1. Jinzhou County Power Supply Company, State Grid Hebei Electric Power Co., Ltd., Jinzhou 052200, China
2. Shijiazhuang Power Supply Company, State Grid Hebei Electric Power Co., Ltd., Shijiazhuang 050051, China
3. State Grid Hebei Electric Power Co., Ltd., Shijiazhuang 050051, China
4. Key Laboratory of Power Electronics for Energy Conservation and Motor Drive of Hebei Province, Yanshan University, Qinhuangdao 066004, China