CN115076026A - Wind generating set blade root load strain gauge calibration calculation method considering installation deflection angle - Google Patents

Abstract

The invention discloses a wind generating set blade root load strain gauge calibration calculation method considering an installation deflection angle, which comprises the following steps of: s1: setting a strain gauge, determining an installation deflection angle, and calibrating shimmy load data and waving load data; s2: constructing a calibration equation, and determining a calibration slope matrix and a calibration offset matrix; s3: and obtaining the actual slope and the offset based on the installation deflection angle and the calibration equation. The invention has the beneficial effects that: in the calibration calculation, the installation deflection angle of the blade root strain gauge is taken into consideration, and the converted blade root load is closer to the reality through the decomposition and synthesis of the actually measured load signal.

Description

Calibration calculation method of wind turbine blade root load strain gauge considering installation deflection angle

technical field

The invention relates to the technical field of wind turbine mechanical load testing, in particular to a calibration calculation method for a wind turbine blade root load strain gauge considering the installation deflection angle.

Background technique

The blade of a wind turbine is a component that absorbs and converts wind energy into mechanical energy, and is one of the most critical components in a wind turbine. Because the blade root is the most significant area for external bending moments, the measurement of blade load is usually carried out at the blade root. The test of the blade root bending moment of the wind turbine includes the test of the blade root swing bending moment and the sway bending moment. The blade root load test sensor generally uses a resistance strain gauge, and a full bridge circuit is established to measure the swing and sway bending moments respectively.

In the prior art, IEC61400-13 provides a calibration correction method for the problem of signal crosstalk generated in blade load measurement swing and swing direction, which considers that the signal crosstalk in blade load measurement cannot be ignored, and the actual swing bending moment The swaying moment is not only related to the corresponding load signal, that is, the swaying moment needs to consider the influence of the swaying load signal when correlating it with the swaying load signal, and the swaying moment needs to be considered when correlating the swaying load signal. The effect of the shimmy load signal. Finally, through a series of matrix transformations, the calibration coefficient and offset in the calibration equation can be obtained. The calibration equation obtained by the above method can sometimes not eliminate the influence of crosstalk well, thus affecting the load calculation. This is because the blades used by different units are different, and the size of the local area of unstable stress near the clamping seam is also different, and the installation deflection angle θ of the strain gauge is often determined by experience, and there is no unified conclusion. In view of the above problems, the installation deflection angle of the strain gage should be taken into account in the calibration calculation process of the blade strain signal of the unit.

For example, a "FBG-based fan blade load measurement method and application" disclosed in Chinese patent documents, its announcement number: CN112665766A, its application date: December 19, 2020, the invention uses the blade equivalent rigidity The mapping relationship between the coefficient matrix, the output wavelength change value of the sensor group and the load value corresponding to the blade pitch angle, to obtain the specific value of the calibrated blade equivalent rigidity coefficient matrix, and measure the output wavelength change value of the sensor group in real time. After calibration, the specific value of the blade equivalent rigidity coefficient matrix, the initial load value of the blade and the output wavelength change value of the sensor group can obtain the real-time load value of the blade. Quantities differ from actual data.

SUMMARY OF THE INVENTION

Aiming at the deficiencies that the installation deflection angle of the blade root strain gauge is not considered in the calibration calculation of the prior art, and the blade root load is different from the actual data, the present invention proposes a wind turbine blade root load strain gauge calibration calculation method considering the installation deflection angle , in the calibration calculation, the installation deflection angle of the blade root strain gauge is taken into account, and through the decomposition and synthesis of the measured load signal, the converted blade root load is closer to reality.

The following is the technical solution of the present invention, considering the installation angle of the wind turbine blade root load strain gauge calibration calculation method, including the following steps:

S1: Set the strain gauge, determine the installation deflection angle, calibrate the sway load data and the swing load data;

S2: Construct the calibration equation, determine the calibration slope matrix and the calibration offset matrix;

S3: Obtain the actual slope and offset based on the installation declination and calibration equation.

