CN219780105U

CN219780105U - Photovoltaic power generation system, fault protection device thereof, combiner box and inverter

Info

Publication number: CN219780105U
Application number: CN202321335945.XU
Authority: CN
Inventors: 潘年安; 张兵; 冯纪归; 丁杰; 张显立
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2023-05-26
Filing date: 2023-05-26
Publication date: 2023-09-29
Anticipated expiration: 2033-05-26
Also published as: DE202024100357U1; CN221227496U

Abstract

The utility model discloses a photovoltaic power generation system, a fault protection device thereof, a combiner box and an inverter. The system includes power conversion unit, N photovoltaic group strings, and the device includes: x positive connection ends and Y negative connection ends which are suitable for connecting N photovoltaic strings, wherein X is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, and when one of X and Y is equal to N, X is not equal to Y; the first end of each pole switch in the multipole linkage switch is correspondingly connected with one connecting end of the X positive connecting ends and the Y negative connecting ends, the second end of each pole switch connected with the positive connecting end is suitable for being connected to the positive input end of the power conversion unit, and each pole switch connected with the negative connecting end is suitable for being connected to the negative input end of the power conversion unit; the multipole ganged switch is configured in an off state in the event of a failure of the photovoltaic power generation system such that at most three of the N photovoltaic strings are connected in parallel. Thus, the safety of the photovoltaic string can be improved.

Description

Photovoltaic power generation system, fault protection device thereof, combiner box and inverter

Technical Field

The utility model relates to the technical field of photovoltaic power generation, in particular to a photovoltaic power generation system, a fault protection device thereof, a combiner box and an inverter.

Background

In a photovoltaic power generation system, a plurality of strings of photovoltaic strings are connected to a power conversion unit through a fault isolation circuit to supply the generated electricity to the power conversion unit through the fault isolation circuit. The fault isolation circuit uses a direct current switch with a breaking function, when a photovoltaic power generation system breaks down, such as a short circuit or reverse connection of a photovoltaic string, the inside of the power conversion unit breaks down, and the like, the direct current switch can be controlled to break so as to enable the photovoltaic string and the power conversion unit to achieve fault isolation. However, in the related art, after the dc switch is turned off, safety of the failed photovoltaic string is affected.

Disclosure of Invention

The present utility model aims to solve at least one of the technical problems in the related art to some extent. Therefore, the utility model aims to provide a photovoltaic power generation system, a fault protection device, a combiner box and an inverter thereof, wherein when the photovoltaic power generation system is in fault, at most three photovoltaic strings in N photovoltaic strings are connected in parallel after a multipolar linkage switch is disconnected, so that the safety of the photovoltaic strings can be improved.

In a first aspect, an embodiment of the present utility model provides a fault protection device for a photovoltaic power generation system, where the photovoltaic power generation system further includes a power conversion unit and N photovoltaic strings, N is an integer greater than or equal to 3, and the fault protection device includes: x positive connection ends and Y negative connection ends which are suitable for connecting N photovoltaic strings, wherein X is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, and when one of X and Y is equal to N, X is not equal to Y; the first end of each pole switch in the multipole linkage switch is correspondingly connected with one connecting end of the X positive connecting ends and the Y negative connecting ends, the second end of each pole switch connected with the positive connecting end is suitable for being connected to the positive input end of the power conversion unit, and each pole switch connected with the negative connecting end is suitable for being connected to the negative input end of the power conversion unit; the multipole linkage switch is configured to be in an off state under the condition that a photovoltaic power generation system fails, so that at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel.

According to the fault protection device of the photovoltaic power generation system, under the condition that the photovoltaic power generation system breaks down, at most three photovoltaic group strings in N photovoltaic group strings are connected in parallel after the multipole linkage switch is disconnected, so that the safety of the photovoltaic group strings can be improved.

According to an embodiment of the present utility model, the fault protection device further comprises: and a control part configured to control a switching tube in the power conversion unit to short-circuit the positive input end and the negative input end of the power conversion unit in case of a failure of the photovoltaic power generation system. Therefore, under the condition that the photovoltaic power generation system breaks down, the switching tube in the power conversion unit is controlled to short-circuit the positive input end and the negative input end of the power conversion unit, so that the current flowing through the multipole linkage switch can be reduced, the safety of the multipole linkage switch when the multipole linkage switch is disconnected is improved, and the multipole linkage switch can break and isolate faults more safely and reliably.

According to one embodiment of the utility model, the number of strings of photovoltaic groups to which each positive connection is adapted to be connected is at most three, and/or the number of strings of photovoltaic groups to which each negative connection is adapted to be connected is at most three. Therefore, after the multipole linkage switch is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, and further protection of the photovoltaic strings is achieved.

According to one embodiment of the utility model, the cathodes of a plurality of strings of photovoltaic groups, which are adapted to be connected to one and the same positive connection, are connected to at least two negative connections, respectively. Therefore, after the multipole linkage switch is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, and further protection of the photovoltaic strings is achieved.

According to one embodiment of the present utility model, when any one positive connection terminal is suitable for connecting more than four photovoltaic strings, at least two negative connection terminals are suitable for connecting the negative poles of the more than four photovoltaic strings, and the number of photovoltaic strings to which the same negative connection terminal is suitable for connecting is at most three. Therefore, after the multipole linkage switch is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, and further protection of the photovoltaic strings is achieved.

According to one embodiment of the present utility model, when any one of the negative connection terminals is suitable for connecting more than four photovoltaic strings, at least two positive connection terminals are suitable for connecting the positive poles of the more than four photovoltaic strings, and the number of the photovoltaic strings to which the same positive connection terminal is suitable for connecting is at most three. Therefore, after the multipole linkage switch is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, and further protection of the photovoltaic strings is achieved.

According to an embodiment of the present utility model, the fault protection device further comprises: the parameter detection part is connected with the control part and is configured to detect at least one of the parameter value of the branch where each photovoltaic group string is located, the parameter value of the branch where each pole switch is located and the parameter value of the direct current bus, so that the control part determines that the photovoltaic power generation system fails according to at least one of the parameter value of the branch where each photovoltaic group string is located, the parameter value of the branch where each pole switch is located and the parameter value of the direct current bus. Therefore, whether the photovoltaic power generation system fails or not can be simply and accurately detected by detecting one or more of the parameter value of the branch where the photovoltaic group string is located, the parameter value of the branch where the pole switch is located and the parameter value of the direct current bus.

According to one embodiment of the utility model, the parameter values include one or more of voltage values, current values, temperature values, and power values. In this way, it is possible to detect whether the photovoltaic power generation system is malfunctioning through various parameter values.

In a second aspect, an embodiment of the present utility model proposes a combiner box, including the foregoing fault protection device, where the fault protection device is configured to divide between N photovoltaic strings and the power conversion unit in the event of a fault in the photovoltaic power generation system, so that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel.

According to the junction box provided by the embodiment of the utility model, under the condition that the photovoltaic power generation system fails, the safety of the photovoltaic group strings can be improved through the parallel connection of at most three photovoltaic group strings in the N photovoltaic group strings after the multipole linkage switch is disconnected.

In a third aspect, an embodiment of the present utility model proposes an inverter including: a power conversion unit including a DC/AC converter; the fault protection device; the power conversion unit is configured to convert direct current output by the N photovoltaic strings and output alternating current through the DC/AC converter, and the fault protection device is configured to divide the N photovoltaic strings from the power conversion unit under the condition that the photovoltaic power generation system breaks down, so that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel.

According to the inverter provided by the embodiment of the utility model, under the condition that the photovoltaic power generation system fails, the safety of the photovoltaic group strings can be improved by connecting at most three photovoltaic group strings in the N photovoltaic group strings in parallel after the multipole linkage switch is disconnected.

According to one embodiment of the utility model, the power conversion unit further comprises a DC/DC converter, the positive input of the DC/DC converter being the positive input of the power conversion unit, the negative input of the DC/DC converter being the negative input of the power conversion unit, the output of the DC/DC converter being connected to the input of the DC/AC converter.

According to one embodiment of the present utility model, when the number of the fault protection devices is plural, the number of the DC/DC converters is plural, the input end of each DC/DC converter is connected to the corresponding multipole linked switch, and the output ends of the plural DC/DC converters are connected in parallel.

In a fourth aspect, an embodiment of the present utility model proposes a photovoltaic power generation system, including the foregoing fault protection device; or the aforementioned junction box; or the inverter described above.

According to the photovoltaic power generation system provided by the embodiment of the utility model, under the condition that the photovoltaic power generation system fails, the safety of the photovoltaic group strings can be improved through the parallel connection of at most three photovoltaic group strings in the N photovoltaic group strings after the multipole linkage switch is disconnected.

Additional aspects and advantages of the utility model will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the utility model.

Drawings

Fig. 1 is a schematic structural diagram of a photovoltaic power generation system in the related art;

FIGS. 2 a-2 b are schematic structural views of a photovoltaic power generation system having three strings of photovoltaic groups according to one embodiment of the present utility model;

3 a-3 b are schematic structural views of a photovoltaic power generation system having four strings of photovoltaic groups according to one embodiment of the present utility model;

FIGS. 4 a-4 b are schematic structural views of a photovoltaic power generation system having five strings of photovoltaic groups according to one embodiment of the present utility model;

FIG. 5 is a schematic diagram of a photovoltaic power generation system having six photovoltaic strings according to one embodiment of the present utility model;

FIG. 6 is a schematic diagram of a photovoltaic power generation system having seven photovoltaic strings according to one embodiment of the present utility model;

FIG. 7 is a schematic diagram of a photovoltaic power generation system having eight photovoltaic strings according to one embodiment of the present utility model;

8 a-8 b are schematic structural views of photovoltaic power generation systems having five photovoltaic strings according to further embodiments of the present utility model;

9 a-9 b are schematic structural views of photovoltaic power generation systems having five strings of photovoltaic groups according to further embodiments of the present utility model;

FIGS. 10 a-10 b are schematic structural views of photovoltaic power generation systems having five strings of photovoltaic groups according to further embodiments of the present utility model;

FIGS. 11 a-11 b are schematic structural views of a photovoltaic power generation system having five photovoltaic strings according to some embodiments of the present utility model;

fig. 12 is a schematic structural view of a junction box according to an embodiment of the present utility model;

Fig. 13 is a schematic structural view of an inverter according to an embodiment of the present utility model;

fig. 14 is a schematic view of an inverter according to another embodiment of the present utility model;

fig. 15 is a schematic structural view of an inverter according to still another embodiment of the present utility model;

fig. 16 is a schematic diagram of a DC/DC converter according to some embodiments of the utility model;

fig. 17 is a schematic diagram of a DC/AC converter according to some embodiments of the utility model.

Detailed Description

Embodiments of the present utility model are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present utility model and should not be construed as limiting the utility model.

Referring to fig. 1, in a photovoltaic power generation system, N photovoltaic strings PV1, PV2, PVN are connected to a power conversion unit through a fault isolation circuit to supply emitted electricity to the power conversion unit through the fault isolation circuit. The fault isolation circuit uses a direct current switch with a breaking function, and the direct current switch can be controlled to break manually or through a control part in the system.

