Wind turbine blade torsion measurement system

Abstract

In a first aspect, a wind turbine blade torsion measurement system is provided. A wind turbine blade torsion measurement system includes a shaft, a rotation sensor assembly, and a connection structure. The connection structure is configured to movably connect the rotation sensor assembly to the blade structure to allow relative movement between the rotation sensor assembly and the blade structure in a direction substantially parallel to a spanwise direction of the wind turbine blade. In another aspect, a wind turbine blade comprising one or more wind turbine blade torsion measurement systems is provided. In yet another aspect, a method of determining torsional deformation of the wind turbine blade is provided. In yet another aspect, a method for installing a wind turbine blade twist measurement system in a wind turbine blade is provided.

Description

Technical Field

[0001] The present disclosure relates to a wind turbine blade twist measurement system, a wind turbine blade having a wind turbine blade twist measurement system, a method for determining the twist of a wind turbine blade, and a method for installing a wind turbine blade twist measurement system in a wind turbine blade. Background Art

[0002] Modern wind turbines are generally used to supply power to the power grid. This type of wind turbine generally includes a rotor having a rotor hub and a plurality of blades. The rotor rotates under the action of the wind on the blades. The rotation of the rotor shaft directly ("directly driven") or drives the generator rotor by using a gearbox. The gearbox (if any), the generator, and other systems are generally installed in a nacelle on top of a wind turbine tower.

[0003] An auxiliary system commonly provided on a wind turbine is a pitch system. The pitch system is used to adapt the position of the wind turbine blade to changing wind conditions. The pitch system generally includes a pitch bearing, which includes an outer ring, an inner ring, and one or more rows of rolling elements between the two rings. The rolling elements allow the two rings to rotate relative to each other.

[0004] The wind turbine blade can be attached to the inner ring or the outer ring, while the hub is connected to the other of the rings. When the pitch system is actuated, the blade can perform a relative rotational movement with respect to the hub. Therefore, the inner ring of the bearing can perform a rotational movement with respect to the outer ring of the bearing.

[0005] The wind turbine blade has a root portion for attachment to the rotor hub (via a pitch bearing) and a tip portion at the opposite end. The root portion of the wind turbine blade generally has a substantially circular cross-section. Some other regions (such as the profile portion or airfoil portion farthest from the rotor hub) have a cross-section with an aerodynamic profile. The aerodynamic cross-section forming the aerodynamic profile can be twisted towards the tip, that is, the angle of the profile chord changes towards the tip. Therefore, the angle of attack at different aerodynamic cross-sections can vary along the length of the wind turbine blade. Therefore, the relative wind speed experienced by the wind turbine blade at different aerodynamic cross-sections depends on the angle of attack.

[0006] Since the pressure loads caused by the wind experienced by a wind turbine blade do not act at the same location in profile under all conditions, the blade is subjected to torsional loads. These torsional loads can cause torsional deformation of the blade or induced warping deformation. The torsional or warping deformation of the blade changes the angle of the profile chord along the length of the blade, and thereby changes the load on the blade. Accordingly, the aerodynamic performance of the blade can be adversely affected. This can result in a reduction in power generation. In addition, the torsional deformation of the blade can increase the noise generated by the wind turbine. Additionally, large wind turbines are generally subject to greater torsional or warping deformation, which can also mean that it is challenging to operate them in a stable manner without the blade and the entire turbine oscillating.

[0007] Strain gauges can be used to measure the torsional deformation of the blade. However, the measurements provided by these strain gauges may not be accurate and are highly dependent on the bending of the blade. Calibrating these strain gauges for different load cases to determine torsion is also time-consuming and difficult.

[0008] Alternatively, a camera can be used to detect the angular position of the blade by detecting markers arranged on the blade. However, these markers are not visible depending on the angle of the wind turbine blade. For example, due to the bending of the blade, markers arranged on the suction side of the blade are not always visible from a camera arranged at the blade root, tower, or nacelle. Dust or fog and clouds can also affect visibility. Accordingly, these types of systems can only be used at specific times. Also, the processing of the images may not be feasible in real time, but rather is a post-processing step with significant time delay.

[0009] Rotation sensors for measuring the rotation of the blade relative to a reference element have also been proposed. However, the reference element and / or support of the rotation sensor can be highly dependent on the bending deformation of the blade. The reference element can also be subject to axial deformation, such as due to thermal expansion or bending. These bending and axial deformations can cause the rotation sensor to provide measurement errors. Additionally, it can be difficult to install these systems inside a wind turbine blade.

[0010] The present disclosure provides examples of systems and methods that at least partially address some of the above disadvantages. SUMMARY OF THE INVENTION

[0011] In a first aspect, a wind turbine blade twist measurement system is provided. The wind turbine blade twist measurement system includes a shaft configured to be arranged in a direction substantially parallel to the spanwise direction of the wind turbine blade. The shaft includes a first shaft portion configured to be coupled to the blade structure of the wind turbine blade. The wind turbine blade twist measurement system further includes a rotational sensor assembly having a rotating member rigidly connected to the first shaft portion, a stationary member rotatably connected to the rotating member, and a sensor for determining the rotational movement of the rotating member relative to the stationary member. Additionally, the wind turbine blade twist measurement system includes a connection structure configured to movably connect the rotational sensor assembly to the blade structure to allow relative movement between the rotational sensor assembly and the blade structure in a direction substantially parallel to the spanwise direction of the wind turbine blade.

[0012] In the present disclosure, the movable connection between the rotational sensor assembly and the blade structure should be understood as a connection that allows relative movement between the rotational sensor assembly and the blade structure in a direction substantially parallel to the spanwise direction of the wind turbine blade. The movable connection may include a slidable connection or a flexible connection along the spanwise direction of the wind turbine blade.

[0013] According to this aspect, axial movement (i.e., movement substantially parallel to the spanwise direction of the wind turbine blade) and changes in the position of the shaft relative to the wind turbine blade can be compensated for by the connection structure. For example, these axial movements and position changes of the shaft may be caused by the bending of the blade and / or by thermal deformation. These phenomena are generally more pronounced in large wind turbine blades because they are subjected to greater loads, are relatively more flexible, and are longer. Thus, according to this aspect, the negative impact of the bending deformation experienced by the wind turbine blade on the twist measurement accuracy can be reduced. The relative changes in the structural performance between the wind turbine blade and the shaft can be absorbed and compensated for by the connection structure.

[0014] Additionally, the load applied to the rotational sensor is reduced. Thus, the expected lifespan of the measurement system can be increased. Furthermore, since the deformation is at least partially compensated for, the wind turbine blade twist measurement system can be arranged outside the blade direction and / or the edge neutral axis. This expands the installation possibilities of the wind turbine blade twist measurement system while maintaining the accuracy of the measurement.

[0015] In another aspect, a wind turbine blade is provided that includes one or more wind turbine blade twist measurement systems according to any of the examples disclosed herein.

