METHOD FOR PARAMETERIZING A SENSOR ARRANGEMENT COMPRISING MULTIPLE LOAD SENSORS OF A ROTOR BLADE OF A WIND POWER INSTALLATION

Abstract

A method for parameterizing a sensor arrangement comprising multiple load sensors of a rotor blade of a rotor of a wind power installation for acquiring at least one load variable, which is representative of a load that acts on the rotor blade, wherein the rotor blade has at least three load sensors, each of the load sensors records a load-dependent physical variable of the rotor blade and outputs a variable representative thereof as the acquired sensor variable, for calculating the at least one load variable from the sensor variables, at least one overall calculation rule is used, forming a relationship between the acquired sensor variables of all the load sensors and the at least one load variable of the rotor blade, and having multiple calculation parameters, and, for parameterizing the sensor arrangement, the calculation parameters of the overall calculation rule are determined while at the same time taking into consideration acquired sensor variables of all the load sensors.

Claims

1. A method comprising: parameterizing a sensor arrangement comprising a plurality of load sensors of a rotor blade of a rotor of a wind power installation for acquiring at least one load variable, wherein the at least one load variable is representative of a load acting on the rotor blade, wherein the rotor blade has at least three load sensors, the parameterizing comprising: recording, by each of the load sensors, a load-dependent physical variable of the rotor blade, and outputting a variable indicative of the load-dependent physical variable as the acquired sensor variable, calculating the at least one load variable from the sensor variables, wherein at least one overall calculation rule is used, forming a relationship between the acquired sensor variables of all the load sensors and the at least one load variable of the rotor blade, and having a plurality of calculation parameters, and parameterizing the sensor arrangement, wherein the calculation parameters of the overall calculation rule are determined while at the same time taking into consideration acquired sensor variables of all the load sensors.

2. The method as claimed in claim 1, wherein no individual parameterization of individual load sensors takes place for determining the calculation parameters.

3. The method as claimed in claim 1, wherein the sensor variables are successively acquired in a plurality of acquisition steps in varying operational situations of the wind power installation, wherein in each acquisition step: a sensor variable is respectively acquired for each load sensor, so that multiple sensor variables are acquired in the acquisition step, forming a set of sensor variables, and at least one associated load variable is ascertained for the set of sensor variables as a reference load variable, wherein the acquisition steps are respectively repeated with a changed operational situation at least as often as the overall calculation rule has calculation parameters to be determined, and wherein the calculation parameters are determined in dependence on all the sensor variables acquired in the acquisition steps and ascertained associated load variables.

4. The method as claimed in claim 1, wherein the overall calculation rule has or is a calculation equation, which describes by the calculation parameters a relationship between the load variable and the sensor variables, wherein, for determining the calculation parameters, a system of equations comprising multiple calculation equations is set up, for each calculation equation of the system of equations: an ascertained reference load variable is used for the load variable, and acquired sensor variables associated with the ascertained reference load variable are used for the sensor variables, and the system of equations is resolved based on the calculation parameters.

5. The method as claimed in claim 1, wherein: a system of equations comprising a plurality of calculation equations of the overall calculation rule is set up in matrix form, wherein: an output vector for the ascertained reference load variables, a measurement matrix for the acquired sensor variables and a parameter vector for the calculation parameters to be determined such that the output vector is equal to a product of the measurement matrix times the parameter vector.

6. The method as claimed in claim 1, wherein: the calculation parameters comprise an offset k.sub.0, each load sensor is assigned at least one calculation parameter k.sub.i, and the overall calculation rule is obtained in that: for each of the load sensors, a product of the sensor variable x.sub.i of the respective load sensor i times the at least one calculation parameter k.sub.i associated with the load sensor is formed, and the load variable L is obtained as the sum of the products k.sub.i.Math.x.sub.i and the offset k.sub.0 based on the formula: $L=\underset{i=1}{\overset{n}{.Math.}}{k}_i.Math.x_i+k_0.$

7. The method as claimed in claim 1, wherein: for the successive acquisition of the sensor variables in varying operational situations, the operational situations are chosen such that different load variables including different bending moments, occur at the rotor blade, and wherein: the bending moments result from a dead weight of the rotor blade, and the bending moments are varied by the rotor being changed in its rotational position, and/or a blade angle of the rotor blade being changed.

8. The method as claimed in claim 1, wherein: for the successive acquisition of the sensor variables in varying operational situations in acquisition steps, a schedule is prescribed for the acquisition steps, the varying operational situations are set according to the schedule, and the parameterizing of the sensor arrangement is carried out after ending the schedule.

