Frequency Support Optimization in Unbalanced Microgrids through Grid-forming Converters

Abstract

The proliferation of distributed renewable generation inherently reduces system inertia, resulting in weaker distribution networks microgrids where rapid and robust frequency support is vital. To provide this essential stability, these modern systems increasingly rely on grid-forming converters and synchronous units. However, inherent phase unbalances create asymmetrical voltage and current profiles that severely restrict the active power capability of balanced three-phase sources. During frequency events, balanced power injections can trigger voltage protections on depressed or elevated phases, creating a critical operational bottleneck. To address this, this paper investigates the potential of utilizing unbalanced grid-forming converters to maximize the frequency support capability in unbalance-constrained microgrids. By employing a centralized Genetic Algorithm and Optimal Power Flow framework, the study quantifies and compares the performance of conventional balanced power-frequency responses against strategic unbalanced operation, proving that flexible unbalanced grid-forming operation successfully unlocks stranded network capacity.