Photovoltaic effective solar irradiance measurement method

Abstract

The invention relates to the technical field of photovoltaic power generation, in particular to a photovoltaic effective solar irradiance measurement method, which comprises the following steps of: converting optical power into irradiance and tracing the irradiance to an SI unit system by taking trap detection transmitted by a low-temperature radiation meter as an optical power standard device and combining a precise diaphragm; respectively collecting the output voltage of the total radiometer, the output voltage of the monitoring radiometer, the zenith angle of the total radiometer in the non-shielding state and the solar irradiance output by the absolute radiometer when the total radiometer is in the shielding state and the non-shielding state, and calibrating the total radiometer; angle response, temperature response, sensitivity linear response and spectral response data of the total radiometer and the photovoltaic module under different influence parameters are obtained, a correction coefficient set is obtained through fitting and used for conducting temperature, angle, irradiance linearity and spectral mismatch correction on the irradiance measured by the total radiometer, photovoltaic effective solar irradiance data are obtained, and the photovoltaic effective solar irradiance data are obtained. Accurate measurement of the solar irradiance for photovoltaic power generation is realized.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic power generation, and more specifically, to a method for measuring the effective solar irradiance of a photovoltaic system. Background Art

[0002] The energy efficiency of a photovoltaic system is a key indicator for evaluating the performance of a photovoltaic power station, and the solar irradiance is the core parameter for measuring the energy efficiency of a photovoltaic system. The solar irradiance is obtained by integrating the solar irradiance and the sampling time. Therefore, the accurate measurement of the solar irradiance is crucial for the evaluation of the energy efficiency of a photovoltaic system. At present, the measurement of the solar irradiance is mostly based on a solar irradiance meter, and the solar irradiance meter is divided into two types: thermoelectric type and photovoltaic type. The thermoelectric solar irradiance meter has characteristics such as a wide spectral response range (300 - 3000) nm, a flat spectral response, and a small annual attenuation rate; the photovoltaic solar irradiance meter is mostly based on a photovoltaic cell as a detector, with a response band of (300 - 1200) nm, a spectral response with spectral selectivity, which is close to the spectral response of a photovoltaic module, but has a larger annual attenuation rate. In the measurement of the energy efficiency of a photovoltaic system, it is usually necessary to place the solar irradiance meter outdoors for continuous monitoring for a long time. Considering the stability of the detector, a thermoelectric solar irradiance meter - a pyranometer is usually used as the detector. The existing industry test method is to place the pyranometer and the photovoltaic module coplanarly and obliquely, and collect the solar irradiance data output by the pyranometer at a certain fixed time interval (such as 5 s), and obtain the solar irradiance data within a certain time period through time integration.

[0003] However, there are many problems in the existing technology. First, the calibration uncertainty of the pyranometer is relatively large, which directly affects the accuracy of the measurement results. Second, the calibration of the pyranometer is based on an indoor solar simulator, and the calibration conditions and calibration environment are standard test conditions, while the actual application environment conditions are complex non-standard test conditions. The influence of the differences between the calibration and application environments on the measurement results is not considered in on-site tests. In addition, the irradiance for photovoltaic system energy efficiency testing should be the effective solar irradiance actually received by the photovoltaic module, but the pyranometer measures the meteorological solar irradiance in the full band, and the existing measurement method does not consider the spectral mismatch effect introduced by the difference between the spectral response of the photovoltaic module and the spectral response of the pyranometer. At the same time, the photovoltaic module has a planar structure, and the pyranometer has a spherical structure, and the existing measurement method does not consider the irradiance measurement deviation introduced by the difference in the angular response between the pyranometer and the photovoltaic module. Summary of the Invention

[0004] In view of this, the present application provides a method for measuring the effective solar irradiance of a photovoltaic system, aiming to solve the technical problem that the effective solar irradiance of a photovoltaic system cannot be accurately measured under complex environmental conditions, and improve the accuracy of the evaluation of the energy efficiency of a photovoltaic system.

[0005] The technical solution provided by the present application is as follows:

[0006] A method for measuring the effective solar irradiance of a photovoltaic system, comprising:

[0007] Construct an absolute radiometer calibration device, using a laser as the light source and a trap detector calibrated by cryogenic radiometry as the optical power standard. Convert the optical power into irradiance using a precision aperture, and trace the absolute radiometer measurement value to the SI unit system through the comparison method;

[0008] Construct an outdoor calibration device for a pyranometer, including an absolute radiometer traceable to the SI unit, a monitoring radiometer, and a pyranometer; when the pyranometer is in the blocked state and the unblocked state, collect the signal outputs of the absolute radiometer, the monitoring radiometer, and the pyranometer respectively, including the output voltage of the pyranometer and the output voltage of the monitoring radiometer, the zenith angle of the pyranometer in the unblocked state, and the solar irradiance output by the absolute radiometer, and calibrate the pyranometer based on the signal outputs;

[0009] Measure the spectral responsivity data of the pyranometer and the photovoltaic module; simulate solar radiation to obtain the angular response, temperature response, and sensitivity data sets of the pyranometer and the photovoltaic module under various influencing parameters at different irradiances, and obtain the correction coefficient sets of the pyranometer and the photovoltaic module under various influencing parameters through fitting and interpolation methods; the influencing parameters include the incident angle, temperature and humidity, irradiance, and spectral responsivity of the pyranometer and the photovoltaic module;

[0010] Synchronously collect the irradiance measured by the pyranometer, spectral irradiance, pyranometer temperature data, and the relative distribution data of solar radiation at various angles in the hemispherical space of the receiving surface of the photovoltaic module at the photovoltaic power generation site, and combine the correction coefficient sets to correct the irradiance measured by the pyranometer, including temperature correction, angular correction, sensitivity linear correction, and spectral mismatch correction, to obtain the effective solar irradiance data of the photovoltaic system.

