Frequency Stability Assessment on Virtual Inertia Control Strategy in Connected and Islanded Multi-Area Power Systems

Virtual inertia control has recently come into focus for various applications, reaching from inertia emulation for renewable power plants to frequency stabilization in microgrids. Supply of virtual inertia is achieved by an inverter based virtual synchronous machine (VISMA), or virtual synchronous generator (VSG), emulating a synchronous generator’s behavior. Until today, virtual inertia control for power grid frequency stability has mainly been tested on either islanded microgrids, or grid-connected power systems. This research compares both situations. A model of a three-area power system is presented. Based on this model, it is shown, that the dynamic behavior of a multi-area power system comprised of island-optimized areas can lead to stability issues. Nevertheless, benefits of connecting islanded grid areas are not only increased redundancy, but also decreased amplitudes of frequency transients and reduced stress on mechanical components, as is shown by simulations. Therefore, in a situation where areas are islanded, the possibility of a connection to neighboring areas is important. It is proposed that connection stability issues may be resolved by virtual inertia control integrating damping properties. When combining virtual inertia and virtual damping, the unoptimized three-area system possesses a dynamic behavior superior to that of the optimized islanded system of equivalent configuration.