Preventing wind turbine misalignment situations

1. A combination comprising:

a horizontal wind turbine including a nacelle, a rotor, rotor blades, a yaw system that moves the nacelle around a vertical yaw axis to position the rotor blades in an optimal position that is parallel to a wind direction, at least one sensor disposed within the wind turbine for measurement of a parameter that can be used to determine an internal deviation value of a position of the rotor blades from the optimal position, and a control system configured to prevent misalignment of the horizontal wind turbine, the control system comprising:

an acquisition unit that retrieves value of the parameter measured by the at least one sensor;

a calculation unit that calculates an external deviation value of the rotor blades from the optimal position using an optimization algorithm for determining an efficiency function y=ƒ(θ) that maximizes efficiency of the wind turbine by (i) forcing the yaw system to oscillate the nacelle at a frequency and amplitude that progressively orients the nacelle to a position that maximizes the efficiency function, (ii) filtering low frequencies to attenuate components that generate wind and meteorological characteristics, (iii) filtering high frequencies to attenuate components of the wind turbine, and (iv) measuring a position of maximum power in the forced oscillation to determine an optimal alignment θ* of the nacelle; and

a deviation comparison unit that determines a difference between the external deviation value calculated by the calculation unit and the internal deviation value determined from the measurement of the at least one sensor;

wherein the internal deviation value is based upon the measurement of the at least one sensor disposed within the wind turbine without any measurements taken by other devices external to the wind turbine;

wherein, if the difference between the external deviation value and the internal deviation value exceeds a preset value, the control system commands the yaw system to adjust the position of the nacelle to take account of the external deviation value; and

wherein the calculation unit further calculates the efficiency function by determining a ratio between an obtained generated power and a theoretically producible power, wherein the theoretically producible power is based on parameters including rotor diameter and maximum power and wind speed coefficients.

2. The control system according to claim 1 , wherein the theoretically producible power is calculated by multiplying a configurable parameter that is characteristic of constants inherent in the wind turbine, the constants comprising the rotor diameter, maximum parameter and wind speed coefficients, the configurable parameter comprising a product of air density, a rotor surface and a coefficient for maximum power.

3. The control system according to claim 1 , wherein the preset value is between 50 and 100.

4. The control system according to claim 1 , wherein the control system prevents oscillation of the nacelle only when a yawing function or a twist limit function of the nacelle is activated.

5. The control system according to claim 1 , wherein the optimization algorithm is an Extremum Seeking Control (ESC) algorithm.

6. The control system according to claim 1 , wherein the optimization algorithm is a Hierarchical Optimistic Optimization (HOO) algorithm based on yaw sweeps.

7. The control system according to claim 1 , wherein the optimization algorithm is a Modified Secant algorithm based on a Brent method.

8. The control system according to claim 1 , wherein the wind turbine comprises a plurality of sensors which are configured and arrange for speed measurement, wind direction measurement, power measurement and rotor rotation measurement.