Parameter acquisition method of photovoltaic tracking system

Abstract

The invention provides a parameter acquisition method of a photovoltaic tracking system, which comprises the following steps of: acquiring longitude and latitude, time and date of a device installation place by using GPS (Global Positioning System) positioning, and describing the relative position of the sun through a sun-oriented movement trajectory tracking algorithm; calculating a tracking angle at which the camera should rotate by using the known relative position of the sun and the direction vector and the position vector of the tracking camera; the camera is driven to rotate to a theoretical angle, and then position tracking of the sun is achieved through the angle sensor; in the tracking process, eight-quadrant illumination intensity data is collected through a self-adaptive weight distribution algorithm model. According to the invention, real-time tracking of the sun is realized, and effective picture data acquisition work for the sun area in the sky is completed. The illumination intensity value calculated by using the adaptive weight distribution algorithm model can reduce the influence of the external environment on the data to a certain extent, balance the error and deviation between the sensors, and finally improve the measurement precision of the illumination intensity.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic tracking, and in particular to a parameter acquisition method for a photovoltaic tracking system. Background Art

[0002] Photovoltaic tracking system is a photovoltaic system that can automatically track the sun and increase the overall power generation. The solar photovoltaic array automatic tracking system tracks the movement of the sun in real time so that sunlight directly hits the photovoltaic array, thereby increasing the amount of solar radiation received by the photovoltaic array and improving the overall power generation of the solar photovoltaic power generation system. There are four widely used solar photovoltaic automatic tracking systems, including horizontal single-axis tracking, double-column inclined single-axis tracking, vertical single-axis tracking and dual-axis tracking. Among them, horizontal single-axis tracking, inclined single-axis tracking and vertical single-axis tracking have only one degree of rotational freedom, and dual-axis tracking has two degrees of rotational freedom. The effect of photovoltaic tracking mainly depends on the collection of various related parameters. Parameters with higher precision are conducive to improving the tracking effect. Therefore, how to improve the collection quality of photovoltaic tracking parameters is an urgent problem to be solved. Summary of the invention

[0003] The present invention provides a parameter acquisition method for a photovoltaic tracking system to solve the deficiencies of the prior art in the background technology.

[0004] The present invention provides a parameter acquisition method for a photovoltaic tracking system, comprising the following steps:

[0005] The latitude and longitude, time and date of the device installation location are obtained by using GPS positioning, and the relative position of the sun is described by the apparent solar motion trajectory tracking algorithm;

[0006] The tracking angle that the camera should rotate is calculated using the known relative position of the sun and the direction vector and position vector of the tracking camera;

[0007] Drive the camera to rotate to the theoretical angle, and then realize position tracking through the angle sensor, and realize the camera's tracking function of the sun in a closed loop to complete dynamic image acquisition;

[0008] During the tracking process, the eight-quadrant light intensity data is collected through an adaptive weight allocation algorithm model.

[0009] Furthermore, the tracking angle that the camera should rotate is calculated as follows:

[0010] The solar motion model established, the solar declination angle δ, hour angle ω, solar altitude angle α s , solar azimuth γ s Assuming that the inclination angle between the camera and the horizontal plane is θ, and the camera's orientation angle is A, the following formula is used to calculate the pitch angle e and yaw angle α that the camera needs to rotate to track the sun:

[0011] First, the current time, date, and longitude and latitude coordinates of the device installation site are obtained based on GPS positioning, and the longitude and latitude coordinates of the device installation site are converted into coordinates (X, Y, Z) in the geocentric earth-fixed coordinate system. Then, the position vector (XS, YS, ZS) of the sun in the geocentric earth-fixed coordinate system is calculated using astronomical methods, and the azimuth angle A of the sun relative to the camera is calculated. z And the altitude angle EI, the specific calculation formula is:

[0012] XS=cosω×cosδ

[0013] YS=sinω×cosδ

[0014] ZS=sinδ

[0015]

[0016] A z =atan2(-YS,-XS)

[0017] EI=asin(ZS / R)

[0018] According to the obtained azimuth angle A of the sun relative to the camera z The pitch angle e and yaw angle α that the camera needs to rotate can be calculated by using the altitude angle EI and the known inclination angle θ between the camera and the horizontal plane. The specific formula is:

[0019] e=atan(tanEI×cosθ-sinθ×cos(A z -A)÷cosEI)

[0020] α=atan2(sin(A z -A),cos(A z -A)×sinθ+tanEI×cosθ)

[0021] Among them, e represents the angle (pitch angle) that the camera needs to rotate around the vertical axis, in radians; α represents the angle (yaw angle) that the camera needs to rotate around the horizontal axis, in radians. atan2() is the four-quadrant inverse tangent function, tan() is the tangent function, and atan() is the inverse tangent function.

