1. Department of Chemical Engineering, Tsinghua University 1 , Beijing 100084, China
2. Department of Electrical Engineering, Tsinghua University 2 , Beijing 100084, China
3. School of Physics, Beijing Institute of Technology 3 , Beijing 100081, China
4. Department of Electrical and Computer Engineering, Michigan State University 4 , East Lansing, Michigan 48824, USA
5. Department of Computational Mathematics, Science and Engineering, Michigan State University 5 , East Lansing, Michigan 48824, USA
6. StateKey Laboratory of Power System Operation and Control, Department of Electrical Engineering, Tsinghua University 6 , Beijing 100084, China