CN105655431A - Photovoltaic assembly and method based on optimal allocation of bypass diodes - Google Patents

Abstract

The invention discloses a photovoltaic module and a method for optimizing the distribution of bypass diodes. The photovoltaic module includes several rows of battery strings distributed side by side from top to bottom, connecting ribbons connecting the battery strings in series, respectively connected to the positive output terminal and The positive junction box and the negative junction box at the negative output end, and the positive connection cable and the negative connection cable drawn from the positive junction box and the negative junction box respectively, each row of battery strings includes several solar cells connected in series from left to right; It also includes a bypass diode that short-circuits the faulty battery string when the battery string fails or the solar cells in the battery string are blocked by obstacles; the bypass diodes are unevenly distributed from top to bottom, that is, there is at least one bypass diode The number of battery strings protected in parallel by the diodes is different from the number of battery strings protected in parallel by the remaining bypass diodes. Solve the problems of large power loss, high risk of hot spots, and low reliability of photovoltaic modules due to the shading of cells.

Description

Photovoltaic module and method for optimizing distribution of bypass diodes

technical field

The invention relates to a photovoltaic module and a method for optimizing the distribution of bypass diodes, belonging to the technical field of photovoltaic power generation.

Background technique

In recent years, the solar photovoltaic industry has developed rapidly, and the actual power generation performance of photovoltaic modules has also attracted much attention. In practical applications, the voltage of a single solar cell is low, and it is usually necessary to connect dozens of cells in series through ribbons, and use protective materials and accessories to package them into photovoltaic modules.

At present, photovoltaic modules usually use one or more junction boxes, which are bonded to the back of the solar cell module and have multiple bypass diodes inside. When the photovoltaic module is running normally, the bypass diode is in reverse bias and does not work; when some cells in the solar cell module are shaded, the bypass diode connected in series and parallel with the shaded cells is turned on, thereby avoiding the hot spot effect of the battery Generate high temperature and damage photovoltaic modules. Generally, a bypass diode can protect up to 20-24 cells. We define these 20-24 cells as 1 substring. Usually, a module consists of 3 substrings, as shown in Figure 1.

Figure 1 is a schematic diagram of the connection of bypass diodes for ordinary photovoltaic modules. From Figure 1, it can be seen that the number of series cells in each substring is the same, that is, the number of cells protected by each bypass diode is the same, 24 cells; However, when shading occurs, usually one cell is shaded, and the power of the photovoltaic module will directly lose one-third.

Contents of the invention

The main purpose of the present invention is to overcome the deficiencies in the prior art and provide a photovoltaic module and method with optimized distribution of bypass diodes, which can solve the problem of large power loss of photovoltaic modules and high risk of hot spots due to the blocking of cells. low reliability issues.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A photovoltaic module with optimized distribution of bypass diodes, including several rows of battery strings distributed side by side from top to bottom, connecting ribbons connecting the battery strings in series, positive junction boxes and negative wiring connected to the positive output terminal and negative output terminal respectively box, and the positive connection cable and the negative connection cable drawn from the positive junction box and the negative junction box respectively. Each row of battery strings includes a number of solar cells connected in series from left to right; it also includes protection for battery string failure or battery failure. When the solar cells in the string are blocked by obstacles, the bypass diodes short-circuit the faulty battery strings; the bypass diodes are distributed unevenly from top to bottom, that is, the number of battery strings protected by at least one bypass diode in parallel is different The number of battery strings protected in parallel with the remaining bypass diodes.

The present invention is further set as: the bypass diodes sequentially include a top bypass diode, several middle bypass diodes, and a bottom bypass diode from top to bottom; the top bypass diodes and the bottom bypass diodes are respectively The number of battery strings protected in parallel is less than the number of battery strings protected in parallel by any intermediate bypass diode.

The present invention is further configured as follows: the battery strings from top to bottom are the first row of battery strings, the second row of battery strings, ..., the Nth row of battery strings, N is a natural number; the battery string in the top row is the first row A row of battery strings, the battery string in the bottom row is the Nth row of battery strings; each row of battery strings has 4-12 solar cells, and the maximum number of solar cells protected by each bypass diode in parallel is 30.

