System and method for controlling a wind turbine

1. A system for controlling a wind turbine, comprising:

meteorological instruments for measuring ambient climate conditions, including an average ambient temperature, an average ambient relative humidity and an average ambient solar influx, and generating meteorological signals related thereto;

a memory for keeping in memory an icing tolerance;

a first calculator for calculating an overall icing probability adjusted as a function of the average ambient solar influx, the average ambient temperature, and the average ambient relative humidity; and

a controller for stopping the wind turbine when the overall icing probability is greater than the icing tolerance.

2. The system according to claim 1 , wherein the memory stores reference efficiency curves and an efficiency deviation tolerance, and the system further comprises:

sensors for detecting an average power generated by the wind turbine, an average position of the wind turbine blades, and an average wind speed proximate the wind turbine, and for generating efficiency signals based thereon; and

a second calculator for calculating the actual efficiency of the wind turbine based on the efficiency signals, the controller stopping the wind turbine when a deviation between the actual efficiency and an average efficiency calculated based upon the reference efficiency curves is greater than an efficiency deviation tolerance.

3. The system according to claim 1 , wherein the first calculator comprises:

first means for calculating a first relative humidity variable associated with the average ambient temperature, said first variable being obtained through interpolation of a first characteristic curve of characteristic variables of relative humidity as a function of a characteristic ambient temperature;

second means for calculating a second relative humidity variable resulting from the subtraction of a lower limit value from the first variable;

third means for calculating a first partial probability of icing corresponding to a first degree of approach between 0.0 and 1.0 of the ambient average humidity towards the first variable according to a fuzzification operation to obtain membership degrees of the ambient average humidity to the first variable and second variable;

fourth means for calculating a second degree of approach and a third degree of approach between 0.0 and 1.0 of the average ambient temperature towards a lower limit temperature and an upper limit temperature respectively according to a fuzzification operation to obtain membership degrees of the ambient average temperature to a series of temperatures comprising the lower limit temperature, the upper limit temperature, at least one additional temperature lower than the lower limit temperature and at least one additional temperature above the upper limit temperature;

fifth means for calculating a second partial probability of icing by adding the second degree of approach and the third degree of approach;

sixth means for calculating a third partial probability of icing by multiplying the first partial probability of icing and the second partial probability of icing;

seventh means for calculating a fourth degree of approach and a fifth degree of approach between 0.0 and 1.0 of the average ambient solar influx towards a lower limit solar influx and an upper limit solar influx respectively according to a fuzzification operation to obtain membership degrees of the average ambient solar influx to a series of values of solar influx comprising the lower limit solar influx and the upper limit solar influx and at least two other values of solar influx between the lower limit solar influx and the upper limit solar influx;

eighth means for calculating a upward adjustment parameter based on solar influx according to the formula:

upward adjustment parameter=((fourth degree of approach)×0.1)+1.0;

ninth means for calculating a downward adjustment parameter based on solar influx according to the formula:

downward adjustment parameter=1.0−((fifth degree of approach)×0.1);

tenth means for calculating an amplified probability of icing by multiplying the third partial probability of icing by the upward adjustment parameter and the downward adjustment parameter; and

eleventh means for calculating the overall icing probability of icing which is equal to the amplified probability of icing if the amplified probability of icing is equal or lower than 1.0 and the overall icing probability is equal to 1.0 if the amplified probability of icing is greater than 1.0.

4. The system according to claim 3 , wherein the second calculator comprises:

twelfth means for calculating a first theoretical wind speed associated with the average power generated by the wind turbine, said first theoretical wind speed being obtained through interpolation of a second generated power characteristic curve as a function of wind speed at a lowest temperature measured proximate the wind turbine;

thirteenth means for calculating a second theoretical wind speed associated with the average power generated by the wind turbine, said second theoretical wind speed being obtained through interpolation of a third generated power characteristic curve as a function of wind speed at a highest temperature measured proximate the wind turbine;

fourteenth means for calculating a sixth degree of approach and a seventh degree of approach between 0.0 and 1.0 of the average ambient temperature towards a first critical temperature and a second critical temperature respectively according to a fuzzification operation to obtain membership degrees of the ambient average temperature to a first critical temperature and a second critical temperature;

