A wind turbine blade deformation state monitoring method

Abstract

The application discloses a wind turbine blade deformation state monitoring method, a plurality of angle sensors are arranged in turn from the blade root side to the blade tip side with the blade root end as the starting reference on the middle axis of the blade web, and two adjacent angle sensors are connected through flexible cables, since the middle axis of the blade web is not in a straight line, the angle sensors form an azimuth angle due to the straightened cables; when the blade is bent and deformed, the angle sensors will produce displacement, so that the pulling direction of the cable is changed, and the blade deformation posture can be obtained through the azimuth angle and the position information of the angle sensor installation. The application is characterized in that a series of associated angle sensors are installed on the middle axis of the blade web, the blade deformation condition is calculated by using geometric principles according to the collected angle data and the installation position, and the application has the advantages of low cost, high accuracy and high reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wind turbine blade deformation monitoring, in particular to a wind turbine blade deformation state monitoring method. BACKGROUND

[0002] In a wind turbine, the blade functions to capture wind energy and convert it into torque, and thus is subjected to a huge wind load, thereby generating a large bending deformation. Excessive deformation of the blade not only affects power generation, but when the deformation is too large, the blade may hit the tower, leading to a serious safety accident. As the length of the blade increases, the stiffness decreases, and the risk of blade deformation becomes greater and greater, so blade deformation state monitoring becomes increasingly important.

[0003] Currently, there are few methods for monitoring blade deformation. One method is to take a photo and estimate the deformation of the blade according to the photo, but this method often cannot monitor in real time and requires manual judgment, and is not suitable for automatic real-time monitoring. Another method is to use a camera and use artificial intelligence to identify the blade deformation, but this method is greatly affected by weather, has high cost, and the technology is not mature enough. There is also a method of monitoring the blade posture by laser scanning radar, but it needs to cover the entire blade to obtain the accurate deformation of the blade, and needs to have a very high sampling rate to collect the high-speed moving blade, so the cost is extremely high and cannot be practically applied. SUMMARY

[0004] The present application proposes a wind turbine blade deformation state monitoring method for low-cost, high-reliability, real-time monitoring of blade deformation state, which overcomes the current difficulty in monitoring blade deformation, high cost, and immature technology. The method is to install a series of associated angle sensors on the middle axis of the blade web, according to the collected angle data, combined with the installation position, and using geometric principles to calculate the blade deformation.

[0005] To achieve the above purpose, the technical solution provided by the present application is as follows: a wind turbine blade deformation state monitoring method, which performs the following operations:

[0006] A plurality of angle sensors are arranged in order from the blade root end to the blade tip side on the middle axis of the blade web, and two adjacent angle sensors are connected by a flexible cable. Since the middle axis of the blade web is not on a straight line, the cable in a straightened state will cause the angle sensors to form an azimuth angle.

[0007] When the blade is deformed, the angle sensor will produce displacement, so that the direction of the cable is changed, and the deformed posture of the blade can be obtained through the position information of the azimuth angle sensor and the angle sensor, and the deformed posture of the blade can be described by the three-dimensional coordinate system (x, y, z) of the angle sensor, wherein the three-dimensional coordinate system (x, y, z) of the angle sensor is taken as the Z-axis of the blade root coordinate system as the reference axis direction, the chord length of the blade as the Y-axis direction, and the X-axis direction perpendicular to the chord length of the blade; the blade is mainly deformed in the X direction, and then in the Y direction, and the blade on the axis is deformed in the length direction, but the deformation amount is the smallest, and the influence is also the smallest, so it is ignored; the specific is as follows:

[0008] The projection coordinates of the angle sensor installation position on the Z-axis are known, the corresponding plane coordinates are calculated in the same plane through the azimuth angle and the geometric relationship, the XZ plane and the ZY plane are perpendicular to each other, and the coordinates of the two planes are combined with each other to obtain the position information of the angle sensor in the three-dimensional coordinates of the blade, and finally, the deformed posture of the blade can be obtained according to the position information.

[0009] Further, a cable connecting point is installed on the middle axis of the blade web between the last angle sensor and the blade tip, which is used to connect the last angle sensor.

[0010] Further, the angle sensors installed on the middle axis of the blade web are n, the first angle sensor, the second angle sensor to the n-th angle sensor from the blade root side, the angles measured in the X direction are 0, theta_x1, theta_x2, …, theta_x(n-1), and the angles measured in the Y direction are 0, theta_y1, theta_y2, …, theta_y(n-1).

