Photovoltaic cell panel invisible defect detection device based on multispectral imaging

Abstract

The invention discloses a photovoltaic cell panel invisible defect detection device based on multispectral imaging. The photovoltaic cell panel invisible defect detection device comprises a photovoltaic cell panel to be detected; the excitation module is configured to enable the photovoltaic cell panel to be detected to generate a short-wave infrared band under the irradiation of an excitation light source; the excitation light source comprises a near-infrared light-induced excitation light source and / or an electroluminescent driving power supply; the spectrum acquisition module comprises a multispectral imaging system composed of a variable optical filter and an area-array camera, the variable optical filter adopts a wavelength programmable narrow-band filtering assembly, and the transmission wavelength of the variable optical filter covers a 1050-1250 nm characteristic spectrum band; and the image acquisition and processing system is configured to control switching of spectrum channels of the variable optical filter, control the area-array camera to shoot multispectral images in sequence and process the images. The device overcomes the adverse effect of the sunlight environment on photoluminescence imaging or electroluminescence imaging of the photovoltaic cell panel, so that the imaging level of invisible defects of the photovoltaic cell panel is improved.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic panel applications, and particularly to a photovoltaic panel invisible defect detection device based on multi-photovoltaic imaging. Background Technique

[0002] Silicon crystal photovoltaic panel components are key devices in solar power generation systems. Due to various reasons, there are often various invisible defects inside silicon crystal photovoltaic panel components, including corner missing, hidden crack, fragmentation, black spot, broken grid, surface contamination, local heating, etc. These defects are important factors affecting the photoelectric conversion efficiency and service life of photovoltaic panel components, and even pose safety problems. Therefore, it is necessary to detect these invisible defects during the use of photovoltaic panel components to eliminate potential hazards.

[0003] Currently, the online detection technologies for invisible defects of photovoltaic panel components include infrared thermal imaging, electroluminescence imaging, photoluminescence imaging, I-V curve characteristic detection and analysis, etc. Among them, electroluminescence imaging and photoluminescence imaging technologies have the advantages of high detection sensitivity, high detection efficiency, and the ability to detect various types of defects, and have been widely used in the field of photovoltaic panel defect detection. The so-called electroluminescence is to apply a certain reverse voltage to the PN junction of a photovoltaic panel to induce it to emit light of a certain wavelength; while photoluminescence is to irradiate the semiconductor material of a photovoltaic panel with light of a certain wavelength to stimulate it to emit light of a certain wavelength. The spectral energy of electroluminescence or photoluminescence of silicon crystal materials is mainly concentrated in the short-wave infrared range of wavelengths from 1050nm to 1250nm; under the background of these electroluminescence or photoluminescence, various invisible defects of photovoltaic panels are revealed, thus creating conditions for imaging. However, compared with the daylight radiation intensity on the ground during the day, the radiation intensity of electroluminescence or photoluminescence of photovoltaic panels is very limited. Therefore, in order to avoid being interfered by daylight, most of the existing electroluminescence imaging and photoluminescence imaging technologies are used in indoor or darkroom environments. However, most of the existing photovoltaic panel components operate in outdoor daylight environments, so it is necessary to develop electroluminescence and photoluminescence imaging technologies under high irradiance during the day.

[0004] Among existing invention patents, the patent documents of Chinese Invention Patent Publication No. CN118199517A, with the patent name "Photoluminescence Imaging System and Method for Photovoltaic Panels Based on Linear Array InGaAs Camera", and Chinese Invention Patent Publication No. CN201340393Y, with the patent name "On-line Detection Device for Defects of Reflective Solar Cell Modules", do not involve imaging detection in daylight environment; the patent documents of World Invention Patent Publication No. WO2011152445A1, with the patent name "Electroluminescence Detection Device and Electroluminescence Detection Method for Solar Panels", and Publication No. WO2017172611A1, with the patent name "Automatic Identification and Defect Detection System and Method for Solar Panels Using Infrared Imaging", also do not involve imaging detection in daylight environment.