[0011] In one possible implementation, when the pyranometer is in the blocked state and the unblocked state, calibrate the sensitivity of the pyranometer based on the signal outputs of the absolute radiometer, the monitoring radiometer, and the pyranometer, including:

[0012] Determine the calibration sensitivity of the pyranometer according to the output voltage of the pyranometer, the output voltage of the monitoring radiometer, the zenith angle of the pyranometer in the unblocked state, and the solar irradiance output by the absolute radiometer, expressed as:

[0013]

[0014] In the formula, k0 is the calibration sensitivity of the pyranometer, V1 is the output voltage of the pyranometer in the unblocked state, V2 is the output voltage of the pyranometer in the blocked state, V 01 is the output voltage of the monitoring radiometer when the pyranometer is in the unblocked state, V 02When the pyranometer is in the blocked state, monitor the output voltage of the pyranometer. α is the zenith angle when the pyranometer is in the unblocked state, and E d is the solar irradiance output by the absolute radiometer when the pyranometer is in the unblocked state.

[0015] In one possible implementation, simulate solar radiation to obtain the angular response data of the pyranometer and the photovoltaic module, including

[0016] Adjust the tilt angles of the pyranometer and the photovoltaic module at a preset angular interval, and simultaneously monitor and correct the change in the irradiance of the light source simulating solar radiation in real time. Collect the output signal of the pyranometer or the output short-circuit current parameter of the photovoltaic module, determine the relationship between the output signal of the pyranometer or the output short-circuit current of the photovoltaic module and the angular change, obtain the angular response data of the pyranometer and the photovoltaic module respectively, and divide the angular response data of the pyranometer and the photovoltaic module by the maximum value in their respective angular response data to obtain the angular response data S p (θ) of the pyranometer and the angular response data S M (θ) of the photovoltaic module.

[0017] In one possible implementation, simulate solar radiation to obtain the temperature response data of the pyranometer, including:

[0018] Set the irradiance of the simulated solar radiation to a constant solar irradiance value, gradually change the ambient temperature based on a preset temperature interval, and maintain a preset fixed time at each temperature point;

[0019] Measure the temperature of the pyranometer and the output signal value of the pyranometer in real time, determine the relationship between the output signal value of the pyranometer and the temperature change of the pyranometer, and obtain the temperature response data set y(T) of the pyranometer.

[0020] In one possible implementation, simulate solar radiation to obtain the sensitivity data set of the pyranometer under different irradiances, including:

[0021] Set the temperature and humidity of the environment where the pyranometer and the photovoltaic module are located to fixed values, adjust the irradiance of the simulated solar radiation, collect the measurement data of the pyranometer, and calculate the ratio of the measurement value of the pyranometer to the irradiance under different irradiation conditions to obtain the sensitivity data set k(E) of the pyranometer under different irradiances.

[0022] In one possible implementation, perform temperature correction on the measured irradiance of the pyranometer, including:

[0023] Based on the temperature data of the pyranometer obtained by real-time measurement, by comparing the temperature difference between the pyranometer at the photovoltaic power generation site and the pyranometer during calibration, and combining with the correction coefficient set, determine the temperature correction factor, expressed as:

[0024]

[0025] Among them, M T is the temperature correction factor, y(T0) is the data value at the total radiometer temperature during sensitivity calibration in the temperature response dataset, and y(T1) is the data value at the total radiometer temperature during actual irradiance measurement in the temperature response dataset.

[0026] In one possible implementation, the angular correction of the irradiance measured by the total radiometer includes:

[0027] Measuring the relative distribution E r (α, θ) of solar irradiance at each azimuth angle and inclination angle within the receiving surface of the photovoltaic module at the photovoltaic power generation site; performing angular correction calculation, expressed as:

[0028]

[0029] Among them, E r (α, θ) is the relative solar irradiance data at different azimuth angles α and inclination angles θ within the receiving surface of the photovoltaic module, S p (θ) is the angular response data of the total radiometer normalized by the maximum value, and S M (θ) is the angular response data of the photovoltaic module normalized by the maximum value.

[0030] In one possible implementation, the sensitivity linear correction of the irradiance measured by the total radiometer includes:

[0031]

[0032] Among them, M k is the sensitivity linear correction factor, k(E0) is the total radiation sensitivity adopted during the measurement by the total radiometer, and k(E1) is the sensitivity of the total radiometer under the actual measured irradiance.

[0033] In one possible implementation, the spectral mismatch correction of the irradiance measured by the total radiometer includes:

[0034] Based on the spectrally resolved irradiance obtained from real-time measurement, combining the irradiance linear response data of the total radiometer and the photovoltaic module, performing spectral mismatch correction on the irradiance measured by the total radiometer after temperature correction and angular correction to obtain the effective solar irradiance data of the photovoltaic; among them, the spectral mismatch correction coefficient is expressed as:

[0035]

[0036] In the formula, SMM is the spectral mismatch correction coefficient, and E ref(λ) is the irradiance distribution of the AM1.5G standard solar spectrum, E meas (λ) is the measured spectral irradiance distribution, and s(λ) is the spectral responsivity data of the photovoltaic module.

[0037] In one possible implementation, the irradiance measured by the pyranometer is corrected for temperature, angle, linearity, and spectral mismatch. The correction formula is as follows:

[0038] E S = E M · M T · M A · M k · SMM

[0039] Among them, E S is the measured value of the effective solar irradiance of the photovoltaic, E M is the solar irradiance measured by the pyranometer, M T is the temperature correction factor, M A is the angle correction factor, M k is the sensitivity linear correction factor, and SMM is the spectral mismatch correction coefficient.

