DE102010035055A1 - Method for adjusting angle of incidence of rotor blade of wind power plant, involves determining controller-based control value based on deviation of angle of incidence of rotor blade with respect to target value - Google Patents

Abstract

The method involves determining a compensated control value (310) for adjusting the angle of incidence of the rotor blade with respect to the target value based on a controller-based control value. The controller-based control value is determined based on the deviation of the angle of incidence of rotor blade with respect to the target value. The size of the tilt angle of the rotor blade is adjusted with respect to the target value and the compensated control value. Independent claims are included for the following: (1) device for adjusting angle of incidence of rotor blade of wind power plant; and (2) computer program product for adjusting angle of incidence of rotor blade of wind power plant.

Description

The present invention relates to a method and apparatus for adjusting an angle of incidence of a rotor blade of a wind turbine, and to a method for determining a compensation value for compensating for a bearing friction torque that affects adjusting an angle of incidence of a rotor blade of a wind turbine.

In wind turbines or wind turbines, for example with a horizontal axis and three rotor blades, the rotational speed above the rated wind speed is controlled by synchronous adjustment of the blade angle that is changed by changing the angle of attack of the rotor blades aerodynamic lift and thus the drive torque in such a way that the system can be kept in the range of the nominal rotational speed. At wind speeds above the shutdown speed this Blattverstellmechanismus is also used as a brake by the leaves are placed with the nose in the wind, so that the rotor delivers no significant driving torque more. As a result of this asymmetric aerodynamic load, pitching and yawing moments on the nacelle result from this collective pitch adjustment. The asymmetric loads arise z. As by wind shear in the vertical direction, boundary layers, yaw angle error, gusts and turbulence, impoundment of the flow at the tower, etc.

The US 7,160,083 B2 discloses a corresponding method to adapt a position of the rotor blades.

Against this background, with the present invention, a method for adjusting an angle of incidence of a rotor blade of a wind turbine, an apparatus using this method, a method for determining a compensation value for compensating a bearing friction torque, which influences setting of a pitch angle of a rotor blade of a wind turbine, and finally a corresponding computer program product according to the independent claims presented. Advantageous embodiments emerge from the respective subclaims and the following description.

The invention is based on the recognition that the accuracy of the position control of the pitch drive of a rotor blade of a wind turbine can be increased by estimating the friction torque in the blade bearing. For this purpose, certain measured variables are required, but in plants that are equipped with IPC (English: Individual Pitch Control, IPC), usually available anyway. Using IPC, the pitch or pitch angle of the blades is adjusted individually to reduce asymmetric aerodynamic loads. Typically, sensors are mounted in or on the rotor blades to measure the impact moments. These then serve as control variables for the individual blade adjustment. Other methods determine the pitching and yawing moments by measuring the gondola acceleration via gyroscopes or by sensors, which measure the deformations of system components caused by the loads by means of distance measurements and thereby determine the loads. For the implementation of IPC, it is necessary that the angle of attack of a rotor blade moves during one revolution on an approximately sinusoidal curve. This requires precise position control on the pitch drive. However, at the blade root of a wind turbine from the rotor blade large shear forces and tilting moments. These significantly determine the friction torque in the blade bearing. To position the rotor blade, the bearing friction torque must be overcome by the pitch drive. The largest part of the power of the drive is used, only a small part actually serves to accelerate the rotor blade about the pitch axis.

The advantages of the invention are that by including the Lagerreibmoments in the position control, the rotor blade can follow evenly a predetermined pitch curve and thus a jerky movement of the rotor blade can be avoided by the pitch axis due to the compensation of the friction in the blade bearing. It can therefore be made possible by friction compensation in the axis controller a more accurate pitch positioning in a wind turbine. Due to the increased position accuracy of the pitch axis, the potential of the individual adjustment of the pitch angle of the individual rotor blades can be better utilized.

