1. State Grid Hubei Electric Power Research Institute, Wuhan 430062, China
2. State Grid Wuhan Power Supply Company, Wuhan 430070, China
3. Department of Electrical Engineering, Wuhan Electric Power Technical College, Wuhan 430074, China
4. State Key Laboratory of Power Grid Environment Protection, School of Electrical Engineering and Automation, Wuhan University, Wuhan 430072, China