CN120177001A - Calibration sampling method and system based on heliostat fields with different areas - Google Patents
Calibration sampling method and system based on heliostat fields with different areas Download PDFInfo
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Abstract
The application belongs to the technical field of heliostats, in particular to a calibration sampling method and a system based on heliostat fields with different areas, which provides a sampling expected queuing algorithm based on tracking accuracy, sampling time consumption estimation and mirror optical efficiency, and scheduling different heliostats for sampling based on a sampling optimization algorithm of multi-heliostat combined light intensity prediction and calibration camera temperature real-time monitoring so as to improve the sampling efficiency of heliostats in a heliostat field.
Description
Technical Field
The application belongs to the technical field of heliostats, and particularly relates to a calibration sampling method and system based on heliostat fields with different areas.
Background
The tower type photo-thermal mirror field has high requirements on tracking accuracy of the heliostat reflected light spots. After a period of operation, the heliostat can have reduced reflection accuracy. In order to maintain high accuracy of heliostat tracking, the heliostat needs to be calibrated continuously. The heliostat field is usually calibrated by adopting methods such as heliostat daytime white target calibration, heliostat reflected sunlight to camera sampling calibration and the like.
In general, 30-40 m2 medium heliostats are calibrated by adopting a daytime white target method, the white target size is large, and a single white target can only calibrate one heliostat at a time, however, for the heliostat field with the same lighting area and using a small heliostat, the efficiency is very low when the small heliostat is calibrated by adopting the method, and the calibration period of the heliostat field can be greatly prolonged.
When the heliostat is used for reflecting sunlight to the camera for sampling and calibrating the field, a calibration tower and a camera are generally arranged around the light-gathering field, the distance between the heliostat and the calibration camera is different, and meanwhile, the heliostat is suitable for a small planar heliostat due to the fact that the curvature radius of the medium-sized heliostat is fixed and the reflection light spots are large, and the method for sampling and calibrating the heliostat for reflecting sunlight to the camera is not suitable for the medium-sized heliostat.
Conventional tower photo-thermal fields typically have only small heliostats or only medium heliostats. In the large-scale mirror field, the small heliostat has the advantages of accurate condensation control in the area close to the heat absorption tower, and the medium heliostat with a certain curvature has the advantages of light spots in the area far from the heat absorption tower. For the field where the small heliostat and the medium heliostat are installed at the same time, the above two common calibration methods cannot be applied at the same time.
Disclosure of Invention
Based on the problems, the application provides a sampling expected queuing algorithm based on tracking accuracy, sampling time consumption estimation and mirror optical efficiency, and a sampling optimization algorithm based on multi-heliostat integrated light intensity prediction and calibration camera temperature real-time monitoring, which are used for scheduling different heliostats for sampling so as to improve the sampling efficiency of heliostats in a heliostat field. The technical proposal is as follows:
A calibration sampling method based on heliostat fields with different areas comprises the following steps:
S1, calculating tracking accuracy of a heliostat;
s2, calculating priority ordering;
S3, heliostat sampling scheduling based on sampling expected priority;
S4, periodic training;
s5, scheduling optimization is carried out based on multi-heliostat combined light intensity prediction and camera temperature real-time monitoring, whether the maximum combined light intensity reaches an upper limit is calculated, if yes, the step S3 is returned to, if not, the heliostat starts sampling, and after the sampling is completed, the sample is put in storage;
s6, judging whether the condition of incapability of sampling is met, if so, ending the sampling, and otherwise, returning to the step S2.
