Research on Single Pole Grounding Fault Characteristics of VSC-HVDC Connected Offshore Wind Power Plants

Pseudo-bipolar connection mode is frequently adopted by the voltage-source converter high-voltage direct current (VSC-HVDC) connected offshore wind farms. When a Single Pole grounding fault occurs, the transient fault current is small and there is basically no steady-state fault current, making it difficult to detect the fault location. Meanwhile, the steady-state fault voltage of the non-faulty pole will increase to twice the rated voltage, while its transient voltage can reach more than three times the rated voltage when severe faults occur, which can easily cause insulation damage and withstand voltage damage to the equipment. Therefore, a theoretical method for solving the single pole grounding fault current in VSC-HVDC is proposed in this paper, and the characteristics of transient fault current are summarized and analyzed. The correctness of the theoretical method is verified by digital simulation results.