Modeling and Analysis of Grid-Supporting Virtual Synchronous Generator Systems Considering Impact of Grid Strength Disturbances

Abstract

Grid-supporting virtual synchronous generator (GS-VSG) may suffer from power oscillation under strong-grid conditions and relatively high ratio of R/X ratio. However, the conventional small-signal analysis does not incorporate the dynamic characteristics of grid-impedance variations. To tackle this issue, this work proposes a power response model in which grid impedance is treated as a small-signal disturbance variable. Based on the proposed model, the stability and dynamic performance of the GS-VSG system are systematically analyzed. The dominant eigenvalues of the proposed active-power-grid-impedance response model agree well with those of the closed-loop system model and achieve a relative error within approximately 4% in comparison to electromagnetic (EMT) model. In addition, auxiliary control strategies referring to a compound feedback path are introduced for robustness analysis by comparing theoretical model with EMT model. Finally, the effectiveness of proposed active power-grid impedance response model is demonstrated by hardware-in-the-loop experiments.