[0040] Compared with the prior art, the technical solution provided by this application has the following beneficial effects:

[0041] By establishing a pyranometer standard traceable to the International System of Units (SI), and using a cryogenic radiometer to calibrate the spectral radiant power responsivity of the standard detector, the traceability of the irradiance value of the absolute radiometer is achieved, ensuring a low uncertainty in the calibration of the pyranometer. By building an outdoor calibration device for the pyranometer, using a solar tracker to transfer the solar irradiance value from the absolute radiometer to the pyranometer, and collecting relevant data separately in the occluded and non-occluded states, the calibration sensitivity of the pyranometer is calculated, thereby improving the measurement accuracy of the pyranometer.

[0042] By simulating solar radiation, the angular response, temperature response, and irradiance linear response data of the pyranometer and the photovoltaic module under various influencing parameters are obtained, and a set of correction coefficients is obtained through fitting and interpolation methods. At the photovoltaic power generation site, the irradiance measured by the pyranometer, spectral irradiance, pyranometer temperature data, and the relative distribution data of solar radiation at various angles in the hemispherical space of the receiving surface of the photovoltaic module are synchronously collected. Combining the set of correction coefficients, the irradiance measured by the pyranometer is corrected for temperature, angle, and spectral mismatch, and finally the effective solar irradiance data of the photovoltaic is obtained, effectively reducing the measurement deviation of solar irradiance introduced by the spectral response difference, angular response difference, calibration condition and application condition difference between the pyranometer and the photovoltaic module, thereby achieving accurate measurement of solar irradiance for photovoltaic power generation. Description of the Drawings

[0043] Figure 1 Schematic diagram of a structure of an absolute radiation metrology traceability device provided in the first embodiment of the present application.

[0044] Figure 2 Schematic diagram of a structure of an outdoor calibration device for a pyranometer provided in the first embodiment of the present application.

[0045] Figure 3 Schematic diagram of a structure of a device for measuring the environmental temperature, humidity, angle, and irradiance responses of a pyranometer and a photovoltaic module provided in the first embodiment of the present application.

[0046] Figure 4 Schematic diagram of a structure of a device for measuring the effective solar irradiance of a photovoltaic provided in the first embodiment of the present application.

[0047] Figure 5 Flowchart of a method for measuring the effective solar irradiance of a photovoltaic provided in the second embodiment of the present application. Specific embodiments

[0048] Next, in combination with the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present application.

[0049] To solve the problems raised in the background art, the present application proposes to establish a pyranometer standard traceable to the International System of Units (SI) to reduce the uncertainty of pyranometer calibration. Through performance comprehensive evaluation and real-time measurement and correction technology of environmental meteorological parameters, the measurement deviation of solar irradiance introduced by the spectral response difference, angle response difference, calibration condition and application condition difference between the pyranometer and the photovoltaic module for photovoltaic power generation, etc. is reduced, and the measurement deviation of solar irradiance for photovoltaic power generation is realized, and the accurate measurement of solar irradiance for photovoltaic power generation is realized.

[0050] Next, the technical solutions provided by the present application will be elaborated in detail in combination with specific embodiments.

[0051] Embodiment 1

[0052] See Figure 1 , which is a schematic diagram of a structure of an absolute radiation metrology traceability device provided in the first embodiment of the present application. The absolute radiation metrology traceability device realizes SI unit system traceability by tracing the measurement results of the absolute radiometer to the cryogenic radiometer, thereby ensuring that a traceability route with low uncertainty can be constructed.

[0053] Specifically, as shown in Figure 1As shown in the figure, the above-mentioned absolute radiation measurement value traceability device includes components such as an absolute radiometer, a monitoring detector, a precision aperture, a beam splitter, an expanding and collimating mirror, an aspherical beam shaper, a Gaussian beam, an adjustable magnification expanding and collimating mirror, a spatial filter, a reflector, a feedback detector, a laser power stabilizer, and a laser.

[0054] In the embodiment of the present application, first, the spectral radiation power responsivity of the standard detector is calibrated by a cryogenic radiometer to determine its response characteristics to radiation power under different spectra. Its response characteristics serve as a stable starting point for the transfer of quantity values, and are used to gradually transfer the high-precision quantity values of the cryogenic radiometer to other measurement links and instruments through the standard detector, ensuring the accuracy and reliability of the entire traceability chain. Specifically, when using the comparison method to trace the radiation exposure quantity value of the absolute radiometer to the cryogenic radiometer, the measurement result of the absolute radiometer is traced back to the cryogenic radiometer through relevant measurements and comparisons with the standard detector, etc., establishing a connection with the International System of Units (SI), completing the process of quantity value transfer, and ensuring the accuracy and traceability of the measurement result of the absolute radiometer.

[0055] As an optical element used to limit the area through which a light beam passes, the effective light-transmitting area of the aperture determines the number of light beams that can pass through the aperture and reach the measurement area. When calculating the radiation exposure quantity value, it is necessary to determine the area receiving the light radiation, that is, it is necessary to determine the effective light-transmitting area of the aperture. In the embodiment of the present application, the above-mentioned effective light-transmitting area of the aperture is obtained through direct measurement. Then, in combination with the effective light-transmitting area of the aperture, the radiation exposure quantity value is traced back to the cryogenic radiometer and the effective light-transmitting area, thereby establishing an accurate mathematical relationship between the actually measured radiation exposure quantity value, the radiation power measured by the cryogenic radiometer, and the effective light-transmitting area of the aperture. Using the radiation power measured by the cryogenic radiometer and the effective light-transmitting area of the aperture, the irradiance can be calculated. In this way, the actually measured irradiance can be determined by these two reference quantities, namely the cryogenic radiometer and the effective light-transmitting area of the aperture, realizing traceability with low uncertainty and ensuring the accuracy and reliability of the measurement result.

