1. Department of Electrical Engineering, Hebei University of Technology, Tianjin, China
2. State Key Laboratory of Reliability and Intelligence of Electrical Equipment, Hebei University of Technology, Tianjin, China
3. School of Electrical Engineering, Hebei University of Technology, Tianjin, China
4. Hebei University of Technology, Tianjin, China
5. Aalborg University, Aalborg Øst, Denmark