automatic Frequency Restoration Reserve
With the Frequency Restoration Reserve products automatic Frequency Restoration Reserve (aFRR) and manual Frequency Restoration Reserve (mFRR), the system balance of each control area in the European interconnected grid is balanced. While all TSOs in the interconnected grid are equally responsible for the frequency and the FCR is activated regardless of the source of the frequency deviation, each TSO is responsible for balancing the system balance.
In contrast to FCR, aFRR is divided into positive (electricity feed-in) and negative aFRR (electricity withdrawal). If the system balance is oversupplied, i.e. more electricity is produced than consumed, negative aFRR compensates for the surplus. If the system balance is undersupplied, i.e. more electricity is consumed than produced, the deficit is offset by positive aFRR.
The TSOs determine the demand for aFRR via the control area balance. This results from the difference between the planned and actual exports or imports of electricity. Adjusted for the activated FCR, this is used to determine the demand, which serves as the input variable for the power frequency controller that each TSO operates. This distributes the demand to the aFRR providers, which have a direct connection to the grid control system of the connected TSO in order to be able to exchange data in real time. The aFRR providers must provide the requested power within five minutes. The majority of aFRR in Germany is provided by pumped storage power plants, which are particularly well suited to meet the high requirements of aFRR. The demand and the resulting activation are determined every four seconds (“control cycle”). aFRR is called up continuously. The German TSOs work very closely in German network rules association zusammen. In addition, the European TSOs optimize the activation of aFRR via the PICASSO & IGCC (aFRR work market)