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

Abstract

Blade loads acting on a rotor blade are usually determined taking into account strains acting thereon, which can be detected by strain sensors. To date, strain sensors have been adjusted using a rotor angle. Detection of the rotor angle is, however, often unreliable or inaccurate, and therefore no adequate solution has been found to date for adjusting the strain sensors simply and accurately. According to the invention, the problem is solved by a computer-implemented method for adjusting a first blade load measurement system having at least one strain sensor on a first rotor blade of a wind turbine, the method comprising the following steps: a first acceleration is measured by means of a first acceleration sensor; a first reference bending moment and / or a first reference axial force is / are determined based on the first acceleration measured; a first measured bending moment and / or a first measured axial force is / are determined based on values measured by the at least one strain sensor of the first blade load measurement system and a first adjustment parameter set, containing first initial adjustment parameter values, assigned to the first blade load measurement system; 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 is determined; the adjustment parameter values of the first adjustment parameter set for the first blade load measurement system are adapted such that the first deviation is less than or equal to a threshold value.

Description

[0001] 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

[0002] Description

[0003] Technical area

[0004] The present invention generally relates 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 having at least one rotor blade with a strain sensor and a computer-readable storage medium.

[0005] State of the art

[0006] A wind turbine converts wind energy into electrical energy. The wind exerts a force on at least one blade of the wind turbine's rotor, converting the wind's kinetic energy into the rotor's rotational kinetic energy. The rotor drives an electric generator, which feeds electrical energy into the electricity grid.

[0007] One or more rotor blades of a wind turbine are increasingly being equipped with one or more sensors, e.g. strain sensors, which are used for control purposes, in particular for load reduction, and / or for monitoring turbine operation, in particular for safety and maintenance purposes. The forces and / or moments acting on the rotor blade are determined from the strains measured by the strain sensors. In order to obtain reliable and correct measured values ​​from the strain sensors and thus correct load measurement results, the strain sensors must be adjusted before they are put into operation. This means that a deviation of a measured load value from a target value (a reference) is determined and documented. The adjustment parameters for the strain sensors are then set or adjusted so that any measurement deviation from a target value is as small as possible or lies within a defined specification or tolerance limits.

[0008] To date, the calibration of a strain sensor for blade load measurement requires the mass of the rotor blade, the arrangement of the sensors on that rotor blade, the current rotor angle of the wind turbine's turbine, the current wind speed, and the current pitch angle. The pitch angle and the current rotor angle represent the most important input parameters. The current wind speed is used for a filter mechanism to filter out measurements taken at wind speeds so high that they could distort the measurement results.

[0009] High wind speeds lead to additional moments that make adjustment inaccurate, so filtering improves the adjustment quality of the strain sensor.

[0010] For the actual adjustment, a controlled and defined movement of the rotor blade is carried out, for example several revolutions at low wind speeds. In particular, the pitch angle of the rotor blade is specifically controlled and adjusted differently. Since wind turbines operate with different pitch angles, it is necessary to perform adjustment movements at different pitch angles in order to fully map the behavior of the strain sensors. The rotor blade is brought into defined positions in which known forces or bending moments act on the rotor blade. Defined positions are, for example, positions of the rotor blade perpendicular or parallel to the earth's surface. The position of the rotor blade can be clearly determined by measuring the current rotor angle. This means that a measurement of the rotor angle is absolutely necessary 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 sensors, and the mass of the rotor blade, the bending moments and axial forces acting on the rotor blade are determined. At the same time, the strain sensors record 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 sensors are compared with the known forces and bending moments, and the adjustment parameter set for the strain sensors is adjusted accordingly.

[0011] For example, EP 2 531 722 A1 teaches a method for in-situ adjustment of load sensors of a wind turbine. First, a rotor azimuth angle and an angle of attack of the first wind turbine blade are determined. In a next step, 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 the comparison.

