Modeling and Stability Analysis of Multi-parallel Grid-Connected PCSs

Aiming at the resonant issue of multi-parallel grid-connected power conversion systems (PCSs), a method to suppress resonance spikes of the system is proposed, and the stability of the parallel system is studied. Firstly, the resonance characteristic of a single LCL-type PCS is analyzed, accordingly, the passive damping strategy with filter capacitor series resistor is introduced, and the stability of a single PCS based on the current control loop is studied. Then, the mathematical model of multi-parallel grid-connected PCSs system under the influence of grid impedance is established, and the amplitude-frequency characteristic curves are used to verify that the passive damping method can effectively restrain the resonant spikes generated by the coupling of multiple PCSs and enhance the stability of the system. Finally, by utilizing simulation, it is verified that the passive damping method has the characteristics of high reliability and strong ability to suppress resonance spikes.