Microgrids Provision of Frequency Response to Low-Inertia Grids

This paper analyzes the ability of microgrids to provide ancillary services, and in particular frequency response, to low inertia grids. Frequency response in power grids is highly dependent on the total available inertia. As the penetration of renewable energy resources is increased, the inertia of the grid reduces making the task of frequency control more difficult. Microgrids equipped with inverter-based resources (IBRs) can provide frequency response to assist low-inertia grids in stabilizing the frequency and hence, facilitating the penetration of more renewables. We compare two types of inverters in terms of their ability to support the frequency: 1) grid-following (GFL) inverters, and 2) grid-forming (GFM) inverters. The support of frequency is measured under multiple microgrid sizes and multiple levels of grid inertia. Three frequency deviation metrics are used in the comparison which are: 1) maximum frequency over/undershoot, 2) maximum rate of change of frequency, and 3) frequency settling time. The analysis is conducted through time-domain simulation in MATLAB/Simulink.