Computer-implemented method and device for adjusting a blade load measuring system of a rotor blade of a wind turbine, wind turbine with at least one rotor blade with a strain sensor and computer-readable storage medium

Description

Technical field

[0001] The present invention relates generally to a computer-implemented method and a device for adjusting a blade load measuring system of a rotor blade of a wind turbine, a wind turbine with at least one rotor blade with a strain sensor and a computer-readable storage medium. State of the art

[0002] A wind turbine converts wind energy into electrical energy. The wind exerts a force on at least one rotor blade of the wind turbine, converting the wind's kinetic energy into the rotor's rotational kinetic energy. The rotor drives an electric generator, which feeds electrical energy into a power grid.

[0003] One or more rotor blades of a wind turbine are increasingly being equipped with one or more sensors, such as strain gauges, which are used for control purposes, particularly for load reduction, and / or for monitoring turbine operation, especially for safety and maintenance purposes. Forces and / or moments acting on the rotor blade are determined from the strain gauge measurements. To obtain reliable and accurate readings from the strain gauges and thus correct load measurement results, the strain gauges must be calibrated before commissioning. This means that any deviation of a load measurement from a target value (a reference) is identified and documented. The calibration parameters for the strain gauges are then set or adjusted so that any measurement deviation from a target value is minimized or remains within a defined specification or tolerance limits.

[0004] Currently, the following parameters are required to calibrate a strain gauge for blade load measurement: the mass of the rotor blade, the arrangement of the sensors on the rotor blade, the current rotor angle of the wind turbine, the current wind speed, and the current pitch angle. The pitch angle and the current rotor angle are the most important input parameters. The current wind speed is used for a filtering mechanism to eliminate measurements taken at such high wind speeds that they could distort the results. High wind speeds lead to additional moments that can imprecise the calibration, so filtering improves the calibration quality of the strain gauge.

[0005] For the actual adjustment, a controlled and defined run of the rotor blade is performed, for example, several revolutions at low wind speeds. In particular, the pitch angle of the rotor blade is precisely controlled and adjusted to different values. Since wind turbines operate with varying pitch angles, it is necessary to perform adjustment runs at different pitch angles to fully replicate the behavior of the strain sensors. The rotor blade is brought into defined positions where known forces or bending moments act upon it. Defined positions include, for example, positions of the rotor blade perpendicular or parallel to the ground. The position of the rotor blade can be unambiguously determined by measuring the current rotor angle. Therefore, measuring the rotor angle is absolutely essential for adjustment.In these defined positions, for example, only a gravitational force acts on the rotor blade. At low wind speeds, the aerodynamic forces acting on the rotor blade are negligible. Taking into account the acting gravity, the position of the strain gauges, and the mass of the rotor blade, bending moments and axial forces acting on the rotor blade are determined. Simultaneously, the strain gauges detect forces and bending moments based on an initial set of adjustment parameters. Since the acting forces and moments are known, the forces and bending moments measured by the strain gauges are compared with the known forces and bending moments, and the adjustment parameter set for the strain gauges is adjusted according to the deviation.

[0006] For example, EP 2 531 722 A1 teaches a method for the in-situ adjustment of load sensors in a wind turbine. First, the rotor azimuth angle and the angle of attack of the first wind turbine blade are determined. Next, loads in the first cross-section of the first wind turbine blade are measured using the first load sensors. Based on the rotor azimuth angle and the angle of attack, theoretical loads acting on the blade are calculated. The measured loads are compared with the calculated theoretical loads, and the first load sensor is adjusted based on this comparison. Problems solved by the invention

[0007] A disadvantage of the previously described method for adjusting a strain sensor is that the current rotor angle of the wind turbine must be measured. However, a rotor angle often cannot be measured unambiguously because measurement limitations result in an angular offset between the actual and measured rotor angle. If interference signals occur, or if the measured rotor angle signal is unreliable or inaccurate, this impairs the adjustment of the strain sensor.

[0008] Based on this prior art, it is an object of the present invention to overcome the aforementioned disadvantages. A means is needed to adjust strain gauges accurately and reliably, particularly without measuring or using a rotor angle. Means to solve the problem

[0009] The problem is solved by a computer-implemented method for adjusting a first blade load measuring system with at least one strain sensor on a first rotor blade of a wind turbine according to claim 1. This enables simple and accurate adjustment of the blade load measuring system and eliminates the need to measure or use a rotor angle in the adjustment process. Furthermore, the problem is solved by a device for adjusting a first blade load measuring system with at least one strain sensor on a first rotor blade of a wind turbine according to claim 9, by a wind turbine according to claim 13, and by a computer-readable storage medium according to claim 14.

[0010] In particular, the task is solved by a computer-implemented method for adjusting a first blade load measuring system with at least one strain sensor on a first rotor blade of a wind turbine, comprising the following steps: a) Measuring a first acceleration with a first acceleration sensor; b) Determining a first reference bending moment and / or a first reference axial force based on the first measured acceleration; c) Determining a first measured bending moment and / or a first measured axial force based on measurements from the at least one strain sensor of the first blade load measuring system and a first set of adjustment parameters associated with the first blade load measuring system with first initial adjustment parameter values; d) Determining a first deviation of the first reference bending moment and / or the first reference axial force from the first measured bending moment and / or the first measured axial force; e) Adjusting the adjustment parameter values ​​of the first set of adjustment parameters for the first blade load measuring system such that the first deviation is less than or equal to a threshold value.

