Small-Signal Impedance Modeling of Modular Multilevel Matrix Converter for Stability Analysis of Low-Frequency Transmission System

Low-frequency transmission system (LFTS) has become a highly competitive technical solution for the long-distance transmission of renewable energy. Its power-electronic nature makes LFTS at risk of experiencing wideband oscillations. Impedance analysis method is a simple and efficient method for stability analysis of power system. Proposing the impedance model of modular multilevel matrix converter(M³C), which is the key device of LFTS, is the basis of applying the impedance method to stability analysis of LFTS. The paper analyzes the structure of M³C and the small-signal propagation process within it. The equation set of small-signal model is derived and the impedance model of M³C based on harmonic state-space (HSS) method is proposed. Furthermore, a cross-hybrid impedance model for stability analysis of LFTS for renewable energy transmission is proposed. The model can efficiently characterize the frequency-domain admittance characteristic of M³C. Finally, the simulation verification based on Matlab/Simulink has been carried out, which verified the accuracy of the impedance model proposed.