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Semiconductor Galvanic Isolation Based Onboard Vehicle Battery Chargers

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Semiconductor Galvanic Isolation Based Onboard Vehicle Battery Chargers Semiconductor Galvanic Isolation Based Onboard Vehicle Battery Chargers DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Chengcheng Yao Graduate Program in Electrical and Computer Engineering The Ohio State University 2018 Dissertation Committee: Dr. Jin Wang, Advisor Dr. Longya Xu Dr. Yuan Zhang Copyright by Chengcheng Yao 2018 Abstract Power converters with galvanic isolation are widely used in various applications, which is also required by the industry safety standards (e.g., IEC60950 and UL2202). Traditionally, there are mainly three solutions to achieve the galvanic isolation in power converters, including the magnetic field-based isolation, electric field-based isolation, and optics-based isolation. Semiconductor-based galvanic isolation (SGI) is a paradigm shift in realizing galvanic isolation. It uses semiconductor switches’ output capacitance to isolate two sides of the circuit when the switches are off. When the switches are on, differential-mode (DM) power can still be delivered from the primary side to the secondary side circuit. It means both the common-mode (CM) current blocking and DM power delivery are handled by the semiconductor switch. This dissertation conducts a comprehensive study of the principle, safety requirements, suitable circuit topologies, the touch current issue and design guidelines of SGI based power converters. The goal is to achieve high power density, high efficiency, and valid galvanic isolation performance that meet safety standards. Onboard vehicle battery charger is selected for the target application. The discussion starts with a review of safety standards on galvanic isolation, which can be evaluated with two tests: the withstand voltage test and the touch current test. Then, principles, benefits, and challenges of the SGI technology are discussed. ii A family of SGI circuit topologies is explored. Basically, the SGI concept can be applied to most traditional inductor-based and capacitor-based circuit topologies. The developed topologies include (a) SGI based buck cell, (b) SGI based buck-boost cell, (c) SGI based boost cell, (d) SGI based switched capacitor converters, and (e) SGI based bridgeless power factor correction converters. Using onboard battery charger as an example, the selection of SGI topologies for different ac/dc power levels is discussed. The touch current issue is one of the key challenges of SGI power converters. Systematic analysis and modeling methods are proposed to predict the touch current. The analysis shows that for a given SGI topology, it is preferred to have smaller Coss and fsw to reduce the touch current. However, these constraints greatly limits the power density and efficiency of SGI power converters. TC compensation is an approach to mitigate the tradeoff between satisfying safety standards and achieving high power density and high efficiency. Several passive and active TC compensation approaches have been investigated. The passive filtering techniques are not very effective due to the low-frequency nature of the touch current. Instead, active compensation methods are far more effective. A comprehensive discussion is presented on various aspects of active compensation methods, including system architecture, TC detection, compensation current injection methods, channel sharing and the timing control. A buck-boost based distribution method with local control is presented to illustrate the design process. Several local detection and control methods are also explored to realize a local control of the TC compensation circuit so that the main controller does not need to involve in the control of the TC compensation. iii The design procedure of SGI based power converters is quite different from the traditional transformer-based isolated converters because semiconductor devices handle both DM power delivery and galvanic isolation. A systematic design approach is presented. The design of galvanic isolation and differential mode power delivery can start in parallel and but need to merge together at some point. Galvanic isolation determines the voltage rating of the main devices. It also sets a limit a switching frequency and device output capacitance if a TC compensation is not applied. DM power delivery sets the requirements of the main device on-resistance, switching losses, circuit topology, and energy storage component size. With an effective TC compensation, the switching frequency constraint can be alleviated from the touch current requirement. To validate the analysis, a 2-kW SGI based onboard battery charger is prototyped. The PFC stage is realized by a GaN-based totem-pole topology. The dc/dc stage is an SGI based 1:1 switching capacitor circuit. The system efficiency is 94% - 96%. The system is able to pass the UL2202 touch current test. The fast response of the proposed local TC control ensures user safety by initiating and stopping the TC compensation whenever it is needed. Conclusions and recommendations for future work are presented. iv Dedication This document is dedicated to my family. v Acknowledgments Foremost, I would like to express my sincere gratitude to my supervisor, Prof. Jin Wang for his patient guidance, encouragement, and advice throughout this journey. It is my privilege to join and work in his great team. Under his guidance, I have learned a lot and also got exposed to many aspects of power electronics. There are numeral takeaways from him but here I want to highlight several points that I will always remember. 