Grid frequency volatility in future low inertia scenarios: challenges and mitigation options

Electricity grids across the world are rapidly changing to accommodate an increasing penetration of renewable generation, but concerns have been raised about the stability of grids during and after this transition. The volatility of the frequency of the grid is a commonly used metric for stability. Here we analyse historic frequency data from Great Britain to gain an understanding of the past and current state of frequency volatility and some of the driving forces behind patterns and trends. We show that frequency volatility increased appreciably in 2017 and 2018. Using predicted 2030 inertia profiles, we also determine the future frequency response requirements of the grid in two different situations: after a large infeed loss and during normal day-to-day operation. In normal day-to-day operation, the frequency volatility does not drastically deteriorate until an inertia level around 20% of current levels (inertia from nuclear and demand only). At this low level, a significant portion of the frequency response capacity needs to be fast acting for successful mitigation. Increasing the capacity of slow acting response alone is actually found to be detrimental. Low inertia has a much greater effect on frequency response requirements in a large infeed loss situation.