1. State Key Laboratory of Traction Power, Southwest Jiaotong University, Chengdu 610031, P. R. China
2. CRRC Zhuzhou Locomotive Co., Ltd., Zhuzhou 412001, P. R. China
3. Hunan Maglev Technology Research Center Co., Ltd., Changsha 410021, P. R. China
4. State Key Laboratory of Heavy Duty AC Drive, Electric Locomotive Systems Integration, Hunan Zhuzhou 412001, P. R. China