1) Always think from the big picture, that’s the key to a successful engineer. 2) Always be open- minded and think out of the box. 3) Being able to explain your work clearly is equally important as doing the work itself. My thanks also go to the committee: Prof. Longya Xu, Prof. Julia Zhang, and Prof. Dr. Robert R. Seghi for their support, advice, and directions. I would also like to thank Prof. Fang Luo, Prof. Ayman Fayed, and Prof. Fusheng Wang for their advice on my research. Thanks Prof. Stephen Sebo for setting me a great example of an organized and life-long engineer. I also want to thank Dr. Chingchi Chen, Dr. Lihua Chen, Dr. Ke Zou, Dr. Xi Lu, Dr. Zhuxian Xu, Dr. Ming Su, Dr. Jun Kikuchi, Mr. Chih-Lun Wang and Dr. Dong Cao at Ford Motor Company, for their guidance and support during my internship in Dearborn, Michigan. I really appreciate the guidance, help, and opportunity from Dr. Satish Thuta, vi Mr. Mehmet Ozbek, Mr. Colin Campbell, Mr. Nick Kalayjian, Dr. Xuan Zhang, Dr. Michelle Liu, Mr. Jan Rutkjaer, Dr. Jizheng Qiu and Dr. Kia Filoof at Tesla. Thanks to Dr. Xuan Zhang, Mr. He Li, Ms. Xintong Lv, Mr. Lixing Fu, Dr. Feng Guo, Dr. Cong Li and Dr. Mark Scott for being my best support in both life and work throughout these years. Thanks for accompanying me over the years as both close friends and colleagues. I’m very grateful to them all for helping me move forward, overcome the hardships, and get through the most difficult days. I wouldn’t have made it without them. I am really grateful to be working closely with a lot of talented junior students in numerous projects. Without their support, the projects just could not be finished. Special thanks to Mr. Yue Zhang, Mr. Pengzhi Yang, Mr. Mingzhi Leng, Ms. Huanyu Chen, Ms. Zhongjing Wang, Ms. Gengyao Li, Mr. Xiaoteng He, Mr. Andong Lang, Mr. Fanbo Zhang, Ms. Chaoran Han, Mr. Hao Wen, Ms. Huwei Liu and Mr. Markus Sievers. Thanks to my friends Dr. Xiu Yao, Dr. Luis Herrera, Dr. Mohammed Alsolami, Mr. Jinzhu Li, Mr. Balaji Narayanasamy, Mr. Da Jiao, Ms. Shuang Tan, Dr. Linyu Zhu, Dr. Xiang Hao, Mr. Amol R. Deshpande, Mr. Ziwei Ke, Dr. Hao Yang, Mr. Boxue Hu, Ms. Qing Jia, Mr. Zuo Wei, Mr. Yingzhuo Chen, Mr. Karun Arjun Potty, Mr. Eric Bauer, Mr. Yousef Abdullah, Mr. Mohamed Elshaer, Mr. John A. Brothers, Mr. Ke Zhu, Mr. Lucheng Wen, Dr. Zhendong Zhang, Dr. Thomas Tsai, Ms. Pu Xu, Mr. Cong Deng, Dr. Dakai Hu, Dr. Haiwei Cai, Dr. Yu Liu, Dr. Miao Wang, Ms. Xiaodan Wang, Mr. Jianyu Pan, Dr. Feng Qi, Mr. Xiaotao Dong, Mr. Rachid Darbali Zamora, Mr. Ernest Davidson, Mr. Hanning Tang, and Mr. Jizhou Jia for sharing this journey at the Ohio State University. Thank you vii all for those joys and shared memories. I will not forget all the days I was embraced by your friendship, help, and support. I would also like to thank all the students who took ECE5047 and ECE5025 in 2016. Thank you all for making this teaching experience fun, memorable, and rewarding. I would also like to take this opportunity to thank all student council members of the Center for High-Performance Power Electronics (CHPPE). It takes some effort to initiate this platform but it takes even much more to run this organization. It’s our privilege to serve the CHPPE family. I sincerely appreciate the contribution from our faculty advisor, council president, committee chairmen and students. I own my deepest gratitude to my parents Zhili Yao and Mihui Chen. Without your love and support, I would not have been where I am today. viii Vita June 2011 .................................................B.S. Electrical Engineering, Changsha University of Science and Technology Sept. 2011 to present ...............................Ph.D. student, Electrical Engineering, The Ohio State University Publications [1] C. Yao, P. Yang, H. Chen, M. Leng, H. Li, K. Zou, M. Su, C. C. Chen, and J. Wang, " Electromagnetic Noise Mitigation for Ultra-fast On-die Temperature Sensing in High Power Modules ", IEEE Trans. Power Electron., early online access. [2] X. Zhang, C. Yao and J. Wang, "A Quasi-Switched-Capacitor Resonant Converter," in IEEE Transactions on Power Electronics, vol. 31, no. 11, pp. 7849-7856, Nov. 2016. [3] X. Zhang, C. Yao, C. Li, L. Fu, F. Guo, and J.
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