1. Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education, the School of electrical engineering, Guangxi University, Nanning, China
2. Department of Electrical and Electronic Engineering, University of Hong Kong, Hong Kong
3. State Key Laboratory of Alternate Electrical Supply System with Renewable Energy Sources, North China Electric Power University, Beijing, China
4. Key Laboratory of Special Machine and High Voltage Apparatus, Ministry of Education, Shenyang University of Technology, Shenyang, China