Frequency and Voltage Compliance Capability of Grid-Forming Wind Turbines in Offshore Wind Farms in Weak Grids with a Power Imbalance

Grid-forming wind turbines are a promising technology for weak grids with a high penetration of converter-based power sources. The droop control, the synchronverter, and the virtual synchronous machine grid-forming control topologies are benchmarked by voltage and frequency stability performance from a frequency disturbance under different grid conditions (by varying short-circuit ratio, X/R ratio, and the inertia). The wind turbines are modelled in an offshore wind farm application and the frequency disturbance are scaled to 5% of the installed capacity. The study have shown that the virtual synchronous machine performs best regarding frequency and voltage compliance in weak grids under a frequency disturbance. DC-link modelling is essential for dynamic simulations of grid-forming converters, as grid perturbations can drain the link for energy.