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Challenge to 99.9% Electric Power Conversion Efficiency for Inverter in a Few kW Power Range
Prof. Atsuo Kawamura
Yokohama National University, Japan
IEEE Fellow

Abstract: Extremely high electric power conversion efficiency over 99 % has been challenged by the authors group and several results will be summarized in this invited talk.

First in the field of the dc/dc electric power conversion, several resonant switching techniques among others were proposed by authors group and 99 % efficiency was achieved in a very high power density using Si devices.

Second, a new concept of a partial boost circuit for dc/dc converter was introduced and over 99.5% efficiency was verified in the power range between 10kW and 100 kW using SiC devices. This topology is named to be HEECS chopper by author’s group. Three examples will be presented. One is for EV application and the second is for FCV and the third may be for renewable energy application.  Also an experience of 3.3kV SiC device use in DAB will be presented.

Third this concept was extended to the partial power conversion principle and it is applied to dc/ac electric energy conversion i.e. inverter. Aiming only at a very high efficiency and discarding the high power density, 99.70% efficiency around 2 kW power range was experimentally measured as tentative data using a circuit topology of combination of a HEECS chopper and an unfolding inverter with SiC devices. Loss analysis of this type of power conversion will be presented from the view point of further loss reduction, including several kinds of loss measurement for system and individual component loss measurement.

Finally applications of these power conversion techniques will be added if time is available.

Biography:  Atsuo Kawamura was born in Yamaguchi, Japan, in December 1953. He received the B.S.E.E., M.S.E.E., and Ph.D. degrees in electrical engineering from the University of Tokyo, Tokyo, Japan, in 1976, 1978, and 1981, respectively.

In 1981, he was with the Department of Electrical and Computer Engineering, University of Missouri, Columbia as a Postdoctoral Fellow, where he was an Assistant Professor from 1983 to 1986. Since 1986, he has been with the Division of Electrical and Computer Engineering, Yokohama National University, Yokohama, Japan, where he was first an Associate Professor and later became a Professor in 1996. He served as a dean of College of Engineering Science and Graduate School of Engineering from 2013 to 2015. He has become Professor Emeritus in 2019, and now is a professor of endoed chair ( Power Electronics) at the same university. His research interests include power electronics, digital control, electric vehicles, robotics, train traction control, etc.

Dr. Kawamura is a member of the Institute of Electrical Engineers of Japan (IEE of Japan), Robotics Society of Japan, and several other organizations. He was the conference Chairperson of IPEC-Sapporo-ECCE-Asia in 2010 and a president of IEE of Japan/IAS (Industry Application Society) in 2012-2013. He received several awards including the IEEE IAS Transactions Prize Paper Award in 1988, the Prize Paper Award of IEE of Japan in 1996, IEEE IES Transactions Best Paper Awards in 2001 and 2002 , and EPE-PEMC Award in 2008.