Method and device for rapidly measuring tracking error of heliostat

Abstract

The invention aims to provide the method and the device for rapidly measuring the tracking error of the heliostat, which can be used for rapidly measuring the tracking error of the heliostat and is used for tracking deviation correction of the heliostat. The device is characterized by comprising a measuring camera, a camera holder, a steel structure bracket, a computer and a measured heliostat. The measuring camera is installed on the camera holder and provided with a protective cover, and the camera holder is fixed to the steel structure support. The heliostat sets the position of the measuring camera as a target point, when light spots deviate and need to be corrected, the controller controls the motor to enable the light spots to do spiral motion, meanwhile, the camera collects light spot images and calculates the average gray value of the images, the average gray value is compared with a light spot gray threshold value, and when the threshold value is reached, the light spots are corrected. The current azimuth-pitch angle of the heliostat and the azimuth-pitch angle of the heliostat before spiral rotation are recorded, a group of error data and multiple measurement error data of the heliostat are obtained, error parameters are obtained through a regression algorithm, the error parameters are substituted into a controller, and error correction of the heliostat is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy utilization, and particularly provides a tower type solar power station heliostat tracking error fast measurement method and device. BACKGROUND

[0002] Tower type solar thermal power generation technology is a clean renewable energy utilization technology, which has been rapidly developed in recent years. The heliostat is a key component of the tower type solar thermal power station. It tracks the sun by rotating around the double axes, reflects and focuses the sunlight to the heat absorber on the top of the tower, and then heats the heat transfer medium in the heat absorber to generate high-temperature heat energy, which is used for power generation. Various errors exist in the manufacturing and installation process of the heliostat, such as column tilt error, non-orthogonal error of the rotating shaft, and non-parallel error of the mirror surface relative to the pitch axis, etc., which leads to tracking error of the heliostat. The tracking error of the heliostat will affect the optical efficiency of the heliostat field, and then affect the power generation efficiency of the power station, so it is necessary to measure the tracking error of the heliostat and correct the tracking formula to make it accurately track.

[0003] At present, the methods for measuring the tracking error of the heliostat mainly include light target reflection measurement method, laser reflection measurement method and camera direct measurement method. The light target reflection measurement method is to install a diffuse white target on the tower, project the heliostat spot onto the white target, use a camera to shoot the spot image on the target, and obtain the tracking deviation data of the heliostat through image processing. The light target reflection measurement method requires that the brightness of the heliostat spot is greater than that of the target, otherwise the position of the spot cannot be distinguished. For a large heliostat field, the heliostat far away from the target has weak spot brightness, so the position of the spot cannot be distinguished, and thus the tracking error of the heliostat cannot be measured. The laser reflection measurement method is to install laser light sources around the heliostat field, project laser beams to the center of the heliostat, and the laser beams are reflected by the heliostat and received by the camera. The tracking error of the heliostat is obtained by calculating the position of the laser spot in the camera. The laser reflection measurement method has high requirements for the direction of the incident laser beam, has high cost, and needs to be measured point by point, so the measurement speed is slow. The camera direct measurement method is to install a camera on the tower or around the mirror field, and project the reflected spot of the heliostat directly into the camera. The tracking error data of the heliostat is calculated according to the position of the spot in the camera. The camera direct measurement method has the following shortcomings: when the tracking error of the heliostat is large, the camera cannot obtain the reflected spot of the heliostat, at this time the heliostat needs to be controlled to rotate and search for the spot of the heliostat, but the current spot searching algorithm is not optimized, and it takes a long time to find the spot, which leads to slow measurement speed of the tracking error of the heliostat. SUMMARY

[0004] The purpose of the present application is to provide a heliostat tracking error fast measurement method and device, which can quickly measure the tracking error of the heliostat for tracking correction of the heliostat. In order to solve the above technical problems, the heliostat tracking error fast measurement method and device of the present application is characterized by comprising a measurement camera, a camera holder, a steel structure support, a computer and a measured heliostat. The measurement principle is as follows:

[0005] The principal point position of the measurement camera is set as the target point, and the measured heliostat is controlled to project the light spot into the camera. When the heliostat accurately tracks, the light spot is normally incident into the measurement camera, and the gray scale of the light spot image reaches the maximum value. The gray scale threshold value of the current position heliostat is calculated through a function formula. When the heliostat has tracking error, the gray scale of the light spot image is weak or there is no light spot image, and the heliostat can be judged whether it realizes accurate tracking by comparing with the light spot gray scale threshold value. When the heliostat has tracking error, the heliostat is controlled to make azimuth and elevation movement, so that the light spot projection point trajectory conforms to the Archimedes spiral line, and the position of the camera is searched. When the camera captures the light spot, the light spot image is collected and the average gray scale value of the light spot is calculated, and compared with the light spot gray scale threshold value. When the light spot gray scale threshold value is satisfied, it indicates that the heliostat has realized accurate tracking. At this time, the current azimuth and elevation angles of the heliostat are recorded, and the difference with the initial azimuth and elevation angles is obtained, and the tracking error of the heliostat is obtained.

[0006] The heliostat tracking error fast measurement method and device of the present application can realize the purpose of quickly measuring the tracking error of the heliostat by using the Archimedes spiral algorithm to search the camera and using the light spot gray scale average threshold algorithm to judge whether the heliostat accurately tracks, and provides measurement data for correcting the tracking error of the heliostat. BRIEF DESCRIPTION OF DRAWINGS

[0007] The present application will be further described below in combination with the drawings and specific embodiments.

[0008] Figure 1 is a structural schematic diagram of a heliostat tracking error fast measurement device of a solar tower power station.

[0009] Figure 2 is a schematic diagram of light spot movement trajectory in the camera searching algorithm. DETAILED DESCRIPTION

[0010] As Figure 1As shown, the measurement camera 1 is installed on the steel structure support 3 through the camera holder 2. In order to prevent saturation caused by excessive exposure of the camera, a filter is installed on the lens of the measurement camera 1. In addition, the measurement camera 1 is equipped with a camera protective cover to avoid direct sunlight, which affects the service life of the camera. Adjust the holder of the measurement camera 1 so that the measurement camera 1 is directed towards the measured heliostat 5. The computer 4 is connected to the measured heliostat 5 and the measurement camera 1 through the network, which can control the azimuth and elevation rotation of the heliostat and can collect the images taken by the measurement camera 1 in real time.

[0011] The gray scale G of the heliostat projection spot taken by the measurement camera 1 and the direct solar radiation I d and the distance S of the heliostat 5 to the measurement camera 1 h , can be written in the form of a function: G = f(I d ,S h ), which can be obtained by experimental measurement. The direct solar radiation I d can be measured in real time by a direct solar radiation measuring instrument on the site of the solar power plant, and the distance S of the heliostat 5 to the measurement camera 1 h can be calculated according to the coordinate position of the heliostat 5. According to the function G = f(I d ,S h ), the theoretical maximum average gray scale value of the projection spot of the measured heliostat 5 is calculated and set as the spot gray scale threshold.

[0012] The principal point position of the camera 1 is set as the tracking target point of the heliostat 5, and the measured heliostat 5 is controlled by the computer 4 to project the spot to the measurement camera 1. The spot image in the measurement camera 1 is collected in real time, the average gray scale value of the spot is calculated, and compared with the set spot gray scale threshold. When the average gray scale of the spot in the camera 1 reaches the spot gray scale threshold, the spot reflected by the heliostat 5 is normally incident in the camera, and the heliostat 5 achieves accurate tracking, with a tracking error of 0. When there is a tracking error in the measured heliostat 5, the spot cannot be completely normally incident in the measurement camera 1, resulting in weak or no spot gray scale collected by the measurement camera 1.