fifteenth means for calculating a first intermediate theoretical wind speed by multiplying the sixth degree of approach by the first theoretical wind speed, a second intermediate theoretical wind speed by multiplying the seventh degree of approach by the second theoretical wind speed, and a third intermediate theoretical wind speed by adding the first intermediate theoretical wind speed and the second intermediate theoretical wind speed;

sixteenth means for calculating a third theoretical wind speed associated with an average position of the wind turbine blades, said third theoretical wind speed being obtained through interpolation of a third characteristic curve of the position of the blades as a function of the wind speed at the lowest temperature measured proximate the wind turbine;

seventeenth means for calculating a fourth theoretical wind speed associated with the average position of the wind turbine blades, said fourth theoretical wind speed being obtained through interpolation of a fourth characteristic curve of the position of the blades as a function of the wind speed at the highest temperature measured proximate the wind turbine;

eighteenth means for calculating an eighth degree of approach and a ninth degree of approach between 0.0 and 1.0 of the average ambient temperature towards a third critical temperature and a fourth critical temperature respectively according to a fuzzification operation to obtain membership degrees of the average ambient temperature towards the third critical temperature and the fourth critical temperature;

nineteenth means for calculating a fourth intermediate theoretical wind speed by multiplying the eighth degree of approach by the third theoretical wind speed, a fifth intermediate theoretical wind speed by multiplying the ninth degree of approach by the fourth theoretical wind speed, and a sixth intermediate theoretical wind speed by adding the fourth intermediate theoretical wind speed and the fifth intermediate theoretical wind speed;

twentieth means for calculating a tenth degree of approach and an eleventh degree of approach between 0.0 and 1.0 of the average wind speed proximate the wind turbine towards a first critical wind speed and a second critical wind speed respectively according to a fuzzification operation in order to obtain membership degrees of the average wind speed towards a first critical wind speed and a second critical wind speed;

twenty-first means for calculating a seventh intermediate theoretical wind speed by multiplying the tenth degree of approach by a third intermediate theoretical wind speed, an eighth intermediate theoretical wind speed by multiplying the eleventh degree of approach by the sixth intermediate theoretical wind speed, and a ninth intermediate theoretical wind speed by adding the seventh intermediate theoretical wind speed and the eighth intermediate theoretical wind speed; and

twenty-second means for calculating the deviation between the actual efficiency and the average efficiency by subtracting the average wind speed proximate the wind turbine from the ninth intermediate wind speed.

5. A method for controlling a wind turbine, comprising the steps of:

a) measuring ambient climate conditions, including an average ambient temperature, an average ambient relative humidity and an average ambient solar influx, and generating meteorological signals related thereto;

b) storing in a memory an icing tolerance;

c) calculating an overall icing probability adjusted as a function of the average ambient solar influx, the average ambient temperature, and the average ambient relative humidity; and

d) stopping the wind turbine when the overall icing probability is greater than the icing tolerance.

6. The method of controlling the wind turbine according to claim 5 , further comprising the steps of:

e) storing in the memory reference efficiency curves and an efficiency deviation tolerance;

f) detecting an average power generated by the wind turbine, an average position of the wind turbine blades, and an average wind speed proximate the wind turbine, and generating efficiency signals based thereon;

g) calculating an actual efficiency of the wind turbine based on the efficiency signals; and

h) stopping the wind turbine when a deviation between the actual efficiency and an average efficiency calculated based on the reference efficiency curves is greater than the efficiency deviation tolerance.

