1. Electric Power Research Institute of State Grid Xinjiang Electric Power Co. Ltd., Hengda Street 200, New and high-tech Industrial Development Zone (New Urban), Urumqi 830011, P. R. China
2. State Grid Electric Power Research Institute, Luoyu Road 143, Wuhan 430074, Hubei, P. R. China
3. School of Electrical and Electronic Engineering, Huazhong University of Science and Technology, Luoyu Road 1037, Wuhan 430074, P. R. China
4. Hubei Key Laboratory of Ferro & Piezoelectric Materials and Devices and Faculty of Physics & Electronic Science, Hubei University, Wuhan 430062, P. R. China