Coordinated Control Strategy of DC Fault Ride-through for the WF Connected to the Grid Through the MMC-HVDC

Aiming at the problems of DC fault isolation and power surplus in the HVDC system with large-scale wind farm (WF) integration after single-pole grounding fault, this paper designs a modified current transfer modular multilevel converter (M-CT-MMC) topology with DC fault isolation and power dissipation functions, and DC fault ride-through can be realized by the coordination of the M-CT-MMC and wind turbines. The DC fault current can be isolated through the coordination of each branch of M-CT-MMC. In terms of surplus power consumption, the control mode switching strategy of M-CT-MMC is designed to improve the power transmission capability of the non-fault pole and make it absorb surplus power independently. Furthermore, a coordinated control strategy of wind turbines and dissipation resistors is designed to absorb surplus power. With the advantages of fast response speed of wind turbine and reliable dissipation resistance, DC fault ride-through under different working conditions is realized. Finally, the effectiveness and feasibility of the coordinated control strategy for DC fault ride-through are verified.