[0011] The arrangement interval between two angle sensors is known;

[0012] When the coordinates of the previous angle sensor are taken as the reference, the relative coordinates (xn, yn, zn) of the position of the next angle sensor are approximately obtained by the following formula:

[0013] Nn=Ln-L(n-1)

[0014] xn=Nn×tan(theta_x(n-1))

[0015] yn=Nn×tan(theta_y(n-1))

[0016] zn=Nn

[0017] In the formula, Nn is the projection position of the nth angle sensor on the Z axis; Ln is the arrangement interval between the next angle sensor and the previous angle sensor, i.e. the arrangement interval between the nth and the (n-1)th angle sensors; L(n-1) is the arrangement interval of the previous angle sensor;

[0018] Therefore, knowing the position relative coordinate of the previous angle sensor as the reference, and adding the three-dimensional coordinate system absolute coordinate of the previous angle sensor, the position absolute coordinate of the next angle sensor can be obtained, so that the spatial position of the blade is calculated as follows:

[0019] a1(x,y,z) = [0, 0, 0], a2(x,y,z) = a1(x,y,z) + [N2 x tan(theta_x1), N2 x tan(theta_y1), N2], a3(x,y,z) = a2(x,y,z) + [N3 x tan(theta_x2), N3 x tan(theta_y2), N3], …, an(x,y,z) = a(n-1)(x,y,z) + [Nn x tan(theta_x(n-1)), Nn x tan(theta_y(n-1)), Nn];

[0020] In the formula, a1(x,y,z) is the coordinate of the first angle sensor, and an(x,y,z) is the coordinate of the nth angle sensor; it is assumed that a(n+1)(x,y,z) is the coordinate of the blade tip, since a(n+1)(x,y,z) and an(x,y,z) are close in distance, it can be approximately considered that the angle changes are the same, and a(n+1)(x,y,z) should be larger than an(x,y,z); by measuring the rigidity difference during production and multiplying a correction coefficient, a more accurate deformation can be obtained, as shown in the following formula:

[0021] theta_xn = theta_x(n-1) x K_x

[0022] theta_yn = theta_y(n-1) x K_y

[0023] a(n+1)(x,y,z) = an(x,y,z) + [N(n+1) x tan(theta_xn), N(n+1) x tan(theta_yn), N(n+1)];

[0024] In the formula, theta_xn is the angle measured in the X direction of the blade tip, K_x is the correction coefficient in the X direction of the blade tip, theta_yn is the angle measured in the Y direction of the blade tip, K_y is the correction coefficient in the Y direction of the blade tip, and N(n+1) is the projection position of the blade tip on the Z axis.

[0025] Further, the angle sensor is a non-contact Hall sensor.

[0026] Further, the non-contact Hall sensor comprises a base, a rotating ring, a rotating half ring, a two-dimensional Hall sensor and a magnet; the base is fixedly connected with a blade web; the rotating ring is installed on the base through a first pin shaft and can rotate around the first pin shaft; the rotating half ring is installed on the rotating ring through a second pin shaft and can rotate around the second pin shaft; the rotating ring and the rotating half ring jointly form two rotating degrees of freedom perpendicular to each other, realizing free rotation in a large direction; one end of the rotating half ring is formed with a first mounting position for connecting a cable; the base is formed with a second mounting position for connecting the cable; the other end of the rotating half ring is installed with the magnet for generating a magnetic field; the two-dimensional Hall sensor is installed on the base and located at the center of the rotating ring and the rotating half ring, and the change of magnetic flux can be measured through the two-dimensional Hall sensor, so as to calculate the azimuth angle of the magnet in the X and Y directions.

[0027] Further, the non-contact Hall sensor adopts a non-magnetic material to avoid interference with the magnetic field.

[0028] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0029] 1. Low cost. Only a few angle sensors need to be arranged on a blade, and the deformation of the blade can be calculated through simple mathematical calculation, which is low in cost.

[0030] 2. High accuracy. Since the angle directly reflects the deformation of the blade, the measurement accuracy is high.

[0031] 3. High reliability. The non-contact Hall sensor is used to measure the angle, which avoids the angle deviation caused by wear, because it is inside the blade and is not affected by the external environment such as weather. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a three-dimensional coordinate system diagram of a blade.

[0033] Figure 2 It is one of the installation diagrams of two angle sensors on the blade web.

[0034] Figure 3 It is the second installation diagram of two angle sensors on the blade web.

[0035] Figure 4 It is one of the structure diagrams of the angle sensor.

[0036] Figure 5 It is the second structure diagram of the angle sensor.

[0037] Figure 6A schematic diagram is calculated for the angle sensor position.