[0056] The above technical solution provided by the embodiment of the present application traces the measurement result back to these two basic and accurately known quantities, namely the cryogenic radiometer and the effective light-transmitting area of the aperture. No matter when and where the radiation irradiance measurement is carried out, as long as the same traceability method and standard are followed, the measurement results can be compared and communicated under the unified standard, thereby ensuring the scientific nature and authority of the measurement results.

[0057] Furthermore, the embodiments of the present application also propose that when measuring the irradiance value to be traced based on an absolute radiometer, a laser is used as the initial light source. The laser generates an initial laser beam, and the initial laser beam is shaped by an aspherical beam shaping component to meet the requirements of multi-wavelength, high power, and uniform light spot, providing a high-quality beam for the subsequent measurement of the absolute radiometer.

[0058] After completing the traceability to the SI unit system, the next more important thing is how to further apply and expand this high-precision traceability result. As a measuring instrument widely used in various fields such as meteorology and environmental monitoring, the accuracy of the pyranometer is also crucial. Therefore, how to calibrate the pyranometer using the absolute radiometer that has been traced to the SI unit system has become the key problem to be solved in the next step.

[0059] See Figure 2 , which is a schematic structural diagram of an outdoor calibration device for a pyranometer provided in Embodiment 1 of the present application. As Figure 2 shown in, the above-mentioned outdoor calibration device for a pyranometer includes a solar tracker, a pyranometer to be calibrated, a monitoring radiometer, an absolute radiometer standard, a multi-channel data collector, and a movable test bench.

[0060] Based on the outdoor solar light source, the embodiments of the present application use the solar tracker as the platform carrier to transfer the solar irradiance value from the absolute radiometer to the pyranometer. The specific implementation process is as follows:

[0061] (1) Place the pyranometer to be calibrated and the monitoring radiometer in the horizontal plane, and the normal of the receiving surface of the absolute radiometer directly faces the sun.

[0062] (2) The shading sphere / plate is controlled by a motor, and the test area of the pyranometer to be calibrated can be shielded and unshielded.

[0063] (3) Measure the solar irradiance value output by the absolute radiometer, the signal output of the pyranometer to be calibrated, the signal output of the monitoring radiometer, and the zenith angle data in the unshielded state.

[0064] (4) Adjust the motor to make the test area of the pyranometer to be calibrated in the shielded state, and measure the signal output of the pyranometer to be calibrated and the signal output of the monitoring radiometer.

[0065] (5) Calculate the calibration sensitivity of the pyranometer to be calibrated using the following formula, expressed as:

[0066]

[0067] In the formula, k0 is the calibration sensitivity of the pyranometer, V1 is the output voltage of the pyranometer in the unshielded state, V2 is the output voltage of the pyranometer in the shielded state, V01 V is the output voltage of the pyranometer when it is in the unobstructed state, monitoring the pyranometer. 02 α is the zenith angle of the pyranometer in the unobstructed state, and Vα is the output voltage of the pyranometer when it is in the obstructed state. E d is the solar irradiance output by the absolute radiometer when the pyranometer is in the unobstructed state.

[0068] Furthermore, due to the spectral response differences, angular response differences between the pyranometer and the photovoltaic modules for photovoltaic power generation, as well as the differences between the calibration conditions and application conditions of the pyranometer, these factors will inevitably introduce measurement biases in solar irradiance. Therefore, this application proposes to reduce the measurement biases in solar irradiance introduced by the spectral response differences, angular response differences, calibration conditions and application differences between the pyranometer and the photovoltaic modules for photovoltaic power generation through performance comprehensive evaluation and real-time measurement and correction techniques of environmental meteorological parameters, so as to achieve accurate measurement of solar irradiance for photovoltaic power generation.

[0069] Specifically, refer to Figure 3 , which is a schematic structural diagram of a device for measuring the environmental temperature, humidity, angle and irradiance response of a pyranometer and a photovoltaic module provided in Embodiment 1 of this application. As Figure 3 shown in, the above device includes a highly collimated solar simulation light source, a programmable environmental temperature and humidity test chamber, a data acquisition and control unit, a monitoring detector and an industrial computer.

[0070] In the embodiment of this application, a highly collimated solar simulator is used as the light source to simulate solar radiation and provide approximate real lighting conditions for the pyranometer and the photovoltaic module. The pyranometer and the photovoltaic module are placed in the programmable environmental temperature and humidity test chamber. The programmable environmental temperature and humidity test chamber is provided with a light passing hole on the side, and the light passing hole uses quartz glass as the window to ensure the stability of environmental conditions such as temperature and humidity in the chamber while allowing light to enter. As Figure 3 shown in, a high-precision angle adjustment device is also provided in the programmable environmental temperature and humidity test chamber. The above high-precision angle adjustment device is electrically controlled by the data acquisition and control unit. The high-precision angle adjustment device responds to the control instructions of the data acquisition and control unit to adjust the angles of the pyranometer and the photovoltaic module, including the tilt angle, azimuth angle, etc., so as to simulate the angles between the sun rays and the pyranometer and the photovoltaic module at different times and seasons, and determine the measurement errors of the pyranometer at various angles.

