1. Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China 2. School of Electrical Engineering, Shanghai University of Electric Power, Shanghai 200090, China 3. Pudong Power Supply Company, State Grid Shanghai Municipal Electric Power Company, Shanghai 200122, China 4. School of Electronic, Electrical and Systems Engineering, University of Birmingham, Birmingham B152TT, UK 5. Zibo Power Supply Company, State Grid Shandong Electric Power Grid Company, Zibo 255000, China 6. East Electric Power Dispatch and Control Sub-Center, State Grid Corporation of China, Shanghai 200000, China

This work is supported by National Natural Youth Science Fund Project (No. 51407113); Shanghai Engineering Research Center of Green Energy Grid-Connected Technology (13DZ2251900) ‘‘Electrical Engineering’’ Shanghai class II Plateau Discipline; and local capacity building plan of Shanghai science and Technology Commission (16020500900). The authors would also like to thank Prof. Wei-Jen LEE and Prof. Fangxing LI for their contributions.