CN114665816A - A junction box, photovoltaic module and test method for hot spot temperature thereof - Google Patents

Abstract

The invention discloses a junction box, a photovoltaic module and a method for testing the hot spot temperature thereof. The junction box includes n diodes, n+1 external terminals, n switches, and a box body, wherein n diodes and n switches are located inside the box, n+1 external terminals are located outside the box, and the mth diode is located outside the box. The first pole, the first terminal of the mth switch and the mth external terminal are electrically connected, the second pole of the mth diode, the second terminal of the mth switch and the m+1th external terminal are electrically connected, wherein , is a positive integer greater than or equal to 2, m is a positive integer greater than or equal to 1 and less than or equal to n. In the technical solution provided by the embodiments of the present invention, the short-circuit current of the battery string unit where the worst cell is located is obtained through testing, so as to confirm the most severe shielding area of the shielded battery piece, so as to realize the more rapid and accurate determination of the most severe shielding area of the battery assembly. Therefore, the hot spot risk of solar cell modules can be more accurately assessed.

Description

A junction box, photovoltaic module and test method for hot spot temperature thereof

technical field

The embodiments of the present invention relate to the technical field of solar photovoltaic modules, and in particular, to a junction box, a photovoltaic module and a method for testing the hot spot temperature thereof.

Background technique

Solar cells use the photovoltaic effect to convert solar radiation into electrical energy. Under the situation that traditional energy sources are becoming increasingly scarce, solar cells will become an important alternative energy source in the future. When the solar cell module generates energy, the shaded solar cell module will generate heat, resulting in a hot spot effect. With the rapid growth of market demand for photovoltaic modules, the power of photovoltaic modules is also getting higher and higher, and the risk of hot spots of solar cell modules is also increasing. Fully assessing the risk of hot spot will help reduce the risk of hot spot failure of solar cell module products, improve the income of power station investors, and escort the sustainable development of alternative energy sources.

At present, when testing the hot spot of a solar cell module, it is necessary to read the volt-ampere characteristic curve of the shaded solar cell module. According to the inflection point in the volt-ampere characteristic curve, the current at the inflection point is equal to the maximum operating current of the solar cell module. , in order to obtain a strict occlusion area. However, in the actual test, there is no obvious inflection point in the volt-ampere characteristic curve after some cells are shaded, resulting in errors in the reading of the most severe shaded area, which in turn leads to a low maximum hot spot temperature of the solar cell module, which affects the Product design and accurate judgment of hot spot performance.

SUMMARY OF THE INVENTION

The invention provides a junction box, a photovoltaic module and a method for testing the hot spot temperature thereof, which can quickly and accurately determine the most severe shielding area of a solar cell module, and then more accurately evaluate the hot spot risk of the solar cell module.

In a first aspect, an embodiment of the present invention provides a junction box, including:

n diodes, n+1 external terminals, n switches, and a box;

Wherein, n diodes and n switches are located in the box body;

n+1 external terminals are located outside the box;

The first pole of the mth diode, the first end of the mth switch and the mth external terminal are electrically connected, and the second pole of the mth diode, the second terminal of the mth switch and the m+1th external terminal are electrically connected. terminal electrical connection;

Wherein, is a positive integer greater than or equal to 2, and m is a positive integer greater than or equal to 1 and less than or equal to n.

In a second aspect, the present invention further provides a photovoltaic module, comprising the junction box described in the first aspect and n battery string units, wherein the battery string unit includes one or two battery strings, and the battery string includes a plurality of battery slices connected in series; each of the diodes is in anti-parallel with each of the battery strings in one of the battery string units.

Optionally, it is characterized in that n=3.

In a third aspect, the present invention also provides a method for testing the hot spot temperature of a photovoltaic module, which is used to test the photovoltaic module described in any of the above aspects, including:

Obtain the maximum power point current of the photovoltaic module under the preset light intensity;

Determine the worst cell in the PV module;

Test the short-circuit current of the battery string unit where the worst cell is located under different shielding areas of the worst cell;

According to the short-circuit current and the maximum power point current, determine the most severe shielding area of the worst cell;

determining the location of the hot spot on the worst cell;

Covering the worst cell, keeping the hot spot position of the worst cell exposed, and the shaded area is equal to the most severe shaded area;

The photovoltaic module is exposed to the sun, and the temperature at the hot spot position is obtained by testing as the hot spot temperature of the photovoltaic module.