[0012] Problems solved by the invention

[0013] A disadvantage of the described previous method for adjusting a strain sensor is that the current rotor angle of the wind turbine's turbine must be recorded. However, a rotor angle often cannot be measured accurately because an angular offset occurs between the actual and measured rotor angle due to measurement deficiencies. If interference signals occur or the recorded rotor angle signal is unreliable or inaccurate, this impairs the adjustment of the strain sensor.

[0014] Based on this prior art, it is an object of the present invention to overcome the aforementioned disadvantages. A method is needed to adjust strain sensors accurately and reliably, especially without measuring or using a rotor angle. Means for solving the problem

[0015] The object is achieved 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 precise adjustment of the blade load measuring system, and eliminates the need to measure or use a rotor angle in the adjustment process. Furthermore, the object is achieved 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.

[0016] In particular, the object is achieved 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 measured values ​​from the at least one strain sensor of the first blade load measuring system and a first adjustment parameter set with first initial adjustment parameter values ​​assigned to the first blade load measuring 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) adjusting the adjustment parameter values ​​of the first adjustment parameter set for the first blade load measuring system such that the first deviation is less than or equal to a threshold value;

[0017] One idea of ​​the present invention is therefore to adjust a blade load measuring system without using a wind turbine's rotor angle. Adjustment based on accelerations can be suitable for increasing the accuracy of the adjustment.

[0018] A blade load measuring system can be understood in particular as a strain sensor system that comprises at least one strain sensor, in particular a plurality of strain sensors, in particular at least three, further in particular at least four strain sensors. The at least one strain sensor can be designed as a strain sensor that measures one or more strains in one direction. The strain sensor can preferably be positioned and aligned 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 be understood in particular as 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 designed to measure multiple strains in the direction of the blade axis, which are required for determining axial forces and / or bending moments. In particular, if the strain sensor can only measure one strain in the direction of the blade axis, the blade load measuring system can comprise 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, for example, in the first plane, of the rotor blade cross-section, or in multiple spaced-apart planes of the rotor blade cross-section.

[0019] The first acceleration sensor can detect a first acceleration acting in a rotating rotor hub. The first acceleration sensor can, for example, be an acceleration sensor system that measures accelerations in three orthogonal spatial directions. For example, the first acceleration sensor can be provided by a 6-DOF acceleration sensor.

[0020] A first measured acceleration can be understood in particular as an acceleration which comprises acceleration components in several spatial directions, in particular in three, in particular orthogonal, spatial directions.

[0021] 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 first reference bending moment and / or the first reference axial force is determined, in particular, without taking the rotor angle into account.

[0022] Whether the first measured bending moment and / or the first measured axial force are taken into account for the adjustment can depend, in particular, on the number of strain sensors. For example, if three strain sensors are used, the first measured axial force can be taken into account. If four strain sensors are used, the first measured bending moment or, alternatively, the first measured axial force and the first measured bending moment can be used.

[0023] 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.

[0024] 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 and the first measured bending moment and / or the first measured axial force can be determined.

[0025] Based on the first deviation, the adjustment parameter values ​​of the first adjustment parameter set are determined such that the first deviation is less than or equal to a threshold value. If the first 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 value can specify a first deviation of at most 5.00%, preferably at most 3.00%, more preferably at most 1.00%.

[0026] The first adjustment parameter set of the first blade load measuring system can comprise one or more suitable parameters for adjusting the first blade load measuring system or the strain sensor. The initial adjustment parameter values ​​of the first adjustment parameter set can be any specified parameter values. The computing time can be shortened if suitable adjustment parameter values ​​are specified as initial adjustment parameter values. For example, adjustment parameter values, in particular initial ones, of an adjustment parameter set from a structurally and functionally similar wind turbine can be used. Optionally, adjustment parameter values, in particular initial ones, can be used that are determined from a stiffness of the first rotor blade and / or a position of the first strain sensor and / or a wavelength of the first strain sensor.