When the photovoltaic power generation system fails, such as short circuit or reverse connection of the photovoltaic string, failure of the power conversion unit, and the like, the direct current switch can be automatically controlled to be disconnected by a manual or control part, so that the photovoltaic string and the power conversion unit can be isolated from each other in a failure mode.

However, in the related art, when a short circuit or a reverse connection fault occurs in the photovoltaic string, the short circuit or the reverse connection current of the branch where the corresponding direct current switch is located is larger, and the direct current switch is disconnected under the larger short circuit or reverse connection current, so that potential safety hazards exist. After the direct current switch is disconnected, if the connection relation of the photovoltaic string is unreasonable, the safety of the failed photovoltaic string is also affected.

Based on the above, the embodiment of the utility model provides a photovoltaic power generation system, a fault protection device, a combiner box and an inverter thereof, when the system is in fault, such as a short circuit or reverse connection fault of a photovoltaic group string, the safety of the multipole linkage switch when the multipole linkage switch is disconnected can be improved by shorting the positive input end and the negative input end of the power conversion unit, so that the multipole linkage switch can break and isolate the fault more safely and reliably; after the multipole linkage switch is disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel, so that the safety of the photovoltaic group strings can be improved.

In order to enable those skilled in the art to better understand the technical solutions of the present utility model, the technical solutions of the embodiments of the present utility model are clearly described below with reference to the accompanying drawings in the embodiments of the present utility model.

The photovoltaic power generation system provided by the embodiment of the utility model can comprise: a power conversion unit and N photovoltaic strings. The fault protection device may include: the power conversion device comprises X positive connection ends, Y negative connection ends and multipole linkage switches, wherein the X positive connection ends and the Y negative connection ends are suitable for being connected with N photovoltaic strings, the first end of each pole switch in the multipole linkage switches is correspondingly connected with one connection end of the X positive connection ends and the Y negative connection ends, the second end of each pole switch connected with the positive connection ends is suitable for being connected with the positive input end of a power conversion unit, the second end of each pole switch connected with the negative connection ends is suitable for being connected with the negative input end of the power conversion unit, N is an integer greater than or equal to 3, X is greater than or equal to 2 and less than or equal to N, Y is greater than or equal to 2 and less than or equal to N, and X is not equal to Y when one of X and Y is equal to N; the multipole linkage switch is configured to be in an off state under the condition that a photovoltaic power generation system fails, so that at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel.

The power conversion unit is capable of converting electricity generated by the photovoltaic string into electricity required by a user. For example, when the photovoltaic power generation system is connected in grid, the power conversion unit can convert direct current emitted by the photovoltaic group string into alternating current commercial power and then be connected into a power grid; when the photovoltaic power generation system directly supplies power to an alternating current load, the power conversion unit can convert direct current emitted by the photovoltaic group string into alternating current required by the alternating current load and provide the alternating current for the alternating current load; when the photovoltaic power generation system directly supplies power to the direct-current load, the power conversion unit can convert direct current generated by the photovoltaic string into direct current required by the direct-current load and provide the direct-current load with the direct-current power. The structure of the power conversion unit is not limited here, as the power conversion unit may be, but is not limited to, a DC/DC converter, a DC/AC converter, as required. Wherein DC refers to direct current, AC refers to alternating current, DC/DC converter refers to direct current-direct current converter, DC/AC converter refers to direct current-alternating current converter.

A multipole ganged switch refers to a switch that includes a plurality of pole switches and that can be ganged, such as a plurality of pole switches that can be turned on or off simultaneously. The positive electrode switch refers to a switch connected with the positive electrode of the photovoltaic string, the negative electrode switch refers to a switch connected with the negative electrode of the photovoltaic string, and the structures, types and the like of the positive electrode switch and the negative electrode switch can be the same or different, that is, the switches can be not distinguished, and can be but not limited to direct current switches such as direct current circuit breakers and the like.

The photovoltaic group string may be formed by connecting a plurality of photovoltaic modules in parallel, for example, a plurality of photovoltaic modules are directly connected in series to form the photovoltaic group string, or a plurality of photovoltaic modules are connected in parallel and then connected in series to form the photovoltaic group string, and the number, parameters and the like of the photovoltaic modules included in the specific photovoltaic group string are not limited herein. In an embodiment of the utility model, the photovoltaic power generation system comprises N photovoltaic strings, wherein N is an integer greater than or equal to 3. It will be appreciated that when n=1 or n=2, even if a short circuit or a reverse connection fault occurs in the photovoltaic string, since the current flowing through the multipole ganged switch is not increased during the short circuit or the reverse connection, the potential safety hazard is small when the multipole ganged switch is turned off, and the safety of the failed photovoltaic string is not affected after the multipole ganged switch is turned off, so in the embodiment of the present utility model, the number of the photovoltaic strings is an integer greater than or equal to 3.

The N photovoltaic group strings can be connected with the multipole linkage switch through X positive connecting ends and Y negative connecting ends, wherein the total number of the pole switches of the multipole linkage switch is the same as the total number of the positive connecting ends and the negative connecting ends, the number of the positive pole switches is the same as the number of the positive connecting ends, and the number of the negative pole switches is the same as the number of the negative connecting ends, namely, the N photovoltaic group strings can be connected with the first ends of the X positive pole switches through the X positive connecting ends and the first ends of the Y negative pole switches through the Y negative connecting ends. The second ends of the X positive switches are also connected with the positive input end of the power conversion unit, and the second ends of the Y negative switches are also connected with the negative input end of the power conversion unit. Wherein, X is less than or equal to 2 and less than or equal to N, Y is less than or equal to 2 and less than or equal to N, when one of X and Y is equal to N, X is not equal to Y, namely, the number of positive connection ends and negative connection ends is not more than the number of photovoltaic strings at maximum, and the number of the positive connection ends and the negative connection ends is not less than two at minimum, and when one of the positive connection ends and the negative connection ends is the number of the photovoltaic strings, the number of the positive connection ends and the negative connection ends is not the same as the number of the photovoltaic strings, so that the number of the pole switches can be reduced to a certain extent.

Further, since at most three photovoltaic strings in the N photovoltaic strings are connected in parallel after the multipole linkage switch is turned off, when X and Y satisfy the above conditions, it is also necessary that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel after the multipole linkage switch is turned off. After the multipole linkage switch is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, so that when one photovoltaic string can bear current output by at most two photovoltaic strings, when the photovoltaic string breaks down, at most two normal photovoltaic strings output current to the photovoltaic string, and at the moment, the current is in a range which can be borne by the broken photovoltaic string, and the photovoltaic string is protected from damage.

Exemplary, case one: a photovoltaic power generation system will be described by taking n=3 as an example.

There are many possibilities for the number of positive and negative connection terminals when n=3, such as y=2 when x=3; alternatively, when x=2, y=2 or 3. At this time, X and Y satisfy: x is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, when one of X and Y is equal to N, X is not equal to Y, and at most two photovoltaic group strings connected with each connecting end can be realized, so that after the multipole linkage switch 20 is disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel.

For example, when x=3 and y=2, referring to fig. 2a, the photovoltaic power generation system includes: 3 photovoltaic strings PV1, PV2 and PV3, and a power conversion unit 10. The fault protection device includes: 3 positive connection terminals X1, X2, and X3, 2 negative connection terminals Y1 and Y2, a multipole linked switch 20, and a control section (not shown), the multipole linked switch 20 including 3 positive electrode switches SX1, SX2, and SX3, and 2 negative electrode switches SY1 and SY2. The positive pole PV1+ of the photovoltaic group string PV1 is connected with the first end of the positive pole switch SX1 through a positive connection end X1, the positive pole PV2+ of the photovoltaic group string PV2 is connected with the first end of the positive pole switch SX2 through a positive connection end X2, and the positive pole PV3+ of the photovoltaic group string PV3 is connected with the first end of the positive pole switch SX3 through a positive connection end X3; the negative pole PV 1-of the photovoltaic group string PV1 and the negative pole PV 2-of the photovoltaic group string PV2 are connected with the first end of the negative pole switch SY1 through a negative connecting end Y1, and the negative pole PV 3-of the photovoltaic group string PV3 is connected with the first end of the negative pole switch SY2 through a negative connecting end Y2; the second ends of the positive pole switches SX1, SX2 and SX3 are connected with the positive input end of the power conversion unit 10; the second terminals of the negative switches SY1 and SY2 are both connected to the negative input of the power conversion unit 10.

It should be noted that fig. 2a is only an exemplary illustration, and that other connection means may be used in this case, for example, PV 1-and PV 3-are connected to the first end of SY1 via Y1, or PV 2-and PV 3-are connected to the first end of SY1 via Y1, etc., which will not be described here.

As another example, when x=2 and y=2, referring to fig. 2b, the photovoltaic power generation system includes: 3 photovoltaic strings PV1, PV2 and PV3, and a power conversion unit 10. The fault protection device includes: 2 positive connection terminals X1 and X2, 2 negative connection terminals Y1 and Y2, a multipole linked switch 20, and a control section (not shown), the multipole linked switch 20 including 2 positive electrode switches SX1 and SX2, and 2 negative electrode switches SY1 and SY2. The positive electrode PV1+ of the photovoltaic group string PV1 and the positive electrode PV2+ of the photovoltaic group string PV2 are connected with the first end of the positive electrode switch SX1 through a positive connecting end X1, and the positive electrode PV3+ of the photovoltaic group string PV3 is connected with the first end of the positive electrode switch SX2 through a positive connecting end X2; the negative pole PV 1-of the photovoltaic group string PV1 and the negative pole PV 2-of the photovoltaic group string PV2 are connected with the first end of the negative pole switch SY1 through a negative connecting end Y1, and the negative pole PV 3-of the photovoltaic group string PV3 is connected with the first end of the negative pole switch SY2 through a negative connecting end Y2; the second ends of the positive electrode switches SX1 and SX2 are connected with the positive input end of the power conversion unit 10; the second terminals of the negative switches SY1 and SY2 are both connected to the negative input of the power conversion unit 10.

It should be noted that fig. 2b is only an exemplary illustration, and other connection methods may be used in this case, for example, that pv1+ and pv3+ are connected to the first end of SX1 through X1, or that pv2+ and pv3+ are connected to the first end of SX1 through X1, etc., which will not be described here.

When x=2 and y=3, the system structure is symmetrical to the structure shown in fig. 2a, and details thereof will not be described here.

And a second case: a photovoltaic power generation system will be described taking n=4 as an example.

When n=4, there are many possibilities of the number of positive connection terminals and the number of negative connection terminals, such as y=3 or 2 when x=4; when x=3 or 2, y=2, 3 or 4. At this time, X and Y satisfy: x is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, when one of X and Y is equal to N, X is not equal to Y, and at most three photovoltaic strings connected with each connecting end can be connected in parallel after the multipole linkage switch 20 is disconnected.

