existing and potential customers. The customers are typically coming from the automotive business, but still need to be educated in techno-economical tradeoffs related to an ICS development.

Conclusion The development of an ICS, a complex and unique product, with a number of technologically sophisticated subsystems, requires the know-how and close collaboration of engineers from various fields of expertise. It takes a lot of time, dedication, and upfront investment as well. We do believe in the bright future of such a device in this emerging application since BRUSA has acquired the largest OEM series contract in the industry so far.

The development of an ICS, a complex and unique product, with a number of technologically sophisticated subsystems, requires the know-how and close collaboration of engineers from various fields of expertise.

Acknowledgment This work was supported by BRUSA Elektronik (München) GmbH, Munich, Germany. Authors would like to thank BRUSA management, especially T. Nindl, L. Böhler, A. Diefenthaler, and many other colleagues for support.

About the Authors Darko Vracˇar ([email protected]) received the Dipl.Ing., Magister, and Ph.D. degrees in electrical engineering from the School of Electrical Engineering, University of Belgrade, Belgrade, Serbia, in 2000, 2007, and 2023, respectively. His major field of study was power converters and drives. He is with BRUSA Elektronik (München) GmbH, Munich, Germany. He has 22 years of industrial experience. Some areas of expertise are implementation of telecom and datacenter power supplies, and research and development of power electronics’ systems, such as solar inverters, SMPS for industrial, automotive, and telecom applications. He has published several papers related to power converters and drives and holds one patent in power conversion systems. His research interests include simulation, control, and design of power converters. He is a Senior Member of the IEEE. Sebastian Wüstner received the Ph.D. degree in computational physics from Imperial College London in 2012. From 2012 to 2014, he worked as a Postdoc at Imperial College researching active light-matter interaction of metamaterials and plasmonics via simulation. His interest in wireless charging systems, magnetic coupling, and soft magnetic materials started with moving to industry in 2014.  He currently works as the Head of simulation and the Head of mechanical design at BRUSA Elektronik (München) GmbH, Munich, Germany. His interests are in the advancement of inductive charging through new topologies and materials, in modern simulation technology, and the concept of digital twins.

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References

Alkiviadis Boulos received the B.Eng. degree in electrical power engineering from the University of Glasgow, Glasgow, U.K., in 1998, and the master’s degree in power engineering from Herriot Watt University, U.K., in 1999, and in control theory and applications from Coventry University, U.K., in 2001, where he received the Ph.D. degree in vehicle electrical power supply and electrical energy management systems, in 2020. He has an automotive experience of over 21 years in the fields of systems engineering, simulation, software development, vehicle product development, power electronics, and electrification. He is currently the Director of engineering at BRUSA Elektronik (München) GmbH, Munich, Germany.

[1] Brusa Elektronik AG. Accessed: Apr. 6, 2022. [Online]. Available: https:// www.brusa.biz [2] H. K. Bai et al., “Charging electric vehicle batteries: Wired and wireless power transfer: Exploring EV charging technologies,” IEEE Power Electron. Mag., vol. 9, no. 2, pp. 14–29, Jun. 2022, doi: 10.1109/MPEL.2022.3173543. [3] A. Mahesh, B. Chokkalingam, and L. Mihet-Popa, “Inductive wireless power transfer charging for electric vehicles—A review,” IEEE Access, vol. 9, pp. 137667–137713, 2021, doi: 10.1109/ACCESS.2021.3116678. [4] H. Feng et al., “Advances in high-power wireless charging systems: Overview and design considerations,” IEEE Trans. Transport. Electrific., vol. 6, no. 3, pp. 886–919, Sep. 2020, doi: 10.1109/TTE.2020.3012543. [5] D. Đ. Vracˇ ar, “Quasi-resonant flyback converter as auxiliary powersupply of an 800 V inductive-charging system for electric vehicles,” IEEE Access, vol. 10, pp. 109609–109625, 2022, doi: 10.1109/ACCESS.2022.3214526. [6] IEA, Paris, France. (May 2022). The Global EV Outlook 2022. Accessed: Jun. 6, 2022. [Online]. Available: https://www.iea.org/reports/global-evoutlook-2022 [7] Market Research Report and MarketsandMarkets. (2022). Wireless Charging Market for Electric Vehicles. Accessed: Jun. 6, 2022. [Online]. Available: https://www.marketsandmarkets.com/Market-Reports/wireless-evcharging-market-170963517.html [8] Shell Recharge Solutions. (May 2022). EV Driver Survey Report 2022. Accessed: Jan. 10, 2023. [Online]. Available: https://shellrecharge.com/en-gb/ solutions/knowledge-centre/reports-and-case-studies/ev-driver-survey-report [9] A. Kurs et al., “Wireless power transfer via strongly coupled magnetic resonances,” Science, vol. 317, no. 5834, pp. 83–86, Jul. 2007, doi: 10.1126/ science.1143254. [10] J. Hirai, T.-W. Kim, and A. Kawamura, “Study on intelligent battery charging using inductive transmission of power and information,” IEEE Trans. Power Electron., vol. 15, no. 2, pp. 335–345, Mar. 2000, doi: 10.1109/63.838106. [11] D. Đ. Vracˇar, “Active-clamped converter as an auxiliary primary-side power supply of a system for wireless inductive battery-charging of electric vehicles,” (in Serbian) Ph.D. dissertation, School Elect. Eng., Power Converters Drives Dept., Univ. of Belgrade, Belgrade, Serbia, 2022. [12] D. Đ. Vracˇ ar and P. V. Pejovic´, “Active-clamp flyback converter as auxiliary power-supply of an 800 V inductive-charging system for electric vehicles,” IEEE Access, vol. 10, pp. 38254–38271, 2022, doi: 10.1109/ ACCESS.2022.3165059. [13] D. Đ. Vracˇar and P. V. Pejovic´, “Active-clamped flyback DC–DC converter in an 800 V application: Design notes and control aspects,” J. Electr. Eng., vol. 73, no. 4, pp. 237–247, Aug. 2022, doi: 10.2478/jee-2022-0032. [14] Electric Vehicle Wireless Power Transfer (WPT) Systems—Part 3: Specific Requirements for Magnetic Field Wireless Power Transfer Systems, Standard IEC 61980-3:2022, IEC, Nov. 2022. 

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A Survey on ImpedanceBased Dynamics Analysis Method for InverterBased Resources by Heng Wu, Fangzhou Zhao, and Xiongfei Wang

I

mpedance-based method has been increasingly adopted to assess the stability of inverter-based resources (IBRs). To get a better view of the stateof-the-art and challenges for implementing the impedance-based dynamic analysis, a survey with

general/specific questions has been initiated by IEEE Task Force on Frequency-Domain Modeling and Dynamic Analysis of High-Voltage Direct Current (HVDC) and Flexible AC Transmission System ( FA C T S ) . T h e f e e d b a c k s a r e c o l l e c t e d f r o m

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universities, national labs, transmission system operators (TSOs), power plant developers, as well as IBR vendors. It is interesting to note that while many common understandings have been established in practices, certain gaps still exist among different stakeholders. This article intends to bridge this gap by sharing a summary of the survey, including questionnaires, responses from different stakeholders, and the analysis of survey results. The challenges for different stakeholders using impedance-based method are identified, which shed a light on the future research work.

Introduction The legacy power grids that are dominated by electrical machines are gradually evolving as power-electronic-based power systems with high proportion of IBRs and active loads. The multi-timescale control dynamics of IBRs may interact with one another and with grid dynamics, leading to resonances and instabilities in a wide frequency range [1], [2]. Addressing these challenges call for new methods and tools for dynamics analysis of IBR-dominated power systems. The impedance-based dynamics analysis method is increasingly used to screen stability risks of IBRdominated power systems, mainly due to its advantage of dealing with black-box models [3], [4], as shown in Figure 1. Over past years, numerous efforts have been devoted, from both academia and industry, to advance this technology [5], [6]. However, certain gaps persist among different stakeholders. An over-simplified IBR-grid system with a few or even single IBR is often used by academia for the impedance-based dynamic

analysis. Such a simplified system may not be capable of reflecting all practical challenges in complex electrical systems, where thousands of IBRs can be configured in meshed and radial network structures. On the other hand, practicing engineers may not be aware of the latest advances in the impedance modeling theory and dynamics analysis. To bridge the gaps, the joint IEEE Power Electronic Society (PELS) and IEEE Power and Energy society (PES) Task Force on Frequency-Domain Modeling and Dynamic Analysis of High-Voltage Direct Current (HVDC) and Flexible AC Transmission System (FACTS) made a questionnaire survey on the impedance-based dynamics analysis, aiming to obtain insights into the latest state-of-the-art and challenges of using this method. The survey got 46 responses from a diverse range of participants (54% from academia and 46% from industry), including universities, national labs, transmission system operators (TSOs), power plant developers, as well as IBR vendors across the globe. More detailed statistics of the survey participants are given in Tables 1 and 2. This article intends to share the survey results and summarize both common and unique challenges for different stakeholders in implementing impedance-based method, which shed a light on the future research work in this direction.

Questionnaire and Responses The questionnaire is designed with five general questions and six specific technical questions, the details of which are described by Q1–Q12 as follows. The corresponding response to those questions are given by Figures 2–13.

FIG 1 Impedance-based dynamic analysis for IBR-dominated power system.

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–– Table 1. Respondent sector statistics.

Respondent Sector Academia

Industry

Number

University

25

National lab

3

TSO

5

Power plant developer

1

IBR vendor

12

Table 2. Geographic location of respondents. –– Geographic Location

FIG 3 Response to Q2. (a) Response from academia. (b) Response from industry.

Number

Q1 Do you use the impedance-based (frequency scan) method for dynamics analysis? A) Yes B) No C) Not yet, may use it in the future Q2 What is your level of confidence on analysis results if using the impedance-based method? A) Very confident: The impedance-based analysis results agree with EMT simulations (and/or field measurements). B) Confident: The mismatch between impedance-based analysis results and EMT simulations (and/or field measurements) are acceptable or explainable. C) Less confident: The mismatch between impedancebased analysis results and EMT simulations (and/or field measurements) are often not acceptable, nor explainable. Q3 For transmission system operators (TSOs) and power-plant owners/developers, please select three most challenging issues for using impedance-based method.

A) No high-fidelity EMT models that can be used for impedance measurement. B) No automated tools for impedance measurement. C) Too time consuming to measure impedances over multiple operating points. D) No method to verify the accuracy of measured impedances. E) No theory/method for impedance-based dynamics analysis of multi-IBR systems. F) Mismatch between impedance-based analysis results and EMT simulations (and/or field tests). G) No clear insight into cause of instability can be provided from black-boxed impedance models. Q4 For vendors of inverter-based resources, please select three most challenging issues for using impedance-based method. A) No high-fidelity EMT model of electrical system that IBR is connected to. B) No impedance specifications/requirements for control dynamics of IBRs. C) No efficient tools for impedance modeling and impedance measurement. D) Too time consuming to measure impedances over multiple operating points. E) No theory/method for impedance-based dynamics analysis of multi-IBR systems. F) No clear design guideline obtained from impedance modeling.

FIG 2 Response to Q1. (a) Response from academia. (b) Response from industry.

FIG 4 Response to Q3 from TSOs and power-plant owners/ developers.

North America

8

Europe

23

Asia/Pacific

15

A. General Questions



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B. Technical Questions

FIG 5 Response to Q4 from IBR vendors.

Q5 What need to be further developed for using impedance-based method? A) Defining clear specifications on impedance profiles of IBRs. B) Improved efficiency and accuracy of impedance measurements in offline EMT simulations. C) Impedance-measurement tools in controller-hardware-in-the-loop tests. D) Impedance-measurement tools in field tests. E) Impedance-based stability and sensitivity analysis methods for multi-IBR systems.

Q6 How do you select frequency range and frequency resolution for impedance measurement? A) Nyquist frequency of IBRs. B) Based on specific frequency range of oscillations. C) The maximum frequency of a black-box model specified by vendors. D) No clear guideline. Q7 Do you have any preference over the reference frames of impedance model, i.e., stationary (αβ) or rotating (dq) reference frame, albeit they are mathematically equivalent? A) Stationary (αβ) reference frame. B) Rotating (dq) reference frame. C) Positive-/negative-sequence. D) Positive-sequence only. E) No preference. F) Will do measurement in both frames and make cross-validations between them. Q8 Do you use the multiple-input multiple-output (MIMO) impedance matrix for dynamics analysis? A) Yes, because the accurate impedance model of three-phase balanced IBR is a 2 × 2 matrix.

FIG 6 Response to Q5. (a) Response from TSOs and power-plant owners/developers. (b) Response from IBR vendors.

FIG 7 Response to Q6. (a) Response from academia. (b) Response from industry.

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B) Yes, but the MIMO impedance matrix can be reduced to SISO impedance transfer function beyond certain frequency. C) No, because no efficient tool for measuring impedance matrix is available. D) No, only the single-input single-output (SISO) impedance transfer function is used for dynamics analysis.

Q9 How do you verify the measured impedance model? A) Check if the marginally stable case predicted by the impedance model agree with EMT simulation tests. B) Check if the step response of impedance model match with that of EMT simulation model. C) Compare the measured impedance data with theoretically derived impedance model.

FIG 8 Response to Q7. (a) Response from academia. (b) Response from industry.

FIG 9 Response to Q8. (a) Response from academia. (b) Response from industry.

FIG 10 Response to Q9. (a) Response from academia. (b) Response from industry.

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D) No clear guideline for verification. E) Not applicable: prefer to transform the impedance model to time-domain state-space model. Q10 Do you use aggregated impedance model of multiIBR system for dynamics analysis? A) Yes, while the aggregate model may not be 100% accurate, it can be used for preliminary dynamics analysis. B) No, the aggregated impedance model cannot accurately capture the dynamics of multi-IBR systems.

Q11 If aggregated impedance models are inaccurate, what factors will contribute most to the inaccuracy? A) Different steady-state operating points of individual IBRs. B) Control interactions between IBRs in an aggregated model. C) Different parameters of controllers and passive components such as filters and cables. Q12 How do you deal with the impact of operating point on the impedance-based method? A) Cover as many operating points as possible in the impedance measurement. B) Select multiple operating points following certain guideline, and be confident that the selected operating points cover the worst case. C) Select multiple operating points following certain guideline, but not sure if the selected operating points cover the worst case. D) No guideline on how to select operating points, but simply rely on engineering judgement.

FIG 11 Response to Q10. (a) Response from academia. (b) Response from industry.

FIG 12 Response to Q11. (a) Response from academia. (b) Response from industry.

FIG 13 Response to Q12. (a) Response from academia. (b) Response from industry.

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Key Results and Analysis A. State-of-the-Art Figure 2 clearly demonstrates that almost all respondents have used or intend to use the impedance-based method for dynamic analysis. There is also an increasing awareness on how the method should be correctly implemented. As indicated in Figure 9, the vast majority of respondents recognize the necessity of employing multiple-input multiple-output (MIMO) impedance matrices, rather than single-input singleoutput (SISO) impedance transfer functions, for the accurate stability assessment in both αβ or dq frame [6]. While most respondents express confidence in the effectiveness of impedance-based method, industry respondents exhibit lower levels of confidence compared to their academic counterparts (see Figure 3). This disparity may be attributed to the fact that industries tend to encounter more complex electrical systems, which increases the likelihood of divergence between impedance-based predictions and EMT simulations/field measurements results.

B. Challenges for the Industry Based on the response of Q3 and Q4 (Figures 4 and 5), both the unique and common challenges faced by TSOs/power plant developers and IBR vendors in implementing impedance-based dynamic analysis are summarized as follows: Unique Challenges for TSOs/Power Plant Developers: It can be seen from Figure 4 that the lack of the automated impedance measurement toolbox is one of most significant challenges for TSOs/power plant developers. The impedance measurement tools have been developed, both in simulation software and hardware, for measuring impedances of single or a few IBRs [7], [8], [9], [10]. However, TSOs/power plant developers are dealing with large and complex electrical systems that may include thousands of IBRs, which

imposes more stringent requirements on the time efficiency of the automated impedance measurement tools. A recent attempt can be found from Aalborg University and TenneT TSO that has developed the impedance measurement toolbox and tested in a multi-terminal HVDC system [8], as shown in Figure 14. National Renewable Energy Laboratory (NREL) [9] as well as Electric Reliability Council of Texas (ERCOT) [10] have also developed similar toolboxes that are tested in wind power plants. Yet, more efforts are still expected to further improve the computational efficiency and accuracy. Figure 4 indicates another challenge for TSOs/power plant developers, which is the difficulty of verifying the accuracy of the impedance measurement. This challenge arises because TSOs/power plant developers work with black-boxed simulation models of IBRs, as the IBR vendors cannot disclose the control algorithms of IBRs due to intellectual property (IP) concerns. Consequently, TSOs/power plant developers cannot theoretically derive the impedance models to check with the measured results. A few TSOs/ power plant developers have asked IBR vendors to provide black-boxed, theoretically-derived impedance models for cross-validation with the measured impedances [11]. However, this requires IBR vendors to have adequate expertise in impedance modeling of IBRs, and hence, it is still not a common practice at the current stage. Unique Challenges for IBR Vendors: Based on Figure 5, the lack of impedance specifications poses a significant challenge for IBR vendors. Given the fact that the impedance matrix of IBR can be simplified to a SISO form in the high-frequency range, its real part is required to be non-negative by some grid codes for the guarantee of high-frequency stability [12]. However, there are currently no specifications for impedance matrix of IBR in the low-frequency range, where its original MIMO form

FIG 14 Graphical user interface (GUI) and part of test results of the impedance measurement toolbox developed in [8].