[0022] Furthermore, the calculation formula of the solar declination angle δ is:

[0023] δ=23.45sin(2πd / 365)°

[0024] Or δ=23.45sin[360(284+n) / 365]°

[0025] Where, δ is the declination on the nth day of the year or the dth day from the vernal equinox, d is the nth day from the vernal equinox, and n is the date number in the year.

[0026] Furthermore, the calculation formula of the solar hour angle ω is:

[0027]

[0028] Where: H s H is the solar time at the location where the tracking system is installed; ls is the standard time of the location, i.e. Beijing time; L sm is the longitude of the location where the system is installed; L lso is the latitude of the installation location; E is the correction value, which corrects the error caused by the revolution, in minutes. The specific calculation formula is as follows:

[0029] E=9.9sin2B-7.5cosB-1.5sinB

[0030] in:

[0031]

[0032] n is the value of the day in a year, such as January 1 is 1, ranging from 1 to 365;

[0033] The difference between the local latitude and the standard time zone latitude is negative in the Eastern Hemisphere and positive in the Western Hemisphere. The formula can be simplified to:

[0034]

[0035] The specific calculation formula of the hour angle ω can be summarized as:

[0036] ω=(H s -12)×15°

[0037] Furthermore, the solar altitude angle α s satisfy:

[0038]

[0039] In the formula is the geographic latitude, δ is the solar declination, and ω is the solar hour angle.

[0040] Furthermore, the solar azimuth angle γ s satisfy:

[0041]

[0042]

[0043] Among them, α sis the solar altitude angle, δ is the solar declination, and ω is the solar hour angle.

[0044] Furthermore, the eight-quadrant light intensity data is collected by using the adaptive weight allocation algorithm model, and the specific steps are as follows:

[0045] Each light sensor will collect light intensity values ​​once every minute, taking every five minutes as a group, and calculate the average value and record it as x i , where i is the number of the sensor (i∈[1,8]);

[0046] Calculate the average value of the total light intensity data collected by all sensors within five minutes as the initial estimate, recorded as x0;

[0047] For each sensor data, calculate the difference between it and the initial estimate, denoted as:

[0048] d i =x i -x0

[0049] Calculate the weight w of each data point based on the difference between it and the initial estimate. i In this model, a form similar to an exponential function is used to calculate the corresponding weights. The calculation formula is:

[0050] w i =e -α|di|

[0051] Where α is a positive constant that controls how fast the weight changes with the difference. When the difference is small, the weight is close to 1, which means that the contribution of this data point is large. When the difference is large, the weight is close to 0, which means that the contribution of this data point is small.

[0052] Normalize all weights so that their sum is equal to 1, that is:

[0053]

[0054] Use the adaptive weighted average to calculate the final light intensity value x, that is:

[0055]

[0056] At least one of the above technical solutions adopted in the embodiments of the present invention can achieve the following beneficial effects:

[0057] The present invention can track the sun in real time by calculating the pitch angle and yaw angle that the camera needs to rotate in real time, and complete the effective image data collection work for the sun area in the sky. The light intensity value calculated by the adaptive weight distribution algorithm model can reduce the impact of the external environment on the data to a certain extent, balance the errors and deviations between sensors, and ultimately improve the measurement accuracy of light intensity. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0059] Figure 1 1 is a diagram showing the declination angle and hour angle coordinates of an embodiment of the present invention.

[0060] Figure 2 1 is a coordinate representation diagram of the altitude angle and the azimuth angle according to an embodiment of the present invention.

[0061] Figure 3 This is a flow chart of the algorithm model for tracking the apparent solar motion trajectory according to an embodiment of the present invention.

[0062] Figure 4 Schematic diagram of an eight-quadrant light intensity data acquisition device based on adaptive weight allocation according to an embodiment of the present invention.

[0063] Figure 5 This is a flow chart of an adaptive weight allocation algorithm model according to an embodiment of the present invention. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0065] The technical solutions provided by various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0066] The parameter acquisition method of the photovoltaic tracking system of the present invention mainly acquires dynamic image acquisition and light intensity acquisition.

[0067] First, the image acquisition device uses GPS positioning to obtain the latitude and longitude, time and date of the device installation location. The relative position of the sun is described by the apparent solar motion trajectory tracking algorithm. Then, the tracking angle that the camera should rotate is calculated using the known relative position of the sun and the direction vector and position vector of the tracking camera. Finally, the camera is driven to rotate to the theoretical angle, and then the position tracking closed loop is realized through the angle sensor to realize the camera's tracking function of the sun, completing the dynamic image acquisition work.

