A nondestructive testing system and equipment for photovoltaic cells

Abstract

The present invention discloses a nondestructive testing system and equipment for photovoltaic cells, and relates to the field of nondestructive testing. It includes a non-contact electromagnetic induction device, which is used to generate an external electric field acting on the photovoltaic cell under test without contacting the photovoltaic cell under test, and the external electric field is parallel to the internal electric field direction of the photovoltaic cell under test; a short-wave infrared camera and / or a visible light camera, which is used to obtain the light radiation distribution map in the photovoltaic cell under test; a thermal imaging device, which is used to obtain the thermal radiation distribution map in the photovoltaic cell under test; and an image processing device, which is used to store and process the light radiation distribution map and the thermal radiation distribution map. The present invention is a non-contact detection when testing photovoltaic cells, and will not damage the photovoltaic cells under test; it can avoid the influence of lateral heat diffusion on defect detection, and improve detection accuracy and detection efficiency.

Description

Technical Field

[0001] The invention relates to the field of nondestructive testing, in particular to a nondestructive testing system and equipment for photovoltaic cells. Background Art

[0002] Photovoltaic power generation has become the key to my country's energy transformation. In recent years, shutdowns, production cuts and safety accidents caused by quality problems of photovoltaic cells are common.

[0003] In order to evaluate the quality of photovoltaic cells, there are currently dozens of detection technologies used for photovoltaic cells. Among them, the electrical parameter measurement method is faster, but cannot detect the specific location of defects; electroluminescence (EL) can quickly detect defects and is sensitive to surface defects; electro-thermography (ET) is sensitive to thermal phenomena generated by photovoltaic cells due to faults such as leakage current, and can be used to detect internal breakdown defects.

[0004] However, in electroluminescence and electrothermal imaging, the electrodes of the power supply need to be in contact with the photovoltaic cell, which not only affects the detection speed, but may also scratch the photovoltaic cell. In addition, electroluminescence and electrothermal imaging are performed under static conditions (imaging equipment and photovoltaic cells are stationary), without dynamic imaging, and the efficiency is low; electrothermal imaging is difficult to achieve quantitative evaluation of defects due to lateral heat diffusion, and it is difficult to calibrate defects, so the defect detection accuracy is low. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a non-destructive testing system and equipment for photovoltaic cells in view of the deficiencies in the prior art, which can detect damage on the surface or inside of the photovoltaic cell without contacting the photovoltaic cell.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a system for non-destructive testing of photovoltaic cells, comprising:

[0007] A non-contact electromagnetic induction device, used for generating an external electric field acting on the photovoltaic cell under inspection without contacting the photovoltaic cell under inspection, wherein the external electric field is parallel to the internal electric field direction of the photovoltaic cell under inspection;

[0008] A short-wave infrared camera and / or a visible light camera, used to obtain a light radiation distribution map in the inspected photovoltaic cell;

[0009] A thermal imaging device for obtaining a distribution map of thermal radiation within the inspected photovoltaic cell;

[0010] An image processing device is used to store and process the light radiation distribution map and the heat radiation distribution map.

[0011] In a photovoltaic cell, the electron concentration in the N region is high and the hole concentration in the P region is high, so the electrons will diffuse from the N region to the P region. Similarly, the holes will diffuse from the P region to the N region. At this time, the nuclei left in the N region are positively charged, and on the contrary, the nuclei left in the P region are negatively charged. Thus, an internal electric field is formed from the N region to the P region. The non-contact electromagnetic induction device is used to generate an external electric field acting on the photovoltaic cell under test without contacting the photovoltaic cell under test. The external electric field is parallel to the internal electric field of the photovoltaic cell under test. If the external electric field is in the opposite direction to the internal electric field, the total electric field in the photovoltaic cell is weakened and the diffusion motion of the minority carriers is enhanced. If the external electric field is in the same direction as the internal electric field, the total electric field in the photovoltaic cell is enhanced and the drift motion of the minority carriers is enhanced. Therefore, whether forward bias or reverse bias is applied, the equilibrium state inside the photovoltaic cell will be broken, and the non-equilibrium minority carriers will continuously recombine when encountering the majority carriers in the original area, thereby generating light radiation. At a constant temperature, the intensity of light radiation is proportional to the concentration of minority carriers and the minority carrier diffusion length. At the same time, when there is an external electric field inside the GF battery, the excess minority carrier concentration at the edge of the PN junction also increases, and the battery luminescence intensity increases accordingly. Since the defect has a lower minority carrier diffusion length, it emits weaker light, thus forming a darker image. At the same time, the external electric field generates thermal radiation inside the photovoltaic cell due to the Joule effect. When there are defects on the surface or inside the photovoltaic cell under inspection, the defects will cause disturbances to the optical flow field and thermal flow field, resulting in abnormal light and heat distribution. By obtaining the optical radiation distribution map and thermal radiation distribution map of the photovoltaic cell under inspection, the defects can be detected. The minority carrier diffusion length, that is, the minority carrier diffusion length, characterizes the average distance that minority carriers can travel while diffusing and recombination.