Preferably, the method further comprises the step S0. of preparing the calibration sampling environment in advance:
The heliostat parameter setting comprises a small heliostat, a medium heliostat and a medium heliostat, wherein the small heliostat refers to a planar heliostat with the area of 2-3 m < 2 >, and the medium heliostat refers to a curved heliostat with the area of 30-40 m < 2 >, and is a concave mirror with a certain curvature, which is formed by assembling a plurality of planar mirrors according to m rows and n columns;
The total number of the calibration cameras needed by the mirror field is based on the visual range of all cameras, all heliostats of the mirror field can be covered, each calibration camera can be matched and combined with heliostats in different areas, and each heliostat can also be matched and combined with a plurality of calibration cameras;
Daytime sampling, wherein heliostat reflection light spots in a sampling camera picture are brighter, and other areas are dark;
The sampling combination comprises three parts of heliostats, calibration cameras and solar light sources, wherein each calibration camera can form N sampling combinations according to the actual small-sized and medium-sized heliostats in the visual field of the calibration cameras, the sampling combination is represented by [ C i, Hi, Li ], the calibration cameras are represented by C, the heliostats are represented by H, and the solar light sources are represented by L;
Calibrating a camera:
Through camera calibration, determining the mapping relation between heliostat ID and camera pixel coordinates:
;
And (3) calibrating the region of interest, namely determining a light spot detection boundary for each heliostat in the field of view of the camera when the camera is calibrated so as to eliminate noise interference of light spot detection during sampling, wherein after one heliostat starts to sample, other heliostats in the light spot detection boundary of the heliostat cannot sample by using the camera, and the region is called a camera region of interest.
Preferably, the tracking accuracy of the heliostat is calculated as follows:
the heliostat is provided with two driving motors which respectively control the heliostat in azimuth angle And pitch angleRotating in the direction;
Each sampling combination successfully acquires a sample with the actual angle of the sample being While the theoretical angle of the sample isThen, the angle difference between the two driving motors in the sample is respectively:
;
;
The final tracking accuracy is calculated by the heliostat based on samples of different angles acquired by different sampling combinations, and is as follows:
;
Wherein:
r, tracking accuracy of heliostat;
the number of samples per heliostat;
the calibration sampling preparation stage calculates the tracking accuracy of all heliostats, and when a new sample is acquired, recalculates the tracking accuracy of the heliostats, and updates the tracking accuracy ordering of all heliostats.
Preferably, the area of the medium heliostat is larger, the single sampling time consumption is longer than that of the small heliostat, and the solar altitude angle of the same heliostat at different times every day is different, so that the sampling time consumption is different, the sampling time consumption average value of effective samples of the heliostat with the same hour time period and the same type is calculated as the time consumption estimated value of the current sampling by taking the hour time period of the same hour time period as a dividing unit, and the solar altitude angle of the heliostat with the same hour time period in different seasons is larger, so that the sampling time consumption average value is calculated, and the samples with the set number are arranged in the inverted order of the sample acquisition time in the hour time period.
Preferably, the time consumption ratio of the medium heliostat to the small heliostat in the current hour period is calculated as follows:
;
;
Wherein:
ρ tM sampling time consumption ratio of the medium heliostat;
ρ tS sampling time-consuming ratio of small heliostat;
T j time consuming the sample of the medium heliostat;
J, the number of sampling samples of the medium heliostat;
t k time consuming sampling of the sample by the small heliostat;
K, the number of sampling samples of the small heliostat;
The sampling expected calculation formula for integrating the heliostat tracking accuracy, the heliostat sampling time consumption ratio and the heliostat optical efficiency value is as follows:
;
The heliostat optical efficiency parameter formula is:
;
Wherein:
E, sampling expected values of heliostats;
R, heliostat tracking accuracy;
ρ, heliostat sampling time consumption ratio;
η is the value of the optical efficiency of the heliostat;
k 1、k2 dynamic adjustment coefficients;
the optical efficiency value of the heliostat;
Heliostat reflectivity;
Heliostat curvature;
cosine efficiency of heliostat;
Shadow shielding efficiency of heliostats;
Atmospheric transmittance;
before the heliostat of the heliostat field starts sampling, a sampling expected value of each heliostat is calculated, and the larger the expected value is, the higher the sampling priority is.
Preferably, in step S5, the photosynthetic intensity is predicted to be different in illumination intensity of reflection light spots of heliostats with different surface types, one medium heliostat is composed of m rows and n columns of mirror surfaces, and the maximum value of illumination intensity generated by the reflection light spots on a calibrated and sampled camera is approximately the same as that of a small heliostatWhen M medium heliostats and N small heliostats are sampled by using one calibration camera at the same time, multi-facula overlapping occurs, and the maximum total light intensity on the calibration camera is as follows:
;
Wherein:
m, the number of medium heliostats;
the number of small heliostats;
m, lens row number of the medium heliostat;
n, lens columns forming the medium heliostat;
r is specular reflectivity;
I i, the illumination intensity of a single lens of the medium heliostat;
And I j, the illumination intensity of the small heliostat lens.