[0013] When the measurement camera 1 does not receive the spot projected by the heliostat 5, the measured heliostat 5 is controlled to move in azimuth and elevation, so that the spot moves along an Archimedes spiral trajectory and gradually approaches the measurement camera 1, as shown in Figure 2 The motion trajectory of the spot conforms to the Archimedes spiral, and the polar equation of the spiral is as follows:

[0014]

[0015] Wherein, t represents the growth parameter. The growth parameter t changes with time, and the speed of change determines the speed of the spiral rotation. The parameter b represents the value of the radius r corresponding to the increase of one unit angle of the spiral. The change of the parameter a is equivalent to rotating the spiral, and the parameter b controls the distance between adjacent curves.

[0016] The rectangular coordinate equation of the spiral is as follows:

[0017]

[0018] Wherein, r is the radius of the spiral, t is the time, and x(t) and y(t) are the X and Y coordinates of the point on the spiral, respectively. The spiral takes the current measured focal position of the heliostat 5 as the starting point and expands around, sets the tracking target point of the heliostat 5 as a series of points on the spiral, and thus controls the movement track of the heliostat 5. As the spiral expands, the reflected light spot of the heliostat 5 enters the field of view of the measuring camera 1 and is captured by the measuring camera 1.

[0019] When the measuring camera 1 captures the light spot, the light spot gray value is compared with the set gray threshold value. When the threshold condition is met, it indicates that the light spot of the heliostat 5 is incident into the measuring camera 1, and the heliostat 5 has realized accurate tracking of the target point. Otherwise, the spiral search algorithm is started again with the current light spot position as the starting point, and the spiral search radius is reduced until the light spot gray value meets the light spot gray threshold value, so that the heliostat 5 realizes accurate tracking.

[0020] When the heliostat 5 realizes accurate tracking, the current azimuth and elevation angles of the heliostat are recorded, and the difference between the initial azimuth and elevation angles is obtained, so that the azimuth and elevation tracking errors of the heliostat 5 are obtained.

Claims

1. A method and apparatus for fast measurement of tracking error of heliostat, characterized in that Include: Measuring camera (1), measuring camera holder (2), steel structure support (3), computer (4), measured heliostat (5). The measuring camera (1) is installed on the measuring camera holder (2), and the camera (1) and the camera holder (2) are fixed on the steel structure support (3) with nuts. The measuring camera (1) is equipped with a protective cover. The heliostat (5) is installed on the ground and maintains a certain distance from the measuring camera (1). The measuring camera (1) faces the direction of the measured heliostat (5).

2. The method and device for fast measuring tracking error of heliostat according to claim 1, characterized in that: When measuring the tracking error of the heliostat, the tracking target point of the heliostat (5) is set as the principal point position of the measuring camera (1), and the heliostat (5) is controlled to project the light spot in the direction of the measuring camera.

3. The method and device for fast measuring tracking error of heliostat according to claim 1, characterized in that: When the heliostat (5) has a large tracking error, the light spot of the heliostat (5) cannot be projected into the field of view of the camera (1), at which point the heliostat (5) needs to be controlled to move in azimuth and pitch to make the light spot trajectory conform to the Archimedes spiral, and search for the position of the camera (1).

4. The method and device for fast measuring tracking error of heliostat according to claim 1, characterized in that: When the camera (1) captures the light spot, by comparing the gray scale of the light spot with the preset gray scale threshold, it can be determined whether the threshold condition is met. If the condition is met, it means that the light spot of the heliostat (5) is normally incident into the camera (1), at which point the heliostat (5) achieves accurate tracking. If the threshold condition is not met, the spiral search algorithm needs to be started again, taking the current light spot position as the starting point, reducing the spiral search radius, until the light spot gray scale meets the threshold requirement, at which point the heliostat (5) achieves accurate tracking.

5. The method and device for fast measurement of tracking error of a heliostat according to claim 1, characterized in that: In order to prevent the measuring camera (1) from being saturated, a filter needs to be installed in front of the camera lens.

6. The method and device for fast measurement of tracking error of a heliostat according to claim 1, characterized in that: In order to protect the measuring camera (1), a protective cover is installed outside the measuring camera (1).

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