aFRR (automatic Frequency Restoration Reserve) is a secondary reserve mechanism in the power system, used for the automatic restoration of balance between electricity generation and consumption, ensuring the system frequency remains close to its nominal value (typically 50 Hz in Europe).
Key features of aFRR:
Purpose:
- Stabilize the frequency in the power system automatically.
- Enable the transmission system operator (e.g., Polskie Sieci Elektroenergetyczne in Poland) to restore balance after disturbances in the grid.
Automation:
- aFRR operates fully automatically, based on signals sent by the Automatic Generation Control (AGC) system.
- Changes in the output of generation or load units providing aFRR are introduced dynamically and in a short time frame.
Timeframe:
- aFRR operates within a range from a few seconds to several minutes, restoring system frequency to its nominal level.
- It reacts faster than mFRR (manual Frequency Restoration Reserve) and over a longer timeframe than FCR (Frequency Containment Reserve).
aFRR Providers:
- Conventional power plants capable of flexible power adjustments.
- Renewable energy sources with controllable generation capacity (e.g., wind and solar farms with energy storage systems).
- Energy storage systems and Demand Side Response (DSR) technologies that can reduce consumption or supply power as needed.
Importance for the power system:
- Ensures the stability and reliability of the power system.
- Reduces the risk of power outages due to grid disturbances.
- Facilitates greater integration of renewable energy sources by compensating for their variable generation.
Differences between aFRR, FCR, and mFRR:
- FCR (Frequency Containment Reserve): Reacts in real time (milliseconds to seconds) to stop frequency drops or rises immediately following a disturbance.
- aFRR: Automatically restores balance after a few seconds, operating for a duration of several minutes.
- mFRR (manual Frequency Restoration Reserve): Manually activated reserve used by the operator for larger or prolonged disturbances that require additional support.
In Poland, Polskie Sieci Elektroenergetyczne (PSE) oversees the delivery and management of aFRR, coordinating efforts with market participants to ensure the safety and stability of the power system.