The present invention provides a method of adjusting an angle of attack of a rotor blade of a wind turbine to a target value, the method comprising the following step:
Determining a compensated manipulated variable for setting the angle of attack on the setpoint value based on a controller-based manipulated variable, which represents a provided by a controller size for adjusting the angle of attack of the rotor blade to the desired value, and a compensation value for compensating a setting influencing Lagerreibmoments.

A wind turbine or wind turbine comprises a rotor with radially outwardly extending rotor blades. Typically, a rotor comprises a plurality of rotor blades, the most common configuration having three rotor blades. The rotor may be rotatably mounted about a horizontal axis of rotation. Each of the rotor blades is individually and independently of the other rotor blades in its angle of attack or pitch angle adjustable. The angle of attack of a rotor blade can be understood as the angle by which the rotor blade is adjusted at its holder in the blade bearing or rotated about a longitudinal axis of the rotor blade. The setpoint specifies a favorable for each specific operating situation of the plant for a given rotor blade angle of attack. The setpoint can be specified, for example, by the IPC control. To set the angle of attack to the setpoint, a controller-based manipulated variable is first determined by a position controller. This control-based manipulated variable may be suitable for driving a motor with which the rotor blade is rotated in order to adjust the angle of attack. As a rule, the controller-based manipulated variable specifies a value of a torque. This torque is adjusted by a pitch drive, such as an electric motor, by means of a subordinate current regulator.

According to the present invention, a compensation value is determined which adapts the controller-based manipulated variable such that at least approximately compensates for a bearing friction torque influencing the setting of the angle of incidence. The compensation value may be determined based on a rotational position of the rotor, the rotational speed of the rotor and a measured blade bending moment of a rotor blade. Ideally, the compensation value corresponds to the Lagerreibmoment to be compensated. The Lagerreibmoment acts in the bearing of the rotor blade and counteracts the pitch rotation of the rotor blade. The bearing friction torque depends, for example, on a wind force acting on the rotor blade and a rotational position of the rotor blade. The bearing friction torque is thus a constantly changing disturbance variable, which results in the setpoint being missed or not being reached sufficiently quickly if the angle of attack is set in accordance with the control-based manipulated variable. The combination of the controller-based manipulated variable and the compensation value results in the compensated manipulated variable. In comparison to the controller-based manipulated variable, the angle of attack of the rotor blade with the compensated manipulated variable, which takes into account the bearing friction torque, can be set more precisely and / or more quickly to the desired value.

The controller-based manipulated variable can be determined based on a deviation of the angle of attack from the desired value. The deviation occurs when the angle of attack has not yet reached the setpoint or a new setpoint is specified.

According to one embodiment, the compensation value may be determined based on at least one physical property of the rotor blade and / or at least one force acting on the rotor blade. The physical property of the rotor blade may be understood by known sizes of the rotor blade, such as the rotor radius, the rotor blade mass, the position of the rotor blade center of gravity, the pitch diameter of the rotor blade bearing or friction coefficient of the bearing. The forces and moments acting on the rotor blade can change over time and be measured or estimated directly or indirectly. The force can be caused for example by acting on the rotor blade wind, gravity or centrifugal force. In particular, the consideration of the force acting on the rotor blade has the advantage that the compensation value can be determined situation-related and accurately. Thus, the Lagerreibmoment can be optimally compensated.

Thus, the compensation value can be determined from a maximum acting in a rotor blade bearing of the rotor blade friction torque based on at least one rotor blade, a rotor blade rotational position, a rotor rotational speed and / or at least one blade root bending moment. Under a rotor blade characteristics in turn sizes, such as the rotor radius, the sheet mass, the position of the blade center of gravity in the sheet, the running diameter of the bearing used or friction coefficient can be understood. Under a blade root bending moment acting on the blade root or the blade bearing tilting moment can be understood.

The compensation value may also be based on a current pitch of the rotor blade. Thus, it can be considered whether the rotor blade is at rest or is being rotated just to change the angle of attack. Furthermore, the direction of rotation of the rotor blade can be taken into account.

