WO2012007111A2

WO2012007111A2 - Method and device for making an angle of attack correction signal available for a predetermined rotor blade of a wind turbine

Info

Publication number: WO2012007111A2
Application number: PCT/EP2011/003270
Authority: WO
Inventors: Felix Hess; Martin Voss; Boris Buchtala; Christian Eitner
Original assignee: Robert Bosch Gmbh
Priority date: 2010-07-15
Filing date: 2011-07-01
Publication date: 2012-01-19
Also published as: WO2012007111A3; DE102010027229A1

Abstract

The invention relates to a method (900) for making an angle of attack correction signal (139) available for a predetermined rotor blade (210) of a plurality of rotor blades of a wind turbine (110). The angle of attack correction signal for modifying a signal (145) is provided for controlling an individual angle of attack of the rotor blade. The method (900) comprises the following steps: reading in (910) a rotor blade position signal (120) which represents an angular position (Ω₁) of the rotor blade relative to a rotational axis (310) of the rotor of the wind turbine and/or reading in a rotational speed (ω) of the rotor blade about the rotational axis (301). The method (900) further comprises a step of determining (920) the angle of attack correction signal (139) for the predetermined rotor blade of the wind turbine using a correlation between an angular position and an angle of attack correction factor saved in a memory (137), the angle of attack correction signal representing the angle of attack correction factor which, when used, prompts correction of the signal (145) for controlling the individual angle of attack for the predetermined rotor blade so that an impact of a torque (M₁) onto the predetermined rotor blade is matched with an impact of a torque (M₂, M₃) onto the at least one further rotor blade of the wind turbine, the determination being carried out using the read-in rotor blade position signal and/or the read-in rotational speed.

Description

I

The present invention relates to a method and apparatus for providing a pitch correction signal for a predetermined rotor blade of a plurality of rotor blades of a wind turbine according to the independent claims. In wind turbines with horizontal axis and at least two rotor blades is synchronously adjusted the blade angle, the speed above the rated wind speed regulated so that by changing the angle of attack (also referred to as pitch angle) the aerodynamic lift and thus the drive torque is changed in such a way that a Reduction of the responsible for the drive torque buoyancy force can be achieved and thus the system can be maintained in the range of rated speed. At wind speeds above the shutdown speed, this blade pitch mechanism is also used as a brake by putting the blades nose-to-wind so that the rotor no longer delivers any significant drive torque. The rotor blades can then be used as aerodynamic brakes by being placed completely in the direction of wind flow (flag position) or by increasing the angle of attack so much that the flow leaves (stable). Collective pitch control (CPC) results in pitching and yawing moments on the nacelle due to asymmetric aerodynamic loads. The asymmetric loads are caused, for example, by wind shear in the vertical direction (boundary layers), yaw angle errors, gusts and turbulence, impoundment of the flow at the tower, etc. Lately, a new approach for the regulation of three-wing wind turbines is increasingly being investigated. rather, in addition to the collective pitch angle, calculate an individual pitch angle of the individual rotor blades. The individual pitch control (IPC) allows a reduction in the asymmetrical loads transmitted to the hub via the nacelle. For this purpose, the bending moments acting on the individual rotor blade roots are measured, and the individual blade adjustment necessary for the reduction of the yawing and pitching moments is calculated. The pitch angles calculated from the IPC and CPC control are then sent as default to the controllers of the corresponding pitch actuators. The bending moments thus serve as a control variable 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. Such an approach is disclosed for example in the document DE 197 39 164 B4.

The regulation of the rotor blade pitch is, however, too slow in some situations, so that the optimum angle of attack is not found. It is an object of the present invention to provide an improvement for the control of the angle of attack.

This object is solved by the subject matter of the independent patent claims. Advantageous embodiments emerge from the respective subclaims and the following description.

The present invention provides a method of providing a pitch correction signal for a predetermined rotor blade from a plurality of rotor blades of a wind turbine, wherein the pitch correction signal is suitable for varying a signal for driving an individual pitch for the rotor blade, the method comprising the following steps having:

- Reading a rotor blade position signal representing an angular position of the rotor blade with respect to a rotational axis of a rotor of the wind turbine and / or reading a rotational speed of the rotor blade about the axis of rotation; and

Determining the pitch correction signal for the predetermined rotor blade of the wind turbine using a stored in a memory relationship between the angular position and a Anstellwinkel- correction factor, wherein the pitch correction signal represents the pitch correction factor, which in use a correction of the individual angle of attack for the causes predetermined rotor blade, so that an effect of a moment on the predetermined rotor blade of an effect of a torque is adjusted to at least one further rotor blade of the wind turbine and wherein the determining is carried out using the read rotor blade position signal and / or the read rotational speed.