[0012] Specifically, the non-contact electromagnetic induction device includes two induction coils, which are respectively arranged on both sides of the photovoltaic cell to be inspected, and the coils of the two induction coils are parallel to the internal electric field direction of the photovoltaic cell to be inspected. By controlling the two induction coils, an external electric field parallel to the internal electric field of the photovoltaic cell to be inspected can be generated.

[0013] Specifically, the currents in the two induction coils are of the same magnitude and in the same direction. Thus, when the photovoltaic cell under test is placed in the external electric field generated by the two induction coils, the total electric field in the photovoltaic cell under test will be relatively uniform, thus minimizing the impact of lateral heat diffusion on the detection effect.

[0014] Specifically, the magnitude and direction of the induced current in the two induction coils can be adjusted. By adjusting the magnitude of the induced current in the induction coils, the magnetic field strength generated by the induction coils can be adjusted, thereby affecting the external electric field strength generated by the induction coils from the P region to the N region in the photovoltaic cell under inspection.

[0015] Specifically, it also includes an image display device, which is electrically connected to the image processing device to display the image stored and processed by the image processing device. Through the image display device, the user can intuitively see the results of the non-destructive testing.

[0016] Specifically, it also includes a movable guide rail, and the non-contact electromagnetic induction device, the short-wave infrared camera and / or the visible light camera, and the thermal imaging device are all installed on the movable guide rail. During the movement of the movable guide rail, the relative positions of the non-contact electromagnetic induction device, the short-wave infrared camera and / or the visible light camera, and the thermal imaging device remain unchanged.

[0017] Based on the same technical concept, the present invention also provides a non-destructive testing device for photovoltaic cells, including the non-destructive testing system for photovoltaic cells.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1) In the process of testing the photovoltaic cell under test, the non-contact electromagnetic induction device, the thermal imaging device, the short-wave infrared camera and / or the visible light camera, the image processing device and the image display device do not need to contact the photovoltaic cell under test, which is a non-contact test and will not damage the photovoltaic cell under test;

[0020] 2) The external electric field generated by the non-contact electromagnetic induction device can avoid the influence of lateral heat diffusion on defect detection and improve detection accuracy and efficiency;

[0021] 3) The movable guide rail is movable, thus supporting dynamic imaging and mobile detection, and can obtain dynamic light radiation distribution maps and thermal radiation distribution maps. The image can be processed in combination with deep learning methods to further improve detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The figure is a schematic diagram of the structure of a nondestructive testing device for photovoltaic cells according to an embodiment of the present invention.

[0023] Figure 2 FIG. 1 is a schematic diagram of the positional relationship between the induction coil and the photovoltaic cell according to an embodiment of the present invention.

[0024] Among them, 1 is a control device, 2 is a computer device, 3 is an excitation device, 4 is a short-wave infrared camera, 5 is a thermal imager, 6 is an induction coil, 7 is a photovoltaic cell to be inspected, and 701 is a defect in the photovoltaic cell. DETAILED DESCRIPTION

[0025] like Figure 1As shown, in one embodiment of the present invention, the nondestructive testing equipment for photovoltaic cells includes a nondestructive testing system for photovoltaic cells and an excitation device 3 and a control device 1 thereof, wherein the nondestructive testing system for photovoltaic cells includes a non-contact electromagnetic induction device, a short-wave infrared camera 4, a thermal imaging device, an image processing device, an image display device, and a movable guide rail.

[0026] In one embodiment of the present invention, the non-contact electromagnetic induction device is a Helmholtz coil, which includes two circular induction coils 6 that are parallel and coaxial to each other, and the currents in the two induction coils 6 are the same in magnitude and direction. The thermal imaging device includes a thermal imager 5, and the image processing device and the image display device are integrated in the computer device 2.

[0027] The excitation device 3 is electrically connected to the two induction coils 6 to provide the two induction coils 6 with an adjustable working current. Figure 2 As shown, the two induction coils 6 are respectively arranged on both sides of the photovoltaic cell 7 to be inspected, and the coils of the two induction coils 6 are parallel to the internal electric field direction of the photovoltaic cell 7 to be inspected.

[0028] The computer device 2, the excitation device 3, the short-wave infrared camera 4 and the thermal imager 5 are all electrically connected to the control device 1, and the control device 1 is used to control the working status of the computer device 2, the excitation device 3, the short-wave infrared camera 4 and the thermal imager 5.