Optionally, the preset light intensity is 1000W/㎡.

Optionally, obtaining the maximum power point current of the photovoltaic module under the preset light intensity includes:

The volt-ampere characteristic curve of the photovoltaic module is obtained by testing under the preset light intensity;

According to the volt-ampere characteristic curve, the maximum power point current is determined.

Optionally, determining the worst cell in the photovoltaic module includes:

Completely shield each of the cells in the photovoltaic module in turn, and after each of the cells is completely shielded, the leakage current of the photovoltaic module is obtained by testing;

It is determined that the battery slice corresponding to the maximum leakage current is the worst battery slice.

Optionally, when testing different shaded areas of the worst cell, the short-circuit current of the battery string unit where the worst cell is located includes:

The battery string unit where the worst cell is located is the first battery string unit, the battery string units other than the first battery string unit are the second battery string unit, and each battery in the first battery string unit The diodes connected in antiparallel in series are the first diodes, and the diodes connected in antiparallel with each battery string in the second battery string unit are the second diodes; disconnect all the diodes connected in parallel with the first diodes. the switch, and close the switch connected in parallel with the second diode;

The output current of the photovoltaic module under different shielding areas of the worst cell is tested as the short-circuit current of the cell string unit where the worst cell is located.

Optionally, test the output current of the photovoltaic module under different shielding areas of the worst cell, as the short-circuit current of the battery string unit where the worst cell is located, including:

Taking the preset area as the variation, starting from the shaded area of the worst cell being 0, and increasing the shaded area of the worst cell in sequence, or starting from the worst cell being completely shaded, sequentially Reduce the shaded area of the worst cell; after each increase or decrease of the shaded area of the worst cell, test the output current of the photovoltaic module once, and use the output current as the corresponding shade the short-circuit current of the battery string unit where the worst battery slice is located under the area;

Wherein, the preset area is 5% of the area of the worst cell sheet.

Optionally, according to the short-circuit current and the maximum power point current, determining the most severe shielding area of the worst cell sheet includes:

It is determined that the short-circuit current with the smallest difference with the maximum power point current is the first short-circuit current, and the shaded area of the worst cell corresponding to the first short-circuit current is determined to be the worst cell of the worst cell. Strictly cover the area.

Optionally, determining the location of the hot spot on the worst cell sheet includes:

An infrared detection device is used to determine the position of the hot spot on the worst cell.

Optionally, the photovoltaic module is exposed to the sun, and the temperature at the hot spot position obtained by testing as the hot spot temperature of the photovoltaic module includes:

Expose the photovoltaic assembly to the sun, and use a thermocouple or an infrared detection device attached to the hot spot position to test and obtain the temperature of the hot spot position as the hot spot temperature of the photovoltaic assembly.

The junction box provided by the embodiment of the present invention includes n diodes, n+1 external terminals, n switches, and a box body, wherein the n diodes and n switches are located in the box body, and n+1 external terminals are located in the box Outside the body, the first pole of the mth diode, the first end of the mth switch and the mth external terminal are electrically connected, the second pole of the mth diode, the second end of the mth switch and the m+1 Each external terminal is electrically connected, wherein m is a positive integer greater than or equal to 2, m is a positive integer greater than or equal to 1 and less than or equal to n, the external terminals are connected to a plurality of battery string units in the solar cell module, and are sequentially connected by blocking Select a cell with the largest leakage current in the module, take this cell as the worst cell in the module, open the switch corresponding to the battery string unit where the worst cell is located, and close the junction box to remove the cell string All switches corresponding to the unit are tested to obtain the short-circuit current of the battery string unit where the worst cell is located, so as to confirm the most severe shielding area of the shielded sheet, so as to achieve a faster and more accurate determination of the most severe shielding area of the battery module, and furthermore Accurately assess the hot spot risk of solar modules.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

1 is a schematic structural diagram of a junction box provided by an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a photovoltaic module according to an embodiment of the present invention;

3 is a connection diagram of a battery string unit and a diode according to an embodiment of the present invention;

FIG. 4 is a schematic structural diagram of another photovoltaic module provided by an embodiment of the present invention;

FIG. 5 is a schematic flowchart of a method for testing a hot spot temperature of a photovoltaic module according to an embodiment of the present invention.