Furthermore, the present invention provides a device for providing a pitch correction signal for a predetermined rotor blade of a plurality of rotor blades of a wind turbine, wherein the pitch correction signal for changing a signal for driving an individual pitch for the rotor blade is provided, the device comprising the following Features include:

an interface for reading in a rotor blade position signal representing an angular position of the rotor blade with respect to an axis of rotation of the rotor of the wind turbine and / or reading a rotational speed of the rotor blade about the axis of rotation; and

a unit for determining the pitch correction signal for the predetermined rotor blade of the wind turbine from a memory, wherein the pitch angle correction signal represents a pitch correction factor, which in use causes a correction of the individual pitch for the predetermined rotor blade, so that a Effect of a moment on the predetermined rotor blade of an effect of a moment is adjusted to at least one further rotor blade of the wind turbine and wherein the determining is carried out using the read-in rotor blade position signal and / or the read rotational speed. Also of advantage is a computer program product with program code, which is stored on a machine-readable carrier such as a semiconductor memory, a hard disk memory or an optical memory and which is used to carry out the method according to one of the embodiments described above, when the program on a control device or a device is performed.

The present invention is based on the recognition that a much faster and better control of the pitch angle of a rotor blade can be achieved when a correction signal is provided which reads out a correction factor for the pitch angle of a specific rotor blade in dependence on an angular position of this rotor blade from a memory. In this context, the angle of attack is defined as the angle by which the rotor blade on the rotor hub is rotated about the rotor blade axis with respect to a zero position in the rotor plane, wherein in the zero position the rotor blade has a maximum thrust force from wind in the direction of the rotor axis having. If the above-mentioned relationship is used, largely stationary forces on the rotor which, for example, due to an oblique flow of the rotor, windfall effects on the tower of the wind turbine or forces due to a wind shear as a function of the angular position of the rotor blade for the rotor blade individually corrected sheet so that the individual pitch control for the individual rotor blades can only be limited to compensating for the effects of wind turbulence. This considerably relieves the regulation of the individual angles of attack. The stationary forces are taken into account for the determination of the angle of attack correction signal as a function of the angular position of the rotor blade, for example, the effects of wind shear or the wind accumulation effects on the tower of the wind turbine in different angular positions of the rotor blade have different weight.

The present invention offers the advantage that the separation of stationary effects and dynamic effects caused by turbulence in the load behavior of the rotor blades makes it possible to control the optimum angle of attack much more quickly and at the same time more precisely. In this case, the regulation does not need to be carried out directly by the present invention, but rather the essential Core of the invention in the provision of a corresponding correction signal, the use of which is possible on the already known regulation of the individual angle of attack. The present invention offers the additional advantage that an existing control concept can be reused and improved by the use of the present invention. This also allows retrofitting to existing wind turbines, which represents an additional economic advantage for the use of the present invention.

It is favorable if, in the step of determining, there is a change in the relationship stored in the memory. Such an embodiment of the present invention offers the advantage that a rapid and flexible updating of the relationship stored in the memory to the corresponding local wind conditions. can be carried out. According to another embodiment of the present invention, a determination of a wind speed at different segments of a rotor blade can be carried out in the step of determining the change in the memory stored in the memory, wherein the determination of the wind speed at the individual segments of the rotor blade taking into account a determined current inclination of the rotor axis against the horizontal, a current distance of a rotor hub to a tower of the wind turbine, a determined oblique flow angle of wind with respect to the rotor axis in the region of the relevant segment, a current wind speed in the direction of the rotor axis in the region of the relevant segment of the rotor blade as a function of the height of the relevant segment over the earth's surface and / or a diameter of a tower of the wind turbine take place at a height of the relevant segment of the rotor blade. Such an embodiment of the present invention offers the advantage that the relationship stored in the memory very precisely maps a correction factor that can be used to compensate for largely stationary disturbances. In this way, the regulation of the individual angle of attack can be relieved and thus accelerated. It is particularly advantageous if in the step of determining a segmentation of a flight circle of the rotor blade about the rotor axis into different segments, wherein at least information about a load of the predetermined rotor blade in one of the segments of the flight circle is recorded and the recorded information for determination a pitch correction signal of another rotor blade of the wind turbine is used, in particular wherein the recorded information is used to determine a Anstellwinkel-correction signal of a rotor blade of the wind turbine, which immediately follows the predetermined rotor blade in the direction of rotation of the rotor. Such an embodiment of the present invention offers the further advantage that the relationship stored in the memory can be adapted very flexibly and quickly to smaller local changes of the largely stationary disturbances. In this way, for example, a rotor blade directly following the rotor blade can already make use of the loading information which was detected by sensors from the first, that is, from the predetermined rotor blade.

