Patent ID: 8154139

Claim:
A method for controlling the rotational speeds of wind turbines, comprising: determining rotor rotational speeds of a first and a second wind turbine; determining rotor azimuth angles of the first and the second wind turbine; calculating a first speed control value for the first wind turbine, based on the determined rotor azimuth angles and rotor rotational speeds, and a second speed control value for the second wind turbine, based on the determined rotor azimuth angles and rotor rotational speeds, wherein the speed control values are calculated such that they lead to an adjustment of the first and second wind turbines such that the rotor azimuth angle of the first wind turbine is equal to the rotor azimuth angle of the second wind turbine after speed adjustment or the rotor azimuth angle of the first turbine is equal to modulus[(360 degrees) divided by (number of blades)] of the rotor azimuth angle of the second wind turbine after speed adjustment, and wherein calculating the speed control value comprises determining a synchronized rotor speed value based on a mean value of the rotor rotational speeds; and adjusting the rotor rotational speed of the first wind turbine according to the first speed control value and the rotor rotational speed of the second wind turbine according to the second speed control value.