In this case, an amount of the compensation value can be determined by the maximum friction torque acting in the rotor blade bearing and a sign of the compensation value by the current pitch velocity of the rotor blade, if the current pitch velocity of the rotor blade is non-zero. Furthermore, the amount of the compensation value can be determined by the smaller value of the maximum friction torque acting in the rotor blade bearing and an externally applied torque and a sign of the Compensation value are determined by the externally applied torque when the current pitch of the rotor blade is equal to zero. The friction torque in the blade bearing is opposite to the current direction of rotation. If the rotor blade is stationary, the bearing friction torque counteracts the torque acting on the bearing externally.

According to one embodiment, a step of varying the angle of attack of the at least one rotor blade based on the compensated control variable may be provided to adjust the angle of attack to the desired value. The compensated manipulated variable calculated according to embodiments of the present invention can thus be incorporated directly into an existing control and adjustment process sequence.

The present invention further provides a method for determining a compensation value for compensating a bearing friction torque, which influences an adjustment of an angle of incidence of a rotor blade of a wind turbine, the method comprising the following steps:
Determining a maximum acting in a rotor blade bearing of the rotor blade friction torque based on at least one rotor blade characteristic, a rotor blade rotational position, a rotor rotational speed and / or at least one blade root bending moment; and
Combining the maximum acting in the rotor blade bearing friction torque with a current pitch of the rotor blade to determine the compensation value, wherein an amount of the compensation value by the maximum friction in the rotor blade bearing friction and a sign of the compensation value determined by the current pitch of the rotor blade, if actual pitch velocity of the rotor blade is non-zero, and in which the amount of compensation value is determined by the smaller value of the maximum friction moment acting in the rotor blade bearing and an externally applied moment and a sign of the compensation value by the externally applied moment, if the current one Pitch of the rotor blade is zero.

The compensation value determined in this way maps as accurately as possible the friction to be overcome for a rotation of the rotor blade.

The present invention further provides an apparatus for adjusting a pitch angle of a rotor blade of a wind turbine to a target value, the apparatus comprising:
a device for determining a compensated manipulated variable for setting the angle of attack to the desired value based on a controller-based manipulated variable representing a variable provided by a controller for setting the angle of attack of the rotor blade on the desired value, and a compensation value for compensating a Lagerreibmoments influencing the setting.

Thus, the present invention provides an apparatus or pitch adjusting apparatus configured to perform the steps of the method of the invention. In particular, the device or the pitch angle adjuster may comprise means configured to execute each a step of one of the methods. Also by this embodiment of the invention in the form of a device or Anstellwinkeleinstellgeräts, the object underlying the invention can be achieved quickly and efficiently.

A device or a Anstellwinkeleinstellgerät can in the present case be understood as an electrical device that can set a pitch of a rotor blade of a wind turbine to a desired value. The device or the Anstellwinkeleinstellgerät may have an interface that may be designed in hardware and / or software. In the case of a hardware configuration, the interfaces may be part of a so-called system ASIC, for example, which includes a wide variety of functions of the device or the Anstellwinkeleinstellgeräts. However, it is also possible that the interfaces are their own integrated circuits or at least partially consist of discrete components. In a software training, the interfaces may be software modules that are present, for example, on a microcontroller in addition to other software modules.

Also of advantage is a computer program product with program code for carrying out a method according to the invention when the program is executed on a device.

The invention will be described by way of example with reference to the accompanying drawings. Show it:

1 a partial view of a rotor of a wind turbine, according to an embodiment of the present invention;

2 a block diagram of a control loop for adjusting an angle of attack of a rotor blade of a wind turbine to a desired value;

3 a block diagram of a device for adjusting an angle of attack, according to an embodiment of the present invention; and

four a block diagram of a control loop for adjusting an angle of attack of a rotor blade of a wind turbine to a target value, according to an embodiment of the present invention.

