Solar power generation system and its fault protection method, apparatus, combiner box, and inverter

Abstract

Disclosed are a photovoltaic power generation system and a method, apparatus, combiner box, and inverter thereof relating to the technical field of photovoltaic power generation. The system includes a power conversion unit, a multi-pole interlocking switch, and N photovoltaic strings, and the method includes the steps of controlling a switching element in the power conversion unit to short-circuit the positive and negative input terminals of the power conversion unit and controlling the multi-pole interlocking switch to turn off so that up to three of the N photovoltaic strings are connected in parallel when a failure occurs in the photovoltaic power generation system.

Description

Technical Field

[0001] [Cross-Reference to Related Disclosures] This disclosure claims the priority of a Chinese patent application with an application number of 202310604548.6 and a title of "Photovoltaic Power Generation System and Its Fault Protection Method, Device, Combiner Box, and Inverter" filed on May 26, 2023, and all of its content is incorporated herein by reference.

[0002] This disclosure relates to the technical field of photovoltaic power generation, and particularly to a photovoltaic power generation system and its fault protection method, device, combiner box, and inverter.

Background Art

[0003] In a photovoltaic power generation system, a plurality of photovoltaic power generation strings are connected to a power conversion unit through a fault isolation circuit, and the generated electricity is supplied to the power conversion unit through the fault isolation circuit. The fault isolation circuit uses a DC switch with a cutoff function, and when a fault such as a short circuit fault or reverse connection fault of a photovoltaic power generation string or a fault inside the power conversion unit occurs in the photovoltaic power generation system, the DC switch is controlled to be cutoff, so as to realize the fault isolation between the photovoltaic power generation string and the power conversion unit.

[0004] However, when a short circuit fault or reverse connection fault occurs in a photovoltaic power generation string, the short circuit current or reverse connection current of the branch circuit where the corresponding DC switch is located is large. If the DC switch is cutoff in this state of large short circuit current or reverse connection current, it will involve certain safety risks.

Summary of the Invention

Problems to be Solved by the Invention

[0005] This disclosure aims to solve, at least to some extent, one of the technical challenges in related technologies. To this end, this disclosure aims to provide a photovoltaic power generation system and its fault protection method, apparatus, combiner box, and inverter, which improves safety when a multi-pole interlocking switch is turned off by short-circuiting the positive and negative input terminals of the power conversion unit in the event of a system failure, thereby enabling the multi-pole interlocking switch to shut off and isolate from faults more safely and reliably, and after the multi-pole interlocking switch is turned off, the safety of the photovoltaic power generation strings can be improved by connecting up to three of the N photovoltaic power generation strings in parallel. [Means for solving the problem]

[0006] According to a first aspect, an embodiment of the present disclosure provides a fault protection method for a photovoltaic system, the photovoltaic system comprising a power conversion unit, a multi-pole interlocking switch, N photovoltaic strings, and positive and negative connection terminals for connecting to the N photovoltaic strings, wherein each pole switch in the multi-pole interlocking switch has a first end connected to either a positive or negative connection terminal and a second end connected to either a positive or negative input terminal of the power conversion unit, where N is an integer of 3 or more, and the fault protection method includes the step of controlling a switching element in the power conversion unit to short-circuit the positive and negative input terminals of the power conversion unit and to turn off the multi-pole interlocking switch so that up to three of the N photovoltaic strings are connected in parallel when a fault occurs in the photovoltaic system.

[0007] According to the fault protection method for a photovoltaic power generation system of the embodiment of the present disclosure, when a fault occurs in the photovoltaic power generation system, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate against faults, and after the multi-pole interlocking switch is turned off, the safety of the photovoltaic power generation strings can be improved by ensuring that up to three of the N photovoltaic power generation strings are connected in parallel.

[0008] According to a second aspect, an embodiment of the present disclosure provides a fault protection device for a photovoltaic power generation system, the photovoltaic power generation system further comprising a power conversion unit and N photovoltaic strings, where N is an integer of 3 or more, and the fault protection device includes a positive terminal, a negative terminal for connecting to the N photovoltaic strings, a multi-pole interlocking switch, each pole switch in the multi-pole interlocking switch having a first end connected to the positive terminal or negative terminal and a second end connected to the positive input terminal or negative input terminal of the power conversion unit, and a control unit that, when a fault is detected in the photovoltaic power generation system, controls a switching element in the power conversion unit to short-circuit the positive input terminal and the negative input terminal of the power conversion unit, and controls the multi-pole interlocking switch to turn off, so that up to three of the N photovoltaic strings are connected in parallel.

[0009] According to the fault protection device for a photovoltaic power generation system of the embodiment of the present disclosure, when a fault occurs in the photovoltaic power generation system, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate against faults, and after the multi-pole interlocking switch is turned off, up to three of the N photovoltaic power generation strings are connected in parallel, thereby improving the safety of the photovoltaic power generation strings.

[0010] According to a third aspect, an embodiment of the present disclosure provides a combiner box including the fault protection device described above, which, in the event of a fault in the photovoltaic system, short-circuits the positive and negative input terminals of the power conversion unit, thereby disconnecting the N photovoltaic strings from the power conversion unit so that up to three of the N photovoltaic strings are connected in parallel.

[0011] According to the combiner box of the embodiment of this disclosure, when a failure occurs in the photovoltaic power generation system, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate in the event of a failure, and after the multi-pole interlocking switch is turned off, up to three of the N photovoltaic power generation strings are connected in parallel, thereby improving the safety of the photovoltaic power generation strings.

[0012] According to a fourth aspect, an embodiment of the present disclosure provides an inverter comprising the above-mentioned fault protection device and a power conversion unit equipped with a DC / AC converter, the power conversion unit converts DC power output from N photovoltaic strings to output AC power via the DC / AC converter, and the fault protection device, in the event of a fault in the photovoltaic system, short-circuits the positive and negative input terminals of the power conversion unit, thereby disconnecting the N photovoltaic strings from the power conversion unit so that up to three of the N photovoltaic strings are connected in parallel.

[0013] According to the inverter of the embodiment of this disclosure, when a failure occurs in the photovoltaic power generation system, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. This allows the multi-pole interlocking switch to shut off and isolate in the event of a failure more safely and reliably, and after the multi-pole interlocking switch is turned off, up to three of the N photovoltaic power generation strings are connected in parallel, thereby improving the safety of the photovoltaic power generation strings.

[0014] According to a fifth aspect, an embodiment of the present disclosure provides a photovoltaic power generation system, which includes the above-mentioned fault protection device.

[0015] According to the photovoltaic power generation system of the embodiment of this disclosure, if a failure occurs in the photovoltaic power generation system, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate against failures, and after the multi-pole interlocking switch is turned off, up to three of the N photovoltaic power generation strings are connected in parallel, thereby improving the safety of the photovoltaic power generation strings.

[0016] Further aspects and advantages of this disclosure are partially described in the following description, clarified in the following description, or understood through the practice of this disclosure. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic diagram of the structure of a photovoltaic power generation system in related technologies. [Figure 2a] This is a schematic diagram of the structure of a photovoltaic power generation system having three photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 2b] This is a schematic diagram of the structure of a photovoltaic power generation system having three photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 3a] This is a schematic diagram of the structure of a photovoltaic power generation system having four photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 3b] This is a schematic diagram of the structure of a photovoltaic power generation system having four photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 4a] This is a schematic diagram of the structure of a photovoltaic power generation system having five photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 4b] This is a schematic diagram of the structure of a photovoltaic power generation system having five photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 5] This is a schematic diagram of the structure of a photovoltaic power generation system having six photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 6] This is a schematic diagram of the structure of a photovoltaic power generation system having seven photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 7] This is a schematic diagram of the structure of a photovoltaic power generation system having eight photovoltaic power generation strings according to one embodiment of the present disclosure. [Figure 8a] This is a schematic diagram of the structure of a photovoltaic system having five photovoltaic strings according to some other embodiments of the present disclosure. [Figure 8b] This is a schematic diagram of the structure of a photovoltaic system having five photovoltaic strings according to some other embodiments of the present disclosure. [Figure 9a] A structural schematic diagram of a solar power generation system having five solar power generation strings according to some further embodiments of the present disclosure. [Figure 9b] A structural schematic diagram of a solar power generation system having five solar power generation strings according to some further embodiments of the present disclosure. [Figure 10a] A structural schematic diagram of a solar power generation system having five solar power generation strings according to some further embodiments of the present disclosure. [Figure 10b] A structural schematic diagram of a solar power generation system having five solar power generation strings according to some further embodiments of the present disclosure. [Figure 11a] A structural schematic diagram of a solar power generation system having five solar power generation strings according to some embodiments of the present disclosure. [Figure 11b] A structural schematic diagram of a solar power generation system having five solar power generation strings according to some embodiments of the present disclosure. [Figure 12] A structural schematic diagram of a combiner box according to an embodiment of the present disclosure. [Figure 13] A structural schematic diagram of an inverter according to an embodiment of the present disclosure. [Figure 14] A structural schematic diagram of a solar power generation system according to an embodiment of the present disclosure. [Figure 15] A structural schematic diagram of a solar power generation system according to another embodiment of the present disclosure. [Figure 16] A structural schematic diagram of a solar power generation system according to yet another embodiment of the present disclosure. [Figure 17] A structural schematic diagram of a DC / DC converter according to some embodiments of the present disclosure. [Figure 18] A structural schematic diagram of a DC / AC converter according to some embodiments of the present disclosure.

Embodiments for Carrying Out the Invention

[0018] The embodiments of this disclosure are described below in detail, and examples of such embodiments are shown in the accompanying drawings, where the same or similar reference numerals throughout the drawings indicate the same or similar elements or elements having the same or similar function. The embodiments described below with reference to the accompanying drawings are illustrative and for illustrative purposes only, and should not be construed as limiting the disclosure.

[0019] Referring to Figure 1, in the photovoltaic power generation system, N photovoltaic power strings PV1, PV2, ..., PVN are connected to a power conversion unit via a fault isolation circuit, and the generated electricity is supplied to the power conversion unit via the fault isolation circuit. The fault isolation circuit uses a DC switch with a tripping function, and the tripping of the DC switch may be controlled manually or by a control unit inside the system.

[0020] If a fault occurs in the solar power generation system, such as a short circuit or reverse connection fault in the solar power generation string, or a fault inside the power conversion unit, fault isolation between the solar power generation string and the power conversion unit can be achieved by manually or automatically controlling the DC switch to shut off.

[0021] However, if a short-circuit or reverse connection fault occurs in a solar power generation string, the short-circuit current or reverse connection current in the branch circuit where the corresponding DC switch is located will be large. Shutting off the DC switch under these conditions of large short-circuit or reverse connection current poses a certain safety risk.

[0022] Based on this, embodiments of the present disclosure provide a photovoltaic power generation system and a fault protection method, apparatus, combiner box, and inverter thereof. In the event of a fault in the photovoltaic power generation system, such as a short-circuit fault or reverse connection fault in the photovoltaic string, the safety when the multi-pole interlocking switch turns off can be improved by short-circuiting the positive and negative input terminals of the power conversion unit. This allows the multi-pole interlocking switch to shut off and isolate the power more safely and reliably in the event of a fault. After the multi-pole interlocking switch turns off, the safety of the photovoltaic strings can be improved by ensuring that up to three of the N photovoltaic strings are connected in parallel.

[0023] To enable those skilled in the art to better understand the technical solutions of the present disclosure, the technical solutions of the embodiments of the present disclosure will be clearly described below, with reference to the drawings of the embodiments.

[0024] The photovoltaic power generation system provided in the embodiments of the present disclosure includes a power conversion unit and N photovoltaic strings. The fault protection device includes X positive terminals and Y negative terminals for connecting to the N photovoltaic strings, a multi-pole interlocking switch, and a control unit, wherein the first end of each pole switch in the multi-pole interlocking switch is connected to one of the X positive terminals and Y negative terminals, the second end of each pole switch connected to the positive terminal is connected to the positive input terminal of the power conversion unit, and the second end of each pole switch connected to the negative terminal is connected to the negative input terminal of the power conversion unit, where N is an integer greater than or equal to 3, 2 ≤ X ≤ N, 2 ≤ Y ≤ N, and if either X or Y is equal to N, X is not equal to Y. When the control unit detects that a fault has occurred in the photovoltaic power generation system, it controls the switching elements in the power conversion unit to short-circuit the positive input terminal and negative input terminal of the power conversion unit, and controls the multi-pole interlocking switch to turn off, so that up to three of the N photovoltaic strings are connected in parallel.

[0025] A power conversion unit refers to a device that can convert the power generated from a solar power generation string into the power required by the user. For example, when a solar power generation system is on-grid, the power conversion unit can convert the DC power generated from the solar power generation string into commercial AC power to keep it on-grid. When a solar power generation system directly supplies power to an AC load, the power conversion unit converts the DC power generated from the solar power generation string into the AC power required by the AC load and supplies it to the AC load. When a solar power generation system directly supplies power to a DC load, the power conversion unit converts the DC power generated from the solar power generation string into the DC power required by the DC load and supplies it to the DC load. The structure of the power conversion unit is not limited; for example, depending on the needs, the power conversion unit may be a DC / DC converter or a DC / AC converter, but is not limited to these. DC is direct current, AC is alternating current, a DC / DC converter is a DC-to-DC converter, and a DC / AC converter is a DC-to-AC converter.

[0026] A multi-pole interlocking switch is a switch that includes multiple interlocking pole switches, for example, multiple pole switches that can be turned on or off simultaneously. The pole switches include a positive pole switch and a negative pole switch, the positive pole switch being connected to the positive pole of the solar power generation string, and the negative pole switch being connected to the negative pole of the solar power generation string. The structure and model numbers of the positive pole switch and the negative pole switch may be the same or different; in other words, the switches themselves are not classified, and either may be a DC switch such as a DC circuit breaker, but is not limited to these.

[0027] A solar power generation string is formed by connecting multiple solar power generation modules in series or parallel. For example, a solar power generation string can be formed by directly connecting multiple solar power generation modules in series, or by connecting multiple solar power generation modules in parallel and then connecting them in series. The specific number of solar power generation modules included in the solar power generation string, parameters, etc., are not limited herein. In the embodiments of this disclosure, the solar power generation system includes N solar power generation strings, where N is an integer of 3 or more. When N=1 or N=2, even if a short circuit or reverse connection failure occurs in the solar power generation string, the current flowing through the multi-pole interlocking switch does not increase during the short circuit or reverse connection. Therefore, when the multi-pole interlocking switch turns off, the safety risk is relatively small. In this case, it is not necessary to short-circuit the positive and negative input terminals of the power conversion unit to reduce the current flowing through the multi-pole interlocking switch. Therefore, in the embodiments of this disclosure, the number of solar power generation strings is an integer of 3 or more.