In this scheme, set the strain gauge, determine the installation deflection angle, calibrate the sway load data and the swing load data, construct the calibration equation, determine the calibration slope matrix and the calibration offset matrix, and obtain the actual slope and For the offset, the installation deflection angle of the blade root strain gauge is taken into account in the calibration calculation, and the converted blade root load is closer to reality by decomposing and synthesizing the measured load signal.

Preferably, the strain gauge is installed on the inner wall of the cylindrical section of the blade root, and the four measuring points are evenly distributed on the quarter points of the circular section of the cylindrical section of the blade root.

In this scheme, the strain gage is installed on the inner wall of the cylindrical section of the blade root, and the four measuring points are evenly distributed on the quarter points of the circular section of the cylindrical section of the blade root, which is convenient for the strain gage to swing the bending moment of the blade root and the blade root. The sway bending moment is measured.

Preferably, the connecting lines of two non-adjacent strain gauges are perpendicular to each other.

In this scheme, in order to avoid the clamping seam area where the local stress is very unstable, the second strain gage and the fourth strain gage have an installation angle with the swing direction when they are arranged. When the first strain gauge and the third strain gauge are arranged, the connection line between the two should be kept perpendicular to the connection line between the second strain gauge and the fourth strain gauge, that is, the connection line between the first strain gauge and the third strain gauge is the same as the swing direction. installation angle.

Preferably, the wind generator set is in a shutdown state during calibration, and the minimum number of cycles for the free rotation of the wind rotor is three cycles.

In this scheme, the wind turbine is in a shutdown state during calibration, and the minimum number of cycles for the free rotation of the wind rotor is three cycles, which improves the measurement accuracy of the strain gauge during calibration.

Preferably, there are three blades in total during calibration, one blade has a pitch angle of 0 degrees, the other blade has a pitch angle of 90 degrees, and the third blade pitch angle is set to any value from 0 to 90 degrees .

In this scheme, the swing direction of the blade with a pitch angle of 90 degrees is completely exposed to the action of gravity, and the swing direction of the blade with a pitch angle of 0 degrees is completely exposed to the action of gravity, which improves the measurement accuracy of the strain gauge during calibration.

Preferably, the wind speed during calibration is 3-4m/s.

In this scheme, the wind speed during calibration is 3-4m/s, which improves the measurement accuracy of the strain gauge during calibration.

Preferably, the calibration equation is as follows:

初始标定斜率矩阵，

初始标定偏移量矩阵。In the above formula, S _e and S _f are the load signals in the swing and swing directions, respectively, M _be and M _bf are the calibrated loads,

initial calibration slope matrix,

Initial calibration offset matrix.

Preferably, the formula for the initial calibration slope is as follows:

为空转过程中摆振载荷信号的平均值，

为空转过程中挥舞载荷信号的平均值，slope_e、slope_f为初始标定斜率。α _e , α _f are the cabin elevation angles, β _e , β _f are the blade cone angles,

is the average value of the swing load signal during the idling process,

is the average value of the swing load signal during the idling process, slope _e and slope _f are the initial calibration slopes.

As a preference, due to the existence of the installation deflection angle, the blade root swing bending moment _Me is actually the projected vector sum of the nominal loads M _be and M _bf in the swing direction; similarly, the blade root swing bending moment M _f is actually the projected vector sum of the calibrated load quantities M _be and M _bf in the swing direction, and the expression is as follows:

Me = M _be · _cosθ +M _bf ·sinθ,

M _f =-M _be ·sinθ+M _bf ·cosθ,

Combined with the calibration equation, the following formula is obtained:

In the above formula, S _e and S _f are the load signals in the swing and swing directions, respectively, M _be and M _bf are the load amounts obtained by calibration, slope _e and slope _f are the initial calibration slopes, and offset _e and offset _f are the initial calibration slopes. Calibration offset.

In this scheme, the slope and offset are obtained from the installation deflection angle, sway load data, and swing load data.

