1. State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Shapingba District, Chongqing 400044, China
2. FREEDM Systems Center, Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27606, USA
3. College of Engineering and Technology, Southwest University, Beibei District, Chongqing 400715, China