What are the stability requirements and why are they necessary?
Capacity deliveries from resources activated on the FCR ancillary services markets are part of a closed-loop control system aimed at keeping the power system frequency within acceptable limits. While an individual delivery generally has limited impact on the system as a whole, it is still crucial that each delivering unit contributes with stabilizing feedback, as the overall system stability depends on the stability of its individual components.
By measuring the response of a unit following a sinusoidal frequency signal, the unit’s stability can be determined. From the results of these sine tests, gain and phase shift are calculated. The results are presented in a so-called Nyquist diagram, which shows whether the response meets the stability requirement.
These calculations must be performed separately for FCR-D and FCR-N. For more information, see section 3.2 in the FCR Technical Requirements (PDF) (.pdf) Opens in a new window