[1] Nanjing Univ Technol, Sch Automat & Elect Engn, Nanjing 210009, Jiangsu, Peoples R China
[2] Xi An Jiao Tong Univ, State Key Lab Elect Insulat & Power Equipment, Xian 710049, Peoples R China
[3] Chinese Acad Sci, Inst Elect Engn, Beijing 100190, Peoples R China
[4] Chinese Acad Sci, Key Lab Power Elect & Elect Dr, Beijing 100190, Peoples R China