Solar panel inspection device and inspection method

Abstract

To provide a solar panel inspection device and an inspection method that is less affected by solar radiation conditions when using a photoluminescence (PL)-based PL inspection method.SOLUTION: Under sunlight irradiation, an open-state PL image is taken with a solar panel open, and a closed-state PL image is taken with the solar panel operating at the maximum power point under the control of a power conditioner, and a differential brightness value ΔPL is calculated from the difference image between the open-state PL image and the closed-state PL image. The differential brightness value ΔPL is divided by the open-circuit voltage value Voc and the short-circuit current specification value Isc to obtain a pseudo FF value (ΔPL / (Voc×Isc)), and the power generation performance of the solar panel is evaluated on the basis of this pseudo FF value.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an inspection apparatus and an inspection method for a solar cell panel.

Background Art

[0002] The presence or absence of defects in a solar cell panel can be grasped by inspection during manufacturing or shipment. However, solar cell panels that have already been installed and used as a solar power generation system may have different power generation performances due to deterioration, damage, disconnection of internal circuits, short-circuit of bypass circuits, etc., depending on their usage conditions. And, with the spread and expansion of solar power generation systems, there is an increasing need to efficiently grasp the power generation performance of solar cell panels during maintenance inspections and reuse of solar cell panels.

[0003] For example, when reusing a solar cell module, it is necessary to grasp the structure and electrical power generation performance status of the solar cell module and determine the feasibility of reuse from the results. However, it requires a lot of labor and cost to remove the installed solar cell module, transport it to a building, etc., and then determine the feasibility of reuse. For this reason, for example, Patent Document 1 proposes a PL inspection method using photoluminescence (hereinafter also referred to as "PL"), which is one of the methods for inspecting the presence or absence of defects in a solar cell under sunlight irradiation on a solar cell module installed outdoors.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inspection method of the solar cell panel disclosed in Patent Document 1 can inspect the presence or absence of defects in the solar cell. However, even if there is a solar cell module with a defect in the I-V characteristics in the solar cell modules in the string to be inspected, for example, a solar cell module with a low open-circuit voltage value Voc as the I-V characteristic, it can only be evaluated by the difference in the luminance values of the pixels in the open-state PL image and the closed-state PL image (difference luminance value ΔPL). Further, when performing a comparative evaluation with solar cell modules in other solar cell strings, the conditions at the time of PL camera shooting, such as differences in solar irradiance, may be different for each, and an accurate comparative evaluation cannot be performed only with the difference luminance value ΔPL.

[0006] The present invention has been made in view of these circumstances, and when using a PL inspection method using photoluminescence (PL), which is one of the methods for inspecting the presence or absence of defects in solar cells in a photovoltaic power generation system, an object thereof is to provide an inspection apparatus and an inspection method for a solar cell panel that are less affected by solar irradiance conditions.

Means for Solving the Problems

[0007] In order to solve the above problems, a first technical means of the present invention is an inspection device for a solar cell panel connected via a switch to a power conditioner that performs maximum power point tracking control (MPPT), comprising: imaging means for imaging the solar cell panel; an open-state PL image captured by the imaging means with the switch open and the solar cell panel in an open state under sunlight irradiation; a closed-state PL image captured by the imaging means with the switch closed and the solar cell panel operating at the maximum power point (MPP) under the control of the power conditioner under sunlight irradiation; PL image generation means for generating the closed-state PL image; determination PL image generation means for generating a determination PL image consisting of a difference image between the open-state PL image and the closed-state PL image; ΔPL calculation means for calculating a differential luminance value ΔPL of the solar cell panel from the determination PL image; voltage measurement means for measuring an open-circuit voltage value Voc of the solar cell panel in a state where the switch is open and the solar cell panel is open under sunlight irradiation; and pseudo-FF value calculation means for calculating ΔPL / (Voc×Isc) as a pseudo-FF value from the short-circuit current specification value Isc of the solar cell panel, the open-circuit voltage value Voc, and the differential luminance value ΔPL.

