1. School of Electrical Engineering at Chongqing University,Chongqing,China,400044
2. Chongqing University,State Key Laboratory of Power Equipment Technology,Chongqing,China,400044
3. Chongqing Electric Power Research Institute State Grid Cooperation of China,Chongqing,China,401123
4. Fengdu Power Supply Branch of State Grid Chongqing Electric Power Company,Chongqing,China,408200