Coordinated control strategies for DC fault ride-through of wind power integration via bipolar hybrid MMC-HVDC overhead lines

The overhead line MMC-HVDC is an effective method for large-scale wind-power-friendly grid connection and reliable delivery. Faced with the high failure rate of overhead lines, a scheme of adopting symmetrical bipolar wiring and hybrid MMC with fault blocking capability is one of the main methods of tackling this. Based on this scheme, this paper proposes a DC fault ride-through coordinated control strategy for grid-connected wind power via a bipolar hybrid MMC-HVDC. Through hybrid MMC zero DC voltage control, the fault current is effectively blocked and the support ability of the fault pole MMC to the AC voltage is maintained. Based on the flexible operation mode of the symmetrical bipolar wiring scheme, and according to whether the fault pole power can be completely absorbed by non-fault poles, the control strategies of non-fault pole under self-absorption and non-self-absorption conditions and parameter adjustment principles are designed. Based on the frequency response capability of the wind farm, a control strategy without communication is designed to achieve accurate load reduction of wind power, and then achieve full load operation of a non-faulty MMC. This scheme could reduce the impact on the receiving AC system while maintaining the safe and stable operation of the system. Finally, a grid-connected system model is built on Matlab/Simulink to verify the effectiveness of the proposed DC fault ride-through coordinated control strategy. © 2021 Power System Protection and Control Press.