Since there are many cases in the structure of the photovoltaic power generation system in this case, the system structure will not be described here one by one to avoid redundancy, and only the examples shown in fig. 3a and 3b will be described as an example.

And a third case: a photovoltaic power generation system will be described by taking n=5 as an example.

When n=5, there are many possibilities for the number of positive connection terminals and the number of negative connection terminals, such as y=4, 3 or 2 when x=5; when x=4, 3 or 2, y=5, 4, 3 or 2, and when x=2 and y=2, by reasonably setting the connection relationship, it can be satisfied that after the multipole linkage switch 20 is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, for example, when the same positive connection end connects the anodes of four photovoltaic strings, the cathodes of the four photovoltaic strings will be connected through two negative connection ends, and for example, the same positive connection end connects the anodes of three photovoltaic strings at most, and the same negative connection end connects the cathodes of three photovoltaic strings at most. At this time, X and Y satisfy: x is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, when one of X and Y is equal to N, X is not equal to Y, and after the multipole linkage switch 20 is disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel.

Since there are many cases in the structure of the photovoltaic power generation system in this case, the system structure will not be described here one by one to avoid redundancy, and only the examples shown in fig. 4a and 4b will be described as an example.

Case four: a photovoltaic power generation system will be described with n=6 as an example.

When n=6, there are many possibilities for the number of positive connection terminals and the number of negative connection terminals, such as y=5, 4, 3 or 2 when x=6; when x=5, 4, 3 or 2, y=6, 5, 4, 3 or 2, and when x=3 and y=3 or 2, or x=2 and y=3 or 2, by reasonably setting the connection relationship, it can be satisfied that after the multipole linkage switch 20 is turned off, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, for example, when x=3 and y=3, when the same positive connection end connects the anodes of four photovoltaic strings, the cathodes of the four photovoltaic strings will be connected through at least two negative connection ends, and for example, the same positive connection end connects at most the anodes of three photovoltaic strings, and the same negative connection end connects at most the cathodes of three photovoltaic strings. It should be noted that this is only an exemplary illustration, and for other cases, this is not a one-to-one illustration. At this time, X and Y satisfy: x is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, when one of X and Y is equal to N, X is not equal to Y, and after the multipole linkage switch 20 is disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel.

Since there are many cases in the structure of the photovoltaic power generation system in this case, the system structure will not be described here one by one to avoid redundancy, and only the example shown in fig. 5 will be described as an example.

Case five: a photovoltaic power generation system will be described by taking n=7 as an example.

When n=7, there are many possibilities for the number of positive connection terminals and the number of negative connection terminals, such as y=6, 5, 4, 3 or 2 when x=7; when x=6, 5, 4, 3 or 2, y=7, 6, 5, 4, 3 or 2, and when x=4 and y=4, 3 or 2, or when x=3 and y=4, 3 or 2, or when x=2 and y=4, 3 or 2, by reasonably setting the connection relationship, it may be satisfied that after the multipole ganged switch 20 is turned off, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, for example, when x=4 and y=4, when the same positive connection terminal is connected to the positive electrodes of the four photovoltaic strings, the negative electrodes of the four photovoltaic strings will be connected through at least two negative connection terminals, and, for example, the same positive connection terminal is connected to the positive electrodes of the three photovoltaic strings at most, and the same negative connection terminal is connected to the negative electrodes of the three photovoltaic strings at most. It should be noted that this is only an exemplary illustration, and for other cases, this is not a one-to-one illustration. At this time, X and Y satisfy: x is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, when one of X and Y is equal to N, X is not equal to Y, and after the multipole linkage switch 20 is disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel.

Since there are many cases in the structure of the photovoltaic power generation system in this case, the system structure will not be described here one by one to avoid redundancy, and only the example shown in fig. 6 will be described as an example.

Case six: a photovoltaic power generation system will be described with n=8 as an example.

When n=8, there are many possibilities for the number of positive connection terminals and the number of negative connection terminals, such as y=7, 6, 5, 4, 3 or 2 when x=8; when x=7, 6, 5, 4 or 3, y=8, 7, 6, 5, 4, 3 or 2; when x=2, y=8, 7, 6, 5, 4 or 3, and when x=5 and y=5, 4, 3 or 2, or when x=4 and y=5, 4, 3 or 2, or when x=3 and y=5, 4, 3 or 2, or when x=2 and y=5, 4 or 3, by reasonably setting the connection relationship, it is possible to satisfy that after the multipole ganged switch 20 is turned off, there is a parallel connection of at most three photovoltaic strings in the N photovoltaic strings, for example, when x=5 and y=5, when the same positive connection terminal connects the positive poles of four photovoltaic strings, the negative poles of the four photovoltaic strings will be connected through at least two negative connection terminals. It should be noted that this is only an exemplary illustration, and for other cases, this is not a one-to-one illustration. At this time, X and Y satisfy: x is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, when one of X and Y is equal to N, X is not equal to Y, and after the multipole linkage switch 20 is disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel.

Since there are many cases in the structure of the photovoltaic power generation system in this case, the system structure will not be described here one by one to avoid redundancy, and only the example shown in fig. 7 will be described as an example.

It should be noted that, for other cases not listed, reference may be made to the foregoing, and no further description is given here.

In some embodiments, the fault protection device further comprises: and a control part configured to control a switching tube in the power conversion unit to short-circuit the positive input end and the negative input end of the power conversion unit in case of a failure of the photovoltaic power generation system. Therefore, under the condition that the photovoltaic power generation system breaks down, the switching tube in the power conversion unit is controlled to short-circuit the positive input end and the negative input end of the power conversion unit, so that the current flowing through the multipole linkage switch can be reduced, the safety of the multipole linkage switch when the multipole linkage switch is disconnected is improved, and the multipole linkage switch can break and isolate faults more safely and reliably.

The protection principle of the fault protection device will be described below in connection with the foregoing cases one to six.

For case one: for example, referring to fig. 2a, in the case where the photovoltaic power generation system is normal, the photovoltaic group strings PV1, PV2, and PV3 supply the generated electricity to the power conversion unit 10 through the multipole ganged switch 20. In case of a failure of the photovoltaic power generation system, for example, the photovoltaic string PV1 is shorted or reversely connected, referring to (1) of fig. 2a, when the current of the photovoltaic strings PV2 and PV3 flows into the photovoltaic string PV1 in the event of a short circuit, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX1 corresponding to the photovoltaic string PV1 will need to break 2 times the short circuit current of the single photovoltaic string, that is, the sum of the currents of the photovoltaic strings PV2 and PV3, and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will need to break 1 times the short circuit current of the single photovoltaic string, that is, the current of the photovoltaic string PV3, and the multipole ganged switch 20 will need to break 2 times the breaking current of the single photovoltaic string at the maximum; when the positions of the positive electrode PV1+ and the negative electrode PV 1-of the photovoltaic string PV1 are exchanged in reverse connection, because the anti-parallel diode exists in the photovoltaic assembly, the current of the photovoltaic string PV2 and the photovoltaic 3 reversely flows to the photovoltaic string PV1, if the multi-pole linkage switch 20 is directly disconnected at the moment, the positive electrode switch SX1 corresponding to the photovoltaic string PV1 needs to be disconnected by 2 times of the reverse connection current of the single photovoltaic string, namely the sum of the current of the photovoltaic string PV2 and the current of the photovoltaic string PV3, and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 needs to be disconnected by 1 time of the reverse connection current of the single photovoltaic string, namely the current of the photovoltaic string PV3, and the multi-pole linkage switch 20 needs to be disconnected by 2 times of the disconnection current of the single photovoltaic string at the maximum, and meanwhile the disconnection voltage of the single photovoltaic string is also disconnected by 2 times.

If the switching tube Q in the power conversion unit 10 is controlled by the control part at this time according to (2) of fig. 2a, so as to short-circuit the positive input end and the negative input end of the power conversion unit 10, that is, a new short-circuit or reverse-connection channel is formed inside the power conversion unit 10, and as the impedance of the switching tube Q in the channel is smaller than that of the photovoltaic string, most of short-circuit or reverse-connection current can pass through the channel, so that the current flowing through the positive electrode switch SX1 corresponding to the photovoltaic string PV1 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage of the positive electrode switch SX1 corresponding to the failed photovoltaic string PV1 are reduced, at this time, the maximum breaking current of the multipole linkage switch 20 is 1 time the breaking current of the single photovoltaic string, and the maximum breaking voltage at the time of the reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 2 times the breaking current of the single photovoltaic string, and 2 times the breaking voltage of the single photovoltaic string, the maximum breaking current of the multipole linkage switch 20 is effectively reduced, and the maximum breaking current and the maximum breaking voltage of the multipole linkage switch SX1 can be more safely and reliably broken and the multipole linkage switch SX1 and the positive electrode switch and the fault is more reliably broken. The switching tube Q is typically a semiconductor device, including but not limited to an IGBT, a MOSFET, and the like.

When the control part controls the switching tube Q in the power conversion unit 10 to short-circuit the positive input end and the negative input end of the power conversion unit 10, the control part controls the multi-pole linkage switch 20 to be disconnected, so that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, when one photovoltaic string can bear the current output by at most two photovoltaic strings, when the photovoltaic string fails, at most two normal photovoltaic strings output the current to the photovoltaic string, and the current is in the range which the failed photovoltaic string can bear, thereby protecting the photovoltaic string from damage. For example, in the example shown in fig. 2a, after the multipole ganged switch 20 is turned off, there is no parallel connection of the photovoltaic string and thus the photovoltaic string is not damaged.

It should be noted that, the protection principle when the photovoltaic string PV2 is shorted or reversely connected is the same as the protection principle when the photovoltaic string PV1 is shorted or reversely connected, so that redundancy is avoided, and no description is repeated here.

When the photovoltaic string PV3 is shorted or reversely connected, referring to the foregoing principle, it can be known that the current flowing through the positive electrode switch SX3 and the negative electrode switch SY2 corresponding to the photovoltaic string PV3 can be effectively reduced, and the maximum breaking current of the multipole linkage switch 20 is unchanged at this time, but the shorted or reversely connected current and the breaking voltage flowing through the positive electrode switch SX3 and the negative electrode switch SY2 corresponding to the failed photovoltaic string PV3 are reduced, so that the positive electrode switch SX3 and the negative electrode switch SY2 can be disconnected more safely and reliably, and the multipole linkage switch 20 can break and isolate the failure more safely and reliably.

As another example, referring to fig. 2b, in the case where the photovoltaic power generation system is normal, the photovoltaic group strings PV1, PV2, and PV3 supply the generated electricity to the power conversion unit 10 through the multipole ganged switch 20.

In case of a failure of the photovoltaic power generation system, for example, the photovoltaic string PV1 is shorted or reversely connected, referring to (1) of fig. 2b, the currents of the photovoltaic strings PV2 and PV3 flow into the photovoltaic string PV1, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will need to break 1 time of the shorted or reversely connected current of the single photovoltaic string, and the maximum breaking current of the multipole ganged switch 20 will be 1 time of the breaking current of the single photovoltaic string, and when reversely connected, will also break 2 times of the breaking voltage of the single photovoltaic string.

