Frequency Control of Highly Renewable Electrical Grids With Battery Power

The integration of renewable energy sources presents significant challenges to power system stability due to the reduced presence of synchronous generators. These generators provide mechanical inertia, which helps buffer the grid against rapid frequency fluctuations. This study investigates the impact of reduced inertia on frequency stability and evaluates the potential of Battery Energy Storage Systems (BESS) to mitigate large frequency deviations and prevent frequency collapse. A nine-bus admittance network is simulated under four different grid compositions C1-C4 representing increasing shares of renewable, non-inertia-based generation. In each case, the system is subjected to a sudden load increase, and the resulting frequency deviation, rate of change of frequency (RoCoF), and stabilization time are analyzed. Two types of reserves are implemented: a Fast Frequency Reserve (FFR) using batteries and a Frequency Control Reserve (FCR) representing governor-based control. The results show that BESS significantly reduce frequency drops and delay potential frequency collapse. Overall, the study concludes that BESS enhance grid frequency stability across varying levels of inertia-based generation.