1. North China Electric Power University,State Key Laboratory for Alternate Electrical Power System with Renewable Energy Sources,Beijing,China
2. Institute of Electrical Engineering, Chinese Academy of Sciences,Beijing,China,100190
3. North China Electric Power University,State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources,Beijing,China,102206
4. North China Electric Power University,Beijing Key Laboratory of High Voltage and Electromagnetic Compatibility,Beijing,China