1. High-voltage Key Laboratory of Fujian Province, Xiamen University of Technology, Xiamen, P.R. China.
2. Research Institute of Intelligent Control and Systems, Harbin Institute of Technology, Harbin, P.R. China.
3. School of Electrical Engineering and Automation, Fuzhou University, Fuzhou, P.R. China.
4. School of Electrical Engineering, Xi’an Jiaotong University, Xi’an, P.R. China.