If the switching tube Q in the power conversion unit 10 is controlled by the control part to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10 at this time according to (2) of fig. 2b, the current flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 can be effectively reduced, and although the maximum breaking current of the multipole ganged switch 20 is still 1 times the breaking current of the single photovoltaic string at this time, the short-circuit or reverse-connection current and the breaking voltage flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the failed photovoltaic string PV1 are reduced, so that the positive electrode switch SX1 and the negative electrode switch SY1 can be disconnected more safely and reliably, and the multipole ganged switch 20 can break and isolate the failure more safely and reliably.

After the multipolar linkage switch 20 is disconnected, the photovoltaic string PV1 and the PV2 are connected in parallel, when the photovoltaic string PV1 is short-circuited or reversely connected, the current of the photovoltaic string PV2 flows into the photovoltaic string PV1, and the photovoltaic string PV1 can bear the current output by at most two photovoltaic strings and does not exceed the bearable range of the photovoltaic string PV1, so that the photovoltaic string PV1 is effectively protected from being damaged.

When the photovoltaic string PV3 is shorted or reversely connected, referring to the foregoing principle, it can be known that the current flowing through the positive electrode switch SX2 and the negative electrode switch SY2 corresponding to the photovoltaic string PV3 can be effectively reduced, and the maximum breaking current of the multipole linkage switch 20 is unchanged at this time, but the shorted or reversely connected current and the breaking voltage flowing through the positive electrode switch SX2 and the negative electrode switch SY2 corresponding to the failed photovoltaic string PV3 are reduced, so that the positive electrode switch SX2 and the negative electrode switch SY2 can be disconnected more safely and reliably, and the multipole linkage switch 20 can break and isolate the failure more safely and reliably.

For the protection principle of other system structures with n=3, reference may be made to the foregoing, and no further description is given here.

For case two: for example, referring to fig. 3a, in the case where the photovoltaic power generation system is normal, the photovoltaic strings PV1 to PV4 supply the generated electricity to the power conversion unit 10 through the multipole ganged switch 20.

In case of a failure of the photovoltaic power generation system, for example, the photovoltaic string PV1 is shorted or reversely connected, referring to (1) of fig. 3a, the current of the photovoltaic strings PV2, PV3 and PV4 flows into the photovoltaic string PV1, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX1 corresponding to the photovoltaic string PV1 will need to break 3 times the shorted or reversely connected current of the single photovoltaic string, the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will need to break 2 times the shorted or reversely connected current of the single photovoltaic string, the maximum breaking current of the multipole ganged switch 20 will be 3 times the breaking current of the single photovoltaic string, and at the time of reversely connected, 2 times the breaking voltage of the single photovoltaic string will be required to break.

If the switching tube Q in the power conversion unit 10 is controlled by the control part to short-circuit the positive input end and the negative input end of the power conversion unit 10 according to (2) of fig. 3a, then the current flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the failed photovoltaic string PV1 are reduced, at this time, the maximum breaking current of the multipole linkage switch 20 is 1 time the breaking current of the single photovoltaic string, and the maximum breaking voltage at the time of reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 3 times the breaking current of the single photovoltaic string, and 2 times the breaking voltage of the single photovoltaic string, the maximum breaking current and the maximum breaking voltage of the linkage switch are effectively reduced, and the positive electrode switch SX1 and the negative electrode switch SY1 can be more safely and reliably disconnected, and the multipole linkage switch 20 can be more safely and reliably disconnected.

After the multipole ganged switch 20 is turned off, the photovoltaic string is not connected in parallel, and thus the photovoltaic string is not damaged.

When the photovoltaic string PV3 is shorted or reversely connected, referring to the foregoing principle, it is known that if the multipole ganged switch 20 is directly disconnected, then both the positive switch SX3 and the negative switch SY2 corresponding to the photovoltaic string PV3 will need to break 3 times of the shorted or reversely connected current of the single photovoltaic string, at this time, the maximum breaking current of the multipole ganged switch 20 is 3 times of the breaking current of the single photovoltaic string, and when reversely connected, the breaking voltage of the single photovoltaic string is still 2 times of the breaking voltage of the single photovoltaic string, and if the positive input end and the negative input end of the power conversion unit 10 are shorted, then the currents of the positive switch SX3 and the negative switch SY2 corresponding to the photovoltaic string PV3 can be effectively reduced, the shorted or reversely connected currents and the breaking voltage of the positive switch SX3 and the negative switch SY2 corresponding to the photovoltaic string PV3 are reduced, at this time, the maximum breaking current of the multipole switch 20 is 2 times of the breaking current of the single photovoltaic string, and the maximum breaking voltage of the single photovoltaic string is 1 times of the breaking current of the single photovoltaic string, and the maximum breaking voltage of the single photovoltaic string is more than the single photovoltaic string, and the current of the positive switch SY2 and the negative switch SY2 can be more safely disconnected, and the current of the positive switch and the negative switch SY2 can be more effectively reduced, and the current of the positive switch SX3 and the negative switch is more than the maximum and the breaking voltage of the current of the single photovoltaic string.

It should be noted that, the protection principle when the photovoltaic string PV4 is shorted or reversely connected is the same as the protection principle when the photovoltaic string PV3 is shorted or reversely connected, so that redundancy is avoided, and no description is repeated here.

As another example, referring to fig. 3b, in the case where the photovoltaic power generation system is normal, the photovoltaic group strings PV1 to PV4 supply the generated electricity to the power conversion unit 10 through the multipole linked switch 20.

In case of a failure of the photovoltaic power generation system, for example, the photovoltaic string PV1 is shorted or reversely connected, referring to (1) of fig. 3b, the current of the photovoltaic strings PV2, PV3 and PV4 flows into the photovoltaic string PV1, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX1 corresponding to the photovoltaic string PV1 will need to break 3 times the shorted or reversely connected current of the single photovoltaic string, the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will need to break 2 times the shorted or reversely connected current of the single photovoltaic string, the maximum breaking current of the multipole ganged switch 20 is 3 times the breaking current of the single photovoltaic string at this time, and at the time of reversely connected, the breaking voltage of the single photovoltaic string is also 2 times.

If the switching tube Q in the power conversion unit 10 is controlled by the control part to short-circuit the positive input end and the negative input end of the power conversion unit 10 according to (2) of fig. 3b, then the current flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the failed photovoltaic string PV1 are reduced, at this time, the maximum breaking current of the multipole linkage switch 20 is 2 times the breaking current of the single photovoltaic string, and the maximum breaking voltage at the time of reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 3 times the breaking current of the single photovoltaic string, and 2 times the breaking voltage of the single photovoltaic string, the maximum breaking current and the maximum breaking voltage of the linkage switch are effectively reduced, and the positive electrode switch SX1 and the negative electrode switch SY1 can be more safely and reliably disconnected, and the multipole linkage switch 20 can be more safely and reliably disconnected.

It should be noted that, the protection principle when the photovoltaic strings PV2 to PV4 are short-circuited or reversely connected is the same as the protection principle when the photovoltaic string PV1 is short-circuited or reversely connected, so that redundancy is avoided, and no description is repeated here.

For the protection principle of other system structures with n=4, reference may be made to the foregoing, and no further description is given here.

For case three: for example, referring to fig. 4a, in the case where the photovoltaic power generation system is normal, the photovoltaic group strings PV1 to PV5 supply the generated electricity to the power conversion unit 10 through the multipole ganged switch 20.

In case of a failure of the photovoltaic power generation system, for example, the photovoltaic string PV1 is shorted or reversely connected, referring to (1) of fig. 4a, the current of the photovoltaic strings PV2 to PV5 flows into the photovoltaic string PV1, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will need to break 3 times of the shorted or reversely connected current of the single photovoltaic string, the maximum breaking current of the multipole ganged switch 20 will be 3 times of the breaking current of the single photovoltaic string, and when reversely connected, the breaking voltage of the single photovoltaic string will be 2 times.

If the switching tube Q in the power conversion unit 10 is controlled by the control part to short-circuit the positive input end and the negative input end of the power conversion unit 10 at this time according to (2) of fig. 4a, then the current flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the failed photovoltaic string PV1 are reduced, at this time, the maximum breaking current of the multipole linkage switch 20 is 2 times the breaking current of the single photovoltaic string, and the maximum breaking voltage at the time of reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 3 times the breaking current of the single photovoltaic string, and 2 times the breaking voltage of the single photovoltaic string, the maximum breaking current and the maximum breaking voltage of the linkage switch are effectively reduced, and the positive electrode switch SX1 and the negative electrode switch SY1 can be more safely and reliably disconnected, and the multipole linkage switch 20 can be more safely and reliably disconnected.

After the multipolar linkage switch 20 is disconnected, the photovoltaic strings PV1 and PV2 are connected in parallel, the photovoltaic strings PV3 and PV4 are connected in parallel, and when the photovoltaic strings PV1 are short-circuited or reversely connected, the current of the photovoltaic strings PV2 flows into the photovoltaic strings PV1, and the photovoltaic strings PV1 can bear the current output by at most two photovoltaic strings and do not exceed the bearable range of the photovoltaic strings PV1, so that the photovoltaic strings PV1 can be effectively protected from being damaged.

When the photovoltaic string PV5 is shorted or reversely connected, referring to (3) of fig. 4a, the currents of the photovoltaic strings PV1 to PV4 flow into the photovoltaic string PV5, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX3 and the negative electrode switch SY3 corresponding to the photovoltaic string PV5 will need to break 4 times of the shorted or reversely connected current of the single photovoltaic string, and the maximum breaking current of the multipole ganged switch 20 will be 4 times of the breaking current of the single photovoltaic string, and when reversely connected, the breaking voltage of the single photovoltaic string will be 2 times of the breaking voltage of the single photovoltaic string.

If referring to (4) of fig. 4a, the control part controls the switching tube Q in the power conversion unit 10 to short-circuit the positive input end and the negative input end of the power conversion unit 10, then the current flowing through the positive electrode switch SX3 and the negative electrode switch SY3 corresponding to the photovoltaic string PV5 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage flowing through the positive electrode switch SX3 and the negative electrode switch SY3 corresponding to the failed photovoltaic string PV5 are reduced, at this time, the maximum breaking current of the multipole linkage switch 20 is 2 times the breaking current of the single photovoltaic string, and the maximum breaking voltage at the time of reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 4 times the breaking current of the single photovoltaic string, and 2 times the breaking voltage of the single photovoltaic string, the maximum breaking current and the maximum breaking voltage of the linkage switch are effectively reduced, and the positive electrode switch SX3 and the negative electrode switch SY3 can be more safely and reliably disconnected, and the multipole linkage switch 20 can be more safely and reliably disconnected.

As another example, referring to fig. 4b, in the case where the photovoltaic power generation system is normal, the photovoltaic group strings PV1 to PV5 supply the generated electricity to the power conversion unit 10 through the multipole linked switch 20.