[0016] In yet another aspect, a method of determining the torsional deformation of a wind turbine blade according to any of the examples disclosed herein is provided. The method includes determining a rotational movement of a rotating member relative to a stationary member of a corresponding rotational sensor assembly and outputting a signal indicative of the determined rotational movement to a controller or a data acquisition system.

[0017] In yet another aspect, a method of installing a wind turbine blade torsion measurement system in a wind turbine blade is provided. The method includes connecting a rotational sensor assembly to a connection structure and rigidly connecting a rotating member of the rotational sensor assembly to a first shaft portion. The method further includes inserting the shaft into the wind turbine blade and connecting the connection structure to the blade structure.

[0018] Advantages obtained from these aspects may be similar to the advantages mentioned with respect to the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Non-limiting examples of the present disclosure will be described below with reference to the accompanying drawings, in which: Figure 1 A perspective view of a wind turbine according to one example is shown; Figure 2 A simplified internal view of a nacelle of a wind turbine according to one example is shown; Figure 3 A perspective view of a wind turbine blade according to one example is shown; Figure 4 Shows Figure 3 A cross-sectional view of the wind turbine blade of Figure 5 Schematically presents a wind turbine blade torsion measurement system according to an example of the present disclosure; Figure 6 Schematically presents a wind turbine blade torsion measurement system according to an example of the present disclosure; Figures 7a - 7f schematically present examples of a rotational sensor assembly and a connection structure according to the present disclosure; Figure 8 Schematically presents a sensor board according to any of the examples disclosed herein; Figure 9 Schematically presents a wind turbine blade torsion measurement system according to an example of the present disclosure; Figures 10a to 10d schematically present examples of a wind turbine blade having a plurality of wind turbine blade torsion measurement systems according to the present disclosure; Figure 11 Is a block diagram of a method of determining the torsional deformation of a wind turbine blade including one or more wind turbine blade torsion measurement systems according to an example of the present disclosure; and Figure 12 is a block diagram of a method for installing a wind turbine blade twist measurement system in a wind turbine blade according to an example of the present disclosure. Detailed implementation

[0020] In these figures, the same reference numerals are used to denote matching elements.

[0021] Figure 1 A perspective view of an example of a wind turbine 1 is shown. As shown, the wind turbine 1 includes a tower 2 extending from a support surface 3, a nacelle 4 mounted on the tower 2, and a rotor 5 coupled to the nacelle 4. The rotor 5 includes a rotatable hub 6 and at least one wind turbine blade 7 coupled to and extending outwardly from the rotor hub 6. For example, in the illustrated example, the rotor 5 includes three wind turbine blades 7. However, in alternative embodiments, the rotor 5 may include more or fewer than three blades 7. Each wind turbine blade 7 may be spaced from the rotor hub 6 to facilitate rotation of the rotor 5 such that kinetic energy can be converted from the wind into useful mechanical energy and subsequently into electrical energy. For example, the rotor hub 6 may be rotatably coupled to a generator 10 ( Figure 2 ) located within or forming part of the nacelle 4 to permit the generation of electrical energy.

[0022] Figure 2 Shows Figure 1 A simplified internal view of an example of the nacelle 4 of the wind turbine 1. As shown, the generator 10 may be disposed within the nacelle 4. Generally, the generator 10 may be coupled to the rotor 5 of the wind turbine 1 to utilize the rotational energy generated by the rotor 5 to generate electrical power. For example, the rotor 5 may include a main rotor shaft 8 coupled to the hub 6 to rotate therewith. Then, the generator 10 may be coupled to the rotor shaft 8 such that rotation of the rotor shaft 8 drives the generator 10. For example, in this figure, the generator 10 includes a generator shaft 11 rotatably coupled to the rotor shaft 8 via a gearbox 9. In other examples, the generator may be directly coupled to the rotor hub or rotor shaft.

[0023] It should be appreciated that the rotor shaft 8, the gearbox 9, and the generator 10 may be generally supported within the nacelle 4 by a platen or support frame 12 located at the top of the tower 2.

[0024] The nacelle 4 is rotatably coupled to the tower 2 by a yaw system 20. The yaw system includes a yaw bearing (in Figure 2(not visible in the figure), the yaw bearing has two bearing members configured to rotate relative to each other. The tower 2 is connected to one of the bearing members, and the bedplate or support frame 12 of the nacelle 4 is connected to the other bearing member. The yaw system 20 includes a yaw ring gear 21 and a plurality of yaw drives 22. The yaw drives 22 have an electric motor, a gearbox, and pinions for meshing with the ring gear to rotate one of the bearing members relative to the other bearing member.

[0025] The blade 7 is connected to the rotor hub 6 by means of a pitch bearing 31 located between the blade 7 and the rotor hub 6. The pitch bearing 31 includes an inner ring and an outer ring (shown). The wind turbine blade can be attached to the inner bearing ring or the outer bearing ring, while the hub is connected to the other. When the pitch system 30 is actuated, the blade 7 can perform a relative rotational movement with respect to the rotor hub 6. Thus, the inner bearing ring can perform a rotational movement with respect to the outer bearing ring. Figure 2 The pitch system 30 includes a pinion 32 that meshes with a pitch ring gear 33 provided on the inner bearing ring to rotate the wind turbine blade.

[0026] Figure 3 An example of a wind turbine blade 7 is shown. The wind turbine blade 7 extends from the blade root end 71 to the blade tip end 72 in the longitudinal direction or spanwise direction 37. The blade 7 includes a blade root region or portion 50 closest to the rotor hub, a profile portion or airfoil portion 52 furthest from the rotor hub, and a transition portion 51 between the blade root portion 50 and the airfoil portion 52. The blade 7 includes a leading edge 53 that faces the rotational direction of the blade 7 when mounted on the rotor hub, and a trailing edge 54 that faces the opposite direction of the leading edge 53.

[0027] In the examples disclosed herein, the length of the wind turbine blade 7 from the blade root end 71 to the blade tip end 72 is more than 80 meters, for example more than 100 meters. However, wind turbine blades 7 of any length can also be used.

[0028] The airfoil portion 52 has a shape designed to generate lift, while the blade root portion 50 has a circular or elliptical cross-section for structural considerations and to facilitate the installation of the blade on the rotor hub. The diameter or chord of the blade root portion 50 can be constant along the entire blade root portion 50. At the transition portion 51, the profile gradually changes from the circular or elliptical cross-section of the blade root portion 50 to the airfoil profile of the airfoil portion 52.

[0029] The wind turbine blade 7 includes a blade shell 73. The blade shell may include two blade shell parts, such as a pressure side blade shell and a suction side blade shell. The pressure side blade shell may be joined (e.g., glued or bonded) to the suction side blade shell along a joining line (which extends along the leading edge 53 and the trailing edge 54). The blade shell 73 includes an outer or external surface that defines the external shape of the blade (e.g., the external shape at the blade root portion and the external shape at the airfoil portion). The blade shell 73 also includes an inner or internal surface that defines the internal volume of the blade and faces the load-bearing structure (not shown). The blade shell 73 may be made of a fiber-reinforced polymer, such as glass fiber and / or carbon fiber.