In the following description of preferred embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and similarly acting, wherein a repeated description of these elements is omitted.

1 shows a partial view of a rotor of a wind turbine, according to an embodiment of the present invention. Shown are three rotor blades 100 , an angle β and three coordinate axes x _{b, i} , y _{b, i} and z _{b, i} . The angle of attack β and the coordinate axes _{xb, i, yb, i} and _{zb, i} are in 1 exemplifying the illustration for the upward-directed rotor blade 100 shown, but it can be seen that each of the rotor blades 100 has its own angle of attack and respective axes. The three coordinate axes are part of a coordinate system that is in 1 at the root of the upwardly directed rotor blade 100 should have its origin.

The rotor blades 100 are part of a wind turbine, apart from the rotor blades 100 only a part of a tower and a nacelle with a hub part are shown. The rotor blades 100 extend radially outwardly from the central hub portion. The hub part and the rotor blades 100 form a rotor with a substantially horizontally extending rotor axis. A rotor blade axis of rotation extends along a main direction of extension of a rotor blade 100 , The angle of attack ß gives the rotational position of a rotor blade 100 around the rotor blade axis again. In the hub part is in each case a radially inner end of a rotor blade 100 rotatably received in a so-called blade bearing about the rotor blade axis of rotation (in 1 not shown). The rotor blade axis of rotation coincides with the coordinate axis z _{b, i} . The rotor axis coincides with the coordinate axis x _{b, i} . The coordinate axis y _{b, i} is orthogonal to the two aforementioned coordinate axes.

A value for the angle β can be specified by a known IPC control. A setting of a rotor blade 100 to a predetermined angle of attack ß is hampered by a setting counteracting Lagerreibmoment.

In the following, a method for determining a compensation _value M _{friction, est} for compensating the bearing friction torque M _{friction will be} described with reference to an exemplary embodiment, which is adjusting the angle of attack β of a rotor blade 100 affected.

To estimate the bearing friction, the rotation of the rotor blade 100 counteracts the z _{b, i} axis, the rotor rotational speed Ω. be known. This is measured at every wind turbine. Further, for each rotor blade 100 the blade rotation position O _Blade (O = 0 rad, blade points up, O = p rad, blade points down) and for each rotor blade 100 the leaf root bending moments M _x , M _y needed as additional sizes. These sizes are usually measured in systems with individual pitch control. The friction estimation described below can thus be implemented on almost every wind power plant using IPC. If one or more variables are not yet detected, suitable measuring devices and evaluation devices can be provided in each case in order to determine the corresponding variables.

The forces F _root in the blade root of a rotor blade can now be determined from the variables mentioned 100 calculate or estimate:

Here, r _{tip is} the blade tip radius, m _{blade is} the rotor blade mass and r _{cm is} the position of the blade center of gravity in the rotor blade 100 , These data are from the design data of the rotor blade 100 known. In the x-direction is closed from the force acting on the blade root bending moment on the thrust. The specified conversion factor applies if a linearly increasing thrust force along the rotor blade 100 is assumed. If the distribution of the thrust along the rotor blade is known in more detail, for example from simulations of the aerodynamics of the rotor blade, then a more precise value for this conversion factor can be determined. The force in the y-direction only considers the weight. The effect of weight is dependent on the blade rotational position. In the z direction, the influence of the weight and the centrifugal force is used to estimate the load. The effect of weight is dependent on the blade rotational position. The centrifugal force depends on the rotor speed.

From this, the tilting moment as well as the forces acting radially and axially on the blade bearing can be calculated:

The tilting moment M _tilt is dependent on the blade root bending moments M _x , M _y .

The radially acting force F _Radial is dependent on the forces acting on the blade root in the x and y directions. The axially acting force F _Axial depends on the force acting on the blade root in the z-direction.

