[1] Tsinghua Univ, Tsinghua Berkeley Shenzhen Inst, Tsinghua Shenzhen Int Grad Sch, Shenzhen 518071, Peoples R China
[2] Taiyuan Univ Technol, Coll Elect & Power Engn, Taiyuan 030024, Peoples R China
[3] Tsinghua Univ, Dept Elect Engn, State Key Lab Power Syst, Beijing 100084, Peoples R China