Frequency Containment Reserve (FCR) is a primary frequency regulation service in the power system, designed to quickly respond within a few seconds to stabilize the grid frequency when deviations occur in the grid frequency (usually within ±200 mHz). FCR is the first line of defense in maintaining the instantaneous balance of the power system and is a core component of the market-based frequency regulation service system in the European mainland synchronous grid (such as Germany, France, the Netherlands, and other countries).