Detailed ways

In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the following describes the specific implementation, structure, structure, Features and their effects are described in detail below.

An embodiment of the present invention provides a junction box, including:

n diodes, n+1 external terminals, n switches, and a box;

Wherein, n diodes and n switches are located in the box body;

n+1 external terminals are located outside the box;

The first pole of the mth diode, the first end of the mth switch and the mth external terminal are electrically connected, and the second pole of the mth diode, the second terminal of the mth switch and the m+1th external terminal are electrically connected. terminal electrical connection;

Wherein, is a positive integer greater than or equal to 2, and m is a positive integer greater than or equal to 1 and less than or equal to n.

The junction box provided by the embodiment of the present invention includes n diodes, n+1 external terminals, n switches, and a box body, wherein the n diodes and n switches are located in the box body, and n+1 external terminals are located in the box Outside the body, the first pole of the mth diode, the first end of the mth switch and the mth external terminal are electrically connected, the second pole of the mth diode, the second end of the mth switch and the m+1 Each external terminal is electrically connected, wherein m is a positive integer greater than or equal to 2, m is a positive integer greater than or equal to 1 and less than or equal to n, the external terminals are connected to a plurality of battery string units in the solar cell module, and are sequentially connected by blocking Select a cell with the largest leakage current in the module, take this cell as the worst cell in the module, open the switch corresponding to the battery string unit where the worst cell is located, and close the junction box to remove the cell string All switches corresponding to the unit are tested to obtain the short-circuit current of the battery string unit where the worst cell is located, so as to confirm the most severe shielding area of the shielded sheet, so as to determine the most severe shielding area of the battery module more quickly and accurately, and then More accurate assessment of hot spot risk for solar modules.

The above is the core idea of the present application. The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention. not all examples. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present invention.

Many specific details are set forth in the following description to facilitate a full understanding of the present invention, but the present invention can also be implemented in other embodiments different from those described herein, and those skilled in the art can do so without departing from the connotation of the present invention. Similar promotions are made, so the present invention is not limited by the specific embodiments disclosed below.

Next, the present invention is described in detail with reference to the schematic diagrams. When describing the embodiments of the present invention in detail, for the convenience of explanation, the schematic diagrams showing the structures of the devices are not partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not be limited here. The scope of protection of the present invention. In addition, the three-dimensional spatial dimensions of length, width and height should be included in the actual production.

FIG. 1 is a schematic structural diagram of a junction box according to an embodiment of the present invention. As shown in FIG. 1 , the junction box includes n diodes 10 , n+1 external terminals 11 , n switches 12 , and a box body 13 , wherein n diodes 10 and n switches 12 are located in the box body 13 , the n+1 external terminals 11 are located outside the box body 13, the first pole of the mth diode 10, the first end of the mth switch 12 and the mth external terminal 11 are electrically connected, and the mth diode 10 is electrically connected. The diode, the second end of the mth switch 12 and the m+1th external terminal 11 are electrically connected, wherein n is a positive integer greater than or equal to 2, m is a positive integer greater than or equal to 1 and less than or equal to n .

Among them, the n diodes 10 and the n switches 12 are wrapped by the box body 13. Among the n+1 external terminals 11, each two external terminals 11 is connected to a diode 10, and one diode 10 is reversely connected to an external battery string unit. , and n diodes 10 in the junction box are connected in series.

1, the junction box includes 3 diodes 10, 4 external terminals 11, 3 switches 12 and a box body 13, wherein 3 diodes 10 and 3 switches 12 are located in the box body 13, 4 The external terminal 11 is located outside the box body 13 . When the first pole of the first diode 10, the first terminal of the first switch 12 and the first external terminal 11 are electrically connected, the second pole of the first diode 10, the second terminal of the first switch and the first external terminal 11 are electrically connected. The two external terminals are electrically connected, and the switch in the junction box can effectively control the on or off of the battery string unit connected to the external terminal, and effectively measure the short-circuit current of the battery string unit.

