Photovoltaic system

Abstract

The invention provides a photovoltaic system. The photovoltaic system comprises a plurality of convergence devices and a photovoltaic inverter. The convergence device comprises a plurality of pairs of input terminals, a tripping switch, an output terminal and a controller. The input terminals are used for being connected with a photovoltaic string, the output terminals are connected with a photovoltaic inverter, the tripping switch comprises a plurality of sub-switches which are arranged in a stacked mode, and the plurality of sub-switches are connected between the plurality of pairs of input terminals and output terminals. The photovoltaic inverter comprises a plurality of pairs of direct current input ends and a plurality of DC / DC conversion units, the direct current input ends are used for being connected with output terminals, one end of each DC / DC conversion unit is used for being connected with at least part of sub-switches in one or more convergence devices through the direct current input ends and the output terminals in sequence, and the other ends of the DC / DC conversion units are connected in parallel. And the controller is used for controlling the tripping switch corresponding to the faulted photovoltaic group string to trip and driving the plurality of sub-switches included in the tripping switch to be disconnected when the photovoltaic group string breaks down, so as to disconnect the electrical connection between the faulted photovoltaic group string and the photovoltaic inverter.

Description

Technical Field

[0001] The present application relates to the field of renewable energy power generation, and in particular to a photovoltaic system. Background Art

[0002] With the rapid development of the new energy field, photovoltaic power generation systems have been increasingly used. As the core equipment of the photovoltaic power generation system, the photovoltaic inverter is used to convert the direct current from the photovoltaic module into alternating current and transmit the alternating current to the power grid. At present, the industry includes two mainstream photovoltaic inverters, namely centralized photovoltaic inverters and string photovoltaic inverters. Among them, the centralized photovoltaic inverter has the advantages of high power (above 1WM) and low comprehensive cost, but the maximum power point tracking (MPPT) voltage range of the centralized photovoltaic inverter is narrow, and it cannot monitor the operation of each photovoltaic string. Therefore, each photovoltaic string cannot be operated at the maximum power point, which reduces the power generation. In addition, in order to ensure the safety of the wiring, on the one hand, it is necessary to equip the photovoltaic module and the centralized photovoltaic inverter with a junction box, and on the other hand, it is necessary to equip the junction box and the centralized inverter with distribution devices such as high-current circuit breakers and fuses, which significantly increases the hardware cost and maintenance difficulty of the photovoltaic power generation system. In contrast, string-type PV inverters have a wide MPPT voltage range and flexible configuration, but the number of PV strings that can be connected to string-type PV inverters is limited, making it difficult to increase power. Summary of the invention

[0003] Based on the above technical problems, the present application provides a photovoltaic system, which not only has a larger power level, but also has the advantages of small footprint, convenient installation and transportation, low hardware cost, and high safety performance.

[0004] In a first aspect, the present application provides a photovoltaic system, comprising a plurality of confluence devices and a photovoltaic inverter. The confluence device comprises a plurality of pairs of input terminals, a trip switch, a pair or a plurality of pairs of output terminals and a controller, wherein the input terminal is used to connect the photovoltaic string, the output terminal is connected to the photovoltaic inverter, the trip switch comprises a plurality of sub-switches arranged in a stacked manner, and the plurality of sub-switches are connected between the plurality of pairs of input terminals and the output terminals. The photovoltaic inverter comprises a plurality of pairs of DC input terminals, a plurality of DC / DC conversion units and one or more DC / AC conversion units, wherein the DC input terminal is used to connect the output terminal of the confluence device, one end of the DC / DC conversion unit is used to connect at least part of the sub-switches in one or more confluence devices in turn through the DC input terminal and the output terminal, and the other ends of the plurality of DC / DC conversion units are connected in parallel and used to connect the DC / AC conversion unit. The controller is used to control the trip switch corresponding to the faulty photovoltaic string to trip and drive the multiple sub-switches it includes to disconnect when a reverse connection or short circuit fault occurs in the photovoltaic string, so as to disconnect the electrical connection between the faulty photovoltaic string and the corresponding DC / DC conversion unit, and make the photovoltaic string corresponding to the tripped trip switch have at most three parallel connections.

[0005] The above photovoltaic system connects multiple photovoltaic strings and DC / DC conversion units by arranging a trip switch composed of multiple sub-switches stacked in the confluence device. When one or more photovoltaic strings in the multiple photovoltaic strings fail, the multiple sub-switches can be actively driven to disconnect at the same time, thereby timely cutting off the electrical connection between the multiple photovoltaic strings including the failed photovoltaic string and the corresponding DC / DC conversion unit, effectively cutting off the reverse current or overcurrent path, preventing the reverse connection or short circuit fault from spreading to the DC / DC conversion unit, and improving the safety of the photovoltaic system. The compact arrangement of multiple sub-switches in the trip switch can also save space in the confluence device, thereby greatly reducing the size of the confluence device. The above photovoltaic system arranges multiple DC / DC conversion units in the photovoltaic inverter, each DC / DC conversion unit is used to connect at least one confluence device, so that the DC / DC conversion unit can perform MPPT on the photovoltaic strings connected thereto in a targeted manner, thereby improving the overall power generation of the photovoltaic system.

[0006] In a possible implementation, the photovoltaic inverter further includes a plurality of DC switches, the DC switches are connected between the DC input terminal and the DC / DC conversion unit, one DC switch is connected to a pair of DC input terminals, the DC switch is connected to the DC / DC conversion unit one-to-one, or a plurality of DC switches are connected to one DC / DC conversion unit. By setting up the DC switch, the maintenance of the photovoltaic inverter can be facilitated. For example, when the photovoltaic inverter needs to be repaired due to a fault, the electrical connection between the photovoltaic inverter and the corresponding confluence device can be disconnected by disconnecting the DC switch. In other words, there is no need to unplug the cable between the confluence device and the photovoltaic inverter, thereby avoiding the safety risks caused by misoperation when rewiring after maintenance.

