A Comprehensive Robustness Analysis of Grid-Forming Virtual Synchronous Machine Systems for the Evaluation of Frequency Performance

This research proposes a robustness analysis model for the frequency performance of grid-forming converter systems (GFMCS). Based on the derived sensitivity and complementary sensitivity functions, a system robustness identification framework is established. This framework includes two key frequency performance indices: sensitivity and robust stability. Sensitivity analysis is used to describe the system’s sensitivity to external disturbances. In addition, the judgment criterion is proposed to quantitatively and intuitively identify the robustness of the GFMCS. Furthermore, the influence mechanisms of the damping and inertia coefficients on robustness are examined comprehensively. This study finds that when the damping coefficient is small, and the inertia coefficient is large, the system is more prone to oscillatory instability, resulting in longer stability time as well as poorer robustness. Finally, the theoretical analysis is validated experimentally.