[0005] Therefore, the present invention proposes a photovoltaic panel invisible defect detection device based on multispectral imaging. By means of the method of multi-channel narrow-band spectral imaging, the interference of daylight on photoluminescence or electroluminescence imaging is eliminated or suppressed, so as to realize high-quality on-line detection of invisible defects of photovoltaic panels. Summary of the Invention

[0006] Aiming at the shortcomings and deficiencies of the prior art, the present invention aims to provide a photovoltaic panel invisible defect detection device based on multispectral imaging, which overcomes the adverse effects of daylight environment on photoluminescence imaging or electroluminescence imaging of photovoltaic panels, thereby improving the imaging level of invisible defects of photovoltaic panels.

[0007] The specific technical solution of the present invention is as follows:

[0008] The present invention provides a photovoltaic panel invisible defect detection device based on multispectral imaging, including a photovoltaic panel to be measured, which adopts a crystalline silicon photovoltaic panel;

[0009] An excitation module, configured to generate a short-wave infrared band in the photovoltaic panel to be measured under the irradiation of an excitation light source; the excitation light source includes a near-infrared photoexcitation light source and / or an electroluminescence drive power supply;

[0010] A spectral acquisition module, including a multispectral imaging system composed of a variable filter and a area array camera. The variable filter adopts a narrow-band filtering component with programmable wavelength, and its transmission wavelength covers the characteristic spectral band from 1050nm to 1250nm;

[0011] An image acquisition and processing system, configured to control the spectral channel switching of the variable filter, and perform acquisition of multispectral images and fusion processing.

[0012] In a further technical solution, the excitation light source is an infrared light-induced excitation light source that irradiates the photovoltaic panel to be measured; the near-infrared light-induced excitation light source is generated by a laser, the laser includes an LED array or a semiconductor laser, and the laser is a narrow-band light source with a central wavelength of 800-860 nm.

[0013] In a further technical solution, the excitation light source is an electroluminescence driving power supply electrically connected to the photovoltaic panel to be measured; the electroluminescence driving power supply applies a reverse bias voltage to the PN junction of the photovoltaic panel to be measured and generates an electroluminescence phenomenon. Preferably, the reverse voltage range applied by the electroluminescence driving power supply is -5V to -20V, and the voltage value is dynamically adjusted according to the series resistance of the photovoltaic module.

[0014] In a further technical solution, the variable filter is a rotary filter wheel structure provided between the photovoltaic panel to be measured and the area array camera, and is equipped with at least 4 narrow-band filters; the central wavelengths of the narrow-band filters cover the range of 1050-1250 nm.

[0015] In a further technical solution, the variable filter is a liquid crystal tunable filter provided between the photovoltaic panel to be measured and the area array camera, and its transmittance in the 1050-1250 nm band is ≥35%.

[0016] In a further technical solution, the area array camera uses an InGaAs focal plane detection camera, and the spectral response range covers 400-1700 nm.

[0017] In a further technical solution, the image acquisition and processing system includes

[0018] a spectral channel switching unit configured to control the spectral channel switching of the variable filter;

[0019] an image acquisition unit configured to control the area array camera to sequentially capture multi-spectral images;

[0020] an image registration unit configured to process the captured images based on a sub-pixel registration algorithm for feature point matching;

[0021] an image fusion unit configured to perform three-level wavelet decomposition fusion processing, where the low-frequency sub-band adopts a weighted average fusion rule, and the weight coefficient is positively correlated with the signal-to-noise ratio of each spectral channel; the high-frequency sub-band adopts a regional energy maximization selection rule;

[0022] a defect enhancement unit configured to process the fused images using an image enhancement algorithm that combines adaptive histogram equalization and morphological operations.

[0023] Based on the above invention principle, the beneficial effects of the present invention are as follows:

[0024] The invisible defect detection device for photovoltaic panels based on multispectral imaging of the present invention uses a multi-channel narrowband spectral imaging method to eliminate or suppress the interference of sunlight on photoluminescence or electroluminescence imaging, thereby realizing high-quality online detection of invisible defects in photovoltaic panels.