[0007] In a possible implementation, the photovoltaic inverter further includes a control unit, and when a short circuit or overcurrent fault occurs in the photovoltaic inverter, the control unit is used to control the multiple DC switches to disconnect. This arrangement can prevent the internal fault of the photovoltaic inverter from spreading to multiple converging devices, thereby improving the safety of the photovoltaic system.

[0008] In a possible implementation, when the busbar includes a pair of output terminals, all of the plurality of sub-switches are connected to a pair of DC input terminals through the pair of output terminals. This configuration can simplify the wiring inside the busbar, and can also simplify the wiring between the busbar and the photovoltaic inverter, thereby reducing the safety risks caused by wiring errors.

[0009] In a possible implementation, the busbar device further includes a pair of DC busbars and a busbar switch, wherein the DC busbar is connected between a plurality of sub-switches and the output terminal, the pair of DC busbars includes a first busbar and a second busbar, and the busbar switch is connected to at least one of the first busbar and the second busbar. The reliability and maintainability of the busbar device can be further improved by providing a busbar switch. For example, when a photovoltaic string fails, the controller can further disconnect the busbar switch to avoid safety risks caused by insufficient disconnection of the trip switch. Similarly, when the busbar device needs to be maintained and the photovoltaic string is still connected to the busbar device, the maintenance personnel can manually disconnect the trip switch in addition to manually disconnecting the busbar switch to avoid the risk of electric shock.

[0010] In a possible implementation, each pair of input terminals is used to connect a photovoltaic string, and each pair of input terminals includes a first input terminal and a second input terminal, wherein the first input terminal is used to connect to the first pole of the photovoltaic string, and the second input terminal is used to connect to the second pole of the photovoltaic string, the first pole is a positive pole or a negative pole, and the second pole is another pole with a polarity opposite to the first pole. A pair of output terminals includes a first output terminal and a second output terminal. The multiple sub-switches include one or more first sub-switches and multiple second sub-switches, wherein the current carrying capacity of the first sub-switch is greater than the current carrying capacity of the second sub-switch. One or more first sub-switches are used to connect the first input terminal of multiple pairs of input terminals with the first output terminal. Multiple second sub-switches are used to connect the second input terminal of multiple pairs of input terminals with the second output terminal, wherein one second sub-switch is connected to at most three second input terminals. In other words, multiple first input terminals share the same first sub-switch. In this way, the photovoltaic string can be promptly troubleshooted in the event of a reverse connection fault or an overcurrent fault, and the number of switches can be saved, thereby reducing the volume of the converging device and simplifying the wiring between the first input terminal and the first sub-switch.

[0011] In a possible implementation, when the busbar device includes N pairs of output terminals, N is greater than or equal to 2, the plurality of sub-switches are divided into N groups, and each group of sub-switches is connected to a pair of DC input terminals via a pair of output terminals. By grouping the sub-switches, the current value borne by each first sub-switch when the busbar device is operating normally will also decrease, and therefore, the requirements for the selection of the first sub-switch can be reduced.

[0012] In a possible implementation, the busbar device further includes N pairs of DC busbars and busbar switches, wherein each pair of DC busbars is connected between a group of sub-switches and a pair of output terminals, each pair of DC busbars includes a first busbar and a second busbar, and the busbar switch is connected to at least one of the first busbar and the second busbar. As described above, the busbar switch can be provided to further improve the reliability and maintainability of the busbar device.

[0013] In a possible implementation, each pair of input terminals is used to connect a photovoltaic string, and the input terminals include a first input terminal and a second input terminal, wherein the first input terminal is used to connect to the first pole of the photovoltaic string, and the second input terminal is used to connect to the second pole of the photovoltaic string, the first pole is a positive pole or a negative pole, and the second pole is another pole with a polarity opposite to the first pole. The output terminal includes a first output terminal and a second output terminal. Each group of sub-switches includes one or more first sub-switches and M second sub-switches, wherein M is greater than or equal to 2, and the current carrying capacity of the first sub-switch is greater than the current carrying capacity of the second sub-switch. One or more first sub-switches of each group of sub-switches are used to connect the first input terminals of some pairs of input terminals in the multiple pairs of input terminals with a first output terminal. The M second sub-switches of each group of sub-switches are used to connect the second input terminals of some pairs of input terminals in the multiple pairs of input terminals with a second output terminal, wherein one second sub-switch is connected to at most three second input terminals. Since the current carrying capacity of the first sub-switch is greater than the current carrying capacity of the second sub-switch, the number of first sub-switches used can be reduced, thereby reducing the size of the trip switch, which is conducive to the miniaturization of the converging device.

[0014] In a possible implementation, the photovoltaic inverter further includes an AC switch, an AC output terminal, and a control unit, wherein the AC switch is connected between the DC / AC conversion unit and the AC output terminal, and the AC output terminal is used to connect to the power grid. When a power grid fails, the control unit is used to control the AC switch to disconnect. With such an arrangement, when a power grid fails or a fault occurs inside the photovoltaic inverter, the control unit is used to control the AC switch to disconnect, thereby preventing the faulty power grid from affecting the photovoltaic inverter, or preventing the photovoltaic inverter from spreading the fault to the power grid side, thereby improving the safety performance of the photovoltaic system.

[0015] In a possible implementation, the photovoltaic inverter also includes an energy storage input terminal and a bidirectional DC / DC conversion unit, wherein the energy storage input terminal is used to connect the energy storage unit, one end of the bidirectional DC / DC conversion unit is used to connect the energy storage unit through the energy storage input terminal, and the other end of the bidirectional DC / DC conversion unit is used to connect the DC / AC conversion unit. It is worth mentioning that many countries will force photovoltaic systems to be equipped with a certain proportion of energy storage batteries when building photovoltaic power stations, and then actively support the power grid when a power grid failure occurs. Based on this, by setting a bidirectional DC / DC conversion unit in the photovoltaic inverter, it is possible to avoid setting up an additional energy storage converter for the photovoltaic system, simplifying the installation difficulty of the photovoltaic power station and improving the integration of the photovoltaic power station.