Wherein, the top bypass diode is connected in parallel to protect the first row of battery strings, or in parallel to protect the first row of battery strings and the second row of battery strings; the bottom bypass diode is connected in parallel to protect the Nth row of battery strings, or in parallel to protect the Nth row of battery strings. row of battery strings and N-1th row of battery strings; if the number of battery strings protected by any one of the top bypass diode and the bottom bypass diode is two rows, then the middle bypass diode is connected in parallel to protect at least three rows of battery strings; if Both the top bypass diode and the bottom bypass diode are connected in parallel to protect one row of battery strings, and the middle bypass diodes are connected in parallel to protect at least two rows of battery strings.

The present invention is further configured as follows: the battery strings are twelve rows, that is, N=12, and each row of battery strings has 6 solar cells, a total of 72 solar cells; the top bypass diode is connected in parallel to protect the first The first row of battery strings and the second row of battery strings, the bottom bypass diodes are connected in parallel to protect the twelfth row of battery strings and the eleventh row of battery strings; there are two middle bypass diodes, which are respectively connected in parallel to protect the third row of battery strings To the sixth row of battery strings, parallel protection of the seventh row of battery strings to the tenth row of battery strings.

The present invention also provides a method for optimizing distribution of bypass diodes, comprising the following steps:

1) According to the installation angle of the photovoltaic module, combined with the sky anisotropic scattering model and typical shadow distribution, obtain the shading probability of each solar cell in each row of battery strings in the photovoltaic module;

2) Averagely calculate the shaded probability of all solar cells in each row of battery strings to obtain the shaded probability of each row of battery strings;

3) Perform uneven distribution of bypass diodes according to the probability of battery strings being blocked;

For the row of battery strings whose probability of being blocked is greater than the set probability threshold, only one bypass diode is connected in reverse parallel to the current row, or a bypass diode is connected in reverse parallel to two rows of adjacent battery strings;

A bypass diode is connected in antiparallel to at least two rows of the remaining battery strings whose probability of being blocked by the battery string is less than or equal to the set probability threshold.

The method of the present invention is further set to: the step 3) carries out the uneven distribution of the bypass diodes, for the battery strings are twelve rows, and each row of battery strings has 6 solar cells, which is a total of 72 solar cells. The photovoltaic module includes a top bypass diode, two middle bypass diodes, and a bottom bypass diode from top to bottom; the top bypass diode is connected in parallel to protect the first row of battery strings and the second row of battery strings, so The above-mentioned bottom bypass diodes are connected in parallel to protect the twelfth row of battery strings and the eleventh row of battery strings. The tenth row of battery strings.

Compared with prior art, the beneficial effect that the present invention has is:

1. The photovoltaic module with optimized distribution of bypass diodes provided by the present invention adopts the parallel protection design of bypass diodes with uneven distribution, and according to the actual use, the lower end of the photovoltaic module is easier to be blocked, and the middle position is relatively less likely to be blocked. In the case of small probability, the total number of solar cells protected in parallel by the bypass diode near the bottom of the photovoltaic module is small, and the power loss of the photovoltaic module is greatly reduced by blocking one cell at the bottom, thereby solving the problem of photovoltaic modules being blocked by cells. The power loss is large, the risk of hot spots is high, and the reliability is low.

2. The method for optimizing the distribution of bypass diodes provided by the present invention performs uneven distribution of bypass diodes according to the probability of battery strings being blocked, which can not only greatly reduce the power loss of photovoltaic modules and improve power generation performance, but also facilitate the layout of the site Flexible distribution of bypass diodes ensures long-term reliability.

The above content is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly, the present invention will be further described below in conjunction with the accompanying drawings.

Description of drawings

FIG. 1 is a schematic diagram of the connection of bypass diodes of common photovoltaic modules in the prior art;

Fig. 2 is a schematic diagram of the bypass diode connection of the photovoltaic module of the present invention;

Figure 3 is the normal and unshaded current and voltage output curve of a common photovoltaic module;

Figure 4 is the current and voltage output curves after the upper and lower parts of a common photovoltaic module are shaded by one solar cell;

Fig. 5 is the current and voltage output curves after the upper part and the lower part of the photovoltaic module of the present invention are each shaded by one solar cell.

detailed description

Below in conjunction with accompanying drawing of description, the present invention will be further described.

