1. School of Electrical Engineering &Automation, Harbin Institute of Technology, Harbin 150001, China
2. School of Electric Power, Shenyang Institute of Engineering, Shenyang 110136, China
3. Liaoning Provincial Institute of Safety Science, 110004 Shenyang, China
4. Fushun Power Supply Company, State Grid Liaoning Electric Power Supply Co Ltd, Fushun 113008, China