1. School of Vehicle and Mobility, Tsinghua University, Beijing 100084, China
2. College of Locomotive and Rolling Stock Engineering, Dalian Jiaotong University, Dalian 116028, China
3. School of Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520, China
4. Department of Electrical Engineering, Tsinghua University, Beijing 100084, China