1. Department of Electrical EngineeringNortheast Dianli UniversityJilin132012People's Republic of China
2. Electrical Engineering and Computer Science DepartmentUniversity of TennesseeKnoxvilleTN37996USA
3. Key Laboratory of Smart Grid of Ministry of EducationTianjin UniversityTianjin300072People's Republic of China
4. Department of Electrical and Computer EngineeringBinghamton UniversityBinghamtonNY13902USA