In a particular embodiment of the present invention, information about a load of the rotor blade following the predetermined rotor blade can be recorded in the step of determining at least one segment, wherein furthermore a deviation between the load of the predetermined rotor blade and the load of the further rotor blade, in particular of the predetermined rotor blade immediately following rotor blade is determined and wherein the determined deviation is used for a determination of the load and / or a Anstellwinkel- correction signal for a third rotor blade of the wind turbine, when the third rotor blade is in the segment of the flight circle. Such an embodiment of the present invention offers the advantage that, when the substantially stationary disturbance variable changes, an estimate of this change for a subsequent rotor blade can already be made. Thus, the pitch correction signal provided may be based on a prediction for varying (essentially stationary) disturbances, which is reflected by a further improvement in the speed and precision of the pitch control when using said pitch correction signal , Also, according to a further embodiment of the present invention, in the step of determining information about a load of the further rotor blade, in particular the rotor blade immediately following the predetermined rotor blade, in the relevant segment are detected and also in the memory, the information about the load of the rotor blade be replaced by the detected information about the load of the other rotor blade. Such an embodiment of the present invention offers the advantage that the relationship stored in the memory is updated in very short time intervals, so that the provision of the pitch correction signal is based on the most precise possible current basis of measured values. This ensures fast and highly accurate control of the individual angle of attack for a single rotor blade when the aforementioned pitch correction signal is used to vary the individual angle of attack of that rotor blade.

According to a further embodiment of the invention, the method may further comprise the following steps:

- Reading a further rotor blade position signal representing an angular position of at least one other rotor blade with respect to a rotational axis of the rotor; and

Determining a further pitch correction signal for the other rotor blade of the wind turbine using the stored relationship between an angular position and a pitch correction factor, the further pitch correction signal representing a pitch angle correction factor which, in use, corrects an individual pitch Angle of incidence for the other Rötorblatt causes, so that an effect of a moment on the other rotor blade of an effect of a moment on the predetermined rotor blade of the wind turbine is adjusted and wherein the determination is carried out using the read in another rotor blade position signal and / or the read rotational speed. Such an embodiment of the present invention offers the advantage that not only an optimization of the pitch angle of a single rotor blade takes place, but that the optimization is carried out jointly for a plurality of rotor blades. This represents a further improvement in the regulation of the angles of incidence of the rotor blades of the wind power plant. In particular, this results in a reduction in the yawing and pitching moments on the tower or the nacelle of the wind power plant.

In a further embodiment of the invention, a method for modifying a signal for actuating an individual angle of attack for the rotor blade can also be provided, this method having the following steps:

the steps of the method as described above; and

- Modifying the signal for controlling the individual pitch for the rotor blade using the provided Ansteuerwinkel- correction signal.

Such an embodiment of the present invention offers the advantage of not only providing an angle of attack correction signal, but of actually changing the signal for driving the individual angle of attack. This allows implementation of the advantages that are provided by providing the Anstellwinkel- correction signal.

The invention will now be described by way of example with reference to the accompanying drawings. 1 shows a block diagram of a control circuit for adjusting the individual angles of incidence for rotor blades of the rotor of the wind power plant, an embodiment of the present invention being used;

FIG. 2 is a front view of a wind turbine, showing a representation of a segmentation of the rotor blades for determining the current pitch correction factor; FIG. 3 shows a representation of a wind shear at different heights above the earth's surface and a side view of a wind power plant in which the rotor axis is shown tilted;

4 is a plan view of a wind turbine, wherein the rotor blades are flowed diagonally by wind;

5 is an illustration for explaining the Turmstaueffekts.

6 shows representations for clarifying the effect of measured load values on subsequent rotor blades of the wind power plant;

7a shows a diagram of load values in a circle segment of a rotor blade in chronological order with an increase of wind;

7b is a diagram showing a change of a correction factor for the angle of attack for the increase of the wind load within the circle segment of the rotor blade shown in FIG. 7a at different points in time;

8 is a block diagram of a control circuit for adjusting the individual control angle for rotor blades of the rotor of the wind turbine, wherein another

Embodiment of the present invention is used; and

9 is a flowchart of an embodiment of the present invention as a method. The same or similar elements may be provided in the following figures by the same or similar reference numerals. Furthermore, the figures of the drawings, the description and the claims contain numerous features in combination. It is clear to a person skilled in the art that these features are also considered individually or that they can be combined to form further combinations which are not explicitly described here. Furthermore, the invention in the following description may be explained using different dimensions and dimensions, wherein the invention is not limited to these dimensions and dimensions to understand. Furthermore, method steps according to the invention can be repeated as well as carried out in a sequence other than that described. If an exemplary embodiment comprises a "and / or" link between a first feature / step and a second feature / step, then this can be read such that the exemplary embodiment according to one embodiment includes both the first feature / only step and the second feature / the second step and according to another embodiment, either only the first feature / the first step or only the second feature / the second step.