Many bearing manufacturers have published formulas how the maximum friction torque in the bearing can be calculated from the forces acting on and moments on the blade bearing. For example, the Hösch-Rothe-Erde formula commonly used in the wind industry to model bearing friction is used below: M _R = M _R0 + μ _tilt M _tilt + μ _axial F _axial D _R + μ _radial F _radial D _R (3)

MR describes the (maximum) frictional force. M _R0 is the self-friction moment, M _Tilting the tilting moment acting on the bearing, F _Axial the force acting axially on the bearing (eg centrifugal force) and F _Radial the radially acting force. DR is the diameter of the bearing used. The associated coefficients of friction are μ _tilt , μ _axial and μ _radial . These, as well as the Eigenreibmoment M _R0 , are published by the bearing manufacturers.

Now the maximum frictional torque acting in the blade bearing is known. The friction torque in the bearing is always the current direction of rotation of the rotor blade 100 opposed. Is the rotor blade 100 , so the Lagerreibmoment counteracts the external externally acting moment M _ext . So it's calculated too

M _ext is the sum of externally applied moments at the blade bearing. These are the drive torque of the pitch drive and the aerodynamic torque acting from the rotor blade. The aerodynamic moment is unknown. Usually, however, it is more than an order of magnitude smaller than the moment applied by the pitch drive. It can therefore be neglected and M _ext can be set approximately equal to the moment M _K determined by the position controller. The sign of M _K indicates the direction of rotation desired by the controller. It is therefore clear that the frictional torque in the bearing will counteract this exactly.

2 shows a basic structure of a Achsregelungseinheit for the position control of a rotor blade. A controller K calculates a necessary torque M _K from a measured deviation of the angle of attack .beta. From a desired angle of attack .beta. * In order, for example, by means of a motor for the rotor blade turn, that a control error is smaller. In this case, a Lagerreibmoment M _friction acts as a disturbance, which is not known to the controller.

3 shows a block diagram of an apparatus for adjusting a pitch of a rotor blade of a wind turbine to a target value, according to an embodiment of the present invention. The device comprises a device 300 for determining a compensated manipulated variable 310 for adjusting the angle of attack to the setpoint. The device 300 performs the determination based on a manipulated variable M _K provided by a controller for setting the angle of attack of the rotor blade to the desired value and a compensation value M _{friction, est} for compensating a Lagerreibmoments influencing the setting to the compensated manipulated variable 310 to adjust the angle of attack to the setpoint. The controller-based manipulated variable M _K can be determined using a known regulator for adjusting the angle of attack. The compensation value can be determined based on known properties of the rotor blade and forces acting on the rotor blade as a function of the situation.

four shows a block diagram of a control loop for adjusting an angle of attack of a rotor blade of a wind turbine to a target value, according to an embodiment of the present invention. In the in four shown elements and devices may be performed steps of a method according to embodiments of the present invention.

A measured current angle of attack β is fed to a first linking device. The first linking device is also supplied with a desired value β * of the setting angle. The first linking device is designed to perform a subtraction of the angle of attack β from the desired value β *. The result of this combination represents the control error in the control loop and is fed to a controller K. Controller K determines a controller-based manipulated variable M _K from the control error. The controller-based manipulated variable M _K defines a torque which is to be applied to the rotor blade in order to adjust the angle of attack β to the desired value β *. However, the manipulated variable M _K counteracts a disturbance variable in the form of a friction torque M _friction in the blade bearing. The disturbance M _friction prevents a correct adjustment of the angle of attack ß for the case that the angle of attack is set based on the controller-based manipulated variable M _K. To compensate for the disturbance variable M _friction, the controller based control variable M _K is _corrected by using a compensation value M _{est friction.}

In order to determine the compensation value M _{friction, est} , the measured angle of attack β is further fed to an observer L. The observer L determines the current rotational speed β from the position signal β. of the rotor blade. Instead of the observer L, another suitable possibility for determining the rotational speed β. be provided. It may also be sufficient to merely determine whether there is a rotation and if there is a rotation in which direction this occurs.