[0028] N solar power strings are connected to a multi-pole interlocking switch via X positive terminals and Y negative terminals. The total number of pole switches on the multi-pole interlocking switch is the same as the total number of positive and negative terminals. The number of positive switches is the same as the number of positive terminals, and the number of negative switches is the same as the number of negative terminals. In other words, N solar power strings are connected to the first ends of X positive switches via X positive terminals, and to the first ends of Y negative switches via Y negative terminals. The second ends of the X positive switches are further connected to the positive input terminals of the power conversion unit, and the second ends of the Y negative switches are further connected to the negative input terminals of the power conversion unit. If 2 ≤ X ≤ N and 2 ≤ Y ≤ N, and if either X or Y is equal to N, then X is not equal to Y. That is, the maximum number of positive and negative connection terminals is both less than or equal to the number of photovoltaic strings, and the minimum number is both 2 or more. If one of them is equal to the number of photovoltaic strings, then the two numbers are different, and this allows for a certain reduction in the number of pole switches.

[0029] Furthermore, in order to ensure that up to three of the N solar power generation strings are connected in parallel after the multi-pole interlocking switch is turned off, if X and Y satisfy the above conditions, it is also necessary that after the multi-pole interlocking switch 20 is turned off, up to three of the N solar power generation strings are connected in parallel.

[0030] As an example, we will explain a solar power generation system using Situation 1: N=3 as an example.

[0031] When N=3, there are many possibilities for the number of positive and negative connection terminals; for example, when X=3, Y=2, or when X=2, Y=2 or 3. In this case, X and Y satisfy 2≦X≦N, 2≦Y≦N, and when one of X or Y is equal to N, X is not equal to Y. At the same time, there are a maximum of 2 photovoltaic strings connected to each connection terminal, and after the multi-pole interlocking switch 20 is turned off, a maximum of 3 of the N photovoltaic strings are connected in parallel.

[0032] For example, when X=3 and Y=2, referring to Figure 2a, the photovoltaic power generation system includes three photovoltaic power strings PV1, PV2, PV3 and a power conversion unit 10. The fault protection device includes three positive terminals X1, X2, X3, two negative terminals Y1, Y2, a multi-pole interlocking switch 20 and a control unit (not shown), the multi-pole interlocking switch 20 includes three positive switches SX1, SX2, SX3 and two negative switches SY1, SY2. The positive electrode PV1+ of the solar power generation string PV1 is connected to the first terminal of the positive switch SX1 via the positive connection terminal X1, the positive electrode PV2+ of the solar power generation string PV2 is connected to the first terminal of the positive switch SX2 via the positive connection terminal X2, the positive electrode PV3+ of the solar power generation string PV3 is connected to the first terminal of the positive switch SX3 via the positive connection terminal X3, the negative electrode PV1- of the solar power generation string PV1 and the negative electrode PV2- of the solar power generation string PV2 are both connected to the first terminal of the negative switch SY1 via the negative connection terminal Y1, the negative electrode PV3- of the solar power generation string PV3 is connected to the first terminal of the negative switch SY2 via the negative connection terminal Y2, the second terminals of the positive switches SX1, SX2, and SX3 are all connected to the positive input terminal of the power conversion unit 10, and the second terminals of the negative switches SY1 and SY2 are all connected to the negative input terminal of the power conversion unit 10.

[0033] Note that Figure 2a is merely an illustrative example, and other connection methods may be used in this situation. For example, PV1- and PV3- may be connected to the first end of SY1 via Y1, or PV2- and PV3- may be connected to the first end of SY1 via Y1. These will not be explained in detail here.

[0034] Furthermore, for example, when X=2 and Y=2, referring to Figure 2b, the photovoltaic power generation system includes three photovoltaic power strings PV1, PV2, and PV3, and a power conversion unit 10. The fault protection device includes two positive terminals X1 and X2, two negative terminals Y1 and Y2, a multi-pole interlocking switch 20, and a control unit (not shown), the multi-pole interlocking switch 20 includes two positive switches SX1 and SX2, and two negative switches SY1 and SY2. The positive electrode PV1+ of solar power string PV1 and the positive electrode PV2+ of solar power string PV2 are both connected to the first end of the positive switch SX1 via the positive connection terminal X1, the positive electrode PV3+ of solar power string PV3 is connected to the first end of the positive switch SX2 via the positive connection terminal X2, the negative electrode PV1- of solar power string PV1 and the negative electrode PV2- of solar power string PV2 are both connected to the first end of the negative switch SY1 via the negative connection terminal Y1, the negative electrode PV3- of solar power string PV3 is connected to the first end of the negative switch SY2 via the negative connection terminal Y2, the second ends of the positive switches SX1 and SX2 are both connected to the positive input terminal of the power conversion unit 10, and the second ends of the negative switches SY1 and SY2 are both connected to the negative input terminal of the power conversion unit 10.

[0035] Note that Figure 2b is merely an illustrative example, and other connection methods may be used in this situation. For example, PV1- and PV3+ may be connected to the first end of SX1 via X1, or PV2+ and PV3+ may be connected to the first end of SX1 via X1. These will not be explained in detail here.

[0036] When X=2 and Y=3, the system structure is symmetrical to the structure in Figure 2a, and a detailed explanation is omitted here.

[0037] Situation 2: We will explain a solar power generation system using N=4 as an example.

[0038] When N=4, there are many possibilities for the number of positive and negative connection terminals. For example, when X=4, Y=3 or 2, and when X=3 or 2, Y=2, 3, or 4. In this case, X and Y satisfy 2≦X≦N, 2≦Y≦N, and when one of X and Y is equal to N, X is not equal to Y. At the same time, there are a maximum of 3 photovoltaic strings connected to each connection terminal, and after the multi-pole interlocking switch 20 is turned off, a maximum of 3 of the N photovoltaic strings are connected in parallel.

[0039] In this situation, the structure of solar power generation systems varies, so to avoid redundancy, we will not explain each system structure individually here, but will instead provide an illustrative explanation using only the examples shown in Figures 3a and 3b.

[0040] Situation 3: Explain the solar power generation system using N=5 as an example.

[0041] When N=5, there are many possibilities for the number of positive and negative connection terminals. For example, when X=5, Y=4, 3, or 2; when X=4, 3, or 2, Y=5, 4, 3, or 2; and when X=2 and Y=2, by rationally arranging the connection relationships, it is possible to satisfy the condition that a maximum of 3 of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off. For example, if the same positive connection terminal is connected to the positive terminals of 4 photovoltaic strings, the negative terminals of those 4 photovoltaic strings are connected via 2 negative connection terminals. Also, for example, the same positive connection terminal is connected to the positive terminals of up to 3 photovoltaic strings, and the same negative connection terminal is connected to the negative terminals of up to 3 photovoltaic strings. In this case, X and Y satisfy the conditions 2 ≤ X ≤ N, 2 ≤ Y ≤ N, and when one of X and Y is equal to N, X is not equal to Y. At the same time, after the multi-pole interlocking switch 20 is turned off, a maximum of three of the N solar power generation strings are connected in parallel.

[0042] In this situation, the structure of solar power generation systems varies, so to avoid redundancy, we will not explain each system structure individually here, but will instead provide an illustrative explanation using only the examples shown in Figures 4a and 4b.

[0043] Situation 4: We will explain the solar power generation system using N=6 as an example.

[0044] When N=6, there are many possibilities for the number of positive and negative connection terminals. For example, when X=6, Y=5, 4, 3, or 2; 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 rationally arranging the connection relationships, it is possible to satisfy the condition that a maximum of 3 of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off. For example, when X=3 and Y=3, the same positive connection terminal is connected to the positive terminals of 4 photovoltaic strings, and the negative terminals of those 4 photovoltaic strings are connected via at least 2 negative connection terminals. Also, for example, the same positive connection terminal is connected to the positive terminals of up to 3 photovoltaic strings, and the same negative connection terminal is connected to the negative terminals of up to 3 photovoltaic strings. Note that this is merely an illustrative explanation, and other situations will not be explained one by one here. In this case, X and Y satisfy the conditions 2 ≤ X ≤ N, 2 ≤ Y ≤ N, and when one of X and Y is equal to N, X is not equal to Y. At the same time, after the multi-pole interlocking switch 20 is turned off, a maximum of three of the N solar power generation strings are connected in parallel.

[0045] In this situation, the structure of solar power generation systems varies, so to avoid redundancy, we will not explain each system structure individually here, but will instead use only the example shown in Figure 5 for illustrative purposes.

[0046] Situation 5: We will explain the solar power generation system using N=7 as an example.

[0047] When N=7, there are many possibilities for the number of positive and negative connection terminals. For example, when X=7, Y=6, 5, 4, 3, or 2; 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 X=3 and Y=4, 3, or 2, the connection relationships can be rationally arranged to satisfy the condition that a maximum of 3 of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off. For example, when X=4 and Y=4, if the same positive connection terminal is connected to the positive terminals of 4 photovoltaic strings, the negative terminals of those 4 photovoltaic strings are connected via at least 2 negative connection terminals. Also, for example, the same positive connection terminal is connected to the positive terminals of up to 3 photovoltaic strings, and the same negative connection terminal is connected to the negative terminals of up to 3 photovoltaic strings. Note that this is merely an illustrative explanation, and other situations will not be explained individually here. In this case, X and Y satisfy the conditions 2 ≤ X ≤ N, 2 ≤ Y ≤ N, and when one of X or Y is equal to N, X is not equal to Y. At the same time, after the multi-pole interlocking switch 20 is turned off, a maximum of three of the N solar power generation strings are connected in parallel.

[0048] In this situation, the structure of solar power generation systems varies, so to avoid redundancy, we will not explain each system structure individually here, but will instead use only the example shown in Figure 6 for illustrative purposes.

[0049] Situation 6: We will explain the solar power generation system using N=8 as an example.

[0050] When N=8, there are many possibilities for the number of positive and negative connection terminals. For example, when X=8, Y=7, 6, 5, 4, 3, or 2; 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 X=4 and Y=5, 4, 3, or 2, or X=3 and Y=5, 4, 3, or 2, a rational arrangement of the connection relationships satisfies the condition that a maximum of 3 of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off. For example, when X=5 and Y=5, if the same positive connection terminal is connected to the positive terminals of 4 photovoltaic strings, the negative terminals of those 4 photovoltaic strings are connected via at least 2 negative connection terminals. Note that this is merely an illustrative explanation, and other situations will not be explained individually here. In this case, X and Y satisfy the conditions 2 ≤ X ≤ N, 2 ≤ Y ≤ N, and when one of X or Y is equal to N, X is not equal to Y. At the same time, after the multi-pole interlocking switch 20 is turned off, a maximum of three of the N solar power generation strings are connected in parallel.

[0051] In this situation, the structure of solar power generation systems varies, so to avoid redundancy, we will not explain each system structure individually here, but will instead use only the example shown in Figure 7 for illustrative purposes.

[0052] For other situations not exemplified above, please refer to the above; a detailed explanation will not be provided here.

[0053] The protection principle of the fault protection device will be explained below by combining the above situations 1 to 6.

[0054] For example, in Situation 1, referring to Figure 2a, if the solar power generation system is functioning normally, solar power strings PV1, PV2, and PV3 supply the generated electricity to the power conversion unit 10 via the multi-pole interlocking switch 20. If a failure occurs in the solar power generation system, for example, if a short circuit or reverse connection occurs in solar power string PV1, referring to (1) in Figure 2a, in the case of a short circuit, the current from solar power strings PV2 and PV3 flows into solar power string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 corresponding to solar power string PV1 needs to interrupt twice the short circuit current of a single solar power string, i.e., the sum of the currents of solar power strings PV2 and PV3, and the negative switch SY1 corresponding to solar power string PV1 needs to interrupt one short circuit current of a single solar power string, i.e., the current of solar power string PV3. In this case, the multi-pole interlocking switch 20 needs to interrupt a maximum interruption current of twice that of a single solar power string, and in the case of a reverse connection, i.e., the positive P of solar power string PV1 When the positions of V1+ and the negative terminal PV1- are swapped, there are diodes connected in antiparallel inside the solar power generation module, so the current from solar power generation strings PV2 and PV3 flows back into solar power generation string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 corresponding to solar power generation string PV1 needs to interrupt twice the reverse connection current of a single solar power generation string, i.e., the sum of the currents of solar power generation strings PV2 and PV3, and the negative switch SY1 corresponding to solar power generation string PV1 needs to interrupt one times the reverse connection current of a single solar power generation string, i.e., the current of solar power generation string PV3. In this case, the multi-pole interlocking switch 20 needs to interrupt a maximum of twice the interruption current of a single solar power generation string and interrupt twice the interruption voltage of a single solar power generation string.

[0055] In this case, as shown in (2) of Figure 2a, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10, that is, to form a new short-circuit or reverse connection path inside the power conversion unit 10. Since the impedance of the switching element Q in this path is smaller than the impedance of the photovoltaic string, most of the short-circuit or reverse connection current passes through this path, thereby effectively reducing the current flowing through the positive switch SX1 corresponding to the photovoltaic string PV1, and also reducing the current flowing through the positive switch SX1 corresponding to the faulty photovoltaic string PV1. The short-circuit or reverse connection current and cutoff voltage flowing through 1 can be reduced. In this case, the maximum cutoff current of the multi-pole interlocking switch 20 is 1 times that of a single solar power string, and the maximum cutoff voltage in reverse connection is 1 times that of a single solar power string. Compared to twice the cutoff current and twice the cutoff voltage of a single solar power string, the maximum cutoff current and maximum cutoff voltage of the multi-pole interlocking switch 20 are effectively reduced, and the positive switch SX1 can be turned off more safely and reliably. The multi-pole interlocking switch 20 can perform cutoff and isolation in the event of a fault more safely and reliably. The switching element Q is generally a semiconductor device and includes, but is not limited to, IGBTs and MOSFETs.

[0056] The control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive and negative input terminals of the power conversion unit 10. Simultaneously, or afterward, the control unit controls the multi-pole interlocking switch 20 to turn off, so that up to three of the N photovoltaic strings are connected in parallel. In this way, when one photovoltaic string can withstand the current output from up to two other photovoltaic strings, if a failure occurs in a photovoltaic string, up to two normal photovoltaic strings will output current to it. In this case, the current will be within the range that the failed photovoltaic string can withstand, thus protecting the photovoltaic string from damage. For example, in the example shown in Figure 2a, after the multi-pole interlocking switch 20 is turned off, there is no parallel connection in the photovoltaic strings, so the photovoltaic strings are not damaged.

[0057] The protection principle in the event of a short circuit or reverse connection in the photovoltaic string PV2 is the same as the protection principle in the event of a short circuit or reverse connection in the photovoltaic string PV1. Therefore, to avoid redundancy, a detailed explanation is omitted here.

[0058] When a short circuit or reverse connection occurs in the solar power generation string PV3, as can be seen by referring to the above principle, the current flowing through the positive switch SX3 and negative switch SY2 corresponding to the solar power generation string PV3 can be effectively reduced. In this case, the maximum breaking current of the multi-pole interlocking switch 20 does not change, but the short circuit or reverse connection current and breaking voltage flowing through the positive switch SX3 and negative switch SY2 corresponding to the faulty solar power generation string PV3 are reduced. This allows the positive switch SX3 and negative switch SY2 to be turned off more safely and reliably, and the multi-pole interlocking switch 20 can more safely and reliably shut off and isolate from the fault.