[0011] One aspect of the present invention is therefore to adjust a blade load measuring system without using a rotor angle of the wind turbine.

[0012] Adjusting based on accelerations can be suitable for increasing the accuracy of the adjustment.

[0013] A blade load measuring system can be understood to be, in particular, a strain sensor system comprising at least one strain sensor, in particular several strain sensors, in particular at least three, and further, in particular, at least four strain sensors. The at least one strain sensor can be configured as a strain sensor that measures one or more strains in one direction. The strain sensor can preferably be positioned and oriented such that it measures one or more strains in the direction of a blade axis. For this purpose, the strain sensor can be arranged in any first plane of the rotor blade cross-section. A plane of a rotor blade cross-section can, in particular, be understood to be a plane through a cross-section of a rotor blade that is orthogonal to a blade axis of the rotor blade.In particular, the strain sensor can be configured to measure multiple strains in the direction of the blade axis, which are necessary for determining axial forces and / or bending moment. Specifically, if the strain sensor can only measure one strain in the direction of the blade axis, the blade load measurement system can include multiple strain sensors that can also detect strains in the direction of the blade axis. These strain sensors can, in principle, be arranged in any identical or different planes. For example, the strain sensors can each be arranged in a common plane, such as the first plane, of the rotor blade cross-section, or in several spaced-apart planes of the rotor blade cross-section.

[0014] The first accelerometer can detect an initial acceleration acting in a rotating rotor hub. For example, the first accelerometer could be an accelerometer system that measures accelerations in three orthogonal spatial directions. For instance, the first accelerometer could be a 6-DOF accelerometer.

[0015] A first measured acceleration can be understood in particular as an acceleration that includes acceleration components in several spatial directions, especially in three, in particular orthogonal, spatial directions.

[0016] According to the invention, the first reference bending moment and / or the first reference axial force is determined based on the first measured acceleration. The determination of the first reference bending moment and / or the first reference axial force is carried out, in particular, without taking the rotor angle into account.

[0017] Whether the first measured bending moment and / or the first measured axial force are used for adjustment can depend, in particular, on the number of strain gauges. For example, when using three strain gauges, the first measured axial force can be taken into account. If four strain gauges are used, either the first measured bending moment or, alternatively, both the first measured axial force and the first measured bending moment can be used.

[0018] According to the invention, the first measured bending moment and / or the first measured axial force are determined based on the measured values ​​from the at least one strain sensor of the first blade load measuring system and the initial adjustment parameter values ​​of the first adjustment parameter set assigned to the first blade load measuring system.

[0019] The first reference bending moment and / or the first reference axial force can be compared with the first measured bending moment and the first measured axial force, and a first deviation between the first reference bending moment and / or the first reference axial force from the first measured bending moment and / or the first measured axial force can be determined.

[0020] Based on the initial deviation, the adjustment parameter values ​​of the first adjustment parameter set are determined such that the initial deviation is less than or equal to a threshold value. If the initial deviation is less than or equal to a defined threshold value, the adjustment parameter values ​​of the first adjustment parameter set are selected for adjustment. For example, the threshold may specify an initial deviation of at most 5.00%, preferably at most 3.00%, and more preferably at most 1.00%.

[0021] The first set of adjustment parameters for the first blade load measurement system can include one or more suitable parameters for adjusting the first blade load measurement system or the strain sensor. The initial adjustment parameter values ​​of the first adjustment parameter set can be any predefined parameter values. Computation time can be reduced by specifying suitable adjustment parameter values ​​as the initial adjustment parameter values. For example, initial adjustment parameter values ​​from a structurally and functionally similar wind turbine can be used. Optionally, initial adjustment parameter values ​​can be used that are determined from the stiffness of the first rotor blade and / or the position of the first strain sensor and / or the wavelength of the first strain sensor.

[0022] Based on the adjusted adjustment parameters of the adjustment matrix, the bending moments in the load reference plane in mutually orthogonal load vectors and / or the axial forces acting orthogonally to the load reference plane can be determined.

[0023] The first axial force can be defined as a force acting from the hub center along the blade axis towards the blade tip. Furthermore, a force acting at the center of gravity of the first rotor blade can be determined from the first measured acceleration and the mass of the first rotor blade. Additionally, a first bending moment can be determined based on the weight of the blade and the distance of its center of gravity from the hub center. The mass and center of gravity of the first rotor blade can be determined, for example, from a data sheet for the first rotor blade or by weighing the blade during a step of the blade manufacturing process or before the first blade is mounted. This has the advantage that a first bending moment and / or a first axial force with respect to the blade flange can be easily deduced solely from the mass of the first rotor blade, the distance of its center of gravity to the blade flange, and the first measured acceleration.Furthermore, a design mass distribution can also be used to determine the center of gravity and mass in relation to each blade radius position and thus to adjust bending moments and / or axial forces in relation to this blade section.