[0008] A second technical means of the present invention is characterized in that, in the first technical means, the determination PL image is generated from a plurality of the captured open-state PL images and a plurality of the captured closed-state PL images.

[0009] A third technical means of the present invention is characterized in that, in the first or second technical means, it further comprises power generation performance determination means for determining the power generation performance of the solar cell panel based on the pseudo-FF value.

[0010] A fourth technical means of the present invention is characterized in that, in the third technical means, the power generation performance determination means determines the power generation performance by comparing the current pseudo-FF value of the solar cell panel to be inspected with the past pseudo-FF value of the solar cell panel to be inspected.

[0011] The fifth technical means of the present invention is as follows. In the third technical means, the power generation performance determination means determines the power generation performance by comparing the current pseudo-FF value of the solar cell panel to be inspected with the current pseudo-FF value of another solar cell panel having the same specifications as the solar cell panel to be inspected.

[0012] The sixth technical means of the present invention is an inspection method for a solar cell panel connected to a power conditioner that performs maximum power point tracking control (MPPT) via a switch. Under sunlight irradiation, an open-state PL image capturing step of capturing an open-state PL image of the solar cell panel in a state where the switch is open and released; an open-circuit voltage value measurement step of measuring the open-circuit voltage value Voc of the solar cell panel in a state where the switch is open and released under sunlight irradiation; a closed-state PL image capturing step of capturing a closed-state PL image of the solar cell panel in a state where the switch is closed and operating at the maximum power point (MPP) under the control of the power conditioner under sunlight irradiation; a determination PL image generation step of generating a determination PL image composed of a difference image between the open-state PL image and the closed-state PL image; a ΔPL calculation step of calculating a difference luminance value ΔPL of the solar cell panel from the determination PL image; and a pseudo-FF value calculation step of calculating ΔPL / (Voc×Isc) as a pseudo-FF value from the short-circuit current specification value Isc of the solar cell panel, the open-circuit voltage value Voc, and the difference luminance value ΔPL. The power generation performance of the solar cell panel is determined based on the pseudo-FF value.

[0013] The seventh technical means of the present invention is as follows. In the sixth technical means, the determination PL image is generated from a plurality of the captured open-state PL images and a plurality of the captured closed-state PL images.

[0014] The eighth technical means of the present invention is that in the sixth or seventh technical means, the determination of the power generation performance of the solar cell panel is characterized in that it is performed by comparing the current pseudo FF value in the solar cell panel to be inspected with the past pseudo FF value in the solar cell panel to be inspected.

[0015] The ninth technical means of the present invention is that in the sixth or seventh technical means, the determination of the power generation performance of the solar cell panel is characterized in that it is performed by comparing the current pseudo FF value in the solar cell panel to be inspected with the current pseudo FF value in another solar cell panel having the same specification as the solar cell panel to be inspected.

Effects of the Invention

[0016] According to the first and sixth technical means of the present invention, it is possible to inspect the power generation performance of the solar cell panel while the solar cell panel is installed and operating, and it is possible to obtain an inspection apparatus and an inspection method for the solar cell panel that are less affected by solar radiation conditions.

[0017] According to the second and seventh technical means of the present invention, since the determination PL image is generated from a plurality of open state PL images and a plurality of closed state PL images, it is possible to reduce the influence of the change in the amount of solar radiation at the time of shooting the open state PL image and at the time of shooting the closed state PL image.

[0018] According to the third technical means of the present invention, by setting the determination conditions in advance, it is possible to automatically determine the power generation performance of the solar cell panel.

[0019] According to the fourth and eighth technical means of the present invention, by comparing, for example, the pseudo FF value at the time of installation of the solar cell panel to be inspected, it is possible to accurately know the state of deterioration. Further, by performing regular inspections, it is possible to know the state of deterioration over time.