[0027] 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 orthogonal to the load reference plane can be determined.

[0028] The first axial force can specify a force that acts from the hub center along the blade axis towards the blade tip. In addition, 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. Furthermore, a first bending moment can be determined based on the weight force and a distance of the center of gravity of the rotor blade 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 rotor blade in a step of rotor blade production or before assembly of the first rotor blade. This has the advantage that a first bending moment and / or a first axial force related to the blade flange can be easily determined solely from the mass of the first rotor blade, the distance of the center of gravity from the blade flange, and the first measured acceleration.Furthermore, a design mass distribution can be used to determine the center of gravity and mass relative to each blade radius position and thus to adjust bending moments and / or axial forces relative to this blade section.

[0029] As already described, the wind turbine can comprise at least a first rotor blade. Furthermore, the wind turbine can comprise a plurality of, in particular two, further in particular three, rotor blades. The rotor blades can each be arranged uniformly around the hub at an angular offset from one another. If, for example, two rotor blades are provided, these can be arranged at an angular offset of 180° from one another. If, for example, three rotor blades are provided, these 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 regard to their dimensions, their mass, their mass distribution and their center of gravity and thus their static moment, i.e. the product of mass and the distance of the center of gravity from a reference point. The deviation is preferably at most 5%, preferably at most 2%, further preferably 1%.

[0030] In an advantageous embodiment, the method may comprise 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 measured values ​​from the at least one strain sensor of the second blade load measuring system and a second adjustment parameter set associated with the second blade load measuring 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 blade load measuring system such that the second deviation is less than or equal to a threshold value;

[0031] 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 a second rotor blade. 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 generally related to the blade flange, but can also be related to any other position on the second rotor blade. At least one second blade load measuring 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 same conditions apply to the type and positioning of the second strain sensor as to the at least one strain sensor of the first blade load measuring system on the first rotor blade.

[0032] 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.

[0033] 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. The threshold for the second deviation can, in particular, correspond to the threshold for the first deviation.

[0034] By only measuring a first acceleration with a first acceleration sensor, the blade load measuring 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.

[0035] The second adjustment parameter set of the second blade load measuring system can comprise one or more suitable parameters for adjusting the second blade load measuring system or strain sensor. The initial adjustment parameter values ​​of the second adjustment parameter set can be any specified parameter values. The computing time can be shortened if suitable adjustment parameter values ​​are specified as initial adjustment parameter values. For example, adjustment parameter values, in particular initial ones, of an adjustment parameter set from a structurally and functionally similar wind turbine can be used. Optionally, adjustment parameter values, in particular initial ones, can be used that are determined from a stiffness of the second rotor blade and / or a position of the second strain sensor and / or a wavelength of the second strain sensor.

[0036] In an advantageous embodiment, steps a) to d) can be carried out repeatedly, in particular at least 50, further in particular at least 100, further in particular at least 1000, further in particular at least 10,000 repetitions, and instead of step e), the adjustment parameter values ​​can be adjusted such that the first and second deviations detected in step d) are less than or equal to a threshold value, wherein different pitch angles and / or different accelerations are detected in each repetition.

[0037] For example, steps a) to d) can be carried out a predetermined number of times or for a predetermined period of time. Both the period of time and the number of repetitions of steps a) to d) are fundamentally unlimited. To increase the accuracy of the adjustment, the period of time 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 period of time and / or the number of repetitions of steps a) to d) can be limited to a maximum value. Likewise, the period of time and / or the number of repetitions of steps a) to d) can be interrupted and continued at a different time. This has the advantage that the adjustment process can be interrupted if, due to external environmental influences, operation of the wind turbine for the purpose of adjustment cannot be carried out safely.The total time period can, for example, be 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 period or the number of repetitions of steps a) to d) can be determined in particular as a function of how frequently a first measured acceleration is rejected. The first and second deviations determined in step d) can, for example, be combined to form 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 quantity 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 adjustment to be made at a later time, depending on the predetermined time period or the predetermined number of runs.