Preferably, when the heliostat of the heliostat field is sampled, a plurality of heliostats simultaneously use the same calibration camera for sampling, and as the number of the heliostat light spots increases, the temperature of the calibration camera gradually increases, and the upper temperature resistance limit of the calibration camera and the upper energy of the heliostat reflection light spots determine the upper number limit of the heliostats simultaneously sampled;
The temperature is divided into a normal temperature region, a warning temperature region and an over Wen Wenou when the camera is calibrated and sampled, the calibration control system can schedule a plurality of heliostats in a standby state to enter a sampling state when the camera temperature is in the normal temperature region, the calibration control system maintains the current heliostat sampling and does not increase the heliostat in the new standby state to enter the sampling state when the camera temperature is gradually increased to the warning temperature region along with the increase of the simultaneous sampling quantity, and the temperature of the camera in the warning temperature region can be continuously increased to the over temperature region due to the influence of DNI increase, the increase of the simultaneous sampling heliostat quantity or other factors, at the moment, all heliostats stop sampling immediately.
Preferably, for the same calibration camera, when a heliostat enters a sampling pre-queuing waiting state, the maximum total light intensity of the heliostat after entering the sampling needs to be estimated; if the maximum photosynthetic intensity which can be born by the calibration camera is exceeded, the heliostat cannot start sampling, the maximum total light intensity needs to be estimated again after the sampling of any heliostat which is being sampled is ended, the judging process is repeated, and the heliostat can formally start sampling until the estimated total light intensity is within the allowable range;
Because the total light intensity of the medium-sized heliostat is X times that of the small-sized heliostat, when the medium-sized heliostat enters a sampling pre-queuing waiting state, the sampling can be formally started after the sampling of a plurality of small-sized heliostats is completed.
A calibration sampling system based on heliostat fields with different areas comprises a signal acquisition unit, a processing unit and an output unit;
the signal acquisition unit is used for acquiring a processing signal;
the processing unit is used for calculating tracking accuracy of heliostats, calculating expected priority, and carrying out heliostat sampling scheduling based on the expected priority;
And the output unit is used for visually outputting the result.
Compared with the prior art, the application has the following beneficial effects:
The method uses sunlight and a calibration camera to calibrate and sample in the daytime.
The method calibrates the region of interest of the calibration camera, can avoid mutual interference between reflected light spots generated during sampling of heliostats with similar distances, and eliminates noise interference during light spot extraction and recognition during sampling, thereby improving sampling efficiency.
The method sorts the heliostats according to tracking accuracy, and the lower the tracking accuracy is, the higher the calibration sampling priority is.
The method considers that the area of the medium heliostat is larger, the single sampling time is longer than that of the small heliostat, and meanwhile, the influence of the optical efficiency of the mirror surface is considered. Thus, the desired prioritization algorithm is optimized based on tracking accuracy, sampling time-consuming estimation, and specular optical efficiency.
According to the method, the maximum synthetic light intensity on a single calibration camera is pre-calculated when different quantities of medium-sized and small-sized heliostats are simultaneously sampled, so that the quantity of heliostats simultaneously sampled by the single calibration camera is controlled, and the over-temperature damage of the calibration camera caused by excessive energy is prevented.
The method provides a sampling temperature interval, an alarm temperature interval and a stop sampling temperature interval of the calibration camera, can improve the concurrency and efficiency of the calibration sampling, and simultaneously protects the hardware of the calibration camera from being damaged.
According to the method, the rotation of the heliostat is controlled by the two stepping motors in the horizontal direction and the vertical direction, and the movement path of the reflecting light spots of the heliostat is controlled to avoid the calibration camera, so that the generation of sampling light spots and the temperature interference of the camera can be avoided.
Drawings
FIG. 1 is a schematic illustration of region of interest calibration in calibrating camera view;
FIG. 2 is a heliostat sampling schedule flow chart;
FIG. 3 is a schematic diagram of a field calibration sampling;
In the figure:
11-region of interest of small heliostat, 12-small heliostat, 13-region of interest of medium heliostat of small and medium heliostat adjacent region, 14-region of interest of medium heliostat of small and medium heliostat adjacent region, 15-region of interest of medium heliostat, 16-region of interest of medium heliostat, 17-region of interest of small heliostat of small and medium heliostat adjacent region, 18-region of small heliostat of small and medium heliostat adjacent region;
21-heat absorber, 22-heat absorbing tower, 23-calibration camera, 24-small heliostat, 25-medium heliostat.
