Honggang Sheng
Honggang Sheng received the B.S. degree from
Xi'an Jiaotong University, Xi'an, China, in 1998, the
M.S. degree from South China University of Technology, Guangzhou, China, in 2003, and the Ph.D.
degree from Virginia Polytechnic Institute and State
University (Virginia Tech), Blacksburg, VA, in 2009,
all in electrical engineering.
He was a Research Assistant with the Center for
Power Electronics Systems (CPES) at Virginia Tech
during his Ph.D. study. From 2009 to 2011, he was a
Senior Application Engineer with Monolithic Power
Systems, San Jose, CA. In 2011, he joined Google, Mountain View, CA, as a
Power Engineer for the Data Center. His research interests include topologies,
control and modeling, resonant converters and power devices.
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Fault detection and protection is an important design aspect for any power converter, especially in high-power high-voltage applications, where cost of failure can be high. The three-level dc-dc converter and its varied derivatives are attractive topologies in high-voltage high-power converter applications. The protection method can not only prevent the system failure against unbalanced voltage stresses on the switches, but also provide a remedy for the system as faults occur and save the remaining components. The three-level converter is subject to voltage unbalance in certain abnormal conditions, which can result in switch overvoltage and system failure. The reasons for the unbalanced voltage stresses are fully investigated and categorized. The solutions to each abnormal condition are introduced. In addition to the voltage unbalance, the three-level converters can be protected against multiple faults by the proposed protection method through monitoring the flying capacitor voltage. Phenomena associated with each fault are thoroughly analyzed and summarized. The protection circuit is simple and can be easily implemented, while it can effectively protect the three-level converters and its derivatives, which has been verified by the experiment with a three-level parallel resonant converter.
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