[0030] Figure 4 A cross-sectional view of the wind turbine blade is shown. The suction side 57 and the pressure side 56 extend from the leading edge 53 to the trailing edge 54. The wind turbine blade 7 further includes a chord line 38 between the leading edge 53 and the trailing edge 54. The chord line 38 extends in the spanwise direction. The flap direction 39 is substantially perpendicular to the chord line 38. Figure 3

[0031] Although not shown in these figures, the wind turbine blade 7 may be slightly twisted according to the design. Blade twist refers to the variation of the chord line 38 from the blade root portion 50 to the blade tip end 72. Blade twist optimizes the angle of attack and thus optimizes the lift of the blade span. For example, the wind turbine blade may be twisted by an angle between 5 and 20 degrees from the root to the tip, i.e., the chord line at the root portion and the chord line in the region adjacent to the blade tip end form an angle between 5 and 20 degrees. The loads acting on the wind turbine blade may generate torsional loads. These torsional loads may cause torsional deformation of the wind turbine blade. Therefore, the wind turbine blade may be twisted or torsionally deformed about the spanwise direction.

[0032] The wind turbine blade 7 includes a blade structure that provides stiffness to the wind turbine blade. The blade structure of this example includes the blade shell 73 and a load-bearing structure. In other examples, the blade structure may also include a plurality of structural ribs arranged along the length of the blade. In this example, the load-bearing structure includes shear webs, such as a leading edge shear web 43 and a trailing edge shear web 44. A cavity 42 is defined between the leading edge shear web 43 and the trailing edge shear web 44. The cavity 42 may extend along the entire length in the spanwise direction. The load-bearing structure of this figure also includes a pressure side spar cap 74 arranged at the pressure side 56 and a suction side spar cap 76 arranged at the suction side 57. In some examples, the shear webs 43 and 44 may be spar boxes having spar sides (such as a trailing edge spar side and a leading edge spar side).

[0033] Figure 5 A wind turbine blade twist measurement system 100 according to an example of the present disclosure is schematically presented. The wind turbine blade twist measurement system 100 is arranged within the wind turbine blade 7.

[0034] The wind turbine blade twist measurement system 100 of this figure includes a shaft 110 which is arranged in the wind turbine blade 7 in a direction substantially parallel to the spanwise direction 37 of the wind turbine blade. In some examples, such as in a swept blade, substantially parallel to the spanwise direction 37 of the wind turbine blade may include being parallel to the fiber direction of the spar cap laminate.

[0035] In some examples, the shaft can be hollow to reduce the overall weight of the blade. The shaft can be made of a lightweight and non-conductive material, such as a composite including fiberglass and Kevlar. The shaft can include both axial fibers and inclined (e.g., arranged at 45°) fibers. These inclined fibers increase the torsional stiffness of the shaft. Thus, the torsional deformation of the shaft can be minimized. In some examples, the shaft can include biaxial fibers, such as at a 30° angle, to provide both bending stiffness and torsional stiffness. In some examples, the shaft can have a diameter between 15 mm and 35 mm, such as between 20 mm and 30 mm.

[0036] The shaft 110 of this example includes a first shaft portion 111 and a second shaft portion 112. The second shaft portion 112 of this figure is fixedly coupled to the blade structure of the wind turbine blade 7. The blade structure can be a shear web (e.g., a shear web such as the shear webs 43, 44 described above) or a diaphragm rib that encloses the cross-section of the blade. The second shaft portion 112 can be rigidly attached to the inner side of the leading-edge shear web or the inner side of the trailing-edge shear web. Thus, the shaft can extend a length along the cavity defined between the leading-edge shear web and the trailing-edge shear web. The second shaft portion can be coupled to the blade structure that is disposed in the region of the half of the blade closest to the blade tip end, e.g., in the outermost third portion of the wind turbine blade.

[0037] In additional examples, the blade structure can include a balance box or a balance chamber that is arranged between the pressure side and the suction side at a predetermined position along the length direction. The balance box or balance chamber is a chamber filled with material to adjust the static moment of the blade. In these examples, the second shaft portion 112 can be rigidly connected to the balance box. For example, the second shaft portion 112 can be inserted into the balance box. Glue can be used to attach the shaft portion 112 to the balance box.

[0038] In this example, since the second shaft portion 112 is rigidly coupled to the blade structure, the torsional deflection of the blade 7 causes the rotation of the shaft 110.

[0039] The first shaft portion 111 is rigidly connected to the rotating member 121 of the rotational sensor assembly 120. The rotating member 121 is rotatably connected to the stationary member 122 of the rotational sensor assembly 120. Thus, the rotation of the shaft 110 caused by the torsional deflection of the blade does not cause the stationary member 122 to rotate. The rotating member 121 and the stationary member 122 thus form a bearing arrangement. The rotating member 121 may include an inner bearing race, and the stationary member may include an outer bearing race. Roller elements (such as ball bearings) may be arranged between the rotating member and the stationary member. The ball bearings may be made of a non-metallic material, such as plastic, glass or ceramic.

[0040] The rotational sensor assembly 120 of this example further includes a sensor 123 for determining the rotational movement of the rotating member 121 relative to the stationary member 122. The rotation of the rotating member 121 relative to the stationary member 122 indicates the rotation of the shaft 110 and thus the torsional deflection of the blade 7. Thus, the torsional angle at the portion of the blade rigidly connected to the second shaft portion 112 can be determined by the sensor 123.

[0041] In some examples, the rotational sensor assembly may include an absolute encoder. Compared to an incremental encoder, an absolute encoder may allow the determination of the same absolute blade twist value after a system reset because the position of each rotating member is associated with a specific marker or unique code. However, in some examples, if the relative torsional change during operation is sufficient, the rotational sensor assembly may include an incremental encoder.

[0042] In some examples, the sensor 123 may include an optical sensor. The rotating member may include a disk having a plurality of optical markers or codes. A transmitter may emit one or more beams of light towards a receiver. The disk with the optical markers or codes is arranged between the transmitter and the receiver. Thus, the number of light beams received by the receiver depends on the optical markers of the disk. Thus, the sensor can detect a specific optical marker and determine the angular position of the rotating member associated with that optical marker.

[0043] In some examples, the sensor may be a magnetic sensor. In these examples, the disk includes magnetic poles, and the sensor includes a magnet. The change in the magnetic field between the magnetic poles and the magnet provides the position of the disk relative to the magnet associated with the stationary member.