An important aim of the present invention is to be seen in that a disturbance variable connection for the IPC control should be realized or made possible. As a result, a significantly improved performance of the IPC control can be achieved. The invention can be very easily combined with the known IPC control methods so that already existing and implemented IPC control strategies can be supplemented. For this purpose, for the individual Pitchregelurig a rotor blade stored over up to a complete rotor circulation measurement information in the best case of all rotor blades are used. The strain gauges obtained from the measurement information can then be used to estimate the expected rotor loads. Based on this estimate, a desired trajectory of the individual pitch angles can then be calculated and used for the precontrol of the pitch actuators.

An important aspect of the present invention is the fact that the IPC control can be extended by a noise compensation, which te the yawing and Nickmomen to compensate for the wind turbine, resulting from known interference effects. These disruptive effects include, for example:

1) the inclination of the rotor axis against the horizontal (usually about 5 °). This creates moments due to the weight force acting on the blades, as well as a periodically changing flow, as the blade tips move back and forth during one revolution.

2) errors in the flow through the tower shadow;

3) dependence of the wind speed on the height above the ground

wind shear;

4) oblique flow of the rotor blades; and

5) Other effects (eg shadowing of half of the rotor surface by other equipment, etc.). 3270

1 1

Since all of these effects change only slowly over time, they can be eliminated by means of noise compensation before they can be measured at the output. For this purpose, first the course of a correction variable for the individual pitch angle for each rotor blade is determined, which is necessary to eliminate the interference. This course is then added as a noise compensation additive in addition to the individual pitch angle calculated by the IPC controller and supplies the received signal to a pitch actuator. A basic procedure in the determination of the corrected individual angle of attack can be seen from the block diagram of FIG. 1. The block diagram of FIG. 1 shows how a control loop 100 that uses the present invention could be configured. Here, the angle of attack of not shown in FIG. 1 rotor blades of a wind turbine 1 10 is regulated. This regulation takes place as a function of the speed of the wind 1 15, which acts on the rotor blades of the wind turbine 1 10. At the wind turbine 1 10 different sensors 120 are detected by sensors, such as the speed of the

Rotor, the angular velocity of the rotor, one or more angular positions of the rotor blades or bending moments, which occur at the blade roots of the rotor blades. These measured variables 120 such as (the angular positions of the rotor blades 1, 3 or 3), ω, Μι ^ (the moments of the rotor blades 1, 2 and 3) are the unit 125 for operation of the wind turbine 1 10, an IPC Regulator 130 and a device 135 and via an interface 136 to a memory 137 which is a unit which provides the Anstellwinkel correction signal 139 also as ßu.2, 3 for the disturbance variable signal for the first, second and third rotor blade provides. In particular, a pitch correction signal for each of the rotor blades of the wind turbine 110 can be provided by the memory 137. In the memory 137, a relationship between the Ansteiiwinkel correction signal for at least one of the rotor blades of the rotor of the wind turbine 1 10 is stored in response to a current angular position of the rotor blade and / or an angular velocity of the rotor for the correction of the individual angle of attack 139 of concerned rotor blade is issued. In the device 135, corrections of the relationship stored in the memory 137 can be carried out in accordance with the description described in greater detail below, and these corrections can be stored in the memory 137. As a result, the relationship stored in the memory 1 37 can be kept current, so that a very precise control of the angle of attack becomes possible.

The operating control unit 125 supplies general control signals related to the optimization of the output of the wind turbine 110 on the basis of the rotational speed ω. For example, the operating control unit 125 supplies a current generator torque 140, which is made available directly to the wind power plant 110, in order to achieve a regulation of the rotational speed of the generator and thus an optimization of the power output of the generator of the wind power plant. Furthermore, the operating control unit 125 supplies a signal 142, which represents a common angle of attack for all rotor blades of the rotor of the wind turbine 1 10, thus taking into account the current wind speed 15 (and possibly the current wind direction), the wind turbine 1 10 in their current optimal performance point works.

The IPC controller 130 uses, for example, one or more signals about moments M 1 ^ 3, which are detected at the individual rotor blade roots and can therefrom for at least one, but better for each of the individual rotor blades an individual angle of attack 145 (from with μipc, 3).