A device HRE for calculating the maximum bearing friction torque is designed to provide information about the rotor blade rotational position O, the rotor rotational speed Ω. and receive the leaf root bending moments M _x , M _y as input quantities. The device HRE is designed to calculate the maximum bearing friction torque that can act in the blade bearing. The calculation of the maximum bearing friction torque can be based on equations (1), (2) and (3).

A device MR receives the current rotational speed β. of the rotor blade from the observer L, the maximum Lagerreibmoment of the device HRE and the controller-based control variable M _K from the controller K as input signals. In the block MR, an estimated bearing friction torque, that is to say the interference variable M _Reib which is likely to be effective, is calculated as the compensation value M _{Reib, est} for compensating the disturbance M _Reib from these input signals. The calculation can be carried out according to equation (4).

In a second linking device, an addition of the compensation value M _{friction, est} from the block MR to the control-based manipulated variable M _K by the controller K takes place. Thus, a compensated control variable M _K + M _{friction, est is} formed in the second linkage, which corresponds to a sum of the control variable calculated by the controller M _K and the compensation value M _{friction, est} . The compensated manipulated variable can be generated by a motor and cause the angle of attack ß despite the disturbance M _friction can be adjusted to the setpoint ß *. The effect of the compensated manipulated variable and the disturbance M _friction on the rotor blade is indicated by a transfer function G. Thus, the disturbance M _friction by the compensation _value M _{friction, est is} completely or at least approximately compensated.

In summary, the observer L calculates the current rotational speed β from the measured position signal β. For this purpose, a known observer approach, such as Luenberg or Kalman filters, can be used. Block HRE calculates the maximum bearing friction torque according to formulas (1), (2) and (3). This maximum bearing friction torque is provided to the block MR, which calculates the estimated bearing friction torque, the compensation value M _{friction, est} according to formula (4). This calculated or estimated Lagerreibmoment is now added to the predetermined by the controller K torque, the controller-based manipulated variable M _K , with. Thus the physically acting in the bearing friction can be compensated M _friction.

Of course, the estimated bearing friction torque will not be exactly accurate. Nevertheless, the scheme is significantly improved by the proposed compensation, even with an existing estimation error, since no longer the full physical Lagerreibmoment M _friction acts as a disturbance on the controlled system, but minus the compensation value M _{friction, est} , so only M _Reib - M _{Friction, est} . In simulations it was shown that the control error can be improved from approx. 0.5 ° to below 0.10 °. The average power in the pitch drive does not change as a result, power peaks can be significantly reduced. Such a control according to embodiments of the present invention may be used as a supplement to existing plant regulations.

The embodiments described and shown in the figures are chosen only by way of example. Different embodiments may be combined together or in relation to individual features. Also, an embodiment can be supplemented by features of another embodiment. Furthermore, method steps according to the invention can be repeated as well as carried out in a sequence other than that described.

LIST OF REFERENCE NUMBERS

100

rotor blade

ß

Actual pitch

ß *

Target angle

K

regulator

M _K

controller-based manipulated variable

M _friction

(actual) bearing friction torque

G

transfer function

300

Device for determining a compensated manipulated variable

310

compensated manipulated variable

M _{friction, est}

compensation value

L

observer

β.

Rotor blade speed (pitch speed)

M _R

Device for calculating the bearing friction torque

O

Rotor blade rotation position

Ω.