[0059] Furthermore, referring to Figure 2b, for example, if the solar power generation system is functioning normally, the solar power strings PV1, PV2, and PV3 supply the generated electricity to the power conversion unit 10 via the multi-pole interlocking switch 20.

[0060] If a malfunction occurs in the solar power generation system, for example, if a short circuit or reverse connection occurs in solar power generation string PV1, referring to (1) in Figure 2b, the current from solar power generation strings PV2 and PV3 flows into solar power generation string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 and negative switch SY1 corresponding to solar power generation string PV1 need to interrupt the short circuit or reverse connection current which is one times that of a single solar power generation string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 is one times that of a single solar power generation string, and in the case of reverse connection, it is also necessary to interrupt the interrupting voltage which is twice that of a single solar power generation string.

[0061] In this case, as shown in (2) of Figure 2b, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10, thereby effectively reducing the current flowing through the positive switch SX1 and the negative switch SY1 corresponding to the solar power generation string PV1. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is still 1x the tripping current of a single solar power generation string, but the short-circuit or reverse connection current and tripping voltage flowing through the positive switch SX1 and the negative switch SY1 corresponding to the faulty solar power generation string PV1 are reduced. As a result, the positive switch SX1 and the negative switch SY1 are turned off more safely and reliably, and the multi-pole interlocking switch 20 can more safely and reliably trip and isolate against faults.

[0062] After the multi-pole interlocking switch 20 is turned off, the solar power strings PV1 and PV2 are connected in parallel. If solar power string PV1 is short-circuited or reverse-connected, the current from solar power string PV2 flows into solar power string PV1. Solar power string PV1 can withstand the current output from up to two solar power strings, and since this does not exceed the limit that solar power string PV1 can withstand, solar power string PV1 is effectively protected from damage.

[0063] The protection principle in the event of a short circuit or reverse connection in the photovoltaic string PV2 is the same as the protection principle in the event of a short circuit or reverse connection in the photovoltaic string PV1. Therefore, to avoid redundancy, a detailed explanation is omitted here.

[0064] When a short circuit or reverse connection occurs in the solar power generation string PV3, as can be seen by referring to the above principle, the current flowing through the positive switch SX2 and negative switch SY2 corresponding to the solar power generation string PV3 can be effectively reduced. In this case, the maximum breaking current of the multi-pole interlocking switch 20 does not change, but the short circuit or reverse connection current and breaking voltage flowing through the positive switch SX2 and negative switch SY2 corresponding to the faulty solar power generation string PV3 are reduced. As a result, the positive switch SX2 and negative switch SY2 can be turned off more safely and reliably, and the multi-pole interlocking switch 20 can perform shutdown and isolation in the event of a fault more safely and reliably.

[0065] For protection principles of other system structures where N=3, please refer to the above; a detailed explanation is omitted here.

[0066] For example, in the case of situation 2, referring to Figure 3a, if the solar power generation system is functioning normally, the solar power strings PV1 to PV4 supply the generated electricity to the power conversion unit 10 via the multi-pole interlocking switch 20.

[0067] If a malfunction occurs in the solar power generation system, for example, if a short circuit or reverse connection occurs in solar power generation string PV1, referring to (1) in Figure 3a, the currents from solar power generation strings PV2, PV3, and PV4 will flow into solar power generation string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 corresponding to solar power generation string PV1 will need to interrupt a short circuit or reverse connection current three times that of a single solar power generation string, and the negative switch SY1 corresponding to solar power generation string PV1 will need to interrupt a short circuit or reverse connection current twice that of a single solar power generation string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 is three times that of a single solar power generation string, and in the case of reverse connection, it is also necessary to interrupt a voltage twice that of a single solar power generation string.

[0068] In this case, as shown in (2) of Figure 3a, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10. This effectively reduces the current flowing through the positive switch SX1 and the negative switch SY1 corresponding to the photovoltaic string PV1, and also reduces the short-circuit or reverse connection current and tripping voltage flowing through the positive switch SX1 and the negative switch SY1 corresponding to the faulty photovoltaic string PV1. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is one times that of a single photovoltaic string, and the maximum tripping voltage in reverse connection is one times that of a single photovoltaic string. Compared to the three times tripping current and twice the tripping voltage of a single photovoltaic string, the maximum tripping current and maximum tripping voltage of the multi-pole interlocking switch are effectively reduced. As a result, the positive switch SX1 and the negative switch SY1 can be turned off more safely and reliably, and the multi-pole interlocking switch 20 can more safely and reliably shut off and isolate against faults.

[0069] After the multi-pole interlocking switch 20 is turned off, there is no parallel connection in the solar power generation string, so the solar power generation string will not be damaged.

[0070] The protection principle in the event of a short circuit or reverse connection in the photovoltaic string PV2 is the same as the protection principle in the event of a short circuit or reverse connection in the photovoltaic string PV1. Therefore, to avoid redundancy, a detailed explanation is omitted here.

[0071] When a short circuit or reverse connection occurs in the solar power generation string PV3, as can be seen by referring to the above principle, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX3 and negative switch SY2 corresponding to the solar power generation string PV3 will both need to interrupt three times the short circuit or reverse connection current of a single solar power generation string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 is three times the interrupting current of a single solar power generation string. Furthermore, in the case of a reverse connection, it is necessary to interrupt twice the interrupting voltage of a single solar power generation string. By short-circuiting the positive input terminal and negative input terminal of the power conversion unit 10, the current flowing through the positive switch SX3 and negative switch SY2 corresponding to the solar power generation string PV3 is effectively reduced. The short-circuit or reverse connection current and tripping voltage flowing through the positive switch SX3 and negative switch SY2 corresponding to the faulty solar power string PV3 are reduced. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is twice that of a single solar power string, and the maximum tripping voltage in the case of reverse connection is one times that of a single solar power string. Compared to the tripled tripping current and doubled tripping voltage of a single solar power string, the maximum tripping current and maximum tripping voltage of the multi-pole interlocking switch 20 are effectively reduced, thereby enabling the positive switch SX3 and negative switch SY2 to be turned off more safely and reliably, and allowing the multi-pole interlocking switch 20 to shut off and isolate in the event of a fault more safely and reliably.

[0072] The protection principle in the event of a short circuit or reverse connection in the PV4 solar power string is the same as the protection principle in the event of a short circuit or reverse connection in the PV3 solar power string. Therefore, to avoid redundancy, a detailed explanation is omitted here.

[0073] Furthermore, referring to Figure 3b, for example, if the solar power generation system is functioning normally, the solar power generation strings PV1 to PV4 supply the generated electricity to the power conversion unit 10 via the multi-pole interlocking switch 20.

[0074] If a malfunction occurs in the solar power generation system, for example, if a short circuit or reverse connection occurs in solar power generation string PV1, referring to (1) in Figure 3b, the currents from solar power generation strings PV2, PV3, and PV4 will flow into solar power generation string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 corresponding to solar power generation string PV1 will need to interrupt three times the short circuit or reverse connection current of a single solar power generation string, and the negative switch SY1 corresponding to solar power generation string PV1 will need to interrupt twice the short circuit or reverse connection current of a single solar power generation string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 is three times the interrupting current of a single solar power generation string, and in the case of reverse connection, it is also necessary to interrupt twice the interrupting voltage of a single solar power generation string.

[0075] In this case, as shown in (2) of Figure 3b, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10. This effectively reduces the current flowing through the positive switch SX1 and the negative switch SY1 corresponding to the photovoltaic string PV1, as well as the short-circuit or reverse connection current and tripping voltage flowing through the positive switch SX1 and the negative switch SY1 corresponding to the faulty photovoltaic string PV1. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is twice that of a single photovoltaic string, and the maximum tripping voltage in reverse connection is one times that of a single photovoltaic string. Compared to the three times tripping current and twice the tripping voltage of a single photovoltaic string, the maximum tripping current and maximum tripping voltage of the multi-pole interlocking switch are effectively reduced. As a result, the positive switch SX1 and the negative switch SY1 can be turned off more safely and reliably, and the multi-pole interlocking switch 20 can more safely and reliably shut off and isolate against faults.

[0076] After the multi-pole interlocking switch 20 is turned off, there is no parallel connection in the solar power generation string, so the solar power generation string will not be damaged.

[0077] Here, the protection principle in the event of a short circuit or reverse connection in the photovoltaic strings PV2-PV4 is the same as the protection principle in the event of a short circuit or reverse connection in the photovoltaic string PV1. To avoid redundancy, a detailed explanation is omitted here.

[0078] For protection principles of other system structures where N=4, please refer to the above; a detailed explanation is omitted here.

[0079] For example, in the case of situation 3, referring to Figure 4a, if the solar power generation system is functioning normally, the solar power strings PV1 to PV5 supply the generated electricity to the power conversion unit 10 via the multi-pole interlocking switch 20.

[0080] If a malfunction occurs in the solar power generation system, for example, when a short circuit or reverse connection occurs in solar power generation string PV1, referring to (1) in Figure 4a, the current from solar power generation strings PV2 to PV5 flows into solar power generation string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 and negative switch SY1 corresponding to solar power generation string PV1 will need to interrupt three times the short circuit or reverse connection current of a single solar power generation string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 will be three times the interrupting current of a single solar power generation string, and in the case of reverse connection, it will also need to interrupt twice the interrupting voltage of a single solar power generation string.

[0081] In this case, as shown in (2) of Figure 4a, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10. This effectively reduces the current flowing through the positive switch SX1 and the negative switch SY1 corresponding to the photovoltaic string PV1, and also reduces the short-circuit or reverse connection current and the tripping voltage flowing through the positive switch SX1 and the negative switch SY1 corresponding to the faulty photovoltaic string PV1. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is twice that of a single photovoltaic string, and the maximum tripping voltage in reverse connection is one times that of a single photovoltaic string. Compared to three times the tripping current and twice the tripping voltage of a single photovoltaic string, the maximum tripping current and maximum tripping voltage of the multi-pole interlocking switch are effectively reduced. This allows the positive switch SX1 and the negative switch SY1 to be turned off more safely and reliably, enabling the multi-pole interlocking switch 20 to more safely and reliably shut off and isolate against faults.

[0082] After the multi-pole interlocking switch 20 is turned off, solar power strings PV1 and PV2 are connected in parallel, and solar power strings PV3 and PV4 are connected in parallel. If solar power string PV1 is short-circuited or reverse-connected, the current from solar power string PV2 flows into solar power string PV1. Solar power string PV1 can withstand the current output from up to two solar power strings, and since this does not exceed the limit that solar power string PV1 can withstand, solar power string PV1 is effectively protected from damage.

[0083] The protection principle in the event of a short circuit or reverse connection in photovoltaic strings PV2-PV4 is the same as the protection principle in the event of a short circuit or reverse connection in photovoltaic string PV1. Therefore, to avoid redundancy, a detailed explanation is omitted here.

[0084] If a short circuit or reverse connection occurs in the solar power string PV5, refer to (3) in Figure 4a. Current from solar power strings PV1 to PV4 flows into solar power string PV5. If the multi-pole interlocking switch 20 is directly turned off in this case, the positive switch SX3 and negative switch SY3 corresponding to solar power string PV5 will need to interrupt four times the short circuit or reverse connection current of a single solar power string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 will be four times the interrupting current of a single solar power string. Furthermore, in the case of reverse connection, it will also need to interrupt twice the interrupting voltage of a single solar power string.

[0085] In this case, referring to (4) in Figure 4a, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10. This effectively reduces the current flowing through the positive switch SX3 and negative switch SY3 corresponding to the photovoltaic string PV5, and also reduces the short-circuit or reverse connection current and tripping voltage flowing through the positive switch SX3 and negative switch SY3 corresponding to the faulty photovoltaic string PV5. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is twice that of a single photovoltaic string, and the maximum tripping voltage in reverse connection is one times that of a single photovoltaic string. Compared to the four times tripping current and twice the tripping voltage of a single photovoltaic string, the maximum tripping current and maximum tripping voltage of the multi-pole interlocking switch are effectively reduced. As a result, the positive switch SX3 and negative switch SY3 can be turned off more safely and reliably, and the multi-pole interlocking switch 20 can more safely and reliably shut off and isolate against faults.

[0086] Furthermore, referring to Figure 4b, for example, if the solar power generation system is functioning normally, the solar power generation strings PV1 to PV5 supply the generated electricity to the power conversion unit 10 via the multi-pole interlocking switch 20.

[0087] If a malfunction occurs in the solar power generation system, for example, when a short circuit or reverse connection occurs in solar power generation string PV1, referring to (1) in Figure 4b, the current from solar power generation strings PV2 to PV5 flows into solar power generation string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 corresponding to solar power generation string PV1 needs to interrupt twice the short circuit or reverse connection current of a single solar power generation string, and the negative switch SY1 corresponding to solar power generation string PV1 needs to interrupt three times the short circuit or reverse connection current of a single solar power generation string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 is three times the interrupting current of a single solar power generation string, and in the case of reverse connection, it is also necessary to interrupt twice the interrupting voltage of a single solar power generation string.

[0088] In this case, as shown in (2) of Figure 4b, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10, thereby effectively reducing the current flowing through the negative switch SY1 corresponding to the photovoltaic string PV1, and also reducing the short-circuit or reverse connection current and tripping voltage flowing through the negative switch SY1 corresponding to the faulty photovoltaic string PV1. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is twice that of a single photovoltaic string, and the maximum tripping voltage in reverse connection is one times that of a single photovoltaic string. Compared to the three times tripping current and twice the tripping voltage of a single photovoltaic string, the maximum tripping current and maximum tripping voltage of the multi-pole interlocking switch are effectively reduced, thereby enabling the positive switch SX1 and the negative switch SY1 to be turned off more safely and reliably, and allowing the multi-pole interlocking switch 20 to shut off and isolate in the event of a fault more safely and reliably.

[0089] After the multi-pole interlocking switch 20 is turned off, the solar power strings PV1 and PV2 are connected in parallel. If solar power string PV1 is short-circuited or reverse-connected, the current from solar power string PV2 flows into solar power string PV1. Solar power string PV1 can withstand the current output from up to two solar power strings, and since this does not exceed the limit that solar power string PV1 can withstand, solar power string PV1 is effectively protected from damage.

[0090] The protection principle in the event of a short circuit or reverse connection in photovoltaic strings PV2-PV4 is the same as the protection principle in the event of a short circuit or reverse connection in photovoltaic string PV1. Therefore, to avoid redundancy, a detailed explanation is omitted here.

[0091] If a short circuit or reverse connection occurs in the solar power string PV5, refer to (3) in Figure 4b. Current from solar power strings PV1 to PV4 flows into solar power string PV5. If the multi-pole interlocking switch 20 is directly turned off in this case, the positive switch SX2 corresponding to solar power string PV5 needs to interrupt a short circuit or reverse connection current three times that of a single solar power string, and the negative switch SY3 corresponding to solar power string PV5 needs to interrupt a short circuit or reverse connection current four times that of a single solar power string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 is four times that of a single solar power string, and in the case of a reverse connection, it is also necessary to interrupt a voltage twice that of a single solar power string.