The pitch correction signal 139 for a particular rotor blade, the signal 145 representative of the individual pitch for the particular rotor blade, and the signal 142 representing a common pitch of all blades may then be additively linked to a corrected pitch control signal 150. From this corrected Anstellwinkel _drive signal 150 is a signal below described in more detail ßi i2,3 _subtracted for a current angle of attack for the relevant rotor blade 1, 2 or 3, wherein the signal obtained from the subtraction is fed to a subordinate pitch _controller 155, for example as P-controller with the control factor k _{A is} configured. That of the subordinate Angle controller 1 55 received signal is additively linked to a signal from a pre-control unit 160 for the pitch actuator. The signal thus linked is subsequently fed to a pitch angle actuator 165 with the transformation instruction G _A , which sets the actual angle of attack for the relevant rotor blade. A signal representing this actual angle of attack for the relevant rotor blade is subtracted from the signal 150 as the above-current angle of attack. The pre-control unit 160 for the pitch-angle actuator thereby performs a prediction of the expected pitch on the basis of the Anstellwinkel- correction signal 139, so that a faster control of the corrected individual-angle of attack for the relevant rotor blade is possible. The above description can also be made for each individual rotor blade of the rotor of the wind turbine 1 10, so that an optimization of the regulation of the individual angle of attack for the rotor blades is possible. However, it is not necessary that the pitch be optimized for all rotor blades.

Since the course of the size for the noise compensation is known in advance, a control can be realized for the pitch controller 155 stored in pitch, which allows a significantly improved and faster follow-up control of the pitch actuator 165. As a result, the actuator can set the pitch components resulting from the interference compensation with the aid of the pitch correction signal 139 virtually without delay. With correctly calculated pitch curve for the noise compensation, the asymmetrical loads can be completely compensated for at a constant, turbulence-free wind. The noise compensation uses a curve in the memory 137, which contains a correlation for the necessary pitch or pitch angle for the noise compensation for each sheet. This curve can be calculated by the device 135 by calculating in the device 135 the course of the wind speed at individual leaf elements. Subsequently, the curve for the

Pitch angle optimized so that the resulting flow conditions result in no or very low asymmetric moments.

However, the curve for the pitch angle can also be adapted continuously in an improved embodiment of the invention by determining from the measured data 120 the wind speed. power plant continuously the parameters of the wind shear, the Turmvorstaus, etc. read and adjusted using these parameters of the stored in the memory 1 37 context. In this case, the individual disturbing effects should not be resolved separately, but an algorithm can be implemented, which adjusts the pitch curve over the rotor blade position so that all disturbing effects, which do not originate from the turbulence of the wind, are compensated.

For the calculation of the wind speeds on the individual rotor blades, for example, a consideration of individual segments 200 of the one or more rotor blades 210 of the wind turbine 1 10 can be used, as shown in FIG. In this case, a distance r of the respective segment 200 from the hub of the rotor as well as the rotational speed ω and / or the angular position Ω of the rotor blade 210 is taken into account, at which the relevant segment is currently located. In this case, a coordinate system is considered in which the z and y axes according to the illustration in FIG. 2 run.

Furthermore, the wind shear at different heights H above the earth's surface can be taken into account for the calculation of the wind speeds. For this purpose, for example, a pitch angle 5 of the rotor axis 310 with respect to the horizontal and a distance of the rotor hub 320 with respect to the center of the tower of the wind turbine is taken into account, as shown schematically in FIG. FIG. 3 also shows the course of the x-coordinate for a coordinate system, as used in the calculation of wind speeds. In determining the wind shear different wind speeds are to be considered, which can occur according to the left schematic representation of Fig. 3 at different heights above the earth's surface, being observed at a great height above the earth's surface, a greater wind speed than close to the earth's surface ,

Also, for example, when determining the wind speeds, the oblique inflow of the rotor blades 210 under the angle of incidence γ with respect to the rotor axis is taken into account, as can be seen schematically from FIG. 4. In addition, an air congestion on the tower of the wind turbine can also be taken into account in the calculation of the wind speeds, as illustrated in the illustration of FIG. 5. 5 shows through the solid lines a flow behavior of wind around a stationary tower of a wind power plant, simplified by a tower radius r at the height of the considered segment 200 at an angle φ and a distance r of this segment 200 from the Center of the tower is assumed. The flow velocity of the wind is designated by the variable u. Using the above relationships can now be the. Estimate wind speeds in different coordinate directions with the help of the following formulas: z = r · cos Ω · cos δ;

y = - r · sin il;

x = - h + r · sin δ · cos Ω;