In case of a failure of the photovoltaic power generation system, for example, the photovoltaic string PV1 is shorted or reversely connected, referring to (1) of fig. 4b, the current of the photovoltaic strings PV2 to PV5 flows into the photovoltaic string PV1, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX1 corresponding to the photovoltaic string PV1 will need to break 2 times of the shorted or reversely connected current of the single photovoltaic string, and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will need to break 3 times of the shorted or reversely connected current of the single photovoltaic string, and the maximum breaking current of the multipole ganged switch 20 is 3 times of the breaking current of the single photovoltaic string, and at the time of reversely connected, the breaking voltage of the single photovoltaic string is also 2 times.

If the switching tube Q in the power conversion unit 10 is controlled by the control part at this time according to (2) of fig. 4b, so as to short-circuit the positive input end and the negative input end of the power conversion unit 10, then the current flowing through the negative electrode switch SY1 corresponding to the photovoltaic string PV1 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage flowing through the negative electrode switch SY1 corresponding to the failed photovoltaic string PV1 are reduced, although the current flowing through the positive electrode switch SX1 corresponding to the photovoltaic string PV1 at this time, the maximum breaking current of the multipole linkage switch 20 at this time is 2 times the breaking current of the single photovoltaic string, and the maximum breaking voltage at the time of reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 3 times the breaking current of the single photovoltaic string, and 2 times the breaking voltage of the single photovoltaic string, and the maximum breaking current and the maximum breaking voltage of the multipole linkage switch SY1 are effectively reduced, and the positive electrode switch SX1 and the negative electrode switch SY1 can be more safely and reliably disconnected, and the multipole linkage switch 20 can be more safely and reliably disconnected.

When the photovoltaic string PV5 is shorted or reversely connected, referring to (3) of fig. 4b, the current of the photovoltaic strings PV1 to PV4 flows into the photovoltaic string PV5, if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX2 corresponding to the photovoltaic string PV5 will need to break 3 times of the shorted or reversely connected current of the single photovoltaic string, the negative electrode switch SY3 corresponding to the photovoltaic string PV5 will need to break 4 times of the shorted or reversely connected current of the single photovoltaic string, and the maximum breaking current of the multipole ganged switch 20 is 4 times of the breaking current of the single photovoltaic string at this time, and when reversely connected, the breaking voltage is also 2 times of the breaking voltage of the single photovoltaic string.

If referring to (4) of fig. 4b, the control portion controls the switching tube Q in the power conversion unit 10 to short-circuit the positive input end and the negative input end of the power conversion unit 10, then the current flowing through the positive electrode switch SX2 and the negative electrode switch SY3 corresponding to the photovoltaic string PV5 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage flowing through the positive electrode switch SX2 and the negative electrode switch SY3 corresponding to the failed photovoltaic string PV5 are reduced, at this time, the maximum breaking current of the multipole linkage switch 20 is 3 times the breaking current of the single photovoltaic string, and the maximum breaking voltage at the time of reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 4 times the breaking current of the single photovoltaic string, and 2 times the breaking voltage of the single photovoltaic string, the maximum breaking current and the breaking voltage of the multipole linkage switch are effectively reduced, and the positive electrode switch SX2 and the negative electrode switch SY3 can be more safely and reliably disconnected, and the multipole linkage switch 20 can be more safely and reliably disconnected from the failure.

For case four: for example, referring to fig. 5, in the case where the photovoltaic power generation system is normal, the photovoltaic group strings PV1 to PV6 supply the generated electricity to the power conversion unit 10 through the multipole linked switch 20.

In the case where a failure occurs in the photovoltaic power generation system, for example, the photovoltaic string PV1 is shorted or reversely connected, referring to (1) of fig. 5, the current of the photovoltaic strings PV2 to PV6 flows into the photovoltaic string PV1, and if the multipole ganged switch 20 is directly turned off at this time, the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will need to break 4 times the shorted or reversely connected current of the single photovoltaic string, and the maximum breaking current of the multipole ganged switch 20 will be 4 times the breaking current of the single photovoltaic string, and when reversely connected, will also break 2 times the breaking voltage of the single photovoltaic string.

If the switching tube Q in the power conversion unit 10 is controlled by the control portion to short-circuit the positive input end and the negative input end of the power conversion unit 10 at this time according to (2) of fig. 5, the current flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 can be effectively reduced, the short-circuit or reverse-connection current and the breaking voltage flowing through the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the failed photovoltaic string PV1 can be reduced, the maximum breaking current of the multipole linkage switch 20 is 2 times the breaking current of the single photovoltaic string at this time, and the maximum breaking voltage at the time of reverse connection is 1 time the breaking voltage of the single photovoltaic string, compared with 4 times the breaking current of the single photovoltaic string and 2 times the breaking voltage of the single photovoltaic string, the maximum breaking current and the breaking voltage of the multipole linkage switch are effectively reduced, and the positive electrode switch SX1 and the negative electrode switch SY1 can be safely and reliably disconnected, and the multipole linkage switch 20 can be safely and reliably disconnected.

After the multipolar linkage switch 20 is disconnected, the photovoltaic strings PV1 and PV2 are connected in parallel, the photovoltaic strings PV3 and PV4 are connected in parallel, and the photovoltaic strings PV5 and PV6 are connected in parallel, when the photovoltaic strings PV1 are short-circuited or reversely connected, the current of the photovoltaic strings PV2 flows into the photovoltaic strings PV1, and the photovoltaic strings PV1 can bear the current output by at most two photovoltaic strings and do not exceed the bearable range of the photovoltaic strings PV1, so that the photovoltaic strings PV1 can be effectively protected from being damaged.

It should be noted that, the protection principle when the photovoltaic strings PV2 to PV6 are short-circuited or reversely connected is the same as the protection principle when the photovoltaic string PV1 is short-circuited or reversely connected, so that redundancy is avoided, and no description is repeated here.

For case five: for example, referring to fig. 6, the protection principle of the system is the same as that of the system shown in fig. 4 a. Compared with fig. 4a, when the photovoltaic string is short-circuited or reversely connected, the positive electrode switch and the negative electrode switch corresponding to the failed photovoltaic string need to bear larger breaking current.

For example, if the multipole ganged switch 20 is directly turned off when the photovoltaic string PV1 is shorted or reversely connected, the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will each need to break 5 times of the shorted or reversely connected current of the single photovoltaic string, which obviously puts higher demands on the breaking capacity of the positive electrode switch.

For another example, when the photovoltaic string PV7 is shorted or reversely connected, if the multipole linkage switch 20 is directly turned off, the positive electrode switch SX4 and the negative electrode switch SY4 corresponding to the photovoltaic string PV7 will both need to break 6 times of the shorted or reversely connected current of the single photovoltaic string, and obviously, a higher requirement is put on the breaking capacity of the positive electrode switch.

And the switching tube Q of the power conversion unit 10 is controlled to be conducted through the control part so as to short-circuit the positive input end and the negative input end of the power conversion unit 10, so that the maximum breaking current of the multipole linkage switch 20 can be reduced, and the multipole linkage switch 20 can break and isolate faults more safely and reliably.

For case six: for example, referring to fig. 7, the protection principle of the system is the same as that of the system shown in fig. 5. Compared with fig. 5, when the photovoltaic string is short-circuited or reversely connected, the positive electrode switch and the negative electrode switch corresponding to the failed photovoltaic string need to bear larger breaking current.

For example, if the multipole ganged switch 20 is directly turned off when the photovoltaic string PV1 is shorted or reversely connected, the positive electrode switch SX1 and the negative electrode switch SY1 corresponding to the photovoltaic string PV1 will each need to break 6 times of the shorted or reversely connected current of the single photovoltaic string, which obviously puts higher demands on the breaking capacity of the positive electrode switch.

In the above embodiment, under the condition that the photovoltaic power generation system fails, by controlling the switching tube in the power conversion unit to short-circuit the positive input end and the negative input end of the power conversion unit, the current flowing through the multipole linkage switch can be reduced, the safety of the multipole linkage switch when the multipole linkage switch is disconnected is improved, and the multipole linkage switch can break and isolate the failure more safely and reliably; after the multipole linkage switch is controlled to be disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel, so that the photovoltaic group strings can be prevented from being damaged.

In some embodiments, the number of photovoltaic strings to which each positive connection is adapted to connect is at most three, and/or the number of photovoltaic strings to which each negative connection is adapted to connect is at most three. Therefore, after the multipole linkage switch 20 is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, and further protection of the photovoltaic strings is achieved.

Specifically, when the number of photovoltaic strings connected to each positive connection terminal is at most three, even if the number of photovoltaic strings connected to the negative connection terminal is four or more, since the parallel connection of the photovoltaic strings requires the corresponding parallel connection of the positive and negative poles of the photovoltaic strings, when the number of photovoltaic strings connected to each positive connection terminal is limited to at most three, it is possible to cause the parallel connection of at most three photovoltaic strings among the N photovoltaic strings after the disconnection of the multipole link switch 20.

For example, referring to fig. 8a, for example, positive connection terminal X1 connects three photovoltaic string PV1, PV2 and PV3, positive connection terminal X2 connects one photovoltaic string PV4, positive connection terminal X3 connects one photovoltaic string PV5, i.e. the number of photovoltaic string connected by each positive connection terminal is not more than three; meanwhile, the negative connection end Y1 is connected with four photovoltaic group strings PV1, PV2, PV3 and PV4, and the negative connection end Y2 is connected with one photovoltaic group string PV5. After the multipole linkage switch 20 is disconnected, only the photovoltaic strings PV1, PV2 and PV3 are connected in parallel at this time due to the limitation of the number of the photovoltaic strings connected by the positive connection end X1, so that it is satisfied that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel after the multipole linkage switch 20 is disconnected.

For another example, referring to fig. 8b, the positive connection terminal X1 connects two photovoltaic strings PV1 and PV2, the positive connection terminal X2 connects two photovoltaic strings PV3 and PV4, and the positive connection terminal X3 connects one photovoltaic string PV5, i.e. the number of photovoltaic strings connected by each positive connection terminal is not more than three; meanwhile, the negative connection end Y1 is connected with four photovoltaic group strings PV1, PV2, PV3 and PV4, and the negative connection end Y2 is connected with one photovoltaic group string PV5. After the multipole linkage switch 20 is disconnected, due to the limitation of the number of the photovoltaic strings connected by the positive connection end X1, at the moment, the photovoltaic strings PV1 and PV2 are connected in parallel, and the condition that at most three photovoltaic strings in N photovoltaic strings are connected in parallel after the multipole linkage switch 20 is disconnected is satisfied.

It should be noted that, for other cases, reference may be made to the foregoing, and detailed descriptions thereof are omitted herein.

Similarly, under the condition that the number of the photovoltaic group strings connected at each negative connection end is at most three, and under the condition that the number of the photovoltaic group strings connected at each positive connection end is at most three and the number of the photovoltaic group strings connected at each negative connection end is at most three, the parallel connection of at most three photovoltaic group strings in the N photovoltaic group strings after the multipole linkage switch 20 is disconnected can be satisfied, and details are not repeated here.

