Simulation Research on Single-Phase Grounding Fault Characteristics of New Energy Transmission AC Line connected to Flexible HVDC Power Grid

In this paper, the single phase grounding fault characteristics of AC lines connected to the flexible HVDC power grid under the background of new energy transmission are simulated and analyzed. Firstly, the simulation model is reliable, accurate and effective. Then, by changing the output of other new energy sources, replacing the flexible HVDC power grid with the traditional AC power grid, replacing the wind turbine with the traditional synchronous machine, and changing the operation mode of the flexible HVDC power grid, it is clear that the wind turbine is one of the main factors affecting the RMS value of the zero-sequence current (steady state) of the Zhongchang line after the single-phase grounding permanent fault. Compared with the traditional synchronous machine, when the active power output of wind turbine is the same before the fault, the zero sequence current and zero sequence voltage will increase after the fault, which will lead to the false operation of the backup protection. The output of other new energy sources except for the Changfengliang wind farm, the flexible HVDC power grid and its operation mode have no influence on the zero-sequence current and zero-sequence voltage (steady state) RMS. This study is of guiding significance for the relay protection setting construction of AC lines connected to the flexible HVDC power grid under the background of new energy transmission.