Impedance Modeling and Analysis of Grid Side Sampling Modular Multilevel Converter

The impedance-based analysis method is an effective way to study the small-signal stability of the grid-connected converter system. A valid impedance model is the premise of the accurate stability analysis. In this study, the impedance model of the grid side sampling modular multilevel converter (MMC) is established both in AC and DC side. Compared with the existing work, the effect of the transformer impedance, ratio and group on the impedance characteristic is considered in modeling, which improves the accuracy of model. the effect of transformer parameters and types on MMC impedance characteristic is analyzed, after verifying the valid of the model in Matlab/Simulink. The stability analysis results show that the model can provide a theoretical reference for the impedance modeling and analysis of the grid side sampling MMC.