[0044] The rotational sensor assembly may be configured to output a signal indicating the rotational movement of the rotating member relative to the stationary member. A controller (such as a wind turbine controller) may thus receive the output signal. The rotational deformation of the blade can be compared with the expected value under a given condition. Depending on the result, a load mitigation strategy can then be applied to reduce the torsional deformation of the blade, or other measures can be taken regarding its operation, or data can be collected into a database for further value optimization of the turbine itself or other turbines in the power plant or in future designs.

[0045] The wind turbine blade twist measurement system 100 of this example further includes a connection structure 130 that movably connects the rotational sensor assembly 120 to the blade structure of the blade 7 in the spanwise direction 37. The connection structure 130 blocks the rotational movement of the rotational sensor assembly 120 and allows axial movement. Thus, when the rotational sensor assembly 120 is connected to the blade structure through the connection structure 130, the rotational sensor assembly 120 can move in a direction parallel to the spanwise direction. Therefore, the influence of the bending and thermal expansion of the blade 7 and / or the shaft 110 on the measured values obtained by the sensor 123 can be reduced.

[0046] In some examples, the connection structure 130 includes guide rails extending in a direction substantially parallel to the spanwise direction 37 of the wind turbine blade 7. The guide rails can be rigidly connected to the blade structure, such as a shear web. The rotational sensor assembly 120 can be configured to slide on the guide rails. Thus, the rotational sensor assembly 120 according to these examples can slide on the guide rails attached to the blade structure.

[0047] In some examples, the connection structure 130 includes a deformable portion or a deformable element. The shape of the deformable portion or the deformable element may change under the action of a load. Therefore, the deformation of the deformable portion or the deformable element can compensate for the dimensional changes of the shaft 110 and / or the blade 7. An example of the deformable element can be a spring that connects the rotational sensor assembly 120 to the blade structure.

[0048] The connection structure 130 can include a deformable portion and an external portion configured to be connected to the blade structure. The deformable portion can be connected to the rotational sensor assembly 120. The deformable portion can deform under a load in a direction parallel to the spanwise direction 37 of the wind turbine blade 7 so that the rotational sensor assembly 120 moves relative to the blade structure in a direction substantially parallel to the spanwise direction 37 of the wind turbine blade 7.

[0049] In some examples, the wind turbine blade twist measurement system 100 can include one or more bearing supports for rotatably connecting the shaft 110 to the blade structure. The bearing supports can be distributed at different positions along the length of the blade 7. The bearing supports can reduce the bending of the shaft 110.

[0050] In some examples, the bearing support can be a tubular element whose inner diameter is larger than the outer diameter of the shaft 110. Thus, the shaft 110 can rotate within the tubular element. The inner surface of the tubular element can include a material with a low coefficient of friction. In some examples, a ball bearing can be defined between the outer diameter of the shaft 110 and the bearing support.

[0051] In other examples, the bearing support may include an inner race and an outer race. The inner race may rotate relative to the outer race. The inner race may be fixedly connected to the shaft 110. For example, the inner race may clamp the shaft 110. In these examples, the outer race may be slidably connected to the blade structure. For example, the connection structure 130 according to any of the examples disclosed herein may be used to connect the outer race to the blade structure.

[0052] The bearing support may be supported by a support plate. The support plate may extend from the pressure side to the suction side of the blade. The support plate may include a curved shape. For example, the support plate may include a plurality of curved segments. In some examples, the support plate includes a pressure-side curved segment spanning from the bearing support to the pressure side and a suction-side curved segment spanning from the bearing support to the suction side. These two curved segments may include S-shaped segments, such as double S-shaped segments. This type of support plate may reduce the adverse effects of blade deflection on the bearing support. Accordingly, the bending loads and axial loads acting on the shaft and the supported bearings may be minimized. As a result, the friction in the bearing support may be reduced, which may lead to improved measurement accuracy and lifespan of the wind turbine blade torsion measurement system.

[0053] Figure 6 A wind turbine blade torsion measurement system 100 according to an example of the present disclosure is schematically presented. The wind turbine blade torsion measurement system 100 may be as described in the example with reference to Figure 5 ; however, in Figure 6 , the second shaft portion 112 is connected to the second rotational sensor assembly 120a, rather than being rigidly connected to the blade structure as in Figure 5 .

[0054] In Figure 6 , the second rotational sensor assembly 120a is rigidly connected to the blade structure. The second rotational sensor assembly 120a may be according to any of the examples disclosed herein. The second shaft portion 112 of this figure is rigidly connected to the rotating member of the second rotational sensor assembly 120a, and the fixed member is rigidly connected to the blade structure.

[0055] However, in other examples, the second rotational sensor assembly 120a may be movably connected (e.g., slidably connected) to the blade structure by a second connection structure. The second connection structure may be a connection structure according to any of the examples disclosed herein. In these examples, an axial stop may be provided in any connection structure to counteract the centrifugal force.

[0056] In Figure 6In an example, the stationary members of the rotational sensor assemblies 120 and 120a rotate with the blade structure. Thus, the torsional deformation of the blade 7 causes rotational movement of the stationary members of the rotational sensor assemblies 120 and 120a. Since the torsional deformation of the blade increases with increasing distance from the root, the rotation of the stationary member of the second rotational sensor assembly 120a is greater than the rotation of the stationary member of the rotational sensor assembly 120.

[0057] The rotating member may rotate about the stationary members of the rotational sensor assemblies 120 and 120a. Thus, the rotation of the stationary member does not cause rotation of the rotating member. When the blade 7 undergoes torsional deformation, the rotating member remains substantially in a fixed position. Thus, in this example, the stationary member rotates about the rotating member. The sensor may detect the relative movement between the rotating member and the stationary member of each rotational sensor assembly. The difference between the rotational movement detected by the second rotational sensor assembly 120a and the rotational movement detected by the rotational sensor assembly 120 indicates the torsional deformation of the blade between these points.

[0058] Figures 7a through 7f schematically illustrate examples of rotational sensor assemblies and connection structures in accordance with the present disclosure.

[0059] In Figure 7a, the connection structure 130 includes an outer portion 132 that is rigidly connected to the blade structure. The outer portion 132 may be connected to a shear web and / or a rib structure of the blade structure. Bolts (e.g., nylon bolts) may be used to rigidly connect the outer portion 132 to the blade structure.

[0060] In some examples, the outer portion 132 includes a suction side outer portion configured to connect to a suction side shear web of the blade structure and a pressure side outer portion configured to connect to a pressure side shear web of the blade structure. Thus, the connection structure may extend in a direction parallel to the blade direction 39.

[0061] In this example, the connection structure 130 further includes a deformable portion 131. The deformable portion 131 is connected to the rotational sensor assembly 120. As can be seen in Figure 7a, the deformable portion 131 is configured to deform under a load in a direction parallel to the axis 110 (e.g., parallel to the spanwise direction 37 of the wind turbine blade). Thus, when the first shaft portion 111 is coupled to the blade structure of the wind turbine blade, the rotational sensor assembly 120 may move relative to the blade structure in a direction substantially parallel to the spanwise direction 37.