The beneficial effect of the invention is that: in the calibration calculation, the installation deflection angle of the blade root strain gauge is taken into account, and the converted blade root load is closer to reality by decomposing and synthesizing the measured load signal; when using IEC61400- When the calibration method provided in 13 does not consider the installation angle for calculation, this method can be used to verify whether the calibration coefficient calculated by the IEC method is incorrect. If the calibration coefficient calculated by the IEC method is basically similar to the calibration coefficient calculated by this method, the calibration result calculated by the IEC method can be used for subsequent load analysis.

Description of drawings

Fig. 1 is a flow chart of the calibration calculation method of the blade root load and strain gauge of the wind turbine considering the installation deflection angle of the present invention.

Fig. 2 is a schematic diagram of the installation of the blade root strain gage of the wind turbine blade root load strain gage calibration calculation method considering the installation deflection angle according to the present invention.

Fig. 3 is a side view of the installation of the blade root strain gage of the method of the present invention for the calibration calculation method of the blade root load strain gage of the wind turbine that considers the installation deflection angle.

4 is a schematic diagram of the pitch angle of three blades during the calibration test process of the wind turbine blade root load strain gauge calibration calculation method considering the installation deflection angle of the present invention.

5 is a schematic diagram of the variation of the blade root sway and swing moment load signals of a single blade with the azimuth angle of the wind rotor during the calibration process of the wind turbine blade root load strain gauge calibration calculation method considering the installation deflection angle of the present invention.

6 is a schematic diagram of decomposition and synthesis of the measured load signal of the method of the present invention for the calibration calculation method of the blade root load and strain gauge of the wind turbine that considers the installation deflection angle.

FIG. 7 is a detailed flow chart of the method for calculating the calibration and calculation of the blade root load and strain gauge of the wind turbine in consideration of the installation deflection angle according to the present invention.

Detailed ways

The technical solutions of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

Example: As shown in Figures 1 to 7, the calculation method for the calibration and calculation of the blade root load and strain gauge of the wind turbine generator set considering the installation deflection angle includes the following steps:

S1: Set the strain gauge, determine the installation deflection angle, calibrate the sway load data and the swing load data.

S2: Construct the calibration equation, and determine the calibration slope matrix and the calibration offset matrix.

S3: Obtain the actual slope and offset based on the installation declination and calibration equation.

As shown in Figures 2 and 3, the strain gauge used to measure the bending moment of the blade root is installed on the inner wall of the cylindrical section of the blade root, and the four measuring points are evenly distributed on the quarter points of the circular section of the cylindrical section of the blade root. . The first strain gage and the third strain gage group of the full bridge measure the blade root swing bending moment, and the second strain gage and the fourth strain gage group full bridge measure the blade root swing bending moment. As shown in Figure 2, in order to avoid the clamping seam area where the local stress is very unstable, the second strain gage and the fourth strain gage have an installation angle θ with the swing direction when they are arranged. Influence, when the first strain gauge and the third strain gauge are arranged, the connection line between the two should be kept perpendicular to the connection line between the second strain gauge and the fourth strain gauge, that is, the connection line between the first strain gauge and the third strain gauge and the swinging The same mounting declination θ exists in the direction. In the actual test, the above strain gauges are arranged on the roots of the three blades of the wind turbine for blade root load measurement.

After the installation and arrangement of the strain gages are completed, after the main control program of the wind turbine is modified, the pitch angles of different blades are adjusted in the shutdown mode of the unit, so that the wind rotor is idling, and then the blade root swing and waving bending moment are adjusted. Calibration, the idling of the wind rotor refers to the process in which the wind rotor rotates freely when the wind turbine is in a shutdown state. The minimum number of idling cycles of the wind rotor during the calibration process is three cycles. The calibration test needs to be carried out under light wind conditions, and the wind speed is 3-4m/s. As shown in Figure 4, the first blade is not propelled, that is, the pitch angle is 90°. The second blade and the third blade are opened to 30° and 0° respectively. When the wind rotor starts to rotate, the swing direction of the first blade is completely exposed to the action of gravity, and the swing direction of the third blade is completely exposed to the action of gravity. When the wind rotor rotates slowly for three times, the calibration test of the load signal in the swing direction of the first blade and the vibration direction of the third blade is completed. According to the same method, the load signal calibration test of the first blade, the second blade and the third blade in the swing and swing directions is finally completed.