Furthermore, the following relationship is used for wind speeds in the x and y directions:

* = · FtKr)! ^' t ^{1 + ■} ^ ^{~ cos2} ^ ^(,)

where φ = arctan ^. Also, the value of the shear coefficient α can be used as an exponent instead of 1/7. This can change over time

Here, in the equations (1) and (2), the term represents

_VHH . (£ ^ V. ( _{1 +} - ^)

H ^M. \ zwub \ x ² + y ² / the component of the wind caused by the wind shear and the term

{ ^l + · ( ^{sir, 2 (} p ^{- cos2} <P) ^b z ^w - (- ² + · ^sin φ · ^cos φ) is the component which can be calculated by the tower congestion model via the potential flow approach Potential damper model uses the following two equations:

Ur = u · (l - 2 _j ) · cos φ

and

u _v = -u * (1 - 2 _j ) · sin φ.

The entire rotor incident flow, ie the flow velocity of the rotor of wind can be simplified by neglecting the small proportion of v _y folgenderma- SEN be determined: v = v _x cos γ + r · sin δ · ω · sin Ω. (3)

In this case, the term cos γ maps the oblique flow of the rotor, while the term r · sin 6 · ω · sin Ω represents the velocity on the basis of the axial inclination.

Using the above formulas, the pitch angle correction relationship stored in the memory 137 may be changed with respect to the current angular position of the rotor and / or the rotational speed of the rotor. This can be done by the unit 135, in which a corresponding model is stored, which angle of attack for a single rotor blade at which wind speed from which direction is required in order to achieve an optimal symmetrical as possible reduction of the load of the wind turbine. It should be noted that the above quantities reflect the stationary conditions that are not fast, ie that can change in the range of a few tens of seconds. For the favorable angle of attack obtained, a corresponding correction factor can then be determined. which is added to an individual angle of attack signal determined by the IPC controller 130 based on the very brief (ie, in the range of seconds) air turbulence. An important object of the invention according to a further embodiment of the invention is to realize an active precontrol of the pitch actuators based on the load measurement series measured in the cycle of rotation of the rotor. The load curve of a rotor blade is here considered as the expected load curve of the Nachläufers (ie the directly following rotor blade) of a circle segment of the rotor blades, wherein the flight circle denotes the surface which sweep the rotor blades during rotation about the rotor hub. For illustration, the following diagrams are shown in FIG. 6. The measured impact bending loads of the rotor blades (lower diagrams) with respect to the measured wind speeds (upper diagrams) are shown in the two left and two right diagrams. The passage order of a rotor sector (ie, the considered segment of the rotor blade circle) is 3-2-1, that is, with respect to the rotor blade 2, sheet 3 is the precursor and sheet 1 is the follower. If the load curves shown are each shifted by t = T / 3 (with T the rotor cycle time) to the right in the time rail, the load curves in the lower diagrams of FIG. 6 can be almost brought into line, ie the solid line corresponds essentially the dashed line and the dashed line can then also represent the dotted line shown; apart from changes in the load moments, which tend to be the same for all three rotor blades.

The load curves within a main sector are thus assigned to the respective subsequent rotor blade. In order to avoid too much uncertainty about the prediction, only the load curve of the precursor for the prediction of the load of the trailer is considered. The rotor surface is discretized for this purpose (eg with a rotor azimuth angle of 1 degree per segment). During the rotor revolution, the measured loads are the corresponding rotor azimuth angles when sweeping the Diskretisierungsabschnittes or the Assigned discretization step. In this way, when storing a complete rotor revolution three (or four) measured values per rotor azimuth angle segment and circulation can be realized. The basic idea for the pilot control according to this exemplary embodiment is to use the sensor data of the individual rotor blades measured during a third revolution (ie 120 degrees) as the basis for the trajectory planning of the pitch angles of subsequent rotor blades. The cyclic load curves of wind turbines that can be detected in measurements and simulations make it possible to predict the expected load,

Thus, the trajectory planning is limited to 3 * 120 ° sectors, for each of which a desired trajectory of the pitch adjustment is calculated. This desired trajectory can be stored for each of the sectors in the memory 137 and used to correct the individual pitch of a rotor blade located in the sector concerned. After sweeping a 120 ° sector, the trajectory planning for this sector will be updated based on the new rotor blade data, which has just passed through this sector. In the lower left diagram of FIG. 6 (load curve gust), an increasing rotor load in the time range 10-22 seconds and a decreasing load in the range 22-30 seconds can be detected. In the case of a gust of wind or, in general, a change in the wind speed (and thus the rotor load), a load gradient for the individual rotor segments can be calculated by means of the measured data.