[0020] According to the fourth and eighth technical means of the present invention, in a solar power generation system, since solar cell modules of the same specification are usually used, even if the pseudo FF values at the time of installation or in the past are not stored, deteriorated solar cell modules can be identified.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0022] Hereinafter, with reference to the drawings, a preferred embodiment of the inspection device and inspection method for a solar cell panel according to the present invention will be described in the case where the inspection unit of the solar cell panel is a solar cell string. In the following description, components denoted by the same reference numerals in different drawings are assumed to be the same, and the description thereof may be omitted. Note that the present invention is not limited to the examples in these embodiments, and includes all modifications within the scope and equivalent scope of the matters described in the claims. Also, as long as combinations of multiple embodiments are possible, the present invention includes combinations of any embodiments.

[0023] FIG. 1 is a diagram for explaining a configuration of a photovoltaic power generation system, and is the object of the inspection apparatus and inspection method of the solar cell panel of the present invention. In order to obtain a desired power generation amount, solar cells of a photovoltaic power generation system usually connect a plurality of solar cell units to form a solar cell module 11 unit, and further, a plurality of solar cell modules 11 are combined in a plurality of units and connected in series to form a solar cell string 12 unit. Each solar cell module 11 has an internal circuit in which solar cell units are connected in series, and a bypass circuit in which bypass diodes are connected in parallel to this internal circuit.

[0024] A plurality of solar cell string 12 units are further connected to a junction box 20 to aggregate power, thereby forming a solar cell array 13 unit. Then, a plurality of solar cell arrays 13 are further connected to a power collection box 30 to aggregate power, and are connected to a power conditioner (PCS: Power Conditioning Subsystem) 40. In an example of the configuration shown in FIG. 1, an example is shown in which three solar cell strings 12 form one solar cell array 13, and three solar cell arrays 13 are connected to a power collection box 30. In the present invention, the term solar cell panel is used as a general term for a solar cell module 11 unit, a solar cell string 12 unit, a solar cell array 13 unit, or an aggregate of a plurality of solar cell arrays. Since the solar cell string 12 and the solar cell array 13 are installed over a large area, it is difficult to detect an abnormal or deteriorated solar cell string 12 or solar cell array 13.

[0025] The connection box 20 is a device for collecting the DC power generated by a plurality of solar cell strings 12 with one solar cell string 12 as one line. The connection box 20 has switches 21 provided for individual solar cell strings 12 and various circuit elements such as a backflow prevention element and a lightning protection element (not shown). Similarly, the power collection box 30 is a device for collecting the DC power generated by a plurality of solar cell arrays 13 with one solar cell array 13 as one line. The power collection box 30 has switches 31 provided for individual solar cell arrays 13 and various circuit elements such as a backflow prevention element and a lightning protection element (not shown), similar to the connection box 20.

[0026] The DC power aggregated by the power collection box 30 is output to the AC system by the PCS 40. The PCS 40 is a power converter for converting the DC power generated by the solar cells into AC power, and operates for power conversion when the solar cell panel is irradiated with light such as sunlight. The PCS 40 controls the power passing through the PCS 40 by switching (on / off) of semiconductor switches in order to convert DC power into AC power, and converts it into AC power so that the DC power output by the solar cell panel becomes maximum by the maximum power point tracking control (MPPT) described later. Note that a plurality of power collection boxes 30 may be connected to the PCS 40 to aggregate the power from the plurality of power collection boxes 30. In this case, switches are provided for the output from each power collection box 30.

[0027] FIG. 2 is a diagram showing a configuration example of an inspection device for a solar cell panel according to the present invention. In FIG. 2, the case where the solar cell string 12 is targeted as an inspection unit of the solar cell panel for which inspection is carried out is shown. The inspection device includes a camera 50 as imaging means for imaging the solar cell string 12, a voltmeter 60, and an inspection device main body 100 that generates an image necessary for determining the power generation performance by processing the image of the solar cell string 12 imaged by the camera 50 and calculates a pseudo-FF value.

[0028] The camera 50 is for photographing a solar cell panel and is not limited as long as it has sensitivity to the wavelength of the PL emission from the solar cells. When inspecting a solar cell string, it is preferable that the camera 50 is set at a position where it can photograph the entire solar cell string 12. However, the position of the camera 50 may be configured to be movable so that it can photograph a plurality of solar cell modules 11 included in the solar cell string 12 one by one or one by one. Further, when the inspection target extends over a large area such as a solar cell array 13, it may be mounted on an unmanned aerial vehicle (drone).