[0092] In this case, referring to (4) in Figure 4b, the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10. This effectively reduces the current flowing through the positive switch SX2 and negative switch SY3 corresponding to the photovoltaic string PV5, and also reduces the short-circuit or reverse connection current and tripping voltage flowing through the positive switch SX2 and negative switch SY3 corresponding to the faulty photovoltaic string PV5. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is three times that of a single photovoltaic string, and the maximum tripping voltage in the case of reverse connection is one times that of a single photovoltaic string. Compared to the four times tripping current and twice the tripping voltage of a single photovoltaic string, the maximum tripping current and tripping voltage of the multi-pole interlocking switch are effectively reduced. As a result, the positive switch SX2 and negative switch SY3 can be turned off more safely and reliably, and the multi-pole interlocking switch 20 can shut off and isolate in the event of a fault more safely and reliably.

[0093] For example, in the case of situation 4, referring to Figure 5, if the solar power generation system is functioning normally, the solar power strings PV1 to PV6 supply the generated electricity to the power conversion unit 10 via the multi-pole interlocking switch 20.

[0094] If a malfunction occurs in the solar power generation system, for example, when a short circuit or reverse connection occurs in solar power generation string PV1, referring to (1) in Figure 5, the current from solar power generation strings PV2 to PV6 flows into solar power generation string PV1. In this case, if the multi-pole interlocking switch 20 is directly turned off, the positive switch SX1 and negative switch SY1 corresponding to solar power generation string PV1 will need to interrupt four times the short circuit or reverse connection current of a single solar power generation string. In this case, the maximum interrupting current of the multi-pole interlocking switch 20 will be four times the interrupting current of a single solar power generation string. Furthermore, in the case of a reverse connection, it will also be necessary to interrupt twice the interrupting voltage of a single solar power generation string.

[0095] In this case, as shown in Figure 5(2), the control unit controls the switching element Q in the power conversion unit 10 to short-circuit the positive input terminal and the negative input terminal of the power conversion unit 10. This effectively reduces the current flowing through the positive switch SX1 and the negative switch SY1 corresponding to the photovoltaic string PV1, and also reduces the short-circuit or reverse connection current and the tripping voltage flowing through the positive switch SX1 and the negative switch SY1 corresponding to the faulty photovoltaic string PV1. In this case, the maximum tripping current of the multi-pole interlocking switch 20 is twice that of a single photovoltaic string, and the maximum tripping voltage in the case of reverse connection is one times that of a single photovoltaic string. Compared to the four times tripping current and twice the tripping voltage of a single photovoltaic string, the maximum tripping current and tripping voltage of the multi-pole interlocking switch are effectively reduced. As a result, the positive switch SX1 and the negative switch SY1 can be turned off more safely and reliably, and the multi-pole interlocking switch 20 can more safely and reliably shut off and isolate against faults.

[0096] After the multi-pole interlocking switch 20 is turned off, solar power strings PV1 and PV2 are connected in parallel, solar power strings PV3 and PV4 are connected in parallel, and solar power strings PV5 and PV6 are connected in parallel. When solar power string PV1 is short-circuited or reverse-connected, the current from solar power string PV2 flows into solar power string PV1. Solar power string PV1 can withstand the current output from up to two solar power strings, and since this does not exceed the limit that solar power string PV1 can withstand, solar power string PV1 is effectively protected from damage.

[0097] The protection principle in the event of a short circuit or reverse connection in photovoltaic strings PV2 to PV6 is the same as the protection principle in the event of a short circuit or reverse connection in photovoltaic string PV1. Therefore, to avoid redundancy, a detailed explanation is omitted here.

[0098] For example, in Situation 5, referring to Figure 6, the protection principle of this system is the same as that of the system in Figure 4a. Compared to Figure 4a, in this system, when a short circuit or reverse connection occurs in the photovoltaic string, the positive and negative switches corresponding to the faulty photovoltaic string can withstand a larger breaking current.

[0099] For example, if a short circuit or reverse connection occurs in the photovoltaic string PV1, directly turning off the multi-pole interlocking switch 20 would require both the positive switch SX1 and the negative switch SY1 corresponding to the photovoltaic string PV1 to interrupt five times the short circuit or reverse connection current of a single photovoltaic string, clearly indicating a higher requirement for the interruption capability of the pole switches.

[0100] Furthermore, for example, if a short circuit or reverse connection occurs in the photovoltaic string PV7, directly turning off the multi-pole interlocking switch 20 would require both the positive switch SX4 and negative switch SY4 corresponding to the photovoltaic string PV7 to interrupt six times the short circuit or reverse connection current of a single photovoltaic string, clearly indicating a higher requirement for the interruption capability of the pole switches.

[0101] The control unit controls the switching element Q of the power conversion unit 10 to turn on, thereby short-circuiting the positive and negative input terminals of the power conversion unit 10. This reduces the maximum interruption current of the multi-pole interlocking switch 20, allowing the multi-pole interlocking switch 20 to interrupt and isolate in the event of a fault more safely and reliably.

[0102] For example, in Situation 6, referring to Figure 7, the protection principle of this system is the same as that of the system in Figure 5. Compared to Figure 5, in this system, when a short circuit or reverse connection occurs in the photovoltaic string, the positive and negative switches corresponding to the faulty photovoltaic string can withstand a larger breaking current.

[0103] For example, if a short circuit or reverse connection occurs in the photovoltaic string PV1, directly turning off the multi-pole interlocking switch 20 would require both the positive switch SX1 and the negative switch SY1 corresponding to the photovoltaic string PV1 to interrupt six times the short circuit or reverse connection current of a single photovoltaic string, clearly indicating a higher requirement for the interruption capability of the pole switches.

[0104] The control unit controls the switching element Q of the power conversion unit 10 to turn on, thereby short-circuiting the positive and negative input terminals of the power conversion unit 10. This reduces the maximum interruption current of the multi-pole interlocking switch 20, allowing the multi-pole interlocking switch 20 to interrupt and isolate in the event of a fault more safely and reliably.

[0105] In the above embodiment, if a failure occurs in the photovoltaic power generation system, the switching element in the power conversion unit can be controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate in the event of a failure. After controlling the multi-pole interlocking switch to turn off, damage to the photovoltaic power generation strings can be avoided by connecting up to three of the N photovoltaic power generation strings in parallel.

[0106] In some embodiments, the number of photovoltaic strings that can be connected to each positive terminal is up to three, and / or the number of photovoltaic strings that can be connected to each negative terminal is up to three. This ensures that up to three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off, and further provides protection for the photovoltaic strings.

[0107] Specifically, if the number of solar power generation strings connected to each positive terminal is a maximum of three, even if the number of solar power generation strings connected to the negative terminal is four or more, in order to achieve parallel connection of solar power generation strings, the positive and negative terminals of the solar power generation strings must be connected in parallel so that they correspond. Therefore, if the number of solar power generation strings connected to each positive terminal is limited to a maximum of three, then after the multi-pole interlocking switch 20 is turned off, a maximum of three of the N solar power generation strings can be connected in parallel.

[0108] For example, referring to Figure 8a, three photovoltaic strings PV1, PV2, and PV3 are connected to positive terminal X1, one photovoltaic string PV4 is connected to positive terminal X2, and one photovoltaic string PV5 is connected to positive terminal X3. That is, the number of photovoltaic strings connected to each positive terminal is three or less. Also, four photovoltaic strings PV1, PV2, PV3, and PV4 are connected to negative terminal Y1, and one photovoltaic string PV5 is connected to negative terminal Y2. After the multi-pole interlocking switch 20 is turned off, the number of photovoltaic strings connected to positive terminal X1 is limited, so at this time, only photovoltaic strings PV1, PV2, and PV3 are connected in parallel, satisfying the condition that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off.

[0109] Furthermore, referring to Figure 8b, for example, two photovoltaic strings PV1 and PV2 are connected to positive terminal X1, two photovoltaic strings PV3 and PV4 are connected to positive terminal X2, and one photovoltaic string PV5 is connected to positive terminal X3. That is, the number of photovoltaic strings connected to each positive terminal is three or less. Also, four photovoltaic strings PV1, PV2, PV3 and PV4 are connected to negative terminal Y1, and one photovoltaic string PV5 is connected to negative terminal Y2. After the multi-pole interlocking switch 20 is turned off, the number of photovoltaic strings connected to positive terminal X1 is limited. In this case, photovoltaic strings PV1 and PV2, and photovoltaic strings PV3 and PV4 are connected in parallel, satisfying the condition that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off.

[0110] For other situations, please refer to the above, and we will omit detailed explanations here.

[0111] Similarly, when the number of photovoltaic strings connected to each negative terminal is a maximum of 3, and when the number of photovoltaic strings connected to each positive terminal is a maximum of 3, and the number of photovoltaic strings connected to each negative terminal is a maximum of 3, in both cases it is possible to satisfy the condition that a maximum of 3 of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off. A detailed explanation is omitted here.

[0112] In the above embodiment, by limiting the number of photovoltaic strings connected to each connection end, it is easy to ensure that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch is turned off, and furthermore, the photovoltaic strings can be protected.

[0113] Furthermore, when limiting the number of photovoltaic strings connected to each connection terminal, in some embodiments, the negative terminals of multiple photovoltaic strings that can be connected to the same positive terminal are connected to at least two negative terminals, respectively. In this way, after the multi-pole interlocking switch 20 is turned off, the number of photovoltaic strings connected in parallel out of the N photovoltaic strings can be reduced, and it can be easily achieved that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch is turned off.

[0114] Specifically, in some situations, multiple, for example, two, three, or more photovoltaic strings may be connected to the same positive terminal. In this case, the negative terminals of the multiple photovoltaic strings connected to the positive terminal can be separated and connected to two or more negative terminals. To achieve parallel connection of photovoltaic strings, it is necessary to connect the positive and negative terminals of the photovoltaic strings in parallel so that they correspond. Therefore, by separating the negative terminals of multiple photovoltaic strings connected to the same positive terminal and connecting them to different negative terminals, the number of photovoltaic strings connected in parallel can be reduced after the multi-pole interlocking switch 20 is turned off.

[0115] For example, referring to Figure 9a, three photovoltaic strings PV1, PV2, and PV3 are connected to the positive terminal X1. At the same time, the negative terminals of photovoltaic strings PV1 and PV2 are connected to the negative terminal Y1, and the negative terminal of photovoltaic string PV3 is connected to the negative terminal Y2. After the multi-pole interlocking switch 20 is turned off, the negative terminals of two of the three photovoltaic strings PV1 and PV2 connected to the positive terminal X1 are connected to the negative terminal Y1, and the negative terminal of one photovoltaic string PV3 is connected to the negative terminal Y2. In this case, only photovoltaic strings PV1 and PV2 are connected in parallel, and the number of photovoltaic modules connected in parallel is reduced compared to before disassembly. In this way, after the multi-pole interlocking switch 20 is turned off, the condition is not only met that a maximum of three of the N photovoltaic strings are connected in parallel, but the current flowing into a faulty photovoltaic string is further reduced, improving the safety of the photovoltaic strings.

[0116] Furthermore, referring to Figure 9b, for example, four photovoltaic strings PV1, PV2, PV3, and PV4 are connected to the positive terminal X1. At the same time, the negative terminals of photovoltaic strings PV1 and PV2 are connected to the negative terminal Y1, and the negative terminals of photovoltaic strings PV3 and PV4 are connected to the negative terminal Y2. After the multi-pole interlocking switch 20 is turned off, the negative terminals of two of the four photovoltaic strings PV1 and PV2 connected to the positive terminal X1 are connected to the negative terminal Y1, and the negative terminals of the two photovoltaic strings PV3 and PV4 are connected to the negative terminal Y2. In this case, photovoltaic strings PV1 and PV2 are connected in parallel, and photovoltaic strings PV3 and PV4 are connected in parallel. Compared to before disassembly, the number of photovoltaic modules connected in parallel is reduced, satisfying the condition that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off.

[0117] For other situations, please refer to the above, and we will omit detailed explanations here.

[0118] In the above embodiment, the negative electrodes of multiple photovoltaic strings connected to the same positive terminal are connected to at least two negative terminals, making it easy to ensure that up to three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch is turned off, and further protecting the photovoltaic strings.

[0119] In some embodiments, if four or more photovoltaic strings can be connected to any one positive terminal, the negative terminals of at least two of these four or more photovoltaic strings are connected to two negative terminals, and the maximum number of photovoltaic strings that can be connected to the same negative terminal is three.

[0120] Specifically, in order to achieve parallel connection of solar power strings, it is necessary to connect the positive and negative poles of the solar power strings in parallel so that they correspond to each other. Therefore, if there are too many solar power strings connected to any one positive terminal, for example, four or more, the connection of solar power strings is limited by the negative terminals. For example, at least two negative terminals are used to connect to solar power strings connected to the same positive terminal, and the number of solar power strings connected to the same negative terminal is limited to a maximum of three. As a result, after the multi-pole interlocking switch 20 is turned off, a maximum of three of the N solar power strings are connected in parallel.

[0121] For example, referring to Figure 10a, four photovoltaic strings PV1, PV2, PV3, and PV4 are connected to the positive terminal X1. Simultaneously, the negative terminals of photovoltaic strings PV1, PV2, and PV3 are connected to the negative terminal Y1, and the negative terminal of photovoltaic string PV4 is connected to the negative terminal Y2. After the multi-pole interlocking switch 20 is turned off, the negative terminals of three of the four photovoltaic strings PV1, PV2, and PV3 connected to the positive terminal X1 are connected to the negative terminal Y1, and the negative terminal of one photovoltaic string PV4 is connected to the negative terminal Y2. In this case, photovoltaic strings PV1, PV2, and PV3 are connected in parallel, satisfying the condition that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off.

[0122] Furthermore, referring to Figure 10b, for example, five photovoltaic strings PV1, PV2, PV3, PV4, and PV5 are connected to the positive terminal X1, and simultaneously, the negative terminal of each photovoltaic string is connected to one negative terminal. After the multi-pole interlocking switch 20 is turned off, the negative terminals of the five photovoltaic strings PV1, PV2, PV3, PV4, and PV5 connected to the positive terminal X1 are connected to different negative terminals. In this case, there are no photovoltaic strings connected in parallel, and the condition that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch 20 is turned off is met.

[0123] Similarly, in some embodiments, if there are four or more photovoltaic strings that can be connected to any one negative terminal, the positive terminals of at least two of these four or more photovoltaic strings are connected to two positive terminals, and the maximum number of photovoltaic strings that can be connected to the same positive terminal is three. Similarly, it is easy to ensure that up to three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch is turned off, and furthermore, protection of the photovoltaic strings can be achieved. For specifics, please refer to the above, and a detailed explanation is omitted here.

[0124] In the above embodiment, if there are four or more photovoltaic strings that can be connected to any one positive terminal, the number of photovoltaic strings connected to the negative terminal can be limited, or if there are four or more photovoltaic strings that can be connected to any one negative terminal, the number of photovoltaic strings connected to the positive terminal can be limited, thereby easily ensuring that a maximum of three of the N photovoltaic strings are connected in parallel after the multi-pole interlocking switch is turned off, and furthermore, the photovoltaic strings can be protected.