[0016] In a possible implementation, the number of first sub-switches among the plurality of sub-switches is less than the number of second sub-switches, and the number of photovoltaic strings connected to the first sub-switches is greater than the number of photovoltaic strings connected to the second sub-switches. In this way, the number of sub-switches in the trip switch can be reduced, thereby reducing the volume of the trip switch and the merging device.

[0017] In a possible implementation, the current carrying capacity of the first sub-switch is greater than the current carrying capacity of the second sub-switch. Similarly, such an arrangement can also reduce the number of sub-switches in the trip switch and reduce the volume of the trip switch and the merging device.

[0018] In a possible implementation, along the stacking direction of the first sub-switch and the second sub-switch, the thickness of the first sub-switch is greater than the thickness of the second sub-switch, and / or the projection area of ​​the first sub-switch is greater than the projection area of ​​the second sub-switch. Similarly, such an arrangement can also reduce the number of sub-switches in the trip switch and reduce the volume of the trip switch and the merging device.

[0019] In a possible implementation, each sub-switch in the multi-sub-switch includes a housing, a moving contact, a first stationary contact, a second stationary contact, and a wiring portion, the moving contact, the first stationary contact, and the second stationary contact are accommodated in the housing, the wiring portion is exposed and fixed to the housing, the first stationary contact and the second stationary contact are opposite and both arranged on the rotation path of the moving contact, the wiring portion is electrically connected to the first stationary contact, and the surface area of ​​the wiring portion corresponding to the first sub-switch is greater than the surface area of ​​the wiring portion corresponding to the second sub-switch. Similarly, such an arrangement can also reduce the number of sub-switches in the trip switch and reduce the volume of the trip switch and the converging device.

[0020] In general, the photovoltaic system provided by the present application greatly simplifies the structure of the merging device and the photovoltaic inverter, which not only facilitates the transportation and installation of the equipment, but also ensures the high safety performance of the photovoltaic system. At the same time, since the merging device is free from the need to set a fuse and the photovoltaic inverter is free from the need to set a fuse, the construction cost and subsequent maintenance difficulty of the photovoltaic power station are significantly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of a centralized photovoltaic power generation system; Figure 2 It is a structural schematic diagram of a combiner box in a centralized photovoltaic power generation system; Figure 3 It is a structural schematic diagram of a centralized inverter in a centralized photovoltaic power generation system; Figure 4 A schematic diagram of a photovoltaic system provided in an embodiment of the present application; Figure 5 Another schematic diagram of the structure of a photovoltaic system provided in an embodiment of the present application; Figure 6 A schematic diagram of a structure of a fusion device in a photovoltaic system provided in an embodiment of the present application; Figure 7 Another structural schematic diagram of a merging device in a photovoltaic system provided in an embodiment of the present application; Figure 8 A schematic diagram of the structure of a photovoltaic inverter in a photovoltaic system provided in an embodiment of the present application; Fig. 9 Another structural schematic diagram of a photovoltaic system provided in an embodiment of the present application; Fig.10 Another structural schematic diagram of a photovoltaic system provided in an embodiment of the present application; Fig.11 Another structural schematic diagram of a photovoltaic system provided in an embodiment of the present application; Fig.12 Another structural schematic diagram of a photovoltaic system provided in an embodiment of the present application; Fig.13 Another structural schematic diagram of a photovoltaic system provided in an embodiment of the present application; Fig.14 One of the structural schematic diagrams of a trip switch in a merging device in a photovoltaic system provided in an embodiment of the present application; Fig.15 The second structural schematic diagram of a trip switch in a merging device in a photovoltaic system provided in an embodiment of the present application; Fig.16 for Fig.14 and Fig.15 An exploded schematic diagram of the trip switch shown; Fig.17 for Figure 14-16 A schematic diagram of the structure of the first sub-switch; Fig.18 for Figure 14-16 Schematic diagram of the structure of the second sub-switch. DETAILED DESCRIPTION

[0022] See also Figure 1 , Figure 1 The figure is a schematic diagram of the structure of a centralized photovoltaic power generation system. Specifically, the centralized photovoltaic power generation system includes photovoltaic modules, a junction box, a centralized inverter, a transformer, and a power grid. The photovoltaic modules are used to convert light energy into direct current and transmit the direct current to the junction box. The junction box is used to ensure the orderly connection and convergence of the photovoltaic modules, and transmit the converged direct current to the centralized inverter. The centralized inverter is used to convert direct current into alternating current and transmit the alternating current to the transformer. The transformer is used to boost the alternating current output by the centralized inverter and transmit the boosted alternating current to the power grid, ultimately achieving AC grid connection.

[0023] Continue to see Figure 2 , Figure 2 for Figure 1 Schematic diagram of the structure of the combiner box. It is worth mentioning that in the centralized photovoltaic power generation system, the combiner box not only has the functions of connection and convergence, but also can cut off the electrical connection between the photovoltaic string and the centralized inverter when the photovoltaic string has a reverse connection or short circuit fault, thereby preventing the fault of the photovoltaic string from spreading to the centralized inverter, and ensuring the power supply safety of the centralized photovoltaic power generation system. Specifically, the combiner box includes a plurality of input terminals 10, a plurality of fuses 11, a molded case circuit breaker 12 and an output terminal 13, wherein the plurality of input terminals 10 are used to connect the photovoltaic strings, and the plurality of input terminals 10 are also used to connect one end of the plurality of fuses 11, and the other ends of the plurality of fuses 11 are connected in parallel to the molded case circuit breaker 12, and the terminal 121 of the molded case circuit breaker 12 is further electrically connected to the output terminal 13, thereby transmitting the converged DC power to the subsequent centralized inverter through the output terminal 13. When a certain photovoltaic module has a reverse connection or short circuit fault, the direct current generated by other photovoltaic strings connected in parallel with the faulty photovoltaic string will be directly injected into the faulty photovoltaic string, causing the fuse 11 connected in series with the faulty photovoltaic module to overheat and burn out, thereby cutting off the overcurrent path. Although such a setting can prevent the photovoltaic string with reverse connection or short circuit fault from burning due to overcurrent, since the fuse 11 is a disposable device, in order to ensure the power generation of the centralized photovoltaic power generation system, maintenance personnel still need to be dispatched to replace the new fuse 11, which increases the difficulty and cost of maintenance. Before replacing the fuse 11, the maintenance personnel need to switch the molded case circuit breaker 12 to the disconnected state, thereby avoiding accidental electric shock during operation and ensuring the personal safety of the maintenance personnel. After replacing the fuse 11, the maintenance personnel need to switch the molded case circuit breaker 12 to the closed state again. Based on this, it can be seen that the existing junction box includes a large number of fuses 11, which increases the difficulty of maintenance and reduces reusability. At the same time, in order to ensure maintenance safety, the junction box needs to be equipped with a molded case circuit breaker 12 with a large current capacity, which increases the volume of the junction box and the hardware cost.