[0029] Further, it is desirable to provide an optical filter or a hood to the camera 50. For example, in the case of a silicon crystalline solar cell, since PL light which is near-infrared light having a peak at 1150 nm is generated, as the optical filter, it is desirable to use a band-pass filter which does not transmit visible light and transmits near-infrared light having a wavelength of 1150 nm. Further, by attaching a hood, noise such as irregular reflection light incident on the camera 50 can be significantly reduced.

[0030] The voltmeter 60 is for measuring the open-circuit voltage value Voc of the solar cell string 12. The switch 21 is provided in the junction box 20 for each solar cell string 12 and is connected so that the open-circuit voltage value Voc of the solar cell string 12 can be measured when the switch 21 is in the open state. The switch 21 is controlled by the switch control means 108 of the inspection apparatus main body 100 described later.

[0031] The inspection device main body 100 has a function of calculating a pseudo FF value and determining the power generation performance of a solar cell based on the pseudo FF value as needed. As hardware, the inspection device main body 100 includes a CPU 110 and a storage unit 120. The storage unit 120 is for storing various programs and data for operating the inspection device main body 100, as well as the short-circuit current specification value Isc, the pseudo FF values 121 calculated in the past and this time, and the like. The CPU 110 realizes various functions necessary for the inspection device main body 100 by operating the programs stored in the storage unit 120 as an arithmetic device. As examples of the functional units that perform these functions, FIG. 2 shows a PL image generation means 101, a PL image generation means 102 for determination, a ΔPL calculation means 103, a voltage measurement means 104, a pseudo FF value calculation means 105, a power generation performance determination means 106, a display / alarm means 107, and a switch control means 108.

[0032] Hereinafter, each functional unit will be described. The PL image generation means 101 controls the camera 50 to photograph the solar cell string 12 in a state where the switch 21 is open and a state where the switch 21 is closed, obtains an imaging image from the camera 50, and temporarily stores the photographed image in the storage unit 120. In this description, the image obtained by photographing the solar cell string 12 with the switch 21 open is referred to as an "open state PL image", and the image obtained by photographing the solar cell string 12 with the switch 21 closed is referred to as a "closed state PL image".

[0033] The determination PL image generation means 102 generates a determination PL image composed of the difference image of the luminance values of each pixel of the open-state PL image and the closed-state PL image temporarily stored in the storage unit 120. When there are a plurality of open-state PL images and closed-state PL images respectively, an open-state average PL image composed of the average value of the luminance values of each pixel of the plurality of open-state PL images and a closed-state average PL image composed of the average value of the luminance values of each pixel of the plurality of closed-state PL images are generated, and a determination PL image composed of the difference image of the luminance values of each pixel between the open-state average PL image and the closed-state average PL image is generated. When obtaining the average or difference of the luminance values of each pixel, by performing image recognition processing, the average or difference operation of the pixels at the same shooting position in the plurality of captured images is performed.

[0034] The ΔPL calculation means 103 specifies the positions of the solar cells in the solar cell string 12 from the determination PL image generated by the determination PL image generation means 102, and counts the luminance values of the pixels corresponding to the solar cells, thereby calculating the differential luminance value ΔPL. The calculated differential luminance value ΔPL is temporarily stored in the storage unit 120.

[0035] The voltage measurement means 104 is for measuring the open-circuit voltage value Voc of the solar cell string 12 by the voltmeter 60 when the switch 21 is in the open state, and the measured open-circuit voltage value Voc is temporarily stored in the storage unit 120.

[0036] The pseudo-FF value calculation means 105 calculates a pseudo-FF value described later from the differential luminance value ΔPL, the open-circuit voltage value Voc, and the short-circuit current specification value Isc stored in the storage unit 120, and stores the calculated pseudo-FF value of each solar cell string 12 in the storage unit 120 as the pseudo-FF value 121. Further, the calculated pseudo-FF value is transmitted to the display / alarm means 107 and displayed on a display panel or the like. The maintenance inspector can determine which solar cell string 12 is deteriorated by looking at the pseudo-FF value of each solar cell string 12 displayed on the display panel or the like.