[0038] In an advantageous embodiment, a pitch angle can be used before step a) and / or a defined pitch angle, in particular different pitch angles, can be set. For example, pitch angle signals that are detected by the wind turbine as standard can be used. A wind turbine is typically operated at different pitch angles. By setting a defined pitch angle, in particular by setting different pitch angles, the first rotor blade can be brought into an aerodynamically favorable position in terms of energy efficiency and safety at any time, so that the rotor of the wind turbine always operates reliably at the optimal operating point. Furthermore, by determining the pitch angle, a critical operating state of the wind turbine can be identified.By setting a defined pitch angle, damage to the wind turbine can be avoided during the calibration of the first blade load sensor.

[0039] In an advantageous embodiment, the first acceleration measured by the first acceleration sensor can be discarded if a wind speed exceeds a wind speed threshold. The wind speed prevailing in the vicinity of the wind turbine can be measured using wind speed sensors that can be arranged on or near the wind turbine. The measured wind speed can be compared with a specified wind speed threshold for a maximum wind speed. If the measured current wind speed is lower than the wind speed threshold for the maximum wind speed, the first measured acceleration can be used for further adjustment of the blade load measuring 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 by wind forces and thus distorted. 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, more preferably 3 m / s.

[0040] 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 formed by an inertial measuring unit and / or an acceleration sensor, preferably two, further preferably three acceleration sensors can be arranged in the hub of the wind turbine.

[0041] The first acceleration sensor 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-direction, y-direction, and z-direction. By using more than one first acceleration sensor, the measuring system can be designed to be functionally redundant so that if one acceleration sensor fails, the other acceleration sensors can take over the measuring function. For this purpose, the acceleration sensors are functionally and structurally identical.In addition, the accuracy of the measurement can be increased by comparing the measured values ​​of the individual acceleration sensors in order to identify differences and thus possible measurement errors and to obtain a correct measured value.

[0042] In particular, the first acceleration sensor can be arranged in the hub of the rotor. In particular, the first acceleration sensor can be oriented such that it can measure an acceleration in the direction of a blade axis of the first rotor blade. The first acceleration sensor can also measure two additional accelerations orthogonal to the first measured acceleration.

[0043] In each rotor blade position, different forces and moments can act on the rotor blade, which must be correctly recorded by the blade load measuring system. It may therefore be necessary to determine the acceleration uniquely assigned to a rotor blade position using the first acceleration sensor. The first measured acceleration can be assigned to a first rotor blade position of the first rotor blade. The second measured acceleration can be assigned to a second rotor blade position of the second rotor blade, wherein the second rotor blade can be arranged around the hub at an angular offset from the first rotor blade. A plurality of rotor blade positions can be assigned to a measured acceleration. An acceleration assigned to a rotor blade position can, for example, be specified using an acceleration vector, wherein 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.

[0044] If the first acceleration sensor is offset from the blade axis by a mounting offset, e.g. a translational or rotational displacement, in particular by an angular offset, the acceleration sensor measures different accelerations. The precise positioning and alignment of the acceleration sensor 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 falsified due to a mounting offset. 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 offset and take it into account when adjusting the blade load measuring system in order to increase the accuracy of the adjustment.

[0045] The strain sensor can be any suitable sensor, such as a piezoelectric strain gauge or a fiber Bragg grating graphene, to measure strains with or without temperature compensation. Depending on the application, it may be necessary to place the strain sensor at a specific position 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.

