Solar power generation system, solar inverter, and DC combiner box

Abstract

The present application discloses a photovoltaic power generation system, a photovoltaic inverter, and a DC combiner box, and relates to the field of photovoltaic power generation technology. The photovoltaic power generation system includes a protection switch and a plurality of DC-DC converters. Each DC-DC converter includes a DC bus, a DC-DC circuit, and at least one input interface. The input interface is configured to be connected to a photovoltaic unit. The photovoltaic unit includes at least one photovoltaic module. The input interface is connected to the DC bus using a protection switch, the DC bus is connected to the input terminal of the DC-DC circuit, and the output terminal of the DC-DC circuit is the output terminal of the DC-DC converter. The protection switch includes a release device and a switching device connected in series. The release device is configured to control the switching device so that the connection is broken when a short-circuit fault occurs on the line where the release device is located. By using the photovoltaic power generation system, the photovoltaic unit and the line can be effectively protected when a short circuit occurs in the photovoltaic unit or the line.

Description

Technology Field

[0001] This application relates to the field of photovoltaic power generation technology, and in particular to photovoltaic power generation systems, photovoltaic inverters, and DC combiner boxes. Background Technology

[0002] Photovoltaic power generation is a technology that converts light energy into electrical energy by utilizing the photovoltaic effect at semiconductor interfaces. A photovoltaic power generation system can generally include photovoltaic units, inverters, and AC power distribution devices. To obtain relatively high output voltage or output current, photovoltaic units are typically configured by connecting multiple photovoltaic modules in specific series and / or parallel connections. To improve the power generation efficiency of the photovoltaic power generation system, photovoltaic units are connected to components with independent Maximum Power Point Tracking (MPPT) capabilities.

[0003] To improve the DC ratio of the current photovoltaic power generation system (the ratio of the power of the photovoltaic unit to the input power of the photovoltaic inverter), each MPPT component is typically connected to at least two photovoltaic units. In the event that a photovoltaic unit or the line on which the photovoltaic unit is located is short-circuited, the short-circuit current is the sum of the output currents of the other connected photovoltaic units. When there is only one connected photovoltaic unit, the photovoltaic unit and the line can tolerate this short-circuit current because the short-circuit current is relatively small. However, when there are two or more other connected photovoltaic units, the short-circuit current is relatively large. To protect the photovoltaic units and the line, a fuse is connected in series to the positive or negative output terminal of the photovoltaic unit, so that the fuse blows and protects the photovoltaic unit and the line.

[0004] However, generally, the fusing current of a fuse is relatively high, while the output current of each solar unit is relatively low. Therefore, it may be difficult for the sum of the short-circuit currents of multiple solar units to reach the fuse's fusing current. As a result, the time it takes for the fuse to blow increases, and the fuse cannot effectively protect the solar units and lines.

[0005] The present application provides a photovoltaic power generation system, a photovoltaic inverter, or a direct current combiner box for effectively protecting a photovoltaic unit and a line when a short circuit occurs in the photovoltaic unit or the line.

[0006] According to a first aspect, the present application provides a photovoltaic power generation system. The photovoltaic power generation system comprises a protection switch and a plurality of direct current (DC)-DC converters. Each DC-DC converter comprises a direct current bus, a DC-DC circuit, and at least one input interface. The input interface is configured to be connected to a photovoltaic unit, and the photovoltaic unit comprises at least one photovoltaic module. The input interface is connected to the DC bus using a protection switch, the DC bus is connected to the input terminal of the DC-DC circuit, and the output terminal of the DC-DC circuit is the output terminal of the DC-DC converter. The protection switch comprises a release device and a switching device connected in series. The release device is configured to control the switching device to be disconnected when a short-circuit fault occurs on the line where the release device is located.

[0007] According to the photovoltaic power generation system, when a short-circuit fault occurs in a photovoltaic unit, the release device controls the switching device to disconnect the connection, thereby disconnecting the interface from the DC bus and the photovoltaic unit connected to the interface from the DC bus. Consequently, photovoltaic units connected to other interfaces do not output current to the line where the photovoltaic unit with the short-circuit fault is located, thus protecting the photovoltaic unit and the line from damage. Based on the protection action triggered by the switching device under the control of the release device, no additional control circuitry is required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as a built-in fuse, can be placed on the photovoltaic unit side instead of under the photovoltaic inverter or DC combiner box of the photovoltaic power generation system, thereby further reducing cable costs.

[0008] In a possible implementation, the release device is an electromagnetic release device. When the reverse current of the line where the release device is located is greater than a first current value, the release device controls the switching device to disconnect. The first current value is related to the electrical parameters of the electromagnetic release device.

[0009] In a possible implementation, the release device is an electromagnetic release device. When an overcurrent occurs in the line where the release device is located, the release device controls the switching device to disconnect the connection.

[0010] In a possible implementation, the release device is a thermal release device. When an overcurrent occurs in the line where the release device is located, the release device controls the switching device to disconnect. For example, in the case of a bimetal sheet thermal release device, when an overcurrent occurs in the line where the release device is located, the bimetal sheet generates heat to drive the switching device to operate.

[0011] In a possible implementation, each input interface is connected to a single solar unit.

[0012] In a possible implementation, up to two photovoltaic units are connected in parallel and then connected to an input interface. In this case, each photovoltaic unit can withstand current input by one or two other photovoltaic units.

[0013] In a possible implementation, up to three photovoltaic units are connected in parallel and then connected to an input interface. In this case, each photovoltaic unit can withstand current input by up to two other photovoltaic units.

[0014] In a possible embodiment, the photovoltaic power generation system further includes an alternating current (AC) circuit, and a DC-AC converter and a plurality of DC-DC converters form an inverter. The positive output ports of the plurality of DC-DC converters are connected in parallel to the positive input ports of the DC-AC converters, the negative output ports of the plurality of DC-DC converters are connected in parallel to the negative input ports of the DC-AC converters, and the output ports of the DC-AC converters are the output ports of the inverter.

[0015] In a possible implementation, a plurality of DC-DC converters form a DC combiner box, the positive output ports of the plurality of DC-DC converters are connected in parallel to form the positive output ports of the DC combiner box, and the negative output ports of the plurality of DC-DC converters are connected in parallel to form the negative output ports of the DC combiner box.

[0016] In a possible implementation, the photovoltaic system further includes a protective device. The protective device is connected to the photovoltaic unit in series or parallel. A release device is additionally configured to prevent the protective device from triggering a protective action when controlling a switching device to disconnect the connection.

[0017] In other words, when reconfiguring a current solar power generation system that uses protection devices, it is easy because there is no need to remove the protection devices.

[0018] In a possible implementation, the protection device includes at least one of a fuse, an optimizer, and a disconnection box.