[0125] In some embodiments, the control unit further obtains at least one of the current values ​​of the branch circuits where each photovoltaic string is located, the branch circuits where each pole switch is located, and the DC bus after the positive and negative input terminals of the power conversion unit 10 are short-circuited, and controls the multi-pole interlocking switch 20 to turn off if it determines that the generated current of the photovoltaic system is less than a first predetermined value based on at least one of the current values ​​of the branch circuits where each photovoltaic string is located, the branch circuits where each pole switch is located, and the DC bus.

[0126] A branch circuit refers to a path through which branch currents flow in a parallel circuit. Referring to Figure 11a, the circuit in which the solar power generation string PV1 is located is called a branch circuit, the circuit formed after solar power generation strings PV1 and PV2 are connected in parallel is called a branch circuit, and the circuit in which the positive switch SX1 is located is also called a branch circuit. The circuit between the multi-pole interlocking switch 20 and the power conversion unit 10 is called a DC bus. The first predetermined value may be calibrated according to the actual situation, and is not specifically limited here.

[0127] Specifically, after the positive and negative input terminals of the power conversion unit 10 are short-circuited, the current generated by the photovoltaic power generation system is first determined, and if the current generated is small, the multi-pole interlocking switch 20 is controlled to turn off, thereby further improving the safety and reliability when the multi-pole interlocking switch 20 is turned off. There are many ways to determine whether the current generated by the photovoltaic power generation system is smaller than a first predetermined value. For example, it may be determined based on the current value of the branch circuit where the photovoltaic power generation string is located, the current value of the branch circuit where the pole switch is located, the current value of the DC bus, or a combination of these three current values. The specific method is not limited here.

[0128] For example, referring to Figure 11a, after the positive and negative input terminals of the power conversion unit 10 are short-circuited, the current values ​​of the branch circuits where each photovoltaic string is located, for example, the current values ​​of the branch circuits where photovoltaic strings PV1 to PV5 are located, are obtained, and the sum of these current values ​​is calculated to obtain the generated current of the photovoltaic system. Alternatively, the current values ​​of the branch circuits where each pole switch is located, for example, the current values ​​of the branch circuits where the positive pole switches SX1, SX2, and SX3 are located, are obtained, and the sum of these current values ​​is calculated to obtain the generated current of the photovoltaic system. Alternatively, the current value of the DC bus is obtained to obtain the generated current of the photovoltaic system. When the generated current is smaller than a first predetermined value, that is, when the current flowing into the multi-pole interlocking switch 20 is small, the control unit controls the multi-pole interlocking switch 20 to turn off, further improving safety and reliability when the multi-pole interlocking switch 20 is turned off.

[0129] In the above embodiment, after short-circuiting the positive and negative input terminals of the power conversion unit, if it is determined that the generated current of the solar power generation system is small, the multi-pole interlocking switch is controlled to turn off, thereby further improving the safety and reliability when the multi-pole interlocking switch is turned off.

[0130] In some embodiments, the control unit further acquires the illuminance after the positive and negative input terminals of the power conversion unit 10 are short-circuited, and controls the multi-pole interlocking switch 20 to turn off if the illuminance is less than a predetermined intensity value.

[0131] Illuminance is obtained using a light sensor or similar device. The predetermined intensity value may be calibrated according to the actual conditions, and is not specifically limited here.

[0132] Specifically, after the positive and negative input terminals of the power conversion unit 10 are short-circuited, the current illuminance is first acquired. If the illuminance is low, the current generated by the corresponding photovoltaic power generation system is low, and therefore the current flowing through the multi-pole interlocking switch 20 is low. By controlling the multi-pole interlocking switch 20 to turn off in this way, the safety and reliability of the multi-pole interlocking switch 20 can be further improved.

[0133] In the above embodiment, after the positive and negative input terminals of the power conversion unit are short-circuited, if the illuminance is low, the multi-pole interlocking switch is controlled to turn off. This further improves the safety and reliability of the multi-pole interlocking switch when it turns off due to low illuminance, low generated current from the corresponding solar power generation system, and low current flowing through the multi-pole interlocking switch.

[0134] In some embodiments, the fault protection device further includes a parameter detection unit, which detects at least one of the parameter values ​​of the branch circuit in which each solar power string is located, the parameter values ​​of the branch circuit in which each pole switch is located, and the parameter values ​​of the DC bus. Based on this, the control unit detects that the solar power system has failed.

[0135] The failure may include a short-circuit failure or a reverse connection failure. Parameter values ​​include voltage values, current values, temperature values, or power values, and for example, it is determined whether a short-circuit or reverse connection failure has occurred in the solar power generation system based on the current value, temperature value, or power value of the branch circuit in which each solar power generation string is located, and for example, it is determined whether a short-circuit or reverse connection failure has occurred in the solar power generation system based on the current value, temperature value, or power value of the branch circuit in which each pole switch is located, and for example, it is determined whether a short-circuit or reverse connection failure has occurred in the solar power generation system based on the voltage value, current value, or temperature value of the DC bus.

[0136] For example, during the operation of a solar power generation system, the parameter detection unit can acquire parameter values, such as current values, of the branch circuits in which each solar power generation string is located in real time. Under normal circumstances, the current value of the branch circuit in which each solar power generation string is located is the output current when that solar power generation string is operating normally. If a short circuit or reverse connection occurs in a solar power generation string, the output current of the other solar power generation strings flows back into the faulty solar power generation string, increasing the current value of the faulty solar power generation string, and at the same time, the current reverses direction. Therefore, it is possible to easily and accurately determine whether a fault has occurred in the solar power generation system based on the current value of the faulty solar power generation string.

[0137] For illustrative purposes, referring to (1) in Figure 11b, under normal circumstances, the current value in the branch circuit where each solar power string is located is the output current when the solar power string is operating normally. If a short circuit or reverse connection occurs in solar power string PV1, referring to (2) in Figure 11b, the output currents of solar power strings PV2 to PV5 flow back into solar power string PV1, and the current in the branch circuit where solar power string PV1 is located increases to four times the short circuit or reverse connection current of a single solar power string, and the direction of the current is opposite to that of normal operation. Therefore, based on the detected current value in the branch circuit where solar power string PV1 is located, it can be determined that a short circuit or reverse connection fault currently exists in the solar power system.

[0138] Furthermore, for example, during the operation of a solar power generation system, the parameter detection unit acquires parameter values, such as current values, of the branch circuits where each pole switch is located in real time. Under normal circumstances, the current value of the branch circuit where each pole switch is located is the output current or the sum of the output currents of the connected solar power generation strings. If a short circuit or reverse connection occurs in the solar power generation string, the current in the branch circuit where the corresponding pole switch is located increases and in the reverse direction. Therefore, based on the current value of the pole switch, it is possible to easily and accurately determine whether a fault has occurred in the solar power generation system.

[0139] Illustratively, referring to (1) in Figure 11b, under normal circumstances, the current value in the branch circuit where the positive switch SX1 and negative switch SY1 are located is the sum of the output currents of photovoltaic strings PV1 and PV2, the current value in the branch circuit where the positive switch SX2 and negative switch SY2 are located is the sum of the output currents of photovoltaic strings PV3 and PV4, and the current value in the branch circuit where the positive switch SX3 and negative switch SY3 are located is the output current of photovoltaic string PV5. If a short circuit or reverse connection occurs in photovoltaic string PV1, referring to (2) in Figure 11b, the current value flowing through the branch circuit where the positive switch SX1 and negative switch SY1 are located is the sum of the output currents of photovoltaic strings PV3, PV4 and PV5, the current value increases, and the direction of the current is opposite to that of normal. Therefore, based on the detected current value in the branch circuit where the positive switch SX1 or negative switch SY1 is located, it can be determined that a short circuit or reverse connection fault currently exists in the photovoltaic system.

[0140] Furthermore, for example, during the operation of a solar power generation system, the parameter detection unit acquires the current value of the DC bus in real time. Under normal circumstances, the current value of the DC bus is the sum of the output currents of the N solar power generation strings. If a short circuit or reverse connection occurs in the solar power generation strings, the current flowing through the DC bus is small, so it is possible to easily and accurately determine whether a fault has occurred in the solar power generation system based on the current value of the DC bus.

[0141] For illustrative purposes, referring to (1) in Figure 11b, under normal circumstances, the current value of the DC bus is the sum of the output currents of the five photovoltaic strings. If a short circuit or reverse connection occurs in photovoltaic string PV1, referring to (2) in Figure 11b, the output currents of photovoltaic strings PV2 to PV5 flow back into photovoltaic string PV1 via the multi-pole interlocking switch 20, and the current flowing through the DC bus becomes very small. Therefore, based on the detected current value of the DC bus, it can be determined that a short circuit or reverse connection fault currently exists in the photovoltaic system.

[0142] In the above embodiment, by detecting one or more of the parameter values ​​of the branch circuit where the solar power generation string is located, the parameter values ​​of the branch circuit where the pole switch is located, and the parameter values ​​of the DC bus, it is possible to easily and accurately detect whether a fault has occurred in the solar power generation system, and there are many detection methods.

[0143] In some embodiments, the parameter detection unit includes at least one of a first current sensor and a second current sensor. The first current sensor detects first current information of any one of the branch circuits where a solar power generation string is located and transmits the first current information to the control unit. The second current sensor detects second current information of any one of the branch circuits where a pole switch is located and transmits the second current information to the control unit. Here, "any one" means that the sensors provided in each branch circuit are not distinguished.

[0144] For example, referring to Figures 11a to 11b, a first current sensor 31 is provided in the branch circuit where each solar power generation string is located. Specifically, a first current sensor 31 is provided at the positive electrode of each solar power generation string. The first current sensor 31 acquires current information from the branch circuit where the corresponding solar power generation string is located, records this information as the first current information, and transmits the first current information, including the current value and current direction, to the control unit.

[0145] Alternatively, a second current sensor 32 is provided in the branch circuit where each pole switch is located. Specifically, a second current sensor 32 is provided in the branch circuit where each positive pole switch is located. The second current sensor 32 acquires current information from the branch circuit where the corresponding pole switch is located, records this information as the second current information, and transmits the second current information, including the current value and current direction, to the control unit.

[0146] Alternatively, a first current sensor 31 is provided in the branch circuit where each solar power generation string is located, and a second current sensor 32 is provided in the branch circuit where each pole switch is located. The first current sensor 31 and the second current sensor 32 acquire first current information and second current information, and transmit them to the control unit.

[0147] The control unit further detects a failure in the solar power generation system if it determines, based on the first current information, that the current direction of the branch circuit where the solar power generation string is located is opposite to the set direction, or if it determines, based on the second current information, that the current direction of the branch circuit where the pole switch is located is opposite to the set direction, or if it determines, based on the first current information, that the current direction of the branch circuit where the solar power generation string is located is opposite to the set direction, AND if it determines, based on the second current information, that the current direction of the branch circuit where the pole switch corresponding to the solar power generation string is located is opposite to the set direction, it detects a failure in the solar power generation system.

[0148] In other words, the control unit can determine whether a malfunction has occurred in the solar power generation system based on the current direction of the branch circuit where the solar power generation string is located, or the current direction of the branch circuit where the pole switch is located, or the current direction of both the branch circuit where the solar power generation string is located and the branch circuit where the pole switch is located.

[0149] For illustrative purposes, referring to (1) in Figure 11b, under normal circumstances, the current direction in the branch circuit where each solar power generation string is located, and the current direction in the branch circuit where each polar switch is located, are shown as indicated by the arrows in the diagram. If a short circuit or reverse connection occurs in solar power generation string PV1, referring to (2) in Figure 11b, the output current of solar power generation strings PV2 to PV5 flows back into solar power generation string PV1, thereby changing the current direction in the branch circuit where solar power generation string PV1 is located, and the branch circuit where the positive polar switch SX1 and negative polar switch SY1 corresponding to solar power generation string PV1 are located. The current direction is reversed from the normal direction, and therefore, based on the first current information, it is determined that the current direction of the branch circuit where the solar power generation string PV1 is located is reversed from the set direction, or based on the second current information, it is determined that the current direction of the branch circuit where the positive switch SX1 is located is reversed from the set direction, or based on the first current information, it is determined that the current direction of the branch circuit where the solar power generation string PV1 is located is reversed from the set direction, and based on the second current information, it is determined that the current direction of the branch circuit where the positive switch SX1 is located is reversed from the set direction, in which case it is determined that a fault has occurred in the solar power generation system.

[0150] In the above embodiment, it is possible to easily and accurately detect whether a malfunction has occurred in the solar power generation system based on the detected current direction.

[0151] The control unit further detects a failure in the solar power generation system if it determines, based on first current information, that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, or if it determines, based on second current information, that the absolute value of the current in the branch circuit where the pole switch is located is greater than a second predetermined current threshold, or if it determines, based on first current information, that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, and based on second current information, it determines, that the absolute value of the current in the branch circuit where the pole switch corresponding to the solar power generation string is located is greater than a second predetermined current threshold, and detects a failure in the solar power generation system.

[0152] In other words, the control unit determines whether a malfunction has occurred in the solar power generation system based on the magnitude of the current in the branch circuit where the solar power generation string is located, or the magnitude of the current in the branch circuit where the pole switch is located, or the magnitude of the current in both the branch circuit where the solar power generation string is located and the branch circuit where the pole switch is located.

[0153] For illustrative purposes, referring to (1) in Figure 11b, under normal circumstances, the current value of the branch circuit where each solar power generation string is located is the output current when the solar power generation string is operating normally; the current value of the branch circuit where the positive switch SX1 is located is the sum of the output currents of solar power generation strings PV1 and PV2; the current value of the branch circuit where the positive switch SX2 is located is the sum of the output currents of solar power generation strings PV3 and PV4; and the current value of the branch circuit where the positive switch SX3 is located is the output current of solar power generation string PV5.

[0154] If a short circuit or reverse connection occurs in the photovoltaic string PV1, refer to (2) in Figure 11b. The output currents of photovoltaic strings PV2 to PV5 will flow back into photovoltaic string PV1, and the current in the branch circuit where photovoltaic string PV1 is located will increase to four times the short-circuit or reverse connection current of a single photovoltaic string. The current value flowing through the branch circuit where the positive switch SX1 is located will be the sum of the output currents of photovoltaic strings PV3, PV4, and PV5, and the current value will increase. Therefore, based on the first current value, the photovoltaic string PV If it is determined that the absolute value of the current in the branch circuit where 1 is located is greater than the first predetermined current threshold, or if, based on the second current information, it is determined that the absolute value of the current in the branch circuit where the positive switch SX1 is located is greater than the second predetermined current threshold, or if, based on the first current value, it is determined that the absolute value of the current in the branch circuit where the solar power generation string PV1 is located is greater than the first predetermined current threshold, and based on the second current information, it is determined that the absolute value of the current in the branch circuit where the positive switch SX1 is located is greater than the second predetermined current threshold, then it is determined that a fault has occurred in the solar power generation system.

[0155] In the above embodiment, it is possible to easily and accurately detect whether a malfunction has occurred in the solar power generation system based on the magnitude of the detected current.

[0156] In some embodiments, the parameter detection unit further includes a first voltage sensor that detects the voltage value of the DC bus and transmits the DC bus voltage value to the control unit.

