Impact of Different Grid-Forming Inverter Control Strategies on System Strength and Frequency

This study aims to understand the impact of different grid-forming inverter (GFMI) control strategies on a larger power system and to investigate their contributions to system strength. Three mainstream GFMI control techniques are investigated and compared: Droop control, virtual synchronous generator (VSG), and synchronverter. The GFMI inverters with these control strategies are connected to a weak bus, using short circuit apparent power as the indicator. The 39-bus New England system is used as the test network for simulations under two scenarios: one with an all-synchronous generator system and the other with a partially renewable integrated system, each tested under two fault conditions. Based on the simulation results, VSG performs well in voltage regulation, while droop control proved efficient in frequency regulation, and the synchronverter exhibits precise reactive power control, closely emulating the behaviour of a synchronous generator. These findings provide valuable insights into the usefulness of different control strategies of GFMIs under complex grid conditions, identifying each strategy's strengths and drawbacks. Future work will explore ancillary grid services using GFMI to enhance system strength and address weak grid issues.