[0062] In this example, the deformable part 131 is a flat plate. The flat plate of this figure extends in a direction substantially parallel to the flap direction 39 of the wind turbine blade and is configured to bend about a direction substantially parallel to the leading edge direction of the wind turbine blade. The flat plate can bend under a load about a direction substantially parallel to the leading edge direction of the wind turbine blade. The flat plate can include a thickness that allows bending but also holds the rotational sensor assembly 120 in a specific position along the flap direction and / or the leading edge direction.

[0063] An aperture can be provided in the flat plate to allow the first shaft portion 111 of the shaft 110 to be connected to the rotating member 121 of the rotational sensor assembly 120. The rotational sensor assembly 120 of this example can be according to any example disclosed herein.

[0064] Due to compensation for bending and thermal expansion, the shaft 110 can be mounted below the flap neutral axis 40 without adversely affecting the accuracy of rotational measurement.

[0065] In the example of this figure, the rotational sensor assembly 120 is pivotally and / or slidably coupled to the connection structure 130. This enhances the compensation for bending and / or thermal expansion of the blade and / or the shaft.

[0066] The rotational sensor assembly 120 of this figure includes a sensor plate 140 arranged substantially perpendicular to the shaft 110. The sensor plate 140 is rotatably connected to the rotating member 121. The sensor plate of this example is fixedly connected to the deformable part 131 of the connection structure 130. Bearings can be provided to rotatably connect the rotating member 121 to the sensor plate 140. In other examples, the sensor plate 140 can be connected to the fixed member 122. The sensor plate 140 of this figure can deform under a load to move the fixed member 122 and the rotating member 121 relative to the connection structure 130. Spacers can be provided at the corners of the sensor plate 140 to allow the central portion of the sensor plate to deform towards the flat plate of the connection structure 130. The sensor plate of this example allows the assembly formed by the fixed member 122 and the rotating member 121 to pivot about a direction substantially parallel to the leading edge direction and / or about a direction substantially parallel to the flap direction 39. Soft zones or weak zones can be provided to facilitate the deformation of the sensor plate 140. The soft zones can be arranged around the central portion of the sensor plate 140.

[0067] In other examples, the rotational sensor assembly 120 includes a plurality of deformable elements extending in a direction substantially parallel to the shaft 110. These deformable elements can connect the fixed member 122 of the rotational sensor assembly 120 to the connection structure 130. Thus, the rotational sensor assembly 120 can pivot and / or slide on the connection structure 130.

[0068] Similar to the connection structure 130 of FIG. 7a, the connection structure 130 of FIG. 7b also includes an outer portion 132 rigidly connected to the blade structure and a deformable portion 131 that allows the rotational sensor assembly 120 to move relative to the blade structure.

[0069] The outer portion 132 of FIG. 7b includes a root-side outer portion 133 and a tip-side outer portion 134. In this example, the root-side outer portion 133 and the tip-side outer portion 134 are connected to the pressure-side spar cap 74, for example, by bonding. However, in other examples, the outer portion 132 may be connected to the suction-side spar cap. In this figure, the deformable portion 131 includes a root-side flat plate 135 extending from the root-side outer portion 133 and a tip-side flat plate 136 extending from the tip-side outer portion 134. The tip-side flat plate 136 is substantially parallel to the root-side flat plate 135. These flat plates extend in a direction substantially parallel to the chord direction 39. The upper plate 137 connects the tip-side flat plate 136 to the root-side flat plate 135. The connection structure 130 of this figure thus forms a U-shaped profile. The U-shaped profile may be made of biaxial fibers to allow deformation and avoid stress concentration.

[0070] In the example of FIG. 7b, specifically in the upper portion of the root-side flat plate 135, the rotational sensor assembly 120 is connected to the root-side flat plate 135. This location may cause the root-side flat plate 135 and the tip-side flat plate 136 to bend about the edgewise direction. Thus, the rotational sensor assembly 120 may move in a direction parallel to the spanwise direction 37. In other examples, the rotational sensor assembly 120 may be connected to the tip-side flat plate 136.

[0071] The rotational sensor assembly 120 of this figure includes a sensor plate 140 rotatably connected to a rotating member. However, in other examples, a fixed member may be rigidly connected to the sensor plate. The sensor plate 140 may be according to any example disclosed herein. For example, the sensor plate 140 may allow the rotational sensor assembly to move relative to the connection structure 130.

[0072] In FIG. 7c, the deformable portion 131 of the connection structure 130 includes a plurality of bending segments. These bending segments cause the deformable portion 131 to deform in a direction substantially parallel to the spanwise direction 37 while providing sufficient stiffness to hold the rotational sensor assembly 120 in a specific position along the chord direction 39 and / or the edgewise direction. Thus, the deformable portion 131 of this figure is a plate formed by bending segments or bending portions.

[0073] The deformable portion 131 includes a plurality of curvature portions arranged along the blade direction 39. These curvature portions can be deformed around the leaf edge direction. These curvature portions can be formed by S-shaped segments and / or multi-S-shaped segments (such as double S-shaped segments). In the example of FIG. 7c, the bending plate includes two double S-shaped segments: a pressure-side double S-shaped segment 151 and a suction-side double S-shaped segment 152, which are connected together at the central region of the deformable portion 131. The rotational sensor assembly 120 of this example is connected to the central portion.

[0074] In this example, the outer portion 132 is connected to the spar cap of the blade structure. The pressure-side double S-shaped segment 151 terminates at the pressure-side outer portion 138, and the suction-side double S-shaped segment 152 terminates at the suction-side outer portion 139. The pressure-side outer portion 138 is connected to the pressure-side spar cap 74, and the suction-side outer portion 139 is connected to the suction-side spar cap 76.

[0075] In FIG. 7c, the suction-side outer portion 139 and the pressure-side outer portion 138 extend substantially towards the root portion of the blade. The outer portion 132 can be bent on the deformable portion 131. The distance between these outer portions can be adjusted. Therefore, this distance can be adjusted to the distance between the pressure-side spar cap 74 and the suction-side spar cap 76. Thus, variations in the thickness of the spar cap and / or the internal unevenness of the blade can be compensated. Therefore, the assembly and installation of the blade twist measurement system can be simplified. The outer portion 132 of this example can apply pressure to the spar cap to fix the connection structure 130 in a specific position.

[0076] In this figure, the sensor plate 140 is arranged at the root side of the deformable portion 131. In other examples, the sensor plate can be arranged at the tip side of the deformable portion 131.

[0077] The sensor plate 140 can be configured to allow the rotational sensor assembly to move relative to the connection structure 130.

[0078] In other examples, a first sensor plate can be arranged at the root side of the deformable portion 131, and a second sensor plate can be arranged at the tip side of the deformable portion 131. The stability of the rotational sensor assembly 120 can thus be increased. The first sensor plate and the second sensor plate can also be configured to deform when a load is applied.

