Impedance Modeling and Impedance Characteristics Analysis of SVI Multi-unit Parallel System

Various stability problems have arisen in the current renewable energy generation systems based on Self-synchronous Voltage-source Inverters (SVI). Therefore, there is an urgent requirement to analyze the impedance characteristics of SVI multi-unit parallel systems. Firstly, the impedance model of a single unit is derived based on the control strategy of SVI using the harmonic linearization method. Then, an SVI multi-unit parallel equivalent impedance modeling method is proposed based on the condition that the parameters are consistent. The multi-unit system is equated to the parallel connection of SVIs with the same parameters, so as to derive the SVI multi-unit parallel equivalent impedance model. Meanwhile, the impedance is verified by MATLAB sweep-frequency simulation. Finally, according to the established impedance model, the effects of LC filter parameters, parallel line impedance, and the number of parallel units on the equivalent impedance characteristics are analyzed, which provides a reference for the stability analysis and optimization of renewable energy generation systems.