[0046] 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 region of at most 50%, preferably at most 30%, of the length of the rotor blade, starting from the blade flange. This allows the determination of the first or second measured bending moment and / or the first or second measured axial force and thus the accuracy of the adjustment to be further increased. 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 carried out by a computing device on the wind turbine on site and / or by a remote computing device. Depending on the application, adjustment by a computing device on the wind turbine on site or by a remote computing device may be expedient.A computing device on site at the wind turbine can be suitable, for example in offshore wind turbines, for carrying out the adjustment of the blade load measuring system on site. A remote computing device may be desired, for example, to make corrections to the adjustment process or to monitor the adjustment process. If the adjustment is carried out by a remote computing device, a unit for storing measurement data and for wirelessly or wired transport of the measurement data to the remote computing unit is particularly advantageous. The computing device can be part of the blade load measuring system. The computing device can consist of one or more computing units. Furthermore, the adjustment of the first or second blade load measuring system can be carried out by a common, i.e. the same, computing device or by different computing devices.

[0047] The object mentioned at the outset is further achieved 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 device has the following:

[0048] - unit for measuring an acceleration, which is designed to measure a first acceleration with a first acceleration sensor;

[0049] - Unit for determining a bending moment and / or an axial force, which is designed 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 measured values ​​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;

[0050] - Unit for determining a deviation of bending moments and axial forces, which is designed 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;

[0051] - A unit for adapting adjustment parameter values ​​of an adjustment parameter set for a blade load measuring system, which unit is configured to adapt adjustment parameter values ​​of the first adjustment parameter set for the first blade load measuring system such that the first deviation is less than or equal to a threshold value. The device described herein can be used, in particular, using the method described herein for adjusting a first blade load measuring system with at least one strain sensor, or the method can be implemented by the device described. In this respect, the modifications and developments described with regard to the method are also applicable to the device.

[0052] 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

[0053] - the unit for measuring an acceleration is designed 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;

[0054] - wherein the unit for determining a bending moment and / or an axial force is designed 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 measured values ​​from the at least one strain sensor of the second blade load measuring system and a second adjustment parameter set with second initial adjustment parameter values ​​assigned to the second blade load measuring system;

[0055] - wherein the unit for determining a deviation of bending moments and axial forces is designed 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;

[0056] - wherein the unit for adapting adjustment parameter values ​​of an adjustment parameter set for a blade load measuring system is designed to adapt 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.

[0057] In an advantageous embodiment, the device may further comprise a pitch angle use and / or setting unit to use a pitch angle and / or to set a defined pitch angle, in particular different pitch angles.

[0058] In an advantageous embodiment, the device may further comprise an acceleration discarding unit 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 discard the first measured acceleration if the wind speed is greater than a wind speed threshold.

[0059] The object is further achieved 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 comprises at least a first rotor blade, and the wind turbine is provided with a device as described above.

[0060] Similar or identical advantages arise as already described in connection with the method described above.

[0061] The object is further achieved in particular by a computer-readable storage medium which contains instructions which cause at least one processor to implement a method as described above when the instructions are executed by the at least one processor.

[0062] Similar or identical advantages arise as already described in connection with the method described above.

[0063] Further embodiments emerge from the subclaims.

[0064] Short description of the drawings

[0065] The invention is explained in more detail below using exemplary embodiments. In the following, the following are shown:

[0066] 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;

[0067] 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.

[0068] 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.

[0069] Description of the execution form(s)

[0070] Embodiments of the invention are explained below. In the drawings, like reference numerals designate the same or similar features of the respective embodiments.

[0071] Figure 1 shows a schematic side view of a wind turbine 100 with a first 201, second 202 and third (not shown here) rotor blade according to embodiments described herein. The wind turbine 100 includes 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, 202 are attached. According to typical embodiments, the rotor has at least one, preferably two rotor blades, more preferably three rotor blades. 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 a hub center. The gondola 102 or its central axis 200 is inclined by a tilt angle o of eight degrees relative to a horizontal alignment of the gondola with respect to a flat, horizontal earth surface, ie a horizontal central axis 203.An axis 211 runs along a longitudinal extension of each rotor blade 201, 202. The rotor blades 201, 202, or their respective axes 211, are inclined away from the tower by a cone angle ß of four degrees with respect to an axis 204 in a rotational plane of the rotor or perpendicular to the central axis 200. This drives a generator to generate electricity.