[0024] As already described, the wind turbine can comprise at least one rotor blade. Furthermore, the wind turbine can comprise several rotor blades, in particular two, and more specifically three. The rotor blades can each be arranged uniformly around the hub at an angular offset from one another. For example, if two rotor blades are provided, they can be arranged at an angular offset of 180° from one another. If, for example, three rotor blades are provided, they can each be arranged at an angular offset of 120° from one another. The rotor blades can be identical or at least approximately identical with respect to their dimensions, mass, mass distribution, and center of gravity, and thus their static moment, i.e., the product of mass and distance of the center of gravity to a reference point. The deviation is preferably at most 5%, more preferably at most 2%, and more preferably 1%.

[0025] In an advantageous embodiment, the method can include adjusting a second blade load measuring system with at least one strain sensor on a second rotor blade, comprising the following steps: a) Determining a second acceleration associated with the second rotor blade, based on the first measured acceleration, taking into account an angular offset between the first and a second rotor blade; b) Determining a second reference bending moment and / or a second reference axial force based on the second acceleration; c) Determining a second measured bending moment and / or a second measured axial force based on measurements from the at least one strain sensor of the second blade load measurement system and a second set of adjustment parameters associated with the second blade load measurement system, with second initial adjustment parameters; d) Determining a second deviation of the second reference bending moment and / or the second reference axial force from the second measured bending moment and / or the second measured axial force;e) Adjusting the adjustment parameter values ​​of the second adjustment parameter set for the second leaf load measuring system such that the second deviation is less than or equal to a threshold value.

[0026] The second acceleration is assigned to the second rotor blade and is determined from the first measured acceleration, taking into account an angular offset between the first and second rotor blades. In other words, the second acceleration represents a transformation of the first measured acceleration from the first rotor blade to the second rotor blade, depending on the angle between the rotor blades. The second reference bending moment and / or the second reference axial force can be determined from the second acceleration. The second reference bending moment and / or the second reference axial force are typically referenced to the blade flange, but can also be referenced to any other position on the second rotor blade. At least one second blade load measurement system with at least one strain sensor is arranged on the second rotor blade, which determines the second measured bending moment and / or the second measured axial force.The type and positioning of the second strain sensor must comply with the same conditions as the at least one strain sensor of the first blade load measuring system on the first rotor blade.

[0027] The second deviation can be determined by comparing the second reference bending moment and / or the second reference axial force with the second measured bending moment and / or the second measured axial force. Based on the second deviation, the adjustment parameter values ​​of the second adjustment parameter set are adjusted so that the second deviation is less than or equal to the threshold value. The threshold value for the second deviation can, in particular, correspond to the threshold value for the first deviation. By measuring only a first acceleration with a first accelerometer, the blade load measurement system on the second rotor blade can also be easily adjusted using the angular offset between the rotor blades, based on the number of rotor blades.

[0028] The second set of adjustment parameters for the second blade load measurement system can include one or more suitable parameters for adjusting the second blade load measurement system or strain sensor. The initial adjustment parameter values ​​of the second set can be any predefined parameter values. Computation time can be reduced by specifying suitable adjustment parameter values ​​as the initial values. For example, initial adjustment parameter values ​​from a structurally and functionally similar wind turbine can be used. Optionally, initial adjustment parameter values ​​can be used that are determined from the stiffness of the second rotor blade and / or the position of the second strain sensor and / or the wavelength of the second strain sensor.

[0029] In an advantageous embodiment, steps a) to d) can be repeated, in particular at least 50, further in particular at least 100, further in particular at least 1000, further in particular at least 10000 repetitions, wherein different pitch angles and / or different accelerations are recorded at each repetition, and then in step e) the adjustment parameter values ​​are adjusted such that the first and second deviations recorded in step d) are less than or equal to a threshold value.

[0030] For example, steps a) to d) can be performed a predetermined number of times or within a predetermined time period. In principle, there is no limit to either the time period or the number of repetitions of steps a) to d). To increase the accuracy of the adjustment, the time period and / or the number of repetitions of steps a) to d) can be set to a minimum value. Likewise, to reduce time and costs, the time period and / or the number of repetitions of steps a) to d) can be limited to a maximum value. Similarly, the time period and / or the number of repetitions of steps a) to d) can be interrupted and resumed at a later time. This has the advantage that the adjustment procedure can be interrupted if, due to external environmental influences, operating the wind turbine for adjustment purposes cannot be carried out safely.The total time interval can be, for example, at least two minutes, preferably at least ten minutes, more preferably at least 15 minutes, and / or at most one hour, preferably at most 45 minutes, more preferably at most 30 minutes. The time interval or the number of repetitions of steps a) to d) can be determined, in particular, depending on how often a first measured acceleration is discarded. The first and second deviations determined in step d) can, for example, be combined into a common first and second deviation, for example, in the form of a vector or a matrix comprising the first and second deviations. By first repeatedly performing steps a) to d), a set of data, in particular first and second deviations, can be collected, on the basis of which a first set of adjustment parameters is determined and selected.This allows for adjustments to be made at a later time, depending on the predetermined time period or the predetermined number of trials.

[0031] In an advantageous embodiment, a pitch angle can be used and / or a defined pitch angle, in particular different pitch angles, can be set before step a). For example, pitch angle signals that are typically acquired by the wind turbine can be used. A wind turbine is usually operated at different pitch angles. By setting a defined pitch angle, in particular by setting different pitch angles, the first rotor blade can always be brought into an aerodynamically efficient position that is both energy-efficient and safe, so that the rotor of the wind turbine always operates safely at its optimal operating point. Furthermore, determining the pitch angle allows for the identification of a critical operating condition of the wind turbine.By setting a defined pitch angle, damage to the wind turbine can be avoided during the calibration of the first blade load sensor.