[0038] Figure 7 A schematic diagram is calculated for the blade deformation. DETAILED DESCRIPTION

[0039] The application will be further described in conjunction with the embodiments and the accompanying drawings, but the embodiments of the application are not limited thereto.

[0040] The embodiment discloses a wind turbine blade deformation state monitoring method, and specific conditions are as follows:

[0041] First, an angle sensor is installed on the middle axis of the blade web during blade production. The angle sensors are unevenly arranged from the blade root side to the blade tip side. The blade tip side is more densely arranged than the blade root side, because the blade stiffness and the load condition determine that the farther away from the blade root, the greater the deformation, so the density needs to be increased at the blade tip to improve the measurement accuracy, and the blade root is less arranged to reduce the cost. If 5 angle sensors are arranged, the last end of the blade root is taken as the starting reference, and the angle sensors are arranged at 0%, 25%, 50%, 62.5%, and 75% of the length of the blade. Only one cable connection point needs to be arranged at 87.5% to connect the last angle sensor. Since the space at the blade tip is small and cannot install an angle sensor, the last section of the blade deformation can be estimated by the value of the last angle sensor. The angle sensor installation method on the web is shown in FIGS. 1 and 2. Figure 2 and Figure 3

[0042] ​The angle sensor is a non-contact Hall sensor, which is installed at the middle axis of the blade web plate and can well represent the deformation of the blade. The angle sensor mainly comprises a base, a rotating ring, a rotating half ring, a two-dimensional Hall sensor and a magnet. The base is fixedly connected with the blade web plate. The rotating ring is installed on the base through a first pin shaft and can rotate around the first pin shaft. The rotating half ring is installed on the rotating ring through a second pin shaft and can rotate around the second pin shaft. The rotating ring and the rotating half ring together form two perpendicular rotation degrees of freedom, realizing free rotation in a large direction. One end of the rotating half ring is formed with a first mounting position for connecting a cable, and the cable installed at the first mounting position is used for connecting the base of the next angle sensor. The base is formed with a second mounting position for connecting the cable. The other end of the rotating half ring is installed with the magnet for generating a magnetic field. The two-dimensional Hall sensor is installed on the base and located at the center of the rotating ring and the rotating half ring. The two-dimensional Hall sensor can measure the change of the magnetic flux, so as to calculate the azimuth angle of the X and Y directions of the magnet. The middle axis of the blade web plate is not on a straight line, so that the cable in a straightened state can form an azimuth angle with the angle sensor, and the azimuth angle is equal to the azimuth angle of the angle sensor connected therewith. The angle sensor adopts a non-magnetic material to avoid interference with the magnetic field. The structure of the angle sensor is shown in Figure 4 and Figure 5 .

[0043] When the blade is bent and deformed, the base will be displaced, so that the direction of the cable is changed, the azimuth angle of the magnet and the two-dimensional Hall sensor is changed, and through the azimuth angle and the position information of the angle sensor, the deformation posture of the blade can be obtained. The deformation posture of the blade can be described by the three-dimensional coordinate system (x, y, z) of each angle sensor, wherein the three-dimensional coordinate system (x, y, z) of the angle sensor takes the Z axis of the blade root coordinate system as the reference axis direction, the chord length of the blade as the Y axis direction, and the direction perpendicular to the chord length of the blade as the X axis direction. The blade three-dimensional coordinate system is shown in Figure 1 .

[0044] The cable itself has a certain elastic deformation amount to ensure that it will not be broken or damaged when stretched. The blade is mainly deformed in the X direction, and then in the Y direction. The blade on the axis will be deformed in the lengthening direction, but the deformation amount is the smallest and the influence on the blade is also the smallest, which can be ignored.

[0045] The projection coordinates of the angle sensor installation position on the Z axis are known. The corresponding plane coordinates are calculated through the azimuth angle and the geometric relationship in the same plane. The XZ plane and the ZY plane are perpendicular to each other. The coordinates of the two planes are combined with each other to obtain the position information of the angle sensor in the three-dimensional coordinates of the blade. Finally, according to the position information, the deformation posture of the blade can be obtained.

[0046] Suppose the blade is about 1 hundred meters long, and the blade manufacturing is done with five angle sensors installed on the middle axis of the blade web at L_0=0 meters, L_1=25 meters, L_2=50 meters, L_3=62.5 meters, L_4=75 meters, and one cable connection point at L_5=87.5 meters for connecting the cable of the fifth angle sensor. L_6=100 meters is the position of the blade tip, as shown in Figure 6

[0047] The angle sensors are connected by flexible cables, so that the blade shape can be calculated by measuring the angles between the angle sensors when the blade is in the original state or deformed.