9. The method as claimed in claim 1, wherein, for acquiring the sensor variables, at least one operational setting is provided from the list comprising: the wind power installation is operated in an idling mode, a blade angle of the rotor blade is set, a power output is set, a torque of a generator connected to the rotor is set, and a rotational speed of the rotor is set, wherein for acquiring the sensor variables, at least one of the operational settings is varied.

10. The method as claimed in claim 1, wherein: the acquisition of the sensor variables for parameterizing the sensor arrangement takes place at wind speeds in a first wind speed range and a second wind speed range, the first wind speed range lies between a start-up wind speed and a first wind speed, which is greater than the start-up wind speed, the second wind speed range lies between the first wind speed and a second wind speed, which is greater than the first wind speed, and the acquisition is repeated at wind speeds in the first wind speed range if the acquisition previously took place at wind speeds in the second wind speed range.

11. The method as claimed in claim 1, wherein: the sensor arrangement is set up for acquiring at least two load variables, a dedicated overall calculation rule with dedicated calculation parameters is provided for each load variable, and wherein: one of the load variables is a blade bending moment of the rotor blade in a flapwise direction, and one of the load variables is a blade bending moment of the rotor blade in an edgewise direction, and one of the load variables is an axial force of the rotor blade, and wherein, for each load variable, a dedicated overall calculation rule, with dedicated calculation parameters, is used, in order to calculate the respective load variable from the sensor variables, and the calculation parameters of each overall calculation rule are respectively determined while at the same time taking acquired sensor variables of all the load sensors into consideration.

12. The method as claimed in claim 1, wherein in each acquisition step a reference load variable is calculated in dependence on a gravitational force that is acting on the rotor blade for each load sensor, wherein the gravitational force is converted into a coordinate system of the rotor blade while taking into consideration a blade angle of the rotor blade, a rotational position of the rotor, an angle of inclination of the rotor with respect to a horizontal, and/or an angle of inclination of the rotor blade with respect to a rotational plane of the rotor.

13. The method as claimed in claim 1, wherein for the successive acquisition of the sensor variables in varying operational situations in acquisition steps, the reference load variable is additionally ascertained in each acquisition step in dependence on aerodynamic forces occurring and/or aerodynamic moments occurring, which act on the rotor blade.

14. The method as claimed in claim 1, wherein: a non-linear relationship between the sensor variables and the load variable is taken into consideration the calculation parameters comprise the offset k.sub.0, altogether m calculation parameters k.sub.i,j are assigned to each load sensor, where m is greater than one, and the overall calculation rule in the case of n load sensors for the load variable L is obtained as: $L=\underset{i=1}{\overset{n}{.Math.}}\left(\underset{j=1}{\overset{m}{.Math.}}{k}_{i,j}.Math.x_i^j\right)+k_0.$

15. A wind power installation comprising: a sensor arrangement comprising a plurality of load sensors of a rotor blade of a rotor of the wind power installation for acquiring at least one load variable, which is representative of a load that acts on the rotor blade, wherein the rotor blade has at least three load sensors, wherein each of the load sensors records a load-dependent physical variable of the rotor blade and outputs a variable representative thereof as the acquired sensor variable, wherein the wind power installation has a control device, and wherein the control device is configured to parameterize the sensor arrangement according to the method as claimed in claim 1.

16. The method as claimed in claim 1, wherein no individual calibration and/or adjustment of individual load sensors takes place for determining the calculation parameters.

17. The method as claimed in claim 4, wherein more calculation equations are set up than the overall calculation rule has calculation parameters, so that the system of equations is overdetermined, and the system of equations is resolved such that a statistically optimal solution is obtained.

18. The method as claimed in claim 4, wherein: an approximation solution for the system of equations is found by forming a pseudoinverse of the measurement matrix, and/or the parameter vector has an offset, and the measurement matrix has an additional column corresponding to the offset, which is filled with the value 1, so that, in the multiplication of the measurement matrix by the parameter vector, the offset is respectively multiplied by the value 1.

19. The method as claimed in claim 9, wherein: each operational setting is retained for a predetermined test period for a plurality of acquisition steps and/or at least one operational setting is retained until multiple operational situations are in each case enacted, with an acquisition step for acquiring the sensor variables being respectively carried out.