[0019] According to a second aspect, the present application further provides a solar inverter configured to be connected to a solar unit. The solar unit includes at least one solar module, and the solar inverter includes a protection switch, a DC-AC converter, and a plurality of DC-DC converters. Each DC-DC converter includes a DC bus, a DC-DC circuit, and at least one input interface. The input interface is configured to be connected to the solar unit, and the solar unit includes at least one solar module. The input interface is connected to the DC bus using a protection switch, the DC bus is connected to the input terminal of the DC-DC circuit, and the output terminal of the DC-DC circuit is the output terminal of the DC-DC converter. The positive port of the output terminal of the plurality of DC-DC converters is connected in parallel to the positive input port of the DC-AC converter, and the negative port of the output terminal of the plurality of DC-DC converters is connected in parallel to the negative input port of the DC-AC converter. The protection switch includes a release device and a switching device connected in series. The release device is configured to control the switching device so that the connection is broken when a short-circuit fault occurs on the line where the release device is located.

[0020] According to the solar inverter, when a short-circuit fault occurs in a connected solar unit, the release device controls the switching device to disconnect the connection, thereby disconnecting the interface from the DC bus and the solar unit connected to the interface from the DC bus. Consequently, solar units connected to other interfaces do not output current to the line where the short-circuited solar unit is located, thus protecting the solar unit and the line from damage. Based on the protection action triggered by the switching device under the control of the release device, additional control circuitry is not required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as an integrated fuse, can be placed on the solar unit side instead of under the solar inverter of the solar power system. This further reduces cable costs.

[0021] In a possible implementation regarding the second aspect, the release device is an electromagnetic release device. When the reverse current of the line where the release device is located is greater than the first current value, the release device controls the switching device to disconnect the connection.

[0022] In a possible implementation regarding the second aspect, the release device is an electromagnetic release device. When an overcurrent occurs in the line where the release device is located, the release device controls the switching device to disconnect the connection.

[0023] In a possible implementation regarding the second aspect, the release device is a thermal release device. When an overcurrent occurs in the line where the release device is located, the release device controls the switching device to disconnect the connection.

[0024] According to a third aspect, the present application further provides a DC combiner box configured to be connected to a photovoltaic unit. The photovoltaic unit includes at least one photovoltaic module, and the DC combiner box includes a protection switch and a plurality of DC-DC converters. Each DC-DC converter includes a DC bus, a DC-DC circuit, and at least one input interface. The input interface is configured to be connected to the photovoltaic unit, and the photovoltaic unit includes at least one photovoltaic module. The input interface is connected to the DC bus using a protection switch, the DC bus is connected to the input terminal of the DC-DC circuit, and the output terminal of the DC-DC circuit is the output terminal of the DC-DC converter. The positive port of the output terminal of the plurality of DC-DC converters is connected in parallel to the positive output port of the DC combiner box, and the negative port of the output terminal of the plurality of DC-DC converters is connected in parallel to the negative output port of the DC combiner box. The protection switch includes a release device and a switching device connected in series. The release device is configured to control the switching device so that the connection is broken when a short-circuit fault occurs on the line where the release device is located.

[0025] According to the DC combiner box, when a short circuit occurs in a connected solar unit, the release device controls the switching device to disconnect the connection, thereby disconnecting the interface from the DC bus and the solar unit connected to the interface. Consequently, solar units connected to other interfaces do not output current to the line where the short-circuited solar unit is located, thus protecting the solar unit and the line from damage. Based on the protection action triggered by the switching device under the control of the release device, additional control circuitry is not required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as an integrated fuse, can be placed on the solar unit side instead of under the DC combiner box of the solar power system. This further reduces cable costs.

[0026] In a possible implementation regarding the third aspect, the release device is an electromagnetic release device. When the reverse current of the line where the release device is located is greater than the first current value, the release device controls the switching device to disconnect the connection.

[0027] In a possible implementation regarding the third aspect, the release device is an electromagnetic release device. When an overcurrent occurs in the line where the release device is located, the release device controls the switching device to disconnect the connection.

[0028] In a possible implementation regarding the third aspect, the release device is a thermal release device. When an overcurrent occurs in the line where the release device is located, the release device controls the switching device to disconnect the connection. Brief explanation of the drawing

[0029] Figure 1 is a schematic diagram of a short-circuit protection circuit used in the prior art. Figure 2 is a schematic diagram of a short-circuit protection circuit used in the prior art. Figure 3 is a schematic diagram of a short-circuit protection circuit used in the prior art. FIG. 4 is a schematic diagram of a branch according to an embodiment of the present application. FIG. 5 is a schematic diagram of another branch according to an embodiment of the present application. FIG. 6 is a schematic diagram of a photovoltaic power generation system according to an embodiment of the present application. FIG. 7 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 8 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 9 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 10 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 11 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 12 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 13 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 14 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 15 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 16 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 17 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 18 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 19 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 20 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 21 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application. FIG. 22 is a schematic diagram of a solar inverter according to an embodiment of the present application. FIG. 23 is a schematic diagram of a DC combiner box according to an embodiment of the present application. Specific details for implementing the invention

[0030] To improve the DC ratio of a photovoltaic power generation system, each MPPT component is typically connected to at least two or more photovoltaic units. Additionally, to protect the photovoltaic units and lines in the event of a short circuit, the positive or negative output terminals of the photovoltaic units are connected in series to a fuse (also known as fuse blowing). The following describes an example where each MPPT component is connected to three branches. The principle for connecting each MPPT component to more branches is similar. Further details will not be explained here.

[0031] Refer to FIGS. 1 to 3. FIG. 1 is a schematic diagram in which the positive output terminal and the negative output terminal of a photovoltaic unit are connected in series with a fuse. FIG. 2 is a schematic diagram in which the positive output terminal of a photovoltaic unit is connected in series with a fuse. FIG. 3 is a schematic diagram in which the negative output terminal of a photovoltaic unit is connected in series with a fuse.

[0032] Each branch includes one solar module (101). Three branches are connected in parallel in front of a switch (102) and then connected to an MPPT component (103) using a DC switch (102). Fuses 1 through 6 in FIG. 1, fuses 1 through 3 in FIG. 2, and fuses 1 through 3 in FIG. 3 are fuses that blow when the current in the line becomes excessively large in order to protect the solar module and the line.

[0033] However, because the actual output current of the solar unit is relatively small, the fuse does not blow quickly. A fuse with a rated current of 15A is used as an example. According to the fuse specifications, when the fuse does not blow, the allowable current can reach up to 1.13 × 15 = 16.95A, and the current required for the fuse to blow within one hour is 1.35 × 15 = 20.25A. The short-circuit current is difficult to meet the current required for the fuse to blow quickly. Therefore, the fuse does not blow or requires a relatively long time to blow. As a result, the solar unit and the line cannot be effectively protected. In some embodiments, because cable protection must be considered, a Y-wire harness of the built-in fuse must be additionally placed on the DC-DC converter side, and the solar unit of the DC-DC converter may be connected using a relatively long cable. This further increases cable costs.