[0037] The power generation performance determination means 106 automatically performs the performance evaluation of the solar cell string 12 to be inspected, and does so by either or both of the following two methods. The first method is to compare the current pseudo-FF value in the solar cell string 12 to be inspected with the past pseudo-FF value. As the past pseudo-FF value, it is desirable to obtain it as an initial performance confirmation at the time of installation of the solar cell string 12 and store it in the storage unit 120 as the initial pseudo-FF value. The second method is to compare the current pseudo-FF value in the solar cell string 12 to be inspected with the current pseudo-FF value in another solar cell string 12 having the same specifications as the solar cell string 12 to be inspected. In the case of existing solar cell panels, there may be no data on the initial pseudo-FF value, and in that case, the second method can be used.

[0038] In both the first method and the second method, when the pseudo-FF value obtained in the current inspection is equal to or less than a predetermined ratio with respect to the pseudo-FF value to be compared, or when it is equal to or less than a predetermined magnitude, the power generation performance determination means 106 determines that the solar cell string 12 to be inspected is deteriorated. The determination result is transmitted to the display / warning means 107.

[0039] The display / warning means 107 displays the pseudo-FF value for each solar cell string 12 sent from the pseudo-FF value calculation means 105 and the performance determination result for each solar cell string 12 sent from the power generation performance determination means 106. Further, when the performance determination result of the solar cell string 12 sent from the power generation performance determination means 106 is evaluated as being deteriorated, the display / warning means 107 issues a warning to the maintenance inspector as necessary.

[0040] The switch control means 108 controls the opening and closing operations of the switches 21 for each solar cell string 12 provided in the junction box 20 or the switches 31 for each solar cell array 13 provided in the power collection box 30. The switch control means 108 cooperates with the PL image generation means 101 to open and close the switch 21 so that the PL image generation means 101 can obtain an open-state PL image and a closed-state PL image, and cooperates with the voltage measurement means 104 to open and close the switch 21 so that the voltage measurement means 104 can measure the open-circuit voltage value Voc of the solar cell string 12.

[0041] Next, the pseudo FF value of the present invention will be described. FIG. 3 is a diagram for explaining the relationship between the I-V characteristics of a solar cell and the pseudo FF value of the present invention.

[0042] A solar cell is formed by joining an n-type semiconductor in which electrons are the main carriers and a p-type semiconductor in which holes are the main carriers. A depletion layer where neither electrons nor holes exist is formed at the junction surface, and a diffusion potential difference is generated by the p-type side of this depletion layer being negatively charged and the n-type side being positively charged. When light having energy equal to or greater than the forbidden bandwidth is irradiated onto the depletion layer, an excessive number of electron-hole pairs are generated, and the generated electron-hole pairs are separated by the diffusion potential difference, resulting in the n-type side being negatively charged and the p-type side being positively charged. As a result, a voltage appears across both ends. Then, an electric current is taken out to the outside through the electrodes provided on each of the n-type semiconductor and the p-type semiconductor. On the other hand, when the generated electron-hole pairs recombine, light is generated, and the generated light is photoluminescence (PL).

[0043] In a normal solar cell string 12, when the switch 21 is in the open state, carriers in the solar cell are not extracted as current to the outside, so the carrier density increases, and the PL emission due to the recombination of electron-hole pairs also becomes stronger. Also, when the switch 21 is in the closed state, the carrier density in the solar cell decreases due to energization, so the PL emission becomes weaker or no PL emission occurs. On the other hand, in a defective solar cell string 12 such as an open circuit in the internal circuit or a short circuit such as soldering of the bypass circuit, the PL emission is at the same level regardless of whether the switch 21 is in the open or closed state.