[0072] As shown in Figure 1, at least a 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.

[0073] Furthermore, Figure 1 shows a first blade load measuring system 410 comprising four strain sensors 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 via a light guide 400, for example, an optical fiber.

[0074] Figure 2 shows a schematic side view of the first rotor blade 201 according to embodiments described herein. The length I of the rotor blade 201 extends from a blade flange 221 to a blade tip 231. Figure 2 also illustrates the center of gravity SP and its distance dsp from the blade flange of the rotor blade. Furthermore, Figure 2 shows the positioning of the first blade load measuring system 410 on the first rotor blade at a distance d4io 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 e4io of a rotor blade cross-section, so that only bending moments are required for adjustment.

[0075] Figure 3 shows a flowchart of a method 500 for adjusting the first blade load measuring system 410 or its strain sensors according to the embodiment described herein. Upon rotation of the rotor and thus of the first rotor blade 201 about the rotation axis 200, the first acceleration sensor 310 and the strain sensors of the first blade load measuring system 410 also experience a corresponding rotational movement. Depending on the position of the first rotor blade 201, different accelerations, forces, and moments act on the first rotor blade. 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.

[0076] In a first step 501, the first acceleration sensor 310 measures a first acceleration in this first position S1. The first acceleration sensor 310 is arranged in the rotating hub and aligned such 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 acceleration sensor 310 can further measure two further accelerations orthogonal to the first measured acceleration in the z-direction or enable their calculation from the acceleration measurements from multiple 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.

[0077] The earth's gravitational acceleration at the rotor blade is distributed vectorially 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 earth's gravitational acceleration in the z-direction along the blade axis 211 is zero and the gravitational acceleration of 9.81 m / s 2 is simply divided into an acceleration in the y-direction and an acceleration in the x-direction.

[0078] From the production 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 dsp of 20 m from the blade flange 221.

[0079] In a second step 502, a first reference bending moment M B -i- BeSThe bending moment of the first rotor blade 201 relative to the blade flange 221 is determined as a load reference cross-section based on the first measured acceleration. The first reference bending moment of the first rotor blade M B -i- BeS chieu nigungssensor is 3924 kNm.

[0080] Likewise, the rotor blade experiences a force and moment effect at the first plane of the rotor blade cross-section in this first position S1, 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 adjustment parameter set assigned to the first blade load measuring system with first initial adjustment parameter values, a first measured bending moment M B -i strain sensor of the first rotor blade 201 relative to the blade flange 221 as a load reference section. In this case, a first measured bending moment M B-i strain sensor for the first rotor blade of 3610 kNm. In a next step 504, the first reference bending moment M B -i- BeS The bending moment M measured by the bending moment sensor is compared with the first measured bending moment M measured by the bending moment sensor to determine a first deviation Al. In the described embodiment, the first deviation Al is 8%.

[0081] In a next step 505, based on the first deviation Al, the adjustment parameter values ​​of the first adjustment parameter set KP1 for the first blade load measuring system are adjusted such that the first deviation Al 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 Bl strain sensor of 3904 kNm, the first deviation Al is 0.5% and is thus less than the threshold value S, so that the adjustment parameter values ​​of the adjustment parameter set KP1 are selected for adjusting the first blade load measuring system or its strain sensors.

[0082] Figure 4 shows a flowchart of a method 600 for adjusting a second blade load measuring system 420 according to embodiments described herein. The wind turbine has a second rotor blade 202 arranged on the hub at an angular offset W of 180° from the first rotor blade 201. In a first step 601, a second acceleration associated with the second rotor blade is determined based on the first measured acceleration 311 and the angular offset W between the first and second rotor blades. The first measured acceleration in the x, y, and z directions is therefore converted into a second acceleration in the x, y, and z directions.