It should be noted that, in this embodiment, n=3 and m=1 are used as an example for description. In other embodiments, n is a positive integer greater than or equal to 2, and m is greater than or equal to 1 and less than or A positive integer equal to n is sufficient.

Specifically, the external terminals in the junction box are connected to a plurality of battery string units in the solar cell module, and one cell with the largest leakage current in the module is selected in turn by blocking, and this cell is used as the worst cell in the module. , open the switch corresponding to the battery string unit where the worst cell is located, and close all the switches corresponding to the battery string unit in the junction box except for the battery string unit, and test to obtain the short-circuit current of the battery string unit where the worst cell is located, so as to confirm The most severe occlusion area of the occluded sheet.

The junction box provided in this embodiment includes n diodes, n+1 external terminals, n switches, and a box body, wherein n diodes and n switches are located inside the box; n+1 external terminals are located outside the box , the first pole of the mth diode, the first end of the mth switch and the mth external terminal are electrically connected, the second pole of the mth diode, the second end of the mth switch and the m+1th The external terminals are electrically connected, wherein n is a positive integer greater than or equal to 2, m is a positive integer greater than or equal to 1 and less than or equal to n, the external terminals are connected to a plurality of battery string units in the solar cell module, and are sequentially connected by blocking Select a cell with the largest leakage current in the module, take this cell as the worst cell in the module, open the switch corresponding to the battery string unit where the worst cell is located, and close the junction box to remove the cell string All switches corresponding to the unit are tested to obtain the short-circuit current of the battery string unit where the worst cell is located, so as to confirm the most severe shielding area of the shielded sheet, so as to achieve a faster and more accurate determination of the most severe shielding area of the battery module, and furthermore Accurately assess the hot spot risk of solar modules.

FIG. 2 is a schematic structural diagram of a photovoltaic module according to an embodiment of the present invention. As shown in FIG. 2 , the photovoltaic module includes the junction box 20 provided in the above embodiment and n battery string units 21 . The battery string unit 21 includes a battery string, and the battery string includes a plurality of battery sheets 22 connected in series. FIG. 3 is a diagram illustrating a connection relationship between a battery string unit and a diode according to an embodiment of the present invention. As shown in FIG. 3 , each diode 30 is connected in anti-parallel to each battery string in one battery string unit 21 .

Exemplarily, the junction box includes 3 diodes, 4 external terminals, 3 switches and 3 battery string units as an example for description below.

2 and 3 , the battery string unit 21 is connected to the junction box 20 through wires. The photovoltaic module includes the junction box provided in the above embodiment and three battery string units 21. Each battery string unit 21 includes a battery string. The string includes a plurality of battery slices 22 connected in series, and each diode 30 is connected in anti-parallel to each battery string in one battery string unit 21 .

Specifically, when the 4 external terminals in the junction box are connected to the 3 battery string units in the photovoltaic module, a cell with the largest leakage current in the photovoltaic module is selected by shading, and the cell is used as the photovoltaic module. The worst cell in the world. For example, three battery string units 21 are arranged from left to right. If the worst battery slice is located in the first battery string unit, the switch connected to the second battery string unit in the junction box and the switch connected to the third battery string unit in the junction box are turned off. The switch connected to the battery string unit, that is, the second battery string unit and the third battery string unit from left to right are short-circuited to test the short-circuit current of the first battery string unit where the worst cell is located. If the worst cell is located in the second battery string unit, turn off the switch connected to the first battery string unit and the switch connected to the third battery string unit in the junction box, that is, from left to right The first battery string unit and the third battery string unit are short-circuited, so as to measure the short-circuit current of the second battery string unit where the worst cell is located. Short-circuit current for three string cells.

According to this arrangement, when each battery string unit includes a battery string, the worst battery cell in a battery string unit can be quickly selected, thereby improving the hot spot test efficiency of the photovoltaic module.

FIG. 4 is a schematic structural diagram of another photovoltaic module provided by an embodiment of the present invention. As shown in FIG. 4 , the photovoltaic module includes the junction box (not shown) provided in the above embodiment and n battery string units 21 , the battery string unit includes 21 and two battery strings 22 , and the battery string includes a plurality of batteries connected in series Plate 23 , each diode 30 is connected in anti-parallel to each battery string in one battery string unit 21 .

