1. School of Electrical Engineering, Shandong University, Jinan, China
2. School of Engineering and Applied Sciences and Harvard China Project, Harvard University, Cambridge, MA, USA
3. National power dispatching and control center State grid corporation of China, Beijing, China
4. Department of Electrical Engineering, North China Electric Power University, Baoding, China
5. School of Electrical Engineering, Xi'an Jiaotong University, Xi'an, China