20. The method as claimed in claim 11, wherein for determining the calculation parameters: a measurement matrix comprising acquired sensor variables for all the overall calculation rules together is recorded and used, and a dedicated output vector comprising ascertained reference load variables is used for each overall calculation rule.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0111] FIG. 1 shows a wind power installation in a perspective view.

[0112] FIG. 2 shows a rotor blade with a sensor arrangement.

[0113] FIG. 3 shows a sensor arrangement.

[0114] FIG. 4 shows a flow diagram for a method.

DETAILED DESCRIPTION

[0115] FIG. 1 shows a schematic representation of a wind power installation according to the invention. The wind power installation 100 has a tower 102 and a nacelle 104 on the tower 102. Provided on the nacelle 104 is an aerodynamic rotor 106 with three rotor blades 108 and a spinner 110. During the operation of the wind power installation, the aerodynamic rotor 106 is set in a rotary motion by the wind, and thereby also turns an electrodynamic rotor of a generator that is directly or indirectly coupled to the aerodynamic rotor 106. The electrical generator is arranged in the nacelle 104 and generates electrical energy. The blade angles of the rotor blades 108, which may also be referred to synonymously as pitch angles, can be adjusted by pitch motors at the rotor blade roots 109 of the respective rotor blades 108.

[0116] Three load sensors are respectively arranged on each of the rotor blades 108.

[0117] FIG. 2 shows a rotor blade 208 with a sensor arrangement 210. The sensor arrangement 210 has three load sensors 211, 213, 215. The sensor arrangement 210 is attached in the region of the blade root 220 of the rotor blade 208. In this case, the three load sensors 211, 213, 215 are distributed around the circumference of the rotor blade. Ideally, the load sensors 211, 213, 215 are offset in relation to one another by an angle of in each case 1200 around the circumference of the blade circumference. However, exact positioning does not matter.

[0118] FIG. 3 schematically shows the sensor arrangement 310 with three load sensors 311, 313, 315, which are distributed around the circumference of the rotor blade in the region of the blade root 320.

[0119] The three load sensors 311, 313, 315 therefore together form the sensor arrangement 310, which is set up for acquiring a load variable. In this case, the load variable should be determined in one of the spatial directions x, y, z of the coordinate system 320. The coordinate axis z in this case points into the figure and consequently corresponds to a direction in the longitudinal axis of the blade.

[0120] The load variable to be acquired may be for example a bending moment M.sub.x of the rotor blade in a flapwise direction x, a bending moment M.sub.y of the rotor blade in an edgewise direction y, or an axial force F.sub.z in a longitudinal direction z of the rotor blade. It is not required here that the measuring directions of the load sensors 311, 313, 315 lie along one of the coordinate axes x, y, z of the coordinate system 320.

[0121] If the rotor blade bends as a result of a load that is acting on the rotor blade, each of the load sensors 311, 313, 315 undergoes a change in length or strain. The physical variable of the change in length is acquired by the load sensors 311, 313, 315 in the form of a sensor variable representative thereof.

[0122] Therefore, if for example a bending moment M.sub.x acts in a flapwise direction x, each of the load sensors 311, 313, 315 undergoes a strain according to its position in the sensor arrangement 310, and acquires a sensor variable proportional to the strain.

[0123] In order to calculate the load variable from the sensor variables of the load sensors 311, 313, 315, the sensor arrangement 310 is parameterized.

[0124] An overall calculation rule is used as a basis for the parameterization of the sensor arrangement 310. The load variable can consequently be calculated on the basis of the overall calculation rule, which forms a relationship between the acquired sensor variables of the load sensors 311, 313, 315 and the load variable. In this case, the load variable can be determined directly from the measured sensor variables. It is therefore not necessary for the physical variable, specifically the strain, to be determined first.

[0125] The overall calculation rule has in this case multiple calculation parameters. Depending on which load variable is to be determined, different calculation parameters are used.

[0126] For the bending moment M.sub.x in the flapwise direction x, for example the overall calculation rule:

M.sub.x=k.sub.x,1.Math.x.sub.1+k.sub.x,2.Math.x.sub.2+k.sub.x,3.Math.x.sub.3+k.sub.x,0

[0127] Is used, with the calculation parameters k.sub.x,1, k.sub.x,2, k.sub.x,3, k.sub.x,0, where k.sub.x,0 forms an offset. The first load sensor 311 in this case measures the first sensor variable x.sub.1, the second load sensor 313 measures the second sensor variable x.sub.2 and the third load sensor 315 measures the third sensor variable x.sub.3.

