1. Department of Polymer Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People's Republic of China
2. State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400030, People's Republic of China
3. Global Energy Interconnection Research Institute, Beijing 102211, People's Republic of China
4. State Key Laboratory of Power System, Department of Electrical Engineering, Tsinghua University, Beijing 100084, People's Republic of China