[0079] In FIG. 7d, the connection structure 130 is based on the connection structure of FIG. 7c. In particular, the deformable portion 131 of this example includes a plurality of bending segments. As in the example of FIG. 7c, the rotational sensor assembly 121 of FIG. 7e is connected to the central portion arranged between the pressure-side double S-shaped segment 151 and the suction-side double S-shaped segment 152.

[0080] The rotational sensor assembly of the figure includes a first sensor plate 140a and a second sensor plate 140b. The sensor plates 140a and 140b can be according to any of the examples herein. For example, the first sensor plate 140a can be according to the sensor plate 140 of FIG. 7c. The first sensor plate 140a is arranged at the root side of the deformable portion 131, and the second sensor plate 140b is arranged at the tip side of the deformable portion 131.

[0081] The rotational assembly 120 of the example is connected to a first sensor plate 140a according to any of the examples herein. The first sensor plate 140a is connected to the second sensor plate 140b. A plurality of spacers are arranged between the first sensor plate 140a and the second sensor plate 140b. Bolts can be used to connect the first sensor plate 140a to the second sensor plate 140b. These bolts can be arranged inside the spacers. These bolts can additionally be used to connect the second sensor plate 140b to the deformable portion 131 of the connection structure. Thus, the deformable portion (such as the central portion) can be clamped between the sensor plates 140a and 140b. The second sensor plate 140b of the example is rotatably connected to the shaft.

[0082] Therefore, the stability of the rotational sensor assembly 120 can be increased, and at the same time, the decoupling of the deflection of the blade relative to the torsion of the rod can be further improved.

[0083] In the example of FIG. 7e, the connection structure 130 is connected to the blade rib structure 90. The blade rib structures can be arranged along the length of the blade. These blade rib structures 90 can increase the local stiffness of the blade.

[0084] The connection structure 130 of the example includes an outer portion 132 rigidly connected to the blade rib structure 90. The deformable portion 131 is arranged between the sensor plate 140 and the outer portion 132. The deformable portion 131 can include a plurality of deformable elements extending in a direction substantially parallel to the spanwise direction 37. Springs or deformable plates (such as ZZ-shaped plates) can be examples of the deformable elements to movably connect the rotational sensor assembly to the blade structure (for example, connected to the blade rib structure 90) in a direction substantially parallel to the spanwise direction 37. The sensor plate 140 can be according to any example herein.

[0085] The example of FIG. 7f is similar to the example of FIG. 7e. However, the connection structure 130 of the example of FIG. 7f includes a deformable plate 181. The deformable plate 181 can be according to the sensor plate 140 according to any example herein. The blade rib structure 90 is arranged between the sensor plate 140 and the deformable plate 181. The sensor plate 140 is connected to the deformable plate 181 through the blade rib structure 90. Bolts can pass through the blade rib structure to connect the sensor plate 140 and the deformable plate 181. Therefore, the connection between the rotational sensor assembly 120 and the connection structure 130 can be further enhanced.

[0086] Figure 8 Schematically presents a sensor board according to any example disclosed herein. The sensor board 140 of this figure is square. However, the sensor board may include any other suitable shape.

[0087] The sensor board 140 includes a central portion 141. A rotating member may be connected to the central portion 141 of the sensor board 140. In this example, a sensor board bearing 142 is disposed at the central portion 141. The sensor board bearing 142 includes an inner ring and an outer ring. The inner ring may rotate with respect to the outer ring. Roller elements (such as ball bearings) may be disposed therebetween. The inner ring may be rigidly connected to the shaft and / or the rotating member. The inner ring defines a central aperture 149 to receive the shaft and / or the rotating member. In this example, the outer ring is rigidly connected to the sensor board, and the inner ring is rigidly connected to the shaft.

[0088] However, in other examples, a fixed member is rigidly connected to the sensor board 140. In these examples, the central aperture 149 of the central portion 141 is configured to allow the shaft and / or the rotating member to pass therethrough.

[0089] In this example, holes are provided at each of the corners of the sensor board 140. Fasteners (such as bolts or screws) may be inserted into the holes and fixed to the deformable portion of the connection structure. The sensor board 140 extends a first length in a first direction 147 and a second length in a second direction 148. The sensor board 140 may be made of glass-reinforced plastic.

[0090] The sensor board 140 of this example includes a plurality of apertures around the central portion 141. These apertures weaken the stiffness of the sensor board 140 to allow the sensor board to deform in a direction perpendicular to the first direction 147 and the second direction 148. When installed inside a wind turbine blade, the sensor board 140 may deform in a direction parallel to the spanwise direction.

[0091] In this figure, the plurality of apertures includes arcuate apertures. In other examples, the apertures may include any other suitable shape. In this figure, a pair of arcuate inner apertures 143a, 143b are disposed around the central portion 141. The arcuate inner apertures 143a and 143b of this example extend between 150 degrees and 178 degrees. The arcuate inner apertures are symmetrically disposed with respect to the central aperture 149. Connecting bridges 144a and 144b are disposed between the arcuate inner apertures. In this example, the upper connecting bridge 144a is disposed between the upper ends of the arcuate inner apertures 143a and 143b, and the lower connecting bridge 144b is disposed between the lower ends of the arcuate inner apertures 143a and 143b. The inner bridge and the arcuate inner apertures in this figure define a circular shape around the central aperture 149. In other examples, the arcuate apertures may define an elliptical shape.

[0092] In this example, a pair of arcuate outer orifices 145a and 145b are arranged (e.g., concentrically) around arcuate inner orifices 143a and 143b. Connecting bridges 146a and 146b are arranged between the arcuate outer orifices 145a and 145b. The arcuate outer orifices 145a and 145b of this example are rotated 90 degrees relative to the arcuate inner orifices 143a and 143b. In other examples, the arcuate outer orifices 145a and 145b may be rotated relative to the arcuate inner orifices 143a and 143b at any suitable angle.

[0093] The plurality of orifices (e.g., arcuate orifices) allow the sensor plate 140 to deform in a direction perpendicular to the first direction 147 and the second direction 148. The misalignment of the orifices further allows the sensor plate to bend about a direction perpendicular to the first direction 147 and / or the second direction 148. Thus, the flexibility of the wind turbine blade torsion measurement system is improved. Thus, the compensation for the bending or thermal expansion of the blade and / or the shaft is enhanced. Accordingly, the sensor plate 140 can act as a gimbal arrangement configured to axially deform in a direction perpendicular to the plane defined by the first direction 147 and the second direction 148; and bend about a direction perpendicular to the first direction 147 and / or the second direction 148 while preventing the rotation of the sensor plate 147.