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should be adopted for stability assessment. This is mainly due to the absence of a straightforward link between the low-frequency stability margin and the dynamic properties of impedance matrix, which makes it difficult to establish the impedance specifications. Moreover, the missing of such a direct link also poses a challenge for IBR vendors in obtaining analytical insights into controller design from the impedance-based dynamic analysis, as indicated by Figure 5. Common Challenges: It can be seen from Figures 4 and 5 that TSOs/power plant developers and IBR vendors have expressed their concerns in using impedance-based dynamic analysis for multi-IBR systems. This concern can be further broken down into two questions: 1) how to

aggregate impedance models of IBRs and 2) how to deal with multiple operating points of a complex electrical system, which are indicated by Q11–Q12. The industry’s responses to the former question, as given by Figure 12(b), suggest that they are skeptical to the capability of aggregated impedance model of multiple IBRs in reflecting the control interactions therein. Further, their response to the latter question reflects a lack of an appropriate method for dealing with multiple operating points, i.e., they either attempt to cover as many operating points as possible, or select multiple operating points based on practical experiences or operational guidelines but are not sure if the selected operating points can cover the worst-case scenarios, as illustrated in Figure 13(b).

FIG 15 Open issues with impedance-based dynamics analysis methods.

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C. Gap Between Academia and Industry It is quite interesting to see from Figures 12 and 13 that academia and industry hold quite different opinions on impedance-based dynamic analysis for multi-IBR systems. By comparing Figure 12(a) and (b), it is found out that although both groups acknowledged that the control interactions of IBRs is the primary cause of inaccuracy of the aggregated impedance model, academia additionally identifies different operating points of individual IBRs as an important contributor, while industry attributes the inaccuracy to different controller and circuit parameters. This disparity may stem from the fact that academia often examines homogeneous multi-IBR systems, where IBRs have identical controller and circuit parameters, and thus fails to capture the impact of heterogeneous IBRs on the accuracy of impedance aggregation. Moreover, Figure 13(a) indicates that around 30% of academic researchers are confident to cover the worst-case scenarios by following certain guidelines, whereas this confidence is not agreed by the industry, as indicated in Figure 13(b). In a nutshell, the results of Figures 12 and 13 clearly indicate the gap between understandings of academia and industry on the challenges of using impedance-based method, and highlight the importance of academia-industry collaboration in developing effective impedance aggregation methods for multi-IBR systems.

Future Development of Impedance-Based Dynamic Analysis Based on the challenges identified in Section “Key Results and Analysis,” and the response to Q5, several open issues with the impedance-based analysis method are summarized as follows, which are also outlined in Figure 15. Addressing these issues require collaborative research and development efforts of academia and industry. 1) Dynamic Specifications for MIMO Impedance Matrix: Control theories that can link dynamic properties of MIMO impedance matrix to low-frequency stability margin, as well as linking the characteristics of each element of impedance matrix to specific controllers need to be developed. Such links would not only aid TSOs/power plant developers in developing clear specifications and requirements on the impedance matrix of IBRs, but also offer insights for IBR vendors in shaping control dynamics of IBRs. 2) Impedance Measurement Toolbox: An automated impedance measurement toolbox with high measuring accuracy and high time efficiency should be developed and tested in large and complex electrical systems. 3) Impedance-Based Analysis of Multi-IBR System: A solid theoretical framework of implementing impedance-based dynamic analysis should be developed for heterogeneous multi-IBR systems in complex electrical networks. This framework should be able to accurately



aggregate impedance models of IBRs and address the challenges related to multiple operating points.

Conclusion and Future Action The results of the survey on impedance-based dynamics analysis method have identified gaps and challenges faced by different stakeholders, based on which, several emerging topics in this direction are summarized. In the future, IEEE Task Force on Frequency-Domain Modeling and Dynamic Analysis of HVDC and FACTS will organize more technical activities to facilitate the collaborations between academia and industry in addressing the challenges, which can hopefully advance the technology for stability analysis of future power systems.

About the Authors Heng Wu ([email protected]) is an Assistant Professor with the Department of Energy, Aalborg University, Denmark. Fangzhou Zhao ([email protected]) is an Assistant Professor with the Department of Energy, Aalborg University, Denmark. Xiongfei Wang ([email protected]) is a Professor with the Division of Electric Power and Energy Systems, KTH Royal Institute of Technology, Sweden, and a part-time Professor with the Department of Energy, Aalborg University, Denmark.

References

[1] C. Buchhagen et al., “Harmonic stability—Practical experience of a TSO,” in Proc. Wind Integr. Workshop, 2016, pp. 1–6. [2] X. Wang and F. Blaabjerg, “Harmonic stability in power electronic-based power systems: Concept, modeling, and analysis,” IEEE Trans. Smart Grid, vol. 10, no. 3, pp. 2858–2870, May 2019. [3] L. Harnefors, M. Bongiorno, and S. Lundberg, “Input-admittance calculation and shaping for controlled voltage-source converters,” IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 3323–3334, Dec. 2007. [4] J. Sun, “Impedance-based stability criterion for grid-connected inverters,” IEEE Trans. Power Electron., vol. 26, no. 11, pp. 3075–3078, Nov. 2011. [5] B. Wen et al., “Analysis of D-Q small-signal impedance of grid-tied inverters,” IEEE Trans. Power Electron., vol. 31, no. 1, pp. 675–687, Jan. 2016. [6] X. Wang, L. Harnefors, and F. Blaabjerg, “Unified impedance model of grid-connected voltage-source converters,” IEEE Trans. Power Electron., vol. 33, no. 2, pp. 1775–1787, Feb. 2018. [7] Z. Shen, “Online measurement of three-phase AC power system impedance in synchronous coordinates,” Ph.D. dissertation, Dept. Elect. Eng., Virginia Tech, Blacksburg, VA, USA, 2012. [8] H. Wu et al., “Development of the toolbox for AC/DC impedance matrix measurement of MTDC system,” in Proc. 20th Wind Integr. Workshop, 2021, pp. 442–448. [9] S. Shah et al., “Sequence impedance measurement of utility-scale wind turbines and inverters—Reference frame, frequency coupling, and MIMO/ SISO forms,” IEEE Trans. Energy Convers., vol. 37, no. 1, pp. 75–86, Mar. 2022. [10] X. Wang et al., “A Python based automatic impedance scan tool for PSCAD models,” in Proc. IEEE Power Energy Soc. Gen. Meeting (PESGM), Denver, CO, USA, Jul. 2022, pp. 1–5. [11] D. Ramasubramanian et al., “Asking for fast terminal voltage control in grid following plants could provide benefits of grid forming behavior,” IET Gener., Transmiss. Distrib., vol. 17, no. 2, pp. 411–426, Jan. 2023. [12] M. Aeberhard, M. Meyer, and C. Courtois, “The new standard EN 50388–2. Part 2—Stability and harmonics,” Elektrische Bahnen, vol. 12, no. 1, pp. 28–35, 2014. 

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Future Directions of Commercially Available Supercapacitors Compared With Rechargeable Batteries for Renewable Energy Applications by Nadee Arawwawala, Nihal Kularatna, and Don Charles Uvindra Sirimanne

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E

nergy storage devices (ESDs) have become an essential component in renewable energy systems for higher reliability, given the fluctuating nature of renewable energy sources such as solar, wind, and biomass. Thus, various types of ESDs have been invented over the past years, and rechargeable batteries play an increasingly vital role in storing energy in response to the fluctuating nature of the renewable sources and increasing demand for reliable renewable energy sources. ESD options for longer-term and infrequent utilization can be listed primarily as below [1]: ■■Rechargeable batteries ■■SC banks ■■Flywheels ■■Thermal energy storage system ■■Fuel cells ■■Compressed air energy storage system ■■Superconductive Magnetic Energy Storage (SMES) ■■Pumped hydro-storage In this review article, mainly the lithium based rechargeable battery technologies and supercapacitors have been investigated and compared.

II. Supercapacitor Structure Supercapacitors do not rely on chemical reactions like batteries and instead, they store potential energy electrostatically. They have bigger electrode plates with less distance between them and those plates are coated with a porous substance such as powdery activated charcoal and are soaked in an electrolyte separated by a very thin insulating material to separate the collection of positive and negative charges forming on each side’s plates. Figure 3 shows the practical formation of a supercapacitor and the two separate series capacitors formed inside due to the electrical double layer. This allows the device to store and release energy efficiently and store the static electricity for later use [2], [5].

I. Li-ion Battery and Supercapacitor: Structural Comparison Lithium-ion (Li-ion) batteries totally rely on chemical reactions where submerging the positive side and the negative side in a liquid electrolyte solution and separating them using a micro-perforated separator, allowing only ions to pass through [3]. Since, lithium is extremely reactive in its elemental form, generally in a lithium-ion battery, lithium metal oxide such as lithiumcobalt oxide (LiCoO2) is used in the cathode and lithium-carbon compounds are used in the anode as those materials allow intercalation letting the electrodes to have easy lithium-ions movement in and out of their structures [2]. Figure 1 depicts the structure of a Li-ion cell. At the cathode, from the half-reaction of reduction, LiCoO2 is formed and at the anode, and from the half-reaction of oxidation, graphite (C6) and lithium ions are formed as depicted below.

FIG 1 Structure of a Li-ion battery [2].

FIG 2 Li-ion battery charging and discharging processes [27], [28].

Reduction(cathode) CoO2 + Li+ + e− → LiCoO2 (1) Oxidation (anode)  LiC6 → C6 + Li+ + e−(2) Then, the full reaction (left to right = discharging, right to left = charging) is given by:

LiC6 + CoO2 → ← C6 + LiCoO2

(3)

Reduction always takes place at the cathode and oxidation always occur at the anode. But the anode and cathode change during the charging and discharging process of the battery and can be illustrated as depicted in Figure 2 [27], [28].

FIG 3 Structure of a supercapacitor and the formation of two series capacitors inside [3].

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When a voltage is applied across the SC, an “electrical double layer” is created, and it aligns and store both negative and positive charges along the boundaries of electrodes and the electrolytic solution as depicted in Figure 4 [6].

III. Comparison of Energy Density Versus Power Density As shown in Ragone plot in Figure 5, we see batteries and fuel cells get placed at the top left hand corner. Compared to this high energy density with low power density, all supercapacitor families get placed in the center indicating relatively high-power density and with lower energy density. Electrolytic capacitors with extra low energy capability stays within the lower right-hand corner. Today, there are several variations of supercapacitors (SC) available and Table 1 provides a comparison of the typical energy density and power density values of different SC types and rechargeable lithium-ion batteries. In general, when a battery pack is used due to its high energy density the ESS (battery pack) allows us to buffer any fluctuations in the energy supply such as a renewable energy input. Under such a situation, MPPT system matches the input resistance of the energy source, such as solar array to the input resistance of the battery pack, plus the load combination modified by the high frequency dc–dc converter. However, moment we replace the battery

FIG 4 Charging and discharging process of a supercapacitor [6].

Table –– 1. Energy and power density comparison [1]. Symmetrical SCs

Hybrid SC

Capabatteries

Li-Ion

Energy density (Wh/kg)

3–8

7–14

50–120

250–670

Power density (W/kg)

8,000

2,500– 4,000

1,600– 3,200

375– 1,750

pack with a supercapacitor bank, it is necessary to match a capacitor on the load side to the impedance of the solar array, which becomes a theoretical impossibility. This issue is not much discussed in published literature.

Recent Developments of Li-ion Battery Variations and SC Types A. Basic Types of Li-Battery Technologies ■■Lithium

cobalt oxide/Lithium-ion cobalt (Li-ion) Commonly known as Li-ion, this most popular rechargeable battery type for portable applications comes with the highest energy density at room temperature, with a single cell nominal voltage of approximately 3.6 V [7], [22]. ■■Lithium manganese oxide This battery type was initially invented in the 1980s and was first published in the Materials Research Bulletin in 1983. Then in 1996, Moli Energy manufactured and commercialized the first Li-ion cell using lithium manganese oxide as the cathode material. These batteries are sometimes known as lithium manganate or lithium-ion manganese batteries, or li-manganese or manganese spinel batteries [7]. ■■Lithium iron phosphate (LiFePO4) This battery was first discovered by the University of Texas (and other contributors) in 1996 by using phosphate as the cathode material for rechargeable lithium batteries. Lithium-phosphate batteries provide good electrochemical performance with low internal resistance featuring enhanced thermal stability and safety. ■■Lithium nickel manganese cobalt oxide (LiNiMnCoO2)/NMC This is considered as one of the most successful Li-ion technology which has the cathode constructed using a mix of nickel, manganese, and cobalt materials.

B. Future Li Batteries ■■Solid-state

FIG 5 Ragone plot [1].

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Li-ion battery This battery is based on a solid metal electrode and a solid based electrolyte. Because of the solid-state, this battery is safer and more stable than the present battery types as the design prevents leakage and corrosion at the electrodes [13], [30]. Table 2 given below provides a comparison of the commercially available types of Li batteries [7], [8].

–– Table 2. Comparing commercially available types of Li batteries [7], [8].

Lithium Battery Type Voltages(V) Cycle life (cycles) Energy-density (Wh/kg)

Lithium Cobalt Oxide

Lithium Manganese Oxide

Lithium Iron Phosphate

LiNiMnCoO2

3.6

3.7

3.2–3.3

3.6

1,000–1,200

300–700

2,000

1,000–2,000

150–250

100–150

90–120

150–220

■■Lithium-sulfur

batteries This type of battery uses lithium metal as the anode, sulfur composite as the cathode and an organic liquid as the electrolyte. Li-sulfur batteries offer high energy densities with low manufacturing costs and are suitable for applications such as EVs, portable devices etc. [14].

Both these charge storage mechanisms are only distinguishable using their measurement techniques. Even though the magnitude of capacitance of each storage principle can be heavily varied, the amount of charge stored per unit voltage in an electrochemical capacitor mainly depends on the size of its electrode.

C. Supercapacitor Electro-Chemistry and Basic Mechanisms

D. Current Commercial Variations of SCs Based on the Recently Developed Mechanisms

In an electrochemical capacitor, though the double-layer effect is used to store electric energy, it doesn’t have a conventional fixed dielectric material to separate the charges and the charge is accumulated in the interface between active electrodes and the electrolyte. Two basic mechanisms of charge storage that support the total capacitance of an electrochemical capacitor are 1) electrostatic charge storage and 2) pseudo-capacitance. Figures 6 and 7 show the difference. ■■Electrostatic charge storage This mechanism is basically a physical non-faradic process that distributes and stores charges on surfaces by separating them in charge traps named Helmholtz double-layer [9], [10]. ■■Pseudo-capacitance This mechanism is basically an electrochemical process that involves faradaic redox reactions with the transfer of charge between electrode and electrolyte [10].

Based on the recent research and developments, there are three main types of commercially available supercapacitors, such as the electrochemical double-layer capacitors (EDLC), which use the non-faradic mechanism, pseudocapacitors, which use the faradic process, and hybrid capacitors, which are using a combination of the two processes and can be categorized as depicted in Figure 8. ■■Electric double-layer capacitors EDLC type supercapacitors are basically constructed using two carbon-based electrodes, an electrolyte, and a separator and use the non-faradic process discussed above in Section C. So, they do not transfer charge between electrode and electrolyte and use an electrochemical double-layer of charge for energy storage. When a voltage is applied, charge accumulates on the electrode surfaces and the ions in the electrolyte solution diffuse across the separator into the pores of the electrode of opposite charge. The electrodes are engineered to prevent

FIG 6 Electrostatic charge storage [9].

FIG 7 Pseudo-capacitance electrochemical charge storage [9].



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the recombination of the ions. Consequently, a double layer with two layers of charges is produced at each electrode. These layers are coupled with an increase in surface area and a decrease in the distance between electrodes, allowing EDLCs to increase capacitance and achieve higher energy densities [10]. Since this is a non-faradic process with no chemical reaction, EDLCs have a highly reversible charge storing ability allowing them to achieve high cycling rates because of their cycling stability. So, this type of SC is great for general applications, replacing rechargeable batteries and also for non-user serviceable areas such as deep-sea or mountains because of their high cycle rates. By changing the nature of the electrolytes, the characteristics of these SCs can be adjusted and the electrolyte for an EDLC can be selected from either an aqueous or organic material. Compared to organic material such as acetonitrile, aqueous electrolytes, non-organics such as H2SO4 and KOH typically have lower ESR values and lower minimum pore size requirements. However, they offer lower breakdown voltages and thus, when selecting the material for electrolyte, the trade-offs between capacitance, ESR, and voltage should be considered and hence the selection of electrolyte mostly depends on the requirements of the application [10]. Sub-categories of EDLC types are characterized primarily using carbon as the electrode material as they are typically having a higher surface area, lower cost, and welldeveloped fabrication methods than other materials, such as conducting polymers and metal oxide [10]. Therefore, the electrodes of EDLCs are made using various forms of

FIG 8 Categorization of SC families [10].

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carbon materials and the sub-categories of current EDLCs which are commercially available can be found as activated carbons, carbon aerogels, and carbon nanotubes based EDLCs [10].

Commercially Available Supercapacitors Versus Li-Battery Performance Comparison We have collected samples of several different supercapacitors from Samwha Electric, Korea [11] for comparison. Based on publicly available construction details from Samwha, the differences in construction are presented below. ■■Standard type activated carbon EDLC consists of active carbon electrodes and an organic solvent. ■■High-temperature type activated carbon EDLC consists of active carbon electrodes and an organic solvent. ■■LMO type asymmetric hybrid utilizes lithium manganese oxide electrode and an activated carbon electrode. ■■LTO type asymmetric hybrid utilizes lithium titanium oxide electrode and an activated carbon electrode. ■■High-energy battery type utilizes the negative LTO electrode and the positive Li transition metal oxide electrode and offers a high-power density of over 1 kW/kg and a high energy density of over 110 Wh/L. ■■High-power battery type utilizes the negative LTO electrode and the positive Li transition metal oxide electrode and offers a high-power density of over 1.7 kW/kg and a high energy density of over 65 Wh/L. Table 3 compares the engineering specifications of these commercial types of supercapacitors and Li-ion battery. Table 4 compares the temperature capability, cycle life, and shelf life, etc., of different types of supercapacitor families.

