1. School of Electrical Engineering, Shandong University, Jinan, China
2. College of Electrical Engineering and Automation, Fuzhou University, Fuzhou, China
3. School of Electrical Engineering, University of Jinan, Jinan, China
4. Electrical Engineering Department, Technical University of Denmark, Copenhagen, Denmark
5. Facultad de Ingenieria, Universidad Andres Bello, Santiago, Chile