Impedance Modeling and Small Signal Stability Analysis of the Cascaded AC/DC Converter

The cascaded AC/DC converters are drawing increasing attention due to their advantages in medium-voltage applications. However, the modelling of the cascaded AC/DC converter lacks an in-depth study for stability analysis and parameter optimization. To address this issue, the harmonic-domain matrix modelling method is introduced in this paper to establish grid-side impedance model of a two-module cascaded AC/DC converter. The relevant stability analysis is also conducted with the Nyquist criterion. The impact of the additional balancing control is discussed. The effectiveness of the derived impedance model and its relevant analysis are verified by the simulation on the Matlab/Simulink.