Primary and Secondary Frequency Control of Low-Inertia Microgrids with Battery Energy Storage and Intermittent Renewable Energy Resources

Abstract

This paper aims to present an accurate and meaningful model of primary and secondary frequency control of low-inertia microgrids (MGs), composed of battery energy storage, wind, and solar units. At the same time, the impact of the virtual synchronous generator (VSG) versus the PQ control method on the frequency variation of MG is discussed. Moreover, it is mathematically proven that power sharing occurs based on the reverse proportion of the droop coefficients of the diesel generator and the battery storage in the primary frequency control. However, when the secondary control loop is applied, the battery storage just provides power during transients and produces no power in the steady state. Simulation results show that the frequency response of the MG improves once the VSG control method is used for the inverters as well as confirming the power sharing ratio, having been mathematically proven.