In the calibration test, the pitch angle of one of the three blades must be 0 degrees, the pitch angle of the other blade must be 90 degrees, and the third blade can be set to any value from 0 to 90 degrees.

During the calibration process, it is also possible to modify the unit control program to reduce the cut-in wind speed parameter of the unit, so that the wind turbine starts when the cut-in wind speed is less than the cut-in wind speed. Calibration of the load signal in the blade root swing direction. After the rotor rotates slowly for three times, manually stop and restore the parameters.

S2: Construct the calibration equation, and determine the calibration slope matrix and the calibration offset matrix.

挥舞载荷信号的平均值

During the calibration process, the signal waveforms of single blade root sway and flapping moment load are similar to sinusoidal functions. By extracting the maximum and minimum values of all blade load signal waveforms, the average value of each blade's swing load signal during idling is calculated

Average value of swing load signal

The initial calibration equation is as follows:

初始标定斜率矩阵，

初始标定偏移量矩阵。In the above formula, S _e and S _f are the load signals in the swing and swing directions, respectively, M _be and M _bf are the calibrated loads,

initial calibration slope matrix,

Initial calibration offset matrix.

When the wind rotor is idling for several cycles, S _e and S _f will obtain a signal waveform similar to a sine function.

Slope _e and slope _f are obtained by calculation, and the formula is as follows:

为空转过程中摆振载荷信号的平均值，

为空转过程中挥舞载荷信号的平均值，slope_e、slope_f为初始标定斜率。In the above formula, F _e and F _f are the gravity generated by the blade at the position of the centroid (F _e =F _f ), and _Le and L _f are the distance between the centroid of the blade and the patch position (L _e =L _f ), α _e and α _f are the nacelle elevation angles (α _e =α _f ), and β _e and β _f are the blade cone angles (β _e =β _f ).

is the average value of the swing load signal during the idling process,

is the average value of the swing load signal during the idling process, slope _e and slope _f are the initial calibration slopes.

Offset _e is equal to the product of -slope _e and the difference between the maximum value and the minimum value of the sway bending moment signal during one cycle of idling of the rotor. Since the rotor has been idling for at least three weeks, Offset _e should be averaged.

Similarly, Offset _f is equal to the product of -slope _f and the difference between the maximum value and the minimum value of the waving bending moment signal during one cycle of idling of the rotor. Since the rotor has been idling for at least three weeks, Offset _f should be averaged.

S3: Obtain the actual slope and offset based on the installation declination and calibration equation.

Due to the existence of the installation deflection angle θ, the blade root swing bending moment _Me is actually the projected vector sum of the nominal loads M _be and M _bf in the swing direction; similarly, the blade root swing bending moment M _f In fact, it is the projected vector sum of the nominal load values M _be and M _bf in the swing direction. The expression is as follows:

Me = M _be · _cosθ +M _bf ·sinθ (4)

M _f = -M _be ·sinθ+M _bf ·cosθ (5)

Rewriting equations (4) and (5) into matrix form, the expressions are as follows:

Substitute equation (1) into equation (6) to obtain equation (7), as follows:

Further simplification yields formula (8):

According to equations (7) and (8), the slope and offset are calculated:

K ₁₁ =cosθ·slope _e (9)

K ₁₂ =sinθ·slope _f (10)

K ₂₁ =-sinθ·slope _e (11)

K ₂₂ =cosθ·slope _f (12)

OFFSET _e =cosθ·offset _e +sinθ·offset _f (13)

OFFSET _f = -sinθ·offset _e +cosθ·offset _f (14)

In the calibration calculation, the installation deflection angle of the blade root strain gauge is taken into account, and the converted blade root load is closer to reality by decomposing and synthesizing the measured load signal; When calculating with the calibration method of the angle, this method can be used to verify whether the calibration coefficient calculated by the IEC method is correct. If the calibration coefficient calculated by the IEC method is basically similar to the calibration coefficient calculated by this method, the calibration result calculated by the IEC method can be used for subsequent load analysis.

