1. School of Electrical Engineering, Southwest Jiaotong University, Chengdu, China
2. SWJTU-Leeds Joint School and National Rail Transit Electrification and Automation Engineering Technique Research Centre, Southwest Jiaotong University, Chengdu, China
3. Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong, China
4. State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu, China