1. North China Electric Power University,State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources,Beijing,P.R.China,102206
2. State Grid Tibet Electric Power Co., Ltd. Naqu Power Supply Company,Naqu,China,852000
3. Tibet Yangbajing High Altitude Electrical Safety and Electromagnetic Environment National Observation and Research Station,Lhasa,China,851500
4. University of Cambridge,Electrical Engineering Division,Cambridge,UK,CB3 0FA