[0083] In a second step 602, a second reference bending moment M B-2.BeS The acceleration sensor of the second rotor blade 202 determines the second acceleration. The second reference bending moment M B-2.BeSThe strain sensor on the second rotor blade is -3924 kNm. The strain sensors of the second blade load measuring system 420, like the strain sensors of the first blade load measuring system 410, are located near the blade flange.

[0084] 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 adjustment parameter set with second initial adjustment parameter values ​​assigned to the second blade load measuring system 420, a second measured bending moment M B-2 -strain sensor of the second rotor blade 202 relative to the load reference section, ie, the blade flange 221 of the second rotor blade 202. 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.

[0085] In a next step 604, the second reference bending moment of the second rotor blade M B-2.BeS chieu nigungssensor with the second measured bending moment of the second rotor blade M B-2-De voltage sensor and a second deviation A2 is determined, which in the described embodiment is 23%.

[0086] In a next 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 value of 1%. For a second measured bending moment of the second rotor blade of M B-2-Deh strain sensor of -3889 kNm, the second deviation A2 is 0.9% and is thus smaller than the threshold value S, which is why the adjustment parameter values ​​of the second adjustment parameter set KP2 are selected for adjusting the second blade load measuring system or its strain sensors on the second rotor blade.

[0087] List of reference symbols

[0088] 100 wind turbines

[0089] 101 Tower

[0090] 102 gondolas

[0091] 103 Hub

[0092] 200 Rotation axis of the rotor

[0093] 201 / 202 first / second rotor blade

[0094] 203 horizontal center axis of the gondola

[0095] 204 Axis in the rotation plane of the rotor

[0096] W Angle between the rotor blades around the rotation axis

[0097] 211 Leaf axis

[0098] 221 blade flange

[0099] 231 leaf tip

[0100] I Length of the rotor blade from the blade flange to the blade tip

[0101] M Mass of the rotor blade

[0102] SP Center of gravity of the rotor blade d S p Distance of the center of gravity from the blade flange of the rotor blade e4io first plane of the rotor blade cross section of the first rotor blade d4io Distance of the first blade load measuring system 410 on the first

[0103] Rotor blade from the blade flange

[0104] S1 first position of the first rotor blade

[0105] 300 signal line

[0106] 310 first acceleration sensor

[0107] 330 evaluation unit

[0108] 400 light guides

[0109] 410 first blade load measuring system with four strain sensors of the first rotor blade

[0110] 420 second blade load measuring system with four strain sensors of the second rotor blade

[0111] Mß-i-ßeschieunigugssensor first reference bending moment due to accelerations on the first rotor blade

[0112] Mß-2 acceleration sensor second reference bending moment due to accelerations on the second rotor blade

[0113] Mß-l strain sensor first measured bending moment based on measured values ​​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

[0114] Mß-2 strain sensor second measured bending moment based on measured values ​​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

[0115] A1 / A2 first / second deviation

[0116] S threshold

[0117] KP1 / KP2 first / second adjustment parameter set for the first / second

[0118] Blade load measuring system of the first / second rotor blade

[0119] 500 Method for adjusting a first blade load measuring system with at least one strain sensor

[0120] 501 Measuring a first acceleration with a first acceleration sensor

[0121] 502 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 measured values ​​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

[0122] 504 Determining a first deviation of the first reference bending moment from the first measured bending moment

[0123] 505 Adjusting the adjustment parameter values ​​of the first adjustment parameter set for the first blade load measuring system such that the first deviation is less than or equal to a threshold value

[0124] 600 Method for adjusting a second blade load measuring system with at least one strain sensor

[0125] 601 Determining a second acceleration associated with the second rotor blade based on the first measured acceleration and an angular offset between the first and a second rotor blade

[0126] 602 Determining a second reference bending moment based on the second acceleration of the second rotor blade

