Patent ID: 7504738

Claim:
A wind turbine comprising: an asynchronous generator having a rotor and a stator; means for determining an actual torque-speed curve of said generator; means for determining an actual grid frequency; means for determining a shifted torque-speed curve of said generator to the determined actual grid frequency if the determined actual grid frequency is higher than a predetermined upper frequency limit or lower than a predetermined lower frequency limit, wherein said means for determining a shifted torque-speed curve is further adapted to determine the shifted torque-speed curve such that an increase in the rotor voltage of said generator rotor is counteracted when shifting the actual torque-speed curve to the shifted torque-speed curve; and means for shifting the actual torque-speed curve of said generator to the shifted torque-speed curve, wherein said means for determining a shifted torque-speed curve is adapted to determine, in the under excited range, a shifted torque-speed curve assigning a higher speed to the same torque as compared to the actual torque-speed curve, wherein said means for determining a shifted torque-speed curve is further adapted to determine, in the overexcited range, a shifted torque-speed curve assigning a lower speed to the same torque as compared to the actual torque-speed curve.