Table –– 3. Performance comparison of commercially available supercapacitor types and Li-ion battery [1], [11]. Device type

Voltage (V)

Capacitance/ mAh capability

ESR (mΩ)

Weight (g)

Energy-density (Wh/kg)

Power-density (Wh/kg)

Standard EDLC

2.7

3,000 F 2,200 mAh

0.29

525

5.7

11,970

High-temp. EDLC

2.5

3,000 F 2,000 mAh

0.3

525

4.9

9,921

LMO hybrid

2.7

6,000 F 2,600 mAh

0.7

670

8

3,886

LTO hybrid

2.8

7,500 F 2,800 mAh

0.8

560

9.8

4,375

High-energy battery type

2.7

70,000 F 19,000 mAh

1.1

810

56.7

2,045

High-power battery type

2.7

40,000 F 12,000 mAh

0.7

710

37

3,667

Li-ion battery

3.7

2,600 mAh

55

50

192

1,245

Table –– 4. Comparing temperature range, cyclic life, and energy/power density of different SC families. SC type

Standard EDLC

High-temp. EDLC

LMO hybrid

LTO hybrid

High-energy battery type

High-power battery type 2.7 V dc [2.8 V]

Rated Voltage (V)

2.7 V dc [2.8 V]

2.5 V dc [2.6 V]

2.7 V dc [2.8 V]

2.7 V dc [2.8 V]

2.7 V dc [2.8 V]

Temp. range (°C)

−20 to 60

−40 to 80

−20 to 50

−20 to 40

−20 to 50

−20 to 50

Cycle life (25 °C)

1,000,000 cycles

500,000 cycles

15,000 cycles

20,000 cycles

Shelf-life

After 1,000 hrs no-load test same as endurance (2.7 V:60 °C)

40,000–50,000 cycles After 1,000 hrs no-load test same as endurance

Energy-density (Wh/kg)

>5 ~ 8

10 ~ 14

50 ~ 120

Power-density (Wh/kg)

>8,000

2,500 ~ 4,000

1,600 ~ 3,200

Ragone plot shown in Figure 5 compares various energy storage device families in general. In the following section, we calculate the energy density and power density of the device families we detailed in Tables 4 and 5, creating a detailed Ragone plot to compare their relative performance. For the Ragone plot analysis, the energy density and the power density of a device are calculated using the following formulas. Energy density Rated Ah capability ( Ah ) * Nominal DC voltage ( V ) = (4) Weight or volume of the packaged device The maximum power capability is estimated by the following relationship considering the maximum power delivery criteria occurring where the ESR is equal to the load resistance [9], [17]. Maximum power capability ( Pmax ) =

After 1,000 hrs no-load test same as endurance

V2 (5) 4 * ESR

Then the power density is estimated by, Power density =

(6) Pmax Weight or volume of the packaged device

Figure 9, is a specifically created Ragone plot based on the above relationships, to compare Li-ion batteries and different SC types, using datasheet values available for the SC devices from Samwha [11].

Combined SC and Batteries in Hybrid Energy Storage Systems (HESS) As Table 4 indicates, supercapacitors have the specific advantage of very high power density, which is the opposite case for Li-ion batteries. Given this situation, hybridization of batteries and SCs helps to overcome the limitations of SCs or batteries as they have power or energy restrictions when taken individually. Thus, such hybrid systems are vital for applications that require both September 2023

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Table 5. Price per Farad cost [30].

EDLC SC Snap in type

EDLC SC Axial type

Battery-cap Snap in type

Battery-cap Axial type

Capacitance (F)

Price ($)

Price per Farad (NZ $ cents)

100

3.7

3.7

200

6.79

3.4

400

10.49

2.62

1,200

30.86

2.57

electric vehicles tend to degrade mostly due to the high peak power and harsh charging/discharging cycles involved during the process of braking and acceleration. Since supercapacitors have the advantage of high-power density, they have the ability to handle an instantaneous impulse EV load and, thereby, they can reduce the stress applied to the battery and also increase the high-rate current demand [15].

2,000

40.74

2.04

B. Short-Term Power Capability From SC Bank

3,000

55.56

1.85

1,500

3.7

0.25

3,300

7.41

0.22

As most supercapacitor families come with lower energy density in general, they cannot be used as the sole power source for applications such as electric vehicles [12]. However, they have the ability to deliver and absorb huge transient pulse power, during sudden acceleration and braking conditions. So, this permits the hybrid energy storage systems to meet the peak power requirement for a short period of time using SCs and the average power delivery requirement for a long period of time using the batteries [15].

6,500

12.35

0.19

9,000

17.28

0.19

9,500

43.21

0.45

20,000

54.32

0.27

33,000

74.07

0.22

70,000

98.77

0.14

C. Usage of Converters in a Hybrid System high power and high energy densities, such as multifunctional electronic equipment, electric vehicles and industrial types of equipment [11].

Since it is essential for electric vehicles to have a highpower density as well as a high energy density, they need to use multiple energy sources and energy storage devices such as batteries, fuel cells (FC), and ultracapacitors or SCs to fulfil those requirements.

A. Life Cycle Extension of a Hybrid Pack The main reason for adopting hybrid systems is to lengthen the life cycle of lithium batteries as the costs involved with replacing the battery packs can be reduced by avoiding replacements during the life of the system powered by the hybrid device [18]. Batteries used in

D. Unique Applications of Supercapacitors in Power Electronic Building Blocks Compared to these straightforward cases of supercapacitors replacing batteries or building battery supercapacitor hybrids, today there is new research related to

FIG 9 Ragone plot based comparison of commercially available supercapacitors with Li-ion battery performance.

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supercapacitor assisted (SCA) techniques where the longtime constant property of a supercapacitor based circuit is creatively utilized. These SCA techniques summarised in [1] are applied to extra low frequency dc–dc converters and transient protection systems. These systems are based on a new theoretical concept now known as supercapacitor assisted loss management (SCALoM) System [29].

Longer-Term Possibility of SC Replacing Li-Batteries Based on Effective Long-Term Capital Cost Table 5 shows a price per Farad analysis of commercially available SCs from Samwha-Korea. As we see from this, larger capacitors are more economical in terms of price per Farad in general. When we consider using the newer families such as battery capacitors, which comes with a penalty of shorter life cycles, they are much cheaper to use. Table 6 illustrates the possibility of achieving a longerterm capital cost-benefit by using SCs to replace rechargeable batteries. As per details in Table 6, similar volume battery capacitors are cheaper than Li-ion cells, based on their device cost. Once you consider the (at least) 15 times longer life of battery capacitors, they become significantly cheaper in terms of cost per 1,000 cycles of use. In the case of the hybridized form of an energy source of SC-battery pair, much more overall life within the cost margins may

be achieved. This discussion is beyond the scope of this review article.

Future Directions of Carbon-Based SC Material Since supercapacitors have become one of the arising innovations of energy storage devices, scientists and researchers are keeping busy exploring ways to increase the functionality of the electrode type or seeking suitable electrolyte materials for supercapacitors to achieve high power densities as well as high energy densities. Even though it is challenging for them to find proper electrode material or electrolyte for the SC development process, two dimensional (2D) nanomaterials such as quasi-graphene, MXene and transition metal dichalcogenides are highly considered for SCs because of their exceptional physical and chemical behavior letting them possess outstanding mechanical and electrical properties, as well the benefit of high surface area [16]. Carbon-based 2D nanomaterials such as graphene, Mxenes and activated carbons store energy primarily using the mechanism of double-layer charge storage. But, they also use the pseudocapacitive mechanism when it has been doped with appropriate materials or functioning chemically. And the other 2D nanomaterial type of inorganic 2D nanomaterials, such as 2D metal oxide, transition metal dichalcogenides (TMD), and transition metal carbide (TMC) use the redox-ion intercalation pseudocapacitive behaviors [16].

Conclusion Table 6. Longer term cost-comparison of SCs with Li-ion batteries with similar capacities [30], [31]. ––

Device type



Capacity Voltage mAh rating

Price per device ($)

Cycle- Price for life 1,000 cycles ($)

1,500 F battery cap

600

2.7

3.7

15,000

0.25

3,300 F battery cap

1,100

2.7

7.41

15,000

0.49

6,500 F battery cap

2,200

2.7

12.35

15,000

0.82

9,500 F battery cap

3,300

2.7

43.21

15,000

2.88

4,500 Li-ion

1,200

3.7

12.24

1,000

12.24

14,500 Li-Ion

800

3.7

11.9

1,000

11.9

18,650 Li-ion

2,600

3.7

18.9

1,000

18.9

26,650 CA Liion

3,400

3.7

31

1,000

31

This work indicates that the current progress of the newer commercial supercapacitor families, such as hybrid types are gradually moving towards the properties of high energy Li-ion battery chemistries, but without seriously compromising the cycle life. As summarized by the list of references, we see that lot of new commercialization happening on the devices while new and unique applications beyond battery replacements are also achieved. Battery-capacitors are a new commercial family, which has reached the energy density of lead-acid batteries, but maintaining their life cycle count still adequate-enough to use them as fit-and-forget devices in consumer electronics, industrial electronics and transportation area. More research on hybridization may lead to better overall energy storage systems, compared to lone Li-ion battery chemistry. We are looking forward to interesting developments in the next five years.

Acknowledgment This research received funding support provided via the Future Architecture Network (FAN) Project of the Advanced Energy Technology Program (AETP) of the Ministry of Business, Innovation and Employment, New Zealand.

About the Authors Nadee Arawwawala ([email protected]) received the B.Eng. degree in digital communications and electronics engineering from the University of Hertfordshire, U.K., where she received the M.Sc. degree in September 2023

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embedded intelligent systems engineering, in 2014. More recently, she was working on applications for renewable energy systems with the University of Waikato, Hamilton 3240, New Zealand. She is currently working as a Software Engineer with the energy distribution company WEL Networks Ltd. Nihal Kularatna ([email protected]) is actively researching supercapacitor applications and power electronics. He has authored ten reference books and research monographs, and contributed over 175 publications. He won the Post Graduate Research Supervision Excellence Award (2021) from the University of Waikato, Hamilton 3240, New Zealand, where he is employed as an Associate Professor. He won the NZ Engineering Innovator of the Year 2013 award for developing SCA techniques. He received the D.Sc. degree in 2015. Prior to moving to academia in New Zealand, he was the CEO of Arthur C. Clarke Institute in Sri Lanka. Don Charles Uvindra Sirimanne (ds213@students. waikato.ac.nz) received the B.Sc. degree in mechanical engineering from the University of Arizona, USA, and the M.Eng. degree in electrical and electronic engineering from the University of Waikato, Hamilton 3240, New Zealand, in 2022. He is undertaking research in supercapacitor applications and power electronics.

References

[1] N. Kularatna and K. Gunawardane, Energy Storage Devices for Renewable Energy-Based Systems: Rechargeable Batteries and Supercapacitors, 2nd ed. San Diego, CA, USA: Elsevier, May 2021. [2] B. Chapman. (Sep. 23, 2019). How Does a Lithium-Ion Battery Work? Let’s Talk Science. Accessed: Mar. 8, 2021. [Online]. Available: https://letstalkscience.ca/educational-resources/stem-in-context/how-does-a-lithiumion-battery-work [3] FutureBridge. Supercapacitors—A Viable Alternative to Lithium-Ion Battery Technology? Accessed: Mar. 8, 2021. [Online]. Available: https:// www.futurebridge.com/industry/perspectives-mobility/supercapacitors-aviable-alternative-to-lithium-ion-battery-technology/ [4] J. T. Warner, Lithium-Ion Battery Chemistries. Amsterdam, The Netherlands: Elsevier, 2019, doi: 10.1016/C2017-0-02140-7. [5] S. Martin. (May 2, 2017). What is the Difference Between a Battery and a Supercapacitor? Aerospace. Accessed: Mar. 8, 2021. [Online]. Available: https://electronics360.globalspec.com/article/8580/what-is-the-differencebetween-a-battery-and-a-supercapacitor [6] N. Raghvendra. What is Supercapacitor (Ultracapacitor)—Characteristics, Working, Types & Applications. Accessed: Mar. 8, 2021. [Online]. Available: https://electricalfundablog.com/supercapacitor-ultracapacitorcharacteristics-working/ [7] Types of Lithium-Ion Batteries Available in the Market, Inverted. Accessed: Mar. 8, 2021. [Online]. Available: https://inverted.in/blog/types-oflithium-ion-batteries-available-in-the-market [8] Battery University. BU-205: Types of Lithium-Ion. Accessed: Mar. 8, 2021. [Online]. Available: https://batteryuniversity.com/article/bu-205-typesof-lithium-ion [9] (Feb. 8, 2022). Supercapacitors, Passive-Components. Accessed: Mar. 8, 2021. [Online]. Available: https://passive-components.eu/supercapacitors/ [10] M. S. Halper and J. C. Ellenbogen. (Mar. 2006). Supercapacitors: A Brief Overview. Accessed: Mar. 8, 2021. [Online]. Available: http://www.mitre.org/ sites/default/files/pdf/06_0667.pdf [11] ESD-SCAP. Samwha Capacitor Brochure. Accessed: Feb. 5, 2022. [Online]. Available: http://samwha20.cafe24.com/samwha_eng/ [12] J. Kathi and N. Kadalis. Battery-Supercapacitor Hybrid Energy Storage Systems. Accessed: Mar. 9, 2021. [Online]. Available: https://www.patent-art.

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com/jp/knowledge-center/battery-supercapacitor-hybrid-energy-storagesystems-in-electric-vehicles/ [13] C. Hall. (Mar. 22, 2021). Future Batteries, Coming Soon: Charge in Seconds, Last Months and Power Over the Air. Accessed: Mar. 9, 2021. [Online]. Available: https://www.pocket-lint.com/gadgets/news/130380future-batteries-coming-soon-charge-in-seconds-last-months-and-powerover-the-air [14] M. Li, C. J. Jafta, and I. Belharouak, “Progress of nanotechnology for lithium-sulfur batteries,” Frontiers Nanosci., vol. 19, pp. 137–164, Jan. 2021. [15] A. Kachhwaha et al., “Design and performance analysis of hybrid battery and ultracapacitor energy storage system for electrical vehicle active power management,” Sustainability, vol. 14, no. 2, p. 776, 2022, doi: 10.3390/ su14020776. [16] B. Raj et al., “Futuristic direction for R&D challenges to develop 2D advanced materials based supercapacitors,” J. Electrochem. Soc., vol. 167, Sep. 2020, Art. no. 136501. [17] R. Vicentini et al., “How to measure and calculate equivalent series resistance of electric double-layer capacitors,” Molecules, vol. 24, no. 8, p. 1452, Apr. 2019. [18] Z. Songab et al., “The battery-supercapacitor hybrid energy storage system in electric vehicle applications: A case study,” Energy, vol. 154, pp. 433–441, Jul. 2018. [19] S. Zhang and N. Pan, “Advanced energy materials supercapacitor performance evaluation,’’ UC Davis Previously Published Works, Tech. Rep. aenm.201401401R1, 2014. [Online]. Available: https://escholarship.org/ content/qt5ps0k488/qt5ps0k488.pdf, doi: 10.1002/aenm.201401401. [20] A. Burke and J. Zhao, “Supercapacitors in micro- and mild hybrids with lithium titanate oxide batteries: Vehicle simulations and laboratory tests,’’ UC Davis Inst. Transp. Stud., Davis, CA, USA, Tech. Rep. UCD-ITS-RR-15-20, 2015. [Online]. Available: https://itspubs.ucdavis.edu/publication_detail. php?id=2553 [21] A. Burke, “Testing of supercapacitors: Capacitance, resistance, and energy energy and power capacity,” UC Davis Inst. Transp. Stud., Davis, CA, USA, Tech. Rep. UCD-ITS-RR-09-19, 2009. [Online]. Available: https://itspubs. ucdavis.edu/publication_detail.php?id=1308 [22] H. Zhao and B. Hengbing, “Fuel cell powered vehicles using supercapacitors: Device characteristics, control strategies, and simulation results,” UC Davis Inst. Transp. Stud., Davis, CA, USA, Tech. Rep. fuce.200900214, 2010, doi: 10.1002/fuce.200900214 [23] A. Burke and M. Andy, “Electrochemical capacitors as energy storage in hybrid-electric vehicles: Present status and future prospects,” UC Davis Inst. Transp. Stud., Davis, CA, USA, Tech. Rep. UCD-ITS-RR-09-07, 2009. [Online]. Available: https://itspubs.ucdavis.edu/publication_detail.php?id=1291 [24] J. M. Miller, “Energy storage technology markets and application’s: Ultracapacitors in combination with lithium-ion,” in Proc. 7th Int. Conf. Power Electron. (ICPE), Nov. 2007, pp. 16–22. [25] J. M. Miller and G. Sartorelli, “Battery and ultracapacitor combinations,’’ in Proc. IEEE Vehicle Power Propuls. Conf., Lille, France, Oct. 2010. [Online]. Available: https://www.researchgate.net/publication/224224218_ Battery_and_ultracapacitor_combinations_-_Where_should_the_converter_ go, doi: 10.1109/VPPC.2010.5729216. [26] J. M. Miller and J. Auer, “Battery-ultracapacitor combinations: Sizing up the benefits,” Tech. Rep. [Online]. Available: https://www.researchgate.net/ publication/242466237_Battery-Ultracapacitor_Combinations_Sizing_up_ the_Benefits [27] M. Mancini, “Improved anodic materials for lithium-ion batteries: Surface modification by metal deposition and electrochemical characterization of oxidized graphite and titanium dioxide electrodes,” Ph.D. thesis, Dept. Chem., Camerino Univ., Camerino, Italy, 2008. [28] N. Omar et al., “Rechargeable energy storage systems for plug-in hybrid electric vehicles—Assessment of electrical characteristics,” Energies, vol. 5, no. 8, pp. 2952–2988, 2012. [29] N. Kularatna et al., “Supercapacitor-assisted techniques and supercapacitor-assisted loss management concept: New design approaches to change the roadmap of power conversion systems,” Electronics, vol. 10, no. 14, p. 1697, 2021, doi: 10.3390/electronics10141697. [30] Samwha Energy Storage Capacitors. Accessed: Feb. 3, 2022. [Online]. Available: http://www.samwha.com/capacitor/news/news_product5.aspx [31] Jaycar. Accessed: Feb. 3, 2022. [Online]. Available: https:// www.jaycar.co.nz/power-batteries/rechargeable-batteries/li-ion-lipo/c/0AB?sort=popularity-desc&q 

