1. Electrical Engineering Department, Shanghai Maritime University, Shanghai, China
2. photovoltaic division of Zhejiang Hengfu Electric Company Ltd., Hangzhou, China
3. School of Electrical and Computer Engineering, Technical University of Crete, Chania, Greece
4. Department of Electrical Engineering and the Centre for Smart Energy Conversion and Utilization Research, City University of Hong Kong, Kowloon, Hong Kong
5. Christian-Albrechts University of Kiel, Kiel, Germany
6. Energy Engineering Department, Aalborg University, Aalborg, Denmark