Detailed Description
The following detailed description of the technical solutions of the present application will be made by specific embodiments and accompanying drawings, and it should be understood that the embodiments of the present application and specific features in the embodiments are detailed descriptions of the technical solutions of the present application, and not limiting the technical solutions of the present application, and that the specific technical features may be combined with each other.
The method uses sunlight and a calibration camera to calibrate and sample in the daytime.
As shown in fig. 1, the method calibrates the interested region of the calibration camera, and can avoid mutual interference between reflected light spots when heliostats with similar distances are sampled, so as to eliminate noise interference when light spots are extracted and identified in the sampling process, thereby improving the sampling efficiency.
The method sorts the heliostats according to tracking accuracy, and the lower the tracking accuracy is, the higher the calibration sampling priority is.
The method considers that the area of the medium heliostat is larger, the single sampling time is longer than that of the small heliostat, and meanwhile, the influence of the optical efficiency of the mirror surface is considered. Thus, the desired prioritization algorithm is optimized based on tracking accuracy, sampling time-consuming estimation, and specular optical efficiency.
According to the method, the maximum synthetic light intensity on a single calibration camera is pre-calculated when different quantities of medium-sized and small-sized heliostats are simultaneously sampled, so that the quantity of heliostats simultaneously sampled by the single calibration camera is controlled, and the over-temperature damage of the calibration camera caused by excessive energy is prevented.
The method provides a sampling temperature interval, an alarm temperature interval and a stop sampling temperature interval of the calibration camera, can improve the concurrency and efficiency of the calibration sampling, and simultaneously protects the hardware of the calibration camera from being damaged.
According to the method, the rotation of the heliostat is controlled by the two stepping motors in the horizontal direction and the vertical direction, and the movement path of the reflecting light spots of the heliostat is controlled to avoid the calibration camera, so that the generation of sampling light spots and the temperature interference of the camera can be avoided.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
2-3, a calibration sampling method based on heliostat fields of different areas includes the following steps:
s1, starting a sampling program, and calculating tracking accuracy of a heliostat;
s2, calculating priority ordering;
s3, heliostat sampling scheduling based on sampling expected priority, and heliostat with highest priority waits;
S4, periodic training;
s5, scheduling optimization is carried out based on multi-heliostat combined light intensity prediction and camera temperature real-time monitoring, whether the maximum combined light intensity reaches an upper limit is calculated, if yes, the step S3 is returned, and if not, after the heliostat begins to sample, the sample is put in storage;
s6, judging whether a condition that cannot be sampled (such as sunset cannot be sampled) is reached, if so, ending the sampling, and otherwise, returning to the step S2.
Calibration sampling environment and early preparation:
1. Heliostat:
1) Small heliostat:
The small heliostat refers to a planar heliostat with an area of 2-3 m 2.
2) Medium heliostat:
The medium heliostat refers to a curved heliostat with the area of 30-40 m < 2 >, and is a concave mirror with a certain curvature, which is formed by assembling a plurality of plane mirrors according to m rows and n columns.
2. Calibrating the camera:
The calibration camera is arranged on the outer wall support of the cylindrical heat absorption tower in the center of the lens field, and the larger the lens field is, the higher the height of the heat absorption tower is. In general, the mounting height of the camera in the large lens field can reach more than hundred meters. Meanwhile, a plurality of calibration cameras can be installed on different horizontal planes of the heat absorption tower in multiple layers, so that the requirements of more heliostat sampling in a mirror field, higher calibration sampling efficiency and the like are met.
The total number of calibration cameras needed for the field of mirrors is such that the field of mirrors can be covered by all heliostats for all cameras' viewable range. Meanwhile, each calibration camera can be paired with heliostats of different areas, and each heliostat can also be paired with a plurality of calibration cameras.