[0068] Regarding the apparent solar motion trajectory tracking algorithm: it mainly relies on the equatorial and horizontal coordinate systems to describe the position of the sun relative to the earth. The equatorial coordinate system can be represented by the declination angle δ and the hour angle ω. Figure 1 It is a diagram showing the declination angle δ and the hour angle ω.

[0069] Declination angle δ: The solar declination angle is also called solar declination. It is the angle between the line connecting the point A where the sun shines directly on the earth and the center of the earth O (AO, that is, the line connecting the center of the sun S and the center of the earth O) and the projection on the equatorial plane. It describes the relative position change caused by the earth's revolution around the sun at a certain inclination. The calculation formula for the change of declination angle in a year is as follows:

[0070] δ=23.45sin(2πd / 365)°

[0071] Or δ=23.45sin[360(284+n) / 365]°

[0072] Where, δ is the declination on the nth day of the year or the dth day from the vernal equinox, d is the nth day from the vernal equinox, and n is the date number in the year.

[0073] Hour angle ω: The rotation of the earth will change the relative position of the sun and the earth, and this change is described by the hour angle. The line OP connecting the center of the earth O and any point P on the surface will have a projection OB on the equatorial plane. The line connecting the center of the sun and the earth will also have a projection OQ on the equatorial plane at 12 o'clock locally. The angle between the two is the hour angle ω. Due to the rotation of the earth, the position of the sun relative to the earth is also constantly changing. The solar hour angle is calculated using the solar time of the location where the system is installed. There is a time difference between the solar time and the standard time used in various regions, so it is usually necessary to convert the standard time to the solar time. The specific formula is as follows:

[0074]

[0075] Where: H s H is the solar time at the location where the tracking system is installed; ls is the standard time of the location, i.e. Beijing time; L sm is the longitude of the location where the system is installed; L lsois the latitude of the installation location; E is the correction value, which corrects the error caused by the revolution, in minutes. The specific calculation formula is as follows:

[0076] E=9.9sin2B-7.5cosB-1.5sinB

[0077] in:

[0078]

[0079] n is the value of the day in a year, such as 1 for January 1, and ranges from 1 to 365.

[0080] The difference between the local latitude and the standard time zone latitude is negative in the Eastern Hemisphere and positive in the Western Hemisphere. For example, my country is located in the Eastern Eighth Zone of the Eastern Hemisphere, so we take positive values ​​when calculating. The formula can be simplified to:

[0081]

[0082] Therefore, the specific calculation formula of the hour angle ω can be summarized as:

[0083] ω=(H s -12)×15°

[0084] About the horizontal coordinate system: The horizontal coordinate system is established from the universe to describe the relative position of the sun and the earth. At this time, the position of the sun is based on the horizontal plane as the reference system, and its position can be expressed by the altitude angle α s With azimuth γ s To represent, the coordinate representation diagram is as follows Figure 2 As shown. Taking the horizon as the reference system means that any angle between the sun and the earth is the angle between the horizon. The horizon coordinate system is consistent with the equatorial coordinate system, expressed by the declination angle δ and the hour angle ω.

[0085] Zenith angle θ z : The angle between the line connecting the sun and the center of the earth and the normal to the horizon, that is, Figure 2 The angle θ between OP and QP z It is called the zenith angle. Zenith angle θ z With altitude angle α s The relationship is: z +α s =90°.

[0086] Altitude angle α s : The angle between the line connecting the sun and the center of the earth and its projection line on the horizon is called the altitude angle, that is, Figure 2 The angle α between OP and Pg s The calculation formula is as follows:

[0087]

[0088] In the formula is the geographic latitude, δ is the solar declination, and ω is the solar hour angle.

[0089] Solar azimuth γ s : The angle between the south direction line PS and the projection Pg of the sun's rays on the ground plane is the azimuth. Its calculation formula is as follows:

[0090]

[0091]

[0092] Therefore, as long as you know the latitude and longitude of the place, the date and the current time, you can know the altitude and azimuth of the sun at that time in the horizontal coordinate system.

[0093] In the above, by establishing the solar motion model in the equatorial coordinate system and the horizontal coordinate system, the motion trajectory of the sun is analyzed and calculated, and the position of the sun can be determined in real time. Therefore, it is only necessary to calculate the theoretical tracking angle, drive the camera to rotate to the theoretical angle, and then realize the position tracking closed loop through the angle sensor to finally realize the camera's tracking function of the sun.