[0157] For example, referring to Figures 11a to 11b, a first voltage sensor 33 is provided on the DC bus. Specifically, the first voltage sensor 33 is provided between the positive input terminal and the negative input terminal of the power conversion unit 10, and the first voltage sensor 33 can detect the voltage value of the DC bus and transmit it to the control unit.

[0158] The control unit further detected that a fault had occurred in the solar power generation system if the voltage of the DC bus was lower than a first predetermined voltage threshold.

[0159] In other words, the control unit determines whether a malfunction has occurred in the solar power generation system based on the magnitude of the DC bus voltage.

[0160] For illustrative purposes, referring to (1) in Figure 11b, under normal circumstances, the DC bus voltage is the voltage after the five photovoltaic strings are connected in parallel. If a short circuit or reverse connection occurs in photovoltaic string PV1, referring to (2) in Figure 11b, the output currents of photovoltaic strings PV2 to PV5 flow back into photovoltaic string PV1 via the multi-pole interlocking switch 20, resulting in very little current flowing through the DC bus and a very low DC bus voltage. Therefore, if it is determined that the DC bus voltage is lower than a first predetermined voltage threshold, it is determined that a fault has occurred in the photovoltaic system.

[0161] In the above embodiment, it is possible to easily and accurately detect whether a malfunction has occurred in the solar power generation system based on the magnitude of the detected voltage.

[0162] The control unit further detects a fault in the solar power generation system if it determines, based on the first current information, that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold and the voltage of the DC bus is less than a first predetermined voltage threshold, or if it determines, based on the second current information, that the absolute value of the current in the branch circuit where the pole switch is located is greater than a second predetermined current threshold and the voltage of the DC bus is less than a first predetermined voltage threshold.

[0163] In other words, the control unit determines whether a fault has occurred in the solar power generation system based on the magnitude of the current in the branch circuit where the solar power generation string is located and the magnitude of the DC bus voltage, or based on the magnitude of the current in the branch circuit where the pole switch is located and the magnitude of the DC bus voltage.

[0164] For illustrative purposes, referring to (1) in Figure 11b, under normal circumstances, the current value in the branch circuit where each solar power string is located is the output current when the solar power string is operating normally; the current value in the branch circuit where the positive switch SX1 is located is the sum of the output currents of solar power strings PV1 and PV2; the current value in the branch circuit where the positive switch SX2 is located is the sum of the output currents of solar power strings PV3 and PV4; the current value in the branch circuit where the positive switch SX3 is located is the output current of solar power string PV5; and the DC bus voltage is the voltage after the five solar power strings are connected in parallel.

[0165] If a short circuit or reverse connection occurs in the solar power string PV1, refer to (2) in Figure 11b. The output currents of solar power strings PV2 to PV5 will flow back into solar power string PV1, increasing the current in the branch circuit where solar power string PV1 is located to four times the short-circuit or reverse connection current of a single solar power string. The current value flowing through the branch circuit where the positive switch SX1 is located is the sum of the output currents of solar power strings PV3, PV4, and PV5, and this current value will be large. On the other hand, the current flowing through the DC bus will be very small, and the voltage of the DC bus will be very small. Therefore, based on the first current information, it is determined that the absolute value of the current in the branch circuit where solar power string PV1 is located is greater than a first predetermined current threshold, and the voltage of the DC bus is less than a first predetermined voltage threshold. Alternatively, based on the second current information, it is determined that the absolute value of the current in the branch circuit where the positive switch SX1 is located is greater than a second predetermined current threshold, and the voltage of the DC bus is less than a first predetermined voltage threshold. In such cases, it is determined that a fault has occurred in the solar power system.

[0166] In the above embodiment, it is possible to easily and accurately detect whether a malfunction has occurred in the solar power generation system based on the detected current and voltage magnitudes.

[0167] In some embodiments, the parameter detection unit further includes a third current sensor that detects current information of the DC bus and transmits the current information of the DC bus to the control unit.

[0168] For example, referring to Figures 11a to 11b, a third current sensor 34 is provided on the DC bus. Specifically, the third current sensor 34 is provided on the positive DC bus, and the third current sensor 34 can detect current information of the DC bus containing the current value and transmit it to the control unit.

[0169] The control unit further determines the absolute value of the current in the branch circuit where any one of the solar power generation strings is located based on the first current information, determines the absolute value of the current in the DC bus based on the current information of the DC bus, and if the absolute value of the current in the branch circuit where any one of the solar power generation strings is located is greater than the absolute value of the current in the DC bus, it detects that a fault has occurred in the solar power generation system, or determines the absolute value of the current in the branch circuit where any one of the pole switches is located based on the second current information, determines the absolute value of the current in the DC bus based on the current information of the DC bus, and if the absolute value of the current in the branch circuit where any one of the pole switches is located is greater than the absolute value of the current in the DC bus If the absolute value of the current in the branch circuit where any one of the solar power generation strings is located is greater than the absolute value of the current in the DC bus, and the absolute value of the current in the branch circuit where any one of the pole switches is located is greater than the absolute value of the current in the DC bus, then a fault in the solar power generation system is detected.

[0170] In other words, the control unit determines whether a malfunction has occurred in the solar power generation system based on the relationship between the magnitude of the current in the branch circuit where the solar power generation string is located and the magnitude of the DC bus current, or the relationship between the magnitude of the current in the branch circuit where the pole switch is located and the magnitude of the DC bus current, or the relationship between the magnitude of the current in the branch circuit where the solar power generation string is located and the magnitude of the DC bus current, and the relationship between the magnitude of the current in the branch circuit where the pole switch is located and the magnitude of the DC bus current.

[0171] For illustrative purposes, referring to (1) in Figure 11b, under normal circumstances, the current value of the branch circuit in which each solar power string is located is the output current when that solar power string is operating normally, the current of the branch circuit in which each pole switch is located is the output current or the sum of the output currents of the solar power strings connected to it, and the current value of the DC bus is the sum of the output currents of the five solar power strings. If a short circuit or reverse connection occurs in the solar power string PV1, refer to (2) in Figure 11b, and the output currents of solar power strings PV2 to PV5 flow back into solar power string PV1, the current in the branch circuits where each solar power string and each pole switch is located is at least 1 times the output current of the solar power string, the current flowing through the DC bus is very small, and this current is smaller than 1 times the output current of the solar power string, therefore, based on the first current information, it is determined that the absolute value of the current in the branch circuits where each solar power string is located is greater than the absolute value of the current of the DC bus, or based on the second current information, it is determined that the absolute value of the current in the branch circuits where each pole switch is located is greater than the absolute value of the current of the DC bus, or based on the first current information, it is determined that the absolute value of the current in the branch circuits where each solar power string is located is greater than the absolute value of the current of the DC bus, and based on the second current information, it is determined that the absolute value of the current in the branch circuits where each pole switch is located is greater than the absolute value of the current of the DC bus, then it is determined that a fault has occurred in the solar power system.

[0172] In the above embodiment, it is possible to easily and accurately detect whether a malfunction has occurred in the solar power generation system based on the magnitude of the detected current.

[0173] Furthermore, the above explanation will mainly be based on the system structures shown in Figures 11a and 11b, describing how the control unit determines whether a malfunction has occurred in the solar power generation system and whether to control the multi-pole interlocking switch to turn off based on the illuminance or current value. However, these methods are not limiting, and these methods may be applied to all system structures related to this disclosure. A detailed explanation will be omitted here.

[0174] As described above, according to the fault protection device for a photovoltaic power generation system of the embodiment of this disclosure, when a fault occurs in the photovoltaic power generation system, the switching element in the power conversion unit is controlled to short-circuit the positive input terminal and the negative input terminal of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate against faults, and after the multi-pole interlocking switch is turned off, up to three of the N photovoltaic power generation strings are connected in parallel, thereby improving the safety of the photovoltaic power generation strings.

[0175] In some embodiments, a combiner box 200 is further provided. Referring to Figure 12, the combiner box 200 includes the fault protection device 100, which, in the event of a fault in the photovoltaic power generation system, short-circuits the positive and negative input terminals of the power conversion unit 10, thereby disconnecting the N photovoltaic strings PV1, PV2, ..., PVN from the power conversion unit 10, so that up to three of the N photovoltaic strings PV1, PV2, ..., PVN are connected in parallel.

[0176] In some examples, the combiner box 200 further includes a power conversion unit 10, which may be a DC / DC converter, but is not limited to this. For further details regarding the fault protection device 100, please refer to the above explanation, and a detailed explanation will be omitted here.

[0177] According to the combiner box of the embodiment of the present disclosure, if a fault occurs in the photovoltaic power generation system based on the fault protection device described above, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate from faults, and after the multi-pole interlocking switch is turned off, up to three of the N photovoltaic power generation strings are connected in parallel, thereby improving the safety of the photovoltaic power generation strings.

[0178] In some embodiments, an inverter 300 is further provided. Referring to Figure 13, the inverter 300 may include the fault protection device 100 and the power conversion unit 10. The power conversion unit 10 includes a DC / AC converter 11, which converts the DC power output from N photovoltaic strings PV1, PV2, ..., PVN to output AC power via the DC / AC converter 11. When a fault occurs in the photovoltaic system, the fault protection device 100 short-circuits the positive and negative input terminals of the power conversion unit 10, disconnecting the N photovoltaic strings PV1, PV2, ..., PVN from the power conversion unit 10, so that up to three of the N photovoltaic strings PV1, PV2, ..., PVN are connected in parallel.

[0179] In some examples, please refer to Figure 13, where the power conversion unit 10 includes a DC / AC converter 11, or the power conversion unit 10 includes a DC / DC converter and a DC / AC converter 11. For the relevant explanation of the fault protection device 100, please refer to the above, and a detailed explanation will be omitted here.

[0180] According to the inverter of the embodiment of this disclosure, when a fault occurs in the photovoltaic power generation system based on the fault protection device described above, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate from faults, and after the multi-pole interlocking switch is turned off, up to three of the N photovoltaic power generation strings are connected in parallel, thereby improving the safety of the photovoltaic power generation strings.

[0181] In some embodiments, a photovoltaic power generation system 400 is further provided. Referring to Figure 14, the photovoltaic power generation system 400 includes the fault protection device 100 and other components, for example, the photovoltaic power generation system 400 further includes N photovoltaic strings PV1, PV2, ..., PVN and a power conversion unit 10, etc. If a fault occurs in the photovoltaic power generation system 400, the fault protection device 100 short-circuits the positive and negative input terminals of the power conversion unit 10, thereby disconnecting the N photovoltaic strings PV1, PV2, ..., PVN from the power conversion unit 10, so that up to three of the N photovoltaic strings PV1, PV2, ..., PVN are connected in parallel.

[0182] As described above, the fault protection device 100 includes a multi-pole interlocking switch 20 and a control unit. The control unit controls the multi-pole interlocking switch 20 to turn it off, thereby disconnecting the N photovoltaic strings PV1, PV2, ..., PVN from the power conversion unit 10, so that a maximum of three of the N photovoltaic strings PV1, PV2, ..., PVN are connected in parallel.

[0183] Although the above examples were explained using the assumption that there is only one multi-pole interlocking switch 20, in some embodiments there may be two or more multi-pole interlocking switches 20. For example, as shown in Figure 15, there are six multi-pole interlocking switches 20 (only two are shown in the drawing).

[0184] In some embodiments, when there are multiple multi-pole interlocking switches 20, each of the multiple multi-pole interlocking switches 20 is connected in parallel to the positive input terminal and the negative input terminal of the power conversion unit 10, and the control unit further determines the fault type of the photovoltaic power generation system 400 and controls some or all of the multiple multi-pole interlocking switches 20 to turn off based on the fault type of the photovoltaic power generation system 400.

[0185] Specifically, the possibility of some or all of the multiple multi-pole interlocking switches 20 being turned off could be that only some of the multiple multi-pole interlocking switches 20 are turned off, or that all of the multiple multi-pole interlocking switches 20 are turned off, and this may be determined specifically based on the fault detection results and actual needs.

[0186] For example, if a fault is detected in the solar power generation system 400 based on safety considerations, all of the multiple multi-pole interlocking switches 20 are controlled to turn off. If a fault is detected in the solar power generation system 400 based on the fault detection result, some of the multiple multi-pole interlocking switches 20 are controlled to turn off, while the remaining multi-pole interlocking switches 20 are maintained in their current state. This ensures that the solar power generation system 400 can continue to supply power and guarantees the reliability of the power supply.

[0187] When controlling some of the multiple multi-pole interlocking switches 20 to turn off based on fault detection results, various situations can arise. For example, if cost is not a consideration, a first current sensor is provided at the positive and negative terminals of each solar power generation string. The first current sensor detects the solar power generation string where a reverse connection fault or short-circuit fault has occurred, and further controls the multi-pole interlocking switch 20 corresponding to that solar power generation string to turn off.

[0188] Considering costs and other factors, it is possible that only the positive terminal of each solar power generation string will be equipped with a first current sensor. However, based on the first current sensor, it may not be possible to detect solar power generation strings with short-circuit faults, but only those with reverse connection faults. In this case, first, it is determined whether a reverse connection fault or a short-circuit fault has occurred in the solar power generation system 400. Specifically, based on voltage, for example, when a reverse connection fault occurs, the pole switch corresponding to the solar power generation string can withstand twice the reverse connection voltage of a single solar power generation string, and based on this voltage, it is possible to detect that a reverse connection fault has occurred in the solar power generation system 400. If it is determined that a reverse connection fault has occurred in the solar power generation system 400, the solar power generation string with the reverse connection fault is determined based on the current detected by the first current sensor, and further, the multi-pole interlocking switch 20 corresponding to that solar power generation string is controlled to turn off. If it is determined that a short-circuit fault has occurred in the photovoltaic power generation system 400, the photovoltaic power generation string in which the short-circuit fault occurred cannot be determined based on the current detected by the first current sensor. Therefore, all of the multiple multi-pole interlocking switches 20 are controlled to turn off. For example, referring to Figure 15, if the positive electrode PV1+ of photovoltaic power generation string PV1 is grounded, the current of the negative electrode PV1- of photovoltaic power generation string PV1 cannot be detected. Therefore, it is not possible to determine whether the negative electrode PV1- of photovoltaic power generation string PV1 is grounded. It is possible that the negative electrode PV1- of photovoltaic power generation string PV1 is grounded, or that the negative electrode PV26- of another photovoltaic power generation string, for example, photovoltaic power generation string PV26, is grounded. Therefore, it is not possible to specifically determine which photovoltaic power generation string is grounded and in which the short-circuit fault occurred. Consequently, it is necessary to control all of the multiple multi-pole interlocking switches 20 to turn off.

[0189] Thus, in some failure scenarios, some of the system's solar power strings can continuously supply the electricity they generate to the power conversion unit via a multi-pole interlocking switch, thereby allowing the solar power system to be used continuously.

[0190] In some embodiments, the control unit further controls the multi-pole interlocking switch 20 corresponding to the reverse-connected branch circuit among the multiple multi-pole interlocking switches 20 to turn off if the fault type of the photovoltaic power generation system 400 is a reverse connection fault. In other words, if the fault type is a reverse connection fault, it allows some of the photovoltaic power generation strings to continuously supply electricity generated to the power conversion unit 10, thereby enabling continuous use of the photovoltaic power generation system 400.

