A method for controlling a wind power installation, the wind power installation having an aerodynamic rotor which is operated with variable speed and which has rotor blades that are adjustable in their blade angle, wherein - the wind power installation is controlled in a partial-load range by an open-loop operating-characteristic control, which uses an operating characteristic, wherein - the operating characteristic presets a relationship between the rotational speed and a generator state variable to be set, the generator state variable to be set being a generator power or a generator torque, and - the operating-characteristic control takes place such that a value of the generator state variable preset by the operating characteristic is set in dependence on a detected speed, and - the wind power installation is controlled in a full-load range by a closed-loop pitch control, in which the rotational speed is controlled to a speed setpoint value by adjusting the blade angles, wherein - in at least one presettable speed range of the partial-load range and/or in a transitional range from the partial-load range to the full-load range, the wind power installation is controlled by a speed-power control, in which the rotational speed is controlled to a speed setpoint value by adjusting the generator state variable, characterized in that - the speed-power control takes place such that - in an outer cascade, a first acceleration setpoint value (a s) of the rotor is determined from a comparison of a preset setpoint speed with a detected actual speed by way of a first closed-loop controller, - in an inner cascade, a generator setpoint value is determined as a setpoint value for the generator state variable from a comparison of the first acceleration setpoint value with a detected acceleration actual value of the rotor by way of a second closed-loop controller. - the wind power installation is controlled in a partial-load range by an open-loop operating-characteristic control, which uses an operating characteristic, wherein - the operating characteristic presets a relationship between the rotational speed and a generator state variable to be set, the generator state variable to be set being a generator power or a generator torque, and - the operating-characteristic control takes place such that a value of the generator state variable preset by the operating characteristic is set in dependence on a detected speed, and - the operating characteristic presets a relationship between the rotational speed and a generator state variable to be set, the generator state variable to be set being a generator power or a generator torque, and - the operating-characteristic control takes place such that a value of the generator state variable preset by the operating characteristic is set in dependence on a detected speed, and - the wind power installation is controlled in a full-load range by a closed-loop pitch control, in which the rotational speed is controlled to a speed setpoint value by adjusting the blade angles, wherein - in at least one presettable speed range of the partial-load range and/or in a transitional range from the partial-load range to the full-load range, the wind power installation is controlled by a speed-power control, in which the rotational speed is controlled to a speed setpoint value by adjusting the generator state variable, characterized in that - the speed-power control takes place such that - in an outer cascade, a first acceleration setpoint value (a s) of the rotor is determined from a comparison of a preset setpoint speed with a detected actual speed by way of a first closed-loop controller, - in an inner cascade, a generator setpoint value is determined as a setpoint value for the generator state variable from a comparison of the first acceleration setpoint value with a detected acceleration actual value of the rotor by way of a second closed-loop controller. - in an outer cascade, a first acceleration setpoint value (a s) of the rotor is determined from a comparison of a preset setpoint speed with a detected actual speed by way of a first closed-loop controller, - in an inner cascade, a generator setpoint value is determined as a setpoint value for the generator state variable from a comparison of the first acceleration setpoint value with a detected acceleration actual value of the rotor by way of a second closed-loop controller.