[0025] The invisible defect detection device for photovoltaic panels based on multispectral imaging of the present invention ensures the flexibility of device use and the accuracy of detection through the collaborative innovation of a dual-mode excitation system and multispectral imaging, as well as the adaptive design of a specific spectral range (1050 - 1250 nm) and material characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the composition principle of an invisible defect detection device for photovoltaic panels based on multispectral imaging;

[0027] Figure 2 It is a schematic diagram of the principle of an invisible defect detection device for photovoltaic panels provided by an embodiment of the present invention, which uses an 850 nm laser excitation light source and a rotating wheel type multispectral filter;

[0028] Figure 3 It is a schematic diagram of the principle of an invisible defect detection device for photovoltaic panels provided by an embodiment of the present invention, which is based on electroluminescence and an LCTF component (liquid crystal tunable filter);

[0029] Figure 4 It is a schematic diagram of the spectral sensitivity curve of a wide spectral band InGaAs camera provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] An invisible defect detection device for photovoltaic panels based on multispectral imaging of the present invention includes a photovoltaic panel 1 to be measured using a crystalline silicon photovoltaic panel, an excitation module 2, a spectral acquisition module, and an image acquisition and processing system 5.

[0031] Figure 1 As shown, the excitation module 2 is configured to generate a short-wave infrared band in the photovoltaic panel 1 to be measured under the irradiation of an excitation light source; the excitation light source includes a near-infrared photoexcitation light source and / or an electroluminescence driving power supply. The spectral acquisition module includes a multispectral imaging system composed of a variable filter 3 and an area array camera 4. The variable filter 3 uses a narrowband filtering component with programmable wavelengths, and its transmission wavelength covers the characteristic spectral range from 1050 nm to 1250 nm. The image acquisition and processing system 5 is composed of a microcomputer and its peripheral interfaces, and is configured to control the spectral channel switching of the variable filter 3, and at the same time control the area array camera 4 to sequentially capture multispectral images, and process the captured multiple spectral images to improve the clarity of the images.

[0032] The content of the present invention will be further described below through embodiments, but it should not be construed as a limitation to the present invention. Without departing from the spirit and essence of the present invention, modifications or substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0033] Embodiment 1

[0034] Figure 2 As shown, this embodiment provides a photovoltaic panel invisible defect detection device using an 850nm laser light source and a rotating multi-spectral filter, including: a photovoltaic panel 1 to be tested, a near-infrared photo-excitation light source, a beam expander 6, a variable filter, an InGaAs camera 40, a microcomputer 50 and its peripheral interface USB, etc.

[0035] The photovoltaic panel 1 to be tested uses a crystalline silicon photovoltaic panel; it includes a polycrystalline silicon photovoltaic panel or a monocrystalline silicon photovoltaic panel.

[0036] The near-infrared photo-excitation light source is generated by a laser 20. The laser 20 includes an LED array or a semiconductor laser. The laser 20 is a narrow-band light source with a central wavelength of 800 - 860nm, and its output power density is not less than 50mW / cm 2 , and the adjustable range of the excitation duration is 10ms - 5s. In a specific solution, the laser 20 is an 850nm semiconductor laser. The beam emitted by it forms a planar light spot after passing through the beam expander and is projected onto the surface of the photovoltaic panel, inducing the photovoltaic panel to generate photoluminescence. The spectral energy of this fluorescence is mainly concentrated in the interval of 1050nm to 1250nm. Against the background of this fluorescence, the defect details inside and on the surface of the photovoltaic panel are revealed.

[0037] The variable filter is a rotating filter wheel structure 30 provided between the photovoltaic panel to be tested and the area array camera, equipped with at least 4 narrow-band filter wheels; the central wavelengths of the narrow-band filter films are respectively located in the visible light band and the short-wave infrared band, specifically covering the interval of 1050 - 1250nm. And the filter films are sequentially switched under the control of the microcomputer.