During daytime sampling, special mode, shutter, gain and other parameters need to be configured to reduce the brightness of the picture. Heliostat reflection light spots in the image of the sampling camera are brighter, and other areas appear dark.
3. Sampling combination:
The sampling combination consists of heliostat, calibration cameras and sunlight sources, and each calibration camera can form N sampling combinations according to the actual small and medium heliostat in the field of view. Sample combination is denoted by [ C 1, H1, L1 ] (where the calibration camera is denoted by C, the heliostat is denoted by H, the solar source is denoted by L):
4. calibrating a camera:
The calibration camera in the invention is calibrated in daytime, all heliostats are rotated to a horizontal posture before the calibration of the camera, and Azimuth angle (Az) and pitch angle (El) of all heliostats are kept the same. And when the camera is calibrated, selecting a mirror surface center point of the horizontal posture of the heliostat in the view angle of the camera as a three-dimensional coordinate point of the heliostat space, and calibrating the heliostats in all calibration cameras by using a camera calibration algorithm.
The camera calibration aims at establishing a mapping relation between a three-dimensional world coordinate system and a two-dimensional image pixel coordinate system. The world coordinates of the calibration camera are the camera lens center, and the world coordinates of the heliostat are the mirror surface center when in a horizontal posture, and the coordinate conversion calculation process is as follows:
1) Converting the world coordinates into calibrated camera coordinates;
2) Converting the calibration camera coordinates into image plane coordinates;
3) Converting the image plane coordinates into image pixel coordinates;
and (3) determining the mapping relation between the heliostat ID (the heliostat is represented by H) and the pixel coordinates of the camera through camera calibration:
。
5. and (5) calibrating a region of interest:
When each camera performs calibration sampling on heliostats in a visual field, mutually-interfered heliostat reflection light spots with similar distances can be generated, and the mutually-interfered heliostat light spots during sampling are called sampling conflicts. Thus, when a camera is calibrated, a spot detection boundary is determined for each heliostat in the field of view of the camera to eliminate noise interference of spot detection during sampling, after one heliostat begins to sample, other heliostats within the spot detection boundary of the heliostat cannot sample using the camera, which is referred to as a camera region of interest (Region of Interest, abbreviated as ROI).
(II) a calibration sampling method:
first, tracking accuracy calculation:
The heliostat can calculate the root mean square error (RMS), i.e., tracking accuracy, of the heliostat angle through a plurality of different sampled samples.
The heliostat is provided with two driving motors which respectively control the heliostat in azimuth angleAnd pitch angleAnd rotates in the direction. Each sampling combination successfully acquires a sample with the actual angle of the sample beingWhile the theoretical angle of the sample is. Then, the angle difference between the two driving motors in the sample is respectively:
;
;
The final tracking accuracy is calculated by the heliostat based on samples of different angles acquired by different sampling combinations, and is as follows:
;
Wherein,
R, tracking accuracy of heliostat;
Number of samples per heliostat.
The calibration sample preparation phase will calculate the tracking accuracy of all heliostats. And after a new sample is acquired, recalculating the tracking accuracy of the heliostats, and updating the tracking accuracy sequences of all the heliostats.
Second, heliostat sampling pre-queuing:
Sample expectation queuing algorithms based on heliostat tracking accuracy, sample time-consuming estimation, and specular optical efficiency.
1) The tracking accuracy of the heliostat is calculated based on the collected effective samples, and when the number of the samples is larger and the angular distribution of the heliostat is wider, the tracking accuracy is higher, namely the tracking error is lower.
2) The medium heliostat has a larger area and takes longer time for a single sampling than a small heliostat. For the same heliostat, the solar altitude angle at different times every day is different, so that the sampling time consumption is different. Therefore, taking the hours as a division unit, calculating the sampling time-consuming average value of the effective samples of heliostats of the same type in the same hour period through the hour period in which the sampling time is located, and taking the sampling time-consuming average value as the time-consuming estimated value of the current sampling. The solar altitude angle in the same hour period in different seasons has larger difference, so when the sampling time-consuming mean value is calculated, a certain number of samples are arranged in the reverse order of the sample collecting time in the hour period.