This change in wind speed, which may also be referred to as a gradient, may then be used as a correction factor for the load curves. The prerequisite for the consideration of the correction factor in this case is a clearly ascertainable tendency on the basis of the measured data series of the corresponding rotor sectors. Such a tendency can be seen, for example, from the diagram of FIG. 7a, in which the wind speed (and thus the moment load M) continuously increases in one and the same rotor segment over the one-third cycle durations T. This can be a correction factor be determined by the load trajectory is changed or should be changed accordingly. For example, this is done in accordance with the representation of FIG. 7B, in which the setpoint trajectory drawn by means of the correction factor, the effect of which is represented by the arrows in FIG. 7B, is converted into a corrected setpoint trajectory, which is represented by dashed lines is. This allows a very short-term change of the correction factors and thus a very fast adaptation of the pitch angle correction signal to be set to the current wind conditions in the respectively considered rotor sector. The procedure described above can then also be carried out for a plurality of rotor sectors, so that as far as possible a short-term update of the wind conditions is possible for the entire flight circle of the rotor. Based on the (corrected) load curves, a feedforward control of the pitch actuators in the context of IPC control can be realized.

Such an embodiment could be reproduced according to a block diagram of FIG. In this case, the memory 137 contains a trajectory planning for the individual rotor sectors, which are updated by the unit 135 in each case. Compared with the exemplary embodiment of the block diagram of FIG. 1, a relationship between an angular position and the pitch correction factor for a rotor blade for a complete revolution is no longer stored in the memory 137, instead the correction factors are stored for individual rotor sectors (or at least one sector) determined and updated after sweeping the trailing rotor blade. In this way, a highly accurate and rapid control or correction of the individual angles of attack of the rotor blades or is achieved.

Further, the present invention provides a method 900 for providing a pitch correction signal for a predetermined rotor blade from a plurality of rotor blades of a wind turbine as illustrated in a flow chart in FIG. Here, the pitch correction signal for changing a signal provided for driving an individual angle of attack for the rotor blade. The method 900 comprises a step of reading in 910 a rotor blade position signal representing an angular position of the rotor blade with respect to an axis of rotation of the rotor blade and / or reading a rotational speed of the rotor blade about the axis of rotation. Further, the method 900 includes a step of determining the pitch correction signal for the predetermined rotor blade of the wind turbine using a relationship between an angular position and a pitch correction factor stored in a memory, the pitch correction signal representing the pitch correction factor included in the memory a use of a correction of the individual angle of attack for the predetermined rotor blade is effected so that an effect of a moment on the predetermined rotor blade of an effect of a torque is adjusted to at least one further rotor blade of the wind turbine and wherein the determining using the read rotor blade position signal and / or the read rotational speed takes place.

The exemplary embodiments shown are chosen only by way of example and can be combined with one another.

25

LIST OF REFERENCE NUMBERS

100 Apparatus for providing a pitch correction signal

1 10 wind turbine

120 sensor signals from sensors on or in the wind turbine

125 Unit for operating the wind turbine

130 controls for determining the individual angles of attack

135 Unit for changing the relationship stored in the memory

136 interface

137 memory

139 Angle Correction Signal

140 Signal representing the generator torque

142 Signa), which represents the common pitch angle for all rotor blades

145 signal for individually controlling the angle of attack from the 1PC controller 150 corrected individual pitch control signal

155 subordinate pitch controller

160 feedforward control for the pitch actuator / pitch actuator

165 pitch actuator, pitch actuator 200 segment of a rotor blade

210 rotor blade

310 rotor axis of rotation

320 rotor hub

900 A method of providing a pitch correction signal

910 step of reading in

920 step of the determination

Claims

21

claims

Method (900) for providing a pitch correction signal (ßi, 139) for a predetermined rotor blade (210) of a plurality of rotor blades of a wind turbine (1 10), wherein the pitch correction signal for changing a signal (1 5) for driving a individual pitch angle for the rotor blade, the method (900) comprising the following steps:

- Reading (910) of a rotor blade position signal (Ωι, 120) representing an angular position (Ωι) of the rotor blade with respect to a rotational axis (310) of the rotor of the wind turbine (1 10) and / or reading a rotational speed (ω) of the rotor blade to the axis of rotation (310); and

- Determining (920) the pitch correction signal (139) for the predetermined rotor blade of the wind turbine using a stored in a memory (137) relationship between an angular position (Ωι) and a Anstellwinkel correction factor (ßi), wherein the Anstellwinkel correction signal the Anstel Iwinkel correction factor representing, in use, a correction of the signal (ßjpci, 1 5) for driving the individual angle of attack for the predetermined rotor blade causes, so that an effect of a moment (Mi) on the predetermined rotor blade of an effect of a moment (M _j M ₃ ) is adapted to at least one further rotor blade of the wind turbine and wherein the determination using the read-in rotor blade position signal (Ωι) and / or the read-in rotational speed (ω) takes place.