In the above embodiment, the number of the photovoltaic strings connected to each connection end is limited, so that it is beneficial to realize that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel after the multipole linkage switch is disconnected, and further realize protection of the photovoltaic strings.

Further, in the case of limiting the number of photovoltaic strings connected by each connection terminal, in some embodiments, the cathodes of a plurality of photovoltaic strings, to which the same positive connection terminal is adapted to be connected, are respectively connected to at least two negative connection terminals. In this way, the number of parallel photovoltaic strings in the N photovoltaic strings can be reduced after the multipole linkage switch 20 is turned off, which is beneficial to realizing that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel after the multipole linkage switch is turned off.

Specifically, in some cases, the same positive connection end may connect a plurality of photovoltaic strings, such as two, three or more, at this time, the cathodes of the plurality of photovoltaic strings connected to the positive connection end may be split and connected to the two or more negative connection ends, and since the parallel connection of the photovoltaic strings requires that the anodes and cathodes of the photovoltaic strings are correspondingly connected in parallel, when the cathodes of the plurality of photovoltaic strings connected to the same positive connection end are split and connected to different negative connection ends, the parallel photovoltaic strings after the disconnection of the multipole linkage switch 20 may be reduced.

Illustratively, referring to fig. 9a, positive connection X1 connects three photovoltaic strings PV1, PV2, and PV3, while the negative poles of photovoltaic strings PV1 and PV2 are connected to negative connection Y1 and the negative pole of photovoltaic string PV3 is connected to negative connection Y2. After the multipole linkage switch 20 is turned off, since the cathodes of two photovoltaic strings PV1 and PV2 of the three photovoltaic strings connected to the positive connection terminal X1 are connected to the negative connection terminal Y1, and the cathode of one photovoltaic string PV3 is connected to the negative connection terminal Y2, only the photovoltaic strings PV1 and PV2 are connected in parallel at this time, and the number of parallel photovoltaic modules is reduced compared with that before the disconnection. Thus, after the multipole linkage switch 20 is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, the current flowing into the failed photovoltaic string is further reduced, and the safety of the photovoltaic string is improved.

For another example, referring to fig. 9b, positive connection terminal X1 connects four photovoltaic string PV1, PV2, PV3, and PV4, while the negative poles of photovoltaic string PV1 and PV2 are connected to negative connection terminal Y1, and the negative poles of photovoltaic string PV3 and PV4 are connected to negative connection terminal Y2. After the multipole linkage switch 20 is disconnected, since the cathodes of two photovoltaic strings PV1 and PV2 in the four photovoltaic strings connected with the positive connection end X1 are connected with the negative connection end Y1, and the cathodes of two photovoltaic strings PV3 and PV4 are connected with the negative connection end Y2, the photovoltaic strings PV1 and PV2 are connected in parallel, and the photovoltaic strings PV3 and PV4 are connected in parallel, compared with the number of parallel photovoltaic components before being split, the number of parallel photovoltaic components is reduced, and the condition that after the multipole linkage switch 20 is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel is satisfied.

In the above embodiment, the cathodes of the plurality of photovoltaic strings connected by the same positive connection end are respectively connected with at least two negative connection ends, which is favorable for realizing that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel after the multipole linkage switch is disconnected, thereby realizing the protection of the photovoltaic strings.

In some embodiments, when the number of photovoltaic strings to which any one positive connection end is adapted to connect is four or more, at least two negative connection ends are adapted to connect the negative poles of the four or more photovoltaic strings, and the number of photovoltaic strings to which the same negative connection end is adapted to connect is at most three.

Specifically, since the parallel connection of the photovoltaic strings requires that the positive electrodes and the negative electrodes of the photovoltaic strings are correspondingly connected in parallel, when the number of the photovoltaic strings connected to any one positive connection end is too large, for example, four or more, the connection of the photovoltaic strings can be limited by the negative connection ends, for example, at least two negative connection ends are connected to the photovoltaic strings connected to the same positive connection end, and the number of the photovoltaic strings connected to the same negative connection end is at most three, so that after the multipole linkage switch 20 is turned off, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel.

Illustratively, referring to fig. 10a, positive connection X1 connects four photovoltaic string PV1, PV2, PV3, and PV4, while the negative poles of photovoltaic string PV1, PV2, and PV3 are connected to negative connection Y1, and the negative pole of photovoltaic string PV4 is connected to negative connection Y2. After the multipole linkage switch 20 is turned off, since the cathodes of three photovoltaic strings PV1, PV2 and PV3 of the four photovoltaic strings connected to the positive connection terminal X1 are connected to the negative connection terminal Y1, and the cathode of one photovoltaic string PV4 is connected to the negative connection terminal Y2, the photovoltaic strings PV1, PV2 and PV3 are connected in parallel, so that after the multipole linkage switch 20 is turned off, at most three photovoltaic strings of the N photovoltaic strings are connected in parallel.

As another example, referring to fig. 10b, positive connection X1 connects five photovoltaic string PV1, PV2, PV3, PV4, and PV5, while the negative pole of each photovoltaic string is connected to one negative connection. After the multipole linkage switch 20 is disconnected, the cathodes of the five photovoltaic group strings PV1, PV2, PV3, PV4 and PV5 connected with the positive connection end X1 are respectively connected with different negative connection ends, so that no photovoltaic group string is connected in parallel at this time, and it is satisfied that at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel after the multipole linkage switch 20 is disconnected.

Similarly, in some embodiments, when the number of the photovoltaic strings to which any one negative connection end is suitable is more than four, at least two positive connection ends are suitable for connecting anodes of the photovoltaic strings to which the four positive connection ends are suitable, and the number of the photovoltaic strings to which the same positive connection end is suitable for being connected is at most three, which is also beneficial to realizing that after the multipole linkage switch is disconnected, at most three photovoltaic strings in the N photovoltaic strings are connected in parallel, so as to realize protection of the photovoltaic strings.

In the above embodiment, when the number of the photovoltaic strings to which any one positive connection end is suitable for connection is more than four, the photovoltaic strings to which the negative connection end is connected are limited; or when the number of the photovoltaic group strings of which any negative connecting end is suitable for being connected is more than four, the limitation of the photovoltaic group strings connected by the positive connecting end is beneficial to realizing that at most three photovoltaic group strings in N photovoltaic group strings are connected in parallel after the multipole linkage switch is disconnected, so that the protection of the photovoltaic group strings is realized.

In some embodiments, the fault protection device further comprises: and the parameter detection part is configured to detect at least one of the parameter value of the branch circuit where each photovoltaic group string is located, the parameter value of the branch circuit where each pole switch is located and the parameter value of the direct current bus, so that the control part detects that the photovoltaic power generation system fails according to at least one of the parameter value of the branch circuit where each photovoltaic group string is located, the parameter value of the branch circuit where each pole switch is located and the parameter value of the direct current bus.

It should be noted that the fault may include a short circuit fault or a reverse connection fault. The parameter values may include a voltage value, a current value, a temperature value, or a power value, etc., and for example, whether a short circuit or a reverse connection fault, etc., occurs in the photovoltaic power generation system may be determined based on the current value, the temperature value, the power value, etc. of the branch where each photovoltaic string is located; for another example, whether a short circuit or a reverse connection fault occurs in the photovoltaic power generation system or not can be determined based on a current value, a temperature value, a power value or the like of a branch where each pole switch is located; for another example, whether a short circuit or a reverse connection failure occurs in the photovoltaic power generation system may be determined based on a voltage value, a current value, a temperature value, or the like of the dc bus.

For example, in the operation process of the photovoltaic power generation system, the parameter value, such as the current value, of the branch where each photovoltaic string is located may be obtained in real time through the parameter detecting part, and under normal conditions, the current value of the branch where each photovoltaic string is located is the output current when the photovoltaic string is operating normally, and when the photovoltaic string is shorted or reversely connected, the output currents of other photovoltaic strings will reversely flow to the failed photovoltaic string, resulting in the increase of the current value of the failed photovoltaic string, and meanwhile, the current is reversely flowing, so that whether the photovoltaic power generation system fails or not can be determined simply and accurately based on the current value of the failed photovoltaic string.

For example, referring to (1) of fig. 11b, under normal conditions, the current value of the branch where each photovoltaic string is located is the output current when the photovoltaic string works normally, and when the photovoltaic string PV1 is shorted or reversely connected, referring to (2) of fig. 11b, the output currents of the photovoltaic strings PV2 to PV5 are reversely poured into the photovoltaic string PV1, so that the current of the branch where the photovoltaic string PV1 is located is increased to 4 times of the shorted or reversely connected current of the single photovoltaic string, and the current direction is opposite to that of the normal state, so that the current photovoltaic power generation system can be determined that there is a short circuit or reversely connected fault based on the detected current value of the branch where the photovoltaic string PV1 is located.

For another example, in the working process of the photovoltaic power generation system, the parameter value such as the current value of the branch where each pole switch is located can be obtained in real time through the parameter detection part, under normal conditions, the current value of the branch where each pole switch is located is the sum of the output current or the output current of the photovoltaic group string connected with the branch, and when the photovoltaic group string is in short circuit or reverse connection, the current of the branch where the corresponding pole switch is located is possibly increased and reverse, so that whether the photovoltaic power generation system fails can be simply and accurately determined based on the current value of the pole switch.

For example, referring to (1) of fig. 11b, under normal conditions, the current value of the branch where the positive electrode switch SX1 and the negative electrode switch SY1 are located is the sum of the output currents of the photovoltaic strings PV1 and PV2, the current value of the branch where the positive electrode switch SX2 and the negative electrode switch SY2 are located is the sum of the output currents of the photovoltaic strings PV3 and PV4, and when the photovoltaic string PV1 is shorted or reversed, referring to (2) of fig. 11b, the current value of the branch where the positive electrode switch SX1 and the negative electrode switch SY1 are located is the sum of the output currents of the photovoltaic strings PV3, PV4 and PV5, and the current direction is opposite to that of the normal, so that it can be determined that there is a short circuit or reverse fault in the current photovoltaic power generation system based on the detected current value of the branch where the positive electrode switch SX1 or the negative electrode switch SY1 is located.

For example, in the working process of the photovoltaic power generation system, the current value of the direct current bus can be obtained in real time through the parameter detection part, under normal conditions, the current value of the direct current bus is the sum of the output currents of the N photovoltaic group strings, and when the photovoltaic group strings are in short circuit or reverse connection, little current flows through the direct current bus, so that whether the photovoltaic power generation system fails can be simply and accurately determined based on the current value of the direct current bus.

For example, referring to (1) of fig. 11b, the current value of the dc bus is normally the sum of the output currents of 5 photovoltaic strings, and when the photovoltaic string PV1 is shorted or reversed, referring to (2) of fig. 11b, the output currents of the photovoltaic strings PV2 to PV5 will be reversed to the photovoltaic string PV1 through the multipole ganged switch 20 with little current flowing through the dc bus, so that it can be determined that there is a short circuit or reversed fault in the current photovoltaic power generation system based on the detected current value of the dc bus.

