1. Department of Electrical EngineeringNortheast Electric Power UniversityJilin132012People's Republic of China
2. Department of Electrical Engineering and Computer ScienceUniversity of TennesseeKnoxvilleTN37996USA
3. Peak ReliabilityLovelandCO80538USA
4. Key Laboratory of Smart Grid of Ministry of EducationTianjin UniversityTianjin300072People's Republic of China