[0032] In an advantageous embodiment, the first acceleration measured by the first accelerometer can be discarded if the wind speed exceeds a predefined threshold. The prevailing wind speed in the vicinity of the wind turbine can be measured by wind speed sensors located on or near the turbine. The measured wind speed can be compared to a predefined threshold for a maximum wind speed. If the current wind speed is lower than the threshold for the maximum wind speed, the first measured acceleration can be used for further adjustment of the blade load measurement system.If the wind speed is equal to or greater than the wind speed threshold for the maximum wind speed, the first measured acceleration can be discarded. This ensures that the first reference bending moment is not excessively influenced and thus distorted by wind forces. The wind speed threshold for the maximum wind speed can be, for example, 10 m / s, preferably 8 m / s, more preferably 5 m / s, and more preferably 3 m / s.

[0033] In a preferred embodiment, the first acceleration sensor can measure accelerations in at least one, in particular two, further in particular three spatial directions and / or be designed by an inertial measuring unit and / or an acceleration sensor, preferably two, further in particular three acceleration sensors, can be arranged in the hub of the wind turbine.

[0034] The first accelerometer can determine positive and negative translational accelerations along one, in particular two, and further, in particular all three spatial directions, i.e., in an x, y, and z direction. The first measured acceleration can thus include an acceleration in at least one, in particular two, and further, in particular three directions from the x, y, and z directions. By using more than one first accelerometer, the measurement system can be designed with functional redundancy so that if one accelerometer fails, the other accelerometers can take over the measurement function. For this purpose, the accelerometers are functionally and structurally identical.Furthermore, the accuracy of the measurement can be increased by comparing the measured values ​​of the individual accelerometers with each other in order to identify differences and thus possible measurement errors and to obtain a correct measured value.

[0035] In particular, the first accelerometer can be located in the hub of the rotor. Specifically, the first accelerometer can be oriented such that it can measure an acceleration in the direction of a blade axis of the first rotor blade. The first accelerometer can further measure two additional accelerations orthogonal to the first measured acceleration.

[0036] Different forces and moments can act on the rotor blade in each blade position, and these must be accurately recorded by the blade load measurement system. Therefore, it may be necessary to determine the acceleration uniquely associated with a rotor blade position using the first accelerometer. The first measured acceleration can be associated with the first rotor blade position of the first rotor blade. The second measured acceleration can be associated with the second rotor blade position of the second rotor blade, where the second rotor blade may be positioned around the hub at an angular offset relative to the first rotor blade. A multitude of rotor blade positions can be associated with a single measured acceleration. For example, an acceleration associated with a rotor blade position can be specified using an acceleration vector, where the vector includes accelerations in three orthogonal spatial directions.Based on the measured acceleration, bending moments and axial forces can be directly determined using the known center of gravity and mass of the blade.

[0037] If the first accelerometer is offset from the blade axis by a mounting misalignment, such as a translational or rotational displacement, particularly an angular misalignment, the accelerometer will measure different accelerations. Precise positioning and alignment of the accelerometer on the blade axis can ensure that the first measured acceleration, and thus the first reference bending moment and / or the first reference axial force, are not distorted due to a mounting misalignment. In practice, however, this may not always be feasible, and the actual installation direction of the sensors may deviate from the described optimal installation direction. It may therefore be necessary to identify this mounting misalignment and take it into account when adjusting the blade load measurement system to increase the accuracy of the adjustment.

[0038] The strain sensor can be any suitable sensor, such as a piezoelectric strain gauge or a fiber Bragg grating graphene, to detect strains with or without temperature compensation. Depending on the application, it may be necessary to position the strain sensor at a specific location on the first or second rotor blade. Therefore, the strain sensor can, in principle, be located at any position on or within the first or second rotor blade.

[0039] In an advantageous embodiment, the at least one strain sensor of the first or second blade load measuring system can be arranged on the first or second rotor blade in a radial area of ​​at most 50%, preferably at most 30%, of the rotor blade's length, extending from the blade flange. This further increases the accuracy of the first or second measured bending moment and / or the first or second measured axial force, and thus the accuracy of the adjustment. In an advantageous embodiment, the adjustment of the first and / or second blade load measuring system on the first and / or second rotor blade can be performed by a computing device on-site at the wind turbine and / or by a remote computing device. Depending on the application, adjustment by a computing device on-site at the wind turbine or by a remote computing device may be advantageous.A computing unit located on-site at the wind turbine, for example in offshore wind turbines, may be suitable for performing the on-site adjustment of the blade load measurement system. A remote computing unit may be desirable, for example, to make corrections to the adjustment procedure or to monitor the adjustment process. If the adjustment is performed by a remote computing unit, a unit for storing measurement data and for wirelessly or via cable transmitting the measurement data to the remote computing unit is particularly advantageous. The computing unit can be part of the blade load measurement system. The computing unit can consist of one or more computing units. Furthermore, the adjustment of the first and / or second blade load measurement systems can be performed by a single, i.e., the same, computing unit or by different computing units.

