Impact of Inertia Emulation and Droop Control on Frequency Dynamics of Inverter-Based Microgrids

The increasing integration of inverter-based resources (IBRs) is transforming conventional power systems and challenging the grid stability due to reduced synchronous inertia and weakened network strength. This paper investigates the frequency response and power-sharing in an inverter-based micro grid through the coordinated control of grid-forming (GFM) and grid-following (GFL) inverters operating in parallel. Electromagnetic transient (EMT) simulations are conducted on a 12 MV A medium voltage micro grid with two photovoltaic (PV) systems, each having 3 MV A of headroom for regulation, to evaluate the effects of droop coefficients, inertia emulation, and damping on the frequency response and active/reactive power sharing. The study compares different control strategies, including droop and virtual synchronous machine (VSM) based approaches. Results show that the combined inertia emulation from both the GFM and GFL units, with tuned droop and inertia parameters, leads to faster damping of power oscillations and improves the steady-state frequency. In the best-performing case, the rate of change of frequency (RoCoF) is reduced to −3.51 Hz/s, and the frequency nadir is improved to 49.92 Hz.