Dynamic studies for 100% converter-based Irish power system

Given increasing shares of wind and/or solar power in many power systems, the possibility of a 100% power converter-based system becomes more plausible. Consequently, the dynamic response of the Irish transmission system with 100% (grid-following and grid-forming) power converters under 3-phase faults is investigated. Time domain simulations show that when active or reactive current prioritisation limits are applied, grid-forming converters can introduce large high-frequency oscillations, but a scaling-down current limitation approach can help to avoid such problems. Furthermore, applying scaling-down current limits, together with freezing the virtual angular speed, for a grid-forming converter, can limit the current and enhance transient stability during faults. Finally, with modified controls applied to the grid-following converters, the grid-forming requirement can be reduced from approximately 40% to less than 30%, with the future Irish grid remaining robust against bolted 3-phase faults, and oscillations quickly damped out during and post fault.