[0034] To solve the aforementioned technical problem, the present application provides a photovoltaic power generation system, a photovoltaic inverter, and a DC combiner box for effectively protecting a photovoltaic unit and a line when a short circuit occurs in the photovoltaic unit or line. Further details are described below with reference to the attached drawings.

[0035] The following terms "First," "Second," etc. are for illustrative purposes only and should not be understood as an indication or implication of relative importance, or as an implicit indication of the quantity of the indicated technical features. Accordingly, the features limited by "First," "Second," etc., may explicitly or implicitly include one or more features.

[0036] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present application embodiment is clearly explained below with reference to the accompanying drawings of the present application embodiment.

[0037] In the following embodiments, a single photovoltaic unit may comprise a single photovoltaic module or be formed by connecting multiple photovoltaic modules in series and / or parallel. For example, a photovoltaic string is formed by first connecting multiple photovoltaic modules in series, and then connecting multiple photovoltaic strings in parallel to form a photovoltaic unit. The specific number of photovoltaic modules included in the photovoltaic unit is not particularly limited in this embodiment of the present application and may be determined by a person skilled in the art based on actual requirements. Furthermore, the electrical parameters of a single photovoltaic module are not particularly limited in this embodiment of the present application.

[0038] The output voltages of multiple photovoltaic units connected to the same DC-DC converter may be the same or different. This is not particularly limited to the embodiments of this application.

[0039] The DC-DC converter of the photovoltaic power generation system provided in this embodiment of the present application can be connected to at least two photovoltaic units using an interface. After being connected using the interface, the photovoltaic units can be connected in parallel to a DC bus within the DC-DC converter, so that the output currents of the photovoltaic units are aggregated into the DC bus to form a branch. The following describes the conventional form of the branch in detail first.

[0040] FIG. 4 is a schematic diagram of a branch according to an embodiment of the present application.

[0041] The branch includes a solar power unit (101a1), the positive output terminal of the solar power unit (101a1) is the positive output terminal of the branch, and the negative output terminal of the solar power unit (101a1) is the negative output terminal of the branch. In the following embodiments, a description thereof is omitted.

[0042] FIG. 5 is a schematic diagram of another branch according to an embodiment of the present application.

[0043] The branch may include a plurality of branches as shown in FIG. 4. Thus, for example, at least two solar units are included in the order 101a1, 101a2, …, 101ai.

[0044] In the present embodiment of the application, a branch is a concept in an electric field and can be understood as a line through which branch current flows to be collected into a DC bus. Still using FIG. 5 as an example, the line where the solar unit (101a1) is located can be called a branch, and the line formed by connecting the solar unit (101a1) and the solar unit (101a2) in parallel can also be called a branch. The positive output terminals of all solar units are collected to form the positive output terminal of the branch, and the negative output terminals of all solar units are collected to form the negative output terminal of the branch.

[0045] In the following embodiments, "branch" specifically refers to the general term for all branches shown in FIGS. 4 and FIGS. 5, or in other words, a general term for all branches excluding the trunk (DC bus).

[0046] The following description uses an example in which a photovoltaic power generation system includes a single DC-DC converter. When a photovoltaic power generation system includes multiple DC-DC converters, the principle is similar, so a detailed description is omitted in this application.

[0047] FIG. 6 is a schematic diagram of a photovoltaic power generation system according to an embodiment of the present application.

[0048] The solar power generation system includes a solar unit (101) and a protection switch (S1~S M+N It includes ) and a DC-DC converter (200).

[0049] The DC-DC converter (200) includes an interface, a DC bus, and a DC-DC circuit (201).

[0050] The DC-DC converter (200) can be connected to a photovoltaic unit using an interface. The number of photovoltaic units connected to the same interface is not specifically limited in this application.

[0051] When one interface is connected to multiple solar units, the multiple solar units are connected in parallel to form a branch as shown in Fig. 5, and then connected to the interface.

[0052] Each solar unit includes at least one solar module.

[0053] Each protection switch includes a release device and a switching device connected in series. The release device is configured to control the switching device to disconnect when a short-circuit fault occurs on the line where the release device is located. In other words, in this case, the protection switch is disconnected, and the input interface of the line where the protection switch is located is disconnected from the DC bus, thereby cutting off the line with the short-circuit fault.

[0054] Using Figure 6 as an example, when a short circuit fault occurs in a single solar unit and the faulty solar unit can withstand the output current of one other normal solar unit, the value of i in the figure is 2.

[0055] As another example, when a short circuit occurs in a single solar unit and the faulty solar unit can withstand the output current of two other normal solar units, the value of i in the drawing is 3.

[0056] A specific value of i is determined based on the actual current allowable value of the photovoltaic unit. This is not specifically limited to this embodiment of the application. It should be noted that the example in FIG. 6 is merely for the sake of illustration and explanation. In the drawing, i photovoltaic units may be connected in parallel inside a DC-DC converter (200), or they may be connected in parallel externally first to an interface for DC bus connection.

[0057] When there is no short circuit, the current from all branches is concentrated into the DC bus. Therefore, the absolute value of the current in the DC bus is greater than the absolute value of the current in any branch. The direction of the current is from the positive electrode of the photovoltaic unit to the positive electrode of the DC bus.

[0058] When a short-circuit fault occurs in any branch, the output current of all other normal branches flows into the short-circuited branch, and a reverse current is generated in the short-circuited branch. When the value of M+N is greater than 2, an additional overcurrent is generated in the short-circuited branch.

[0059] The release device is mechanically connected to the switching device and is configured to release the holding mechanism when a protection action is triggered, so that the switching device is automatically disconnected. The principle of the release device is as follows: When a reverse current or overcurrent occurs in the branch where the release device is located, the release device controls the switching device to disconnect in order to protect the solar unit and the line.

[0060] The DC-DC circuit (201) can specifically be a Boost circuit, a Buck circuit, or a Buck-Boost circuit.

[0061] In conclusion, according to the photovoltaic power generation system, when a short-circuit fault occurs in a photovoltaic unit, the release device controls the switching device to disconnect the connection, thereby disconnecting the interface from the DC bus and the photovoltaic unit connected to the interface from the DC bus. Consequently, photovoltaic units connected to other interfaces do not output current to the line where the photovoltaic unit with the short-circuit fault is located, thus protecting the photovoltaic unit and the line from damage. Based on the protection action triggered by the switching device under the control of the release device, no additional control circuitry is required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as an integrated fuse, can be placed on the photovoltaic unit side instead of under the photovoltaic inverter or DC combiner box of the photovoltaic power generation system, thereby further reducing cable costs.

