Small Signal Stability Analysis of Virtual Impedance Control in Islanded Microgrid

This paper examines the impact of virtual impedance control in an inverter-dominated microgrid (MG) system. The goal is to provide a clear understanding of Virtual Impedance (VI) control toward MG stability. This analysis is performed by developing the system’s Small-Signal Model (SSM) and studying the poles’ trajectory change when the system’s key control parameters are varied. The results indicate that VI will benefit system stability when considering MG with low X/R while negatively affecting MG with high X/R. Also, there is a trade-off between the coupling impedance of the inverter and the VI parameters, which needs to be considered when incorporating this control with existing grid-forming (GFM) controllers.