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摘要
The frequency coupling phenomenon of the virtual synchronous generator (VSG) will reduce the stability margin of the system and cause the oscillation instability of the VSG. The article establishes a VSG sequence impedance model, and analyzes the influence mechanism of frequency coupling characteristics on the stability of VSG. Considering that the sequence impedance of the VSG and the grid impedance are coupled with each other after the frequency coupling characteristics are added, a simplified design scheme of virtual impedance is proposed; the grid-source subsystem is re-segmented, the virtual impedance is converted to the grid side, and the grid-connected stability is used at the same time. And the power output capability gives the virtual impedance value range for the constraint. The experimental results on the StarSim semi-physical platform verify the feasibility and correctness of the simplified virtual impedance scheme and parameter design method, and show that the method can enhance the stability margin of the VSG under different grid impedances and ensure that the system has sufficient power output capability. ? 2022 Science Press.