[0048] The first angle sensor, the second angle sensor, and the fifth angle sensor are set from the blade root side, and the angles measured in the X direction are 0, theta_x1, theta_x2, theta_x3, and theta_x4, respectively, and the angles measured in the Y direction are 0, theta_y1, theta_y2, theta_y3, and theta_y4, respectively.

[0049] Since the arrangement interval between two sensors is known.

[0050] The position relative coordinates (xn, yn, zn) of the next angle sensor can be approximately calculated from the following formula with the coordinates of the previous angle sensor as the reference:

[0051] Nn=Ln-L(n-1)

[0052] xn=Nn*tan(theta_x(n-1))

[0053] yn=Nn*tan(theta_y(n-1))

[0054] zn=Nn

[0055] where Nn is the projection position of the nth angle sensor on the Z axis, n=1, 2, 3, 4, 5; Ln is the arrangement interval between the next angle sensor and the previous angle sensor, i.e., the arrangement interval between the nth and the (n-1)th angle sensors; L(n-1) is the arrangement interval of the previous angle sensor.

[0056] Therefore, knowing the position relative coordinates of the previous angle sensor as the reference, and adding the three-dimensional coordinate system absolute coordinates of the previous angle sensor, the absolute coordinates of the position of the next angle sensor can be obtained, as shown in Figure 7

[0057] ​​a1(x,y,z) = [0, 0, 0]

[0058] a2(x,y,z) = a1(x,y,z) + [N2 x tan(theta_x1), N2 x tan(theta_y1), N2]

[0059] a3(x,y,z) = a2(x,y,z) + [N3 x tan(theta_x2), N3 x tan(theta_y2), N3]

[0060] a4(x,y,z) = a3(x,y,z) + [N4 x tan(theta_x3), N4 x tan(theta_3), N4]

[0061] a5(x,y,z) = a4(x,y,z) + [N5 x tan(theta_x4), N5 x tan(theta_y4), N5]

[0062] In the formula, a1(x,y,z), a2(x,y,z), a3(x,y,z), a4(x,y,z), a4(x,y,z) are coordinates of the 1st-5th angle sensors respectively; wherein a6(x,y,z) is assumed to be a tip coordinate, since a6(x,y,z) and a5(x,y,z) are relatively close, it can be approximately considered that their angle changes are almost the same, and a6(x,y,z) should be slightly larger than a5(x,y,z), which can be obtained by measuring the rigidity difference during production and multiplying a correction coefficient to obtain more accurate deformation, as shown in the following formula:

[0063] theta_x6 = theta_x5 x K_x

[0064] theta_y6 = theta_y5 x K_y

[0065] a6(x,y,z) = a5(x,y,z) + [N6 x tan(theta_x5), N6 x tan(theta_y6), N_6]

[0066] In the formula, theta_x5 is the angle measured in the X direction of the tip, K_x is the correction coefficient in the X direction of the tip, theta_y5 is the angle measured in the Y direction of the tip, K_y is the correction coefficient in the Y direction of the tip, and N6 is the projection position of the tip on the Z axis.

[0067] Similarly, during installation in the workshop, further calibration and debugging can be performed according to the controllable conditions on site to obtain more accurate deformation data. The corresponding mapping relationship between the angle and the deformation can also be obtained through computer simulation.

[0068] The above embodiments are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications, etc. made without departing from the spirit and principles of the present application should be equivalent replacement manners and should be included in the protection scope of the present application.