[0094] Figure 9 Schematically presented is a wind turbine blade torsion measurement system arranged within a wind turbine blade 7 according to an example of the present disclosure. As Figure 5 an example, the shaft 110 includes a first shaft portion 111 coupled to a rotational sensor assembly 120 and a second shaft portion 112 rigidly or fixedly coupled to the blade structure.

[0095] The wind turbine blade torsion measurement system 100 may include one or more additional rotational sensor assemblies. Accordingly, the torsional deformation of the blade 7 can be measured at different positions along the length of the blade. Thus, the measurement accuracy is improved. In addition, the gradient torsional deformation between different rotational sensor assemblies can also be obtained. Thus, local effects can be determined.

[0096] In this example, the blade torsion measurement system includes three additional rotational sensor assemblies 120b, 120c, and 120d. In other examples, the number of rotational sensor assemblies may vary. These additional rotational sensor assemblies are arranged between the first shaft portion 111 and the second shaft portion 112. The rotational members of each of these additional rotational sensor assemblies 120b, 120c, and 120d are fixedly connected to the shaft 110.

[0097] The rotational sensor assemblies of these figures can be any of the examples disclosed herein. In some examples, one or more additional rotational sensor assemblies are movably coupled to the blade structure by a connection structure according to any of the examples disclosed herein. In other examples, some of the one or more additional rotational sensor assemblies are directly connected to the blade structure.

[0098] Figures 10a through 10d schematically depict examples of wind turbine blades having multiple wind turbine blade twist measurement systems according to the present disclosure. The wind turbine blade twist measurement systems of these examples can be any of the examples disclosed herein. The multiple wind turbine blade twist measurement systems can be disposed within a cavity defined by two parallel shear webs. In other examples, the wind turbine blade twist measurement systems can be disposed at a leading edge cavity and / or on a trailing edge cavity.

[0099] The multiple wind turbine blade twist measurement systems 100, 100a, and 100b in Figure 10a are disposed substantially parallel to each other in the spanwise direction 37 of the wind turbine blade 7. The length of the shafts can vary to detect the torsional deformation of the blade 7 at different locations. In this example, the rotational sensor assemblies are disposed at the root side ends of the corresponding shafts. The rotational sensor assemblies of this figure are substantially disposed at the same length of the blade. In other examples, the rotational sensor assemblies can be disposed at different lengths of the blade.

[0100] In this example, the shafts of the wind turbine blade twist measurement systems extend from the corresponding rotational sensor assemblies toward the tip end of the blade. In other examples, one or more of the shafts can extend from the corresponding rotational sensor assemblies toward the root end of the blade.

[0101] In Figure 10b, the multiple wind turbine blade twist measurement systems 100, 100a, and 100b are disposed continuously along the spanwise direction 37 of the wind turbine blade 7. This configuration can provide partial measurements of the torsional deformation. The absolute torsional deformation can be obtained by summing the partial measurements provided by each of the wind turbine blade twist measurement systems 100, 100a, and 100b.

[0102] In some examples, the shafts of the wind turbine blade twist measurement systems may partially overlap. The partial torsional deformation with respect to each wind turbine blade twist measurement system can be used to determine the absolute torsional deformation.

[0103] In the example of FIG. 10c, the blade twist blade measurement system is arranged at the outermost half of the blade. The wind turbine blade twist measurement system 100 is arranged closer to the root than the wind turbine blade twist measurement system 100a. The first shaft portion 111 of the shaft 110 faces the root of the blade, and the second shaft portion 112 faces the tip portion of the blade. Conversely, the first shaft portion 111a faces the tip portion of the blade, and the second shaft portion 112a faces the root of the blade. The second shaft portions 112 and 112a face each other. The second shaft portions 112 and 112a can be connected to a single blade member. In other examples, the orientation of the blade twist blade measurement system may be different.

[0104] In this example, the wind turbine blade twist measurement system 100 is arranged in the trailing edge cavity, and the wind turbine blade twist measurement system 100a is arranged in the leading edge cavity.

[0105] The rotation sensor assemblies 120 and 120a can be connected to the connection structure according to any example herein. For example, the rotation sensor assembly 120 can be connected to the connection structure according to the example of FIGS. 7c or 7d; and the rotation sensor assembly 120a can be connected to the connection structure according to the example of FIGS. 7e or 7f.

[0106] The blade 7 of FIG. 10d is a segmented blade. The first blade segment 201 is connected to the second blade segment 202 by a blade joint 203. The blade joint 203 may include a plurality of connectors and one or more fairings covering the connectors. In this example, the first blade segment 201 includes a first wind turbine blade twist measurement system 100, and the second blade segment 202 includes a second wind turbine blade twist measurement system 100a. In this example, the rotation sensor assemblies 120 and 120a face the blade joint 203. The rotation sensor assemblies 120 and 120a are adjacent to the blade joint 203. The rotation sensor assemblies 120 and 120a can be accessed through the fairing. Thus, maintenance and inspection of the rotation sensor assemblies can be easily performed.

[0107] The wind turbine blade twist measurement systems 100 and 100a can be according to any example herein.

[0108] Figure 11 is a block diagram of a method for determining the twist deformation of a wind turbine blade including one or more wind turbine blade twist measurement systems according to an example of the present disclosure.

[0109] The wind turbine blade twist measurement system can be according to any example disclosed herein. As presented at block 310, the method 300 includes determining the rotational movement of a rotating member of a corresponding rotation sensor assembly relative to a fixed member. The relative rotational movement between the rotating member and the fixed member is measured according to any example disclosed herein.

[0110] At block 320, a signal indicating the determined rotational movement is output to a controller. In some instances, the controller may include a data acquisition system. The rotational sensor assembly or assemblies may be communicatively coupled to the controller using a wired connection and / or a wireless connection.

[0111] In some instances, the method may include determining a plurality of rotational movements, each of the plurality of rotational movements corresponding to a different rotational sensor assembly. These different rotational sensor assemblies may belong to a single wind turbine blade twist measurement system or multiple wind turbine blade twist measurement systems.

[0112] In these instances, the method may further include determining the twist deformation of the wind turbine blade at different positions along the spanwise direction of the blade.

[0113] In some instances, the method may further include comparing the rotational movement between the rotating member and the stationary member of the rotational sensor assembly with an expected value. The expected value may be selected for a given condition (e.g., for a specific wind speed and / or pitch angle). Depending on the result, a load mitigation strategy may be activated.

[0114] Figure 12 is a block diagram of a method for installing a wind turbine blade twist measurement system in a wind turbine blade according to an example of the present disclosure.

[0115] As presented at block 410, method 400 includes connecting a rotational sensor assembly to a connection structure. For example, the stationary member of the rotational sensor assembly may be rigidly or fixedly connected to the connection structure. In other instances, the rotating member may be rotatably connected to the connection structure.

[0116] In some instances, connecting the rotational sensor assembly to the connection structure includes connecting a sensor plate to the rotational sensor assembly and to a connection structure according to any example disclosed herein.

