[Cao, Yijia; Yang, Xian; Li, Yong] Hunan Univ, Coll Elect & Informat Engn, Changsha 410082, Hunan, Peoples R China.
[Yang, Xian] Hunan City Univ, Sch Mech & Elect Engn, Yiyang 413002, Peoples R China.
[Cai, Ye] Changsha Univ Sci Technol, Coll Elect & Informat Engn, Changsha 410114, Hunan, Peoples R China.
[Lee, Kwang Y.] Baylor Univ, Dept Elect & Comp Engn, Waco, TX 76798 USA.
[Jia, Zhijian] State Grid Yiyang Power Supply Co, State Grid, Yiyang 413000, Peoples R China.