[0062] The release device may be implemented in different ways. For example: In some embodiments, the release device is an electromagnetic release device. When the reverse current of the branch where the release device is located is greater than a first current value, the release device controls the switching device to disconnect. In some other embodiments, the release device is an electromagnetic release device. When an overcurrent occurs in the branch where the release device is located, the release device controls the switching device to disconnect. In yet another embodiment, the release device is a thermal release device. When an overcurrent occurs in the branch where the release device is located, the release device controls the switching device to disconnect.

[0063] The following describes the implementation of the solar power generation system in detail.

[0064] The following explains, first using an example where a DC-DC converter is connected to two solar units.

[0065] FIG. 7 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0066] Each DC-DC converter (200) is connected to two solar units (101a1, 101a2) using an interface.

[0067] Two solar units are connected to the interface of a DC-DC converter (200). After being connected in parallel inside the DC-DC converter (200), the two solar units are connected to a DC-DC circuit (201) using a DC switch (102). The DC switch (102) is configured to protect the circuit. In some embodiments, a direct connection may be performed instead of placing the DC switch (102).

[0068] Each solar power unit is additionally connected in series to a protection switch (S1).

[0069] When there is no short-circuit fault, the currents from the two photovoltaic units are concentrated into a DC bus. The absolute value of the current in the DC bus (the absolute value of the detected current at point A or point B) is greater than the absolute value of the current at any branch (the absolute value of the detected current at point C or point D).

[0070] When a short circuit occurs in one solar unit, the output current from other normal solar units flows to the short-circuited unit. As a result, a reverse current is generated in the branch where the short-circuited solar unit is located.

[0071] In this case, the release device may be an electromagnetic release device. When the reverse current of the branch where the release device is located is greater than the first current value, the release device controls the switching device to disconnect the connection.

[0072] When a short circuit occurs in the branch where the solar unit (101a1) is located, the protection switch (S1) disconnects, thereby protecting the solar unit and the line by disconnecting the branch where the solar unit (101a1) is located. When a short circuit occurs in the branch where the solar unit (101a2) is located, the protection switch (S2) disconnects, thereby protecting the solar unit and the line by disconnecting the branch where the solar unit (101a2) is located.

[0073] In some embodiments, the protection switch may be connected in series to the positive output terminal of the photovoltaic unit or to the negative output terminal of the photovoltaic unit. Alternatively, redundancy control may be implemented by connecting one protection switch in series to each of the positive and negative output terminals of the photovoltaic unit. This is not particularly limited to the embodiments of this application.

[0074] In another embodiment, when a single DC-DC circuit is connected to only two solar units, either of the protection switches (S1, S2) may be canceled. For example, when solar unit (101a1) is short-circuited after S1 is canceled, solar unit (101a2) transmits current to the branch where solar unit (101a1) is located, but the current is within the tolerance range of solar unit (101a1). Thus, solar unit (101a1) is not damaged. When solar unit (101a2) is short-circuited, the protection switch (S2) is disconnected to protect the circuit.

[0075] In conclusion, when the switching device of the photovoltaic power generation system is disconnected, the interface is disconnected from the DC bus, and the photovoltaic unit connected to the interface is also disconnected from the DC bus. Therefore, photovoltaic units connected to other interfaces do not output current to the line where the photovoltaic unit with the short-circuit fault is located, thereby preventing damage to the photovoltaic unit and the line. Based on the protection action triggered by the switching device under the control of the release device, no additional control circuit is required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as an integrated fuse, can be placed on the photovoltaic unit side instead of under the photovoltaic inverter or DC combiner box of the photovoltaic power generation system, thus further reducing cable costs.

[0076] The aforementioned embodiment is described using an example where each DC-DC converter is connected to a photovoltaic unit using two input interfaces. However, to improve the DC ratio of current photovoltaic power generation systems, photovoltaic units are typically connected by placing three, four, or more input interfaces on each DC-DC converter. The following first explains the operating principle when three input interfaces are placed on each DC-DC converter.

[0077] FIG. 8 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0078] Three solar units are each connected to the three input interfaces of the DC-DC converter. Each of the three solar units is connected in series to a single protection switch inside the DC-DC converter, then the three solar units are connected in parallel, and then connected to the DC-DC circuit (201) using a DC switch (102). The DC switch (102) is configured to protect the circuit. In actual applications, a direct connection may be performed instead of placing the DC switch (102).

[0079] The solar power unit (101a1) is connected in series to the protection switch (S1), the solar power unit (101a2) is connected in series to the protection switch (S2), and the solar power unit (101a3) is connected in series to the protection switch (S3).

[0080] When there is no short-circuit fault, the output currents of the three photovoltaic units are concentrated into a DC bus. Therefore, the absolute value of the current on the DC bus (the absolute value of the detected current at point A or point B) is greater than the absolute value of the current at any branch (the absolute value of the detected current at point C, point D, or point E). In this case, the current direction at points C, D, and E can be set to a preset current direction, for example, a positive direction.

[0081] It is assumed that when a short circuit occurs in a single solar unit, the short circuit occurs in the line where the solar unit (101a3) is located, and the single solar unit can withstand reverse current transmitted from only one other branch.

[0082] In this case, the output current of the other two normal solar units flows to the solar unit (101a3) that has a short-circuit fault. As a result, an overcurrent occurs in the branch where the solar unit (101a3) is located, and a reverse current (opposite to the current direction at point E) occurs.

[0083] In a possible implementation, the release device of S3 is an electromagnetic release device. When the reverse current of the branch where the solar unit (101a3) is located is greater than the first current value, the release device controls the switching device to disconnect.

[0084] In another possible implementation, the release device of S2 is an electromagnetic release device. When an overcurrent occurs in the branch where the solar unit (101a3) is located, the release device controls the switching device to disconnect the connection.

[0085] In another possible implementation, the release device is a thermal release device. When an overcurrent occurs in the branch where the solar unit (101a3) is located, the release device controls the switching device to disconnect.

[0086] Alternatively, one input interface may be connected in series to two protection switches and then connected to the DC bus inside the DC-DC converter. In this case, the two protection switches may use different types of release devices.

[0087] After S3 is disconnected, the solar unit (101a1) and the solar unit (101a2) can continue to work normally, thus protecting the solar unit and the line.

[0088] The above-described embodiment was explained using an example where three input interfaces are arranged in each DC-DC converter. The following explains the principle when four input interfaces are correspondingly arranged in each DC-DC converter.

[0089] FIG. 9 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0090] Each of the four solar units is connected to one input port of the DC-DC converter and then connected in series to the protection switch. After that, the four solar units are connected in parallel to the DC-DC circuit (201).

[0091] Specifically, the positive output terminal of the solar unit is connected to the protection switch (S1). The negative output terminal of the solar unit (101a1) is connected to the protection switch (S3). The negative output terminal of the solar unit (101a2) is connected to the protection switch (S2). The negative output terminal of the solar unit (101a3) is connected to the protection switch (S4). The negative output terminal of the solar unit (101a4) is connected to the protection switch (S5).