Rotor speed

M _x , M _y

Blade root bending moments

HRE

Device for calculating the maximum bearing friction torque

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7160083 B2 [0003]

Claims (10)

Method for adjusting an angle of incidence (β) of a rotor blade ( 100 ) of a wind turbine to a setpoint value (β *), the method comprising the following step: determining a compensated control variable ( 310 ) for adjusting the angle of attack (β) to the desired value (β *) based on a controller-based manipulated variable (M _K ), which is a variable provided by a controller for setting the angle of incidence (β) of the rotor blade ( 100 ) to the desired value (β *), and a compensation value (M _{friction, est} ) for compensating a bearing _{friction torque} influencing the setting (M _friction ). Method according to claim 1, comprising a step of determining the controller-based manipulated variable (M _K ) based on a deviation of the setting angle (β) from the desired value (β *). Method according to one of the preceding claims, _wherein the compensation value (M _{friction, est} ) based on at least one physical property of the rotor blade ( 100 ) and at least one on the rotor blade ( 100 ) acting force is determined. Method according to one of the preceding claims, _wherein the compensation value (M _{friction, est} ) from a maximum in a rotor blade bearing of the rotor blade ( 100 ) acting friction torque is based on at least one rotor blade characteristic, a rotor blade rotational position (O), a rotor rotational speed (Ω) and at least one blade root bending moment (M _x , M _y ) based. Method according to Claim 4, in which the compensation value (M _{friction, est} ) is further determined at a current pitch velocity (β.) Of the rotor blade ( 100 ). Method according to Claim 5, in which an amount of the compensation value (M _{friction, est} ) is determined by the maximum friction torque acting in the rotor blade bearing and a sign of the compensation value (M _{friction, est} ) by the current pitch velocity (β.) Of the rotor blade ( 100 ) are determined when the actual pitch velocity (β.) of the rotor blade ( 100 ) is not equal to zero, and in which the magnitude of the compensation value (M _{friction, est} ) is given by the smaller value of the maximum friction moment acting in the rotor blade bearing and an externally acting moment and a sign of the compensation value (M _{friction, est} ) by that of externally acting moment are determined when the actual pitch velocity (β.) of the rotor blade ( 100 ) is equal to zero. Method according to one of the preceding claims, with a step of changing the angle of attack (β) of the at least one rotor blade ( 100 ) based on the compensated manipulated variable ( 310 ) to set the angle of attack (ß) to the setpoint (ß *). Method for determining a compensation value (M _{friction, est} ) for compensating a bearing friction torque (M _friction ), which _involves setting an angle of attack (β) of a rotor blade ( 100 ) of a wind turbine, the method comprising the following steps: determining a maximum in a rotor blade bearing of the rotor blade ( 100 ) acting friction torque based on at least one rotor blade characteristic, a rotor blade rotational position (O), a rotor rotational speed (Ω) and / or at least one blade root bending moment (M _x , M _y ); and combining the maximum friction moment acting in the rotor blade bearing with a current pitch velocity (β) of the rotor blade ( 100 ) to determine the compensation value (M _{friction, est} ), wherein an amount of the compensation value (M _{friction, est} ) by the maximum friction torque acting in the rotor blade bearing and a sign of the compensation value (M _{friction, est} ) by the actual pitch velocity (β .) Of the rotor blade ( 100 ) are determined when the actual pitch velocity (β.) of the rotor blade is nonzero, and where the magnitude of the compensation value (M _{friction, est} ) is the smaller of the maximum friction moment acting in the rotor blade bearing and the externally acting moment and a sign of the compensation value (M _{friction, est} ) is determined by the externally acting moment when the actual pitch velocity (β.) of the rotor blade ( 100 ) is equal to zero. Device for adjusting an angle of attack (β) of a rotor blade ( 100 ) of a wind turbine to a desired value (β *), the device comprising: a device ( 300 ) for determining a compensated manipulated variable ( 310 ) for adjusting the angle of attack (β) to the desired value (β *) based on a controller-based manipulated variable (M _K ), which is a variable provided by a controller for setting the angle of incidence (β) of the rotor blade ( 100 ) to the setpoint (ß *) represents, and a compensation value (M _{friction, est} ) for compensating a Lagerreibmoments influencing the setting (M _friction ). Computer program product with program code for carrying out the method according to one of claims 1 to 8, when the program is executed on a device.

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