The invention relates to a control device for a wind power plant having an electrical system and a rotor including a plurality of rotor blades driven by wind, and outputting a mechanical rotor power to the electrical system. The system converts the mechanical rotor power at least partially into electrical power. The control device includes a blade sensor associated with at least one of the rotor blades and measuring at least one physical property of the rotor blade dependent on at least one characteristic value of a wind field describing the wind at the location of the rotor. The blade sensor generates a blade sensor signal characterizing the physical property. The control device also includes an estimation unit to determine an estimated value for the electrical power as a function of the blade sensor signal.
