Grid-Forming Inverter Control for Renewable-Dominated Power Systems

The accelerating displacement of synchronous generation by inverter-based renewable resources is eroding the rotational inertia and frequency-regulating capability that have historically maintained power-system stability. Conventional grid-following inverters behave as controlled current sources and depend on a stiff external grid for synchronization, rendering them inadequate as the dominant resource. Grid-forming (GFM) inverters, which regulate their own voltage magnitude and frequency and can operate without a pre-existing grid reference, are widely regarded as the enabling technology for very high renewable penetration.

This paper reviews and comparatively evaluates the principal grid-forming control strategies droop control, the virtual synchronous machine, dispatchable virtual oscillator control, and the synchronverter within a unified small-signal and electromagnetic-transient simulation framework. Using a modified IEEE benchmark network, the study quantifies frequency nadir, rate of change of frequency (RoCoF), and transient settling time under load and generation disturbances. Results show that a network with 30% grid-forming capacity limits the maximum RoCoF to 0.58 Hz/s at 100% inverter penetration, compared with 2.9 Hz/s for an all-grid-following system, keeping the frequency excursion within statutory limits.

The findings provide system planners with practical guidance on the selection of grid-forming control and the minimum grid-forming share required for secure operation of low-inertia networks.