[0029] The short-wave infrared camera 4 and the thermal imager 5 are both placed directly above the photovoltaic cell 7 under inspection. The short-wave infrared camera 4 can obtain the light radiation distribution map of the photovoltaic cell 7 under inspection, and the thermal imager 5 can obtain the thermal radiation distribution map of the photovoltaic cell 7 under inspection.

[0030] The short-wave infrared camera 4 and the thermal imager 5 are both electrically connected to the computer device 2 to process and display the images acquired by the short-wave infrared camera 4 and the thermal imager 5 .

[0031] The movable rail is not shown in the figure, and the two induction coils 6, the short-wave infrared camera 4 and the thermal imager 5 are all mounted on the movable rail. During the movement of the movable rail, the relative positions of the two induction coils 6, the short-wave infrared camera 4 and the thermal imager 5 remain unchanged.

[0032] In one embodiment of the present invention, the nondestructive testing device for photovoltaic cells can realize static testing and dynamic testing. Static testing means that the photovoltaic cell under test and the movable guide rail remain stationary. There are two ways to realize dynamic testing, one is that the photovoltaic cell under test moves while the movable guide rail does not move, and the other is that the photovoltaic cell under test does not move while the movable guide rail moves.

[0033] like Figure 2 As shown, during the detection, the photovoltaic cell 7 to be detected is placed between the two induction coils 6, and the coils of the two induction coils 6 are parallel to the direction of the internal electric field of the photovoltaic cell 7 to be detected. The computer device 2, the excitation device 3, the short-wave infrared camera 4 and the thermal imager 5 are started by the control device 1. At this time, a magnetic field is generated in the two induction coils 6 due to the passage of current, and a magnetic field is also generated between the two induction coils 6. In the area where the photovoltaic cell 7 to be detected is located, an external electric field parallel to the direction of the internal electric field of the photovoltaic cell 7 to be detected is generated. Figure 2 The middle arrow indicates the direction of the external electric field. At this time, light radiation and thermal radiation are generated inside the photovoltaic cell 7 under inspection. The existence of the defect 701 inside the photovoltaic cell 7 under inspection will disturb the light flow field and the thermal flow field, resulting in abnormal light and heat distribution at the defect 701. The distribution map of light radiation obtained by the short-wave infrared camera 4 and the distribution map of thermal radiation obtained by the thermal imager 5 can be processed and displayed by the computer equipment to intuitively determine whether the photovoltaic cell 7 under inspection has defects, as well as the size and type of the defects.

[0034] By adjusting the excitation device 3, the working current of the two induction coils 6 can be adjusted to adjust the strength of the external electric field generated by them.

[0035] In one embodiment of the present invention, the nondestructive testing equipment for photovoltaic cells can combine the three-dimensional data reconstruction method with the deep learning method to process dynamic images, thereby improving the ability to identify defects during dynamic testing.

Claims

1. A nondestructive testing system for photovoltaic cells, characterized in that: include A non-contact electromagnetic induction device, used for generating an external electric field acting on the photovoltaic cell under inspection without contacting the photovoltaic cell under inspection, wherein the external electric field is parallel to the internal electric field direction of the photovoltaic cell under inspection; A short-wave infrared camera and / or a visible light camera, used to obtain a light radiation distribution map in the inspected photovoltaic cell; A thermal imaging device for obtaining a distribution map of thermal radiation within the inspected photovoltaic cell; An image processing device is used to store and process the light radiation distribution map and the heat radiation distribution map.

2. The nondestructive testing system for photovoltaic cells according to claim 1, characterized in that: The non-contact electromagnetic induction device comprises two induction coils, which are respectively arranged on both sides of the photovoltaic cell to be inspected, and the coils of the two induction coils are parallel to the internal electric field direction of the photovoltaic cell to be inspected.

3. The nondestructive testing system for photovoltaic cells according to claim 2, characterized in that: The currents in the two induction coils are of the same magnitude and in the same direction.

4. The nondestructive testing system for photovoltaic cells according to claim 3, characterized in that: The magnitude and direction of the induced current in the two induction coils can be adjusted.

5. The nondestructive testing system for photovoltaic cells according to claim 4, characterized in that: It also includes an image display device, which is electrically connected to the image processing device to display the image stored and processed by the image processing device.

6. The nondestructive testing system for photovoltaic cells according to any one of claims 1 to 5, characterized in that: It also includes a movable guide rail, on which the non-contact electromagnetic induction device, the short-wave infrared camera and / or the visible light camera, and the thermal imaging device are all installed. During the movement of the movable guide rail, the relative positions of the non-contact electromagnetic induction device, the short-wave infrared camera and / or the visible light camera, and the thermal imaging device remain unchanged.

7. A non-destructive testing device for photovoltaic cells, characterized in that: A nondestructive testing system for photovoltaic cells comprising any one of claims 1 to 6.

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