[0092] In some embodiments, instead of placing the protection switch (S1) in FIG. 9, a direct connection may be performed.

[0093] When there is no short circuit, the currents of the four photovoltaic units are concentrated into a DC bus, so the absolute value of the current in the DC bus (the absolute value of the detected current at detection point A or B) is greater than the absolute value of the current at any branch (the absolute value of the detected current at detection points C, D, E, and F).

[0094] When a short circuit occurs in one solar unit, the output current from other normal solar units flows to the solar unit with the short circuit. As a result, overcurrent and reverse current occur in the faulty branch.

[0095] It is still used as an example where a single solar unit can withstand current flowing from only one other branch. In this case, the release device of the protection switch on the faulty branch controls the corresponding switching device to disconnect the connection, so the faulty branch is disconnected, allowing the remaining solar units to continue operating normally, thereby protecting the solar units and the line.

[0096] FIG. 10 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0097] The difference between the implementation shown in FIG. 10 and the implementation shown in FIG. 9 is as follows: the positive output terminal of the solar unit (101a1) and the positive output terminal of the solar unit (101a2) are connected at a protection switch (S1) and connected to a positive DC bus using the protection switch (S1). The positive output terminal of the solar unit (101a3) and the positive output terminal of the solar unit (101a4) are connected at a protection switch (S6) and connected to a positive DC bus using the protection switch (S6).

[0098] In this case, the principle is similar to that of FIG. 9, and a detailed description is omitted in this embodiment of the application.

[0099] FIG. 11 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0100] The difference between the method illustrated in FIG. 11 and the method in FIG. 9 is as follows: The positive output terminal of each solar unit is connected in series to a single protection switch inside the DC-DC converter and then connected to the positive DC bus. The negative output terminal of each solar unit is connected in series to a single protection switch inside the DC-DC converter and then connected to the negative DC bus. By redundantly placing protection switches, safety is further enhanced, and it is possible to ensure that the branch where the solar unit is located is disconnected. The specific principle is similar to FIG. 9, and a detailed description is omitted in this embodiment of the application.

[0101] In conclusion, when the DC-DC converter of the photovoltaic power generation system is connected to four photovoltaic units via an interface and a short-circuit fault occurs in a branch, the release device controls the switching device to disconnect the connection, thereby disconnecting the interface from the DC bus and the photovoltaic units connected to the interface from the DC bus. Consequently, photovoltaic units connected to other interfaces do not output current to the line where the short-circuited photovoltaic unit is located, thus protecting the photovoltaic units and lines from damage. Based on the protection action triggered by the switching device under the control of the release device, no additional control circuitry is required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as an integrated fuse, can be placed on the photovoltaic unit side instead of under the photovoltaic inverter or DC combiner box of the photovoltaic power generation system, thereby further reducing cable costs.

[0102] FIG. 12 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0103] The solar power units (101a1, 101a2) are connected in parallel inside the DC-DC converter and then connected to the DC bus of the DC-DC converter using a protection switch. The branches where the solar power units (101a3, 101a4) are located are each connected in series to a single protection switch and then connected to the DC bus of the DC-DC converter.

[0104] Specifically, the positive output terminal of the solar power unit (101a1, 101a2) is connected to the positive DC bus using a protection switch (S1), and the negative output terminal of the solar power unit (101a1, 101a2) is connected to the negative DC bus using a protection switch (S2).

[0105] In some embodiments, instead of placing a protection switch (S2), a direct connection may be performed.

[0106] When there is no short-circuit fault, the currents from all branches are concentrated into the DC bus; therefore, the absolute value of the current in the DC bus (the absolute value of the detected current at detection point A or B) is greater than the absolute value of the current in any branch (the absolute value of the detected currents at detection points C, D, E, F, G, and H).

[0107] When a short circuit occurs in a branch, the output current from the normal branch flows into the short-circuited branch. As a result, a reverse current is generated in the short-circuited branch.

[0108] The release device may be an electromagnetic release device. In this case, the release device of the protection switch for the faulty branch controls the corresponding switching device to disconnect the connection, thereby disconnecting the branch where the short-circuit fault occurred and allowing other solar units to continue operating normally, thus protecting the solar units and the line.

[0109] A detailed description is as follows with reference to Fig. 12:

[0110] When a short circuit occurs in the branch where the solar unit (101a3) is located, S3 is disconnected. In this case, the solar unit (101a3) is disconnected, and the solar units (101a1, 101a2, 101a4) can operate normally.

[0111] When a short circuit occurs in the branch where the solar unit (101a4) is located, S4 is disconnected. In this case, the solar unit (101a4) is disconnected, and the solar units (101a1, 101a2, 101a3) can operate normally.

[0112] When a short circuit occurs in the branch where the solar unit (101a1) is located, S1 and S2 are disconnected. In this case, the current input by the solar unit (101a2) is within the allowable tolerance range of the solar unit (101a1), and the solar units (101a3, 101a4) can operate normally.

[0113] When a short circuit occurs in the branch where the solar unit (101a2) is located, S1 and S2 are disconnected. In this case, the current input by the solar unit (101a1) is within the allowable tolerance range of the solar unit (101a2), and the solar units (101a3, 101a4) can operate normally.

[0114] FIG. 13 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0115] The difference between the implementation shown in FIG. 13 and the implementation shown in FIG. 12 is as follows: the positive output terminal of the solar power unit (101a3, 101a4) is connected to the positive DC bus using a protection switch (S3), the negative output terminal of the solar power unit (101a3) is connected to the negative DC bus using a protection switch (S4), and the negative output terminal of the solar power unit (101a4) is connected to the negative DC bus using a protection switch (S5).

[0116] The operating principle is similar to the description corresponding to FIG. 12, and a detailed description is omitted in this embodiment of the application.

[0117] FIG. 14 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0118] The difference between the implementation shown in FIG. 14 and the implementation shown in FIG. 13 is as follows: solar units (101a1, 101a2) are connected in parallel, and the positive output terminals of solar units (101a1, 101a2) are connected to a positive DC bus using a protection switch (S1), and the negative output terminals are connected to a negative DC bus using a protection switch (S4). The positive output terminal of solar unit (101a3) is connected to a positive DC bus using a protection switch (S1), and the negative output terminal is connected to a negative DC bus using a protection switch (S2). The positive output terminal of solar unit (101a4) is connected to a positive DC bus using a protection switch (S3), and the negative output terminal is connected to a negative DC bus using a protection switch (S4).

[0119] The operating principle is similar to the description corresponding to FIG. 12, and a detailed description is omitted in this embodiment of the application.

[0120] FIG. 15 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0121] The photovoltaic units (101a1, 101a2) are directly connected in parallel inside the DC-DC converter. The positive output terminal of the photovoltaic units (101a1, 101a2) is connected to the positive DC bus using a protection switch (S1), and the negative output terminal is connected to the negative DC bus using a protection switch (S2).

