Sequence Impedance Model and Stability Analysis of MMC Considering Wind Farm Integration

When the wind power delivery system based on modular multilevel converter (MMC) is connected to the wind farm, interconnected system is prone to produce harmonic resonance. Impedance analysis method is an effective way to analyze the harmonic resonance. This paper develops the ac side impedance of wind farm and wind farm MMC by multiharmonic linearization. The ac side impedance of wind farm MMC considers all control loops and the dc side impedance of grid side MMC. Compared to the existing models, this model can improve the accuracy of the ac side impedance of wind farm MMC and make it easier to analyze the harmonic resonance of the interconnected system. The model can be used for the stability design of MMC-HVDC system connected to wind farm, and the time-domain simulations in Matlab/Simulink validate the impedance model and stability analysis.