Abstract: [Objectives] To address issues such as power angle instability and insufficient voltage support caused by symmetrical short-circuit faults in virtual synchronous generators (VSG) within low-inertia power grids, a VSG control strategy combining power angle compensation and adaptive voltage droop coefficient is proposed. [Methods] The variation in transient power angle is fed back into the active power control loop, and it is decomposed in combination with the unbalanced power expression, thereby deriving and introducing a variable gain. On this basis, an adaptive reactive power voltage droop coefficient is further introduced and dynamically adjusted according to the depth of voltage sag, thereby achieving stable voltage support for the point of common coupling during faults. Finally, the effectiveness of the proposed strategy is verified by MATLAB/Simulink simulation experiments. [Results] The proposed control strategy can adaptively adjust control parameters according to the degree of voltage sag, reducing the amplitude of power angle oscillations of the inverters during faults, significantly decreasing voltage fluctuations at the point of common coupling, and shortening the recovery time. [Conclusions] The proposed control strategy not only effectively improves transient power angle stability during faults, but also significantly enhances voltage and reactive power support capabilities, thereby ensuring the safe and stable operation of inverters under grid fault conditions.

Key words: power grid, renewable energy, distributed generation, grid-connected inverter, virtual synchronous generator (VSG), voltage support, transient power angle