Method for controlling an offshore floating tower wind turbine, and control system and wind turbine that use the method

A control system for controlling an offshore tower wind turbine, said wind turbine comprising a rotor with a plurality of blades and a plurality of actuators, the control system comprising:

• one or more monitoring sensors for monitoring a plurality of physical parameters of said wind turbine;
• and
• a controller adapted to adjust a power P with the wind turbine and a pitch angle A of the plurality of blades, wherein the wind turbine, the monitoring sensors and the controller are configured to carry out the following steps:
• a. producing the power P with the wind turbine, wherein P is variable over time and dependent on a relative wind speed Vw at which a wind strikes the rotor, where Prated is a rated power of the wind turbine that may be achieved when the relative wind speed Vw is equal to or greater than a rated wind speed Vr;
• b. regulating the pitch angle A of the plurality of blades with the plurality of actuators and the controller, such that:
• i. given the relative wind speed Vw, an increase in the pitch angle A of the plurality of blades entails a decrease in a rotation speed of the rotor and/or of the produced power P and/or of a thrust that the wind exerts on the rotor;
• ii. given the relative wind speed Vw, a decrease in the pitch angle A of the plurality of blades entails an increase in the rotation speed of the rotor and/or of the produced power P and/or of the thrust that the wind exerts on the rotor;
• iii. the pitch angle A of the plurality of blades has a minimum value which is assigned, by convention, a 0-degree pitch value for the plurality of blades;
• iv. given the relative wind speed Vw greater than Vr, there is a theoretical pitch angle of the plurality of blades At greater than 0 degrees, such that the produced power P is substantially equal to Prated;
• c. experiencing, in at least one working condition, that generate a speed of the wind turbine Va, which is understood as being positive (Va>0) when the wind turbine is displaced in a direction substantially contrary to the direction of the wind and is understood as being negative (Va<0) when the wind turbine is displaced in a direction coinciding substantially with the direction of the wind;
• d. monitoring the speed of the wind turbine Va directly or indirectly with the monitoring sensors;
• establishing at least during part of the time for which the speed of the wind turbine Va is positive (Va>0) and the relative wind speed Vw is greater than Vr (Vw>Vr), a pitch angle A of the plurality of blades less than At (A<At), wherein the wind turbine produces a power P greater than Prated (P>Prated);
• and/or
• establishing at least during part of the time for which the speed of the wind turbine Va is negative (Va<0) and the relative wind speed Vw is greater than Vr (Vw>Vr), a pitch angle A of the plurality of blades greater than At (A>At), wherein the wind turbine produces a power P less than Prated (P<Prated).