Characteristic Investigation and Overvoltage Suppression of MMC-HVDC Integrated Offshore Wind Farms Under Onshore Valve-Side SPG Fault

The valve-side ground fault in the converter station of modular multilevel converter based high voltage direct current (MMC-HVDC) is a serious threat to the security of power systems. Hence, this paper analyzes the most common single-phase-to-ground (SPG) fault characteristics of valve-side faults in onshore converter stations of MMC-HVDC integrated offshore wind farms. The propagation and impact mechanism of onshore SPG fault to offshore HVDC transmission lines, offshore converter station, and wind farms are deduced based on the MMC control principle. Furthermore, an overvoltage suppression strategy based on zero-sequence voltage modulation is proposed. The effect mechanism of this strategy on the transient stability of the system is analyzed. The key parameter of the proposed strategy is also designed considering both the practical engineering requirements and the impact of the system operation. Finally, the theoretical analysis of fault characteristics and the proposed overvoltage suppression strategy are verified by the PSCAD/EMTDC simulation platform. Simulation results not only show good agreement with the theoretical analysis of the fault characteristics, but also prove the effectiveness of the proposed overvoltage suppression strategy.