Transient virtual inertia optimization strategy for virtual synchronous generator based on equilibrium point state assessment

Virtual inertia enables the virtual synchronous generator (VSG) to have a good frequency support capability, but improper virtual inertia will deteriorate the transient synchronization characteristics of the VSG during grid faults, and may even lead to transient instability of the VSG. Aiming at this problem, this paper first analyzes the influence of virtual inertia on the transient stability of the VSG under different equilibrium point states. The research shows that reducing the virtual inertia can improve the transient stability when the VSG has equilibrium points, and increasing the virtual inertia can reduce the risk of transient instability when the VSG has no equilibrium points. Based on the above analysis, it is considered to adjust the virtual inertia adaptively according to the equilibrium point state to enhance the transient synchronous operation ability of the VSG. But directly determining the equilibrium point state depends on the measurement of grid parameters, which is difficult to achieve quickly and accurately in engineering. To this end, a transient virtual inertial optimization strategy based on equilibrium point state assessment is proposed. This strategy indirectly assesses the equilibrium point state according to characteristic parameters, flexibly adjusts the virtual inertia, and enhances the transient stability. Finally, simulation and experiment results verify the correctness of the theoretical analysis and the effectiveness of the proposed optimization strategy.