In the above embodiment, by detecting one or more of the parameter value of the branch where the photovoltaic string is located, the parameter value of the branch where the pole switch is located, and the parameter value of the dc bus, whether the photovoltaic power generation system fails or not can be simply and accurately detected, and the detection modes are various.

In some embodiments, the parameter detecting portion includes at least one of a first current sensor and a second current sensor, wherein the first current sensor is configured to detect first current information of a branch where any one of the photovoltaic strings is located, and send the first current information to the control portion; the second current sensor is configured to detect second current information of a branch where any one of the pole switches is located, and send the second current information to the control section. Any reference herein is to the sensors provided on the respective branches without distinction.

For example, referring to fig. 11 a-11 b, a first current sensor 31 may be disposed on a branch where each photovoltaic string is located, specifically, a first current sensor 31 may be disposed on an anode of each photovoltaic string, current information of the branch where the corresponding photovoltaic string is located is obtained through the first current sensor 31, and may be recorded as first current information, including a current value and a current direction, and the first current information is sent to the control portion.

Or, a second current sensor 32 is disposed on a branch where each pole switch is located, specifically, the second current sensor 32 may be disposed on a branch where each positive pole switch is located, current information of the branch where the corresponding pole switch is located is obtained through the second current sensor 32, and is recorded as second current information, which may include a current value and a current direction, and the second current information is sent to the control part.

Or, a first current sensor 31 is arranged on a branch where each photovoltaic string is located, a second current sensor 32 is arranged on a branch where each pole switch is located, and the first current information and the second current information are acquired through the first current sensor 31 and the second current sensor 32 and sent to the control part.

Further, the control part is further configured to detect that the photovoltaic power generation system fails when the current direction of the branch where the photovoltaic group string is located is determined to be opposite to the set direction according to the first current information; or detecting that the photovoltaic power generation system fails when the current direction of the branch where the pole switch is located is opposite to the set direction according to the second current information; or detecting that the photovoltaic power generation system fails when the current direction of the branch circuit where the photovoltaic group string is located is opposite to the set direction according to the first current information and the current direction of the branch circuit where the pole switch corresponding to the photovoltaic group string is located is opposite to the set direction according to the second current information.

That is, the control portion may determine whether the photovoltaic power generation system fails based on the current direction of the branch in which the photovoltaic string is located, the current direction of the branch in which the pole switch is located, the current direction of the branch in which the photovoltaic string is located, and the current direction of the branch in which the pole switch is located.

For example, referring to (1) of fig. 11b, under normal conditions, the current direction of the branch where each photovoltaic string is located and the current direction of the branch where each pole switch is located are as indicated by the arrow direction in the figure, and when the photovoltaic string PV1 is shorted or reversely connected, referring to (2) of fig. 11b, the output currents of the photovoltaic strings PV2 to PV5 are reversely fed to the photovoltaic string PV1, so that the current direction of the branch where the photovoltaic string PV1 is located and the current direction of the branch where the positive pole switch SX1 and the negative pole switch SY1 corresponding to the photovoltaic string PV1 are located are opposite to each other than normal, therefore, when the current direction of the branch where the photovoltaic string PV1 is determined to be opposite to the set direction based on the first current information, or the current direction of the branch where the positive pole switch SX1 is determined to be opposite to the set direction based on the second current information is determined based on the first current information, the system is determined to be failed to generate electricity when the current direction of the branch where the positive pole switch SX1 is determined to be opposite to the set direction is determined to be set based on the second current information is determined.

In the above embodiment, based on the detected current direction, whether the photovoltaic power generation system fails or not can be simply and accurately detected.

Further, the control part is further configured to detect that the photovoltaic power generation system fails when the absolute value of the current of the branch where the photovoltaic group string is located is determined to be greater than a first preset current threshold according to the first current information; or detecting that the photovoltaic power generation system fails when the absolute value of the current of the branch where the pole switch is located is larger than a second preset current threshold value according to the second current information; or detecting that the photovoltaic power generation system fails when the absolute value of the current of the branch where the photovoltaic group string is located is determined to be larger than a first preset current threshold according to the first current information and the absolute value of the current of the branch where the pole switch corresponding to the photovoltaic group string is determined to be larger than a second preset current threshold according to the second current information.

That is, the control portion may determine whether the photovoltaic power generation system fails based on the current level of the branch where the photovoltaic string is located, the current level of the branch where the pole switch is located, the current level of the branch where the photovoltaic string is located, and the current level of the branch where the pole switch is located.

For example, referring to fig. 11b (1), under normal conditions, the current value of the branch where each photovoltaic string is located is the output current of the photovoltaic string when the photovoltaic string is operating normally, the current value of the branch where the positive switch SX1 is located is the sum of the output currents of the photovoltaic strings PV1 and PV2, the current value of the branch where the positive switch SX2 is located is the sum of the output currents of the photovoltaic strings PV3 and PV4, and the current value of the branch where the positive switch SX3 is located is the output current of the photovoltaic string PV 5.

When the photovoltaic string PV1 is shorted or reversely connected, referring to (2) of fig. 11b, the output current of the photovoltaic strings PV2 to PV5 is reversely fed to the photovoltaic string PV1, so that the current of the branch where the photovoltaic string PV1 is located is increased to 4 times the shorted or reversely connected current of the single photovoltaic string, the current value of the branch where the positive switch SX1 is located is the sum of the output currents of the photovoltaic strings PV3, PV4 and PV5, and the current value is increased, therefore, when the absolute value of the current of the branch where the photovoltaic string PV1 is determined to be greater than the first preset current threshold based on the first current value, or the absolute value of the current of the branch where the positive switch SX1 is determined to be greater than the second preset current threshold based on the second current information, or the absolute value of the current of the branch where the photovoltaic string PV1 is determined to be greater than the first preset current threshold based on the first current value, the photovoltaic power generation system is determined to be failed based on the second current information.

In the above embodiment, based on the detected current, whether the photovoltaic power generation system fails or not can be simply and accurately detected.

In some embodiments, the parameter detecting section further includes a first voltage sensor configured to detect a voltage value of the dc bus and transmit the voltage value of the dc bus to the control section.

For example, referring to fig. 11a to 11b, a first voltage sensor 33 may be disposed on the dc bus, and specifically, the first voltage sensor 33 may be disposed between the positive input terminal and the negative input terminal of the power conversion unit 10, and the voltage value of the dc bus may be detected by the first voltage sensor 33 and sent to the control unit.

Further, the control part is further configured to detect that the photovoltaic power generation system fails when the voltage of the direct current bus is smaller than a first preset voltage threshold.

That is, the control section may determine whether the photovoltaic power generation system is malfunctioning based on the voltage magnitude of the dc bus.

For example, referring to (1) of fig. 11b, the voltage of the dc bus is normally the voltage after the series-parallel connection of 5 photovoltaic strings, and when the photovoltaic string PV1 is shorted or reversely connected, referring to (2) of fig. 11b, the output currents of the photovoltaic strings PV2 to PV5 will be reversely fed to the photovoltaic string PV1 through the multipole ganged switch 20, and little current flows through the dc bus, and the voltage of the dc bus is small, so that it is determined that the photovoltaic power generation system fails when it is determined that the voltage of the dc bus is less than the first preset voltage threshold.

In the above embodiment, based on the detected voltage, whether the photovoltaic power generation system fails or not can be simply and accurately detected.

Further, the control part is further configured to detect that the photovoltaic power generation system fails when it is determined according to the first current information that the absolute value of the current of the branch where the photovoltaic string is located is greater than a first preset current threshold value and the voltage of the direct current bus is less than a first preset voltage threshold value; or detecting that the photovoltaic power generation system breaks down when the absolute value of the current of the branch where the pole switch is located is determined to be larger than a second preset current threshold value and the voltage of the direct current bus is smaller than a first preset voltage threshold value according to the second current information.

That is, the control unit may determine whether the photovoltaic power generation system has failed based on the current level of the branch in which the photovoltaic string is located and the voltage level of the dc bus, or based on the current level of the branch in which the pole switch is located and the voltage level of the dc bus.

For example, referring to (1) of fig. 11b, under normal conditions, the current value of the branch where each photovoltaic string is located is the output current of the photovoltaic string when the photovoltaic string is operating normally, the current value of the branch where the positive switch SX1 is located is the sum of the output currents of the photovoltaic strings PV1 and PV2, the current value of the branch where the positive switch SX2 is located is the sum of the output currents of the photovoltaic strings PV3 and PV4, the current value of the branch where the positive switch SX3 is located is the output current of the photovoltaic string PV5, and the voltage of the dc bus is the voltage after the parallel connection of the 5 photovoltaic strings.

When the photovoltaic string PV1 is shorted or reversely connected, referring to (2) of fig. 11b, the output current of the photovoltaic strings PV2 to PV5 will reversely sink to the photovoltaic string PV1, so that the current of the branch where the photovoltaic string PV1 is located is increased to 4 times the shorted or reversely connected current of the single photovoltaic string, the current value of the branch where the positive switch SX1 is located is the sum of the output currents of the photovoltaic strings PV3, PV4 and PV5, the current value is increased, but little current flows through the dc bus, and the voltage of the dc bus is small, so that when it is determined based on the first current information that the absolute value of the branch where the photovoltaic string PV1 is located is greater than the first preset current threshold and the voltage of the dc bus is less than the first preset voltage threshold, or when it is determined based on the second current information that the absolute value of the branch where the positive switch SX1 is located is greater than the second preset current threshold and the voltage of the dc bus is less than the first preset voltage threshold, it is determined that the photovoltaic power generation system fails.

In the above embodiment, based on the detected current and voltage, whether the photovoltaic power generation system fails or not can be simply and accurately detected.

In some embodiments, the parameter detecting section further includes a third current sensor configured to detect current information of the dc bus and transmit the current information of the dc bus to the control section.

For example, referring to fig. 11a to 11b, a third current sensor 34 may be disposed on the dc bus, and specifically, a third current sensor 34 may be disposed on the positive dc bus, and the current information of the dc bus, which may include a current value, is detected by the third current sensor 34 and sent to the control unit.

Further, the control part is further configured to determine the current absolute value of the branch where any one photovoltaic group string is located according to the first current information, determine the current absolute value of the direct current bus according to the current information of the direct current bus, and detect that the photovoltaic power generation system fails when the current absolute value of the branch where any one photovoltaic group string is located is greater than the current absolute value of the direct current bus; or determining the absolute value of the current of the branch where any one of the pole switches is located according to the second current information, determining the absolute value of the current of the direct current bus according to the current information of the direct current bus, and detecting that the photovoltaic power generation system fails when the absolute value of the current of the branch where any one of the pole switches is located is larger than the absolute value of the current of the direct current bus; or determining the current absolute value of the branch where any photovoltaic group string is located according to the first current information, determining the current absolute value of the direct current bus according to the current information of the direct current bus, determining the current absolute value of the branch where any one pole switch is located according to the second current information, and detecting that the photovoltaic power generation system fails when the current absolute value of the branch where any one photovoltaic group string is located is greater than the current absolute value of the direct current bus and the current absolute value of the branch where any one pole switch is located is greater than the current absolute value of the direct current bus.

