[1] Beijing Inst Technol, Collaborat Innovat Ctr Elect Vehicles Beijing, Beijing 100081, Peoples R China
[2] Beijing Inst Technol, Natl Engn Lab Elect Vehicles, Beijing 100081, Peoples R China
[3] Beijing Inst Technol, Chongqing Innovat Ctr, Chongqing 401120, Peoples R China
[4] Univ Witwatersrand, Sch Elect & Informat Engn, ZA-2050 Johannesburg, South Africa