As shown in Figure 2, the present invention provides a photovoltaic module with optimized distribution of bypass diodes, which includes several rows of battery strings 1 distributed side by side from top to bottom, connecting ribbons 2 connecting the battery strings in series in sequence, and connecting them to the positive electrode respectively. The positive junction box (shown in the figure) and the negative junction box (shown in the figure) of the output terminal 3 and the negative output terminal 4, and the positive connection cable 5 and the negative connection cable drawn from the positive junction box and the negative junction box respectively Cable 6, each row of battery strings 1 includes a number of solar cells 11 connected in series from left to right; it also includes a battery that will fail when the battery string 1 fails or the solar cells 11 in the battery string 1 are blocked by obstacles. Bypass diodes short-circuited in series; the bypass diodes are unevenly distributed from top to bottom, that is, the number of battery strings 1 protected in parallel by at least one bypass diode is different from the number of battery strings protected in parallel by the remaining bypass diodes. It should be noted that the maximum number of solar cells protected by parallel connection of each bypass diode is 30 pieces.

As shown in Figure 2, the battery strings 1 are the first row of battery strings, the second row of battery strings, ..., the Nth row of battery strings from top to bottom, and N is a natural number 12; the solar cells of each row of battery strings There are 6 pieces of solar cells, and a total of 72 pieces of 156mm*156mm solar cells are packaged in the module frame 12 to form a photovoltaic module.

The bypass diodes include a top bypass diode 7, two middle bypass diodes 8, and a bottom bypass diode 9 from top to bottom; the top bypass diode 7 is connected in parallel to protect the first row of battery strings and the first row of batteries. For the second row of battery strings, the bottom bypass diode 9 is connected in parallel to protect the twelfth row of battery strings and the eleventh row of battery strings; and the two middle bypass diodes 8 are respectively connected in parallel to protect the third row to the sixth row of battery strings , Parallel protection of the seventh row of battery strings to the tenth row of battery strings. That is, one bypass diode is connected in parallel for every 12 solar cells at the upper and lower ends of the photovoltaic module, and one bypass diode is connected in parallel after every 24 solar cells are connected in series in the middle part.

The electrical performance parameters of the normal photovoltaic module and the optimized photovoltaic module of the present invention are shown in Table 1. The normal and unshielded current and voltage output curves of the ordinary photovoltaic module are shown in Figure 3. The normal photovoltaic module of the present invention is The unshaded current-voltage output curve is basically the same as that in Figure 3.

For ordinary photovoltaic modules, when the upper and lower parts are covered by one solar cell, the electrical performance parameters of ordinary photovoltaic modules are shown in Table 2, and the current and voltage output curves are shown in Figure 4; for the bypass diode distribution of the present invention For the optimized photovoltaic module, when the upper part and the lower part of the photovoltaic module are covered by one solar cell, the electrical performance parameters of the photovoltaic module of the present invention are shown in Table 3, and the current and voltage output curves are shown in Figure 5.

Isc Voc Im Vm Pmax Ploss 8.70 46.00 8.34 38.35 319.84 0.00%

Table 1

Isc Voc Im Vm Pmax Ploss 8.70 45.88 8.01 13.27 106.26 65.41%

Table 2

Isc Voc Im Vm Pmax Ploss 8.70 45.96 8.18 26.34 215.35 31.77%

table 3

In Table 1, Table 2, and Table 3, Isc is the short-circuit current, Voc is the open-circuit voltage, Im is the maximum power point current, Vm is the maximum power point voltage, Pmax is the maximum power, and Ploss is the power loss.

Compared with the ordinary photovoltaic module shown in Figure 1, when the upper part and the lower part are shaded by one solar cell, the power of the photovoltaic module with optimized bypass diode distribution of the present invention as shown in Figure 2 drops to about 32%. The power of ordinary photovoltaic modules is reduced by about 65%. It can be seen that the present invention achieves the purpose of greatly reducing the power loss of the photovoltaic module after the parallel protection of the bypass diodes with uneven distribution is adopted.

The present invention also provides a method for optimizing the distribution of bypass diodes, which is characterized in that it includes the following steps:

1) According to the installation angle of the photovoltaic module, combined with the sky anisotropic scattering model and typical shadow distribution, obtain the shading probability of each solar cell in each row of battery strings in the photovoltaic module;

2) Averagely calculate the shaded probability of all solar cells in each row of battery strings to obtain the shaded probability of each row of battery strings;

3) Perform uneven distribution of bypass diodes according to the probability of battery strings being blocked;

For the row of battery strings whose probability of being blocked is greater than the set probability threshold, only one bypass diode is connected in reverse parallel to the current row, or a bypass diode is connected in reverse parallel to two rows of adjacent battery strings;

A bypass diode is connected in antiparallel to at least two rows of the remaining battery strings whose probability of being blocked by the battery string is less than or equal to the set probability threshold.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (6)