That is, the control unit may determine whether the photovoltaic power generation system has a fault based on a relationship between the current level of the branch in which the photovoltaic string is located and the current level of the dc bus, or based on a relationship between the current level of the branch in which the pole switch is located and the current level of the dc bus, or based on a relationship between the current level of the branch in which the photovoltaic string is located and the current level of the dc bus, and based on a relationship between the current level of the branch in which the pole switch is located and the current level of the dc bus.

For example, referring to fig. 11b (1), under normal conditions, the current value of the branch where each photovoltaic string is located is the output current of the photovoltaic string when the photovoltaic string is operating normally, the current of the branch where each pole switch is located is the output current or the sum of the output currents of the photovoltaic strings connected with the pole switch, and the current value of the dc bus is the sum of the output currents of the 5 photovoltaic strings. When the photovoltaic string PV1 is shorted or reversely connected, referring to (2) of fig. 11b, the output current of the photovoltaic strings PV2 to PV5 is reversely fed to the photovoltaic string PV1, the current of the branch where each photovoltaic string and each pole switch are located is at least 1 time as large as the output current of the photovoltaic string, but only a small current flows through the dc bus, which is smaller than 1 time as large as the output current of the photovoltaic string, so that the photovoltaic power generation system malfunction is determined when the current absolute value of the branch where each photovoltaic string is located is determined to be larger than the current absolute value of the dc bus based on the first current information, or the current absolute value of the branch where each pole switch is determined to be larger than the current absolute value of the dc bus based on the second current information.

It should be noted that, the above-mentioned determination of whether the photovoltaic power generation system is faulty or not by the control unit and determination of whether to control the disconnection of the multipole linked switch based on the illumination intensity or the current value are mainly described with the system structures shown in fig. 11a and 11b, but these modes are not limited to the above-mentioned modes, and are applicable to all the system structures related to the present utility model, and detailed descriptions thereof are omitted herein.

In summary, according to the fault protection device of the photovoltaic power generation system provided by the embodiment of the utility model, when the photovoltaic power generation system breaks down, the switching tube in the power conversion unit is controlled to short-circuit the positive input end and the negative input end of the power conversion unit, so that the current flowing through the multipole linkage switch can be reduced, the safety of the multipole linkage switch when being disconnected is improved, and the multipole linkage switch can break and isolate the fault more safely and reliably; after the multipole linkage switch is disconnected, at most three photovoltaic group strings in the N photovoltaic group strings are connected in parallel, so that the safety of the photovoltaic group strings can be improved.

In some embodiments, a combiner box 200 is also provided. Referring to fig. 12, the junction box 200 may include the aforementioned fault protection device 100, and the fault protection device 100 is configured to divide between the N photovoltaic string PV1, PV2,..pvn and the power conversion unit 10 such that at most three of the N photovoltaic string PV1, PV2,..pvn are connected in parallel in the event of a fault in the photovoltaic power generation system.

It should be noted that, in some examples, the combiner box 200 may also include the power conversion unit 10, and the power conversion unit 10 may be, but is not limited to, a DC/DC converter, and reference is made to the foregoing for the relevant description of the fault protection device 100, which is not repeated herein.

According to the junction box disclosed by the embodiment of the utility model, based on the fault protection device, under the condition that a photovoltaic power generation system breaks down, at most three photovoltaic group strings in N photovoltaic group strings are connected in parallel after the multi-pole linkage switch is disconnected, so that the safety of the photovoltaic group strings can be improved.

In some embodiments, an inverter 300 is also provided. Referring to fig. 13, the inverter 300 may include: the fault protection device 100 and the power conversion unit 10 described above. Wherein the power conversion unit 10 comprises a DC/AC converter 11, the power conversion unit 10 being configured to convert the direct current output by the N photovoltaic strings PV1, PV2, PVN and to output an alternating current through the DC/AC converter 11. The fault protection device 100 is configured to divide between the N photovoltaic strings PV1, PV2, PVN and the power conversion unit 10 such that at most three of the N photovoltaic strings PV1, PV2, PVN are connected in parallel in the event of a fault in the photovoltaic power generation system.

In some embodiments, referring to fig. 14, the power conversion unit 10 further includes a DC/DC converter 12, a positive input of the DC/DC converter 12 being a positive input of the power conversion unit 10, a negative input of the DC/DC converter 12 being a negative input of the power conversion unit 10, an output of the DC/DC converter 12 being connected to an input of the DC/AC converter 11.

In some embodiments, referring to fig. 15, when the fault protection device 100 is plural, the DC/DC converter 12 is plural, the input terminal of each DC/DC converter 12 is connected to the corresponding multipole linked switch 20, and the output terminals of the plural DC/DC converters 12 are connected in parallel.

By way of example, fig. 16 provides two DC/DC converters and fig. 17 provides three DC/AC converters, but this is merely an exemplary illustration and not a limitation of the present utility model.

According to the inverter provided by the embodiment of the utility model, based on the fault protection device, under the condition that a photovoltaic power generation system breaks down, at most three photovoltaic strings in N photovoltaic strings are connected in parallel after the multipole linkage switch is disconnected, so that the safety of the photovoltaic strings can be improved.

In some embodiments, a photovoltaic power generation system is also provided. The photovoltaic power generation system includes the aforementioned fault protection device 100; or the aforementioned junction box 200; or the inverter 300 described above.

According to the photovoltaic power generation system provided by the embodiment of the utility model, based on the fault protection device, under the condition that the photovoltaic power generation system breaks down, at most three photovoltaic strings in N photovoltaic strings are connected in parallel after the multipole linkage switch is disconnected, so that the safety of the photovoltaic strings can be improved.

It should be noted that the logic and/or steps represented in the flowcharts or otherwise described herein, for example, may be considered as a ordered listing of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this description, a "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium would include the following: an electrical connection (electronic device) having one or more wires, a portable computer diskette (magnetic device), a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CDROM). In addition, the computer readable medium may even be paper or other suitable medium on which the program is printed, as the program may be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a suitable manner, if necessary, and then stored in a computer memory.

It is to be understood that portions of the present utility model may be implemented in hardware, software, firmware, or a combination thereof. In the above-described embodiments, the various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, may be implemented using any one or combination of the following techniques, as is well known in the art: discrete logic circuits having logic gates for implementing logic functions on data signals, application specific integrated circuits having suitable combinational logic gates, programmable Gate Arrays (PGAs), field Programmable Gate Arrays (FPGAs), and the like.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present utility model. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present utility model, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present utility model, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

While embodiments of the present utility model have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the utility model, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the utility model.

Claims

1. The utility model provides a fault protection device of photovoltaic power generation system, its characterized in that, photovoltaic power generation system still includes power conversion unit, N photovoltaic group cluster, and wherein, N is the integer of 3 or more, fault protection device includes:

the positive connecting ends and the negative connecting ends are suitable for connecting the X positive connecting ends and the Y negative connecting ends of the N photovoltaic strings, wherein X is more than or equal to 2 and less than or equal to N, Y is more than or equal to 2 and less than or equal to N, and when one of X and Y is equal to N, X is not equal to Y;

a multipole linkage switch, wherein a first end of each pole switch in the multipole linkage switch is correspondingly connected with one connecting end of the X positive connecting ends and the Y negative connecting ends, a second end of each pole switch connected with the positive connecting ends is suitable for being connected with a positive input end of the power conversion unit, and each pole switch connected with the negative connecting ends is suitable for being connected with a negative input end of the power conversion unit;

wherein the multipole ganged switch is configured in an off state in case of a failure of the photovoltaic power generation system such that at most three of the N photovoltaic strings are connected in parallel.

2. The fault protection device of claim 1, further comprising:

and a control part configured to control a switching tube in the power conversion unit to short-circuit a positive input terminal and a negative input terminal of the power conversion unit in case of a failure of the photovoltaic power generation system.

3. The fault protection device of claim 1, wherein the number of photovoltaic strings to which each positive connection is adapted to be connected is at most three, and/or the number of photovoltaic strings to which each negative connection is adapted to be connected is at most three.

4. A fault protection device according to claim 3, wherein the cathodes of a plurality of strings of photovoltaic groups, to which the same positive connection is adapted, are respectively connected to at least two negative connections.

5. The fault protection device of claim 1, wherein when any one positive connection terminal is adapted to connect more than four photovoltaic strings, at least two negative connection terminals are adapted to connect the negative poles of the more than four photovoltaic strings, and the number of photovoltaic strings to which the same negative connection terminal is adapted to connect is at most three.

6. The fault protection device of claim 1, wherein when any one of the negative connection terminals is adapted to connect more than four photovoltaic strings, at least two positive connection terminals are adapted to connect anodes of the more than four photovoltaic strings, and the number of photovoltaic strings to which the same positive connection terminal is adapted to connect is at most three.

7. The fault protection device of claim 2, further comprising:

the parameter detection part is connected with the control part and is configured to detect at least one of the parameter value of the branch where each photovoltaic group string is located, the parameter value of the branch where each pole switch is located and the parameter value of the direct current bus, so that the control part determines that the photovoltaic power generation system fails according to at least one of the parameter value of the branch where each photovoltaic group string is located, the parameter value of the branch where each pole switch is located and the parameter value of the direct current bus.

8. The fault protection device of claim 7, wherein the parameter values comprise one or more of voltage values, current values, temperature values, and power values.

9. A combiner box, characterized in that it comprises a fault protection device according to any one of claims 1-8, configured to break between the N photovoltaic strings and the power conversion unit in case of a fault of the photovoltaic power generation system, such that at most three of the N photovoltaic strings are connected in parallel.

10. An inverter, comprising:

a power conversion unit including a DC/AC converter;

the fault protection device according to any one of claims 1-8;

the power conversion unit is configured to convert direct current output by the N photovoltaic strings and output alternating current through the DC/AC converter, and the fault protection device is configured to break the N photovoltaic strings and the power conversion unit under the condition that the photovoltaic power generation system breaks down, so that at most three photovoltaic strings in the N photovoltaic strings are connected in parallel.

11. The inverter of claim 10, wherein the power conversion unit further comprises a DC/DC converter, a positive input of the DC/DC converter being a positive input of the power conversion unit, a negative input of the DC/DC converter being a negative input of the power conversion unit, an output of the DC/DC converter being connected to an input of the DC/AC converter.

12. The inverter according to claim 11, wherein when the fault protection device is plural, the DC/DC converter is plural, an input terminal of each of the DC/DC converters is connected to a corresponding multipole interlock switch, and output terminals of the DC/DC converters are connected in parallel.

13. A photovoltaic power generation system, comprising:

the fault protection device according to any one of claims 1-8; or alternatively

The combiner box of claim 9; or alternatively

The inverter according to any one of claims 10-12.