[0191] For example, referring to Figure 15, if a reverse connection fault occurs in the photovoltaic string PV1, the control unit determines that a reverse connection fault has occurred in the photovoltaic system 400 based on the voltage of the positive switch SX1 corresponding to the photovoltaic string PV1. In this case, the control unit controls the multi-pole interlocking switch 20 corresponding to the photovoltaic string PV1 to turn off, while the multi-pole interlocking switches 20 corresponding to the remaining photovoltaic strings that have not experienced a fault operate normally, continuously supplying the generated electricity to the power conversion unit 10, thereby allowing the photovoltaic system 400 to be used continuously.

[0192] In the above embodiment, if a reverse connection fault occurs in the solar power generation system, the multi-pole interlocking switch corresponding to the reverse connection branch circuit is controlled to turn off, while the remaining multi-pole interlocking switches continue to operate. This allows some of the solar power strings to continuously supply the generated electricity to the power conversion unit, thereby enabling the solar power generation system to be used continuously.

[0193] In some embodiments, the control unit further controls all of the multiple multi-pole interlocking switches 20 to turn off if the fault type of the photovoltaic system is a short-circuit fault. In other words, since it is difficult to identify the photovoltaic string where the short-circuit fault occurred, the safety of the photovoltaic system 400 can be improved by controlling all of the multiple multi-pole interlocking switches 20 to turn off when a short-circuit fault occurs.

[0194] In some embodiments, the power conversion unit 10 includes at least one of a DC / DC converter and a DC / AC converter. For example, the power conversion unit 10 may include a DC / DC converter, a DC / AC converter, or both a DC / DC converter and a DC / AC converter.

[0195] In some embodiments, referring to Figure 16, when the power conversion unit 10 includes a DC / DC converter 12 and a DC / AC converter 11, the positive input terminal of the DC / DC converter 12 functions as the positive input terminal of the power conversion unit 10, the negative input terminal of the DC / DC converter 12 functions as the negative input terminal of the power conversion unit 10, and the output terminal of the DC / DC converter 12 is connected to the input terminal of the DC / AC converter 11.

[0196] Furthermore, referring to Figure 16, if there are multiple multi-pole interlocking switches 20, there are multiple DC / DC converters 12, the input terminals of each DC / DC converter 12 are connected to the corresponding multi-pole interlocking switches 20, and the output terminals of the multiple DC / DC converters 12 are each connected in parallel to the input terminals of the DC / AC converter 11.

[0197] For illustrative purposes, Figure 17 provides two types of DC / DC converters, and Figure 18 provides three types of DC / AC converters; this is for illustrative purposes only and does not limit the scope of this disclosure.

[0198] According to the photovoltaic power generation system of the embodiment of this disclosure, if a failure occurs in the photovoltaic power generation system based on the above-mentioned fault protection device, the switching element in the power conversion unit can be controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate from the fault. After the multi-pole interlocking switch is turned off, the safety of the photovoltaic power generation strings can be improved by ensuring that up to three of the N photovoltaic power generation strings are connected in parallel. If there are multiple multi-pole interlocking switches, the photovoltaic power generation system can be used in some situations by controlling them to turn off some or all of the multi-pole interlocking switches based on the type of failure.

[0199] In some embodiments, further fault protection methods are provided. The fault protection method may include the step of controlling a switching element in a power conversion unit to short-circuit the positive and negative input terminals of the power conversion unit and turn off a multi-pole interlocking switch in the event of a fault in the photovoltaic system, so that up to three of the N photovoltaic strings are connected in parallel.

[0200] In some embodiments, the multi-pole interlocking switch is controlled to turn off after the positive and negative input terminals of the power conversion unit are short-circuited. By short-circuiting the positive and negative input terminals of the power conversion unit in this way, the current flowing through the multi-pole interlocking switch is reduced, improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can shut off and isolate in the event of a fault more safely and reliably.

[0201] In some embodiments, after the positive and negative input terminals of the power conversion unit are short-circuited, the method further includes the step of obtaining at least one of the current values ​​of the branch circuits in which each photovoltaic string is located, the current values ​​of the branch circuits in which each pole switch is located, and the current value of the DC bus, and if it is determined that the current generated by the photovoltaic system is less than a first predetermined value based on at least one of the current values ​​of the branch circuits in which each photovoltaic string is located, the current values ​​of the branch circuits in which each pole switch is located, and the DC bus, the method further includes the step of controlling the multi-pole interlocking switch to turn off. In this way, after the positive and negative input terminals of the power conversion unit are short-circuited, if it is determined that the current flowing through the multi-pole interlocking switch is small, i.e., if the current flowing through the multi-pole interlocking switch is small, the method can control the multi-pole interlocking switch to turn off, thereby further improving safety when the multi-pole interlocking switch is turned off.

[0202] In some embodiments, after the positive and negative input terminals of the power conversion unit are short-circuited, the method further includes the step of acquiring the illuminance and controlling the multi-pole interlocking switch to turn off if the illuminance is less than a predetermined intensity value. When the illuminance is low, the generated current of the corresponding photovoltaic power generation system is low, and after the positive and negative input terminals of the power conversion unit are short-circuited, the current flowing through the multi-pole interlocking switch is small, which can further improve safety when the multi-pole interlocking switch is turned off.

[0203] In some embodiments, the fault protection method further includes the steps of detecting at least one of the parameter values ​​of the branch circuit in which each photovoltaic string is located, the parameter values ​​of the branch circuit in which each pole switch is located, and the parameter values ​​of the DC bus, and detecting that a fault has occurred in the photovoltaic system based on at least one of the parameter values ​​of the branch circuit in which each photovoltaic string is located, the parameter values ​​of the branch circuit in which each pole switch is located, and the parameter values ​​of the DC bus. In this way, by detecting one or more of the parameter values ​​of the branch circuit in which the photovoltaic string is located, the parameter values ​​of the branch circuit in which the pole switch is located, and the parameter values ​​of the DC bus, it is possible to easily and accurately detect whether a fault has occurred in the photovoltaic system.

[0204] In some embodiments, the parameter values ​​of the branch circuit where each solar power generation string is located include first current information, and the parameter values ​​of the branch circuit where each pole switch is located include second current information. Based on the first current information, if it is determined that the current direction of the branch circuit where the solar power generation string is located is opposite to the set direction, a fault is detected in the solar power generation system. Alternatively, if it is determined that the current direction of the branch circuit where the pole switch is located is opposite to the set direction based on the second current information, a fault is detected in the solar power generation system. Alternatively, if it is determined that the current direction of the branch circuit where the solar power generation string is located is opposite to the set direction based on the first current information, and the current direction of the branch circuit where the pole switch corresponding to the solar power generation string is located is opposite to the set direction based on the second current information, a fault is detected in the solar power generation system. In this way, it is possible to easily and accurately detect whether a fault has occurred in the solar power generation system based on the detected current direction.

[0205] In some embodiments, the parameter values ​​of the branch circuit where each solar power generation string is located include first current information, and the parameter values ​​of the branch circuit where each pole switch is located include second current information. If, based on the first current information, it is determined that the absolute current value of the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, a fault is detected in the solar power generation system. Alternatively, if, based on the second current information, it is determined that the absolute current value of the branch circuit where the pole switch is located is greater than a second predetermined current threshold, a fault is detected in the solar power generation system. In this way, a fault is detected in the solar power generation system if, based on the first current information, it is determined that the absolute current value of the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, and based on the second current information, it is determined that the absolute current value of the branch circuit where the pole switch corresponding to the solar power generation string is located is greater than a second predetermined current threshold. In this way, it is possible to easily and accurately detect whether a fault has occurred in the solar power generation system based on the magnitude of the detected current.

[0206] In some embodiments, the parameter values ​​of the branch circuit where each photovoltaic string is located include first current information, and the parameter values ​​of the DC bus include the voltage value of the DC bus. Based on the first current information, if it is determined that the absolute value of the current in the branch circuit where the photovoltaic string is located is greater than a first predetermined current threshold and the voltage of the DC bus is less than a first predetermined voltage threshold, a fault in the photovoltaic system is detected. In this way, it is possible to easily and accurately detect whether a fault has occurred in the photovoltaic system based on the detected magnitudes of the current and voltage.

[0207] In some embodiments, the parameter values ​​of the branch circuits where each pole switch is located include second current information, and the parameter values ​​of the DC bus include the voltage value of the DC bus. Based on the second current information, if it is determined that the absolute value of the current in the branch circuit where the pole switch is located is greater than a second predetermined current threshold and the voltage of the DC bus is less than a first predetermined voltage threshold, a fault is detected in the solar power generation system. In this way, it is possible to easily and accurately detect whether a fault has occurred in the solar power generation system based on the detected magnitude of the current and voltage.

[0208] In some embodiments, the parameter value of the DC bus includes the voltage value of the DC bus, and if the DC bus voltage is lower than a first predetermined voltage threshold, a fault is detected in the photovoltaic power generation system. In this way, it is possible to easily and accurately detect whether a fault has occurred in the photovoltaic power generation system based on the magnitude of the detected voltage.

[0209] In some embodiments, the parameter values ​​of the branch circuits where each solar power generation string is located include first current information, the parameter values ​​of the branch circuits where each pole switch is located include second current information, and the parameter values ​​of the DC bus include DC bus current information. Based on the first current information, the absolute current value of the branch circuit where any one solar power generation string is located is determined, and based on the DC bus current information, the absolute current value of the DC bus is determined. If the absolute current value of the branch circuit where any one solar power generation string is located is greater than the absolute current value of the DC bus, a fault is detected in the solar power generation system. Alternatively, based on the second current information, the absolute current value of the branch circuit where any one pole switch is located is determined, and based on the DC bus current information, the DC bus The absolute value of the current is determined, and if the absolute value of the current in the branch circuit where any one of the pole switches is located is greater than the absolute value of the DC bus current, a fault is detected in the solar power generation system. Alternatively, the absolute value of the current in the branch circuit where any one of the solar power strings is located is determined based on the first current information, the absolute value of the DC bus current is determined based on the DC bus current information, and the absolute value of the current in the branch circuit where any one of the pole switches is located is determined based on the second current information. If the absolute value of the current in the branch circuit where any one of the solar power strings is located is greater than the absolute value of the DC bus current, AND the absolute value of the current in the branch circuit where any one of the pole switches is located is greater than the absolute value of the DC bus current, a fault is detected in the solar power generation system. In this way, it is possible to easily and accurately detect whether a fault has occurred in the solar power generation system based on the magnitude of the detected current.

[0210] For further details regarding fault protection methods, please refer to the above explanation concerning fault protection devices; a detailed explanation will be omitted here.

[0211] According to the fault protection method for a photovoltaic power generation system of the embodiment of the present disclosure, when a fault occurs in the photovoltaic power generation system, the switching element in the power conversion unit is controlled to short-circuit the positive and negative input terminals of the power conversion unit, thereby reducing the current flowing through the multi-pole interlocking switch and improving safety when the multi-pole interlocking switch is turned off. As a result, the multi-pole interlocking switch can more safely and reliably shut off and isolate against faults, and after the multi-pole interlocking switch is turned off, the safety of the photovoltaic power generation strings can be improved by ensuring that up to three of the N photovoltaic power generation strings are connected in parallel.

[0212] Furthermore, the logic and / or steps shown in the flowchart or otherwise described herein are, for example, an ordered list of executable instructions capable of realizing a logical function, and are specifically implemented on any computer-readable medium so that an instruction execution system, device or apparatus (e.g., a computer system, a system including a processor, or other system that reads instructions from an instruction execution system, device or apparatus and executes them) can use, or so that such instruction execution systems, devices or apparatus can be used in combination. For the purposes of this specification, “computer-readable medium” may be an instruction execution system, device or apparatus, or any device used in combination with such instruction execution systems, devices or apparatus, by containing, storing, communicating, propagating, or transmitting a program. More specific examples (but not exhaustive) of computer-readable mediums include electrical connections with one or more wires (electronic devices), portable computer disk cartridges (magnetic devices), random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber devices, and compact disk read-only memory (CDROM). Furthermore, the computer-readable medium may also be paper or other suitable medium on which the program is printed, for example, to obtain the program in electronic form after optically scanning the paper or other medium, then editing, analyzing, or processing it in any other suitable way as needed, and storing it in computer memory.

[0213] It should be understood that each part of this disclosure may be implemented in hardware, software, firmware, or a combination thereof. In the embodiments described above, several steps or methods may be implemented in software or firmware that is stored in memory and executed by an appropriate instruction execution system. For example, if implemented in hardware, as in other embodiments, it may be implemented in any one or a combination of the following technologies that are common knowledge in the art: namely, discrete logic circuits having logic gate circuits for implementing logic functions for data signals, application-specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), and the like.

[0214] In this specification, reference terms such as “one embodiment,” “several embodiments,” “example,” “specific example,” or “several examples” mean that the specific features, structures, materials, or characteristics described in combination with such embodiment or example are included in at least one embodiment or example of this disclosure. In this specification, the exemplary expressions of the above terms do not necessarily refer to the same embodiment or example. The specific features, structures, materials, or characteristics described are combined in an appropriate manner in any one or more embodiments or examples.

[0215] Furthermore, terms such as “first,” “second,” etc., are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly representing the number of technical features shown. Thus, features designated as “first,” “second,” etc., explicitly or implicitly include at least one such feature. In the description of this disclosure, unless otherwise specified, “multiple” means at least two, for example, two, three, etc.

[0216] In this disclosure, unless otherwise specified, terms such as “attached,” “connected,” “connected,” and “fixed” should be understood in a broad sense, and may include, for example, fixed connections, removable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections with an intermediary; and even internal communication or interaction relationships between two components. Those skilled in the art will understand the specific meaning of these terms in this disclosure depending on the specific circumstances.

[0217] While examples of the present disclosure have been shown and described above, it should be understood that these examples are illustrative and should not be construed as limiting the present disclosure. Those skilled in the art can modify, amend, replace, and transform the above examples within the scope of the present disclosure.

Claims

1. A method for protecting a solar power generation system from failures, The photovoltaic power generation system includes a power conversion unit, a multi-pole interlocking switch, N photovoltaic power generation strings, a positive terminal and a negative terminal for connecting to the N photovoltaic power generation strings, wherein the first end of each pole switch in the multi-pole interlocking switch is connected to the positive terminal or the negative terminal, the second end of each pole switch in the multi-pole interlocking switch is connected to the positive input terminal or the negative input terminal of the power conversion unit, N is an integer of 3 or more, and the fault protection method is A fault protection method comprising the steps of, when a failure occurs in the solar power generation system, controlling a switching element in the power conversion unit to short-circuit the positive input terminal and the negative input terminal of the power conversion unit, and controlling the multi-pole interlocking switch to turn off, so that up to three of the N solar power generation strings are connected in parallel.

2. The fault protection method according to claim 1, wherein the multi-pole interlocking switch is controlled to turn off after the positive input terminal and the negative input terminal of the power conversion unit are short-circuited.