[0122] The solar power units (101a3, 101a4) are directly connected in parallel inside the DC-DC converter. The positive output terminal of the solar power units (101a3, 101a4) is connected to the positive DC bus using a protection switch (S3), and the negative output terminal is connected to the negative DC bus using a protection switch (S4).

[0123] When there is no short-circuit fault, the currents from all branches are concentrated into the DC bus; therefore, the absolute value of the current in the DC bus (the absolute value of the detected current at detection point A or B) is greater than the absolute value of the current in any branch (the absolute value of the detected currents at detection points C, D, E, F, G, and H).

[0124] When a short circuit occurs in a branch, the output current from the normal branch flows into the short-circuited branch. As a result, a reverse current is generated in the short-circuited branch.

[0125] The release device may be an electromagnetic release device. In this case, the release device of the protection switch for the faulty branch controls the corresponding switching device to disconnect the connection, thereby disconnecting the branch where the short-circuit fault occurred and allowing another solar unit to continue operating normally, thus protecting the solar unit and the line.

[0126] Referring to Fig. 15, a detailed description is as follows:

[0127] When a short circuit occurs in the branch where the solar unit (101a1) is located, S1 and S2 are disconnected. In this case, the current input by the solar unit (101a2) is within the allowable tolerance range of the solar unit (101a1), and the solar units (101a3, 101a4) can operate normally.

[0128] When a short circuit occurs in the branch where the solar unit (101a2) is located, S1 and S2 are disconnected. In this case, the current input by the solar unit (101a1) is within the allowable tolerance range of the solar unit (101a2), and the solar units (101a3, 101a4) can operate normally.

[0129] When a short circuit occurs in the branch where the solar unit (101a3) is located, S3 and S4 are disconnected. In this case, the current input by the solar unit (101a4) is within the allowable tolerance range of the solar unit (101a3), and the solar units (101a1, 101a2) can operate normally.

[0130] When a short circuit occurs in the branch where the solar unit (101a4) is located, S3 and S4 are disconnected. In this case, the current input by the solar unit (101a3) is within the allowable tolerance range of the solar unit (101a4), and the solar units (101a1, 101a2) can operate normally.

[0131] In some embodiments, to reduce costs by reducing the number of protection switches connected in series, a direct connection may be performed instead of placing at least one of the protection switches (S1, S2), a direct connection may be performed instead of placing at least one of the protection switches (S3, S4), or a direct connection may be performed instead of placing one of the protection switches (S1, S2) and one of the protection switches (S3, S4).

[0132] The aforementioned embodiments describe the operating principles for cases where each DC-DC converter includes three input interfaces and cases where each DC-DC converter includes four input interfaces. In some embodiments, each DC-DC converter may be additionally connected to correspond to more photovoltaic units. The following specifically describes the operating principles for cases where the number of photovoltaic units connected to each DC-DC converter is greater than four.

[0133] FIG. 16 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0134] The DC-DC converter has M input interfaces for connecting to photovoltaic units, and each interface is connected to one photovoltaic unit to form M first-type photovoltaic unit branches. M is an integer greater than or equal to 3.

[0135] When a solar unit is connected in series to a single protection switch, the protection switch is connected in series to the positive output terminal or the negative output terminal of the solar unit. When a solar unit is connected in series to two protection switches, the protection switches are connected in series to the positive output terminal and the negative output terminal of the solar unit to provide redundant protection.

[0136] M solar units are each connected in series to a single protection switch and then connected in parallel to the DC bus of a DC-DC converter.

[0137] When there is no short-circuit fault, the current from all photovoltaic units is concentrated into a DC bus, and the absolute value of the current in the DC bus (the absolute value of the detected current at detection point A or detection point B) is greater than the absolute value of the current in any branch.

[0138] When a short circuit occurs in one solar unit, the output current from other normal solar units flows to the branch where the short-circuited solar unit is located. As a result, overcurrent and reverse current occur in the faulty branch.

[0139] In this case, the release device of the faulty branch controls the corresponding switching device to disconnect the connection, so that the faulty branch is disconnected and other solar units can continue to operate normally.

[0140] FIG. 17 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0141] All i photovoltaic units are directly connected in parallel inside the DC-DC converter. Then, the i photovoltaic units are connected in series to at least one protection switch and then connected to the DC bus of the DC-DC converter. N is an integer greater than or equal to 2.

[0142] In the event of a short circuit in a single photovoltaic unit, when the faulty photovoltaic unit can withstand the output current of another normal photovoltaic unit, the value of i is 2; or when the faulty photovoltaic unit can withstand the output current of two other normal photovoltaic units, the value of i is 2 or 3.

[0143] FIG. 18 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0144] M solar units are each connected in series to one or more switches inside a DC-DC converter and then connected to a DC bus.

[0145] i solar units are directly connected in parallel inside the DC-DC converter. Then, the i solar units are connected in series to at least one protection switch and then connected to the DC bus of the DC-DC converter. N is an integer greater than or equal to 2.

[0146] In the event of a short circuit failure in a single photovoltaic unit, when the faulty photovoltaic unit can withstand the output current of another normal photovoltaic unit, the value of i is 2; or when the faulty photovoltaic unit can withstand the output current of two other normal photovoltaic units, the value of i is 2 or 3.

[0147] Also, FIG. 19 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0148] Solar units and protection devices can be connected in series or parallel and then connected to a DC-DC converter. The drawing illustrates an example in which i solar units are connected in parallel with a protection device in between. In some embodiments, the protection device may otherwise be connected in series with the solar units.

[0149] The protection device (Q) may be one of a fuse, an optimizer, a single-line box, or a combination thereof, or may be another component capable of protecting the circuit when a short-circuit fault occurs in the circuit. This is not specifically limited to the embodiments of the present application.

[0150] The value of k in the drawings may be determined based on actual cases. This is not particularly limited to the embodiments of the present application.

[0151] In this case, when controlling the switching device to disconnect the connection, a release device is additionally configured to prevent the protection device from triggering a protection action. In other words, when reconfiguring a current photovoltaic power generation system using a protection device, there is no need to remove the protection device, and it can be directly connected to a DC-DC converter.

[0152] It should be noted that when a short circuit fault occurs in a single photovoltaic unit and the faulty photovoltaic unit can withstand the output current of another normal photovoltaic unit, the value of i is 2 to prevent the protective operation of the protective device. When the faulty photovoltaic unit can withstand the output current of two other normal photovoltaic units, the value of i is 2 or 3 to prevent the protective operation of the protective device.

[0153] FIG. 20 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0154] The photovoltaic power generation system illustrated in the drawing includes X DC-DC converters (200) and further includes a DC-AC converter (300). The DC-AC converter is also called an inverter.

