What is aFRR (automatic frequency restoration reserve) and how does it work?
What is aFRR (automatic frequency restoration reserve)
and how does it work?Definition
The automatic Frequency Restoration Reserve (aFRR), also known as secondary reserve, is a reserve in the power grid that helps to keep the grid frequency stable. To keep the frequency within certain thresholds, the Transmission System Operators (TSOs) activate balancing services like aFRR, which they acquire from Balancing Service Providers (BSPs). Countries differ in their specifications but after European harmonization of the balancing markets, BSPs need to ensure that they provide the reserve within 5 minutes (Full Activation Time). As the secondary reserve, aFRR replaces the FCR gradually after 30 seconds, the mFRR, the tertiary reserve, supports or partially substitutes the aFRR after 12.5 minutes.