Stability Analysis of SVI Multi-parallel System Based on Impedance Method

The renewable energy generation system based on Self-synchronous Voltage-source Inverter (SVI) has various stability problems nowadays, so it is necessary to analyze the stability of SVI multi-parallel system. Firstly, the impedance model is established based on the control strategy of SVI, and an SVI multi-unit impedance equivalent model is proposed and verified by the sweep-frequency simulation. Then, according to the impedance stability criterion, a bode diagram is used to analyze the stability of the system under the series-complemented grid. In the case of the series-complemented grid, the phase angle margin decreases when the series-complemented degree is higher, the stability decreases, and oscillation is likely to occur in the sub-synchronous frequency band of 20 Hz–30 Hz. Finally, the correctness and accuracy of the stability analysis are verified by the simulation of the 3-unit parallel system in MATLAB.