1. the photovoltaic module of a by-pass diode distribution optimization, it is characterized in that: comprise the some row's battery strings distributed side by side, connection welding belt battery strings connected successively from top to bottom, be connected to cathode output end and the positive terminal box of cathode output end and negative pole terminal box and the positive pole tie cable drawn from positive terminal box and negative pole terminal box respectively and negative pole tie cable, each row's battery strings comprises from left and some solar battery sheets that are that connect successively in the right side;

By the by-pass diode of fail battery string short circuit when the solar battery sheet also comprised in protection battery strings generation fault or battery strings is blocked by obstacle; Described by-pass diode adopts uneven distribution from top to bottom, namely have at least a by-pass diode the battery strings different amts of protection in parallel in the residue by-pass diode institute battery strings quantity protected in parallel.

2. the photovoltaic module of a kind of by-pass diode distribution optimization according to claim 1, it is characterised in that: described by-pass diode comprises a top by-pass diode, some intermediate bypass diodes and a bottom bypass diode from top to bottom successively; Described top by-pass diode and bottom bypass diode separately the battery strings quantity of protection in parallel all less than any one intermediate bypass diode institute battery strings quantity protected in parallel.

3. the photovoltaic module of a kind of by-pass diode distribution optimization according to claim 2, it is characterised in that: described battery strings be followed successively by from top to bottom first row's battery strings, second row battery strings ..., N arrange battery strings, N is natural number; The battery strings being positioned at top row is first row's battery strings, and the battery strings being positioned at end row is N row's battery strings; The solar battery sheet often arranging battery strings is 4-12 sheet, and the solar battery sheet upper limit number of each by-pass diode parallel connection protection is 30;

Described top by-pass diode parallel connection protection first row's battery strings, or protection in parallel first row's battery strings and second row battery strings; Described bottom bypass diodes in parallel protects N to arrange battery strings, or protection N in parallel arranges battery strings and N-1 arranges battery strings;

If any one battery strings quantity protected is two rows in top by-pass diode and bottom bypass diode, then intermediate bypass diodes in parallel protection at least three row's battery strings; If top by-pass diode and bottom bypass diode protection one row's battery strings all in parallel, then intermediate bypass diodes in parallel protection at least two row's battery strings.

4. the photovoltaic module of a kind of by-pass diode distribution optimization according to claim 3, it is characterised in that: described battery strings is 12 rows, i.e. N=12, and the solar battery sheet often arranging battery strings is 6, is 72 solar battery sheets altogether;

Described top by-pass diode parallel connection protection first row's battery strings and second row battery strings, described bottom bypass diodes in parallel protection the 12 row's battery strings and the 11 row's battery strings; Described intermediate bypass diode is two, and protection the 3rd row's battery strings in parallel is to the 6th row's battery series and parallel protection the 7th row's battery strings to the tenth row's battery strings respectively.

5. the method for a by-pass diode distribution optimization, it is characterised in that, comprise the following steps:

1) according to photovoltaic module, angle is installed, in conjunction with sky anisotropic scattering model and typical case's shade distribution, obtains the cell piece often arranging each solar battery sheet in battery strings in photovoltaic module from top to bottom and be blocked probability;

2) probability that is blocked by the cell piece often arranging all solar battery sheets in battery strings is averaged calculating, and the battery strings obtaining often arranging battery strings is blocked probability;

3) uneven distribution of by-pass diode is carried out according to the be blocked size of probability of battery strings;

This row's battery strings that the probability that battery strings is blocked is greater than setting probability threshold value only current one is arranged a reverse by-pass diode in parallel or totally two is arranged an oppositely by-pass diode in parallel with adjacent row battery strings;

The probability that battery strings is blocked is less than or equals the residue row battery strings at least two row oppositely by-pass diode in parallel setting probability threshold value.

6. the method for a kind of by-pass diode distribution optimization according to claim 5, it is characterized in that: described step 3) carries out the uneven distribution of by-pass diode, for battery strings be 12 rows, the solar battery sheet of often arranging battery strings be 6 be the photovoltaic module of 72 solar battery sheets altogether, comprise a top by-pass diode, two intermediate bypass diodes and a bottom bypass diode from top to bottom successively;

Described top by-pass diode parallel connection protection first row's battery strings and second row battery strings; described bottom bypass diodes in parallel protection the 12 row's battery strings and the 11 row's battery strings, two intermediate bypass diode difference protection the 3rd row's battery strings in parallel protect the 7th row's battery strings to the tenth row's battery strings to the 6th row's battery series and parallel.