Stability Analysis and Virtual Inductance Control for Static Synchronous Compensators with Voltage-Droop Support in Weak Grid

Static synchronous compensators (STATCOMs) are widely applied in modern power networks for reactive power compensation and grid voltage regulation. Compared to the conventional compensation devices, the STATCOMs deliver superior performance through the voltage-droop control loop. However, the interaction between the STATCOMs and grid impedance, especially in weak grids, can lead to stability issues. To investigate this instability mechanism, the STATCOMs and grid impedance are modeled as a multi-input–multi-output system in this paper. Thus, the coupling effects between the control loop and the grid impedance are clearly highlighted, making the stability assessment feasible. The proposed method avoids the cost and volume issues associated with adding physical inductance in traditional approaches to mitigate these coupling effects. It not only improves the operational stability of the STATCOM but also enhances its voltage support capability, thereby supplementing the stability research for weak grids with STATCOMs under this specific condition. The effectiveness of the presented analysis and proposed control scheme are validated through both simulation and experimental results.