[0024] Continue to see Figure 3 , Figure 3 for Figure 1Schematic diagram of the structure of the centralized inverter. Specifically, the centralized inverter includes a plurality of bus cables 21, a plurality of fuses 22, a distribution switch 23 and a power converter 24. Among them, one end of the bus cable 21 is connected to the bus box, and the other end of the bus cable is connected to the fuse 22 in a one-to-one correspondence. After the plurality of fuses 22 are connected in parallel, they are connected to the distribution switch 23, and the distribution switch 23 is further connected to the power converter 24. When a bus box has a reverse connection or short circuit fault, the direct current transmitted by other bus boxes in parallel with the faulty bus box will be directly poured into the faulty bus box, causing the fuse 22 in series with the faulty bus box to overheat and burn out, thereby cutting off the overcurrent path. Similar to the bus box, by setting the fuse 22, although it can prevent the faulty bus box from burning due to overcurrent, it is still necessary to dispatch maintenance personnel to replace the new fuse 22, which increases the difficulty and cost of maintenance. In addition, the multiple bus cables 21 and the multiple fuses 22 occupy a large amount of space inside the centralized inverter, resulting in the overall volume of the centralized inverter being too large, which is not conducive to its transportation and installation. Similarly, before replacing the fuse 22, the maintenance personnel also need to switch the distribution switch 23 to the disconnected state, and after the replacement is completed, switch the distribution switch 23 to the closed state to restore the normal operation of the centralized inverter. It is worth mentioning that the distribution switch 23 usually has an automatic disconnection function. For example, in the event of a short circuit fault inside the centralized inverter, when the current flowing through the distribution switch 23 exceeds a certain threshold, the distribution switch 23 can be disconnected in time, thereby avoiding the spread of the short circuit fault. Furthermore, the power converter 24 is used for MPPT and is also used to convert direct current into alternating current. Combined with what is mentioned in the background technology, since multiple junction boxes are connected to the power converter 24 through the distribution switch 23, the power converter 24 cannot perform MPPT on each junction box in a targeted manner, that is, it cannot ensure that each junction box operates at the maximum power point, which reduces the power generation of the centralized photovoltaic power generation system. At the same time, the power converter 24 usually performs MPPT and DC to AC conversion at the same time, but in order to give priority to the conversion of DC to AC, the power converter 24 cannot always maintain MPPT, thereby reducing the power generation of the centralized photovoltaic power generation system. In short, the existing centralized inverters are large in size, difficult to transport, complex in operation and maintenance, narrow in MPPT tracking range, high in hardware cost, and cannot adapt to the development trend of extremely simple, safe and efficient operation and maintenance of photovoltaic power stations.

[0025] In view of the above problems existing in the existing centralized photovoltaic power generation system, this application proposes a photovoltaic system, which has a large power level, a small size, a high safety level, and convenient operation and maintenance. Figure 4-Figure 18 The photovoltaic system provided in this application is described.

[0026] See also Figure 4 , Figure 4 A structural schematic diagram of a photovoltaic system provided in an embodiment of the present application. Specifically, the photovoltaic system includes a plurality of confluence devices 3 and a photovoltaic inverter 4. Among them, the confluence device 3 includes a plurality of pairs of input terminals 31, a trip switch 32, a pair of output terminals 33 and a controller 34. Each pair of input terminals 31 is used to connect a photovoltaic string, and each pair of input terminals 31 includes a first input terminal 311 and a second input terminal 312. The first input terminal 311 is used to connect the positive pole of the photovoltaic string, and the second input terminal 312 is used to connect the negative pole of the photovoltaic string. It should be noted that a photovoltaic string is generally composed of a plurality of photovoltaic modules connected in series or in parallel, and the positive pole and negative pole of the photovoltaic string are respectively the positive pole and negative pole exposed to the outside after the positive poles of a plurality of photovoltaic modules are connected in series. The trip switch 32 includes a plurality of sub-switches arranged in a stacked manner, wherein the plurality of sub-switches include a first sub-switch S1 and a plurality of second sub-switches S2, wherein one end of the first sub-switch S1 is used to connect all the first input terminals 311 of the busbar 3, and one end of each second sub-switch S2 is used to connect two second input terminals 312 of the busbar 3. Further, the output terminal 33 is used to connect the photovoltaic inverter 4, and a pair of output terminals 33 includes a first output terminal 331 and a second output terminal 332, wherein the first output terminal 331 is used to connect the other end of the first sub-switch S1 through the first busbar (positive DC busbar BUS+) in a pair of DC buses, and the second output terminal 332 is used to connect the other ends of all the second sub-switches S2 in the busbar 3 through the second busbar (negative DC busbar BUS-) in a pair of DC buses.