[0155] A DC-AC converter and a plurality of DC-DC converters form an inverter (20) which is a string inverter.

[0156] The positive output ports of X DC-DC converters (200) are connected in parallel to the positive input ports of the DC-AC converter (300), and the negative output ports of X DC-DC converters (200) are connected in parallel to the DC-AC converter (300).

[0157] The alternating current output by the inverter (20) flows through an alternating current combiner box or switch box, is collected, then converted by a transformer, and reaches the alternating current power grid.

[0158] FIG. 21 is a schematic diagram of another photovoltaic power generation system according to an embodiment of the present application.

[0159] X DC-DC converters (200) included in the photovoltaic power generation system illustrated in the drawing form a DC combiner box (30). The positive output ports of the X DC-DC converters (200) are connected in parallel to form the positive output ports of the DC combiner box (30). The negative output ports of the X DC-DC converters (200) are connected in parallel to form the negative output ports of the DC combiner box (30).

[0160] In some embodiments, the DC combiner box (30) is an MPPT boost combiner box, and the positive output terminal and the negative output terminal of the DC combiner box (30) are connected to the positive input terminal and the negative input terminal of a centralized inverter, respectively.

[0161] A centralized inverter is configured to convert a single current input from the DC side or multiple DC inputs from the DC side connected in parallel into an AC output. Generally, DC-AC single-stage power conversion is used. The AC output of the centralized inverter flows through a transformer and is then aggregated into the AC power grid.

[0162] Based on the photovoltaic power generation system provided in the above-described embodiment, the embodiment of the present application further provides a photovoltaic inverter, which is described in detail below with reference to the attached drawings.

[0163] FIG. 22 is a schematic diagram of a solar inverter according to an embodiment of the present application.

[0164] The solar inverter (20) illustrated in the drawing includes a protection switch (not shown), a DC-AC converter (300), and a plurality of DC-DC converters (200).

[0165] The input terminal of each DC-DC converter (200) is connected to at least two solar units (101), and each solar unit includes at least one solar module.

[0166] Each DC-DC converter (200) includes a DC bus, a DC-DC circuit, and at least one input interface.

[0167] Each input interface includes a positive input interface and a negative input interface.

[0168] The input interface is configured to be connected to a solar unit. The positive input interface is connected to the positive DC bus inside the solar inverter (20), and the negative input interface is connected to the negative DC bus inside the solar inverter.

[0169] The positive output ports of a plurality of DC-DC converters (200) are connected in parallel to the positive input ports of a DC-AC converter (300), and the negative output ports of a plurality of DC-DC converters (200) are connected in parallel to the negative input ports of a DC-AC converter (300).

[0170] The protection switch includes a release device and a switching device. The release device is configured to control the switching device to disconnect the connection when a short-circuit fault occurs on the line where the release device is located.

[0171] In a possible implementation, the release device is an electromagnetic release device. When the reverse current of the branch where the release device is located is greater than a first current value, the release device controls the switching device to disconnect.

[0172] In another possible implementation, the release device is an electromagnetic release device. When an overcurrent occurs in the branch where the release device is located, the release device controls the switching device to disconnect.

[0173] In another possible implementation, the release device is a thermal release device. When an overcurrent occurs in the branch where the release device is located, the release device controls the switching device to disconnect.

[0174] According to the solar inverter, when a short-circuit fault occurs in a solar unit, the release device controls the switching device to disconnect the connection, thereby disconnecting the interface from the DC bus and the solar unit connected to the interface from the DC bus. Consequently, solar units connected to other interfaces do not output current to the line where the short-circuited solar unit is located, thus protecting the solar unit and the line from damage. Based on the protection action triggered by the switching device under the control of the release device, additional control circuitry is not required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as an integrated fuse, can be placed on the solar unit side instead of under the solar inverter of the solar power system. This further reduces cable costs.

[0175] Based on the photovoltaic power generation system provided in the above-described embodiment, the embodiment of the present application further provides a DC combiner box, which is described in detail below with reference to the attached drawings.

[0176] FIG. 23 is a schematic diagram of a DC combiner box according to an embodiment of the present application.

[0177] The DC combiner box (30) includes a protection switch (not shown) and a plurality of DC-DC converters (200).

[0178] The input terminal of each DC-DC converter is connected to at least two solar units (101), and each solar unit includes at least one solar module.

[0179] Each DC-DC converter includes a DC bus, a DC-DC circuit, and at least one input interface. The input interface includes a positive input interface and a negative input interface. The input interface is configured to be connected to a photovoltaic unit. The positive input interface is connected to a positive DC bus inside a DC combiner box (30), and the negative input interface is connected to a negative DC bus inside a DC combiner box (30).

[0180] The positive output ports of a plurality of DC-DC converters (200) are connected in parallel to form the positive output port of a DC combiner (30), and the negative output ports of a plurality of DC-DC converters (200) are connected in parallel to form the negative output port of a DC combiner box (30).

[0181] The protection switch includes a release device and a switching device. The release device is configured to control the switching device to disconnect the connection when a short-circuit fault occurs on the line where the release device is located.

[0182] In a possible implementation, the release device is an electromagnetic release device. When the reverse current of the branch where the release device is located is greater than a first current value, the release device controls the switching device to disconnect.

[0183] In another possible implementation, the release device is an electromagnetic release device. When an overcurrent occurs in the branch where the release device is located, the release device controls the switching device to disconnect.

[0184] In another possible implementation, the release device is a thermal release device. When an overcurrent occurs in the branch where the release device is located, the release device controls the switching device to disconnect.

[0185] In some embodiments, at least one of the positive input interface or the negative input interface of each input interface is connected in series to a protection switch inside a DC combiner box (30).

[0186] According to the DC combiner box, when a short circuit occurs in a photovoltaic unit, the release device controls the switching device to disconnect the connection, thereby disconnecting the interface from the DC bus and the photovoltaic unit connected to the interface. Consequently, photovoltaic units connected to other interfaces do not output current to the line where the short-circuited unit is located, thus preventing damage to the photovoltaic unit and the line. Based on the protection action triggered by the switching device under the control of the release device, additional control circuitry is not required, and the difficulty of implementing the solution is reduced. Furthermore, since fuses are no longer used, the Y-wire harness, which was originally used as an integrated fuse, can be placed on the photovoltaic unit side instead of under the DC combiner box of the photovoltaic system. This further reduces cable costs.

[0187] In this application, "at least one" should be understood to mean one or more, and "plural" to mean two or more. The term "and / or" is used to describe an association between associated objects and indicates that three relationships may exist. For example, "A and / or B" may indicate the following three cases: where only A exists, where only B exists, or where both A and B exist, wherein A and B may be singular or plural. The character " / " generally indicates an "or" relationship between connected objects. "At least one of the following items (pieces)" or a similar expression indicates any combination of such items, including a single item (piece) or a combination of plural items (pieces). For example, at least one item (piece) of a, b, or c may represent a, b, c, "a and b," "a and c," "b and c," or "a, b, and c," wherein a, b, and c may be singular or plural.