From “Power Electronics Inside” to “HumanCentered Power Electronics” by Harish Sarma Krishnamoorthy, Philip Krein, and Brian Zahnstecher

A

n early mantra of our field was “power electronics inside,” a take on a popular tagline from a major electronics company. Power electronics continues to be an infrastructure and internal technology—throughout the grid, integral to our computers and devices, essential in motor drives, embedded in our cars and appliances, actively managing renewable energy systems, and performing an unlimited range of vital functions. Even though power electronics may not be familiar to the average person, today’s users are more and more likely to interact directly with power electronics equipment. They have many chargers and power supplies for mobile phones and

Digital Object Identifier 10.1109/MPEL.2023.3301416 Date of publication: 26 September 2023

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rechargeables. They use flat panel displays and compact audio systems. They purchase lamps and lighting with builtin power conversion and HVAC systems with variable-speed drives. They might have an electric car. They see the growth of electrical energy applications. Admittedly, the interactive experience is not always great. For example, nearly every device needs a different power supply, leading to too many wires (Figure 1), which users rarely appreciate. Human-centered design for power electronics is emerging as an important frontier in our field. This article gives a few examples and hints about the needs and opportunities. Power electronics enables the development of compact electronic devices like smartphones, laptops, and tablets, while also contributing to better lighting solutions, reduced heat generation (and therefore enhanced reliability), extended product lifespan, and lower energy bills. Power electronics add sophistication, functionality, and energy efficiency to various household appliances, including refrigerators, washers, and HVAC systems. Power electronics advances have led to small, lightweight chargers, and power blocks. They have paved the way for new-generation home systems including flat panel displays, home theaters, and smart devices. The emergence of grid-forming power electronics down to residential scales presents new opportunities. Power converters have already brought significant global societal changes, from small electric drives for grain grinding to massive transportation transformations. A smartphone now redefines the quality of life for impoverished or underdeveloped communities by giving access to critical communications and services even when there is hardly any money to put food on the table. There are critical issues and challenges with regard to power converters that we need to tackle in the near future. The discussion around recycling and circular economics remains limited. Defining sustainability in the larger context is essential for the future development and implementation of power electronics. From a system

FIG 1 A typical jumble of power supply leftovers. Most have similar specifications but few are intended to be interchangeable. Even fewer have been designed with recycling in mind.

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integration perspective, attention should be given to power receptacle outlet reliability and life, effective and accessible color-coded displays, power management for peripherals, and all aspects of user interfaces and the user experience. For example, plug-in chargers (Figure 2) tend to wear out electric receptacles quickly and often employ unreliable cords. The absence of insertion life requirements in the UL 498 standard and limited manufacturer specifications have contributed to the inconsistency and short lifespan of receptacles. The lack of consistency

FIG 2 Typical electric vehicle (EV) charging port—not especially ergonomic or user-friendly.

among interchangeable battery packs has added to consumer confusion. The inconsistency and varying quality of rechargeable packs have left people wondering which ones have good value, or are even safe. Car chargers, so far designed to imitate gas pumps, often garner dislike from users who wonder why the engineers make things so difficult. Solar panels have become much cheaper, although many end users find it hard to take advantage of and arrange for their own, cost-effective, and reliable power sources. Many small chargers or appliance power supplies consume electricity even when not in use. This “vampire power” raises questions about efficiency and proper energy conservation, particularly under no-load or light-load scenarios. The frustration extends to outdoor activities such as biking and hiking, where small phone chargers prove insufficient to sustain power despite favorable weather conditions, and affordable solar chargers really do not exist. The lack of solutions to these problems has led individuals to question why they are left to deal with issues that have not been adequately addressed by the experts. Why do we pour massive resources and efforts into increasing the energy density of smartphone batteries when we can easily extend daily battery life by many hours simply by helping the user implement intelligent power management (IPM) features such as turning down screen brightness or auto-brightness (and off when not using) and killing all those radio-hungry applications? There are opportunities for IEEE Power Electronics Society (PELS) members to explore advances such as power over Ethernet (PoE), USB-C, and potential formats for improved interoperability and multi-use supplies. Standards for remote control, data transmission, and active safety; best practices for grid interoperability for electric vehicles; and widespread adoption of electronics in motors and receptacles are just a few of the areas worth considering for further development. Recognizing the importance of considering the end-user perspective, there is now a growing urgency to design power electronics with human-centered design principles. The impact of wide bandgap (WBG) devices is interesting in this respect. Some formerly obsolete designs are experiencing a resurgence because of WBG technology implementations. One example is the revival of currentsource inverters (CSIs) for motor drives. Emerging WBG bidirectional switching devices are promising for CSIs, and also for solid-state circuit breakers, intelligent receptacles, and modular, mass-produced inverter units. Operating temperature increases supported by WBG devices have special promise for fully-integrated motor drives and comprehensive 3D multi-function electronics integration. These advances can revolutionize user experiences. Developing informative user interfaces and experiences is essential for optimizing the efficiency and performance of power electronics and the applications they support. A few aspects are already being addressed by emerging academic programs and courses that are



focused on social design thinking and design for social impact in the field of power conversion. Design for sustainability is starting to emerge. Some others are attracting industry innovations. Dedicated, interdisciplinary facilities are being established to foster innovation and collaboration in this rapidly evolving field. On a global scale, it is important to understand how technology can be accepted and perform energy-related functions, enabling life-changing energy access and functionality for underserved communities and the poor. We, as power electronics engineers and experts, still have a lot of work to do in “advancing technology for humanity.” These discussions, and a lot more, were facilitated in the IEEE PELS Future of Electronic Power Processing and Conversion” (FEPPCON XI) 2022 workshop session titled “Human Impact of Power Electronics.” The organization of this session involved three expert panel talks and open discussion. The topics included 1) user-driven design and the impact of power electronics on human lives (by Prof. Philip Krein of the University of Illinois Urbana–Champaign); 2) energy access and how power electronics will enable global economic impact (by Prof. Deepak Divan of Georgia Tech); and 3) how advancements in motors and drives will change the world (by Prof. Thomas Jahns of the University of Wisconsin–Madison). This FEPPCON XI session aimed to link power electronics to the ultimate user and to encourage the broader technical community to think about further positive impacts on society. This session emphasized developing a human perspective on the social and psychological aspects of power conversion systems, including how people will accept (or deny) future technological advancements.

About the Authors Harish Sarma Krishnamoorthy ([email protected]) is an Assistant Professor with the ECE Department, University of Houston, Houston, TX, USA. He is the Immediate Past Chair of the IEEE PELS’ Students and Young Professionals Committee and the Current Standards Liaison for the IEEE PELS’ TC7-Technical Committee on Critical Power and Energy Storage Systems. He was also a Session Chair of FEPPCON’2022. Philip Krein ([email protected]) holds a Grainger Endowed Chair Emeritus Professorship in Electric Machinery and Electromechanics with the University of Illinois Urbana–Champaign. He is a Past President of PELS, received the IEEE William E. Newell Power Electronics Award in 2003, and received the IEEE Transportation Technologies Award in 2021. Brian Zahnstecher ([email protected]) is a Senior Member of IEEE, the Chair (Emeritus) of IEEE SFBAC PELS, IEEE PELS Regional (R1-3) Chair, sits on PSMA Advisory Council, is the Co-Chair of its Energy Harvesting Committee, the Co-Founder/Co-Chair of the EnerHarv workshop, and is a Principal of PowerRox. September 2023

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PSMA Corner

by Renee Yawger

WiPDA Celebrates Tenth Anniversary

S

ponsored by IEEE Power Electronics Society/Electron Devices Society/Power Sources Manufacturers Association (PELS/EDS/PSMA), the Workshop on Wide Bandgap Power Devices and Applications (WiPDA) [http:// www.wipda.org/] is an internationally recognized workshop dedicated to advancing the field of wide bandgap (WBG) power devices and applications. It provides a platform for leading researchers, industry professionals, and academia to discuss the latest developments and advances in WBG power devices and their applications. Plus, the attendees have the opportunity to witness their journey and understand the pivotal role they can play in shaping the future.

a series of special sessions and keynote presentations will reflect on the progress made in the field and envision the roadmap for future innovations. The commemoration of this milestone presents a unique opportunity for attendees to witness the journey of wide bandgap power devices and understand the pivotal role they can play in shaping its future.

WiPDA 2023—Charlotte, NC, USA WiPDA will take place from 4 to 6 December 2023, at the UNC Charlotte Marriott Hotel and Conference Center in Charlotte, NC, USA (Figure 1). WiPDA will feature a wide range of technical sessions, keynote speeches, tutorials, and poster presentations.

The technical sessions feature peer reviewed presentations by researchers and industry professionals and will cover various topics, including the latest developments in WBG materials, device structures, packaging, characterization techniques, and thermal management. There will also be sessions focusing on power electronics applications, such as electric vehicles (EVs), renewable energy, and data centers. The tutorials are carefully curated by a panel of experts in the field and will cover a wide range of subjects, from fundamental concepts in device fabrications to advanced techniques to develop power electronics systems, providing participants with both valuable insights and practical skills.

Ten Years of Advancements This year’s WiPDA conference holds special significance as it celebrates its tenth anniversary. Over the past decade, WiPDA has played a pivotal role in driving advancements in WBG power devices and applications. As the conference looks back on the achievements of the last ten years as these technologies have developed from nascent platforms to mass production solutions, it also provides a look to the future and the exciting possibilities that lie ahead. During the conference, Digital Object Identifier 10.1109/MPEL.2023.3299917 Date of publication: 26 September 2023

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FIG 1 WiPDA 2023 venue is UNC Charlotte Marriott Hotel and Conference Center.

IEEE POWER ELECTRONICS MAGAZINE z September 2023

Spotlight on Reliability and Technology Roadmap Two special tracks have been added to the WiPDA agenda for 2023. The application (switching) reliability track is the first focused track on application reliability. This track explores the latest advancements in determination of component lifetime, product dynamic high temperature operating life (DHTOL), methods and circuits to apply application-relevant stress, failure modes and mechanisms, monitoring and prognostics, meeting JEDEC JEP180; to the types of stresses seen in circuits with hardswitching, soft-switching, flyback, and other types of operation with power gallium nitride (GaN), silicon carbide (SiC) and silicon (Si). The ITRW special track is a comprehensive research agenda focused on materials, devices, packaging, and applications of WBG power devices. This track explores the latest advancements in WBG technology and provides valuable insights into the current state-of-the-art and future directions of this rapidly evolving field. Join us at WiPDA and engage with leading experts in the field to learn about the latest research findings and gain valuable insights into the future of WBG technology.

Conclusion WiPDA provides a unique opportunity to further advance the field of WBG power devices and applications. The knowledge exchange at these events is critical to identifying emerging trends and addressing challenges. It also provides participants with an opportunity for professional growth and career development through networking and knowledge acquisition. WiPDA helps to bridge the gap between academia and industry, fostering collaboration, innovation, and advancements in the field of power electronics. To r e g i s t e r v i s it : ht t p s: // w ip d a .or g / registration/.

About the Author Renee Yawger ([email protected]) is the Director of Marketing at Efficient Power Conversion Corporation (EPC), El Segundo, CA 90245 USA, and the Director of Corporate Marketing at EPC Space. She has over 25 years of sales and marketing experience within the semiconductor industry. Prior to joining EPC, she was at Vishay Siliconix for nearly 15 years in various positions in sales support, customer service, and regional marketing. At EPC, she is responsible for the product marketing and marketing communication functions globally. She is also the Vice President of the Board of Directors at PSMA.

www.apec-conf.org

Industry Pulse

by Kristen Parrish and Stephanie Watts Butler

Consumer EV Standards and Voltage Trends How Tesla’s Unique Stance Will Impact WBG Semiconductor Market

T

he electric vehicle (EV) market continues to grow, with an estimated 14 million vehicles to be sold by end of 2023 [1]. As EVs continue to appear on the road, the charging infrastructure needed to support them will also continue to scale, especially with the help of government subsidies offered to both manufacturers and consumers (check out the September 2022 column for a deep dive on this [2]). EV hardware, both in the vehicle (drive train/inverter) and in the charging station, will drive rail voltages—and with multiple voltage options comes competing semiconductor requirements. This article explores how implementation of different plug types and charging standards are impacting infrastructure scaling and accessibility, and how these may impact wide bandgap (WBG) semiconductor needs going forward. As with any new technology, uniformity and standardization are a work in progress. Variations in plug type and communications protocol, as well as voltage and current capabilities, exist across North America, Europe, and Asia. The current dominant technology for consumer EV charging is ac to ac, with on-board charging circuitry required on the vehicle to convert ac to dc. There are

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two types of ac charging [3]: a slower Type 1 technology (roughly 5 miles per hour for charge), and the Type 2 technology which is approximately five times as fast. As of July 2023, nearly 80% of charging stations in the U.S. were ac (99% of those being Type 2). Because of the slow rate of charge, ac charging technology is ideal for consumers to install in homes to charge overnight—but is generally considered too slow for use during travel (taking much longer than filling up a gas tank), which can be seen as a barrier to long-distance travel with EVs. To address EV usage beyond the daily commute, public infrastructure must support convenient, on-the-go charging [5]. DC fast charging, true to its name, enables 100–200 miles of charge in just an half hour. Unlike ac chargers, dc fast chargers output dc voltage directly and don’t require onboard ac to dc conversion. As of July 2023, roughly 20% of public U.S. chargers were of this type, but this is expected to grow. Figure 1 shows the number of charging stations across the U.S., by voltage type and connector technology. While CHAdeMO and CSS are commonplace in terms of stations, Tesla (also referred to as the North American Charging Standard, NACS) outnumbers all other types by ports, since many supercharger stations have numerous charging ports. Note that dissimilar connectors on

IEEE POWER ELECTRONICS MAGAZINE z September 2023

automobile and charging port are not always a limiter—Teslas and other EVs are compatible with plug adapters that enable other port types and match their communications protocols. However, this won’t change the voltage that the vehicle can be charged at—a charger at 800 V cannot be used to charge a 400 V vehicle without risk of damage, while plugging an 800 V vehicle into a 400 V limited port will result in slow charging speeds. Figure 2 shows a snapshot of the number of charging stations across regions/countries. One takeaway— China has more fast chargers than the rest of the world combined right now. In China, the GB/T standard was developed by the Standardization Administration of China, with the newest iteration of the standard good up to 750 V [6]. In Japan, the CHAdeMO standard is developed and maintained by a consortium of Tokyo Electric Power and Japanese OEMs [7]. While the first generation was for 500 V, the latest dc fast charging technology aimed at consu mer veh icles is desig ned for 1000 V × 400 A (400 kW). The dominant charging technology in Europe and South Korea, the SAE combined charging system (CCS) standard, uses up to 1000 V— the plug encompasses ac Type 1, Type 2, and dc fast charging [8]. This plug is sometimes referred to as J1772 Combo—J1772 is commonly

FIG 1 Number of electric vehicle charging stations by type (ac Type 1, Type 2, or dc), dc fast charging stations by plug standard, and dc fast charging ports, in the USA station may have more than one port—a Tesla supercharger may have up to 80 ports. J1772 and the J1772 combo are both counted as CCS. Data provided by the Alternative Fuels Data Center, July 2023 [3].

used for ac ty pe chargers. CharIN, a commonly refere n c e d o r g a n i z a t io n w i t h respect to charging standards, is not strictly speaking a standards organization, but a lobbying organization for the CCS standard. Finally, the dominant dc fa st cha rge tech nolog y i n North America with a majority of ports is from Tesla, which is also called the NACS. While the NACS connector and standard is good for 1000 V, today’s Tesla Supercharger  only delivers power at 500 V. While not originally developed by a consortium, NACS is used by other vehicle manufacturers, including Ford, Riv ia n, a nd GM. Charging station companies such as Chargepoint and ABB have also committed to adding the Tesla charger [9]. SAE recently announced efforts to standardize the technology as SAE J3400 [10]. In Table 1, we can see how the standards around the world might drive future power semiconductor trends. All the standards have a maximum voltage allowed at 750 V and above, and most allow 1000 V. Outside of North America, the focus might appear to be to implement charging at 800 V [11]. As early as 2021, EV manufacturers BYD, Huawei, Xpeng, and Great Wall Motors have announced

FIG 2 Number of EV charging stations around the globe in 2022. Data from [4].

800 V vehicles coming soon [12]. Outside of China, companies such as Audi, Hyundai, Porsche, and Kia recently announced 800 V vehicles, with Lucid announcing a 900 V vehicle [13]. The ramp to 800 V may be slow though—while innovation may be happening, one analyst predicts that from a market point of view, by 2025 only 12% of EVs on the road will be 800 V capable [14]. On the other hand, Tesla executives have gone on record saying that they don’t see sufficient value to going towards 800 V vehicles [15], which likely means that superchargers will remain at 500 V for the near future. Thus, while all the standards allow >750 V maximum voltage, the majority of charging ports available may only be 500 V. This situation demonstrates how the exact implementation of the standard, not the standard itself, determines the power semiconductor required. In conclusion, we return to the question posed at the beginning of the column—what will be the impact on WBG semiconductor trends? The divide between 800 and 400 V vehicles and chargers points to a potential semiconductor differentiation. If the predominant voltage remains in the 500 V and below range, GaN is obviously an option. This situation is now more likely as consumer EV and charging station suppliers coalesce around Tesla. For 750 V+ chargers, a multi-level topology would be required for GaN, and thus SiC might continue to be favored. Both voltages enable different tradeoffs in charging time, efficiency, and costs. Recent proposals for hybrid solutions with IGBT may make for the best cost-efficiency trade-off, but the equation is very different due to differences in cost and voltage/current capabilities between GaN and SiC [16], [17].