2. The method according to claim 1, characterized in that in the step of determining a change in the stored relationship in the memory. 22

Method according to claim 2, characterized in that, in the step of determining the change in the relationship stored in the memory, a determination of a wind speed (15) takes place on different segments (200) of a rotor blade, wherein the determination of the wind speed at the individual segments of the rotor blade taking into account a determined current inclination (δ) of the rotor axis (3 10) against the horizontal, a current distance of a rotor hub (320) to a tower of the wind turbine, a determined oblique angle of incidence (γ) of wind with respect to the rotor axis in the region of the relevant Segmentes, a current wind speed in the direction of the rotor axis in the region of the relevant segment of the rotor blade as a function of the height (H) of the relevant segment above the earth's surface and / or a diameter (a) of a tower of the wind turbine at a height of the respective segment of the rotor blade SUC gt.

Method according to one of the preceding claims, characterized in that in the step of determining a segmentation of a flight circle of the rotor blade about the rotor axis into different segments, wherein at least one information about a load of the predetermined rotor blade in one of the segments of the flight circle is recorded and the recorded Information is used to determine a Anstellwinkel-correction signal of another rotor blade of the wind turbine, in particular wherein the recorded information is used to determine a Anstellwinkel-correction signal of a rotor blade of the wind turbine, which immediately follows the predetermined rotor blade in the direction of rotation of the rotor.

5. The method according to claim 4, characterized in that in the step of

For at least one segment information about a load of the rotor blade immediately following the predetermined rotor blade is recorded, wherein there is also a deviation between the load of the predetermined rotor blade and the load of the further rotor blade, in particular of the rotor blade immediately following the predetermined rotor blade 23 is determined and wherein the determined deviation is used for a determination of the load and / or a Anstellwinkel correction signal for a third rotor blade of the wind turbine, when the third rotor blade is in the one segment of the flight circle.

A method according to claim 4 or 5, characterized in that in the step of determining information about a load of the further rotor blade, in particular the rotor blade immediately following the predetermined rotor blade, in the relevant segment is detected and also in the memory, the information about the load of the rotor blade is replaced by the detected information on the load of the other rotor blade.

Method according to one of the preceding claims, characterized in that the method further comprises the following steps:

- Reading another rotor blade position signal (Ω ₂ ), which represents an angular position of at least one other rotor blade with respect to a rotational axis of the rotor; and

Determining a further pitch correction signal (139, βsa) for the other rotor blade of the wind power station using the relationship between an angular position and a pitch correction factor stored in memory, the further pitch correction signal representing an attack angle correction factor a use of a correction of an individual angle of attack for the other rotor blade causes, so that an effect of a moment on the other rotor blade of an effect of a moment on the predetermined rotor blade of the wind turbine is adjusted and wherein the determining using the read in another rotor blade position signal and / or the read rotational speed takes place.

A method of modifying a signal to drive an individual angle of attack for the rotor blade, the method comprising the steps of: 24 shows the steps of the method according to one of claims 1 to 7; and changing the signal for driving the individual angle of attack (βipci) for the rotor blade using the provided drive angle correction signal (β _l ).

Device (1 00) for providing a pitch correction signal (139, β _s , i) for a predetermined rotor blade of a plurality of rotor blades (210) of a wind turbine (1 10), wherein the pitch correction signal for changing a signal (145). is provided for controlling an individual angle of attack for the rotor blade, the device having the following features:

- An interface (136) for reading a rotor blade position signal (Ω |), which represents an angular position of the rotor blade with respect to a rotation axis (320) of the rotor of the wind turbine and / or reading a rotational speed (co) of the rotor blade about the axis of rotation; and

- A unit (135, 137) for determining the pitch correction signal (ßs, i) for the predetermined rotor blade of the wind turbine from a memory (137), wherein the pitch correction signal represents a Anstellwinkel- correction factor, which in use a correction of the individual angle of attack (βipci) for the predetermined rotor blade is effected, so that an effect of a moment (Mi) on the predetermined rotor blade of an effect of a moment (M ₂ , M ₃ ) is adjusted to at least one further rotor blade of the wind turbine and wherein the determining using of the read-in rotor blade position signal and / or the read rotational speed takes place.

Computer program product with program code for carrying out a method according to one of claims 1 to 8, when the program is executed on a control device or a device.