[0027] exist Figure 4 In the photovoltaic system, when the connection relationship between the photovoltaic string and the confluence device 3 is normal and the confluence device 3 is working normally, the direct current generated by all photovoltaic strings connected to the confluence device 3 flows out from the positive electrode and flows to the first bus and the first output terminal 331 through the first sub-switch S1. Subsequently, the direct current flows back to the confluence device 3 through the photovoltaic inverter 4 and the second output terminal 332 and the second bus again. Further, the direct current is split and passes through multiple second sub-switches S2, and finally flows back to the negative electrode of each photovoltaic string. At this time, the direction of the current flowing through the first sub-switch S1 and the current flowing through the second sub-switch S2 are positive currents. For the first sub-switch S1, the flow direction of the positive current is from the input terminal 31 to the output terminal 33, and for the second sub-switch S2, the flow direction of the positive current is from the output terminal 33 to the input terminal 31.

[0028] When a reverse connection fault or a short circuit fault occurs in a photovoltaic string connected to a pair of input terminals 31, the direct current generated by the photovoltaic string connected in parallel with the faulty photovoltaic string and sharing the same second sub-switch S2 flows out from the positive pole, and then flows directly to the first input terminal 311 corresponding to the faulty photovoltaic string and flows through the faulty photovoltaic string. Subsequently, the direct current passes through the second input terminal 312 corresponding to the faulty photovoltaic string and finally flows back to the negative pole of the above photovoltaic string. The direct current generated by other photovoltaic strings that do not share the same second sub-switch S2 with the faulty photovoltaic string also flows out from the positive pole and directly flows to the first input terminal 311 corresponding to the faulty photovoltaic string and flows through the faulty photovoltaic string. Subsequently, the direct current passes through the second input terminal 312 corresponding to the faulty photovoltaic string and continues to flow through the second sub-switch S2 corresponding to the faulty photovoltaic string. Finally, the direct current passes through the second sub-switch S2 corresponding to the photovoltaic string and returns to the negative pole of the photovoltaic string. It is worth noting that the direction of the direct current flowing through the second sub-switch S2 corresponding to the faulty photovoltaic string is from the input terminal 31 to the output terminal 33, that is, opposite to the direction of the forward current. At this time, the current is called a reverse current. Based on this, it can be understood that when a reverse connection fault or a short circuit fault occurs in a photovoltaic string connected to a pair of input terminals 31, the direct current generated by other photovoltaic strings will all be poured into the faulty photovoltaic string. At the same time, the second sub-switch S2 corresponding to the faulty photovoltaic string will bear the current from the photovoltaic string that does not share the second sub-switch S2 with the faulty photovoltaic string. At this time, the current borne by the second sub-switch S2 corresponding to the faulty photovoltaic string is a reverse current, and the value of the reverse current will also increase sharply.

[0029] Based on this, in order to avoid failure and burning of the photovoltaic string due to reverse connection or short circuit, the confluence device 3 also includes a controller 34. Figure 4When a photovoltaic string connected to the confluence device 3 has a reverse connection or short circuit fault, the second sub-switch S2 corresponding to the faulty photovoltaic string will have a reverse current or overcurrent. The controller 34 controls the trip switch 32 to trip based on the reverse current or overcurrent signal and drives the multiple sub-switches included in the trip switch 32 to disconnect, thereby disconnecting the electrical connection between the faulty photovoltaic component and the photovoltaic inverter 4 to prevent the fault from spreading to the photovoltaic inverter 4. Further, after the multiple sub-switches included in the trip switch 32 are disconnected, other photovoltaic strings that do not share the same second sub-switch S2 with the faulty photovoltaic string are disconnected from the faulty photovoltaic string, thereby preventing other photovoltaic strings from back-flowing current to the faulty photovoltaic string. It is worth mentioning that in order to detect the occurrence of reverse current or overcurrent in time, the confluence device 3 is also provided with a sensor (not shown). When the sensor detects that the current flowing through a sub-switch is a reverse current, or when the sensor detects that the current flowing through a sub-switch exceeds a set threshold, the sensor is used to send a reverse current or overcurrent signal to the controller 34. It is worth mentioning that although the photovoltaic string sharing the same second sub-switch S2 as the faulty photovoltaic string will still feed current back to the faulty photovoltaic string, the faulty photovoltaic string can withstand the current fed back to it, so there is no danger of burning the photovoltaic string.

[0030] It should be noted that the photovoltaic string can usually withstand the maximum current fed back to it by the other two photovoltaic strings connected in parallel. That is to say, in actual applications, one end of the second sub-switch S2 can be connected to at most three second input terminals 312. Therefore, when a photovoltaic string has a reverse connection or short circuit fault, after the multiple sub-switches included in the trip switch 32 are disconnected, there are at most three photovoltaic strings in parallel. Of course, after the multiple sub-switches included in the trip switch 32 are disconnected, according to the connection relationship between the actual input terminal 31 and the trip switch 32, the maximum three second input terminals 312 connected to one end of the second sub-switch S2 can also be connected to photovoltaic strings that are not in parallel.

[0031] Further, in Figure 4 In the photovoltaic system shown, one end of each second sub-switch S2 is used to connect to the two second input terminals 312 of the busbar device 3. In actual applications, the number of second input terminals 312 of the busbar device 3 that can be connected to one end of each second sub-switch S2 can be different (just ensure that it is less than or equal to 3), or, one end of each second sub-switch S2 is used to connect to the three second input terminals 312 of the busbar device 3, thereby improving the adaptability and flexibility of the busbar device 3.

[0032] It is worth mentioning that in order to save the number of sub-switches and reduce the volume of the trip switch 32, the number of first sub-switches S1 in the trip switch 32 is less than the number of second sub-switches S2. For example, when the first sub-switch S1 and the second sub-switch S2 have the same current carrying capacity and can withstand the sum of five or six photovoltaic string currents at most, one first sub-switch S1 is used to connect five or six first input terminals 311, and one second sub-switch S2 is used to connect at most three second input terminals 312. If the number of input terminals 31 included in the converging device 3 is greater than five pairs or six pairs, the number of first sub-switches S1 needs to be increased.

