A test method for identifying wind turbine blade attribute parameters

Abstract

The present invention relates to a test method for identifying the attribute parameters of wind turbine blades. The method comprises: obtaining the bending moment, deflection, and strain of each section of the blade under the action of a loading force through a static loading test, and establishing a relationship between the bending moment and strain in the static test; obtaining the stiffness of each section of a variable-section blade through mathematical solution based on the relationship between bending moment, deflection, and section stiffness in structural mechanics; obtaining parameters such as the amplitude, strain, and frequency of each section of the blade through a fatigue loading test, establishing a relationship between strain and amplitude in the fatigue test, and inferring the mass distribution of the blade based on vibration theory. Compared with existing inventions, the present invention obtains the actual attribute parameters of the blade through static and fatigue testing of the blade, calibrates the errors in the theoretical model, and uses this as a basis for performing bending moment matching and loading control in the blade fatigue test, effectively reducing the load error of the fatigue test and improving the accuracy of the blade test.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power generation, and in particular to a testing method for identifying attribute parameters of wind turbine blades. Background Art

[0002] Before being put into use, wind turbine blades usually need to undergo full-scale static loading tests and fatigue loading tests. The static loading test is to apply loading forces to the blades at multiple points. Under the action of the loading forces, the blades produce corresponding static deformations to test the static strength of the blades. The fatigue loading test uses an exciter to excite the blades, and the blades need to undergo millions of fatigue vibrations. Due to the complexity of the blade cross-sectional shape and layer structure, as well as human errors in the manufacturing process, there are often some differences between the actual manufactured blade cross-sectional stiffness and mass distribution and the theoretical values, and the existing blade cross-sectional stiffness calculation method also has the problem of large errors. These problems will make it difficult for the actual fatigue test load to match the design value, which may cause premature damage to the blades or incomplete testing of the blade fatigue performance.

[0003] To solve the above problems, the invention patent with authorization number CN113029479B proposes a full-size blade stiffness detection method, electronic equipment and storage medium. The method includes: placing the blade to be detected on a support platform, setting a number of test points in the verification area of ​​the blade to be detected; measuring the deflection of each of the test points; establishing a blade deflection curve function based on the deflections of all the test points; using the blade deflection curve function to obtain the measured curvature of the blade cross section at each of the test points, and comparing the measured curvature with the theoretical curvature of each corresponding cross section of the blade to be tested to obtain the detection result. In fact, when the blade is stationary on the support platform, the blade segment between the two support platforms basically does not deform. Therefore, this method has high measurement requirements and is prone to inaccurate measurements. In addition, the theoretical mass linear density of the blade needs to be used when solving the blade shear force, which will also cause calculation errors. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a test method for identifying the attribute parameters of wind turbine blades. The present invention takes into account the shortcomings of existing blade testing methods and existing testing means, and realizes a test method that can identify blade mode, stiffness distribution, and blade mass distribution.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A test method for identifying attribute parameters of a wind turbine blade comprises the following steps:

[0007] S1. Conduct a full-scale static loading test on the blade. Based on the deformation of the blade under the loading force, calculate the bending moment of each section of the blade, measure the deflection and strain of each section of the blade, and establish the corresponding relationship between the bending moment and strain at each section of the blade;

[0008] S2. Based on the bending moment and deflection of each section of the blade obtained in step S1, and according to the relationship between bending moment, deflection and section stiffness in structural mechanics, a mathematical method is used to inversely calculate the section stiffness of each section of the variable-section blade;

[0009] S3. Perform a full-scale fatigue loading test on the blade. This involves using a vibrator to resonate and vibrate the blade. Parameters such as amplitude, strain, and resonant frequency are measured at each blade section, establishing a corresponding relationship between strain and amplitude at each blade section during the fatigue test.

[0010] S4. Based on the correspondence between the strain and amplitude at each section of the blade in the fatigue test obtained in step S3, combined with the correspondence between the bending moment and strain at each section of the blade established in the static test in step S1, a correspondence between the amplitude and bending moment in the fatigue test is further established. According to the calculation formula of the blade bending moment in the fatigue test, the mass of each section of the blade is obtained by reverse deduction.

[0011] Furthermore, in step S1, the static loading test includes single-point loading or multi-point loading, and can cause measurable deformation of the blade.

[0012] Furthermore, in step S1, the static loading test needs to measure and calculate the angle between the loading force and the normal direction of the blade section when the blade is deformed, so as to reduce the static bending moment calculation error.

[0013] Furthermore, in step S1 , static loading tests need to be performed in the swinging direction and the shimmying direction respectively.

[0014] Furthermore, in step S2, according to the relationship between bending moment, stiffness and deflection in material mechanics, if the finite difference method is used, the cross-sectional stiffness EI of each cross-sectional area of ​​the variable cross-sectional blade is obtained. i The expression is:

[0015]

[0016] Where h is the distance between each section, M i is the bending moment of each section of the blade, y i is the deflection of each section of the blade, and i is the section number.

