1. Department of Electrical Engineering, Tsinghua University, Beijing, China
2. Chongqing Key Laboratory of Computational Intelligence, Chongqing University of Posts and Telecommunications, Chongqing, China
3. School of Electrical Engineering, Chongqing University, Chongqing, China
4. Power Grid Technology Center, Chongqing Electric Power Company of SGCC, Chongqing, China