Among them, a battery string unit includes two battery strings, and the two battery strings share a diode in anti-parallel connection.

Similarly, in this embodiment, the photovoltaic module includes the junction box provided in the above embodiment and three battery string units, each battery string unit includes two battery strings, wherein the junction box provided in the above embodiment includes three battery strings A diode, 4 external terminals, and 3 switches are used as an example.

Specifically, after selecting the cell with the largest leakage current in the photovoltaic module as the worst cell, the method of testing the short-circuit current of the battery string unit where the worst cell is located is the same as that adopted in the above-mentioned embodiment. It is not repeated here.

Optionally, n=3.

Among them, in this embodiment, the photovoltaic module includes 3 battery string units, which is conducive to testing the short-circuit current of the battery string unit where the worst cell is located, and the measured short-circuit current is used to further confirm the maximum value of the blocked cell in the photovoltaic module. Strict shading area is beneficial to improve the accuracy of assessing the risk of hot spot of photovoltaic modules.

FIG. 5 is a schematic flowchart of a method for testing a hot spot temperature of a photovoltaic module according to an embodiment of the present invention. This method is suitable for testing the photovoltaic modules provided in any of the above embodiments. As shown in FIG. 5 , the method may specifically include the following:

S510. Obtain the maximum power point current of the photovoltaic module under the preset light intensity.

It should be noted that the maximum power point current is obtained from the volt-ampere characteristic curve of the solar cell formed when the photovoltaic module is tested. Among them, the volt-ampere characteristic curve of the solar cell is a curve drawn by the working voltage and current values corresponding to the solar cells with different resistance values. The curve includes the maximum power point, the open-circuit voltage point and the short-circuit current point. According to the volt-ampere The characteristic curve can calculate the output power of the solar cell.

S520. Determine the worst cell in the photovoltaic module.

Among them, due to factors such as manufacturing process and impure raw materials, it is inevitable for solar cells to generate leakage current. When judging a cell with the worst electrical performance among all cells in a photovoltaic module, the leakage current of all cells is mainly analyzed and compared.

S530 , testing the short-circuit current of the battery string unit where the worst cell is located under different shielding areas of the worst cell.

Specifically, after the worst cell sheet is determined in step S520, the worst cell sheet is shaded under different shaded areas. In this embodiment, the shading area of the worst cell can be increased or decreased sequentially by an equal amount. After each time the shading area of the worst cell is increased or decreased, the battery string unit where the worst cell is located is tested once. short circuit current.

S540. Determine the most severe shielding area of the worst cell according to the short-circuit current and the maximum power point current.

Wherein, in step S510, according to the maximum power point current obtained from the volt-ampere characteristic curve of the photovoltaic module under the preset light intensity, the short-circuit current of the battery string unit where the worst cell is located and the maximum power point current obtained in step S530 are calculated as For comparison, when the short-circuit current of the battery string where the worst cell is located is equal to the maximum power point current of the photovoltaic module, read the shading area of the worst cell at this time, and use this area as the worst cell when the hot spot effect occurs. Harsh blocking area.

S550. Determine the hotspot position on the worst cell sheet.

S560. Block the non-hot spots on the worst cell, keep the hot spots of the worst cell exposed, and the shaded area is equal to the most severe shade.

Wherein, after determining the position of the worst cell in the cell string unit of the photovoltaic module, the non-hot spot of the worst cell is still shielded by shading, so as to expose the determined hot spot on the worst cell.

S570 , exposing the photovoltaic module to the sun, and obtaining the temperature of the hot spot by testing as the hot spot temperature of the photovoltaic module.

Specifically, the photovoltaic module is placed in a steady state simulator for exposure, wherein the light intensity of the photovoltaic module exposure is the preset light intensity set for testing the maximum power point current of the photovoltaic module provided in the above embodiment.

