Frequency regulation optimization strategy of improved virtual synchronous generator under ultra-weak grid conditions

To enhance the frequency support capability of grid-forming energy storage systems governed by Virtual Synchronous Generators (VSGs) under ultra-weak grid conditions, an improved VSG frequency support strategy is proposed based on model predictive control. Initially, to account for the frequency regulation characteristics of the VSG and the distinct fluctuation patterns under ultra-weak grid conditions, the concepts of interval adjustment coefficients and damping factors are introduced. Corresponding incremental adjustment coefficients and damping factors are designed for distinct VSG frequency regulation intervals, allowing improved handling of frequency variations in ultra-weak grids and enhancing the system’s dynamic response. Subsequently, a model predictive control scheme that incorporates frequency deviation and the rate of change of frequency as weighted coefficients is introduced to further enhance the system’s active regulation capability. Finally, simulations are conducted under various operating scenarios in an ultra-weak grid environment with a short-circuit ratio of 2. The simulation results indicate that the proposed strategy significantly improves the VSG’s frequency regulation capability under ultra-weak grid conditions, notably reduces frequency deviations, and effectively mitigates frequency oscillations.