1. School of Electrical Engineering and Information, Tianjin Univ., Tianjin 300072, China.
2. Professor, School of Electrical Engineering and Information, Tianjin Univ., Tianjin 300072, China.
3. Associate Professor, School of Electrical Engineering and Information, Tianjin Univ., Tianjin 300072, China (corresponding author).
4. Lecturer, School of Electrical Engineering, Hebei Univ. of Science and Technology, Shijiazhuang 050000, China.
5. Instructor, Beijing Institute of Control Engineering, Beijing 100074, China. Email: lwjingbice@163.com