It should be noted that the steady-state simulator in the solar photovoltaic module is a device for testing the electrical performance parameters of the solar cell by simulating sunlight irradiating the surface of the solar cell, and is an important performance testing equipment in the production of solar cells and photovoltaic modules. In this embodiment, the steady state simulator may be a filtered xenon lamp, a two-color filtered tungsten lamp-ELH lamp or an improved mercury lamp.

The technical solution provided in this embodiment is to determine the worst cell in the photovoltaic module by obtaining the maximum power point current of the photovoltaic module under the preset light intensity, and test the battery where the worst cell is located under different shading areas of the worst cell. The short-circuit current of the string unit, according to the short-circuit current and the maximum power point current, determine the most severe blocking area of the worst cell, determine the hot spot position on the worst cell, block the worst cell, and maintain the hot spot position of the worst cell Exposure, and the shaded area is equal to the most severe shaded area, expose the PV modules to the sun, and test the temperature at the hot spot as the hot spot temperature of the PV modules, so as to achieve a faster and more accurate determination of the most severe shaded area of the battery modules, and further Accurately assess the hot spot risk of solar modules.

Optionally, the preset light intensity is 1000W/㎡.

Among them, the preset light intensity is a reasonable preset made by the tester based on the volt-ampere characteristic curve of the photovoltaic module when testing the solar photovoltaic module. When the preset light intensity is 1000W/㎡, the photovoltaic can be accurately obtained. The short-circuit current of the module, the maximum power point current and the maximum output power of the photovoltaic module.

Optionally, obtaining the maximum power point current of the photovoltaic module under the preset light intensity includes: testing and obtaining the volt-ampere characteristic curve of the photovoltaic module under the preset light intensity, and determining the maximum power point current according to the volt-ampere characteristic curve.

It should be noted that, when testing photovoltaic modules under the condition of light intensity of 1000W/m2, the volt ^- ampere characteristic curve can be directly drawn by the tester.

Optionally, determining the worst cell in the photovoltaic module includes: sequentially completely blocking each cell in the photovoltaic module, after each cell is completely blocked, testing to obtain the leakage current of the photovoltaic module, and determining the corresponding maximum leakage current. The cell is the worst cell.

Specifically, after the photovoltaic module is energized, all the cells in the photovoltaic module are tested in turn by shading, and the leakage current corresponding to the cell can be obtained by testing each cell. After the leakage current, the cell with the largest leakage current is selected as the worst cell in the photovoltaic module.

Optionally, when testing different shielding areas of the worst cell, the short-circuit current of the battery string unit where the worst cell is located includes: the battery string unit where the worst cell is located is the first battery string unit, except for the first battery string unit The battery string unit is the second battery string unit, the diode in anti-parallel with each battery string in the first battery string unit is the first diode, and the diode in anti-parallel with each battery string in the second battery string unit is the first diode. Two diodes, disconnect the switch connected in parallel with the first diode, close the switch connected in parallel with the second diode, and test the output current of the photovoltaic module under different shading areas of the worst cell, as the location of the worst cell The short-circuit current of the battery string unit.

2, a plurality of battery string units are arranged from left to right. If the worst battery slice is located in the first battery string unit, the batteries other than the first battery string unit can be removed. The string units are used as second battery string units, disconnect the diodes in anti-parallel with each battery string in the first battery string unit, and close the diodes in anti-parallel with each battery string in the second battery string unit. The second battery string unit is short-circuited, so as to obtain the short-circuit current of the first battery string unit where the worst cell is located.

Optionally, test the output current of the photovoltaic module under different shaded areas of the worst cell, as the short-circuit current of the cell string unit where the worst cell is located, including: taking the preset area as the variation, from the shaded area of the worst cell Starting from the area of 0, increase the shaded area of the worst cell in turn, or, starting from the worst cell being completely shaded, decrease the shaded area of the worst cell in turn, increasing or decreasing each time After the shaded area of the worst cell, test the output current of the photovoltaic module once, and use the output current as the short-circuit current of the cell string unit where the worst cell is located under the corresponding shaded area, where the preset area is the worst cell 5% of the area of the sheet.

