1. Offshore Wind Power Research Institute, Shanghai University of Electric Power, Shanghai, China
2. School of Electrical Engineering, Xi'an University of Technology, Xi'an, China
3. School of Electrical Engineering, Xi'an Jiaotong University, Xi'an, China
4. Department of Electrical Engineering, State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment, Tsinghua University, Beijing, China
5. College of Information and Electrical Engineering, China Agricultural University, Beijing, China