[0033] In other embodiments of the present invention, in order to further reduce the number of sub-switches, there is a difference in the current carrying capacity of the first sub-switch S1 and the second sub-switch S2, that is, the current carrying capacity of the first sub-switch S1 is greater than the current carrying capacity of the second sub-switch S2. In other words, the number of first sub-switches S1 is much smaller than the number of second sub-switches S2, and the number of first input terminals 311 used to connect to the first sub-switches S1 is much larger than the number of second input terminals 312 used to connect to the second sub-switches S2. When the current carrying capacity of the first sub-switch S1 is large enough, it is feasible to include only one first sub-switch S1 in a trip switch 32. For example, in Figure 4 In the embodiment, all the first input terminals 311 of the current converging device 3 are connected to a first sub-switch S1. It should also be explained that the current carrying capacity of the sub-switch is positively correlated with the value of the maximum current that the sub-switch can withstand. By matching the first sub-switch S1 and the second sub-switch S2 with different current carrying capacities with different numbers of first input terminals 311 and second input terminals 312, the number of sub-switches used can be reduced, and the safety of the trip switch 32 can be ensured.

[0034] Continue to see Figure 4The photovoltaic inverter 4 includes a plurality of pairs of DC input terminals 41, a plurality of DC / DC conversion units 42, a DC / AC conversion unit 43 and an AC output terminal 44. The DC input terminals 41 are used to connect to the output terminals 33 of the converging device 3, and each pair of DC input terminals 41 includes a first DC input terminal 411 and a second DC input terminal 412, wherein the first DC input terminal 411 is used to connect to the first output terminal 331, and the second DC input terminal 412 is used to connect to the second output terminal 332, that is, the DC input terminals 41 are connected to the output terminals 33 in a one-to-one correspondence. One end of the DC / DC conversion unit 42 is connected to the multiple sub-switches included in the trip switch 32 through the DC input terminal 41 and the output terminal 33 in turn. The other ends of the multiple DC / DC conversion units 42 are connected in parallel and used to connect the DC / AC conversion unit 43. The DC / DC conversion unit 42 is used to convert the DC power transmitted by the corresponding converging device 3 into DC power with a suitable voltage. The DC / AC conversion unit 43 is used to convert the DC power converted by the multiple DC / DC conversion units 42 into AC power and transmit the AC power to the power grid through the AC output terminal 44. It can be understood that the photovoltaic inverter 4 is equipped with a DC / DC conversion unit 42 for each converging device 3, so that each converging device 3 can work independently at the maximum power point, thereby increasing the power generation of the photovoltaic system. At the same time, the DC / DC conversion unit 42 undertakes the MPPT function, and the DC / AC conversion unit 43 satisfies the conversion of DC power to AC power. Therefore, the DC / DC conversion unit 42 realizes the MPPT function independently of the DC / AC conversion unit 43, so it can maintain MPPT for a long time, thereby increasing the power generation of the photovoltaic power generation system. Furthermore, by providing a plurality of DC / DC conversion units 42, backflow between a plurality of converging devices 3 connected to the photovoltaic inverter 4 can also be avoided. For example, when a converging device 3 is reversely connected to the photovoltaic inverter 4, that is, the first output terminal 331 of the converging device 3 is connected to the second DC input terminal 412 of the photovoltaic inverter 4 and the second output terminal 332 of the converging device 3 is connected to the first DC input terminal 411 of the photovoltaic inverter 4, the DC / DC conversion unit 42 connected to the reversely connected converging device 3 can block the current backflowed to it by other converging devices 3, thereby improving the safety of the photovoltaic system. When a converging device 3 is short-circuited or a short-circuit occurs in the connection between a converging device 3 and the photovoltaic inverter 4, it is similar to the case where a converging device 3 is reversely connected to the photovoltaic inverter 4, and will not be repeated here.

[0035] Continue to see Figure 4, the photovoltaic inverter 4 also includes a plurality of DC switches S3, each DC switch S3 is connected between a pair of DC input terminals 41 and a DC / DC conversion unit 42. It is worth mentioning that the DC switch S3 also includes two switch units, wherein one switch unit is connected between the first DC input terminal 411 and the DC / DC conversion unit 42, and the other switch unit is connected between the second DC input terminal 412 and the DC / DC conversion unit 42. In practical applications, the DC switch S3 only needs to include at least one switch unit. By setting the DC switch S3, the maintenance of the photovoltaic inverter 4 can be facilitated. For example, when the photovoltaic inverter 4 needs to be repaired due to a fault, the electrical connection between the photovoltaic inverter 4 and the corresponding confluence device 3 can be disconnected by disconnecting the DC switch S3. That is to say, there is no need to unplug the cable between the confluence device 3 and the photovoltaic inverter 4, thereby avoiding the safety risks caused by misoperation when rewiring after maintenance.

[0036] Continue to see Figure 4 , the photovoltaic inverter 4 also includes a control unit 45. Specifically, when a short circuit or overcurrent fault occurs inside the photovoltaic inverter 4, the control unit 45 controls the multiple DC switches S3 to disconnect based on the short circuit or overcurrent signal, thereby disconnecting the electrical connection between the multiple converging devices 3 and the corresponding DC / DC conversion units 42, so as to prevent the internal fault of the photovoltaic inverter 4 from spreading to the multiple converging devices 3.

[0037] Continue to see Figure 4 , the photovoltaic inverter 4 also includes an AC switch S4, which is connected between the DC / AC conversion unit 43 and the AC output terminal 44. It is worth mentioning that when the AC power grid is a three-phase three-wire system, there are three AC switches S4, and the three AC switches S4 are respectively connected to the A-phase, B-phase and C-phase cables. Specifically, when the photovoltaic inverter 4 works normally, the AC switch S4 is closed so that the AC power output by the DC / AC conversion unit 43 is smoothly transmitted to the power grid. When a power grid fault occurs or a fault occurs inside the photovoltaic inverter 4, the control unit 45 is used to control the AC switch S4 to disconnect, thereby preventing the faulty power grid from affecting the photovoltaic inverter 4, or preventing the photovoltaic inverter 4 from spreading the fault to the power grid side, thereby improving the safety performance of the photovoltaic system.

