1. School of Energy, Power and Mechanical Engineering, North China Electric Power University Baoding Hebei 071003 China
2. Hebei Key Laboratory of Electric Machinery Health Maintenance & Failure Prevention, North China Electric Power University Baoding Hebei 071003 China
3. Advanced Flywheel Energy Storage Technology Research Center of North China Electric Power University, Changping Distinct Beijing 102206 China
4. School of Electrical and Electronic Engineering, North China Electric Power University Baoding Hebei 071003 China