[0017] Furthermore, in step S2, according to the relationship between bending moment, stiffness and deflection in structural mechanics, if the direct integration and difference method is used, the cross-sectional stiffness EI of each cross-sectional area of ​​the variable cross-sectional blade is obtained. i The expression is:

[0018]

[0019] Where P is the loading force in static calibration; L is the loading point position; C1 and C2 are the solution coefficients; y i is the deflection of each section of the blade, i is the section number, x i is the length of the i-th section from the blade root.

[0020] Furthermore, in step S3, the amplitude of each section of the blade is measured by a displacement sensor;

[0021] The displacement sensors are distributed on each main cross section of the blade, and the number of the displacement sensors is at least sufficient to fit the modal vibration shape of the blade.

[0022] Furthermore, in step S3, the resonance frequency at each cross section of the blade is obtained by performing frequency domain or time domain analysis on the amplitude or strain.

[0023] Furthermore, in step S4, the blade bending moment calculation formula in the fatigue test is expressed as:

[0024]

[0025] Where M i is the bending moment value of the i-th section of the blade in the fatigue test, m k is the mass of the kth section of the blade, ω is the resonance frequency, Y k is the amplitude at the mass center of the kth blade section during fatigue testing, L k -L i is the relative distance from the mass center of the kth section to the i-th section, and n is the number of blade sections.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention can utilize the test process required for full-scale structural testing of blades to obtain blade-related parameters without the need for additional test processes. Accurate measurement results can be obtained under low test requirements.

[0028] 2. The present invention can identify the actual stiffness distribution of the blade in a static test, and can identify the actual mass distribution of the blade and the modal characteristics of the blade in a fatigue test.

[0029] 3. The test method provided by the present invention can more accurately reflect the actual properties of the blade, and use it as a basis for blade fatigue test bending moment matching and loading control, effectively reducing the load error of the fatigue test, which is conducive to improving the test accuracy of blade bending moment matching in fatigue testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of the present invention;

[0031] Figure 2 Schematic diagram of static loading of blades in an embodiment of the present invention;

[0032] Figure 3 Schematic diagram of bending moment distribution during blade fatigue test in an embodiment of the present invention;

[0033] Figure 4 Schematic diagram of polynomial fitting for static measurement deflection of blades in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] like Figure 1 As shown, the test method steps for identifying wind turbine blade attribute parameters in embodiment 1 of the present invention are as follows:

[0037] S1: First, perform a full-scale static loading test on the blade, such as Figure 2 As shown in Figure 1, under the action of a single or multi-point tension, the blade will produce corresponding deformation. In this case, the bending moment M of each section of the blade can be calculated by the applied tension and the relative distance. i The deflection y of each section of the blade is obtained by total station measurement i , the strain S of each section of the blade is measured by strain gauge i , establish the bending moment M at each section i and strain S i In addition, it is necessary to perform polynomial fitting and smoothing on the deflection values ​​measured at each section of the blade to reduce human measurement errors, such as Figure 4 In this step, static loading tests need to be performed in both the flapping and shimmying directions.

[0038] S2: The blade is then subjected to a full-scale fatigue loading test, e.g. Figure 3As shown, an exciter is used to resonate the blade, causing it to vibrate. The blade's modal information can be measured using an accelerometer or strain gauge to obtain the blade's resonant frequency ω. In addition, the accelerometer can be used to measure the amplitude Y of each section of the blade during vibration. i Signal.

[0039] S3: The bending moment M of each section of the blade obtained in step S1 i and deflection y i According to the relationship between bending moment, stiffness and deflection in material mechanics, the finite difference method can be used to inversely calculate the section stiffness EI of each section of the blade. i .

[0040] According to the differential formula of the second-order differential in material mechanics:

[0041]

[0042] We can get:

[0043] Section 1: y0-2y1+y2=A1

[0044] Section 2: y1-2y2+y3=A2

[0045]

[0046] Section i:y i-1 -2y i +y i+1 =A i

[0047]

[0048] Section n-1: y n-2 -2y n-1 +y n =A n-1

[0049] Where A i The expression is:

[0050]

[0051] h is the distance between each section.

[0052] The stiffness of each section can be further obtained as:

[0053]

[0054] S4: According to the amplitude Y of each section of the blade obtained in step S2 i and strain S i Information can be used to establish the amplitude Yi and strain S i The corresponding relationship between them, and then according to the bending moment M in step S1 i and strain S i The relationship between the amplitude Y in fatigue test can be further established. i and bending moment M i The relationship between the blade and the amplitude data measured by the acceleration sensor can be used to know the bending moment of the blade. According to the bending moment formula of the blade in the fatigue test, the mass m of each blade segment can be calculated. i .

[0055] The bending moment in fatigue testing is calculated as follows:

[0056]

[0057] The mass of segment n is:

[0058]

[0059] The mass of segment n-1 is:

[0060]

[0061]

[0062] According to the above calculation method, the mass of each section of the blade can be calculated in sequence starting from the blade tip.