About the Authors Kristen Parrish ([email protected]) received the bachelor’s degree from the Rose-Hulman Institute of Technology, Terre Haute, IN, USA, and the master’s and Ph.D. degrees from The University of Texas at Austin, Austin, TX, USA, before embarking on a career spanning multiple fields, ultimately working in power electronics at both Texas Instruments, Dallas,

Table 1. Global EV charging connectors, standards, and corresponding –– voltage levels*. Connector

Standard

Max Voltage [V]

Primary Locations

GB/T

20234.3

750

China

SAE CCS (J1772 Combo)

SAE CCS

1000

Europe, S. Korea, USA

Tesla/NACS

TS-0023666

1000

USA

CHAdeMO

2.0

1000

USA, Japan

*Charger and on-vehicle battery and inverter capabilities will vary by manufacturer.

TX, and Wolfspeed, Durham, NC, USA. Her work experience includes a Research and Development Engineer, a Systems Engineer, and most recently as an Applications Engineer with projects in packaging, magnetics, and silicon carbide. During her career, she has been involved with IEEE at the local section level, serving as the Eastern North Carolina Vice-Chair, the Women in Engineering (WIE) Chair, and the Webmaster, and also at the society level on the PELS

WIE Steering Committee. She became a Senior Member of IEEE in 2020. She has also created a mentoring program that connected mentors and YP mentees in IEEE Region 3 during the early days of the COVID-19 pandemic, which was nominated for the MGA Young Professionals Achievement Award. She is passionate about mentoring and career development of women in engineering. Stephanie Watts Butler, Ph.D., P.E. ([email protected]) is the

President of WattsButler LLC, an innovation services company focused on the power semiconductor industry. During her previous career at Texas Instruments, Dallas, TX, USA, she produced innovations in the areas of power and CMOS process and package technology, processing equipment, materials, reliability, research and development management, manufacturing science, control, fault detection, metrology, and new product development, generating 17 U.S. patents. She is the Co-Founder and the Past-Chair of JEDEC’s JC-70 WBG Standards Committee and the CoConvenor of IEC’s TC47/WG8. She is the Industry Deputy Editor-in-Chief of IEEE Power Electronics Magazine, a PELS Member-at-Large (AdCom), the Chair of the PELS Industry Committee, and a WIE Committee Member. She also serves on the APEC Planning Committee and the PSMA Board of Directors and the Semiconductor

Committee. She is a Fellow of the AVS and a Senior Member of IEEE.

[7] Accessed: Jul. 12, 2023. [Online]. Available:

[13] Accessed: Jul. 12, 2023. [Online]. Available:

https://www.chademo.com/about-us/what-is-

https://www.autonews.com/technology/ev-indus-

chademo

try-seen-shifting-800-volt-technology

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https://www.iea.org/news/demand-for-electric-

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the-analyst.html?chid=13

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[16] APEC 2023 Keynote: GaN for EV Power

https://afdc.energy.gov/fuels/electricity_infra-

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[17] Is Tesla Moving Backwards to Silicon? Adam

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Expert View

by Alex Lidow

The Ascent of GaN An Update on the Rate of Adoption and the Future of GaN Power Devices

I

n this article, the factors impacting gallium nitride (GaN) adoption are examined, as well as how they are being addressed and overcome. The key issues that we’ve heard from customers over the last 13 years that EPC has been in volume production fall into the following categories: 1) Small Size and Thermal Management: The GaN devices can be 10–15 times smaller than the power MOSFETs they are replacing. This leads to challenges in manufacturing, as well as design, and with small size also comes the issue of thermal management. 2) Reliability Concerns: Customers are concerned with how a new technology will work reliably for the lifetime of their application. 3) Ease of Use: There has been concern about ease of use considering the device is 10–100 times higher speed than the MOSFET it is replacing and there traditionally has been less infrastructure in place to support gallium nitride devices. 4) Cost: If the cost of new technology remains high, only niche applications will adopt it. As the cost of GaN crosses over the cost of silicon, the ramp to mass adoption accelerates.

Digital Object Identifier 10.1109/MPEL.2023.3299936 Date of publication: 26 September 2023



W hat About the Table–– 1. GaN FET versus silicon FET comparison. Small Size? Table 1 shows a fifth generation GaN device that is about 10 mm 2 against a benchmark silicon Silicon FET GaN FET device that is about 31 Parameter (@ 10VGS) (@ 5VGS) m m 2 . T he on-resi s RDS(on) max 2.7 mΩ 2.2 mΩ tance of the MOSFET 89 nC 22 nC QG typ is about 20% higher than the GaN device. QGD typ 18 nC 1.9 nC However, the die size 89 nC 0 nC QRR typ of the GaN device is 20°C/W max 0.3°C/W typ RTJC 3× smaller than the 10.2 mm2 Device Size 31 mm2 M O S F E T. D e s p i t e that, the ther ma l resistance to the case ity report, we not only characterize is 70 times lower for the GaN device the failure mechanisms of GaN but where you can dissipate heat in all show how these mechanisms can be directions. used to demonstrate reliability What About Reliability? GaN under application-specific mission is a wide bandgap (WBG) semiconprofiles. The extraordinary lifetime ductor, which means that there is a capabi l it y of Ga N dev ices ha s tighter chemical bond between the shown to be much greater than gallium and the nitrogen atoms than power MOSFETs. there is between silicon atoms in a Are These Devices Easy to silicon device. And that has been Use? Admittedly, wafer level chip demonstrated to make the devices scale devices are smaller and require more rugged and reliable and less more precision handling tools. Also, sensitive to thermal and radiation the devices are 10× faster, which effects. Extremely conservative and means that circuits designed with rugged applications have adopted GaN are more sensitive to parasitics, GaN, including satellites, automoparticularly parasitic inductance. tive, and solar. Solar is an extraordiTherefore, a careful layout is very n a r i ly de m a nd i n g a p pl ic a t io n important. because the equipment is sitting in a To further mitigate some of these variety of very difficult harsh envihandling concerns, there are power ronments and must last 35 years in devices offered in power quad flat some cases. In our phase 15 reliabilSeptember 2023

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Table 2. Comparing Gen 6 GaN versus –– benchmark Si MOSFET.

Parameter

Silicon (@ 10 VGS)

Gen 6 GaN (@ 5 VGS)

VDS

80 V

80 V

RDS(on) max

2.7 mΩ

4 mΩ

RDS(on) ⋅ Area

81

12

RDS(on) ⋅ QG

162

27

RDS(on) ⋅ QOSS

227

87

RDS(on) ⋅ QGD

32

3

Device Size

30 mm2

3.75 mm2

no-lead (PQFN) packages. This package adds no inductance, no electrical resistance, and is extraordinarily thermally efficient. It combines the tremendous advantage of low thermal resistance with the ease of PQFN assembly. To make GaN even easier to design and use, integrated circuits are available from multiple suppliers. As an example, there are monolithic power stages which include the high side and low side power devices integrated with their drivers, with a level shift, and with a sink boot to generate the high side gate signal. These solutions save design time but are also easier to use; all the designer needs is a logic-level input from the controller to get power output. Integration eliminates all the parasitic inductances that add to EMI and slow down the device. The resulting system is much smaller, and the efficiency is better. What About the Cost? There is still an outdated belief that GaN is more expensive than silicon, which is simply not true. In 2023 at the IEEE Applied Power Electronics Conference & Expoasition (APEC), EPC set up a booth and challenged people to bring their MOSFET part number and compare the pricing of the equivalent GaN FET. Sixty percent of the people who took the challenge found that the price of the GaN FET was lower than the silicon MOSFET. Of the 24% that had higher prices they were very old, very cheap MOSFETs. When comparing GaN against state-ofthe-art MOSFETs, the GaN FETs were always priced lower. State of GaN Today: Adoption is paced by customers perceptions a nd my ths, most of which are based on older and earlier generations of GaN technology. In October of 2022, EPC’s first generation-six device with double the power density of pr ior generations wa s

In summary, the barriers to mass adoption of GaN power devices are rapidly falling and early adopters will have a distinct advantage over their competitors.

About the Author

FIG 1 Buck converter efficiency is 2% points higher.

r ele a s e d . I n a ppl ic a t ion s t h i s translates to higher efficiency and higher power output in a smaller footprint. Table 2 shows a comparison of a Gen 6 device against a benchmark silicon MOSFET that is eight times larger in size. Figure 1

shows that despite the GaN device being 30% higher in on-resistance and significantly smaller, the efficiency of the device in a 48–12 V buck converter at 500 kHZ is 2% points higher and the losses are almost 40% lower.

Alex Lidow (alex.lidow@epc-co. com) is the CEO and the Co-Founder of Efficient Power Conversion Corporation (EPC), El Segundo, CA 90245 USA. Prior to founding EPC, he was the CEO of International Rectifier Corporation. A Co-Inventor of the HEXFET power MOSFET, he holds many patents in power semiconductor technology and has authored numerous publications on related subjects, including co-authoring the first textbook on GaN transistors, titled GaN Transistors for Efficient Power Conversion, now in its third edition published by John Wiley and Sons. He received the B.Sc. degree from Caltech and the Ph.D. degree from Stanford.

Women in Engineering

by Katherine A. Kim, Yunting Liu, Stephanie Watts Butler, Sneha Narasimhan, Kristen Parrish, Mhret Berhe Gebremariam, and Christina DiMarino

Women in IEEE PELS Charting Progress Towards Inclusivity

A

fter emerging from the peak of the COVID era, with heavy travel restrictions and less-than-optimal interactions at virtual conferences, we ventured out to our first in-person conferences over the past year. What awaited us was the heartening sight of more women taking up prominent roles in every aspect of the conference. From influential plenary speakers to confident session chairs, passionate presenters, engaged attendees, and dedicated organizers. It served as a powerful reminder that the traditionally maledominated domain is gradually transforming and becoming more inclusive. While a considerable journey remains ahead, we made unmistakable progress this past year. Our investigation into the representation of women in IEEE Power Electronics Society (PELS) began with an article published in 2021 that introduced key statistics [1], followed by a subsequent article in 2022 that updated and expanded the statistics [2]. In this third edition, we delve again into the statistics spanning the

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past to the present, assessing the progress made by the IEEE PELS community and identifying areas that require further improvement. The IEEE PELS is committed to enhancing diversity and inclusion (D&I) efforts [3]. By closely examining the statistics, we gain insights into the changing landscape of various aspects concer ning the representation of women, such as membership and society-level recognition. It is important to note that diversity encompasses not only gender but also regional, racial, cultural, and affiliation factors (industry, government, versus academia). However, we focus on gender metrics because it is a common underrepresentation across all regions in IEEE, w it h dat a goi ng back mu ltiple decades. Let’s see what the numbers can tell us.

Membership The percentage of women members of IEEE, PELS, and some sister societies—Industrial Applications Society (IAS), Power & Energy Society (PES), and Electron Devices Society (EDS) are shown up to 2022 in Figure 1. In 2022, the percentage

IEEE POWER ELECTRONICS MAGAZINE z September 2023

of women PELS members was 13.6%, which is a 1.8% increase from the previous year. However, PELS still falls short of 16%, which was the percentage of women in all of IEEE and is also behind sister societies IAS (15.2%) and PES (16.1%), but exceeds that for EDS (12.2%). PELS is on a promising trajectory, and we hope to see the numbers continue to rise over the coming years. The PELS women member percentage (13.6%) is used as a baseline for comparison in the following sections to assess progress. Diving deeper into the membership data, we see a more profound story with some hopeful and some concerning trends. Figure 2(a) shows the number of women PELS members divided into each membership grade. All membership levels have seen an increase in women members, except for Fellows. Like the previous year, student membership represents the most significant number of women members in 2022 (55.4% undergraduate and 13.0% graduate student members). Looking at the data over time, we would hope to see the undergraduate students transfer directly to graduate or regula r

FIG 1 Historical data on the percentage of women members up to 2022 in IEEE (blue), PELS (red), and sister societies. Source: IEEE PELS.

there is one woman in a room of 20 members (6.4% women for members and 7.2% women for senior members). Unfortunately, the representation of women at the Fellow level is the lowest at 2.2%, which is analogous to one woman in a room of 50 Fellows. One concerning trend is that the percentage of women Fellows has stagnated over the last three years and decreased in 2022 compared to the previous year. Some ideas on addressing this problem are at the end of this article.

Leadership members; while there was some growth in the graduate student and regular member numbers since the previous year, there is still work to be done to retain more undergraduate members as they graduate. Another way to examine the data is to examine the percentage of women in each member grade, shown in Figure 2(b). For example, if

you had ten undergraduate members in a room, four would be women (39.6%). This promising trend shows that young women are interested in power electronics and are likely involved at the student chapter level. For a room of ten graduate student members, at least one would be a woman (12.2%). For members and senior members, it is more likely that

PELS leadership positions are also crucial for assessing inclusivity as it reflects who can be recognized and succeed in our society. First, we look at the representation of women in the Administrative Committee (AdCom), as shown in Figure 3. For 2023, there is a record of 28.6% women voting members, an increase from the previous year and well above the membership

FIG 2 From 2010 to 2022, (a) the number of women members in PELS according to membership grade and (b) the percentage of women in each membership grade. Source: IEEE PELS.

baseline. Two new women membersat-large elected for three-year terms starting in 2023 were Mahshid Amirabadi (Northeastern, USA) and Hong Li (Beijing Jiaotong University, China). Along with eight other women out of 35 voting members, this strong representation of women in the AdCom is vital for ensuring diverse perspectives are being considered. A woman has not yet been elected for the PELS president or vice president (VP) positions, but efforts have been made to ensure women are nominated for these leadership positions. In 2022, two women were cand id a t e s for t wo d i f fer e nt V P positions, but neither was successfully elected. Despite this, the stage is set for women to take PELS leadership positions in the near future, mainly since the pool of candidates for these positions is chosen from the AdCom membership, which has the highest percentage of women in PELS history.

Recognition One role of the IEEE Societies is recognizing its members’ contributions through society awards. Figure 4 shows the percentage of women awardees of PELS awards up to 2023. In 2022, the percentage of women awardees reached 14.3%, just exceeding the PELS membership baseline (13.6%). However, the recentlyannounced PELS awards for 2023 had zero women recipients; this is out of twelve society awards, two technical field awards, and one IEEE medal

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FIG 3 Percentage of women voting members of PELS AdCom (yellow) from 2010 to 2023. Source: IEEE PELS.

sponsored by PELS. The disappointing fact that no women were recognized for their achievements through PELS awards in 2023 is a sign that there is still a gap in the recognition of women PELS members for their achievements, and PELS needs more effort in this area. It should be noted that the PELS Ph.D. Thesis Talks (P3 Talks) were not included in statistics for Figure 4 (the winners for 2023 were not yet announced). The P3 Talks became an official PELS society award in 2022, but there have been P3 Talk winners since 2019. There have been five winners per year, and so far, one woman has been a recipient each year (20% women awardees). The P3 Talk Awards are aimed at graduating Ph.D. students, so this is good recog n it ion for g r a du at e

IEEE POWER ELECTRONICS MAGAZINE z September 2023

student members, but a gap still remains for recognition of highergrade women PELS members. Other important types of recognition within PELS are distinguished lecturers (DLs) and regional distinguished lecturers (RDLs). The DLs and RDLs ser ve as high-profile speakers who can be invited by PELS chapters to give talks on their achievements in the field of power electronics. DLs are nominated by peer s (or sel f-nom i n at ed) a nd selected by the PELS DL selection committee. RDLs are nominated by the PELS Regional Liaisons and approved by the PELS DL program ch a i r a nd V P of member sh ip. Figure 5 shows the percentage of women in each of these roles up to 2023. For 2023, the percentage of women DL s i s 25.0 % , a nd t he

percentage of women RDLs is 30.4%. The women DLs for 2023 are Maryam Saeedifard (Georgia Institute of Technology) and Keyue Ma Smedley (University of California Irvine), and there are also seven women RDLs. Having women recognized as disting u i shed lec t u rer s at bot h t he regional and societal levels at these percentages is heartening and sets out a good goal for the level of representation that we hope to see at all levels of PELS in the future. Elevation to IEEE Fellow is a nother cr itical recognition for members. Although the final evaluation takes place at the IEEE level, the initial part of the evaluation occurs at the societal level. Each nominee chooses one IEEE Society which does the initial nomination review. The number of women nominees and recipients through PELS is also an indication of our society’s inclusiveness. Figure 6 shows the percentage of women Fellows elevated through PELS (red), the percentage of elevated women IEEE Fel lows i nclud i ng a l l societies

FIG 4 Percentage of women awarded PELS-sponsored awards (yellow) from 2010 to 2023. Source: IEEE PELS.

(blue), and the percentage of elevated Fellows who are PELS members (yellow) regardless of which society did the elevation from 2010 to 2023. Using the percentage of women elevated through all societies (10.7% in 2023) as the baseline, the percentage elevated through PELS (16.7% in 2023) has exceeded the baseline for 2022 and 2023; this

is a result of one woman elevated to IEEE Fellow through PELS per class for the last two years. Note that in 2023, only six members were elevated through PELS, while in 2022, there were eight. Among those honored with IEEE Fellow elevation in 2023 was Marta Molinas (Norwegian University of Science and Technology, Norway) for “contributions

retain the number of women members actively involved in PELS at all membership levels.

What Can You Do? Be Counted Accurately

FIG 5 Percentage of women PELS distinguished lecturers (yellow) and PELS regional distinguished lecturers (green) from 2017 to 2023. Source: IEEE PELS.