It should be noted that when the short-circuit current of the battery string where the worst cell is located is higher than the maximum power point current obtained from the solar volt-ampere characteristic curve, continue to increase the shaded area of the worst cell until the shade is increased. After the area, the short-circuit current obtained by the test is the same as the maximum power point current. If the short-circuit current of the battery string where the worst cell is located is lower than the maximum power point current obtained from the volt-ampere characteristic curve, reduce the shaded area of the worst cell, so that the short-circuit current of the battery string where the worst cell is located is equal to the photovoltaic module up to the maximum operating point current.

Optionally, according to the short-circuit current and the maximum power point current, determining the most severe shading area of the worst cell includes: determining the short-circuit current with the smallest difference from the maximum power point current as the first short-circuit current, and determining the corresponding first short-circuit current. The shaded area of the worst cell is the most severe shaded area of the worst cell.

Exemplarily, taking 5% of the area of the worst cell as the variation, starting from the shaded area of the worst cell being 0, and increasing the shaded area of the worst cell in turn, when it increases to the worst cell When it is 10% of the cell, the short-circuit current I1 of the photovoltaic module can be tested. When it increases to 15% of the worst cell, the short-circuit current I2 of the photovoltaic module can be tested. At this time, I1 can be compared with the maximum power point. The current difference and the difference between I2 and the maximum power point current, if the difference between I1 and the maximum power point current is less than the difference between I2 and the maximum power point current, at this time, I2 is selected as the first short-circuit current, and the first short-circuit current is determined. The shaded area of the worst cell corresponding to the short-circuit current is the most severe shaded area of the worst cell.

Alternatively, starting from the worst cell being completely blocked, that is, starting from 100% of the area of the worst cell, and decreasing the shaded area of the worst cell in turn, a cell with the smallest difference from the maximum power point current can be obtained. The short-circuit current is the second short-circuit current, and the shaded area of the worst cell corresponding to the second short-circuit current is determined as the most severe shaded area of the worst cell.

Optionally, determining the hot spot position on the worst cell sheet includes: using an infrared detection device to determine the hot spot position on the worst cell sheet.

Among them, the infrared detection device is designed to measure the surface temperature when heat flows in, out and/or through the object, and can determine the location of the hot spot by thermal imaging, which can collect the hot spot very quickly in a non-contact manner within a certain range, and further to determine the hotspot location.

Optionally, exposing the photovoltaic module to the sun, and testing to obtain the temperature of the hot spot as the hot spot temperature of the photovoltaic module includes: exposing the photovoltaic module to the sun, and using a thermocouple or infrared detection device attached to the hot spot to test and obtain the hot spot position. The temperature is used as the hot spot temperature of the photovoltaic module.

Among them, a thermocouple belongs to a kind of thermoelectric device, which is a temperature measuring element commonly used in temperature measuring instruments. It can convert temperature signals into thermoelectromotive force signals, and convert them into the temperature of the measured medium through equipment such as secondary instruments.

Specifically, when testing the output current of the photovoltaic module under different shading areas of the worst cell, taking the output current as the short-circuit current of the battery string unit where the worst cell is located, and judging that the short-circuit current is equal to the maximum power point current, determine The shaded area of the worst cell corresponding to the short-circuit current is the most severe shaded area of the worst cell, and the most severe shaded area is used to determine the hotspot position of the worst cell, and to block the worst cell At the hot spot position, the photovoltaic module is irradiated with a preset light intensity, and the temperature at the hot spot position is measured by using a thermocouple or infrared detection device attached to the hot spot position, and the temperature at the hot spot position is used as the hot spot temperature of the photovoltaic module, so that the photovoltaic module can be accurately obtained. The most severe shielding area of the hot spot can avoid the reading error caused by the unclear inflection point in the volt-ampere characteristic curve of the photovoltaic module, and can evaluate the hot spot effect of the photovoltaic module more quickly and accurately.

Note that the above are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and can also include more other equivalent embodiments without departing from the concept of the present invention. The scope is determined by the scope of the appended claims.

Claims (12)

1. A junction box, comprising:

n diodes, n +1 external terminals, n switches, and a case;

the n diodes and the n switches are positioned in the box body;

n +1 external terminals are positioned outside the box body;

the first pole of the mth diode, the first end of the mth switch and the mth external terminal are electrically connected, and the second pole of the mth diode, the second end of the mth switch and the (m + 1) th external terminal are electrically connected;

wherein n is a positive integer greater than or equal to 2, and m is a positive integer greater than or equal to 1 and less than or equal to n.