Claims (9)

1. consider the wind turbine blade root load strain gauge calibration calculation method of installation deflection angle, it is characterized in that, comprise the following steps: S1: Set the strain gauge, determine the installation deflection angle, calibrate the sway load data and the swing load data; S2: Construct the calibration equation, determine the calibration slope matrix and the calibration offset matrix; S3: Obtain the actual slope and offset based on the installation declination and calibration equation. 2. The method for calibrating and calculating the blade root load strain gauge of a wind turbine according to claim 1, wherein the strain gauge is installed on the inner wall of the blade root cylindrical section, and the four measuring points are evenly distributed on the On the quarter point of the circular section of the cylindrical segment of the blade root. 3 . The method for calibrating and calculating the load strain gauge at the blade root of a wind turbine generator set according to claim 2 , wherein the connecting lines of two non-adjacent strain gauges are perpendicular to each other. 4 . 4. The method for calibrating and calculating the blade root load strain gauge of a wind turbine considering the installation deflection angle according to claim 1, wherein the wind turbine is in a shutdown state during calibration, and the minimum number of cycles of the free rotation of the wind rotor is three cycles. . 5. the wind turbine blade root load strain gauge calibration calculation method considering the installation deflection angle according to claim 1, it is characterized in that, when calibrating a total of three blades, one blade pitch angle is 0 degree, the other blade The blade pitch angle is 90 degrees, and the third blade pitch angle is set to any value from 0 to 90 degrees. 6 . The method for calibrating and calculating the blade root load and strain gauge of a wind turbine generator set according to claim 1 , wherein the wind speed is 3-4m/s during calibration. 7 . 7. the calculation method for the calibration calculation method of the blade root load strain gauge of the wind turbine generator set considering the installation deflection angle according to claim 1, is characterized in that, the calibration equation is as follows:

In the above formula, S _e and S _f are the load signals in the swing and swing directions, respectively, M _be and M _bf are the calibrated loads,

initial calibration slope matrix,

Initial calibration offset matrix. 8. The wind turbine blade root load strain gauge calibration calculation method considering installation deflection angle according to claim 7, is characterized in that, the calculation formula of initial calibration slope is as follows:

In the above formula, F _e and F _f are the gravity generated by the blade at the position of the center of mass, _Le and L _f are the distance between the center of mass of the blade and the position of the patch, α _e , α _f are the cabin elevation angle, β _e , β _f is the blade cone angle,

is the average value of the swing load signal during the idling process,

is the average value of the swing load signal during the idling process, slope _e and slope _f are the initial calibration slopes. 9. The method for calibrating and calculating the load and strain gauge of the wind turbine blade root load and strain gauge considering the installation deflection angle according to claim 8, characterized in that, due to the existence of the installation deflection angle, the blade root swing bending moment _Me is actually: The projected vector sum of the calibrated loads M _be and M _bf in the swing direction; similarly, the swaying moment M _f of the blade root is actually the projected vector sum of the calibrated loads M _be and M _bf in the swing direction, expressing The formula is as follows: Me = M _be · _cosθ +M _bf ·sinθ, M _f =-M _be ·sinθ+M _bf ·cosθ, Combined with the calibration equation, the following formula is obtained:

In the above formula, S _e and S _f are the load signals in the swing and swing directions, respectively, M _be and M _bf are the load amounts obtained by calibration, slope _e and slope _f are the initial calibration slopes, and offset _e and offset _f are the initial calibration slopes. Calibration offset.

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