Research on control strategy of fault ride-through of MMC-HVDC connected to wind farm

During the fault ride-through process of the MMC-HVDC system for the grid-connected offshore wind farm, the unloading circuit does not start to function until the DC voltage reaches a certain value for a period of time, which results in a great impact on the sub-module voltage on the land side, there is a risk of damaging the electronic components, in this paper, the control strategy is improved according to the system characteristics during the fault, and the sub-module voltage is suppressed under the premise of ensuring the system fault ride-through performance. Finally, a semi-physical simulation model of the pseudo-bipolar flexible HVDC transmission system at both ends was built based on the RTDS simulation system, and the improved control strategy was verified in the control and protection device.