1. Bradley Department of Electrical and Computer Engineering Virginia Polytechnic Institute and State University Blacksburg Virginia USA
2. State Key Laboratory of Advanced Electromagnetic Engineering and Technology Hubei Electric Power Security and High Efficiency Key Laboratory and School of Electrical and Electronic Engineering Huazhong University of Science and Technology Wuhan China
3. Pacific Northwest National Laboratory Battelle Seattle Research Center Seattle Washington USA
4. Office of Electricity Delivery and Energy Reliability U.S. Department of Energy Washington District of Columbia USA