1 | School of Economics and Management, North China Electric Power University, Baoding 071003, China |
2 | Division of Development, Gansu Electric Power Corporation, State Grid (Research Institute of Economy
and Technology), Lanzhou 730050, China |
3 | School of Electrical Engineering and Information Engineering, Lanzhou University of Technology,
Lanzhou 730050, China |
4 | School of Electrical and Electronic Engineering, North China Electric Power University, Baoding 071003, China |