DC grid is an effective means to realize large-scale renewable energy power generation collection

multi-energy complementation

and friendly grid connection. For the large-scale wind power connected to DC grid in island mode

the coordinated control strategies for fault ride-through under the conditions of DC line over-current

the non-fault pole MMC overload and DC grid over-voltage are proposed respectively based on the analysis of its power surplus characteristics. As for DC line over-current

the overload problem of DC line can be effectively solved by reasonably switching the control mode of fault pole MMC and making the non-fault pole MMC to absorb the surplus power independently. As for the non-fault pole MMC overload

the precise load-shedding control of wind farm and its coordination scheme with dissipative resistors are designed

which can effectively reduce the probability and capacity of dissipative resistors input and wind turbines being disconnected

and can improve the system recovery speed.As for DC grid over-voltage

an additional control strategy for reducing the output power of wind farm based on the local DC voltage and its coordinated cooperation with the dissipative resistors are designed to effectively restrain the change rate and amplitude of DC voltage and improve the ability of safe and stable operation of the system. Finally

based on the RTLAB OP5600 real-time digital simulation platform

a four-terminal DC grid simulation model is built to verify the effectiveness and feasibility of the proposed coordinated control strategies under different power surplus conditions.