1. Saint Petersburg State University, St. Petersburg 199034, Russia
2. Institute for Electrophysics and Electric Power, Russian Academy of Sciences, St. Petersburg 191186, Russia
3. Department of Physics, Harbin Institute of Technology, Harbin 150001, China
4. College of Electrical and Information Engineering, Anhui University of Technology, Maanshan 243032, China
5. Electric Automation Research Institute, Anhui University of Science and Technology, Huainan 232001, China