1. School of Automation and Electrical Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
2. Baiyin Power Supply Company of State Grid Gansu Power Supply Company, Baiyin 730900, China
3. School of New Energy and Power Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
4. Electric Power Research Institute of State Grid Gansu Electric Power Company, Lanzhou 730070, China