Wind power installation

A wind power installation comprising:

• an aerodynamic rotor and a rotor blade coupled to the aerodynamic rotor, and
• a flow control device on the rotor blade, wherein the flow control device is configured to actively influence a flow over the rotor blade,
• wherein the flow control device comprises a rotor blade surface opening and at least one fan for providing a controllable air flow through the rotor blade surface opening,
• wherein the flow control device is configured to draw off air or blow out air or both through the rotor blade surface opening by way of the controllable air flow,
• wherein the wind power installation has a controller configured to control an amount of the controllable air flow through the rotor blade surface opening according to at least one of the following rules:
• if a rotational speed threshold value of a rotational speed of the rotor is exceeded, increasing a maximum controllable air flow successively with increasing rotational speed;
• and
• if a torque threshold value of a torque of the rotor is exceeded, increasing the maximum controllable air flow successively with increasing torque,
• wherein the flow control device comprises a plurality of rotor blade surface openings along a length of the rotor blade, wherein the at least one fan of the flow control device has adjustable speeds and is configured to vary an amount of the air flow through the rotor blade surface openings along the length of the rotor blade,
• wherein the controller is configured to control the amount of the controllable air flow through the rotor blade surface openings such that the amount of the air flow decreases over the length of the rotor blade, and
• wherein the controller is configured to control the amount of the controllable air flow through the rotor blade surface openings such that the decrease in the amount over the length of the rotor blade decreases with lower atmospheric air density.