Impedance-Based Stability Analysis of MMC-HVDC for Offshore DFIG-Based Wind Farms

摘要

Impedance-based stability analysis method has been proved to be a simple and useful method to analyze the stability of an interconnected system. Due to the high-quality output voltage and low switching frequencies of MMC, it attracts widely-spread attention in HVDC transmission for wind farms. This paper develops the AC side small-signal impedance model of MMC based on multi-harmonic linearization. Based on the impedance model, the stability of MMC-HVDC for DFIG-based wind farms integration under small disturbance is analyzed and the potential resonant frequencies are predicted by using Nyquist stability criterion. Then the influences of transmission line parameters, controller parameters on system stability are analyzed in detail. The simulation model with a 36-level MMC and DFIG based wind farm is built based on Matlab/Simulink to validate the correctness of the impedance-based stability analysis method.