[0044] In this embodiment, the differential luminance value ΔPL, which is the difference in luminance of the PL emission from the solar cell string 12 between the open state and the closed state of the switch 21, is used. However, in the solar cell module 11 within the solar cell string 12, for example, there may be a solar cell module 11 with a low open-circuit voltage value Voc as an I-V characteristic, or the conditions during camera shooting such as differences in solar irradiance may vary. Therefore, in the evaluation using only the differential luminance value ΔPL, an accurate comparative evaluation with other solar cell strings 12 cannot be performed. For this reason, in the present invention, the solar cell string 12 is evaluated by quantifying using a pseudo FF value that applies the fill factor (FF), which is an index of the I-V characteristic, using the open-circuit voltage value Voc and the short-circuit current specification value Isc.

[0045] Referring to the I-V characteristic shown in FIG. 3, point (a) indicates the operating point of the solar cell string 12 when the switch 21 is in the open state, and point (b) indicates the operating point when the solar cell string 12 is operated at the maximum power point by maximum power point tracking control (MPPT). The voltage value at point (a) when not energized is the open-circuit voltage value Voc, and the PL luminance value (emission intensity) PL(a) at point (a) is larger than the PL luminance value (emission intensity) PL(b) in the energized state.

[0046] The FF value as an index of the electrical characteristics in the I-V characteristic can be expressed by the following equation from the maximum power generation value P(MPP), the open-circuit voltage value Voc, and the short-circuit current value Isc’. FF value = P(MPP) / (Voc × Isc’)

[0047] On the other hand, since the differential luminance value ΔPL, which is the difference between the PL luminance value PL(a) and the PL luminance value PL(b), is a variable in the same dimension as the maximum power generation value P(MPP), in the present invention, the pseudo-FF value is obtained from the following formula. Pseudo-FF value = ΔPL / (Voc × Isc) Here, since it is difficult to obtain the short-circuit current value Isc’ in the field, the short-circuit current specification value Isc obtained from the specification values of the solar cell modules 11 of the target solar cell string 12 is used.

[0048] In a photovoltaic power generation system, usually, since solar cell modules 11 of the same specification are used, the FF values of normal solar cell strings 12 are the same. Similarly, for the pseudo-FF value, since the pseudo-FF values of normal solar cell strings 12 are the same, the solar cell strings 12 of the entire photovoltaic power generation system can be accurately compared and evaluated. Therefore, by comparing the pseudo-FF value obtained by inspection with the pseudo-FF value at the time of installation of the solar cell string 12 to be inspected, or by comparing it with the pseudo-FF values of other solar cell strings of the same specification at the time of inspection, it is possible to evaluate and determine the superiority or inferiority of the power generation performance.

[0049] Next, a method for inspecting a solar cell panel will be described. FIG. 4 is a diagram for explaining an inspection flow in the method for inspecting a solar cell panel according to the present invention. While also referring to the configuration example of FIG. 2, the procedure of the method for inspecting a solar cell panel will be described.

[0050] The inspection of the solar cell panel is performed in a state where sunlight L is irradiating the solar cell string 12. First, in step S1, the switch 21 connected to the solar cell string 12 to be inspected is opened by the switch control means 108, and at the same time, it is connected to the voltmeter 60 so that the terminal voltage of the solar cell string 12 can be measured.

[0051] Next, move to step S2. The PL image generation means 101 operates the camera 50 to photograph the entire solar cell string 12, and records the acquired photographed image in the storage unit 120 (step S3). The camera 50 is installed in advance so as to be able to photograph the entire solar cell string 12. However, if the camera 50 cannot photograph the entire solar cell string 12 in one shot, the solar cell modules 11 may be photographed in plural or one by one. The process from step S2 to step S3 is the open state PL image photographing step for generating the open state PL image.

[0052] Next, move to step S4, and repeat the process from step S2 to step S3 N times (for example, 50 times). This is because in later processing, in order to obtain the determination PL image as a differential image that can be luminance-counted, it is necessary to obtain a clearer PL image from a plurality of photographed images. Next, move to step S5. The voltage measurement means 104 acquires the open circuit voltage value Voc measured by the voltmeter 60 and stores it in the storage unit 120. The process in step S5 is the open circuit voltage value measurement step.

