METHOD TO CONTROL THE OPERATION OF A WIND TURBINE

1 . A method to control an operation of a wind turbine, comprising: measuring a plurality of wind-related values and operating parameters of the wind turbine, the plurality of wind-related values and operating parameters of the wind turbine include electrical output power, parameters of the rotating blade-system, accelerations and thrusts, which are impacting on a plurality of wind turbine components; generating respective time-based statistics using the measured values;

estimating at least one load of these loads: tower bending moment, blade bending moment and/or tower yawing moment, using the time-based statistics;

comparing the estimated loads with load threshold values, that are pre-determined for a given type of the wind turbine; and

controlling the operation of the wind turbine taking into account the load estimations so that respective loads are reduced.

2 . The method according to claim 1 , wherein the operating parameters comprise at least one of these measurements: a produced electrical output power of the wind turbine, a pitch angle of rotating blades of the wind turbine, a number of rotations per minute (rpm) of the rotating blades or the rotational speed of the rotating blades of the wind turbine, accelerations experienced by a nacelle, and/or thrusts, which are experienced by respective components of the wind turbine.

3 . The method according to claim 1 , wherein the plurality of wind-related values comprise characteristics of the wind such as wind speed, wind turbulences, the air temperature and/or the air moisture.

4 . The method according to claim 1 , wherein the respective time-based statistics comprises at least one of these: a n-second statistic of power, a n-second statistic of pitch, a n-second statistic of rpm, a n-second statistic of the wind as an estimation, a n-second statistic of the turbulence as an estimation, a n-second statistic of a processed nacelle side-to-side acceleration, a n-second statistic of a processed nacelle forward-backward acceleration, a n-second statistic of a processed nacelle resulting acceleration, and/or a n-second statistic of thrust estimates.

5 . The method according to claim 4 , wherein the time-based statistics cover a time period of several seconds up to a time period of several hours.

6 . The method according to claim 1 , wherein the time-based statistics are used to estimate at least one or a subset of these loads:

a first maximum absolute tower bending moment, while the moment is referred to a bottom end of a tower and is referred to a forward-backward movement of the tower as experienced in direction to the incoming wind,

a second maximum absolute tower bending moment, while the moment is referred to the bottom end of the tower and is referred to a side-to-side movement of the tower as experienced perpendicular to the direction of the incoming wind, a maximum absolute yawing moment in reference to a top of the tower,

a minimum blade root flap bending moment,

a maximum absolute blade root edge bending moment,

a cyclic tower bottom forward-backward fatigue bending moment,

a cyclic tower bottom side-to-side fatigue bending moment, and/or

a cyclic blade root flap fatigue bending moment.

7 . The method according to claim 1 , wherein all of the following control handles or a sub-set of the following control handles are used to reduce the loads:

a limiting pitch angle value is adjusted, and/or

the rotational speed of the rotating blades is curtailed, and/or

the electrical output power of the wind turbine is curtailed, and/or

a gain of a side-to-side tower damper is increased, and/or

a saturation limit of the side-to-side tower damper is increased.

8 . The method according to claim 6 , wherein the load estimators are grouped for the load-estimation:

wherein a first estimator is used to estimate these loads:

the first maximum absolute tower bending moment,

the minimum blade root flap bending moment, and

the maximum blade root edge bending moment, while

wherein a second estimator is used to estimate the second maximum absolute tower bending moment, while

wherein a third estimator is used to estimate the maximum absolute yawing moment in reference to the top of the tower, and

wherein a fourth estimator is used to estimate these loads:

the cyclic tower bottom forward-backward fatigue bending moment,

the cyclic tower bottom side-to-side fatigue bending moment, and

the cyclic blade root flap fatigue bending moment.

9 . The method according to claim 8 , wherein the respective load estimator is described by this formula:

{tilde over (L)} i =c i,1 s i,1 k +c i,2 s i,2 k +c i,3 s i,3 k

with:

{tilde over (L)} i as load estimate corresponding to load group i,

c i,1 -c i,3 as load model coefficients of load model i,

s i,1 -s i,3 as input signals of the load model i, and

k as weighting factor, 1<=k<=2.

and wherein the model coefficients are determined by aero-elastic simulations such that a highest possible correlation is achieved between the load estimate of each group and the loads within the group.