2. A photovoltaic module comprising the junction box of claim 1 and n cell string units, the cell string unit comprising one or two cell strings comprising a plurality of cells connected in series; each of the diodes is connected in anti-parallel with each of the battery strings in one of the battery string units.

3. The photovoltaic module of claim 2, wherein n-3.

4. A method for testing a hot spot temperature of a photovoltaic module, for testing the photovoltaic module according to any one of claims 2 to 3, comprising:

acquiring the maximum power point current of the photovoltaic module under the preset light intensity;

determining the worst cell slice in the photovoltaic assembly;

testing the short-circuit current of the battery string unit where the worst battery piece is located under different shielding areas of the worst battery piece;

determining the severest shielding area of the worst battery piece according to the short-circuit current and the maximum power point current;

determining a hot spot position on the worst battery piece;

shielding the worst battery piece, keeping the hot spot position of the worst battery piece exposed, and keeping the shielded area equal to the severest shielded area;

and exposing the photovoltaic module, and testing to obtain the temperature of the hot spot position as the hot spot temperature of the photovoltaic module.

5. The method of claim 4, wherein the predetermined light intensity is 1000W per square meter.

6. The testing method of claim 4, wherein obtaining the maximum power point current of the photovoltaic module at the preset light intensity comprises:

testing and obtaining a volt-ampere characteristic curve of the photovoltaic module under the preset light intensity;

and determining the maximum power point current according to the volt-ampere characteristic curve.

7. The testing method of claim 4, wherein determining the worst cell in the photovoltaic module comprises:

completely shielding each cell in the photovoltaic module in sequence, and testing to obtain the leakage current of the photovoltaic module after each cell is completely shielded;

and determining the battery piece corresponding to the maximum leakage current as the worst battery piece.

8. The test method of claim 4, wherein testing the short-circuit current of the battery string unit where the worst battery piece is located under different shielding areas of the worst battery piece comprises:

the battery string unit where the worst battery piece is located is a first battery string unit, the battery string units except the first battery string unit are second battery string units, diodes which are reversely connected in parallel with each battery string in the first battery string unit are first diodes, and the diodes which are reversely connected in parallel with each battery string in the second battery string unit are second diodes; opening the switch in parallel with the first diode and closing the switch in parallel with the second diode;

and testing the output current of the photovoltaic module under different shielding areas of the worst battery piece to be used as the short-circuit current of the battery string unit where the worst battery piece is located.

9. The method for testing the photovoltaic module according to claim 8, wherein the step of testing the output current of the photovoltaic module under different shielding areas of the worst cell, as the short-circuit current of the cell string unit where the worst cell is located, comprises the steps of:

sequentially increasing the shielded area of the worst battery piece from the shielded area of the worst battery piece being 0 by taking a preset area as a variable quantity, or sequentially decreasing the shielded area of the worst battery piece from the worst battery piece being completely shielded; after the shielded area of the worst battery piece is increased or reduced each time, testing the output current of the photovoltaic assembly once, and taking the output current as the short-circuit current of the battery string unit where the worst battery piece is located under the corresponding shielded area;

wherein the preset area is 5% of the area of the worst battery piece.

10. The testing method of claim 4, wherein determining the severest shielding area of the worst cell slice according to the short circuit current and the maximum power point current comprises:

determining the short-circuit current with the minimum difference with the maximum power point current as a first short-circuit current, and determining the shielded area of the worst battery piece corresponding to the first short-circuit current as the severest shielded area of the worst battery piece.

11. The testing method of claim 4, wherein determining the hotspot location on the worst cell slice comprises:

and determining the position of the hot spot on the worst battery piece by adopting an infrared detection device.

12. The method for testing according to claim 4, wherein the photovoltaic module is exposed to the sun, and the step of testing the temperature of the hot spot position as the hot spot temperature of the photovoltaic module comprises:

and (3) exposing the photovoltaic module, and testing to obtain the temperature of the hot spot position as the hot spot temperature of the photovoltaic module by adopting a thermocouple or an infrared detection device attached to the hot spot position.

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