1. School of Electrical Engineering, Xi'an Jiaotong University, 12480 Xi'an, Shaanxi, China, 710049 (e-mail: htzhangee@gmail.com)
2. electrical end computer engineering, Georgia Institute of Technology College of Engineering, 115724 Atlanta, Georgia, United States, 30332-0360 (e-mail: mehraban.mahmoud@gatech.edu)
3. Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States, 30332 (e-mail: maryam@ece.gatech.edu)
4. ELectrical power enginerring, Electrical Engineering College, Xi'an, Shaanxi, China, 710049 (e-mail: mengyq@mail.xjtu.edu.cn)
5. School of Electrical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, China, 710049 (e-mail: xiuliw@mail.xjtu.edu.cn)
6. ELectrical power enginerring, Electrical Engineering College, Xi' an, Shaanxi, China, 710049 (e-mail: xfwang@mail.xjtu.edu.cn)