[0038] exist Figure 4In the photovoltaic system shown, in order to further improve the safety performance of the photovoltaic system, the confluence device 3 and the photovoltaic inverter 4 can communicate with each other. Specifically, when the photovoltaic inverter 4 itself fails, or when the photovoltaic inverter 4 needs to be actively shut down due to a grid failure, the photovoltaic inverter 4 is used to send a first fault signal to the confluence device 3, and then the controller 34 in the confluence device 3 is used to control all sub-switches included in the trip switch 32 to disconnect, thereby effectively avoiding the spread and spread of the fault, thereby improving the safety of the photovoltaic system. Similarly, when a photovoltaic string or the confluence device 3 fails, the confluence device 3 is used to send a second fault signal to the photovoltaic inverter 4, and then the control unit 45 in the photovoltaic inverter 4 is used to control all DC switches S3 to disconnect, thereby effectively avoiding the spread and spread of the fault, thereby improving the safety of the photovoltaic system.

[0039] It is understandable that in the photovoltaic system provided in the embodiment of the present application, the concentrator 3 is free from the need to set Figure 2 The multiple fuses 11 and molded case circuit breakers 12 shown in the figure significantly reduce the volume of the confluence device 3, facilitate the transportation of the confluence device 3, simplify the later maintenance of the confluence device 3, and reduce the hardware cost of the confluence device 3. Furthermore, in the photovoltaic system provided in the embodiment of the present application, the photovoltaic inverter 4 is free from the need to set Figure 3 The multiple fuses 22 and distribution switches 23 shown, therefore, significantly reduce the volume of the photovoltaic inverter 4, facilitate the transportation of the photovoltaic inverter 4, ensure that the multiple confluence devices 3 can independently operate at the maximum power point, and improve the overall power generation of the photovoltaic system.

[0040] See also Figure 5 , Figure 5 A schematic diagram of the structure of a photovoltaic system provided in this application. Figure 4 The photovoltaic system shown is different in that Figure 5In the shown busbar device 3, a trip switch 32 includes two first sub-switches S1 and multiple second sub-switches S2, wherein the number of first sub-switches S1 is less than the number of second sub-switches S2. Furthermore, one end of each first sub-switch S1 is respectively used to connect part of the first input terminal 311, the other ends of the two first sub-switches S1 are connected in parallel and connected to the same first output terminal 331, one end of each second sub-switch S2 is respectively used to connect a second input terminal 312, and the other ends of the multiple second sub-switches S2 are connected in parallel and connected to the same second output terminal 332. That is, the two first sub-switches S1 included in the trip switch 32 share the same first output terminal 331, and the multiple second sub-switches S2 share the same second output terminal 332. With such a configuration, the number of output terminals can be reduced, the connection between the busbar device 3 and the photovoltaic inverter 4 can be simplified and the connection cost can be reduced, and the risk caused by incorrect wiring between the busbar device 3 and the photovoltaic inverter 4 can also be reduced. It is worth mentioning that Figure 5 Only two first sub-switches S1 are shown in the figure. In actual application, the number of the first sub-switches S1 can be set as needed.

[0041] See also Figure 6 , Figure 6 This is a schematic diagram of the structure of a confluence device 3 provided in this application. Figure 4 The difference between the shown confluence device 3 is that Figure 6 The shown converging device 3 also includes a bus switch S5. The bus switch S5 includes two small switches, one of which is connected to the first bus, namely BUS+, and the other of which is connected to the second bus, namely BUS-. In practical applications, the bus switch S5 only needs to include at least one small switch. By setting the bus switch S5, the reliability and maintainability of the converging device 3 can be further improved. For example, when a photovoltaic string fails, the controller 34 not only controls the trip switch 32 to disconnect, but also further controls the bus switch S5 to disconnect, thereby avoiding the safety risk caused by insufficient disconnection of the trip switch 32. At the same time, the electrical connection between the photovoltaic inverter 4 and the trip switch 32 is also disconnected, reducing the risk of electric shock. Similarly, when the converging device 3 needs to be maintained and the photovoltaic string is still connected to the converging device 3, the maintenance personnel can not only manually disconnect the trip switch 32, but also manually disconnect the bus switch S5 to avoid the risk of electric shock.

[0042] See also Figure 7 , Figure 7 This is a schematic diagram of the structure of a confluence device 3 provided in this application. Figure 4 The confluence device 3 shown is different in that Figure 7In the shown converging device 3, the first input terminal 311 is used to connect the negative pole of the photovoltaic string, and the second input terminal 312 is used to connect the positive pole of the photovoltaic string. Further, the first output terminal 331 is used to connect the first sub-switch S1 through the second DC bus (negative DC bus BUS-) in a pair of DC buses, and the second output terminal 332 is used to connect all the second sub-switches S2 in the converging device 3 through the first DC bus (positive DC bus BUS+) in a pair of DC buses. By adjusting the connection relationship between the trip switch 32 and the input terminal 31 and the output terminal 33, the converging device 3 can be adapted to photovoltaic strings and photovoltaic inverters 4 with different characteristics.

[0043] See also Figure 8 , Figure 8 A schematic diagram of the structure of a photovoltaic inverter 4 provided in this application. Figure 4 The photovoltaic inverter 4 shown is different in that Figure 8 The photovoltaic inverter 4 shown includes two DC / AC conversion units 43 and six AC switches S4, wherein three AC switches S4 are respectively connected to the A phase, B phase and C phase of one DC / AC conversion unit 43, and the remaining three AC switches S4 are respectively connected to the A phase, B phase and C phase of the remaining other DC / AC conversion unit 43. Specifically, when the power level of the photovoltaic inverter 4 is large, in order to avoid overloading of a single DC / AC conversion unit 43, an additional DC / AC conversion unit 43 can be provided, thereby ensuring the normal operation of the photovoltaic inverter 4.

