[1] Kunming Univ Sci & Technol, Fac Elect Power Engn, Kunming 650500, Yunnan, Peoples R China
[2] Yunnan Power Grid Co Ltd, Elect Power Res Inst, Kunming 650217, Yunnan, Peoples R China
[3] Hong Kong Polytech Univ, Dept Elect Engn, Kowloon, Hong Kong 999077, Peoples R China
[4] South China Univ Technol, Coll Elect Power, Guangzhou 510640, Peoples R China