Method for determining a setpoint signal of a wind energy conversion system, the method, in a system comprising at least one signal processing device (13, 14, 15), comprising: - providing a first input signal, comprising system frequency values of an electric power system, and a second input signal comprising an angular speed value of a wind energy conversion system; - determining, from the first input signal, an intermediate signal comprising system frequency deviation values, the system frequency deviation values indicating deviations between the system frequency values and a target frequency value; - determining, from the intermediate signal and the first input signal, a power correction signal comprising a first power value; - determining, from the second input signal, a first reference signal comprising a second power value corresponding to a point of maximum power extraction of the wind energy conversion system; - determining, from the power correction signal and the first reference signal, a setpoint signal for setting an output power value of the wind energy conversion system; and - storing or releasing kinetic energy in the rotating mass of the wind energy conversion system based on the first power value of the power correction signal; wherein said determining of the power correction signal comprises: - identifying frequency bands of dominating frequency components in the intermediate signal; - determining the number of dominating frequency components; - determining a number of activated band-pass filter units from the number of dominating frequency components; - using the activated band-pass filter units to filter the intermediate signal, resulting in partial signals; - summing the partial signals to yield the first power value. - providing a first input signal, comprising system frequency values of an electric power system, and a second input signal comprising an angular speed value of a wind energy conversion system; - determining, from the first input signal, an intermediate signal comprising system frequency deviation values, the system frequency deviation values indicating deviations between the system frequency values and a target frequency value; - determining, from the intermediate signal and the first input signal, a power correction signal comprising a first power value; - determining, from the second input signal, a first reference signal comprising a second power value corresponding to a point of maximum power extraction of the wind energy conversion system; - determining, from the power correction signal and the first reference signal, a setpoint signal for setting an output power value of the wind energy conversion system; and - storing or releasing kinetic energy in the rotating mass of the wind energy conversion system based on the first power value of the power correction signal; - identifying frequency bands of dominating frequency components in the intermediate signal; - determining the number of dominating frequency components; - determining a number of activated band-pass filter units from the number of dominating frequency components; - using the activated band-pass filter units to filter the intermediate signal, resulting in partial signals; - summing the partial signals to yield the first power value.