An Overview on Resonance Instability of Multiple Grid-connected Inverters in Weak Grid

The resonance problem caused by the grid-connected inverter's integration would directly affect the grid current quality and the system stability. This paper comprehensively reviews the resonance instability of multiple grid-connected inverters in the weak grid, including stability analysis methods, stability influence factors and resonance analysis methods. First, the topology and control strategy of grid-connected inverters are introduced. Second, the applications of the state-space method and the impedance analysis method in stability analysis of system with grid-connected inverters are compared, and the output impedance modeling of grid-connected inverter system is investigated. Then, the influences of grid impedance, inverter parameters, phase-locked loop and the number of parallel inverters on the stability of grid-connected inverter system are analyzed. Finally, the traditional frequency domain analysis method and the modal analysis method are applied to analyze the resonance instability mechanism of multiple grid-connected inverter system. The advantages and application prospects of the modal analysis method in resonance analysis are explored.