1. College of Information and Computer Science, Taiyuan University of Technology, Taiyuan, China
2. School of Electrical Engineering, Shandong University, Jinan, China
3. School of Electric and Electronic Engineering, North China Electric Power University, Beijing, China
4. Shandong Power Company of the State Grid, Jinan, China
5. Department of Computer Science, State University of New York, New Paltz, NY, USA