1. Department of EngineeringGlasgow Caledonian UniversityGlasgowUK
2. Institute of Energy and EnvironmentDepartment of Electrical Engineering Royal College BuildingUniversity of StrathclydeGlasgowUK
3. State Key Laboratory of Alternate Electrical Power System with Renewable Energy SourcesNorth China Electricity Power UniversityBaoding 071000People's Republic of China