A wind farm with at least two wind turbines (1, 2, 3, 4) connected to a power grid is provided, said wind farm further comprising a control unit (5) connected to said at least two wind turbines (1, 2, 3, 4), and a sensor unit (6) connected to said power grid and said control unit (5), wherein said sensor unit (6) is adapted to measure the grid frequency of said power grid and to transmit said measured grid frequency to said control unit (5), and wherein said control unit (5) is adapted to control the output of real power of said wind farm according to said measured grid frequency. Furthermore, a method for operating a wind farm is proposed, said method comprising the steps of measuring the grid frequency with a sensor unit, transmitting said measured grid frequency to a centralized control unit, determining whether the measured grid frequency lies outside a predetermined range, and, if the measured grid frequency lies outside said predetermined range, selecting at least one out of the at least two wind turbines comprised in said wind farm by said centralized control unit and regulating the power output of said selected at least one wind turbine.