[0040] The aforementioned problem is further solved in particular by a device for adjusting a first blade load measuring system with at least one strain sensor in a first rotor blade of a wind turbine, which has the following features: Unit for measuring acceleration, configured to measure a first acceleration with a first acceleration sensor; unit for determining a bending moment and / or an axial force, configured to determine a first reference bending moment and / or a first reference axial force based on the first measured acceleration and to determine a first measured bending moment and / or a first measured axial force based on measurements from the at least one strain sensor of the first blade load measuring system and a first set of adjustment parameters associated with the first blade load measuring system with first initial adjustment parameter values; unit for determining a deviation of bending moments and axial forces, configured to determine a first deviation of the first reference bending moment and / or the first reference axial force from the first measured bending moment and / or the first measured axial force;Unit for adjusting the calibration parameter values ​​of a calibration parameter set for a leaf load measuring system, which is designed to adjust the calibration parameter values ​​of the first calibration parameter set for the first leaf load measuring system such that the first deviation is less than or equal to a threshold value.

[0041] The device described herein can be used, in particular, for adjusting a first leaf load measuring system with at least one strain sensor, using the method described herein, or the method can be implemented by the described device. Therefore, the modifications and further developments described with regard to the method are also applicable to the device.

[0042] In an advantageous embodiment, the device can be suitable for adjusting a second blade load measuring system with at least one strain sensor on a second rotor blade of a wind turbine, wherein the unit for measuring an acceleration is configured to determine a second acceleration based on the first measured acceleration and taking into account an angular offset between the first and the second rotor blade; wherein the unit for determining a bending moment and / or an axial force is configured to determine a second reference bending moment and / or a second reference axial force based on the second acceleration and to determine a second measured bending moment and / or a second measured axial force based on measurements from the at least one strain sensor of the second blade load measuring system and a second set of adjustment parameters associated with the second blade load measuring system with second initial adjustment parameter values;wherein the unit for determining a deviation of bending moments and axial forces is configured to determine a second deviation of the second reference bending moment and / or the second reference axial force from the second measured bending moment and / or the second measured axial force; wherein the unit for adjusting adjustment parameter values ​​of an adjustment parameter set for a blade load measuring system is configured to adjust adjustment parameter values ​​of the second adjustment parameter set for the second blade load measuring system such that the second deviation is less than or equal to a threshold value.

[0043] In an advantageous embodiment, the device may further comprise a pitch angle usage and / or adjustment unit to use a pitch angle and / or to set a defined pitch angle, in particular different pitch angles.

[0044] In an advantageous embodiment, the device may further include a unit for rejecting an acceleration, which is configured to compare a wind speed with a wind speed threshold and to select the first measured acceleration if the wind speed is less than a wind speed threshold and to reject the first measured acceleration if the wind speed is greater than a wind speed threshold.

[0045] The problem is further solved in particular by a wind turbine having a rotor with a hub and a rotor blade extending radially from the hub, wherein the number of rotor blades includes at least a first rotor blade, and the wind turbine is equipped with a device as described above.

[0046] The advantages are similar or identical to those already described in connection with the procedure described above.

[0047] The problem is further solved in particular by a computer-readable storage medium which contains instructions that cause the device according to one of claims 9 to 12 to perform the method steps according to one of claims 1 to 8.

[0048] Similar or identical advantages arise as those already described in connection with the method described above. Further embodiments are described in the dependent claims. Brief description of the drawings

[0049] The invention will now be explained in more detail using exemplary embodiments. These will show: Figure 1 : a schematic side view of a wind turbine with rotor blades according to an embodiment described herein; Figure 2: a schematic side view of a rotor blade according to an embodiment described herein; Figure 3 : a flowchart of a method for adjusting a first blade load measuring system with at least one strain sensor on a first rotor blade according to an embodiment described herein. Figure 4 : a flowchart of a method for adjusting a second blade load measuring system with at least one strain sensor on a second rotor blade according to an embodiment described herein. Description of the embodiment(s)

[0050] Exemplary embodiments of the invention are explained below. In the drawings, identical reference numerals denote the same or similar features of the respective embodiments.

[0051] Figure 1Figure 1 shows a schematic side view of a wind turbine 100 with a first 201, second 202, and third (not shown) rotor blade according to the embodiments described herein. The wind turbine 100 comprises a tower 101 and a nacelle 102. A rotor is attached to the nacelle 102. The rotor includes a hub 103 to which the rotor blades 201 and 202 are attached. According to typical embodiments, the rotor has at least one, preferably two, rotor blades, and more preferably three. During operation of the wind turbine, the rotor, i.e., the hub 103 with the rotor blades mounted thereon, rotates about an axis 200, which corresponds to a central axis of the nacelle 102 through the hub center. The nacelle 102, or rather its central axis 200, is inclined at a tilt angle α of eight degrees relative to a horizontal orientation with respect to a flat, horizontal earth surface, i.e., a horizontal central axis 203.An axis 211 runs along the longitudinal extent of each rotor blade 201, 202. The rotor blades 201, 202, or rather their respective axes 211, are inclined away from the tower by a cone angle β of four degrees with respect to an axis 204 in a plane of rotation of the rotor, or perpendicular to the central axis 200. This drives a generator for electricity production.

