LIU Jian-lin1, 2, FENG Yao-jing1, GAO Lei3, YANG Kai3
(1. College of Electrical & Information Engineering, Hunan Univ,Changsha,Hunan 410082, China; 2. Hunan Mechanical & Electrical Polytechnic, Changsha,Hunan 410151, China;3. College of Electrical & Electronic Engineering, Huazhong Univ of Science & Technology, Wuhan,Hubei 430074, China)