Tutorial Title: Design and Optimization of High-Power High-frequency Transformers for Solid-State Transformers

Solid-state transformers (SST) are widely applied in the AC/DC hybrid distribution networks to implement energy routing and to increase efficiency and power density. Isolated DC-DC converters are the key stages of the SSTs, which require high-power high-frequency transformers to provide the proper voltage transfer ratio and to help realize soft switching. The design and optimization of high-power high-frequency transformers are presented in this lecture. Two major solutions of high-power high-frequency transformers, namely litz-wire transformers and planar transformers, are investigated and compared, including the design and applications. The loss modeling methods are proposed, including that of winding losses for both litz wires and PCB windings, and that of core losses, in particular the eddy losses. The insulation design and the magnetic integration design are also analyzed for litz-wire transformers and planar transformers respectively. In addition, the optimization methods of high-power high-frequency transformers are introduced, along with novel methods based on intelligent algorithms.

Presenters’  Information

Kai Sun, Tsinghua University

Kai Sun received the B.E., M.E., and Ph.D. degrees in electrical engineering from Tsinghua University, in 2000, 2002, and 2006, respectively. He joined the faculty of Electrical Engineering, Tsinghua University, in 2006, where he is currently a Tenured Associate Professor (Research Professor). From Sep 2009 to Aug 2010, he was a Visiting Scholar at Department of Energy Technology, Aalborg University, Aalborg, Denmark. From Jan to Aug 2017, he was a Visiting Professor at Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Canada. His research interests include power electronics for renewable generation systems, microgrids, and energy internet.

Dr. Sun serves as an Associate Editor for IEEE Transactions on Power Electronics, IEEE Journal of Emerging and Selected Topics in Power Electronics, and Journal of Power Electronics. Dr. Sun served as the TPC Vice Chair of IEEE ECCE2017 and IEEE ECCE-Asia2017, the Organization Committee Chair of IEEE eGrid2019, and the Publicity Chair of IEEE ECCE2020. He also served as the General Co-Chair of 2018 International Future Energy Challenge (IFEC2018). Dr. Sun serves as PELS Asia Pacific Regional Vice Chair, PELS Beijing Chapter Chair and PELS Electronic Power Grid Systems Technical Committee (TC8) Secretary. He was a recipient of Delta Young Scholar Award in 2013, and Youth Award of China Power Supply Society (CPSS) in 2017, and IEEE Transactions on Power Electronics' Outstanding Reviewers Award in 2019.

Presenters’  Information

Zheyuan Yi, Tsinghua University

Zheyuan Yi received the B.S. degree in electrical engineering from Tsinghua University, Beijing, China in 2019. She is currently working toward the Ph.D. degree at Department of Electrical Engineering, Tsinghua University.

Her research interests include design and optimization of high-power high-frequency transformer and design of isolated bidirectional DC-DC converter.