The time consumption ratio of the medium heliostat and the small heliostat in the current hour period is calculated as follows:
;
;
Wherein:
ρ tM sampling time consumption ratio of the medium heliostat;
ρ tS sampling time-consuming ratio of small heliostat;
T j time consuming the sample of the medium heliostat;
J, the number of sampling samples of the medium heliostat;
t k time consuming sampling of the sample by the small heliostat;
K, the number of samples sampled by the small heliostat.
3) The higher the heliostat mirror optical efficiency, the higher the thermal power output at the field of the mirror on a day-by-day basis. Thus, the higher the heliostat mirror optical efficiency, the higher its sampling priority, with the other factors being equal. The optical efficiency of the mirror surface is influenced by factors such as heliostat reflectivity, curvature, cosine efficiency, shadow shielding efficiency, atmospheric transmissivity and the like, and when the sampling priority is expected to be calculated, expected values are comprehensively considered.
The heliostat optical efficiency parameter formula is:
Wherein:
the optical efficiency value of the heliostat;
Heliostat reflectivity;
Heliostat curvature;
cosine efficiency of heliostat;
Shadow shielding efficiency of heliostats;
Atmospheric transmittance;
Finally, the sampling expected calculation formula integrating the heliostat tracking accuracy, the heliostat sampling time consumption ratio and the heliostat optical efficiency value is as follows:
;
Wherein:
E, sampling expected values of heliostats;
R, heliostat tracking accuracy;
ρ, heliostat sampling time consumption ratio;
η is the value of the optical efficiency of the heliostat;
k 1、k2 dynamic adjustment coefficients;
before the heliostat of the heliostat field starts sampling, a sampling expected value of each heliostat is calculated, and the larger the expected value is, the higher the sampling priority is.
Third, heliostat sampling scheduling algorithm
The sampling scheduling algorithm provided by the invention performs scheduling optimization based on multi-heliostat synthetic light intensity prediction and calibration camera temperature real-time monitoring.
Because meteorological factors such as DNI, field temperature, wind speed and the like can change in real time, the temperature of the calibration camera can also change in real time during sampling, and the number of heliostats which can be sampled by the calibration camera at the same time is different. Therefore, the calibration sampling system pre-queues based on the sampling expected priority, and performs real-time scheduling optimization on heliostat sampling according to multi-heliostat photosynthetic intensity prediction and real-time temperature feedback of a calibration camera.
1) Photosynthetic intensity prediction:
The illumination intensities of the reflecting light spots of the heliostats with different planes are different, one medium-sized heliostat consists of m rows and n columns of mirror surfaces, and the maximum value of the illumination intensity of the reflecting light spots generated by the camera for calibration sampling is approximately equal to that of the small heliostat Multiple times. When the M medium heliostats and the N small heliostats are sampled by using one calibration camera at the same time, multi-light-spot overlapping occurs, and the maximum total light intensity on the calibration camera is as follows:
;
Wherein:
m, the number of medium heliostats;
the number of small heliostats;
m, lens row number of the medium heliostat;
n, lens columns forming the medium heliostat;
r is specular reflectivity;
I i, the illumination intensity of a single lens of the medium heliostat;
I j the illumination intensity of the small heliostat lens;
the sum maximum of illumination intensities of M medium heliostats and N small heliostats;
Meanwhile, DNI is time-of-day, and DNI may generate a surge or dip situation with the appearance and drift of cloud. Resulting in a maximum total light intensity on a single calibration camera In order to ensure that the calibration camera is not damaged by high temperature, the number of heliostats sampled using the calibration camera needs to be automatically adjusted.
For the same calibration camera, when a heliostat enters a sampling pre-queuing waiting state, the maximum total light intensity of the heliostat after the heliostat enters the sampling needs to be estimated. If the maximum photosynthetic intensity which can be born by the calibration camera is exceeded, the heliostat cannot start sampling, the maximum total light intensity needs to be estimated again after the sampling of any heliostat which is being sampled is ended, and the judging process is repeated until the estimated total light intensity is within the allowable range, the heliostat can formally start sampling.
Because the total light intensity of the medium-sized heliostat is X times that of the small-sized heliostat, when the medium-sized heliostat enters a sampling pre-queuing waiting state, the sampling can be formally started after the sampling of a plurality of small-sized heliostats is completed.