[0094] Calculation of tracking angle: Regarding the position of the sun in the sky, the solar declination angle δ, hour angle ω, and solar altitude angle α can be obtained through the established solar motion model. s , solar azimuth γ s Assuming that the inclination angle of the camera to the horizontal plane is θ, and the camera's orientation angle is A, the following formula can be used to calculate the pitch angle e and yaw angle α that the camera needs to rotate to track the sun:

[0095] First, the current time, date, and longitude and latitude coordinates of the device installation site are obtained based on GPS positioning, and the longitude and latitude coordinates of the device installation site are converted into coordinates (X, Y, Z) in the geocentric earth-fixed coordinate system. Then, the position vector (XS, YS, ZS) of the sun in the geocentric earth-fixed coordinate system is calculated using astronomical methods, and the azimuth angle A of the sun relative to the camera is calculated. z And the altitude angle EI, the specific calculation formula is:

[0096] XS=cosω×cosδ

[0097] YS=sinω×cosδ

[0098] ZS=sinδ

[0099]

[0100] A z =atan2(-YS,-XS)

[0101] EI=asin(ZS / R)

[0102] According to the obtained azimuth angle A of the sun relative to the camera z The pitch angle e and yaw angle α that the camera needs to rotate can be calculated by using the altitude angle EI and the known inclination angle θ between the camera and the horizontal plane. The specific formula is:

[0103] e=atan(tanEI×cosθ-sinθ×cos(A z -A)÷cosEI)

[0104] α=atan2(sin(A z -A),cos(A z -A)×sinθ+tanEI×cosθ)

[0105] Among them, e represents the angle (pitch angle) that the camera needs to rotate around the vertical axis, in radians; α represents the angle (yaw angle) that the camera needs to rotate around the horizontal axis, in radians. atan2() is the four-quadrant inverse tangent function, tan() is the tangent function, and atan() is the inverse tangent function.

[0106] By calculating the pitch and yaw angles that the camera needs to rotate in real time, the sun can be tracked in real time, completing the effective image data collection work for the sun area in the sky. Figure 3 shown.

[0107] In the photovoltaic tracking process, because the light intensity is easily disturbed by the complex environment and thus produces abnormal values, the present invention also relates to an eight-quadrant light intensity data acquisition device based on adaptive weight allocation, such as Figure 4 As shown in the figure, several light sensors are distributed in eight quadrants, which can collect eight sets of light intensity data at the same time. The adaptive weight allocation algorithm model is used to suppress abnormal data and amplify the weight of normal data, and finally obtain light intensity data with higher accuracy.

[0108] Regarding the adaptive weight allocation algorithm model, the specific process is as follows:

[0109] Each light sensor will collect light intensity values ​​once every minute, taking every five minutes as a group, and calculate the average value and record it as x i , where i is the number of the sensor (i∈[1,8]).

[0110] Calculate the average value of the total light intensity data collected by all sensors within five minutes as the initial estimate, recorded as x0.

[0111] For each sensor data, calculate the difference between it and the initial estimate, denoted as:

[0112] d i =x i -x0

[0113] Calculate the weight w of each data point based on the difference between it and the initial estimate. i In this model, a form similar to an exponential function is used to calculate the corresponding weights. The calculation formula is:

[0114] w i =e -α|di|

[0115] Where α is a positive constant that controls how fast the weight changes with the difference. When the difference is small, the weight is close to 1, which means that the contribution of this data point is large; when the difference is large, the weight is close to 0, which means that the contribution of this data point is small.

[0116] Normalize all weights so that their sum is equal to 1, that is:

[0117]

[0118] Finally, the adaptive weighted average is used to calculate the final light intensity value x, that is:

[0119]

[0120] The light intensity value x calculated using the adaptive weight allocation algorithm model can reduce the impact of the external environment on the data to a certain extent, balance the errors and deviations between sensors, and ultimately improve the measurement accuracy of light intensity. The flow chart of the adaptive weight allocation algorithm model is as follows: Figure 5 shown.

[0121] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A parameter collection method for a photovoltaic tracking system, characterized in that: The following steps are involved: The latitude and longitude, time and date of the device installation location are obtained by using GPS positioning, and the relative position of the sun is described by the apparent solar motion trajectory tracking algorithm; The tracking angle that the camera should rotate is calculated using the known relative position of the sun and the direction vector and position vector of the tracking camera; Drive the camera to rotate to the theoretical angle, and then realize position tracking through the angle sensor, and realize the camera's tracking function of the sun in a closed loop to complete dynamic image acquisition; During the tracking process, the eight-quadrant light intensity data is collected through an adaptive weight allocation algorithm model.