[0052] As in Figure 1 As shown, at least one first acceleration sensor 310 is provided in the hub 103. The first acceleration sensor 310 is connected via a signal line 300 to an evaluation unit 330, which evaluates the measured signals. According to some embodiments, which can be combined with other embodiments, the first acceleration sensor 310 is a 6-DOF acceleration sensor that measures accelerations and angular accelerations in three spatial directions, i.e., six degrees of freedom.

[0053] Furthermore, in Figure 1 A first blade load measuring system 410 comprising four strain sensors is arranged near the blade flange on the first rotor blade 201. Each strain sensor is designed as a fiber optic sensor. For fiber optic strain sensors, an optical signal is transmitted to the evaluation unit 330 by means of a light guide 400, for example an optical fiber.

[0054] Figure 2 Figure 1 shows a schematic side view of the first rotor blade 201 according to the embodiments described herein. The length I of the rotor blade 201 extends from a blade flange 221 to a blade tip 231. In Fig. 2 The center of gravity (SP) and its distance dSP from the rotor blade flange are also illustrated. Furthermore, it shows Figure 2The positioning of the first blade load measuring system 410 on the first rotor blade at a distance d 410 of 2% of the length of the rotor blade starting from the blade flange 221. The first blade load measuring system comprises four strain sensors arranged symmetrically within a first plane e 410 of a rotor blade cross-section, so that only bending moments are required for adjustment.

[0055] Figure 3Figure 1 shows a flowchart of a method 500 for adjusting the first blade load measuring system 410 and its strain sensors according to the embodiment described herein. When the rotor, and thus the first rotor blade 201, rotates about the axis of rotation 200, the first acceleration sensor 310 and the strain sensors of the first blade load measuring system 410 also undergo a corresponding rotational movement. Depending on the position of the first rotor blade 201, different accelerations, forces, and moments act on it. For example, the first rotor blade 201 is in a first position S1 when its blade axis 211 is oriented horizontally, i.e., orthogonally to a longitudinal axis of the tower 101.

[0056] In a first step 501, the first accelerometer 310 measures an initial acceleration in this first position S1. The first accelerometer 310 is arranged in the rotating hub and oriented so that it can measure accelerations along the blade axis 211; optionally, it can measure accelerations in any three mutually orthogonal spatial directions to enable the calculation of the acceleration in the blade axis direction 211; this is referred to below as the first measured acceleration in the z-direction of the first rotor blade. The first accelerometer 310 can further measure two additional accelerations orthogonal to the first measured acceleration in the z-direction or enable their calculation from the acceleration measurements in several spatial directions; these are referred to below as the first measured acceleration in the y-direction and the first measured acceleration in the x-direction of the first rotor blade.

[0057] The acceleration due to gravity at the rotor blade is vectorially distributed depending on the cone angle, the tilt angle, the pitch angle, and the rotor blade position around the rotation axis 200. In the first position S1, the acceleration due to gravity in the z-direction along the blade axis 211 is zero, and the acceleration due to gravity of 9.81 m / s² is distributed only between an acceleration in the y-direction and an acceleration in the x-direction.

[0058] From the manufacture of the first, second and third rotor blades, it is known that the mass M of a rotor blade is 20,000 kg and the center of gravity SP is located along the blade axis 211 of the rotor blade at a distance d SP of 20 m from the blade flange 221.

[0059] In a second step 502, a first reference bending moment M B-1 acceleration sensor of the first rotor blade 201 is determined with respect to the blade flange 221 as the load reference cross-section based on the first measured acceleration. The first reference bending moment of the first rotor blade M B-1 acceleration sensor is 3924 kNm.

[0060] Likewise, in this first position S1, the rotor blade experiences a force and moment effect at the first plane of the rotor blade cross-section, which are detected by the strain sensors of the first blade load measuring system 410. In a third step 503, based on the measurements of the strain sensors and a first set of adjustment parameters assigned to the first blade load measuring system with initial adjustment parameter values, a first measured bending moment M B-1 strain sensor of the first rotor blade 201 is determined with respect to the blade flange 221 as the load reference section. In this case, a first measured bending moment M B-1 strain sensor of 3610 kNm is determined for the first rotor blade.

[0061] In a subsequent step 504, the first reference bending moment M B-1 acceleration sensor is compared with the first measured bending moment M B-1 strain sensor to determine a first deviation A1. In the described embodiment, the first deviation A1 is 8%.

[0062] In a subsequent step 505, based on the first deviation A1, the adjustment parameter values ​​of the first adjustment parameter set KP1 for the first leaf load measuring system are adjusted such that the first deviation A1 is less than or equal to a threshold value. In the described embodiment, the threshold value S is 1%. With a measured bending moment of M B-1 strain sensor of 3904 kNm, the first deviation A1 is 0.5% and is therefore less than the threshold value S, so the adjustment parameter values ​​of the adjustment parameter set KP1 are selected for adjusting the first leaf load measuring system or its strain sensors.

[0063] Figure 4Figure 600 shows a flowchart of a method for adjusting a second blade load measurement system 420 according to the embodiments described herein. The wind turbine has a second rotor blade 202, which is arranged at the hub at an angular offset W of 180° to the first rotor blade 201. In a first step 601, a second acceleration, which is assigned to the second rotor blade, is determined based on the first measured acceleration 311 and the angular offset W between the first and the second rotor blade. The first measured acceleration in the x, y, and z directions is thus converted into a second acceleration in the x, y, and z directions.