7. The method of controlling the wind turbine according to claim 5 , wherein step c) comprises the sub-steps of:

i) calculating a first relative humidity setting associated with the average ambient temperature, said first setting being obtained through interpolation of a first characteristic curve of the relative humidity characteristic settings as a function of a characteristic ambient temperature;

ii) calculating a second relative humidity setting resulting from a subtraction of a lower limit value from the first setting;

iii) calculating a first partial probability of icing corresponding to a first degree of approach between 0.0 and 1.0 of the ambient average humidity towards a first setting according to a fuzzification operation in order to obtain membership degrees of the ambient average humidity towards the first setting and the second setting;

iv) calculating a second degree of approach and a third degree of approach between 0.0 and 1.0 of the average ambient temperature towards a lower limit temperature and an upper limit temperature respectively according to a fuzzification operation in order to obtain membership degrees of the ambient average temperature to a series of temperatures comprising the lower limit temperature, the upper limit temperature, at least one additional temperature lower than the lower limit temperature and at least one additional temperature greater than the upper limit temperature;

v) calculating a second partial probability of icing by adding the second degree of approach and the third degree of approach;

vi) calculating a third partial probability of icing by multiplying the first partial probability of icing and the second partial probability of icing;

vii) calculating a fourth degree of approach and a fifth degree of approach between 0.0 and 1.0 of the average ambient solar influx towards a lower limit solar influx and an upper limit solar influx respectively according to a fuzzification operation to obtain membership degrees of the average ambient solar influx to a series of values of solar influx comprising the lower limit solar influx and the upper limit solar influx and at least two other values of solar influx between the lower limit solar influx and the upper limit solar influx;

viii) calculating a solar influx upward adjustment parameter according to the formula:

upward adjustment parameter=((fourth degree of approach)×0.1)+1.0;

ix) calculating a solar influx downward adjustment parameter according to the formula:

downward adjustment parameter=1.0−((fifth degree of approach)×0.1);

x) calculating an amplified probability of icing by multiplying the third partial probability of icing by the upward adjustment parameter and the downward adjustment parameter; and

xi) calculating the probability of icing which is equal to the amplified probability of icing if the amplified probability of icing is equal or lower than 1.0 and the probability of icing is equal to 1.0 if the amplified probability of icing is greater than 1.0.

8. The method of controlling the wind turbine according to claim 7 , wherein step g) comprises the sub-steps of:

xii) calculating a first theoretical wind speed associated with the average power generated by the wind turbine, said first theoretical wind speed being obtained through interpolation of a second characteristic curve of power generated as a function of wind speed at a lowest temperature measured proximate the wind turbine;

xiii) calculating a second theoretical wind speed associated with the average power generated by the wind turbine, said second theoretical wind speed being obtained through interpolation of a third characteristic curve of power generated as a function of wind speed at a highest temperature measured proximate the wind turbine;

xiv) calculating a sixth degree of approach and a seventh degree of approach between 0.0 and 1.0 of the average ambient temperature towards a first critical temperature and a second critical temperature respectively according to a fuzzification operation to obtain membership degrees of the average ambient temperature towards the first critical temperature and the second critical temperature;

xv) calculating a first intermediate theoretical wind speed by multiplying the sixth degree of approach by the first theoretical wind speed, a second intermediate theoretical wind speed by multiplying the seventh degree of approach by the second theoretical wind speed and a third intermediate theoretical wind speed by adding the first intermediate theoretical wind speed and the second intermediate theoretical wind speed;

xvi) calculating a third theoretical wind speed associated with the average position of the wind turbine blades, said third theoretical wind speed being obtained through interpolation of a third characteristic curve of the position of the blades as a function of the wind speed at the lowest temperature measured proximate the wind turbine;

xvii) calculating a fourth theoretical wind speed associated with the average position of the wind turbine blades, said fourth theoretical wind speed being obtained through interpolation of a fourth characteristic curve of the position of the blades as a function of the wind speed at the highest temperature measured proximate the wind turbine;

xviii) calculating an eighth degree of approach and a ninth degree of approach between 0.0 and 1.0 of the average ambient temperature towards a third critical temperature and a fourth critical temperature respectively according to a fuzzification operation for obtaining membership degrees of the average ambient temperature towards the third critical temperature and the fourth critical temperature;

xix) calculating a fourth intermediate theoretical wind speed by multiplying the eighth degree of approach by a third theoretical wind speed, a fifth intermediate theoretical wind speed by multiplying the ninth degree of approach by the fourth theoretical wind speed, and a sixth intermediate theoretical wind speed by adding the fourth intermediate theoretical wind speed and the fifth intermediate theoretical wind speed;