2. A parameter acquisition method for a photovoltaic tracking system according to claim 1, characterized in that: The tracking angle that the camera should rotate is obtained by calculation, specifically: The solar motion model established, the solar declination angle δ, hour angle ω, solar altitude angle α s , solar azimuth γ s Assuming that the inclination angle between the camera and the horizontal plane is θ, and the camera's orientation angle is A, the following formula is used to calculate the pitch angle e and yaw angle α that the camera needs to rotate to track the sun: First, the current time, date, and longitude and latitude coordinates of the device installation site are obtained based on GPS positioning, and the longitude and latitude coordinates of the device installation site are converted into coordinates (X, Y, Z) in the geocentric earth-fixed coordinate system. Then, the position vector (XS, YS, ZS) of the sun in the geocentric earth-fixed coordinate system is calculated using astronomical methods, and the azimuth angle A of the sun relative to the camera is calculated. z And the altitude angle EI, the specific calculation formula is: XS=cosω×cosδ YS=sinω×cosδ ZS=sinδ A z =atan2(-YS,-XS) EI=asin(ZS / R) According to the obtained azimuth angle A of the sun relative to the camera z The pitch angle e and yaw angle α that the camera needs to rotate can be calculated by using the altitude angle EI and the known inclination angle θ between the camera and the horizontal plane. The specific formula is: e=atan(tanEI×cosθ-sinθ×cos(A z -A)÷cosEI) α=atan2(sin(A z -A),cos(A z -A)×sinθ+tanEI×cosθ) Among them, e represents the angle (pitch angle) that the camera needs to rotate around the vertical axis, in radians; α represents the angle (yaw angle) that the camera needs to rotate around the horizontal axis, in radians. atan2() is the four-quadrant inverse tangent function, tan() is the tangent function, and atan() is the inverse tangent function.

3. The parameter collection method of a photovoltaic tracking system according to claim 2, characterized in that: The calculation formula of the solar declination angle δ is: δ=23.45sin(2πd / 365)° Or δ=23.45sin[360(284+n) / 365]° Where, δ is the declination on the nth day of the year or the dth day from the vernal equinox, d is the nth day from the vernal equinox, and n is the date number in the year.

4. The parameter collection method of a photovoltaic tracking system according to claim 2, characterized in that: The calculation formula of the solar hour angle ω is: Where: H s H is the solar time at the location where the tracking system is installed; ls is the standard time of the location, i.e. Beijing time; L sm is the longitude of the location where the system is installed; L lso is the latitude of the installation location; E is the correction value, which corrects the error caused by the revolution, in minutes. The specific calculation formula is as follows: E=9.9sin2B-7.5cosB-1.5sinB in: n is the value of the day in a year, such as January 1 is 1, ranging from 1 to 365; The difference between the local latitude and the standard time zone latitude is negative in the Eastern Hemisphere and positive in the Western Hemisphere. The formula can be simplified to: The specific calculation formula of the hour angle ω can be summarized as: ω=(H s -12)×15°.

5. The parameter collection method of a photovoltaic tracking system according to claim 2, characterized in that: The sun altitude angle α s satisfy: In the formula is the geographic latitude, δ is the solar declination, and ω is the solar hour angle.

6. The parameter collection method of a photovoltaic tracking system according to claim 2, characterized in that: The solar azimuth angle γ s satisfy: Among them, α s is the solar altitude angle, δ is the solar declination, and ω is the solar hour angle.

7. The parameter collection method of a photovoltaic tracking system according to claim 1, characterized in that: The eight-quadrant light intensity data is collected by using the adaptive weight allocation algorithm model, and the specific steps are as follows: Each light sensor will collect light intensity values ​​once every minute, taking every five minutes as a group, and calculate the average value and record it as x i , where i is the number of the sensor (i∈[1,8]); Calculate the average value of the total light intensity data collected by all sensors within five minutes as the initial estimate, recorded as x0; For each sensor data, calculate the difference between it and the initial estimate, denoted as: d i =x i -x0 Calculate the weight w of each data point based on the difference between it and the initial estimate. i In this model, a form similar to an exponential function is used to calculate the corresponding weights. The calculation formula is: w i =e -α|di| Where α is a positive constant that controls how fast the weight changes with the difference. When the difference is small, the weight is close to 1, which means that the contribution of this data point is large. When the difference is large, the weight is close to 0, which means that the contribution of this data point is small. Normalize all weights so that their sum is equal to 1, that is: Use the adaptive weighted average to calculate the final light intensity value x, that is:

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