1. School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China
2. Shaanxi Key Laboratory of Smart Grid and the State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an 710049, China
3. Department of Civil and Environmental Engineering, University of Houston, 4800 Calhoun, Houston, Texas 77004, USA
4. Shaanxi Fast Auto Drive Engineering Research Institute, Xi’an 710119, China