1. Electric Power Research Institute, CSG EHV Power Transmission Company 1 , Guangzhou 510663, China
2. Joint Laboratory of DC Transmission Equipment and Submarine Cable Safety Operation 2 , Guangzhou 510663, China
3. Condensed Matter Science and Technology Institute, School of Instrumentation Science and Engineering, Harbin Institute of Technology 3 , Harbin 150080, China
4. Heilongjiang Provincial Key Laboratory of Quantum Control, School of Measurement and Communication Engineering, Harbin University of Science and Technology 4 , Harbin 150080, China