3. After the positive input terminal and the negative input terminal of the power conversion unit are short-circuited, The fault protection method according to claim 2, further comprising the steps of obtaining at least one of the current values ​​of the branch circuits in which each solar power generation string is located, the current values ​​of the branch circuits in which each pole switch is located, and the current value of the DC bus, and controlling the multi-pole interlocking switch to turn off if it is determined that the generated current of the solar power generation system is less than a first predetermined value based on at least one of the current values ​​of the branch circuits in which each solar power generation string is located, the current values ​​of the branch circuits in which each pole switch is located, and the current value of the DC bus.

4. After the positive input terminal and the negative input terminal of the power conversion unit are short-circuited, the method is as follows: The fault protection method according to claim 2, further comprising the step of acquiring illuminance and controlling the multi-pole interlocking switch to turn off when the illuminance is less than a predetermined intensity value.

5. The steps include detecting at least one of the parameter values ​​of the branch circuit in which each solar power generation string is located, the parameter values ​​of the branch circuit in which each pole switch is located, and the parameter values ​​of the DC bus, A step of detecting a fault in the solar power generation system based on at least one of the parameter values ​​of the branch circuit in which each solar power generation string is located, the parameter values ​​of the branch circuit in which each pole switch is located, and the parameter values ​​of the DC bus, The fault protection method according to claim 1, further comprising:

6. The parameter values ​​of the branch circuits where each solar power generation string is located include first current information, and the parameter values ​​of the branch circuits where each pole switch is located include second current information. If, based on the first current information, it is determined that the current direction of the branch circuit in which the solar power generation string is located is opposite to the set direction, a malfunction is detected in the solar power generation system, or If, based on the second current information, it is determined that the current direction of the branch circuit where the pole switch is located is opposite to the set direction, a malfunction is detected in the solar power generation system, or, The fault protection method according to claim 5, wherein, based on the first current information, it is determined that the current direction of the branch circuit in which the solar power generation string is located is opposite to the set direction, and based on the second current information, it is determined that the current direction of the branch circuit in which the pole switch corresponding to the solar power generation string is located is opposite to the set direction, and a fault has occurred in the solar power generation system.

7. The parameter values ​​of the branch circuits where each solar power generation string is located include first current information, and the parameter values ​​of the branch circuits where each pole switch is located include second current information. If, based on the first current information, it is determined that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, then a fault is detected in the solar power generation system, or Based on the second current information, if it is determined that the absolute value of the current in the branch circuit where the pole switch is located is greater than the second predetermined current threshold, a fault is detected in the solar power generation system, or, The fault protection method according to claim 5, wherein, based on the first current information, it is determined that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, and based on the second current information, it is determined that the absolute value of the current in the branch circuit where the pole switch corresponding to the solar power generation string is located is greater than a second predetermined current threshold, and a fault is detected in the solar power generation system.

8. The parameter values ​​of the branch circuit in which each solar power generation string is located include first current information, and the parameter values ​​of the DC bus include the voltage value of the DC bus. The fault protection method according to claim 5, wherein, based on the first current information, it is determined that the absolute value of the current in the branch circuit in which the solar power generation string is located is greater than a first predetermined current threshold, and the voltage of the DC bus is less than a first predetermined voltage threshold, and a fault is detected in the solar power generation system.

9. The parameter values ​​of the branch circuit where each pole switch is located include second current information, and the parameter values ​​of the DC bus include the voltage value of the DC bus. The fault protection method according to claim 5, wherein, based on the second current information, it is determined that the absolute value of the current in the branch circuit where the pole switch is located is greater than a second predetermined current threshold, and the voltage of the DC bus is less than a first predetermined voltage threshold, and a fault is detected in the solar power generation system.

10. The parameter value of the DC bus includes the voltage value of the DC bus. The fault protection method according to claim 5, wherein a fault is detected in the solar power generation system when the voltage of the DC bus is less than a first predetermined voltage threshold.

11. The parameter values ​​of the branch circuits in which each solar power generation string is located include first current information, the parameter values ​​of the branch circuits in which each pole switch is located include second current information, and the parameter values ​​of the DC bus include current information of the DC bus. Based on the first current information, the absolute value of the current in the branch circuit where any one of the solar power generation strings is located is determined, and based on the current information of the DC bus, the absolute value of the current in the DC bus is determined, and if the absolute value of the current in the branch circuit where any one of the solar power generation strings is located is greater than the absolute value of the current in the DC bus, a fault is detected in the solar power generation system, or Based on the second current information, the absolute value of the current in the branch circuit where any one of the pole switches is located is determined, and based on the current information of the DC bus, the absolute value of the current in the DC bus is determined. If the absolute value of the current in the branch circuit where any one of the pole switches is located is greater than the absolute value of the current in the DC bus, a fault is detected in the solar power generation system, or, The fault protection method according to claim 5, wherein the absolute value of the current in a branch circuit where any one of the solar power generation strings is located is determined based on the first current information, the absolute value of the current in the DC bus is determined based on the current information of the DC bus, the absolute value of the current in a branch circuit where any one of the pole switches is located is determined based on the second current information, and if the absolute value of the current in a branch circuit where any one of the solar power generation strings is located is greater than the absolute value of the current in the DC bus, and the absolute value of the current in a branch circuit where any one of the pole switches is located is greater than the absolute value of the current in the DC bus, a fault is detected in the solar power generation system.

12. A fault protection device for a solar power generation system, The photovoltaic power generation system further includes a power conversion unit and N photovoltaic power generation strings, where N is an integer of 3 or more, and the fault protection device is Positive and negative terminals for connecting to the N solar power generation strings, A multi-pole interlocking switch, wherein each pole switch in the multi-pole interlocking switch is a multi-pole interlocking switch whose first end is connected to the positive terminal or the negative terminal and whose second end is connected to the positive input terminal or the negative input terminal of the power conversion unit, A control unit, when a malfunction is detected in the solar power generation system, controls the switching element in the power conversion unit to short-circuit the positive input terminal and the negative input terminal of the power conversion unit, and controls the multi-pole interlocking switch to turn off, so that up to three of the N solar power generation strings are connected in parallel, Fault protection devices including...

13. The fault protection device according to claim 12, wherein the maximum number of photovoltaic strings that can be connected to each positive terminal is three, and / or the maximum number of photovoltaic strings that can be connected to each negative terminal is three.

14. The fault protection device according to claim 13, wherein the negative electrodes of multiple photovoltaic strings that can be connected to the same positive electrode connection terminal are each connected to at least two negative electrode connection terminals.

15. The fault protection device according to claim 12, wherein if there are four or more photovoltaic strings that can be connected to any one positive terminal, the negative terminals of at least two of the four or more photovoltaic strings are connected to two negative terminals, and the maximum number of photovoltaic strings that can be connected to the same negative terminal is three.

16. The fault protection device according to claim 12, wherein if there are four or more photovoltaic strings that can be connected to any one negative terminal, the positive terminals of at least two of the four or more photovoltaic strings are connected to two positive terminals, and the maximum number of photovoltaic strings that can be connected to the same positive terminal is three.

17. The fault protection device according to any one of claims 12 to 16, wherein the control unit further controls the multi-pole interlocking switch to turn off after the positive input terminal and the negative input terminal of the power conversion unit are short-circuited.

18. The fault protection device according to claim 17, further comprising: the control unit, after the positive input terminal and negative input terminal of the power conversion unit are short-circuited, acquires at least one of the current values ​​of the branch circuits in which each photovoltaic string is located, the current values ​​of the branch circuits in which each pole switch is located, and the current value of the DC bus, and if it is determined that the generated current of the photovoltaic system is less than a first predetermined value based on at least one of the current values ​​of the branch circuits in which each photovoltaic string is located, the current values ​​of the branch circuits in which each pole switch is located, and the current value of the DC bus, controls the multi-pole interlocking switch to turn off.

19. The fault protection device according to claim 17, further comprising the control unit, which, after the positive input terminal and the negative input terminal of the power conversion unit are short-circuited, acquires the illuminance and controls the multi-pole interlocking switch to turn off if the illuminance is less than a predetermined intensity value.

20. The fault protection device according to claim 12, further comprising a parameter detection unit, wherein the parameter detection unit detects at least one of the parameter values ​​of the branch circuit in which each solar power generation string is located, the parameter values ​​of the branch circuit in which each pole switch is located, and the parameter values ​​of the DC bus, and the control unit detects a fault in the solar power generation system based on at least one of the parameter values ​​of the branch circuit in which each solar power generation string is located, the parameter values ​​of the branch circuit in which each pole switch is located, and the parameter values ​​of the DC bus.

21. The fault protection device according to claim 20, wherein the parameter value includes one or more of voltage value, current value, temperature value, and power value.

22. The parameter detection unit includes at least one of the first current sensor and the second current sensor. The first current sensor detects the first current information of the branch circuit in which any one of the solar power generation strings is located, and transmits the first current information to the control unit. The fault protection device according to claim 20, wherein the second current sensor detects second current information of a branch circuit where any one of the pole switches is located, and transmits the second current information to the control unit.

23. The control unit further, If, based on the first current information, it is determined that the current direction of the branch circuit in which the solar power generation string is located is opposite to the set direction, a fault is detected in the solar power generation system, or If, based on the second current information, it is determined that the current direction of the branch circuit where the pole switch is located is opposite to the set direction, a malfunction is detected in the solar power generation system, or, The fault protection device according to claim 22, which detects that a fault has occurred in the solar power generation system when it is determined, based on the first current information, that the current direction of the branch circuit in which the solar power generation string is located is opposite to the set direction, and based on the second current information, it is determined that the current direction of the branch circuit in which the pole switch corresponding to the solar power generation string is located is opposite to the set direction.

24. The control unit further, If, based on the first current information, it is determined that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, then a fault is detected in the solar power generation system, or If, based on the second current information, it is determined that the absolute value of the current in the branch circuit where the pole switch is located is greater than the second predetermined current threshold, then a fault is detected in the solar power generation system, or, The fault protection device according to claim 22, which detects that a fault has occurred in the solar power generation system when it is determined, based on the first current information, that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, and based on the second current information, it is determined that the absolute value of the current in the branch circuit where the pole switch corresponding to the solar power generation string is located is greater than a second predetermined current threshold.

25. The fault protection device according to claim 22, further comprising a first voltage sensor that detects the voltage value of the DC bus and transmits the voltage value of the DC bus to the control unit.

26. The fault protection device according to claim 25, wherein the control unit further detects that a fault has occurred in the solar power generation system when the voltage of the DC bus is less than a first predetermined voltage threshold.

27. The control unit further, If, based on the first current information, it is determined that the absolute value of the current in the branch circuit where the solar power generation string is located is greater than a first predetermined current threshold, and the voltage of the DC bus is less than a first predetermined voltage threshold, then a fault is detected in the solar power generation system, or The fault protection device according to claim 25, which detects that a fault has occurred in the solar power generation system when it is determined, based on the second current information, that the absolute value of the current in the branch circuit where the pole switch is located is greater than a second predetermined current threshold and the voltage of the DC bus is less than a first predetermined voltage threshold.

28. The fault protection device according to claim 22, further comprising a third current sensor that detects current information of the DC bus and transmits the current information of the DC bus to the control unit, wherein the parameter detection unit further includes

29. The control unit further, Based on the first current information, the absolute value of the current in the branch circuit where any one of the solar power generation strings is located is determined, and based on the current information of the DC bus, the absolute value of the current in the DC bus is determined, and if the absolute value of the current in the branch circuit where any one of the solar power generation strings is located is greater than the absolute value of the current in the DC bus, a fault is detected in the solar power generation system, or Based on the second current information, the absolute value of the current in the branch circuit where one of the pole switches is located is determined, and based on the current information of the DC bus, the absolute value of the current in the DC bus is determined. When the absolute value of the current in the branch circuit where one of the pole switches is located is greater than the absolute value of the current in the DC bus, a fault is detected in the solar power generation system, or, The fault protection device according to claim 28, which determines the absolute value of the current in a branch circuit where any one of the solar power generation strings is located based on the first current information, determines the absolute value of the current in the DC bus based on the current information of the DC bus, determines the absolute value of the current in a branch circuit where any one of the pole switches is located based on the second current information, and detects that a fault has occurred in the solar power generation system if the absolute value of the current in the branch circuit where any one of the solar power generation strings is located is greater than the absolute value of the current in the DC bus, and the absolute value of the current in the branch circuit where any one of the pole switches is located is greater than the absolute value of the current in the DC bus.

30. It is a combiner box, A fault protection device according to any one of claims 12 to 29, The fault protection device is a combiner box that, in the event of a fault in the photovoltaic power generation system, short-circuits the positive input terminal and the negative input terminal of the power conversion unit, thereby disconnecting the N photovoltaic power generation strings from the power conversion unit, so that up to three of the N photovoltaic power generation strings are connected in parallel.

31. It is an inverter, A fault protection device according to any one of claims 12 to 29, A power conversion unit equipped with a DC / AC converter, Includes, The power conversion unit converts the DC power output from the N solar power generation strings to output AC power via the DC / AC converter, and the fault protection device, in the event of a fault in the solar power generation system, short-circuits the positive input terminal and the negative input terminal of the power conversion unit, thereby disconnecting the N solar power generation strings from the power conversion unit, so that up to three of the N solar power generation strings are connected in parallel, in the inverter.

32. It is a solar power generation system, A photovoltaic power generation system including a fault protection device according to any one of claims 12 to 29.

33. The photovoltaic power generation system according to claim 32, wherein, if there are multiple multi-pole interlocking switches, each of the multiple multi-pole interlocking switches is connected in parallel to the positive input terminal and the negative input terminal of the power conversion unit, and the control unit further determines the type of failure of the photovoltaic power generation system and controls some or all of the multiple multi-pole interlocking switches to turn off based on the type of failure of the photovoltaic power generation system.

34. The solar power generation system according to claim 33, further comprising the control unit which controls the multi-pole interlocking switch corresponding to the reverse connection branch circuit among the plurality of multi-pole interlocking switches to turn off if the failure type of the solar power generation system is a reverse connection failure.

35. The photovoltaic power generation system according to claim 33, further comprising the control unit which controls all of the multiple multi-pole interlocking switches to turn off if the failure type of the photovoltaic power generation system is a short-circuit failure.

36. The photovoltaic power generation system according to claim 32, wherein the power conversion unit includes at least one of a DC / DC converter and a DC / AC converter.

37. The photovoltaic power generation system according to claim 36, wherein the power conversion unit includes a DC / DC converter and a DC / AC converter, the positive input terminal of the DC / DC converter functions as the positive input terminal of the power conversion unit, the negative input terminal of the DC / DC converter functions as the negative input terminal of the power conversion unit, and the output terminal of the DC / DC converter is connected to the input terminal of the DC / AC converter.

38. The photovoltaic power generation system according to claim 37, wherein, if there are multiple multi-pole interlocking switches, there are multiple DC / DC converters, the input terminal of each DC / DC converter is connected to the corresponding multi-pole interlocking switch, and the output terminals of the multiple DC / DC converters are each connected in parallel to the input terminals of the DC / AC converter.

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