Stability and Passivity Analysis of Single-Voltage-Loop Grid-Forming VSIs with Negative Proportional Gain

Serving as the core of grid-forming (GFM) voltage-source inverters (VSIs), voltage regulation plays a crucial role in defining the control stability and shaping the dynamic response. In this context, this article examines the stability and passivity of a single-voltage-loop GFM VSI with negative proportional gain. It has been revealed that a negative proportional gain introduces additional phase delays, thereby enlarging the stability margin. In the meantime, a negative proportional gain extends the passive region, while the commonly used positive proportional gain shows the opposite effect. Subsequently, simulation and experimental studies under different operating conditions validate the theoretical findings.