[0038] The area array camera uses an InGaAs camera 40. The InGaAs camera 40 is a wide-spectrum area array camera, and its spectral range covers the spectral range of 400nm to 1700nm, as Figure 4 shown; its quantum efficiency is not less than 60% in the 1050 - 1300nm band, and the spatial resolution reaches more than 640×512 pixels. The InGaAs camera 40 sequentially completes the shooting of the photovoltaic panel defect images in 4 bands under the control of the computer; the computer stores and displays the captured spectral images.

[0039] Embodiment 2

[0040] As Figure 3 shown, the present invention provides a photovoltaic panel invisible defect detection device based on electroluminescence and a liquid crystal tunable filter (LCTF), comprising: a photovoltaic panel 1 to be measured, an electroluminescence driving power supply 21, a variable filter, a wide-spectrum InGaAs camera 40, a microcomputer 50 and its peripheral interface USB, etc.

[0041] The excitation light source is the electroluminescence driving power supply 21 electrically connected to the photovoltaic panel to be measured; the electroluminescence driving power supply 21 applies a reverse bias voltage to the PN junction of the photovoltaic panel 1 to be measured and generates an electroluminescence phenomenon. The reverse voltage applied by the electroluminescence driving power supply 21 ranges from -5V to -20V, and the voltage value is dynamically adjusted according to the series resistance of the photovoltaic module. The spectral energy of the electroluminescence is mainly concentrated in the range of 1050nm to 1250nm; against the background of the electroluminescence, the defect images inside and on the surface of the photovoltaic panel are revealed.

[0042] The variable filter is a liquid crystal tunable filter 31, i.e., an LCTF component, provided between the photovoltaic panel to be measured and the area array camera. Its spectral tuning resolution ≤ 10nm, wavelength switching time ≤ 50ms, and transmittance ≥ 35% in the 1050 - 1250nm band. The LCTF component is a narrow-band filter with continuously variable wavelength, and its wavelength range covers the visible light to short-wave infrared band. When using the LCTF, sub-nanometer spectral scanning can be achieved through software programming, which is particularly suitable for analyzing the subtle spectral shift phenomenon caused by defects. With the cooperation of a thermoelectric cooling module and a transmittance compensation algorithm, a wavelength stability of ±1nm can be maintained at an ambient temperature of -10°C to 40°C. The LCTF component is located in front of the lens of the area array camera and continuously switches the central wavelength under the control of the computer.

[0043] The area array camera 40 uses a wide-spectrum InGaAs camera with a spectral range covering 400nm to 1700nm, which can not only capture the photoluminescence and electroluminescence images of the photovoltaic panel, but also capture the reflected light image of the photovoltaic panel. The wide-spectrum InGaAs camera 40 continuously captures the electroluminescence spectrum images of the photovoltaic panel or the reflected image of the photovoltaic panel on the ambient light through the LCTF component under the control of the computer, thereby obtaining a series of multi-spectral images of the photovoltaic panel defects.

[0044] In addition, in another specific example, the image acquisition and processing system 5 includes a spectral channel switching unit, an image acquisition unit, an image registration unit, an image fusion unit, and a defect enhancement unit.

[0045] The spectral channel switching unit is configured to control the spectral channel switching of the variable filter; specifically, the FPGA can generate a timing control signal to coordinate the excitation pulse of the excitation module, the switching action of the variable filter, and the exposure timing of the area array camera.

[0046] The image acquisition unit is configured to control the area array camera to sequentially capture multi-spectral images.

[0047] The image registration unit is configured to process the captured images based on the sub-pixel registration algorithm of feature point matching; the improved SIFT feature matching algorithm can be used to establish a sub-pixel level mapping relationship between adjacent spectral channel images, and the registration accuracy reaches 0.1 pixel.