[0188] The foregoing embodiments are merely for illustrating the technical solution of the present application and are not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solution described in the foregoing embodiments may still be modified or some of its technical features replaced with equivalents without departing from the scope of the technical solution of the embodiments of the present application.

Claims

Claim 1 As a photovoltaic power generation system, the photovoltaic power generation system comprises a plurality of protection switches and a plurality of DC-DC converters, each DC-DC converter comprises a DC bus, a DC-DC circuit, and a plurality of input interfaces, wherein the plurality of input interfaces of a first DC-DC converter among the plurality of DC-DC converters are configured to be connected to a plurality of first photovoltaic units among a plurality of photovoltaic units, and each photovoltaic unit comprises at least one photovoltaic module, wherein the plurality of input interfaces of the first DC-DC converter are connected to the DC bus using a plurality of first protection switches among the plurality of protection switches, wherein the positive or negative output terminal of the plurality of first photovoltaic units is connected to a first protection switch among the plurality of first protection switches, and the opposite output terminal of the plurality of first photovoltaic units is connected to at least two first protection switches among the plurality of first protection switches, wherein the DC bus is connected to an input terminal of the DC-DC circuit, and the output terminal of the DC-DC circuit is an output terminal of the first DC-DC converter, and each of the plurality of protection switches comprises a mechanically connected release device and a switching device, wherein the release device is the switching device A photovoltaic power generation system configured to release a holding mechanism when a protection action is triggered so as to be automatically disconnected, wherein the principle of the release device is as follows: when a short-circuit fault occurs in a branch and the reverse current of the normal branch flowing to the branch where the release device is located is greater than a first current value, the release device controls the switching device to disconnect in order to prevent another photovoltaic module from outputting current to the branch where the photovoltaic unit having a reverse current greater than the first current value is located. Claim 2 A photovoltaic power generation system according to claim 1, wherein the release device is an electromagnetic release device, and the short-circuit fault or short-circuit fault occurs including a reverse current on the line where the release device is located being greater than a first current value, and when the reverse current on the line where the release device is located is greater than the first current value or an overcurrent occurs on the line where the release device is located, the release device controls the switching device to disconnect. Claim 3 A photovoltaic power generation system according to claim 1, wherein the release device is an electromagnetic release device, and the release device controls the switching device so that the connection is disconnected when an overcurrent occurs in the line where the release device is located. Claim 4 A photovoltaic power generation system according to claim 1, wherein the release device is a thermal release device, and the release device controls the switching device to disconnect when an overcurrent occurs in the line where the release device is located. Claim 5 A photovoltaic power generation system according to any one of claims 1 to 4, wherein the plurality of first photovoltaic units comprises at least three first photovoltaic units, each first photovoltaic unit comprises at least one photovoltaic string, the positive or negative output terminals of the at least three first photovoltaic units are aggregated and then connected to the one first protection switch, and the opposite output terminals of the at least three photovoltaic units are connected to the at least two first protection switches. Claim 6 A photovoltaic power generation system according to any one of claims 1 to 4, wherein the plurality of first photovoltaic units comprises at least four first photovoltaic units, each first photovoltaic unit comprises at least one photovoltaic string, the positive or negative output terminals of the at least four first photovoltaic units are connected to the one first protection switch after being concentrated, and the opposite output terminals of the at least four photovoltaic units are connected to the at least two first protection switches. Claim 7 A photovoltaic power generation system according to any one of claims 1 to 4, wherein the photovoltaic power generation system further comprises a DC-AC converter, and the DC-AC converter and the plurality of DC-DC converters form an inverter, and the positive output port of the plurality of DC-DC converters is connected in parallel to the positive input port of the DC-AC converter, and the negative output port of the plurality of DC-DC converters is connected in parallel to the negative input port of the DC-AC converter. Claim 8 A photovoltaic power generation system according to any one of claims 1 to 4, wherein the plurality of DC-DC converters form a DC combiner box, the positive output ports of the plurality of DC-DC converters are connected in parallel to form a positive output port of the DC combiner box, and the negative output ports of the plurality of DC-DC converters are connected in parallel to form a negative output port of the DC combiner box. Claim 9 A photovoltaic power generation system according to any one of claims 1 to 4, wherein the photovoltaic power generation system further comprises a protection device, wherein the protection device is connected in series or parallel to the photovoltaic unit, and the release device is further configured to prevent the protection device from triggering a protection operation when the switching device is controlled to disconnect the connection. Claim 10 In claim 9, the protection device comprises: at least one of a fuse, an optimizer, and a single-line box, a photovoltaic power generation system. Claim 11 A solar inverter configured to be connected to a plurality of solar units, wherein each solar unit includes at least one solar module, and the solar inverter includes a plurality of protection switches, a DC-AC converter, and a plurality of DC-DC converters, wherein each DC-DC converter includes a DC bus, a DC-DC circuit, and at least one input interface, wherein the input interface of a first DC-DC converter among the plurality of DC-DC converters is configured to be connected to a plurality of first solar units among the plurality of solar units, and wherein the input interface of the first DC-DC converter is connected to the DC bus using a plurality of first protection switches among the protection switches, wherein a positive or negative output terminal of the plurality of first solar units is connected to one of the first protection switches among the plurality of first protection switches, and an opposite output terminal of the plurality of first solar units is connected to at least two of the first protection switches among the plurality of first protection switches, wherein the DC bus is connected to the input terminal of the DC-DC circuit, and the output terminal of the DC-DC circuit is the output terminal of the first DC-DC converter, and the positive port of the output terminal of the plurality of DC-DC converters is the DC-AC A solar inverter, wherein the positive input port of a converter is connected in parallel, and the negative port of the output terminal of a plurality of DC-DC converters is connected in parallel to the negative input port of a DC-AC converter, and each of the plurality of protection switches includes a release device and a switching device connected in series, and the release device is configured to release a holding mechanism to disconnect the switching device when a short circuit fault occurs in the line where the release device is located, in order to protect the solar unit or the inverter. Claim 12 A solar inverter according to claim 11, wherein the release device is an electromagnetic release device, and the release device controls the switching device to disconnect when the reverse current of the line where the release device is located is greater than a first current value or when an overcurrent occurs in the line where the release device is located. Claim 13 In claim 11, the release device is an electromagnetic release device, and the solar inverter controls the switching device so that the release device disconnects when an overcurrent occurs in the line where the release device is located. Claim 14 In paragraph 13, the release device is a thermal release device, and the solar inverter controls the switching device so that the release device disconnects when an overcurrent occurs in the line where the release device is located. Claim 15 delete Claim 16 delete Claim 17 delete Claim 18 delete Claim 19 delete

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