[0128] For the same set of sensor variables comprising sensor variables x.sub.1, x.sub.2, x.sub.3, with the further calculation parameters k.sub.y,1, k.sub.y,2, k.sub.y,3, k.sub.y,0 the bending moment M.sub.y in the edgewise direction y can also be calculated according to:

M.sub.y=k.sub.y,1.Math.x.sub.1+k.sub.y,2.Math.x.sub.2+k.sub.y,3.Math.x.sub.3+k.sub.y,0.

[0129] For the parameterization of the sensor arrangement 310, therefore the calculation parameters are determined.

[0130] The first, second and third sensor variables x.sub.1, x.sub.2 and x.sub.3 are in this case the same for both bending moments.

[0131] FIG. 4 shows a method 400 for parameterizing the sensor arrangement 310.

[0132] In the starting block 410, the parameterization is initiated. The parameterization is preferably initiated whenever enough wind is blowing for the rotor of the wind power installation to turn, but the wind speed is so low that only stresses that are caused by gravitation are taken into consideration, but further stresses can be ignored. The bending moments occurring consequently result from a dead weight of the rotor blade.

[0133] An acquisition step 420 is then carried out at time step t=t.sub.1. In the acquisition step 420, a sensor variable x.sub.1(t=t.sub.1), x.sub.2(t=t.sub.1), x.sub.3(t=t.sub.1) is acquired for each load sensor 311, 313, 315 in a sensor-variable-set determining step. The sensor variables x.sub.1(t=t.sub.1), x.sub.2(t=t.sub.1), x.sub.3(t=t.sub.1) of all the load sensors 311, 313, 315 together form the set of sensor variables at time step t=t.sub.1.

[0134] Also carried out in the acquisition step 420 is a reference-load-variable determining step 423. In this, a reference load variable L.sub.ref(t=t.sub.1) is determined. The reference load variable L.sub.ref(t=t.sub.1) corresponds here to the load variable that is likely to occur at time step t=t.sub.1 and can be calculated by using the weight force.

[0135] The reference load variable L.sub.ref is for example a bending moment M.sub.x in the flapwise direction x, a bending moment M.sub.y in the edgewise direction y or an axial force F.sub.z in the longitudinal direction z. In the reference-load-variable determining step 423, however, it is also possible for multiple reference load variables to be determined.

[0136] In the storage step 430, the reference load variable L.sub.ref(t=t.sub.1) is stored in an output vector {right arrow over (L)}.sub.ref. Similarly, the set of sensor variables, that is to say the sensor variables x.sub.1(t=t.sub.1), x.sub.2(t=t.sub.1), x.sub.3(t=t.sub.1), is stored in a measurement matrix A.

[0137] As soon as enough data have been stored, particularly after a predetermined number of repetitions, the procedure continues with a parameterizing step 440. Otherwise, a further acquisition step 420 is carried out in the next time step. In this case, with each new acquisition step an operational situation of the wind power installation is varied. By changing the operational situation, it is intended that the reference load variable to be determined changes. In particular, this may mean that the rotor has continued to turn. The turning of the rotor has the effect that the gravitational force leads to a changed strain of the rotor blade in the region of the load sensors. Consequently, the reference load variable L.sub.ref also changes.

[0138] The operational situation may however also be varied by for example a blade angle of the rotor blade being changed.

[0139] Furthermore, an operational setting may also be changed. The changing of the operational setting is likewise intended to have the effect of changing the reference load variable. However, the operational setting does not have to be varied after each acquisition step 420, but instead may be retained for multiple acquisition steps 420. Consequently, for example, the continued turning of the rotor does not represent a changed operational setting, but leads to a changed operational situation. The operational setting can however be changed by variation of the blade angle.

[0140] In the acquisition step 420, the set of sensor variables and the reference load are then repeatedly acquired in changed operational situations. This takes place in the sensor-variable-set determining step 421 and in the reference-load-variable determining step 423. Operational settings may possibly also be varied. The variables thus acquired are stored in the storage step 430, in the next row of the output vector or the measurement matrix in each case.

