Influence of wind turbine behaviour on the primary frequency control of the British transmission grid

Abstract

System frequency of a synchronous power system varies with the imbalance of energy supplied and the electrical energy consumed. When large generating blocks are lost, the system undergoes a frequency swing relative to the size of the loss. Any deviation in the system frequency is limited using frequency responsive plant. Changes have occurred to the generation mix of the British transmission system in the past 10 years. This has influenced the type of machines contracted for frequency response services. Future increased levels of wind turbines will also influence the operational characteristics of the system and warrant investigation. A process to optimise the response requirements while maintaining statutory limits on frequency deviation has been developed. This method requires suitable load and generator models to replicate transmission system performance. Validation of the complete system against historic loss events has established confidence in the method. A review of the current system with the dynamic model showed that utilising CCGT plant for responsive services requires additional primary response in some cases. Simulations including extra wind generation have shown that under appropriate circumstances, there is a potential to reduce the primary response requirement in the future. The secondary response requirements are maintained in all cases.