[0053] Next, move to step S6. The switch control means 108 closes the switch 21 connected to the solar cell string 12 to be inspected. As a result, the solar cell string 12 is operated under the maximum power point tracking control by the PCS 40 and operates at the point (b) in the I-V characteristics shown in FIG. 3.

[0054] Next, move to step S7. The PL image generation means 101 operates the camera 50 to photograph the entire solar cell string 12, and records the acquired photographed image in the storage unit 120 (step S8). If the camera 50 cannot photograph the entire solar cell string 12 in one shot, similar to step S2, the solar cell modules 11 may be photographed in plural or one by one. Next, move to step S9, and repeat the process from step S7 to step S8 N times (for example, 50 times). This is for the same reason as in the case of obtaining the open state PL image. The process from step S7 to step S8 is the closed state PL image photographing step for generating the closed state PL image.

[0055] Next, it moves to step S10, and the determination PL image generation means 102 generates a determination PL image composed of the difference image between the open-state PL image and the closed-state PL image temporarily stored in the storage unit 120. When there are a plurality of open-state PL images and closed-state PL images respectively, as described above, a determination PL image, which is a difference image, is generated based on the average image obtained by averaging the luminance values of each pixel. The process in step S10 becomes the determination PL image generation step. Next, it moves to step S11, and the ΔPL calculation means 103 identifies the positions of the solar cells in the solar cell string 12 from the determination PL image generated by the determination PL image generation means 102, counts the luminance values of the pixels corresponding to the solar cells, calculates the differential luminance value ΔPL, and stores the calculated differential luminance value ΔPL in the storage unit 120. The process in step S11 becomes the ΔPL calculation step.

[0056] Next, it moves to step S12, and the pseudo-FF value calculation means 105 reads out the short-circuit current specification value Isc stored in the storage unit 120. Similarly, it reads out the open-circuit voltage value Voc and the differential luminance value ΔPL stored in the storage unit 120, and in step S13, calculates the pseudo-FF value (=ΔPL / (Voc×Isc)). The calculated pseudo-FF value is transmitted to the display / alarm means 107 in step S14 and displayed on a display panel or the like. Here, when obtaining the pseudo-FF value of the solar cell string 12 composed of solar cell modules 11 of the same specification, in the calculation formula, the short-circuit current specification value Isc has the same value, so for example, the value can be handled as 1. The process in step S13 becomes the pseudo-FF value calculation step.

[0057] Although a series of processes can end at step S14, when automatically determining the power generation performance of a solar cell panel, the process moves from step S14 to step S15, and the power generation performance determination means 106 evaluates the performance of the solar cell string 12 that is the subject of the current inspection. Regarding the method for evaluating power generation performance, it can be performed by either or both of the two methods as described above, and it can be performed by the method selected in advance. Regarding the determination result determined by the power generation performance determination means 106, it is sent to the display / alarm means 107 at step S16 and displayed on a display panel or the like.

[0058] In this embodiment, performance evaluation is performed in units of the solar cell string 12 operated by the switch 21. However, when it is desired to identify a solar cell module 11 with deteriorated performance among the solar cell strings 12, using the determination PL image, which is the difference image between the open-state PL image and the closed-state PL image, the differential luminance value ΔPL is calculated in units of the solar cell module 11, and the performance deterioration of the solar cell module 11 can be determined by comparing the obtained differential luminance value ΔPL with the differential luminance values ΔPL of other solar cell modules of the same specification.

[0059] As described above, in this embodiment, the inspection in units of the solar cell string 12 as the inspection target has been described. However, the present invention can evaluate the power generation performance in units of the unit for operating the switch (solar cell string unit or solar cell array unit). When performing the inspection in units of the solar cell array 13 as the inspection target, the switch control means 108 controls the opening and closing of each switch 31 of the power distribution box 30, the PL image generation means processes the captured images for each solar cell array 13, and the voltage measurement means 104 measures the open-circuit voltage value Voc for each solar cell array 13. Then, the pseudo-FF value calculation means 105 calculates the pseudo-FF value in units of the solar cell array 13.

