1. School of Electrical and Information Engineering; Anhui University of Technology; Ma'anshan 243002 China
2. Department of Electrical Engineering; Yeungnam University; 280 Daehak-Ro, Kyongsan 712-749 Korea
3. National Laboratory of Industrial Control Technology; Institute of Cyber-Systems and Control, Zhejiang University; Hangzhou Zhejiang, 310027 China