Virtual Inertia Emulation and Frequency Control of a Wind–Solar PV-Geothermal-Based Low-Inertia Microgrid

Abstract

AbstractRenewable sources such as wind turbine generator system (WTGS) and solar photovoltaic system (SPVS) do not have rotating parts, and as a result, when these renewable sources are incorporated into a microgrid (µG), the overall inertia of the µG decreases. In the situation of uncertainties, this low system inertia creates a high rate of change of frequency (ROCOF) and a high dip in frequency from the nominal value, thus disturbing the µG stability. This paper addresses a frequency control scheme for a wind–solar photovoltaic–geothermal-based µG by emulation of virtual inertia (VI) control loop into the µG. In this work, derivative-type VI control has been employed using an energy storage system (ESS). The usefulness of the proposed derivative-type VI and frequency controller has been tested through the dynamic response of the µG system for a small load perturbation. Robustness of the proposed VI control scheme has been checked against varying load, varying wind speed and varying solar irradiation level.KeywordsEnergy storage systemMicrogridRate of change of frequencyRenewable energyVirtual inertia