1. School of Electrical Engineering, Hebei University of Technology, Tianjin 300401, China
2. People Electric Appliance Group Co., Ltd., Wenzhou 325604, China
3. Technology Institute of Wenzhou University in Yueqing, Wenzhou 325699, China
4. Engineering Research Center of Low-Voltage Apparatus of Zhejiang Province, Wenzhou University, Wenzhou 325035, China