[0063] Example 2:

[0064] The main difference between this embodiment and the first embodiment lies in step S1, which is modified as follows:

[0065] S1: First, the static calibration test during the fatigue test can be used to calculate the bending moment M of each section of the blade by applying the tension and the relative distance. i The strain S of each section of the blade can be measured by strain gauges. i , establish the bending moment M at each section i and strain S i In the static calibration test, the deflection y of each section before and after blade deformation can be directly calculated by the image recognition algorithm. i Because the image recognition solution does not require manual coordinate measurement of each blade section using a total station, there is no need to fit or smooth the measured deflection. The image recognition algorithm needs to be able to measure the three-dimensional deflection changes of the blade to improve measurement accuracy.

[0066] S2: Then the blade is subjected to full-scale fatigue loading test, such as Figure 3As shown, an exciter is used to resonate the blade, causing it to vibrate. The blade's modal information can be measured using an accelerometer or strain gauge to obtain the blade's resonant frequency ω. In addition, the accelerometer can be used to measure the amplitude Y of each section of the blade during vibration. i Signal.

[0067] S3: The bending moment M of each section of the blade obtained in step S1 i and deflection y i According to the relationship between bending moment, stiffness and deflection in structural mechanics, the cross-sectional stiffness EI of each section of the blade can be directly calculated by integrating and subtracting. i .

[0068] According to the second-order derivative differential formula of deflection in material mechanics:

[0069]

[0070] Taking the second-order integral derivative of the above equation, we can get the deflection curve equation y(x) of the variable-section blade:

[0071]

[0072] Select the deflection parameters of the front and back sections of the i-th section and make the difference, and we can get:

[0073]

[0074]

[0075] From the above two equations, we can get the stiffness EI of the i-th section: i :

[0076]

[0077] Where P is the loading force in static calibration; L is the loading point position; C1 and C2 are the solution coefficients; x i is the length of the i-th section from the blade root.

[0078] S4: As described in Example 1.

[0079] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A test method for identifying attribute parameters of wind turbine blades, characterized in that: The following steps are involved: S1. Conduct a full-scale static loading test on the blade. Based on the deformation of the blade under the loading force, calculate the bending moment of each section of the blade, measure the deflection and strain of each section of the blade, and establish the corresponding relationship between the bending moment and strain at each section of the blade; S2. Inversely calculate the section stiffness of each section of the variable-section blade based on the bending moment and deflection of each section of the blade obtained in step S1; S3. Perform a full-scale fatigue loading test on the blade to put it in a vibrating state, measure the amplitude, strain, and resonant frequency at each section of the blade, and establish a corresponding relationship between the strain and amplitude at each section of the blade during the fatigue test; S4. Based on the correspondence between the strain and amplitude at each section of the blade in the fatigue test obtained in step S3, combined with the correspondence between the bending moment and strain at each section of the blade established in the static test in step S1, a correspondence between the amplitude and bending moment in the fatigue test is further established. According to the calculation formula of the blade bending moment in the fatigue test, the mass of each section of the blade is obtained by reverse deduction.

2. A test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S1, the static loading test includes single-point loading or multi-point loading, and can cause the blade to undergo measurable deformation.

3. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S1, the static loading test needs to measure and calculate the angle between the loading force and the normal direction of the blade section when the blade is deformed, so as to reduce the calculation error of the static bending moment.

4. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S1, static loading tests need to be performed in the swinging direction and the shimmying direction respectively.

5. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S2, according to the relationship between bending moment, stiffness and deflection in material mechanics, if the finite difference method is used, the cross-sectional stiffness EI of each cross-sectional area of ​​the variable cross-sectional blade is obtained. i The expression is: Where h is the distance between each section, M i is the bending moment of each section of the blade, y i is the deflection of each section of the blade, and i is the section number.

6. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S2, according to the relationship between bending moment, stiffness and deflection in structural mechanics, if the direct integration and difference method is used, the cross-sectional stiffness EI of each cross-sectional area of ​​the variable cross-sectional blade is obtained. i The expression is: Where P is the loading force in static calibration; L is the loading point position; C1 and C2 are the solution coefficients; y i is the deflection of each section of the blade, i is the section number, x i is the length of the i-th section from the blade root.

7. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S3, the amplitude of each section of the blade is measured by a displacement sensor; The displacement sensors are distributed on each main cross section of the blade, and the number of the displacement sensors is at least sufficient to fit the modal vibration shape of the blade.

8. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S3, the resonance frequency at each cross section of the blade is obtained by performing frequency domain or time domain analysis on the amplitude or strain.

9. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S4, the blade bending moment calculation formula in the fatigue test is expressed as: Where M i is the bending moment value of the i-th section of the blade in the fatigue test, m k is the mass of the kth section of the blade, ω is the resonance frequency, Y k is the amplitude at the mass center of the kth blade section during fatigue testing, L k -L i is the relative distance from the mass center of the kth section to the i-th section, and n is the number of blade sections.

10. The test method for identifying attribute parameters of wind turbine blades according to claim 1, characterized in that: In step S3, the fatigue loading test uses an exciter to resonate the blade to put the blade in a vibrating state.

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