[0071] The monitoring detector is placed outside the programmable environmental temperature and humidity test chamber and is used to monitor the change in the irradiance of the light source of the solar simulator for correction. Specifically, the monitoring detector monitors the irradiance of the light source of the highly collimated solar simulator in real time, determines the real-time change in the irradiance of the light source, and sends the above real-time change to the data acquisition and control unit. The data acquisition and control unit adjusts the irradiance of the light source of the highly collimated solar simulator according to the above real-time change, so as to output stable simulated solar radiation, thereby reducing the error caused by the instability of the light source.

[0072] Through the above device, the angle response data, temperature response data, and irradiance linear response data of the pyranometer and the photovoltaic module are measured respectively under different conditions in the embodiments of the present application, which are used to evaluate the performance of the pyranometer and the photovoltaic module under different environmental conditions, so as to facilitate angle correction, temperature correction, spectral correction, etc. of the measured solar irradiance, to compensate for the measurement deviation of solar irradiance caused by changes in angle, temperature, and irradiance, and improve the accuracy and reliability of the measurement. The specific measurement methods of the angle response, temperature response, and sensitivity data under different irradiances are as follows.

[0073] For the measurement of the angle response, based on the above data acquisition and control unit to control the high-precision angle adjustment device, the tilt angle of the pyranometer or the photovoltaic module is adjusted at a preset angle interval. At the same time, the monitoring detector is used to monitor the change in the irradiance of the light source of the solar simulator in real time, and then the data acquisition and control unit collects the output signal of the pyranometer or the output short-circuit current parameter of the photovoltaic module to determine the relationship between the output signal of the pyranometer or the output short-circuit current of the photovoltaic module and the angle change, and obtains the angle response data of the pyranometer and the photovoltaic module respectively. Further, the present application divides the angle response data of the pyranometer and the photovoltaic module by the maximum value in their respective angle response data to obtain the angle response data S p (θ) of the pyranometer and the angle response data S M (θ) of the photovoltaic module.

[0074] For the measurement of the temperature response, in the embodiments of the present application, the irradiance of the highly collimated solar simulator is set to a constant solar irradiance value. The data acquisition and control unit is used to set the temperature of the programmable environmental chamber, gradually change the environmental temperature according to the preset temperature interval, and maintain the preset fixed time at each temperature point. During this period, the change in the irradiance of the light source of the solar simulator is monitored and corrected in real time by the monitoring detector, and the measurement data of the pyranometer or the output electrical parameters of the photovoltaic module are collected, so as to determine the relationship between the output signal value of the pyranometer and the temperature change of the pyranometer, and obtain the temperature response data set y(T) of the pyranometer.

[0075] For the sensitivity measurement under different irradiances, the embodiments of the present application set the temperature and humidity of the programmable environmental chamber to fixed standard values to ensure stable environmental conditions. The irradiance of the high-collimation solar simulator is adjusted by the data acquisition and control unit, and the irradiance value is sequentially changed in the ascending or descending order of the preset irradiance. At each irradiance, the monitoring detector is used to monitor and correct the change of the irradiance of the solar simulator light source in real time, and then the measurement data of the pyranometer or the output electrical parameters of the photovoltaic module are collected, so as to determine the relationship between the irradiance change and the measurement value of the pyranometer or the short-circuit current parameter of the photovoltaic module output, and obtain the sensitivity data set k(E) of the pyranometer under different irradiances.

[0076] Further, to realize the angle correction, temperature correction, sensitivity linear correction and spectral mismatch correction of the measured solar irradiance, the embodiments of the present application obtain the correction coefficient sets of the pyranometer and the photovoltaic module under different influence parameters and different magnitudes through the fitting interpolation method.

[0077] In a specific application scenario, see Figure 4 , a pyranometer, a spectrometer and a hemispherical irradiance scanner are arranged at the photovoltaic power generation site. Among them, the pyranometer is placed parallel and coplanar with the photovoltaic module to measure the total solar irradiance at different times. The probe of the spectrometer is placed parallel and coplanar with the photovoltaic module to measure the spectral irradiance data at different times. The hemispherical irradiance scanner is placed parallel and coplanar with the photovoltaic module to measure the angular distribution of the solar irradiance in the hemispherical space of the receiving surface of the photovoltaic module. At multiple times, the measured irradiance of the pyranometer, the temperature of the pyranometer, the spectral irradiance data and the distribution data of the direct / diffuse light in the hemispherical surface with the angle are measured simultaneously.

[0078] Based on the data obtained from the above measurements and the above correction coefficient sets, the solar irradiance measured by the pyranometer is corrected in real time online, specifically including:

[0079] Based on the temperature data of the pyranometer obtained by real-time measurement, by comparing the temperature difference between the pyranometer at the photovoltaic power generation site and the temperature at the time of calibration of the pyranometer, and combining the key parameter correction coefficient set of the pyranometer obtained in step three, the temperature correction of the measured solar irradiance is carried out, and the correction factor is as follows:

[0080]

[0081] Among them, M T is the temperature correction factor, y(T0) is the data value at the temperature of the pyranometer during sensitivity calibration in the temperature response data set, and y(T1) is the data value at the temperature of the pyranometer during the actual irradiance test in the temperature response data set.

[0082] The angle correction of the irradiance measured by the pyranometer specifically includes:

[0083] Using a hemispherical space irradiance scanner, the relative distribution data of solar radiation at various angles in the hemispherical space of the receiving surface of the photovoltaic module is measured in real time. The relative distribution data of solar radiation at various angles is normalized (the sum is 1) to obtain the relative distribution data of solar irradiance at various angles in the normalized hemispherical space. Multiply the measured irradiance of the pyranometer after temperature correction by the relative distribution data of solar irradiance at various angles in the normalized hemispherical space to obtain the absolute value of the solar irradiance data at various angles measured by the pyranometer. Multiply the absolute value of the solar irradiance data at various angles measured by the pyranometer by the angular responsivity correction factor at the corresponding angles of the pyranometer to obtain the absolute value data of the solar irradiance at various angles actually incident on the surface of the photovoltaic module, which is expressed as:

[0084]

[0085] In the formula, E r (α, θ) is the relative solar irradiance data at different azimuth angles α and tilt angles θ in the receiving surface of the photovoltaic module, S p (θ) is the pyranometer angular response data normalized by the maximum value, S M (θ) is the angular response data of the photovoltaic module normalized by the maximum value.