Claims

1. A wind turbine blade deformation condition monitoring method, characterized by, The following operations are performed: A plurality of angle sensors are arranged in order from the blade root side to the blade tip side on the middle axis of the blade web with the blade root end as the starting reference, and two adjacent angle sensors are connected by a flexible cable. Since the middle axis of the blade web is not in a straight line, the angle sensors form an azimuth angle due to the tensioned cable; When the blade is deformed, the angle sensors will displace, thereby changing the direction of the cable. By the azimuth angle and the position information of the angle sensors, the deformation posture of the blade can be obtained. The deformation posture of the blade can be described by the three-dimensional coordinate system (x, y, z) of each angle sensor, wherein the three-dimensional coordinate system (x, y, z) of the angle sensor takes the Z-axis of the blade root coordinate system as the reference axis direction, the blade chord length as the Y-axis direction, and the direction perpendicular to the blade chord length as the X-axis direction. The deformation of the blade in the X direction is the largest, followed by the Y direction. The blade on the axis will deform in the lengthening direction, but the deformation amount is the smallest and the influence is also the smallest, so it is ignored. The specific process is as follows: The projection coordinates of the angle sensor installation position on the Z-axis are known. The corresponding plane coordinates are calculated in the same plane by the azimuth angle and the geometric relationship. The XZ plane and the ZY plane are perpendicular to each other. The position information of the angle sensor in the three-dimensional coordinates of the blade can be obtained by combining the coordinates of the two planes. Finally, the deformation posture of the blade can be obtained according to the position information. The angle sensor is a non-contact Hall sensor, which includes a base, a rotating ring, a rotating half ring, a two-dimensional Hall sensor, and a magnet. The base is fixedly connected with the blade web. The rotating ring is installed on the base by a first pin shaft and can rotate around the first pin shaft. The rotating half ring is installed on the rotating ring by a second pin shaft and can rotate around the second pin shaft. The rotating ring and the rotating half ring together form two rotation degrees of freedom perpendicular to each other, realizing free rotation in a large direction. One end of the rotating half ring forms a first mounting position for connecting the cable. The base forms a second mounting position for connecting the cable. The other end of the rotating half ring is provided with a magnet for generating a magnetic field. The two-dimensional Hall sensor is installed on the base and located at the center of the rotating ring and the rotating half ring. The two-dimensional Hall sensor can measure the change of magnetic flux, thereby calculating the azimuth angle of the X and Y directions of the magnet.

2. A wind turbine blade deformation condition monitoring method according to claim 1, characterized in that: A cable connecting point is installed on the middle axis of the blade web between the last angle sensor and the blade tip, for connecting the last angle sensor.

3. A wind turbine blade deformation condition monitoring method according to claim 2, characterised in that: The angle sensors installed on the middle axis of the blade web are set to n, including the first angle sensor, the second angle sensor, and the nth angle sensor from the blade root side. The measured angles in the X direction are 0, theta_x1, theta_x2, …, theta_x(n-1), respectively. The measured angles in the Y direction are 0, theta_y1, theta_y2, …, theta_y(n-1), respectively. The arrangement interval between two angle sensors is known. The position relative coordinates (xn, yn, zn) of the next angle sensor are approximately calculated by the following formulas when the coordinates of the previous angle sensor are taken as the reference: Nn = Ln - L(n-1) xn = Nn tan(theta_x(n-1)) yn = Nn tan(theta_y(n-1)) zn = Nn In the formulas, Nn is the projection position of the nth angle sensor on the Z axis; Ln is the arrangement interval between the next angle sensor and the previous angle sensor, i.e., the arrangement interval between the nth and (n-1)th angle sensors; L(n-1) is the arrangement interval of the previous angle sensor. Therefore, the position absolute coordinates of the next angle sensor can be obtained by taking the position relative coordinates of the previous angle sensor as the reference and adding the three-dimensional coordinate system absolute coordinates of the previous angle sensor, so that the blade space position is calculated as follows: a1(x,y,z) = [0,0,0], a2(x,y,z) = a1(x,y,z)+[N2 tan(theta_x1), N2 tan(theta_y1), N2], a3(x,y,z) = a2(x,y,z)+[N3 tan(theta_x2), N3 tan(theta_y2), N3],…, an(x,y,z) = a(n-1)(x,y,z)+[Nn tan(theta_x(n-1)), Nn tan(theta_y(n-1)), Nn]; In the formulas, a1(x,y,z), a2(x,y,z), and a3(x,y,z) are the coordinates of the 1st, 2nd, and 3rd angle sensors, respectively, and an(x,y,z) is the coordinate of the nth angle sensor; a(n+1)(x,y,z) is assumed to be the blade tip coordinate, which is close to an(x,y,z) and can be approximately considered to have the same angle change, and a(n+1)(x,y,z) should be larger than an(x,y,z). By measuring the rigidity difference during production and multiplying a correction coefficient, a more accurate deformation can be obtained, as shown in the following formulas: theta_xn = theta_x(n-1) K_x theta_yn = theta_y(n-1) K_y a(n+1)(x,y,z) = an(x,y,z)+[N(n+1) tan(theta_xn), N(n+1) tan(theta_yn), N(n+1)]; In the formulas, theta_xn is the measured angle of the blade tip in the X direction, K_x is the correction coefficient of the blade tip in the X direction, theta_yn is the measured angle of the blade tip in the Y direction, K_y is the correction coefficient of the blade tip in the Y direction, and N(n+1) is the projection position of the blade tip on the Z axis.

4. A wind turbine blade deformation condition monitoring method according to claim 1, characterized in that: The non-contact Hall sensor adopts a non-magnetic material to avoid interference with the magnetic field.

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