1. Hebei Provincial Key Laboratory of Power Transmission, Equipment Security Defence, North China Electric Power University, Baoding 071003, Hebei, P. R. China
2. State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, P. R. China
3. Ganzhou Longbang Material Technology Co., Ltd., Ganzhou 341000, Jiangxi, P. R. China