Stability Analysis of Grid Connected System under the Influence of Grid Impedance

New energy power generation widely relies on grid connected inverters to connect with the power grid, and the traditional double closed-loop control strategy has been widely used. Due to the fluctuation of power grid impedance, when it changes, it may cause resonance in the system, and the grid connected waveform is seriously distorted, which poses a threat to the stability of the system. In this paper, based on the equivalent model of grid connected inverter, the concept of harmonic resonance is proposed, and the difference and connection with traditional circuit resonance are analyzed. The simulation verifies that with the gradual increase of grid impedance, the stability of the system gradually decreases, the harmonic resonance gradually appears.