Explanation of Reference Numerals

[0060] 11…Solar cell module 12…Solar cell string 13…Solar cell array 20…Connection box 21…Switch 30…Collecting box 31…Switch 50…Camera 60…Voltmeter 100…Inspection device main body 101…PL image generation means 102…PL image generation means for determination 103…ΔPL calculation means 104…Voltage measurement means 105…Pseudo FF value calculation means 106…Power generation performance determination means 107…Alarm means 108…Switch control means 110…CPU 120…Memory unit 121…Pseudo FF value

Claims

1. An inspection device for a solar panel connected via a switch to a power conditioner that performs maximum power point tracking control (MPPT), comprising: imaging means for imaging the solar panel; PL image generation means for generating an open state PL image captured by the imaging means with the switch open and the solar panel in an open state under sunlight irradiation, and a closed state PL image captured by the imaging means with the switch closed and the solar panel operating at the maximum power point (MPP) under the control of the power conditioner under sunlight irradiation; determination PL image generation means for generating a determination PL image composed of a difference image between the open state PL image and the closed state PL image; ΔPL calculation means for calculating a difference luminance value ΔPL of the solar panel from the determination PL image; voltage measurement means for measuring an open circuit voltage value Voc of the solar panel in a state where the switch is open and the solar panel is open under sunlight irradiation; simulated FF value calculation means for calculating ΔPL / (Voc×Isc) as a simulated FF value from the short circuit current specification value Isc of the solar panel, the open circuit voltage value Voc, and the difference luminance value ΔPL; An inspection device for a solar panel, characterized by comprising the above.

2. The inspection device for a solar panel according to claim 1, wherein the determination PL image is generated from a plurality of the captured open state PL images and a plurality of the captured closed state PL images, respectively.

3. The inspection device for a solar panel according to claim 1 or 2, further comprising power generation performance determination means for determining the power generation performance of the solar panel based on the simulated FF value.

4. The inspection device for a solar panel according to claim 3, wherein the power generation performance determination means determines the power generation performance by comparing the current simulated FF value of the solar panel to be inspected with the past simulated FF value of the solar panel to be inspected.

5. The inspection device for a solar panel according to claim 3, wherein the power generation performance determination means determines the power generation performance by comparing the current simulated FF value of the solar panel to be inspected with the current simulated FF value of another solar panel having the same specification as the solar panel to be inspected.

6. A method for inspecting a solar panel connected via a switch to a power conditioner that performs maximum power point tracking control (MPPT), an open-state PL image capturing step of capturing an open-state PL image of the solar panel with the switch open and released under sunlight irradiation, an open-circuit voltage value measuring step of measuring an open-circuit voltage value Voc of the solar panel with the switch open and released under sunlight irradiation, a closed-state PL image capturing step of capturing a closed-state PL image of the solar panel with the switch closed and operating at the maximum power point (MPP) under the control of the power conditioner under sunlight irradiation, a determination-use PL image generating step of generating a determination-use PL image composed of a difference image between the open-state PL image and the closed-state PL image, a ΔPL calculating step of calculating a difference luminance value ΔPL of the solar panel from the determination-use PL image, a pseudo-FF value calculating step of calculating ΔPL / (Voc × Isc) as a pseudo-FF value from the short-circuit current specification value Isc of the solar panel, the open-circuit voltage value Voc, and the difference luminance value ΔPL, and characterized by determining the power generation performance of the solar panel based on the pseudo-FF value, a method for inspecting a solar panel.

7. The method for inspecting a solar panel according to claim 6, characterized in that the determination-use PL image is generated from a plurality of the captured open-state PL images and a plurality of the captured closed-state PL images.

8. The method for inspecting a solar panel according to claim 6 or 7, characterized in that the determination of the power generation performance of the solar panel is performed by comparing the current pseudo-FF value in the solar panel to be inspected with the past pseudo-FF value in the solar panel to be inspected.

9. The method for inspecting a solar panel according to claim 6 or 7, characterized in that the determination of the power generation performance of the solar panel is performed by comparing the current pseudo-FF value in the solar panel to be inspected with the current pseudo-FF value in another solar panel having the same specification as the solar panel to be inspected.

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