In the following, two typical heliostat sampling priorities are taken as an example, and heliostat groups sampled simultaneously by the same calibration camera are scheduled. Taking 3m2 small heliostats (denoted by a) and 30m2 medium heliostats (denoted by B) as examples, it is assumed that the total light intensity of the medium heliostats is 10 times that of the small heliostats, and the upper limit of the number of heliostats in which the calibration camera simultaneously samples is 12 small heliostats.
Examples:
Assume that the sampling is desired prioritized as A1 a 2..a 14 a 15B 1a 16 a 17..a 29 a 30.
The heliostat groups (marked by underline) sampled at the same time are sequentially:
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
......
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
[A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15 B1 A16 A17 A18 A19 ...]
......
[... A15 B1 A16 A17 A18 A19 A20 A21 A22 A23 A24 A25 A26 A27 A28 A29 A30...]
[... A15 B1 A16 A17 A18 A19 A20 A21 A22 A23 A24 A25 A26 A27 A28 A29 A30...]
......。
2) Monitoring the temperature of a camera in real time:
When heliostat field heliostat is sampled, a plurality of heliostats can be simultaneously sampled by using the same calibration camera, and the temperature of the calibration camera is gradually increased along with the increase of the number of heliostat spots. The upper temperature tolerance limit of the calibration camera and the energy of the heliostat reflected light spots determine the upper limit of the number of heliostats that are sampled simultaneously. From the perspective of full-field calibration, the more heliostats are sampled simultaneously, the higher the field calibration efficiency and the shorter the calibration period. Therefore, in order to sample more heliostats simultaneously on the premise of ensuring the safety of the calibration camera, a temperature sensor is arranged in the calibration camera to feed back the temperature to a calibration control system in real time, so that the scheduling of the heliostats can be flexibly adjusted.
The temperature is divided into a normal temperature region, a warning temperature region and a super Wen Wenou when the camera is calibrated for sampling. The calibration control system may schedule a plurality of heliostats in a "standby" state to enter a "sampling" state when the camera temperature is at a normal temperature zone. As the number of simultaneous samples increases, the camera temperature gradually increases and exceeds the lower limit of the warning temperature zone, and the calibration control system maintains the current heliostat sample and no longer adds a new "standby" state heliostat to enter the "sampling" state. Due to the effects of increased DNI, increased number of simultaneously sampled heliostats, or other factors, the temperature of the camera in the warning temperature zone may continue to rise and exceed the lower limit of Wen Wenou, at which point, to protect the safety of the camera hardware, the calibration control system must control all heliostats to immediately stop sampling until the camera temperature falls to the normal temperature zone, and reschedule the heliostats to begin sampling.
Fourth, a facula motion trail prediction algorithm:
The sampling scheduling algorithm provided by the invention is used for controlling and optimizing based on the heliostat reflected light spot movement track prediction algorithm.
In order to prevent the calibration camera from being irradiated by the reflection light spots of the heliostat rotating randomly in the mirror field, the invention provides a prediction algorithm based on the movement track of the reflection light spots, and the algorithm can control the rotation distance of the heliostat in the horizontal and vertical directions by calculating the intersection point of rays and objects in a space coordinate system so as to prevent the calibration camera from being damaged due to temperature shock when the reflection light spots of a plurality of heliostats are irradiated simultaneously.
The ray reflected by the heliostat to the sunlight, i.e., the ray in space, can be expressed by a parametric equation. Let the ray start point beThe direction vector isThen any point on the rayCan be expressed asWherein t is greater than or equal to 0.t is a parameter that determines the position of a point on a ray. When t=0, the number of times of the process is,With increasing, the point moves in the direction of the ray.
Establishing a spatial cuboid model for calibrating a camera, the axis-aligned cuboid can be represented by six plane equations, respectively,,,,,. To determine whether the ray intersects the cuboid, it is necessary to determine the intersection of the ray and the six planes, respectively. For each plane, substituting the ray parameter equation into the plane equation according to the calculation method of intersecting the ray and the plane(Wherein,Is a planar normal vectorCoordinates of (c) and a t value is obtained. If the value of t for all planes does not satisfy t≥0, or the determined intersection point coordinates are not within the range of a cuboid (e.g., for planesFinding that the coordinates of the intersection point are greater thanOr is smaller than) Then the ray does not intersect the cuboid.