[0064] In a second step 602, a second reference bending moment M B-2 acceleration sensor of the second rotor blade 202 is determined from the second acceleration. The second reference bending moment M B-2 acceleration sensor on the second rotor blade is -3924 kNm. The strain sensors of the second blade load measuring system 420 are located near the blade flange, just like the strain sensors of the first blade load measuring system 410.

[0065] In a third step, based on the measurements of the strain sensors of the second blade load measuring system 420 of the second rotor blade and a second set of adjustment parameters assigned to the second blade load measuring system 420 with second initial adjustment parameter values, a second measured bending moment M B-2 strain sensor of the second rotor blade 202 is determined with reference to the load reference section, i.e. the blade flange 221 of the second rotor blade 202.

[0066] In the present case, the second blade load measuring system determines a second measured bending moment M B-2 strain sensor of the second rotor blade of -3010 kNm.

[0067] In a next step 604, the second reference bending moment of the second rotor blade M B-2 acceleration sensor is compared with the second measured bending moment of the second rotor blade M B-2 strain sensor and a second deviation A2 is determined, which in the described embodiment is 23 %.

[0068] In a subsequent step 605, based on the second deviation A2, the adjustment parameter values ​​of the second adjustment parameter set KP2 for the second blade load measuring system 420 are adjusted such that the second deviation A2 is less than or equal to the threshold of 1%. With a second measured bending moment of the second rotor blade from M B-2 strain sensor of -3889 kNm, the second deviation A2 is 0.9% and is therefore less than the threshold S. Consequently, the adjustment parameter values ​​of the second adjustment parameter set KP2 are selected to adjust the second blade load measuring system and its strain sensors on the second rotor blade. Reference symbol list

[0069] 100 Wind turbine 101 Tower 102 Nacelle 103 Hub 200 Rotational axis of the rotor 201 / 202 First / second rotor blade 203 Horizontal center axis of the nacelle 204 Axis in the plane of rotation of the rotor W Angle between the rotor blades about the rotational axis 211 Blade axis 221 Blade flange 231 Blade tip I Length of the rotor blade from the blade flange to the blade tip M Mass of the rotor blade SP Center of gravity of the rotor blade d SP Distance of the center of gravity from the blade flange of the rotor blade e 410 First plane of the rotor blade cross-section of the first rotor blade d 410 Distance of the first blade load measuring system 410 on the first rotor blade from the blade flange S1 First position of the first rotor blade 300 Signal line 310 First accelerometer 330 Evaluation unit 400 Fiber optic cable 410 First blade load measuring system with four strain sensors of the first Rotor blade 420 second blade load measuring system with four strain sensors of the second rotor blade M B-1 acceleration sensor first reference bending moment due toAccelerations at the first rotor blade M B-2 acceleration sensor second reference bending moment due to accelerations at the second rotor blade M B-1 strain sensor first measured bending moment based on measurements from the at least one strain sensor of the first blade load measuring system and a first adjustment parameter set assigned to the first blade load measuring system with first initial adjustment parameter values ​​M B-2 strain sensor second measured bending moment based on measurements from the at least one strain sensor of the second blade load measuring system and a second adjustment parameter set assigned to the second blade load measuring system with second initial adjustment parameter values ​​A1 / A2 first / second deviation S threshold KP1 / KP2 first / second adjustment parameter set for the first / second blade load measuring system of the first / second rotor blade 500 Method for adjusting a first blade load measuring system with at least one strain sensor 501 Measuring of502 Determining a first reference bending moment based on the first measured acceleration of the first rotor blade 503 Determining a first measured bending moment based on measurements from the at least one strain sensor of the first blade load measuring system and a first set of adjustment parameters assigned to the first blade load measuring system with first initial adjustment parameter values ​​504 Determining a first deviation of the first reference bending moment from the first measured bending moment 505 Adjusting the adjustment parameter values ​​of the first set of adjustment parameters for the first blade load measuring system such that the first deviation is less than or equal to a threshold value 600 Method for adjusting a second blade load measuring system with at least one strain sensor 601 Determining a second acceleration assigned to the second rotor blade based on the first measured602 Determine a second reference bending moment based on the second acceleration and an angular offset between the first and a second rotor blade. 603 Determine a second measured bending moment based on measurements from the at least one strain sensor of the second blade load measuring system and a second set of adjustment parameters assigned to the second blade load measuring system with second initial adjustment parameters. 604 Determine a second deviation of the second reference bending moment from the second measured bending moment. 605 Adjust the adjustment parameter values ​​of the second set of adjustment parameters for the second blade load measuring system such that the second deviation is less than or equal to a threshold value.

Claims

1. A computer-implemented method for adjustment of a first blade load measurement system having at least one strain sensor on a first rotor blade of a wind turbine, having the following steps: a) measuring a first acceleration with a first acceleration sensor; b) determining a first reference bending moment and / or a first reference axial force based on the first measured acceleration; c) determining a first measured bending moment and / or a first measured axial force based on measured values from the at least one strain sensor of the first blade load measurement system and a first adjustment parameter set with first initial adjustment parameter values associated with the first blade load measurement system; d) determining a first deviation of the first reference bending moment and / or the first reference axial force from the first measured bending moment and / or the first measured axial force; e) adapting the adjustment parameter values of the first adjustment parameter set for the first blade load measurement system such that the first deviation is less than or equal to a threshold value.

