Analysis of optimal grid-forming converter penetration in AC connected offshore wind farms

The modern electricity network is seeing a trend in the replacement of fossil fuel power plants with converter interfaced generation as worldwide efforts are made to combat climate change. New converter control structures such as grid -forming are seen as a key building block for maintaining the stability of the future power system. Moreover, wind power is the fastest growing renewable technology in the UK with ambitious targets set for installed capacity in the coming decade. While the benefits and drawbacks of the technology have been explored, little attention has been given to how many grid -forming converters will be needed to stabilise the modern network. Is there such a thing as too much grid -forming? This paper utilises an impedance -based windfarm model with the capability to include unique control systems on each turbine to present a smallsignal based methodology for determining the penetration limits of grid -forming technology. Key stability and screening metrics are applied to identify the penetration that provides the strongest and most stable system. Three key points are specified: the critical, optimal and maximum penetrations. Moreover, findings suggest providing enhanced system strength via converters is only applicable to a certain extent where further interactions cause increased stability issues.