1. State Key Laboratory of Power Systems, Department of Electrical EngineeringTsinghua UniversityBeijingPeople's Republic of China
2. Department of Electrical and Computer EngineeringStevens Institute of TechnologyHobokenNJUSA
3. Department of Electrical Engineering and Computer ScienceUniversity of TennesseeKnoxvilleTNUSA
4. Department of Electrical EngineeringXi'an Jiaotong UniversityXi'anPeople's Republic of China