[0086] Perform a sensitivity linear correction on the measured irradiance of the pyranometer, specifically including obtaining a sensitivity linear correction factor and performing a sensitivity linear correction on the measured irradiance of the pyranometer based on the above sensitivity linear correction factor. Among them, the above sensitivity linear correction factor is expressed as:

[0087]

[0088] Among them, M k is the sensitivity linear correction factor, k(E0) is the total radiation sensitivity used when the pyranometer is measured, and k(E1) is the pyranometer sensitivity under the actually measured irradiance.

[0089] Perform a spectral mismatch correction on the measured irradiance of the pyranometer, specifically including:

[0090] Based on the spectral irradiance data obtained by real-time measurement, combined with the irradiance linear response data of the pyranometer and the photovoltaic module, use the following formula to perform a spectral mismatch correction on the measured irradiance of the pyranometer after temperature and angle correction to obtain the effective solar irradiance data of the photovoltaic. Among them, the spectral mismatch correction coefficient is expressed as:

[0091]

[0092] In the formula, SMM is the spectral mismatch correction coefficient, E refE(λ) is the standard solar spectral irradiance distribution of AM1.5G, and E meas E(λ) is the measured spectral irradiance distribution, and s(λ) is the spectral responsivity data of the photovoltaic module.

[0093] Based on the temperature correction factor, angle correction factor, sensitivity linear correction factor, and spectral mismatch correction coefficient obtained above, the irradiance measured by the pyranometer is corrected to obtain the final measured value of the effective solar irradiance of the photovoltaic, which is expressed as:

[0094] E S = E M ·M T ·M A ·M k ·SMM

[0095] Among them, E S is the measured value of the effective solar irradiance of the photovoltaic, E M is the solar irradiance measured by the pyranometer, M T is the temperature correction factor, M A is the angle correction factor, M k is the sensitivity linear correction factor, and SMM is the spectral mismatch correction coefficient.

[0096] Compared with the prior art, the technical solution provided in the first embodiment of the present application has the following beneficial effects:

[0097] By constructing a complete set of measurement and calibration systems, high-precision measurement of the effective solar irradiance of the photovoltaic is achieved. Specifically, by building an outdoor calibration device for the pyranometer, combining an absolute radiometer, a monitoring radiometer, and a pyranometer that trace back to the International System of Units (SI), key data can be collected in both shaded and non-shaded states, thereby accurately calculating the calibration sensitivity of the pyranometer, ensuring high precision and low uncertainty of the pyranometer during the calibration process, and providing a reliable basis for subsequent measurements.

[0098] By introducing a highly collimated solar simulation light source and a programmable environmental temperature and humidity test chamber, real solar radiation conditions are simulated, and at the same time, environmental parameters are precisely controlled, providing a stable experimental environment for measuring the angle response, temperature response, and irradiance linear response data of the pyranometer and photovoltaic modules. Through the set of correction coefficients obtained by the fitting interpolation method, combined with the real-time measurement data on the photovoltaic power generation site, the device can perform temperature correction, angle correction, and spectral mismatch correction on the measurement results of the pyranometer, thereby improving the accuracy and reliability of the measurement of the effective solar irradiance of the photovoltaic.

[0099] Embodiment Two

[0100] Based on each device provided in Embodiment One, Embodiment Two of the present application elaborates in detail on the method for measuring the effective solar irradiance of the photovoltaic. SeeFigure 5 , which is a flowchart of a method for measuring the effective solar irradiance of a photovoltaic provided in the second embodiment of the present application. As Figure 5 shown, the specific steps of the above method include:

[0101] Step 100: Build an absolute radiometer calibration device. Based on a laser as the light source, use a trap detector for cryogenic radiometric transfer as the optical power standard. Through a precision aperture with accurately calibrated area, convert the optical power into irradiance, and realize the traceability of the absolute radiometer measurement value to the SI unit system through the comparison method.

[0102] The present application first reduces the uncertainty of the pyranometer calibration by establishing a pyranometer calibration method traceable to the SI unit system. Specifically, use a cryogenic radiometer to calibrate the standard detector and determine its spectral irradiance responsivity at different spectra. Then, through the comparison method, trace the irradiance measurement value obtained by the absolute radiometer to the cryogenic radiometer to ensure the accuracy and traceability of its measurement results. During this process, it is necessary to directly measure the effective light-transmitting area of the aperture and combine the above effective light-transmitting area to trace the irradiance measurement value to the cryogenic radiometer, thereby establishing a complete traceability system and realizing a low-uncertainty traceability route for the absolute radiometer.

[0103] Step 101: Build an outdoor pyranometer calibration device, including an absolute radiometer traceable to the SI, a monitoring pyranometer, and a pyranometer.

[0104] For the above outdoor pyranometer calibration device, based on the outdoor solar light source and using a solar tracker as the platform carrier, place the pyranometer in the horizontal plane and the normal of the receiving surface of the absolute radiometer directly facing the sun. By switching the shielding and non-shielding states of the shading sphere / plate, measure the solar irradiance output by the absolute radiometer, the signal output of the pyranometer, the signal output of the monitoring pyranometer, and the zenith angle data respectively. According to the measurement data, calculate the calibration sensitivity of the pyranometer to realize the transfer of the absolute radiometer measurement value to the pyranometer and improve the measurement accuracy of the pyranometer.