[0117] At block 420, the rotating member of the rotational sensor assembly is rigidly connected to a first shaft portion. The first shaft portion may be clamped by the rotating member. Other suitable connection methods (such as welding, bolting, and / or snap fitting) may also apply.

[0118] In some instances, the rotating member may be connected to the first shaft portion before connecting the rotational sensor assembly to the connection structure. In other instances, the rotational sensor assembly is first connected to the connection structure, and then the shaft is connected to the rotating member.

[0119] At block 430, an axis is presented as being arranged in a direction substantially parallel to the spanwise direction of a wind turbine blade. In some instances, arranging the axis in a direction substantially parallel to the spanwise direction may include inserting the axis into the wind turbine blade. In some instances, an axis rigidly connected to a rotating member may be inserted into the wind turbine blade. In other instances, the axis may be inserted into the wind turbine blade and then connected to the rotating member.

[0120] In some instances, inserting the axis into the wind turbine blade includes pushing the axis in a direction parallel to the spanwise direction of the blade. The axis may be pushed into a cavity formed between two shear webs.

[0121] At block 440, a connection structure is presented as being connected to the blade structure. The connection structure may be connected to the blade structure according to any of the examples disclosed herein. For example, the connection structure may include a bendable pressure side outer portion and a bendable suction side outer portion. These outer portions may apply pressure to the spar caps to hold the connection structure in a predetermined position.

[0122] Blocks 410, 420, 430, and 440 disclosed herein are not limited to a particular order. In some instances, the axis, the rotational sensor assembly, and the connection structure are inserted into the wind turbine blade together. This may reduce the number of operations and connections to be performed inside the blade.

[0123] The method may further include connecting the axis to the blade structure. The axis may be connected to the blade structure using a snap-fit connection or an adhesive.

[0124] This written description uses examples to disclose the invention, including the preferred embodiments, and also enables those skilled in the art to practice the invention, including making and using any device or system and performing any combined methods. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. If such other examples have structural elements that are not different from the written language of the claims, or if they include equivalent structural elements that are not materially different from the written language of the claims, then such other examples are intended to be within the scope of the claims. Aspects from the various described embodiments, as well as other known equivalents of each such aspect, may be mixed and matched by those skilled in the art to form additional embodiments and techniques in accordance with the principles of this application. If reference numerals associated with the drawings are placed in parentheses in the claims, they are only used to attempt to increase the intelligibility of the claims and should not be construed as limiting the scope of the claims.

Claims

1. A wind turbine blade twist measurement system (100), comprising: A shaft (110) configured to be arranged in a direction substantially parallel to the spanwise direction (37) of the wind turbine blade (7), wherein the shaft (110) includes a first shaft portion (111) configured to be coupled to the blade structure of the wind turbine blade (7); A rotational sensor assembly (120), comprising: A rotating member (121) rigidly connected to the first shaft portion (111); A stationary member (122) rotatably connected to the rotating member (121); and A sensor (123) for determining the rotational movement of the rotating member (121) relative to the stationary member (122); and A connection structure (130) configured to movably connect the rotational sensor assembly (120) to the blade structure to allow relative movement between the rotational sensor assembly (120) and the blade structure in a direction substantially parallel to the spanwise direction (37) of the wind turbine blade (7).

2. The wind turbine blade twist measurement system (100) according to claim 1, wherein the connection structure (130) includes: An outer portion (132) configured to be rigidly connected to the blade structure; And A deformable portion (131) connected to the rotational sensor assembly (120), which is configured to deform under a load in a direction parallel to the direction of the shaft (110) when the first shaft portion (111) is coupled to the blade structure of the wind turbine blade, so that the rotational sensor assembly (120) moves relative to the blade structure in a direction substantially parallel to the spanwise direction (37) of the wind turbine blade (7).

3. The wind turbine blade twist measurement system (100) according to claim 2, wherein the deformable portion (131) includes a plurality of bending segments.

4. The wind turbine blade twist measurement system (100) according to claim 3, wherein the deformable portion (131) includes an S-shaped segment and / or a multi-S-shaped segment (151, 152).

5. The wind turbine blade twist measurement system (100) according to any one of claims 1 to 4, wherein the rotational sensor assembly (120) is pivotally and / or slidably coupled to the connection structure (130).

6. The wind turbine blade twist measurement system (100) according to claim 5, wherein the rotational sensor assembly (120) includes a sensor plate (140) arranged substantially perpendicular to the shaft (110); wherein the sensor plate (140) is rotatably connected to the rotating member (121) and fixedly connected to the connection structure (130), and wherein the sensor plate (140) is configured to deform under a load so that the stationary member (122) and the rotating member (121) move relative to the connection structure (130).

7. The wind turbine blade twist measurement system (100) according to claim 6, wherein the rotating member (121) is connected to the central portion (141) of the sensor plate (140), and wherein the sensor plate (140) includes a plurality of apertures (143a, 143b, 145a, 145b) around the central portion (141).

8. The wind turbine blade twist measurement system (100) according to any one of claims 1 to 7, further comprising one or more bearing supports for rotatably connecting the shaft (110) to the blade structure.

9. The wind turbine blade twist measurement system (100) according to any one of claims 1 to 8, wherein the shaft (100) includes a second shaft portion (112) fixedly coupled to the blade structure.

10. A wind turbine blade (7) comprising one or more wind turbine blade twist measurement systems (100, 100a, 100b) according to any one of claims 1 to 9.

11. The wind turbine blade (7) according to claim 10, wherein the one or more wind turbine blade twist measurement systems (100, 100a, 100b) include a plurality of wind turbine blade twist measurement systems (100, 100a, 100b).

12. The wind turbine blade (7) according to claim 11, wherein the plurality of wind turbine blade twist measurement systems (100, 100a, 100b) are arranged one after another in the spanwise direction (37) of the wind turbine blade (7).

13. The wind turbine blade according to claim 11, wherein the plurality of wind turbine blade twist measurement systems (100, 100a, 100b) are arranged substantially parallel in the spanwise direction (37) of the wind turbine blade (7).

14. A method (300) for determining the torsional deformation of a wind turbine blade (7) according to any one of claims 10 to 13, comprising: determining (310) the rotational movement of a rotating member (121) of a corresponding rotational sensor assembly (120) relative to a fixed member (122); and outputting (320) a signal indicative of the determined rotational movement to a controller.

15. A method (400) for installing a wind turbine blade twist measurement system (100) according to any one of claims 1 to 9 in a wind turbine blade (7), comprising: connecting (410) the rotational sensor assembly (120) to the connection structure (130); rigidly (420) connecting the rotating member (121) of the rotational sensor assembly (120) to the first shaft portion (111); arranging (430) the shaft (110) in a direction substantially parallel to the spanwise direction (37) of the wind turbine blade (7); and connecting (440) the connection structure (130) to the blade structure.

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