The accuracy of the baseline statistics (Figures 1 and 2) relies on selfreported gender data through each member’s IEEE personal profile, which gives options of “female,” “male,” “other,” and “prefer not to answer.” Using the online IEEE OU Analytics tool, members can check a number of membership metrics, including gender and grade for all societies. As of June 2023, 7.0% of PELS members were listed as female while 7.3% were listed as unknown (either “other” or “prefer not to answer”). Having accurate gender data gives a more realistic picture of our society, so please check the gender listed in your IEEE profile and make sure it accurately reflects your gender identity. (You can check this by going to www.ieee.org, logging in, going to your profile, and then clicking “Personal Profile.”)

Summary

FIG 6 Percentage of women Fellows per elected class elevated through PELS (red) compared to all of IEEE (blue) and elevated Fellows who are PELS members (yellow) from 2010 to 2023. Source: IEEE PELS.

to modeling and stability of power electronics.” Dr. Molinas has also contributed to the PELS WIE community, and an article was written about a talk she gave at a PELS WIE Breakfast in [3]. For the next couple of years, we hope to see at least one woman Fellow elevated through PELS each year to sustain this progress.

PELS WIE Events The PELS WIE committee regularly organizes events at major PELS conferences to provide networking, mentorship, and volunteer opportunities, which are open to all. At these events,

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the level of female participation has been significantly higher than the proportion of women in IEEE PELS membership. At ECCE 2022 and APEC 2023, PELS WIE hosted inclusivity-themed breakfast networking events. The gender identity statistics of attendees at these two WIE events are shown in Figure 7, where female participation reached 41% (ECCE 2022) and 39% (APEC 2023). Compared to the percentage of women PELS members, which stands at 13.6%, women are highly engaged in activities related to inclusivity. These PELS WIE events serve as an important opportunity to increase and

IEEE POWER ELECTRONICS MAGAZINE z September 2023

We see a lot of hopeful trends toward improved representation of women in membership, leadership, and representation. Research points to 30% as a critical mass threshold for any minority group and is often considered a tipping point for resulting change [4]. Using 30% as a threshold, PELS is doing exceptionally well regarding undergraduate women membership (39.6% in 2022) and women RDLs (30.4% in 2023). Next, considering the baseline of 13.6% (women PELS members in 2023) up to 30% as an “on-track” target range, PELS is on-track in terms of women voting members on the Administrative Committee (28.6% in 2023), women DLs (25.0% in 2023), and women Fellows elevated by PELS (16.7% in 2023). Finally, below the 13.6% baseline is the range where PELS needs further efforts, which include women PELS awardees (0%  in 2023), and also women

FIG 7 Gender identity of participants at PELS WIE events at ECCE 2022 and APEC 2023. Source: IEEE PELS.

membership at the grades of graduate student (12.2% in 2022), member (6.4% in 2022), senior member (7.2% in 2022), and Fellow (2.2% in 2022). For women to become and stay PELS members, they need to feel included, engaged, and valued in our society.

One disheartening statistic in this report is the declining trend of women Fellows, currently standing at 2.2%. While the historical male dominance of the field partly explains this low figure, it does not account for the overall decrease observed in recent

years. One approach to help increase the number of women Fellows is to recognize and elevate more outstanding women members within the society, which we can begin to address through initiatives. Firstly, to be nominated as a Fellow, individuals must hold senior membership, which regular members can apply for after ten years of professional experience. Raising awareness through diverse media platforms and organizing senior member drives specifically targeting women (and underrepresented groups) are effective ways to expand the pool of eligible woman candidates. Secondly, it is crucial to encourage current Fellows to advocate for and support nominations of qualified women candidates. Women Fellows serve as powerful role models for female members, and recognizing more deserving women in PELS as Fellows will inspire and empower young women members, cultivating their aspirations for future success.

Although there were some setbacks in PELS award recognition, this year’s report has generally shown improved representation of women in many areas of PELS. The true test of sustained change will be if the representation of women increases (or is at least maintained) over the next few years. We will continue to shine a light on these statistics as our society grows through these annual reports.

Acknowledgment This article was written with editorial assistance using ChatGPT from Open AI.

About the Authors Katherine A. Kim (katherine.kim@ ieee.org) received the B.S. degree from the Franklin W. Olin College of Engineering, in 2007, and the M.S. and Ph.D. degrees from the University of Illinois at Urbana-Champaign, in 2011 and 2014, respectively. She is an Associate Professor of electrical engineering at National Taiwan University, Taipei, Taiwan. She received the Richard M. Bass Outstanding Young Power Electronics Engineer Award from IEEE PELS in 2019, and recognition as an Innovator under 35 for the Asia Pacific Region by the MIT Technology Review in 2020. For IEEE PELS, she served as a Member-atLarge for 2016–2018, the PELS Women in Engineering Chair in 2018– 2020, and the PELS Constitution and Bylaws Chair 2021–2024. Yunting Liu ([email protected]) received the B.S. degree in electrical engineering from the Huazhong University of Science and Technology, Wuhan, China, in 2013, and the Ph.D. degree in electrical engineering from Michigan State University, East Lansing, MI, USA, in 2019. She joined The Pennsylvania State University, University Park, PA 16802 USA, as an Assistant Professor, in 2022. Prior to joining Penn State, she was an Assistant Professor with Michigan Technological University, from 2021 to 2022 and was a Post-Doctoral Research Associate with The University of Tennessee, Knoxville, TN, USA, from

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2019 to 2021. She does research in the areas of electric power conversion, multilevel converters, electric vehicles, interfaces with renewable and distributed energy resources, and reactive power compensation. Stephanie Watts Butler, Ph.D., P.E. ([email protected]) is the President of WattsButler LLC, an innovation services company focused on the power semiconductor industry. During her previous career at Texas Instruments, she produced innovations in the areas of power and CMOS process and package technology, processing equipment, materia l s , r el i a bi l it y, r e s e a r c h a nd development management, manufacturing science, control, fault detection, metrology, and new product development generating 17 U.S. patents. She is the Co-Founder and the Past-Chair of JEDEC’s JC-70 wide bandgap standards committee, the Co-Convenor of IEC’s TC47/WG8. She is the Industry Deputy Editor-inChief of IEEE Power Electronics Magazine, a PELS Member-at-Large (ADCOM), the Chair of the PELS Industry Committee, and a WIE Committee Member. She also serves on the APEC Planning Committee and the PSMA Board of Directors and the Semiconductor Committee. She is a Fellow of the AVS and a Senior Member of IEEE. Sneha Narasimhan (snarasi7@ ncsu.edu) received the B.Tech. degree in electrical and electronics engineering from Amrita University, India, in 2013 and the M.S. degree in electrical engineering from the University of Minnesota, in 2015. Since 2018, she has been pursuing the Ph.D. degree with FREEDM Systems Center, North Carolina State University, Raleigh, NC 27695 USA. In 2015, she joined Rockwell Automation as an Associate Hardware Engineer with Mequon Office. In 2019, she interned at ABB Corporate Research Center, Raleigh. Her research interests include wide band-gap devices, current source inverters, and high-speed motor drives. She was recognized as a Graduate Student of the Year for scholarly

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achievement at NC State in 2023. She also secured first place at the ECE Symposium in 2023. She is currently the IEEE Power Electronics Society (PELS) Women in Engineering (WiE) Treasurer. Kristen Parrish (kristen@ieee. org) received the bachelor’s degree from the Rose-Hulman Institute of Technology, Terre Haute, IN, USA, and the master’s and Ph.D. degrees from The University of Texas at Austin, Austin, TX, USA, before embarking on a career spanning multiple fields, ultimately working in power electronics at both Texas Instruments, Dallas, TX, and Wolfspeed, Durham, NC, USA. She is currently unaffiliated, but she is located in Beijing, China. Her work experience includes Research and Development Engineer, Systems Engineer, and most recently as an applications engineer with projects in packaging, magnetics, and silicon carbide. Duri n g her c a r e er, s he h a s be en involved with IEEE at the local section level, serving as the Eastern Nor th Ca roli na Vice - Cha ir, the Women in Engineering (WIE) Chair, and the Webmaster, and also at the society level on the PELS WIE Steeri ng Com m it t ee. She beca me a Senior Member of IEEE in 2020. She has also created a mentoring program that connected mentors and YP mentees in IEEE Region 3 during the early days of the COVID-19 pandemic, which was nominated for. She is passionate about mentoring and career development of women in engineering. Mhret Berhe Gebremariam ([email protected]) is currently pursuing the Ph.D. degree with the Department of Electrical Engineering, University of Oviedo, Oviedo, Spain. She is a Researcher with the Department of Electrical Engineering, University of Oviedo, working in the design and control of grid-forming inverters for buildingto-building energy exchange applic a t ion s. She i s a l s o a Globa l Sustainable Electricity Par tnership’s (GSEP’s) Young Ambassador

for Globa l Elect r i f icat ion. She received the B.Sc. degree in electrical and electronics engineering from Mekelle University, Mekelle, Ethiopia, in 2016, and the M.Sc. degree in sustainable transportation and electrical power systems (Erasmus Mundus Masters) from the Univer sit y of Not ti ng ha m a nd t he University of Oviedo, in 2020. Her research interests include the control of grid-forming inverters and the control of grid-tied power converters for distributed resources integration. She is a member of the IEEE Power Electronics Society (PELS) and a member of the PELS Women in Engineering. She also serves as a Liaison for Africa in the Industrial Power Conversion Systems Department (IPCSD)—Divers i t y, E q u i t y, a n d I n c l u s i o n Committee (DEIC) of the IEEE Industry Applications Society (IAS). Christina DiMarino (dimar i n o @ v t .e d u) i s a n A s s i s t a n t

Professor with the Bradley Department of Electrical and Computer Engineering (ECE), Virginia Tech, Blacksburg, VA, USA, working in the Center for Power Electronics Systems (CPES). She received the B.S. degree in engineering from James Madison University, and the M.S. and Ph.D. degrees in electrical engineering from Virginia Tech. Her resea rch i nterest s i nclude power electronics packaging, highdensity integration, medium-volta ge power modu le s, a nd w ide bandgap power semiconductors. She is a member of the IEEE Power Electronics Society (PELS), where she currently serves as a Memberat-Large for the PELS Administrative Committee, Vice Chair for the PELS Tech n ica l Com m it tee on Power Components, Integration, and Power ICs, and is a Member of the PELS Women in Engineering committee. She is the Advisor of the PELS Student Branch Chapter

at Virginia Tech, and is a member of the ECE Diversity and Inclusion Committee at Virginia Tech.

References [1] K. A. Kim et al., “Women in IEEE PELS: Learning from the past defining the future [women in engineering],” IEEE Power Electron. Mag., vol. 8, no. 2, pp. 70–75, Jun. 2021. [2] K. A. Kim et al., “Women in IEEE PELS: Progress and opportunities [women in engineering],” IEEE Power Electron. Mag., vol. 9, no. 2, pp. 74–81, Jun. 2022, doi: 10.1109/ MPEL.2022.3169875. [3] K. A. Kim, “Career advice from inspiring IEEE members at the women in engineering breakfast [women in engineering],” IEEE Power Electron. Mag., vol. 5, no. 3, pp. 64–65, Sep. 2018, doi: 10.1109/MPEL.2018.2851122. [4] T. Khwaja, P. L. Eddy, and K. Ward, “Critical approaches to women and gender in higher education: Reaching the tipping point for change,” in Critical Approaches to Women and Gender in Higher Education, P. Eddy, K. Ward, and T. Khwaja, Eds. New York, NY, USA: Macmillan, 2017, doi: 10.1057/978-1-137-59285-9_15

Students and Young Professionals Rendezvous

by John Noon and Joseph P. Kozak

PELS Day 2023 Looks Back to Support Local Chapters

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n 20 June 1987 the ■        “ Empowering Sustainable IEEE Power ElecFuture: Power Electronics tronics Society for a Greener World” in (PELS) became a full-fledged Enugu, Nigeria.  society within the IEEE. ■        PELS Day celebration with Since 2019, there has been a PELS Distinguished Lecturpush for the local, regional, er Dr. Keyue Ma Smedley and global celebrations to and a panel discussion on commemorate the founding energy transition in Paraiba, of the society. This year, Brazil.  there was excellent partici■        G aN Device Seminar in pation and engagement Ottawa, Canada.  worldwide through the ■        “Miniaturized Power Manevents and activities hosted agement that Disappears & and supported by PELS. Merges with the EnvironThroughout the month of ment” in Santa Clara, CA, June, 68 events were held USA.  worldwide, and the festivities For local chapters, PELS reached their peak on PELS FIG 1 The 2023 PELS Day People’s Choice photo contest winner subprovided financial support to Day with the global lecture mitted by the IEEE PELS SBC Chapter at GCEK, Kerala, India. qua l i f y i ng chapter s who delivered by Former PELS hosted events, and further P re sident , P rof. D u sh a n provided PELS Day themed deliver it instantly, at the speed of Boroyevich, a university distinmerchandise to some chapters as light, to customers anywhere around guished professor and the deputy available. These resources facilitated the world. Just as we are now using director of the Center for Power Elecchapters with the opportunity to the internet. This led to interesting tronics Systems, Virginia Tech, engage their local communities spediscussion and thought. The recorded Blacksburg, VA, USA. The PELS cifically for PELS Day. Over 60 chaplecture can be found through the motto is Powering a Sustainable ters across the five continents! PELS Resource Center, but a brief Future, and Prof. Boroyevich’s lecFurthermore, chapters could enter takeaway from the lecture is that ture, titled “Global Intergrid for Susthe annual photo contest which there has never been a more exciting tainable Energy Abundance” fit the reached a record 63,000 votes being or more important time to be a power theme in stride. Prof. Boroyevich cast in total. Congratulations to the electronics engineer!   highlighted the new electronic power IEEE PELS Student Branch Chapter The events that were held around grid, the Intergrid, could collect (SBC) at the Government College of the world spanned various technical energy from wherever the sun is shinEngineering Kannur (GCEK), Kerala, topics and provided an opportunity ing and the wind is blowing and India, for winning the People’s Choice for in person networking among category (Figure 1). PELS members. A few events to highA final event was held in July to Digital Object Identifier 10.1109/MPEL.2023.3301287 light include:  close the PELS Day festivities. PELS Date of publication: 26 September 2023

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President Brad Lehman and PELS VP of Membership Mark Xu delivered addresses on the state of PELS, and highlighted the many opportunities that are available in today’s society for power electronics engineers. Additionally, the winners of the photo contest were announced, as were the winners of the 2023 PELS Ph.D. Thesis Talk (P3) award! In conclusion, the 2023 edition of the PELS Day celebrations were a success in bringing together members

both locally and globally, increasing the number of chapters and participants engaging with the overall society. Please stay tuned for PELS Day 2024! Excitement for, and around, our profession will be a helpful step in creating the workforce we need to “Power our Sustainable Future!” 

About the Authors John Noon ([email protected]) is a Senior Electrical Engineer with Otis Elevator Company, Farmington, CT,

USA. He is the Co-Chair of the IEEE PELS Day 2023 Committee. He is also the Founder and Chair of the Connecticut Section IEEE PELS Chapter. Joseph P. Kozak (joseph.kozak@ jhuapl.edu) is a Senior Electrical Engineer with The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA. He is the Chair of the IEEE PELS Day 2023 Committee. He is also the Vice-Chair of the IEEE PELS’ Students and Young Professionals’ Committee.

by Haifah Sambo, Bruna Seibel Gehrke, Ripun Phukan, Anshuman Sharma, Nayara Brandão de Freitas, and Joseph P. Kozak

The S&YP Spotlight Program Shining the Light on PELS’ Rising Stars

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he IEEE Power Electronics Society (PELS) Students and Young Professionals (S&YP) Committee launched a new initiative in July 2023; the IEEE PELS S&YP Spotlight Program. The goals of this spotlight program lie at the core of the committee’s mission, which is to support the engagement and development of students and early career engineers in PELS. By highlighting the work and accomplishments of S&YP members, the spotlight program aims to connect this organizational committee with PELS members and showcase the promise lying in its young talent.

Digital Object Identifier 10.1109/MPEL.2023.3301376 Date of publication: 26 September 2023



The IEEE PELS S&YP spotlight program was kicked off with a highlight of the S&YP Committee as a whole. With over 15 active volunteers in various industries and regions around the world (Figure 1), the S&YP Committee leads and organizes the engagement, networking, and mentorship opportunities that tie students a nd you ng professiona ls together and to PELS. This opening issue featured a few of the dynamic activities organized by the committee (YP receptions, WiE YP and You Breakfasts at select conferences, and PELS Day Contests), as well as the overarching mission and goals driving its volunteers (Figure 2). Following this overview of the S&YP Committee, future issues of September 2023

the spotlight program will focus on an individual member of S&YP at a time. Starting with the active volunteers on the committee, each issue will unveil the unique accomplishments as well as the work and volu nteer i ng ex per ience of t he spotlighted member. Issues will be relea sed per iodica lly on PELS’s social media platforms allowing for new stories about our rising engineers to be shared regularly across the globe. To stay updated with IEEE PELS, the S&YP Committee, the spotlight program and instructions to be featured, follow IEEE PELS on Twitter (@ieeepels), Instagram (@ieeepels), and Linked I n ( I E E E Powe r E le c t r o n ic s Society). z IEEE POWER ELECTRONICS MAGAZINE

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FIG 1 Members of the 2023 PELS S&YP Committee.

In addition to launching the spotlight program, the IEEE PELS S&YP Committee is revamping its students activ ities subcom mittee (SAC). Within S&YP, the SAC focuses on delivering a quality student membership experience to IEEE PELS student members across the world, and providing them with diverse opportunities to collaborate and contribute back to the society. In fact, there has been an increase in student engagement in S&YP activities in the past years, which has been of great benefit to the dynamism of PELS. Via SAC, students will have an enhanced representation in PELS to reflect their growing participation in the society. SAC will also enable a larger number of students to partake in the planning and organization of activities related to S&YP and beyond! To make SAC a complete subunit of S&YP, we are seeking dedicated volunteers. By volunteering with SAC, students will make a difference in PELS and have unique networking opportunities while gaining valuable team-building experience. A variety of roles are available and their descriptions can be found following the SAC FAQ QR code in Figure 3. If interested in volunteering with SAC and S&YP, please fill out the short application form following the QR code in Figure 3. Any questions related to SAC or the application process can be directed to the Student Membership Chair, Haifah Sambo ([email protected]).