xx) calculating a tenth degree of approach and an eleventh degree of approach between 0.0 and 1.0 of the average wind speed proximate the wind turbine towards a first critical wind speed and a second critical wind speed respectively according to a fuzzification operation to obtain membership degrees of the average wind speed towards the first critical wind speed and the second critical wind speed;

xxi) calculating a seventh intermediate theoretical wind speed by multiplying the tenth degree of approach by the third intermediate theoretical wind speed, an eighth intermediate theoretical wind speed by multiplying the eleventh degree of approach by the sixth intermediate theoretical wind speed, and a ninth intermediate theoretical wind speed by adding the seventh intermediate theoretical wind speed and the eighth intermediate theoretical wind speed; and

xxii) calculating the deviation between the actual efficiency and average efficiency by subtracting the average wind speed proximate the wind turbine from the ninth intermediate wind speed.

9. The system according to claim 4 , wherein the first calculator comprises a twenty-third means for comparing the overall icing probability with an excess probability, activating a timer if the value of the overall icing probability is equal or greater than the excess probability, resetting the timer if the value of the overall icing probability is less than the excess probability, and the controller stops the wind turbine if the timer remains active for a duration exceeding a critical time period.

10. The system according to claim 2 , wherein the second calculator comprises a means for adjusting the deviation between the actual efficiency and the average efficiency for the wind turbine before comparing the deviation to the deviation tolerance, by adding to the deviation a deviation average between the actual efficiency and the average efficiency for a series of other wind turbines adjacent to said wind turbine comprising the control system and by dividing the result of the addition by two.

11. The system according to claim 1 , wherein the memory stores reference efficiency curves and an efficiency deviation tolerance, the system further comprising:

sensors for detecting the average power generated by the wind turbine, an average position of the wind turbine blades, and an average wind speed proximate the wind turbine, and generating efficiency signals based thereon;

a second calculator for calculating an actual efficiency of the wind turbine based on the efficiency signals; and

a third calculator comprising:

first means for calculating a sensitivity parameter associated with the overall probability of icing, said sensitivity parameter being obtained through interpolation of a characteristic curve of the sensitivity parameter as a function of the probability of icing; and

second means for calculating an adjusted efficiency deviation tolerance by subtracting the sensitivity parameter from the efficiency deviation tolerance;

the controller stopping the wind turbine when a deviation between the actual efficiency and the average efficiency calculated based on the reference efficiency curves is greater than the adjusted efficiency deviation tolerance.

12. The method of controlling the wind turbine according to claim 5 , further comprising the steps of comparing the overall icing probability with an excess probability, activating a timer if the value of the overall icing probability is equal or greater than the excess probability, resetting the timer if the value of the overall icing probability is less than the excess probability, and stopping the wind turbine if the timer remains active for a duration exceeding a critical time period.

13. The method of controlling the wind turbine according to claim 6 , further comprising the step of adjusting the deviation between the actual efficiency and average efficiency for the wind turbine before comparing the deviation to the deviation tolerance, by adding to the deviation an average of deviations between the actual efficiency and average efficiency for a series of other wind turbines adjacent to the wind turbine comprising the control system and by dividing the result of the addition by two.

14. The method of controlling the wind turbine according to claim 5 , further comprising the steps of:

e) storing in the memory the reference efficiency curves and an efficiency deviation tolerance;

f) detecting an average power generated by the wind turbine, an average position of the wind turbine blades, and an average wind speed proximate the wind turbine, and generating efficiency signals based thereon;

g) calculating an actual wind turbine efficiency based on the efficiency signals;

h) calculating an adjustment parameter associated with the overall icing probability, said adjustment parameter being obtained through interpolation of a characteristic curve of the adjustment parameter as a function of the probability of icing;

i) calculating a deviation tolerance of the adjusted efficiency by subtracting the adjustment parameter from the efficiency deviation tolerance; and

j) stopping the wind turbine when a deviation between the actual efficiency and an average efficiency calculated based on reference efficiency curves is greater than the adjusted efficiency deviation tolerance.