1. Departmentof Electrical Engineering, Shanghai Maritime University, Shanghai, China
2. National Ocean Technology Center of China, Tianjin, China
3. East China Sea Standard Measurement Center of the State Oceanic Administration of China, Tianjin, China
4. School of Electrical and Computer Engineering, Technical University of Crete, Chania, Greece
5. Department of Energy Engineering, Aalborg University, Aalborg, Denmark