2. The computer-implemented method according to claim 1, characterised in that the method comprises adjusting a second blade load measurement system having at least one strain sensor on a second rotor blade, having the following steps: a) determining a second acceleration associated with the second rotor blade based on the first measured acceleration taking into account an angular offset between the first and a second rotor blade; b) determining a second reference bending moment and / or a second reference axial force based on the second acceleration; c) determining a second measured bending moment and / or a second measured axial force based on measured values from the at least one strain sensor of the second blade load measurement system and a second adjustment parameter set with second initial adjustment parameters associated with the second blade load measurement system; d) determining a second deviation of the second reference bending moment and / or the second reference axial force from the second measured bending moment and / or the second measured axial force; e) adapting the adjustment parameter values of the second adjustment parameter set for the second blade load measurement system such that the second deviation is less than or equal to a threshold value.

3. The computer-implemented method according to claim 1 or 2, characterised in that steps a) to d) are performed repeatedly, in particular for at least 50, more particularly at least 100, more particularly at least 1000, more particularly at least 10000 repetitions, with different pitch angles and / or different accelerations being detected at each repetition, and afterwards in step e), the adjustment parameter values are adapted such that the first or second deviations detected in step d) are less than or equal to a threshold value.

4. The computer-implemented method according to any one of the preceding claims, characterised in that, prior to step a), a pitch angle is applied and / or a defined pitch angle, in particular different pitch angles, is set.

5. The computer-implemented method according to any one of the preceding claims, characterised in that the first measured acceleration is rejected if a wind speed exceeds a wind speed threshold value.

6. The computer-implemented method according to any one of the preceding claims, characterised in that the first acceleration sensor measures accelerations in at least one, in particular two, more particularly three spatial directions and / or is formed by an inertial measurement unit, and / or in that an acceleration sensor, preferably two, more preferably three acceleration sensors, are arranged in the hub of the wind turbine.

7. The computer-implemented method according to any one of the preceding claims, characterised in that the at least one strain sensor of the first or second blade load measurement system is arranged on the first or second rotor blade in a radial range of no more than 50 %, preferably no more than 30 %, of the length of the rotor blade starting from the blade flange.

8. The computer-implemented method according to any one of the preceding claims, characterised in that the adjustment of the first and / or second blade load measurement system on the first and / or second rotor blade is executed by a computing device on site at the wind turbine and / or by a remote computing device.

9. An apparatus for adjustment of a first blade load measurement system having at least one strain sensor on a first rotor blade of a wind turbine, having: - a unit for measuring an acceleration, configured to measure a first acceleration with a first acceleration sensor; - a unit for determining a bending moment and / or an axial force, configured to determine a first reference bending moment and / or a first reference axial force based on the first measured acceleration and a first measured bending moment and / or a first measured axial force based on measured values from the at least one strain sensor of the first blade load measurement system and a first adjustment parameter set with first initial adjustment parameter values associated with the first blade load measurement system; - a unit for determining a deviation of bending moments and axial forces, configured to determine a first deviation of the first reference bending moment and / or the first reference axial force from the first measured bending moment and / or the first measured axial force; - a unit for adapting adjustment parameter values of an adjustment parameter set for a blade load measurement system, configured to adapt adjustment parameter values of the first adjustment parameter set for the first blade load measurement system such that the first deviation is less than or equal to a threshold value.

10. The apparatus according to claim 9, characterised in that the apparatus is suitable for adjustment of a second blade load measurement system having at least one strain sensor on a second rotor blade of a wind turbine, wherein - the unit for measuring an acceleration is configured to determine a second acceleration based on the first measured acceleration and taking into account an angular offset between the first and second rotor blades; - wherein the unit for determining a bending moment and / or an axial force is configured to determine a second reference bending moment and / or a second reference axial force based on the second acceleration and a second measured bending moment and / or a second measured axial force based on measured values from the at least one strain sensor of the second blade load measurement system and a second adjustment parameter set with second initial adjustment parameter values associated with the second blade load measurement system; - wherein the unit for determining a deviation of bending moments and axial forces is configured to determine a second deviation of the second reference bending moment and / or the second reference axial force from the second measured bending moment and / or the second measured axial force; - wherein the unit for adapting adjustment parameter values of an adjustment parameter set for a blade load measurement system is configured to adapt adjustment parameter values of the second adjustment parameter set for the second blade load measurement system such that the second deviation is less than or equal to a threshold value.

11. The apparatus according to any one of claims 9 to 10, further having a pitch angle application and / or setting unit to apply a pitch angle and / or to set a defined pitch angle, in particular different pitch angles.

12. The apparatus according to any one of claims 9 to 11, further having a unit for rejecting an acceleration, configured to compare a wind speed to a wind speed threshold value and to select the first measured acceleration if the wind speed is less than a wind speed threshold value, and to reject the first measured acceleration if the wind speed is greater than a wind speed threshold value.

13. A wind turbine, comprising a rotor with a hub and a rotor blade, extending radially from the hub, wherein the number of rotor blades comprises at least a first rotor blade, characterised in that the wind turbine is provided with an apparatus according to any one of claims 9 to 12.

14. A computer-readable storage medium, containing instructions which cause the apparatus according to any one of claims 9 to 12 to execute the method steps according to any one of claims 1 to 8.