[0105] Step 102: Respectively collect the signal outputs of the absolute radiometer, the monitoring pyranometer, and the pyranometer in the shielded state and non-shielded state of the pyranometer, including the output voltage of the pyranometer and the output voltage of the monitoring pyranometer, the zenith angle of the pyranometer in the non-shielded state, and the solar irradiance output by the absolute radiometer, and calibrate the sensitivity of the pyranometer based on the above signal outputs.

[0106] Specifically, according to the output voltage of the pyranometer and the output voltage of the monitoring pyranometer, the zenith angle of the pyranometer in the non-shielded state, and the solar irradiance output by the absolute radiometer, determine the calibration sensitivity of the pyranometer, expressed as:

[0107]

[0108] In the formula, k0 is the calibration sensitivity of the pyranometer, V1 is the output voltage of the pyranometer in the non-occluded state, V2 is the output voltage of the pyranometer in the occluded state, V 01 is the output voltage of the monitoring radiometer when the pyranometer is in the non-occluded state, V 02 is the output voltage of the monitoring radiometer when the pyranometer is in the occluded state, α is the zenith angle of the pyranometer in the non-occluded state, E d is the solar irradiance output by the absolute radiometer when the pyranometer is in the non-occluded state.

[0109] Step 103: Measure the spectral responsivity data of the pyranometer and the photovoltaic module. Simulate solar radiation to obtain the angular response, temperature response, and irradiance linear response data of the pyranometer and the photovoltaic module under various influencing parameters. Among them, the above-mentioned influencing parameters include the included angle between the pyranometer and the photovoltaic module, temperature and humidity, and light source irradiance.

[0110] Specifically, place the pyranometer and the photovoltaic module in a programmable environmental temperature and humidity test chamber, use a highly collimated solar simulation light source as the light source to simulate real lighting conditions. Control the high-precision angle adjustment device through the data acquisition and control unit to adjust the inclination angle and azimuth angle of the pyranometer or the photovoltaic module respectively. At the same time, use the monitoring detector to monitor and correct the change of the light source irradiance in real time, collect measurement data and output electrical parameters, and determine the angular responsivity of the pyranometer at various angles. In addition, by setting a constant solar irradiance value and gradually changing the environmental temperature according to a preset temperature interval, determine the temperature responsivity of the pyranometer at various temperatures. And, by changing the irradiance value according to a preset irradiance sequence, determine the irradiance linear responsivity of the pyranometer.

[0111] Step 104: Obtain the correction coefficient sets of the pyranometer and the photovoltaic module under various influencing parameters through the fitting interpolation method.

[0112] Step 105: Synchronously collect the measured irradiance, spectral irradiance, pyranometer temperature data of the pyranometer and the relative distribution data of solar radiation at various angles in the hemispherical space of the receiving surface of the photovoltaic module at the photovoltaic power generation site. Combine the above correction coefficient sets to correct the measured irradiance of the pyranometer, including temperature correction, angle correction, and spectral mismatch correction, to obtain the effective solar irradiance data of the photovoltaic.

[0113] Specifically, at the photovoltaic power generation site, a pyranometer, a spectrometer, and a hemispherical irradiance scanner are arranged to be placed parallel and coplanar with the photovoltaic modules. At multiple moments, the irradiance measured by the pyranometer, the temperature of the pyranometer, the spectral irradiance data, and the distribution data of direct / diffuse light with angles within the hemispherical surface are measured simultaneously. Based on the temperature data of the pyranometer obtained from real-time measurement and in combination with the key parameter correction coefficient set of the pyranometer, temperature correction is performed on the measured solar irradiance. Using the relative distribution data of solar irradiance at each angle in the normalized hemispherical space measured by the hemispherical space irradiance scanner, angle correction is performed on the irradiance measured by the pyranometer. Finally, based on the spectral irradiance distribution data obtained from real-time measurement and in combination with the irradiance linear response data of the pyranometer and the photovoltaic modules, spectral mismatch correction is performed on the irradiance measured by the pyranometer after temperature and angle correction, so as to obtain the photovoltaic effective solar irradiance data.

[0114] It should be noted that the specific real-time steps of the method provided in the second embodiment of the present application can be combined with the first embodiment, and will not be elaborated here. Although the embodiments of the present application have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for measuring photovoltaic effective solar irradiance, characterized in that: include: Build an absolute radiometer calibration device, use laser as light source, use low temperature radiometer transmission trap detector as optical power standard, use precision aperture to convert optical power into irradiance, and trace the absolute radiometer value to SI unit system by comparison method; Set up an outdoor pyranometer calibration setup, including an absolute radiometer, a monitoring pyranometer and a pyranometer traceable to SI units; The signal outputs of the absolute radiometer, the monitoring radiometer and the pyranometer are respectively collected when the pyranometer is in a shielded state and an unshielded state, including the output voltage of the pyranometer and the output voltage of the monitoring radiometer, the zenith angle of the pyranometer in an unshielded state and the solar irradiance output by the absolute radiometer, and the pyranometer is calibrated based on the signal outputs; Measure pyranometer and photovoltaic module spectral responsivity data; Simulate solar radiation, obtain the angle response, temperature response, and sensitivity data set of the pyranometer and photovoltaic module under various influencing parameters, and obtain the correction coefficient set of the pyranometer and photovoltaic module under various influencing parameters through fitting interpolation method; the influencing parameters include the incident angle, temperature and humidity, irradiance, and spectral response of the pyranometer and photovoltaic module; At the photovoltaic power generation site, the irradiance measured by the global pyranometer, spectral irradiance, global pyranometer temperature data and the relative distribution data of solar radiation at various angles in the hemispherical space of the photovoltaic module receiving surface are synchronously collected. Combined with the correction coefficient set, the irradiance measured by the global pyranometer is corrected, including temperature correction, angle correction, sensitivity linear correction and spectral mismatch correction, to obtain the photovoltaic effective solar irradiance data.

2. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: The sensitivity of the pyranometer is calibrated based on the signal outputs of the absolute radiometer, the monitoring radiometer and the pyranometer in both the shaded and unshaded states, including: The calibration sensitivity of the pyranometer is determined based on the output voltage of the pyranometer and the output voltage of the monitoring pyranometer, the zenith angle of the pyranometer in the unshielded state, and the solar irradiance output by the absolute radiometer, which is expressed as: Where k0 is the calibration sensitivity of the pyranometer, V1 is the output voltage of the pyranometer in the unshielded state, V2 is the output voltage of the pyranometer in the shielded state, and V 01 The output voltage of the pyranometer is monitored when the pyranometer is in the unblocked state, V 02 is the output voltage of the pyranometer when it is blocked, α is the zenith angle of the pyranometer when it is not blocked, and E d It is the solar irradiance output by the absolute radiometer when the pyranometer is in an unobstructed state.

3. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: Simulate solar radiation and obtain angular response data of pyranometers and photovoltaic modules, including According to the preset angle interval, the inclination angle of the pyranometer and the photovoltaic module is adjusted, and the change of the irradiance of the light source simulating solar radiation is monitored and corrected in real time. The output signal of the pyranometer or the output short-circuit current parameter of the photovoltaic module is collected, and the relationship between the output signal of the pyranometer or the output short-circuit current of the photovoltaic module and the angle change is determined to obtain the angle response data of the pyranometer and the photovoltaic group respectively, and the angle response data of the pyranometer and the photovoltaic module are divided by the maximum value of their respective angle response data to obtain the pyranometer angle response data S normalized by the maximum value. p (θ) and PV module angle response data S M (θ).

4. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: Simulate solar radiation and obtain temperature response data of the pyranometer, including: The irradiance of the simulated solar radiation is set to a constant solar irradiance value, the ambient temperature is gradually changed based on a preset temperature interval, and a preset fixed time is maintained at each temperature point; The temperature of the pyranometer and the output signal value of the pyranometer are measured in real time, the relationship between the output signal value of the pyranometer and the temperature change of the pyranometer is determined, and the temperature response data set y(T) of the pyranometer is obtained.

5. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: Simulate solar radiation and obtain the sensitivity data set of the pyranometer under different irradiances, including: The temperature and humidity of the environment where the pyranometer and photovoltaic modules are located are set to fixed values. By adjusting the irradiance of simulated solar radiation, the measurement data of the pyranometer are collected, and the ratio of the pyranometer measurement value to the irradiance under different irradiance conditions is calculated to obtain the sensitivity data set k(E) of the pyranometer under different irradiances.

6. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: Temperature correction of irradiance measured by pyranometer, including: Based on the temperature data of the pyranometer measured in real time, the temperature correction factor is determined by comparing the temperature difference between the pyranometer at the photovoltaic power generation site and the temperature difference during calibration, combined with the correction coefficient set, and expressed as: Among them, M T is the temperature correction factor, y(T0) is the data value at the pyranometer temperature during sensitivity calibration in the temperature response dataset, and y(T1) is the data value at the pyranometer temperature during actual irradiance testing in the temperature response dataset.

7. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: Angle correction for irradiance measured by pyranometer, including: Measure the relative distribution of solar irradiance E at various azimuths and inclinations within the receiving surface of photovoltaic modules at photovoltaic power generation sites r (α, θ); perform angle correction calculation, expressed as: Among them, E r (α, θ) is the relative solar irradiance data at different azimuth angles α and inclination angles θ within the receiving surface of the photovoltaic module, S p (θ) is the angular response data of the pyranometer normalized to the maximum value, S M (θ) is the angular response data of the photovoltaic module normalized to the maximum value.

8. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: Perform linear sensitivity correction on the irradiance measured by the pyranometer, including: Among them, M k is the sensitivity linear correction factor, k(E0) is the global radiation sensitivity used in the global radiation meter measurement, and k(E1) is the global radiation meter sensitivity under the actual measured irradiance.

9. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: Spectral mismatch correction for pyranometer-measured irradiance, including: Based on the spectral irradiance obtained by real-time measurement, combined with the irradiance linear response data of the pyranometer and photovoltaic modules, the spectral mismatch correction is performed on the irradiance measured by the pyranometer after temperature correction and angle correction to obtain the photovoltaic effective solar irradiance data; the spectral mismatch correction coefficient is expressed as: Where SMM is the spectral mismatch correction factor, E ref (λ) is the AM1.5G standard solar spectrum irradiance distribution, E meas (λ) is the measured spectral irradiance distribution, and s(λ) is the spectral responsivity data of the photovoltaic module.

10. A photovoltaic effective solar irradiance measurement method according to claim 1, characterized in that: The irradiance measured by the pyranometer is corrected for temperature, angle, linearity, and spectral mismatch. The correction formula is as follows: E S =E M ·M T ·M A ·M k ·SMM Among them, E S is the measured value of photovoltaic effective solar irradiance, E M is the solar irradiance measured by the pyranometer, M T is the temperature correction factor, M A is the angle correction factor, M k is the sensitivity linear correction factor, and SMM is the spectral mismatch correction coefficient.

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