About the Authors

FIG 2 Mission and goals of the S&YP Committee.

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Haifah Sambo is currently pursuing the Ph.D. degree with the Electrical Engineering and Computer Sciences Department, University of California, Berkeley, CA, USA. She is a Research Fellow with the Electrical Engineering and Computer Sciences Department, University of California. She is currently a member of the IEEE PELS S&YP Committee. Bruna Seibel Gehrke received the Ph.D. degree in power electronics from Universidade Federal de Campina Grande, Campina Grande,

FIG 3 FAQ and application form to become a SAC volunteer.

Brazil. She is currently a member of the IEEE PELS S&YP Committee. Ripun Phukan is a Staff Research and Development Engineer with Delta

Electronics, Research Triangle Park, Raleigh, NC, USA. He is currently a member of the IEEE PELS S&YP Committee.

Anshuman Sharma is a Hardware Engineer with Hitachi Astemo, Farmington Hills, MI, USA. He also serves as the Vice-Chair of the IEEE Power Electronics/Consumer Electronics Chapter at the IEEE Toronto Section and is a member of the IEEE PELS S&YP Committee. Nayara Brandão de Freitas is a development engineer with Siemens Energy in Erlangen, Germany. She is also the Current Chair of the IEEE PELS S&YP Committee. Joseph P. Kozak (joseph.kozak@ jhuapl.edu) is a Senior Electrical Engineer with the Johns Hopkins University Applied Physics Laboratory (JHU-APL), Laurel, MD, USA. He is currently the Vice-Chair of the IEEE PELS S&YP Committee. 

Society News

by Ashok Bindra

IEEE Honors Engineering Pioneers

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very year the IEEE Awards Board recommends a select group of recipients to receive IEEE’s most prestigious honors. These are individuals whose exceptional achievements and outstanding contributions have made a lasting impact on technology, society, and the engineering profession. This year at the IEEE Vision, Innovation, and Challenges Summit (VICS) and Honors Ceremony in Atlanta, GA, USA, there were several recipients of the IEEE medals. Amongst them were Vinton “Vint” Cerf, widely known as the “Father of the Internet,” remote sensing pioneer Melba Crawford, National Instruments (NI) Cofounder James Truchard, and robotics and artificial intelligence (AI) gurus Rodney Brooks and Lydia Kavraki. Other notable names in the power and semiconductor arena included Canadian Professor Kamal Al-Haddad, silicon carbide (SiC) material pioneer Hiroyuki Matsunami, and superjunction power devices researchers Tatsuhiko Fujihira, David James Coe, and Gerald Deboy. The 2023 IEEE Medal of Honor went to Vint Cerf who codesigned the internet protocol and transmission control protocol. An IEEE Life Fellow, Cerf is being recognized “for co-creating the internet architecture and providing sustained leadership in its phenomenal growth in becoming society’s critical infrast r uctu re.” L ikew ise, Craw ford received the IEEE Mildred Digital Object Identifier 10.1109/MPEL.2023.3303115 Date of publication: 26 September 2023

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Dresselhaus Medal for contributions to remote sensing technology and leadership in its application for the benefit of humanity. L i k e w i s e , N I ’s C o f o u n d e r Truchard was the recipient of the IEEE James H. Mulligan, Jr. Education Medal for the development of LabVIEW and establishing worldwide programs to enhance hands-on learning in laboratories and classrooms. And robotics guru Brooks was honored with the IEEE Founders Medal for leadership in resea rch a nd

commercialization of autonomous robotics, including mobile, humanoid, ser vice, and manufacturing robots. The IEEE Frances E. Allen Medal was awarded to Kavraki for foundational probabilistic algorithms and randomized search methods that have broad impact in robotic motion planning and computational biology. Prof. Maryam Saeedifard of Georgia Tech represented IEEE Power Electronics Society (PELS) to help give the IEEE Medal in Power Engineering to Prof. Al-Haddad (Figure 1),

FIG 1 Prof. Maryam Saeedifard, IEEE President Saifur Rahman, Prof. Kamal Al-Haddad, and IEEE President-Elect Tom Coughlin (from right to left).

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a senior Canada research chair, École de Technologie Supérieure, Montréal, QC, Canada, for contributions to power electronics converters for p ower q u a l it y a nd i ndu s t r i a l applications. The IEEE Edison Medal recipient Matsunami was honored for pioneer i ng cont r ibut ion s to t he development of SiC material and its

applications to electronic power devices. While the IEEE Medal for Environmental and Safety Technolog ie s wa s joi nt ly re ceived by researchers Tatsuhiko Fu jihira, David James Coe, and Gerald Deboy for contributions to the concept and realization of superjunction power devices that significantly improve power efficiency.

The evening culminated with the Honor s C er emony d i n ner a nd gala—hosted by IEEE President and CEO Saifur Rahman and IEEE P resident-Elect Tom Coug h l i n, where the recipients were celebrated and given the chance to make an acceptance speech, many of w h ic h we r e i n s pi r i n g a nd memorable.

by Ashok Bindra

Congratulations to the 2023 PELS Award Winners!

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n keeping with the tradition of recognizing technical professionals whose exceptional achievements and outstanding contributions have made a lasting impact on technology, society, an Srinivas Bhaskar Karankid the engineering profession, IEEE Power Electronics Society (PELS) has announced the winners of its 2023 PELS awards. The winners were announced by the 2023 IEEE PELS Aw a r d s C h a i r Andreas Lindemann of Universitaet Magdeburg, Germany. The IEEE PELS R ich a rd

M . Ba s s Out st a nd i n g You n g Power Elect ron ic s En g i neer Award went to Minjie Chen for contributions to the modeling, design,

and application of high-performance power electronic systems. The recipient of the IEEE PELS R. David Middlebrook Achievement

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Award was Marco Liserre for modelling and control of power converters in reliability and stability studies. The IEEE William E. Newell Power Electronics Award was presented to Dragan Maksimovic for contributions to digital control, model i ng, a nd topolog ies of switched mode power supplies. The IEEE McMurray Award for Industry Achievements in Power Electronics was given to Shinzo Tamai for contributions to high-power applications of threelevel neutral-point-clamped converters in industry and utilities. The winner of the IEEE PELS H a r r y A . O wen , Jr. D i st i n guished Service Award was Alan Mantooth for two decades of distinguished service and leadership in technical operations, standards, publications, mentorship activities, and as society president. The IEEE PELS Young Profess i o n a l E xc e p t i o n a l S e r v i c e Award was presented to Harish K rishnamoor thy for exceptional ser v ice t o t he I EEE Power Electron ics Societ y th rough

outstanding contributions to chapters, committees, conferences, and TPEL editorial board. The IEEE Modeling and Cont rol Te c h n ic a l Ac h ievement Award was given to Josep M. Guerrero for contributions to modelling and control of power electronics based microgrids. The winner of the IEEE PELS Award for Achievements in Power Electronics Education was Jacobus D. Van Wyk for pioneering contribu t io n s t o p ower ele c t r on ic s education of power electronics experts across the world over five decades. The IEEE PELS Sustainable E n e r g y S y s t e m s Te c h n i c a l Achievement Award was given to Hua Geng for contributions to control of renewable energy power conversion systems. The IEEE PELS Vehicle and Transportation Systems Achievement Award was received by Chunting Mi (Chris) for contributions to the advancement of battery management systems and of electric vehicle charging.

The winner of the Outstanding Achievement Award on Aerospace Power was Don Ta n for impactful contributions and visionary leadership in advancing space power electronics and systems. The IEEE Power Electronics Emerg i ng Tech nolog y Awa rd went to Leon Tolbert for technical leadership and innovation in developing adva nced gate d r ives for SiC devices. The recipient of the IEEE PELS Technical Achievement Award for Integration and Miniaturization of Switching Power Converters was Zheng (John) Shen for contribution to the development of MHz-frequency power MOSFET Technology for ultrahigh density power converters. The Power Electronics Society Best Chapter Award was presented to IEEE PELS IES Delhi Chapter. The Power Electronics Society Best Student Branch Award was given to Sri Sai Ram Engineering Col lege, Chen na i, Ta m i l Nadu, India, PEL35.

by Dong Jiang, Boyang Li, and Wei Sun

IEEE PELS Wuhan Chapter Celebrates PELS Day

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n 18 June 2023, IEEE Power Electronics Society’s (PELS) Wuhan Chapter celebrated PELS Day at the Huazhong University of Science and Technology Digital Object Identifier 10.1109/MPEL.2023.3303129 Date of publication: 26 September 2023

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(HUST), Wuhan, China. The forum brought together members of the IEEE PELS, the IEEE PELS Wuhan Chapter, faculty members and students of HUST, and other institutes in the Wuhan area, renowned scholars, and experts from power electronics industry. More than 100

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people attended this event to celebrate IEEE PELS Day (Figure 1). The forum began with the invited lecture from Prof. Jian Sun from Rensselaer Polytechnic Institute, Troy, NY, USA, who presented on the topic “Data Center Power System Stability.”

FIG 1 More than 100 people attend the PELS Day event in Wuhan, China.

After the invited lecture, four industrial speakers gave presentations. The first industry speaker was Dr. Chu Xu from United Imaging Medical Technology, who presented on the topic “Application of Power Conversion Technology in Large Medical Equipment.” The second industry speaker was Dr.  Lu  Zhengang from State Grid Corporation’s Intelligent Grid Research Institute, who presented on the topic “Novel Flexible AC T ra nsm ission Tech nolog ies



Supporting Large-scale New Energy Delivery.” The third industry speaker was Dr. Zhu Wei from Shanghai Nancal Electric Company, Ltd., who presented on the topic “Key Technologies for Large-scale Electrical Drive System s.” T he fou r t h i ndu st r y speaker was Dr. Shen Jie from LEADRIVE Technology, who presented on the  topic “Development Trends in Power Electronics Technology from the Perspective of Vehicle Electrification Control.”

September 2023

The successful convening of this IEEE PELS Day forum has effectively promoted academic exchanges and technological advancements in the field of power electronics. The attending representatives shared the latest research achievements and industry development trends, contributing to the innovative application of power electronics technology, and making greater contributions to the development of the power electronics field in China and globally.

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by Srinivas Bhaskar Karanki

IIT Bhubaneswar India Organizes First Ph.D. Summer School

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rom 10 to 14 July 2023, the School of Electrical Engineering, Indian Institute of Technology Bhubaneswar, India, in collaboration with the IEEE Power Electronics Society (PELS), organized its first Ph.D. summer school for doctoral scholars with power electronics background. The objective is to encourage brilliant young minds to build careers in areas of electrical engineering, including power systems, renewable integration, smart grids, and control systems. About 97 Ph.D. scholars working in the area of power electronics and its applications, came from various institutes in India to attend the Ph.D. summer school (Figure 1). The inaugural session was conducted on 10 July from 9:30 to 10:30 AM,

which was attended by Prof. A. K. Tripathy, former CPRI director, as the chief guest. The event also witnessed video address by Prof. Brad Lehman, president of IEEE PELS, Prof. Liuchen Chang, immediate past president, who presented the State of PELS to the audience in virtual mode. Prof. Mario Pacas, VP global relations highlighted various awards and funding opportunities in IEEE PELS. Prof. Sanjib Kumar Panda, R-10 reginal chair, presented insight into the activities of Region 10. Likewise, Dr. Srinivas Bhaskar Karanki, India-Liaison described the objectives of the Ph.D. school and the benefits of joining IEEE PELS to the participants. In total, 14 sessions were conducted, which includes talks by the

experts from academia and industry, Ph.D. talks, and hand on training. In addition, 13 Ph.D. scholars presented their work to the peers, which was followed by very interactive Q& A session. Plus, fou r h a nd s on t r a i n i n g on F P GA s , STM32, and C2000 microcontroller were organized as par t of Ph.D. summer school. Furthermore, 10 lectu res were del ivered, wh ich includes talks by Prof. A. K. Tripathy, Prof. Deepak Raj Diwan, Prof. Sanjib Panda, Dr. Kaushik Basu, Dr. Santanu Kapat, Dr. Krishna Dora, Dr. Subham Sahoo, Mr. Kedarnath, Mr. Kamaldeep, and Dr. Srinivas Bhaskar Karanki. All the participants were shown the laboratory facilities in IIT Bhubaneswar, followed by a specia l ses sion on

FIG 1 Attendees at IIT Bhubaneswar India’s first Ph.D. summer school for doctoral scholars.

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dSPACE, arranged by Ph.D. scholars of IIT Bhubaneswar. The welcome address was given by Prof. Dehong Xu, VP Membership. The participants were provided with bags and writing materials. Mr.

Ranjan, IEEE Bhubaneswar student branch chapter chair, Mr. Sanjib, Mr. Rav i Ra nja n, M r. P rag ya Na nd Singh, a nd other scholars were actively involved in the entire program successfully. The feedback

from the pa r ticipa nts wa s ver y much positive and many institutes/ chapters have shown interest in conducting the next edition of the Ph.D. su m mer school i n t hei r respective location.

by Poojasree Kubendra Raja

IEEE PELS SBC at SJCE Hosts Distinguished Lectures

T

 o celebrate PELS Day 2023, the IEEE Power Electronics Society (PELS) Student Branch Chapter (SBC) at St. Joseph’s College of Engineering (SJCE) hosted multiple distinguished lectures. The first one took place on 10 June and the topic “Career in Power Electronics and How to Master a Craft in Co re E ng i ne e ri ng ” was presented by PELS Distinguished L e c t u r e r ( D L ) D r. Brij Singh, John Deere Technical Fellow. On 13 June, the second presentation was by PELS DL Dr. Keyue Ma Smedley on the topic “Exploration at the Confluence of Three Major Power Electronics Branches.”

Additionally, the IEEE PELS SBC at SJCE hosted three online competitions that had a gaming theme focused on power electronics. On 20 Ju ne, the SBC hosted a power

electronics exhibition, which helped student attendees to understand power electronics’ high level of impact through its applicationoriented focus.

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by Rajesh M. Pindoriya

IEEE PELS/IES Delhi Chapter Co-hosts Event for Children

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n 29 April 2023, the IEEE Power Electronics Society (PELS)/Industrial Electronics Society (IES) Delhi Chapter along with the IEEE Power and Energy Society (PES)/Industry Applications Society (IAS) Delhi Section Chapter, IEEE IAS/PES Student Branch Chapter (SBC) at the Thapar Institute of Engineering and Technology (TIET) in Patiala, Pratigya Society TIET, and IEEE Students (SPAx) Committee cohosted an event with the theme “Awareness of Renewable Energy Sources for School Kids.” The event was held at the TIET and was

attended by over 50 students ranging from classes 1 to 4 from nearby schools. To begin the event, a presentation from Dr. Ra jesh Pindor iya (IEEE IAS Chapter Area chair, R10 East and South Asia) focused on renewable energy sources, including solar, wind, hydro, geothermal, and biomass (Figure 1). The students viewed multiple videos and pictures related to these renewable energy sources, which helped them to understand the concepts better. After the presentation, the students participated in a coloring competition. Each student received a

FIG 1 Dr. Pindoriya giving his presentation to the students.

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sheet that had a drawing related to renewable energy printed on it and were encouraged to color the picture in a way that showcased the importance of renewable energy sources. Once the students completed their coloring, the winners of the competition were announced and received a memento, a certificate, and a school bag. The IEEE PELS/IES Delhi Chapter and the other sponsoring groups are pleased with the event’s success and are glad to raise awareness a mong t he st udent s about t he importance of renewable energy sources.

by Ashutosh Yadav

IEEE PELS SBC at HBTI Organizes PELS Day Event

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n 20 June 2023, the IEEE PELS Student Branch Chapter (SBC) at the Harcourt Butler Technological Institute (HBTI) in Kanpur organized an event to celebrate PELS Day 2023. To begin the day, there were three talks presented by different experts in the power electronics field. The first one was delivered by Dr. Sanjeev Pannala (assistant research professor at the Energy System Innovation Center, USA) and had the theme “Power System Operat iona l Cha l lenges w it h Inver ter-Based Resources.” This present at ion shed l ig ht on t he

complexities faced when integrating renewable energy resources into the power grid. The second one was had the theme “Applications of Power Electronics in the Field of Renewables and EVs: RealTime Studies” and was presented by Dr. Gururaj Mirle Vishwanath (Indian Institute of Technology, Kanpur). The talk included valuable insights into the practica l applications and real-time studies in the domains of renewable energy and electric vehicles (EV). The last presentation wa s by Dr. Sa njiv Kumar (Harcourt Butler Technical University, Kanpur) on the topic

“Recent Trends and Applications of Power Electronics.” This presentation showcased the cutting-edge developments in the field. Once the presentations were completed, a quiz and poster-making competition focusing on the industrial applications of power electronics were held to allow participants to demonstrate the knowledge they gained from the talks (Figure 1). The IEEE PELS SBC at HBTI in Kanpur is pleased with the success of t he event a nd wou ld l ike to thank the presenters for coming and giving presentations to those in attendance.