[0127] 603 Determining a second measured bending moment based on measured values ​​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 parameters

[0128] 604 Determining a second deviation of the second reference bending moment from the second measured bending moment

[0129] 605 Adjusting the 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

Claims

Patent claims 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 measured values ​​from the at least one strain sensor of the first blade load measuring system and a first adjustment parameter set with first initial adjustment parameter values ​​assigned to the first blade load measuring 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) adjusting the adjustment parameter values ​​of the first adjustment parameter set for the first blade load measuring system such that the first deviation is less than or equal to a threshold value. The computer-implemented method according to claim 1, characterized in that the method comprises 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 measured values ​​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 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 blade load measuring system such that the second deviation is less than or equal to a threshold value.Computer-implemented method according to claim 1 or 2, characterized in that steps a) to d) are carried out repeatedly, in particular at least 50, further in particular at least 100, further in particular at least 1000, further in particular at least 10,000 repetitions, and instead of step e), the adjustment parameter values ​​are adjusted such that the first and second deviations detected in step d) are less than or equal to a threshold value, wherein different pitch angles and / or different accelerations are detected with each repetition. Computer-implemented method according to one of the preceding claims, characterized in that before step a), a pitch angle is used and / or a defined pitch angle, in particular different pitch angles, are set.Computer-implemented method according to one of the preceding claims, characterized in that the first measured acceleration is discarded if a wind speed exceeds a wind speed threshold. Computer-implemented method according to one of the preceding claims, characterized in that the first acceleration sensor divides accelerations into at least one, in particular two, further categories. in particular measures three spatial directions and / or is formed by an inertial measuring unit and / or that an acceleration sensor, preferably two, more preferably three acceleration sensors is arranged in the hub of the wind turbine. Computer-implemented method according to one of the preceding claims, characterized in that the at least one strain sensor of the first or second blade load measuring system is arranged on the first or second rotor blade in a radial region of at most 50%, preferably at most 30%, of the length of the rotor blade, starting from the blade flange. Computer-implemented method according to one of the preceding claims, characterized in that the adjustment of the first and / or second blade load measuring system on the first and / or second rotor blade is carried out by a computing device on the wind turbine on site and / or by a remote computing device.Device for adjusting a first blade load measuring system with at least one strain sensor on a first rotor blade of a wind turbine, comprising:. - unit for measuring an acceleration, which is designed to measure a first acceleration with a first acceleration sensor; - Unit for determining a bending moment and / or an axial force, which is designed 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 measured values ​​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; - Unit for determining a deviation of bending moments and axial forces, which is designed to determine a first deviation of the first reference bending moment and / or the first reference to determine axial force from the first measured bending moment and / or the first measured axial force; - Unit for adjusting adjustment parameter values ​​of an adjustment parameter set for a blade load measuring system, which is designed to adjust adjustment parameter values ​​of the first adjustment parameter set for the first blade load measuring system such that the first deviation is less than or equal to a threshold value. Device according to claim 9, characterized in that the device is 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 designed 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 designed 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 measured values ​​from the at least one strain sensor of the second blade load measuring system and a second adjustment parameter set with second initial adjustment parameter values ​​assigned to the second blade load measuring system; - wherein the unit for determining a deviation of bending moments and axial forces is designed 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 measuring system is designed to adapt 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. Device according to one of claims 9 to 10, further comprising a pitch angle usage and / or setting unit for using a pitch angle and / or setting a defined pitch angle, in particular different pitch angles. Device according to one of claims 9 to 11, further comprising a unit for discarding an acceleration, which is designed to compare a wind speed with 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 discard the first measured acceleration if the wind speed is greater than a wind speed threshold value.A wind turbine characterized by a rotor having 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 provided with a device according to any one of claims 9 to 12. A computer-readable storage medium containing instructions causing at least one processor to implement a method according to any one of claims 1 to 8 when the instructions are executed by the at least one processor.

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