MMC-HVDC Fault Ride-through Coordination Control Strategy at Both Ends

When the MMC-HVDC system supplying power to passive network has AC fault, the dc voltage will drop seriously or even collapse. This paper introduces the topological structure and decoupling control of MMC, and then analyzes the mechanism of capacitor discharge of MMC in the case of AC fault at the sending end and the correlation between dc voltage sag and the control mode. The core idea of the strategy is that, when the fault occurs, the d-axis current obtained by the original sending end control mode under the fault condition is taken as the actual measurement, and the d-axis current obtained by the original sending end control mode under the steady-state condition is taken as the reference value of the d-axis current under the fault condition. Finally, the study is carried on PSCAD platform, and the effectiveness of the strategy is verified.