Virtual Synchronous Machine integration on a Commercial Flywheel for Frequency Grid Support

With increasing penetration of inverter-connected power sources, such as RESs, the equivalent inertia in the grid decreases. Employing Maximum Power Point Tracking (MPPT) controllers, RESs behave like constant power sources, not offering damping to support the frequency during disturbances. Novel control algorithms have been proposed that can mimic the inertial behavior of generators or can provide grid support to counter the decline in system inertia. In this letter we explore the capability of a commercially available high speed flywheel energy storage system (FESS) to provide virtual inertia and damping services to microgrids. We demonstrate how a virtual synchronous machine (VSM) algorithm can increase the grid inertia by controlling the FESS active power. A power hardware in the loop (PHIL) evaluation was performed considering the real limitations of a commercial flywheel with different virtual inertia and damping droop settings.