FIG 1 Participants of the poster-making competition

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by Moiz Ahmad

IEEE PES/PELS Islamabad Section Chapter Organizes Interactive Workshop

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n 6 June 2023, the IEEE Power and Energy Society (PES)/Power Electronics Society (PELS) Islamabad Section Chapter organized an interactive workshop with the theme “Arduino Experience” at Comstats University in Islamabad, Pakistan. The event allowed participants to delve into the world of electronics and programming through the Arduino platform and emphasized the importance of experimentation and exploration. The workshop began with an introduction to the fundamental components of A rdu i no, wh ich equipped the participants with the needed knowledge to embark on a creative journey (Figure 1). Subsequently, experienced instructors guided the participants through a series of engaging and hands-on Digital Object Identifier 10.1109/MPEL.2023.3303119 Date of publication: 26 September 2023

FIG 1 Students listening to a presentation about the Arduino platform.

activities, which included setting up the development environment and writing code using the Arduino programming language. Attendees were able to build circuits, connect various sensors and actuators, and witness the results of their creations. They were also able to collaborate and exchange ideas with fellow Arduino enthusiasts,

which allowed attendees to learn from each other’s experiences. The event had over 40 participants and the IEEE PES/PELS Islamabad Section Chapter is pleased with the success of providing a platform for the attendees to unleash their creativity, discover their passion for technology, and join a supportive community of like-minded enthusiasts.

by Mahmadasraf Mulla

IEEE PES/IAS/PELS Gujarat Section Chapter Organizes Expert Talk

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o celebrate PELS Day 2023, the IEEE Power and Energy Society (PES)/Industry

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Applications Society (IAS)/Power Electronics Society (PELS) Gujarat, India, Section Chapter hosted a hybrid expert talk on 20 June 2023. The presenter was Dr. Sanjib Kumar Panda (associate professor at the

IEEE POWER ELECTRONICS MAGAZINE z September 2023

National University of Singapore) and his theme was “A Plug and Play Operational Approach for Implementation of an Autonomous Microgrid System.” This event was organized in co-operation the Electrical

FIG 1 In-person attendees of the event.

Engineering Society (EES) and the Sardar Vallabhbhai National Institute of Technology (SVNIT). Before beginning his presentation, Dr. Panda highlighted the importance, benefits, and other activities of the IEEE PELS. Dr. Panda then

talked about the responsive grids for future energy systems and the role of energy control centers in grid interconnection with other microgrids. This session focused on sustainable developments that meet the needs of the present generation without

compromising the ability of future generations being able to meet t hei r ow n needs. Additionally, Dr. Panda introduced t he plu g- a nd - pl ay autonomous grid system and explained the concept with different case studies that were supported with experimental results. After the presentation, a questionand-answer session was held where the students, research schola rs, a nd faculty members could ask questions to Dr. Panda. The IEEE PES/IAS/ PELS Gu ja r at S ect ion Chapter would like to thank Dr. Panda for taking the time to give his present a t ion t o a l l of t he a t t endee s (Figure 1).

by Eric Meier

IEEE PI2 Joint Chapter Hosts PELS Day Celebration

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n 22 June 2023, the IEEE Power and Energy Society (PES)/Power Electronics Society (PELS)/Industrial Electronics Society (IES)/Industry Applications Society (IAS)/Product Safety Engineering Society (PSES) (PI2) Joint Chapter hosted a celebration in honor of PELS Day 2023. This event also included the Central Texas Section Young Professionals affinity group.

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FIG 1 Attendees at the Austin, TX, USA event on 22 June 2023.

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During the event, attendees were able to network with each other while enjoying on-site food trucks

a nd dr inks in Austin, TX, USA (F igure 1). The IEEE PI2 Joint Chapter also created an IEEE and

engineering-themed trivia contest that allowed participants to compete for prizes.

by Jinning Zhang

Prof. Panda Presents IEEE Distinguished Lecture at the University of Leicester, U.K.

O

speaker. Dr. Panda offered an insightconnected inverter and single-phase n 19 July 2023, Dr. Sanjib ful orientation on power converters series connected inverter, were anaKumar Panda, an associate for microgrid applications, and it was lyzed and compared for microgrid professor and the director of well received by the students and applications to interface the utilitythe power and energy research at the researchers at the University of grid and loads. The lecture was folNational University of Singapore Leicester. lowed by a lively and engaging Q&A (NUS) presented the IEEE Distin session between the audience and the guished Lecture (DL) titled “Renewable Energy Source Integration to Microgrids” at the School of Engineering, University of Leicester, U.K. (Figure  1). The event was organized as a hybrid event with 18 in-person attendees and 41 online participants. The DL talk provided a detailed introduction to responsive grid 2.0 in Singapore and identified the challenges and opportunities for the evolving power grid, e.g., decentralized/distributed energy generation, diversified nature of loads, and bidirectional power and information flow. Following that, power converters with their control strategies, such as the s i n g le - ph a s e p a r a l lel FIG 1 Prof. Sanjib K. Panda presenting the IEEE DL talk at the University of Leicester, U.K.

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Event Calendar

2023 24–26 September Miami, FL, USA IEEE Design Methodologies Conference (DMC) https://attend.ieee.org/dmc-2023/

27–29 September Hannover, Germany International Workshop on Power Supply On Chip (PwrSoC)

28 November–1 December Chiang Mai, Thailand EEE Transportation Electrification Conference and Expo, AsiaPacific (ITEC Asia-Pacific) https://itec-ap2023.com/

4–6 December Charlotte, NC, USA IEEE 10th Workshop on Wide Bandgap Power Devices & Applications (WiPDA)

http://pwrsocevents.com/

https://wipda.org/

12–15 October

10–13 December

Radnor, PA, USA IEEE Global Humanitarian Technology Conference (GHTC) https://ieeeghtc.org/

16–18 October Karlsruhe, Germany 8th IEEE Workshop on the Electronic Grid (eGRID) https://www.egrid2023.com/index.php

26–28 October Monterrey, Mexico International Symposium on Electromobility (ISEM)

29 October–2 November

Bhubaneswar, India IEEE 3rd International Conference on Smart Technologies for Power, Energy and Control (STPEC) https://event.kiit.ac.in/STPEC2023/

14–16 December Guwahati, India 11th National Power Electronics Conference (NPEC) https://www.npec2023.com/

17–20 December Trivandrum, India IEEE International Conference on Power Electronics, Smart Grid, and Renewable Energy (PESGRE)

Nashville, TN, USA IEEE Energy Conversion Congress and Exposition (ECCE)

https://pesgre2023.org/

https://www.ieee-ecce.org/2023/

2024

10–13 November

25–29 February

Guangzhou, China IEEE 2nd International Power Electronics and Application Symposium (PEAS) http://peas.cpss.org.cn/

15–17 November Auckland, New Zealand IEEE Fifth International Conference on DC Microgrids (ICDCM) https://www.ieee-icdcm.org/

Long Beach, CA, USA IEEE Applied Power Electronics Conference and Exposition (APEC) https://www.apec-conf.org/

24–27 June Lahore, Pakistan IEEE Workshop on Control and Modeling for Power Electronics (COMPEL)

20–23 November Sydney, Australia IEEE International Future Energy Electronics Conference (IFEEC) https://ifeec2023.org/

26–29 November Florianopolis, Brazil IEEE 8th Southern Power Electronics Conference (SPEC)

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White Hot  

(continued from page 104)

The specific task was to measure the output voltage regulation characteristic at various different input voltages. This required taking thousands upon thousands of measurements. To sit at the bench make this measurements by hand while entering the data in a spreadsheet would have taken several weeks while also likely having a significant number of data entry errors. To handle this job I bought a copy of Labview with the idea of automating the task. I was thinking that the graphical programming environment would be easy to master. I was wrong. Labview is an excellent tool and loved by many. But, it just did not click for me. I struggled with automating these measurements but the clock was ticking. I ended up hiring a local Labview consultant to write the application to run the instruments and collect the needed data. Even with this highly automated process it took me almost two weeks to finish the job. I kept up my Labview maintenance for a few years. Once in a while I would open it up and try to program some simple tasks such as controlling a power supply or taking readings from a digital multimeter. It never clicked for me and eventually I stopped paying for the maintenance. In the past several months I have been working on learning Python with the goal of doing the same kind of automated measurements. I have taken a course on Python through Coursera to learn the basics. I have been working on tasks like writing and reading data from Excel workbooks. I have been exploring the use of tools like PyVISA to interface to instruments using a USB to GPIB adapter. I can report some progress, but I still have a ways to go to fully master these tools. I have come to have a real appreciation for Python. I now understand why I see so many examples of people doing rather adva nced



simulations and animations, even for power electronics. I think the key is the wide range of libraries that have been developed for Python. Initially, I was wondering about these libraries and their long-term support, given they are generally open-source projects. However, I realized that even with paid software there is no guarantee of long-term support. I have a lot of older Microsoft Word and PowerPoint files that the current version of Office will not open. So my fears of support for Python libraries were misplaced. Another skill that we now need is video production. In this age of YouTube and TikTok, video has become a dominant means of communication. As I teach my project lab students, if you don’t have the skills to communicate your ideas and work product to your peers, your management, and your customers then you have nothing. Today, we all have the hardware and software tools we need to produce videos to tell our stories. Every mobile phone now has a very good video camera. High quality webcams are ridiculously inexpensive. Here are a couple of ways that I use videos, other than formal lectures and web presentations, to enhance communication. One is that when working on a problem in the lab or otherwise, there is nothing like a video of an oscilloscope waveform or even meter readings to communicate the issue. As web chair of IEEE APEC, right before the conference there was a problem with the APEC website on mobile devices. I was able to use my webcam to record myself accessing the web site on my mobile phone. I sent the video to the professional web developer contracted to support the APEC website to show the problem. A few seconds of video was all that was needed to show the issue. If I had tried to describe the issue in a phone call or an email message it would have been far harder to communicate the problem.

September 2023

We all have meetings where we need to discuss a situation or problem and make some decisions about actions to be taken. Often much of the meeting time is taken up by a presentation of the issue to be discussed. I have taken to making videos of the material to be presented. I distribute the slides and a link to the video a few days ahead of the scheduled meeting. People can then review the slides and watch the video presentation at their convenience. Then, when we meet, we spend a few minutes reviewing the presentation and answering questions. We can then get to the real discussions and making the needed decisions. This either greatly reduces the meeting time or allows for fuller discussion of the issues. There are an endless variety of audio and video editing tools, free and commercial, available. A nd example of a free, but very high quality and powerful audio tool, is Audacity. My favorite video tool is commercial software, Camtasia. I find it easy to use for video editing and basic audio editing. For more complex audio editing, I sometimes use Audacity but I also use commercial software, Soundforge, as it has a very good noise reduction plugin. There are many choices of video and audio editing tools. Which one you use is not all that important. Try several. Find one you like and can use effectively and get busy improving your professional communications with video. For making good quality videos one also needs a bit of hardware. Mobile phones today have excellent cameras. You will also need a good webcam, but these are inexpensive. You will also need various stands to hold your phone and web camera. These can be anything from small tripods for the desktop to full camera tripods for long reach adjustable arms. Lighting is also important. Nothing ruins a video faster than it being dark or covered by shadows. It

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is worth investing in some simple lights like a small ring light or panels of LEDs. It is also worth buying lights that can allow varying both their intensity and light color (from bright daylight to warm incandescent like color). Start simple and cheap. Buy or borrow the simplest stands and lights and experiment with them. Find what works for you before investing in higher quality pro-grade equipment. You are even likely to find that the basic, inexpensive stands and lights work just fine. Those that know me personally know that I love being a power electronics engineer. I love the challenge of having to know so much about so many topics to be successful. Even so I find that I need to keep learning more. Not just more about the technical details of some new topology or a

new generation of power devices, but also things like build up my skills in programming and video production. As I tell my students, to be successful learn something new every day. Disclaimer: All of the products I mentioned, hardware or software, are tools I use in my everyday work. Commercial tools were purchased by me with my own funds. None were provided to me by the manufacturers. I have not, and will not, receive any consideration for mentioning these products. In fact, the manufacturers or producers of these products will not even know of the mention until this column is published.

About the Author Robert V. White (bob.white@ieee. org) has more than 40 years of industry experience as a power electron-

ics engineer. He has worked in product design, systems and applications engineering, technical marketing, and technology development. He has been an active volunteer with the IEEE Power Electronics Society, serving several years on the Administrative Committee, two terms as the Technical Vice President, and as the Chapter Chair. He received the B.S.E.E. degree from the Massachusetts Institute of Technology and the M.S.E.E. degree from Worcester Polytechnic Institute. He is currently pursuing the Ph.D. degree in power electronics with the University of Colorado, Boulder, CO, USA. Presently, he is the Chief Engineer of Embedded Power Labs, Highlands Ranch, CO, USA, a power electronics consulting company. He is a Life Fellow of the IEEE.

Advertisers Index

The Advertisers Index contained in this issue is compiled as a service to our readers and advertisers: the publisher is not liable for errors or omissions, although every effort is made to ensure its accuracy. Be sure to let our advertisers know you found them through IEEE Power Electronics Magazine. SALES CONTACTS Kathy Naraghi WelComm, Inc. 13223-1 Black Mountain Road, Suite 434 San Diego, CA 92129 Telephone: +1 858 279 2100 [email protected]

PAGE#

COMPANY

URL

PHONE

11

Acopian Technical Company

www.acopian.com

+1 610 258 5441

91

Advanced Test Equipment Corp.

www.atecorp.com

+1 800 404 ATEC

87

Applied Power Systems, Inc.

www.appliedps.com

+1 516 679 2686

72

Astrodyne TDI

www.astrodynetdi.com

93

CalRamic Technologies LLC

www.CalRamic.com

+1 775 851 3580

Cov 3

Chroma Systems Solutions

www.chromausa.com

+1 949 600 6400

5 Coilcraft

www.coilcraft.com/tools

70

Dean Technology

www.deantechnology.com

13

Electronic Concepts

www.ecicaps.com

71

Fuji Electronic Corporation

americas.fujielectric.com/ieee-power

83

ICE Components

www.icecomponents.com

12

Imperix Power Electronics

www.imperix.com

6,66

ITG Electronics

www.ITG-Electronics.com

9

Kendeil S.r.l.

www.kendeil.com

74 KYOCERA-AVX

www.kyocera-avx.com

3

Magna Power Electronics

www.magna-power.com

10

Magnetic Metals Corp.

www.MagneticMetals.com

66

Magnetics, Division of Spang & Co.

www.mag-inc.com

Cov 4

MATHWORKS, Inc.

mathworks.com/pec

74 Mersen

+39 0331 786966

+1 856 964 7842

ep.mersen.com

Cov 2

Mitsubishi Electric US,



Semiconductor Device Div.

meus-semiconductors.com

65

New England Wire Technologies

newenglandwire.com

89 NORWE

norwe.com

79

www.omicron-lab.com/

Omicron Lab

+1 972 248 7691

+1 603 838 6624



training-events

73

Payton Planar Magnetics

www.PaytonGroup.com

+1 954 428 3326

70

PICO Electronics Inc.

picoelectronics.com

+1 800 431 1064

7

Plexim GmbH

www.plexim.com

69

Premier Magnetics

www.premiermag.com

77

RTDS Technologies, Inc.

rtds.com/webinars

81

Triad Magnetics

www.triadmagnetics.com

+1 949 452 0511

+1 951 277 0757

Digital Object Identifier 10.1109/MPEL.2023.3307231



September 2023

z IEEE POWER ELECTRONICS MAGAZINE

103

White Hot

by Robert V. White

More Stuff to Know

F

or one to be a good power electronics engineer one must know a lot about a lot. Power electronics engineers obviously have to know about power conversion circuits and topologies. But, we must also have a basic understanding of semiconductor physics to truly understand how our power switching devices work and how to make best use of them. We must have a deep understanding of magnetics and magnetics devices. We have to know about all different types of capacitor technologies, the characteristics of each, and where each fits in our power converter designs. We must know analog and digital circuit design to create not just analog controllers but all sorts of monitoring and protection circuitry. We have to know a fair amount about control theory to properly design our controllers. We have to know product safety standards and practice. We have to know EMI standards and how to control unwanted electromagnetic emissions both by design and by mitigation after the fact. We have to understand heat transfer and thermal management. I believe that good power electronics engineers must have a greater breadth and depth in more technical areas than some other engineering specialties.

Digital Object Identifier 10.1109/MPEL.2023.3299938 Date of publication: 26 September 2023

104

Even knowing all that there is more that we power electronics engineers need to know to be good at our jobs. In terms of technical skills, we all need to have some programming skills. Programming itself is a broad field. There is a big difference between writing applications that run under operating systems like Windows, MacOS, or Linux and writing firmware that runs on bare metal microcontrollers. For us as power electronics engineers we of course need to know how to use various calculation tools to solve our circuit problems. These all require some knowledge of programming. I even consider building Excel worksheets to solve design problems as a form of programming. A well-designed spreadsheet will show how the problem is solved, step by step, with the same kind of full commenting that one expects when wr iting C la nguage code. Other tools that require programming in some form or the other include MathCAD and MATLAB. With Python being the new BASIC, I see more and more examples of people writing Python scripts to solve engineer ing problems. More on Python in a bit. We all also now need to know the basics of microcontrollers and embedded systems programming to migrate our analog monitoring a nd prot ec t ion ci rc u it s i nt o a microcontroller. We might even

IEEE POWER ELECTRONICS MAGAZINE z September 2023

have to have more than working knowledge of digital control and its practical deployment in microcontrollers, digital signal processors (DSPs), and FPGAs. Today, if you are a skilled power electronics engineer and also highly skilled a nd prof icient at prog ra m m i ng controls for complex power electronics, such as grid interfacing i nver ter s, you ca n pret t y much “write your own ticket” when it comes to finding a job with much higher than average compensation. I admit that I am not, and never have been, a wizard at programming. I keep working at improving my programming skills and today I rate myself as adequately proficient. With engineering calculation tools like I consider myself very skilled. When it comes to embedded programming I can write good functioning code that works. However, I a m not the person to wr ite a n embedded application that is running a three phase rectifier while also driving an LCD display and providing a bluetooth interface. I freely admit that is beyond my skill set and experience. Recently, I have been working on learning Python with a specific use in mind. Several years ago I had an expert witness consulting job where I had to characterize many different boa rd mount dc– dc conver ters. (continued on page 101)