1. Faculty of Electric Power Engineering, Kunming University of Science and Technology, Kunming, China
2. Electrical and Computer Engineering Department, Illinois Institute of Technology, Chicago, IL, USA
3. College of Energy and Electrical Engineering, Hohai University, Nanjing, China
4. Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai, China
5. Electric Power Research Institute, Yunnan Power Grid Company Ltd., Kunming, China