And determining to perform horizontal axis rotation or vertical axis rotation by utilizing the pre-calculation of the reflected ray position of the solar facula of the heliostat at the next moment, thereby completing the safe path of the reflected facula so as to avoid all calibration cameras and other devices of the mirror field, and finally moving to the sampling waiting position near the calibration camera of the current sampling combination of the heliostat.
Fifth, image processing and flare recognition:
1) Background diagram interception:
before starting sampling of a pre-queuing heliostat, capturing a screenshot region of interest image as a background image frame to be sampled of the heliostat according to the image coordinate position of the heliostat and the region of interest of the heliostat 。
2) Background difference and binarization processing:
After the heliostat enters a sampling starting stage from a pre-queuing state, a calibration camera starts to capture the light spots of the interested region of the heliostat in real time, and the sizes and pixel values of expected light spots are different for heliostats with different sizes. Collecting a flare image identified in a camera as a foreground image frame Taking the pixel difference value of the foreground image and the background image and taking the absolute value as the difference image of the sampling light spot:
;
After obtaining the light spot differential image, performing binarization processing on pixel points in the differential image, wherein different threshold values are required to be set as the light spot sizes and the intensities of heliostats with different sizes are different, and finally obtaining the binarization image of the light spot of the heliostat。
3) Spot identification:
Firstly, the light spot identification process utilizes a contour detection algorithm to extract the contour in the binarized image. And adopting a Canny edge detection algorithm, firstly carrying out Gaussian filtering on a binarized image to smooth noise, then calculating the gradient amplitude and direction of the image, determining edge pixels through non-maximum suppression and double-threshold detection, and finally obtaining a contour through edge connection.
And secondly, analyzing contour features. For the extracted contour, the length, closure, convexity and other characteristics of the contour can be analyzed. For heliostat reflected spots, the profile is typically closed, and the spot profile is typically approximately circular. For a spot of approximately circular shape, there is a relationship between the contour length and the area, and this feature is used to determine whether it is a spot, and discarding the image that fails to be identified.
And thirdly, calculating pixel coordinates corresponding to the central point of the light spot by using a centroid algorithm, and converting the pixel coordinates into angles of heliostats Az and El. Meanwhile, the angle of Az and El can be converted into the number of steps of the heliostat stepper motor.
Fourth, in the sampling process, the heliostat continuously rotates, the calibration camera continuously acquires the reflection light spot, and simultaneously, the angles of the heliostat Az and El and the stepping number of the heliostat stepping motor are continuously converted.
And finally, carrying out averaging treatment on the step number set obtained by sampling to obtain Az and El step numbers of heliostats under the sampling combination and related sampling information, namely, obtaining complete sample data.
Conventional tower photo-thermal fields typically have only small heliostats or only medium heliostats. In the large-scale mirror field, the small heliostat has the advantages of accurate condensation control in the area close to the heat absorption tower, and the medium heliostat with a certain curvature has the advantages of light spots in the area far from the heat absorption tower. At present, the commonly used daytime calibration method cannot be simultaneously applied to the fields of small heliostats and medium heliostats, and the daytime calibration method mainly solves the problem of sampling the fields of the small heliostats and the medium heliostats.
According to the calibration method for the region of interest of the calibration camera, mutual interference between reflected light spots during sampling of heliostats with similar distances can be avoided, so that noise interference during light spot extraction and recognition in the sampling process is eliminated, and the sampling efficiency is improved.
The invention provides a sampling expected queuing algorithm based on tracking accuracy, sampling time consumption estimation and mirror optical efficiency, so that high-efficiency sampling queuing control can be provided for small and medium heliostats at the same time.
The sampling scheduling algorithm provided by the invention performs scheduling optimization based on multi-heliostat synthetic light intensity prediction and calibration camera temperature real-time monitoring, so that the efficiency of sampling scheduling can be improved, and meanwhile, the safe and reliable operation of the calibration camera in the sampling process can be ensured.
The sampling scheduling algorithm provided by the invention is controlled and optimized based on the heliostat reflected light spot movement track prediction algorithm, so that mutual conflict and noise interference in the sampling process can be reduced, and damage to the mirror field equipment caused by irradiation of excessive reflected light spots can be avoided.
Claims (9)
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