[0141] After p acquisition steps 420 and storage steps 430, there is consequently a measurement matrix:

[00010]$A=\left(\begin{array}{cccc}{x}_1\left(t=t_1\right)& x_2\left(t=t_1\right)& x_3\left(t=t_1\right)& 1\\ x_1\left(t=t_2\right)& x_2\left(t=t_2\right)& x_3\left(t=t_3\right)& 1\\ .Math.& .Math.& .Math.& 1\\ x_1\left(t=t_p\right)& x_2\left(t=t_p\right)& x_3\left(t=t_p\right)& 1\end{array}\right)$

and also an output vector:

[00011]$\stackrel{.fwdarw.}{L}=\left(\begin{array}{c}{L}_{\mathrm{ref}}\left(t=t_1\right)\\ L_{\mathrm{ref}}\left(t=t_2\right)\\ .Math.\\ L_{\mathrm{ref}}\left(t=t_p\right)\end{array}\right).$

[0142] A schedule is preferably used as a basis here, so that in the storage step 430 enough data have been stored specifically when the schedule has been ended. Consequently, the number p of acquisition steps may be prescribed in the schedule.

[0143] It may for example be prescribed according to the schedule to carry out an acquisition step 420 after each turning of the rotor by 1 and to change the blade angle after two full turns, while for example three different blade angles are measured. The number p of acquisition steps would in this case be 2*3*360=2160.

[0144] Once the schedule has been ended, the sensor arrangement is parameterized in the parameterizing step 440 in that the calculation parameters are determined.

[0145] In this case, the calculation parameters are determined on the basis of the measurement matrix A, while at the same time taking into consideration all the sensor variables acquired during the parameterization. In just one computing step, the parameter vector {right arrow over (k)}, which has the calculation parameters, is determined for this purpose by using:

{right arrow over (k)}=(A.sup.T.Math.A).sup.1.Math.A.sup.T.Math.{right arrow over (L)}.sub.ref.

[0146] In the subsequent completion step 450, the calculated parameters are stored and the parameterization is ended.

[0147] If the sensor arrangement is parameterized for a bending moment M.sub.x in the flapwise direction x, the calculation parameters k.sub.x,1, k.sub.x,2, k.sub.x,3, k.sub.x,0 are correspondingly determined and stored.

[0148] Once parameterization has taken place, the sensor arrangement may be used for calculating load variables. Therefore, once the parameterization for the bending moment M.sub.x has been carried out, the calculation takes place on the basis of the overall calculation rule:

M.sub.x=k.sub.x,1.Math.x.sub.1+k.sub.x,2.Math.x.sub.2+k.sub.x,3.Math.x.sub.3+k.sub.x,0.

[0149] To ensure the most accurately determined calculation parameters possible, the method 400 for parameterizing the sensor arrangement 310 is repeated after a predetermined time, for example every three months.

[0150] The following has particularly also been recognized and the following is proposed.

[0151] A method for parameterization of a sensor arrangement of a wind power installation is therefore proposed, the sensor arrangement being arranged on a rotor blade of the wind power installation and consisting of at least three load sensors.

[0152] The parameterization in this case preferably takes place in a two-stage process, consisting of a schedule or parameterizing routine and a parameterizing step.

[0153] The aim of the parameterizing routine is to acquire and store measured values of the load sensors respectively under different bending moments on the rotor blade and in each case an associated calculated reference bending moment. For this, the wind power installation is operated in a mode in which a bending moment applied to the rotor blade can be calculated with great accuracy.

[0154] It is particularly proposed for the parameterizing routine to operate the wind power installation in an idling mode and to prescribe varying blade angles for the rotor blade, so that the reference bending moment corresponds approximately to a natural moment.

[0155] In order that the aerodynamic forces are negligible, the parameterization of the sensor arrangement is preferably performed at low wind speeds. On the other hand, the wind must be strong enough to carry out the parameterization in an acceptable time. The specific wind speeds at which such a parameterization is carried out are dependent on the cut-in wind speed of the wind power installation at the respective site. If these conditions are not satisfied, particularly if the wind is stronger than in good conditions, but a parameterization is necessary, the parameterization is nevertheless carried out and is repeated later in good conditions.

[0156] Alternatively, the aerodynamic forces and moments could be additionally taken into consideration, in order to make an accurate parameterization of the sensor arrangement also possible when there is a lot of wind.

[0157] Once the parameterizing routine has been completed, the parameterizing step is performed. The parameterizing step serves for calculating the calculation parameters. After completion of the parameterizing routine, the calculation parameters are calculated from the recorded sensor variables and the reference bending moments, so that the mean squared error between the reference bending moments and the bending moments calculated from the calculation parameters and the sensor variables is minimal.

[0158] It is assumed here that the bending moments are proportional to the strain of the rotor blade. In fact, as from a certain strain, a non-linearity occurs. The deviation from the linearity can, if need be, be taken into consideration inversely in the parameterizing routine or in the parameterizing step.

[0159] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.