[0048] The image fusion unit is configured to perform three-level wavelet decomposition fusion processing, in which the low-frequency sub-band adopts the weighted average fusion rule, and the weight coefficient is positively correlated with the signal-to-noise ratio of each spectral channel; the high-frequency sub-band adopts the regional energy maximization selection rule.

[0049] The defect enhancement unit is configured to process the fused image by applying an image enhancement algorithm that combines adaptive histogram equalization and morphological operations.

[0050] The above system deeply combines hardware timing control (FPGA) with software algorithms (wavelet fusion) to solve the synchronization problem of multi-spectral imaging.

[0051] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other, and the differences between each embodiment and other embodiments are emphasized. In particular, for the device embodiments, since they are basically similar to the method embodiments, they are described relatively simply, and the relevant parts can be referred to the description of the method embodiments.

[0052] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A photovoltaic panel invisible defect detection device based on multispectral imaging, characterized in that, Including: The photovoltaic panel to be tested, using a crystalline silicon photovoltaic panel; An excitation module configured to generate a short-wave infrared band in the photovoltaic panel to be tested under the irradiation of an excitation light source; the excitation light source includes a near-infrared photoexcitation light source and / or an electroluminescence drive power supply; A spectral acquisition module, including a multi-spectral imaging system composed of a variable filter and a planar array camera, the variable filter using a narrow-band filtering component with programmable wavelength, and its transmission wavelength covering the characteristic spectral band from 1050nm to 1250nm; An image acquisition and processing system configured to control the spectral channel switching of the variable filter, and at the same time control the planar array camera to sequentially capture multi-spectral images and process the captured multi-spectral images.

2. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 1, characterized in that, The photovoltaic panel to be tested uses a polycrystalline silicon photovoltaic panel or a single-crystalline silicon photovoltaic panel.

3. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 1, characterized in that The excitation light source is an infrared photoexcitation light source irradiating the photovoltaic panel to be tested; the near-infrared photoexcitation light source is generated by a laser, the laser includes an LED array or a semiconductor laser, and the laser is a narrow-band light source with a central wavelength of 800 - 860nm.

4. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 3, characterized in that, A beam expander is arranged in front of the laser.

5. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 1, characterized in that, The excitation light source is an electroluminescence drive power supply electrically connected to the photovoltaic panel to be tested; the electroluminescence drive power supply applies a reverse bias voltage to the PN junction of the photovoltaic panel to be tested and generates an electroluminescence phenomenon.

6. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 5, characterized in that, The reverse voltage applied by the electroluminescence drive power supply ranges from -5V to -20V, and the voltage value is dynamically adjusted according to the series resistance of the photovoltaic module.

7. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 1, characterized in that The variable filter is a rotary filter wheel structure arranged between the photovoltaic panel to be tested and the planar array camera, equipped with at least 4 narrow-band filter films; the central wavelength of the narrow-band filter films covers the interval of 1050 - 1250nm.

8. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 1, characterized in that, The variable filter is a liquid crystal tunable filter arranged between the photovoltaic panel to be tested and the planar array camera, and its transmittance in the 1050 - 1250nm band is ≥ 35%.

9. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 1, characterized in that, The planar array camera uses an InGaAs focal plane detection camera, and the spectral response range covers 400 - 1700nm.

10. The photovoltaic panel invisible defect detection device based on multispectral imaging according to claim 1, characterized in that, The image acquisition and processing system includes A spectral channel switching unit configured to control the spectral channel switching of the variable filter; An image acquisition unit configured to control the planar array camera to sequentially capture multi-spectral images; An image registration unit configured to process the captured images based on a sub-pixel registration algorithm for feature point matching; An image fusion unit configured to perform three-level wavelet decomposition fusion processing, where the low-frequency sub-band uses a weighted average fusion rule, and the weight coefficient is positively correlated with the signal-to-noise ratio of each spectral channel; the high-frequency sub-band uses a region energy maximization selection rule; A defect enhancement unit configured to process the fused image using an image enhancement algorithm combining adaptive histogram equalization and morphological operations.

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