[0044] See also Fig. 9 , Fig. 9 A schematic diagram of the structure of a photovoltaic system provided in this application. Figure 4 The difference between the shown confluence device 3 is that Fig. 9 The shown busbar device 3 includes two pairs of output terminals 33. Further, Fig. 9 In the shown confluence device 3, the sub-switches included in the trip switch 32 are divided into two groups, namely a first group of sub-switches 321 and a second group of sub-switches 322, and the multiple pairs of input terminals 31 are also divided into two corresponding groups, and each group of sub-switches is connected between a group of input terminals 31 and a pair of output terminals 33. Furthermore, each group of sub-switches includes a first sub-switch S1 and M second sub-switches S2, where M is greater than or equal to 2, wherein the first sub-switch S1 of each group of sub-switches is used to connect all the first input terminals 311 in a group of input terminals 31 corresponding to the group of sub-switches, and each second sub-switch S2 in each group of sub-switches is used to connect two second input terminals 312 in a group of input terminals 31 corresponding to the group of sub-switches. By grouping the sub-switches, the current value that each first sub-switch S1 bears when the confluence device 3 is working normally will also decrease, and therefore, the requirements for the selection of the first sub-switch S1 can be reduced. It is worth mentioning that Fig. 9Each group of sub-switches includes a first sub-switch S1 and M second sub-switches S2, where M is greater than or equal to 2. In actual applications, a group of sub-switches may include multiple first sub-switches S1, that is, the multiple first sub-switches S1 in each group of sub-switches share the same first output terminal 331.

[0045] It is worth mentioning that in practical applications, in order to reduce the number of stacked sub-switches and ensure the stability of sub-switch disconnection, multiple trip switches 32 can be placed in the confluence device 3, and each trip switch 32 is used to connect to one pair or N pairs of output terminals 33, where N is greater than or equal to 2. It is worth mentioning that when the output terminals 33 are N pairs, the number of DC busbars and busbar switches is also N. Further, when a trip switch 32 is used to connect to multiple pairs of output terminals 33, the sub-switches included in the trip switch 32 can also be divided into multiple groups, and each group of sub-switches includes one or more first sub-switches S1.

[0046] See also Fig.10 , Fig.10 A schematic diagram of the structure of a photovoltaic system provided in this application. Fig. 9 The photovoltaic inverter 4 shown is different in that Fig.10 In the photovoltaic inverter 4 shown, each DC / DC conversion unit 42 is connected to two pairs of DC input terminals 41. It is worth mentioning that a DC switch S3 is still provided between each pair of DC input terminals 41 and the DC / DC conversion unit 42. By adjusting the number of DC input terminals 41 connected to each DC / DC conversion unit 42, that is, the number of output terminals 33 connected to each DC / DC conversion unit 42, the power level of each DC / DC conversion unit 42 is adjusted, thereby optimizing the overall performance, cost and volume of the DC / DC conversion unit 42 in the photovoltaic inverter 4.

[0047] See also Fig.11 , Fig.11 A schematic diagram of the structure of a photovoltaic system provided in this application. Fig.10 The photovoltaic system shown is different in that Fig.11In the photovoltaic inverter 4 shown, a DC / DC conversion unit 42 is connected to two confluence devices 3. Specifically, the DC / DC conversion unit 42 is connected to all sub-switches of one of the confluence devices 3 through a pair of DC input terminals 41 and a pair of output terminals 33 in sequence. Further, the DC / DC conversion unit 42 is also connected to part of the sub-switches (a group of sub-switches) of another confluence device 3 through another pair of DC input terminals 41 and another pair of output terminals 33 in sequence. When the photovoltaic strings corresponding to the two confluence devices 3 are close to each other, the maximum power points of the photovoltaic strings corresponding to the two confluence devices 3 are also close to each other. Therefore, the above photovoltaic strings can reuse the same DC / DC conversion unit 42. In this way, the number of DC / DC conversion units 42 can be reduced, and the hardware cost of the DC / DC conversion unit 42 and the volume of the photovoltaic inverter 4 can be reduced.

[0048] See also Fig.12 , Fig.12 A schematic diagram of the structure of a photovoltaic system provided in this application. Fig.11 The photovoltaic system shown is different in that Fig.12 In the photovoltaic inverter 4 shown, a DC / DC conversion unit 42 is connected to part of the sub-switches (a group of sub-switches) of the two converging devices 3 through two pairs of DC input terminals 41 and two pairs of output terminals 33 in sequence. When the photovoltaic strings corresponding to the part of the sub-switches (a group of sub-switches) of the two converging devices 3 are close to each other, the maximum power points of the photovoltaic strings corresponding to the two converging devices 3 are also close to each other, so the above photovoltaic strings can reuse the same DC / DC conversion unit 42. Such a setting can reduce the number of DC / DC conversion units 42, reduce the hardware cost of the DC / DC conversion unit 42 and the volume of the photovoltaic inverter 4.

[0049] See also Fig.13 , Fig.13 A schematic diagram of the structure of a photovoltaic system provided in this application. Figure 4 The photovoltaic inverter 4 shown is different in that Fig.13The photovoltaic inverter 4 shown also includes multiple pairs of energy storage input terminals 46 and a bidirectional DC / DC conversion unit 47. Among them, the bidirectional DC / DC conversion unit 47 is used to connect the energy storage unit 5 through the energy storage input terminal 46. Further, the energy storage input terminal 46 and the bidirectional DC / DC conversion unit 47 are also provided with a DC switch S3. Specifically, when a short circuit or overcurrent fault occurs inside the photovoltaic inverter 4, the control unit 45 can control all DC switches S3 connected to the energy storage unit 5 to disconnect, thereby preventing the fault of the photovoltaic inverter 4 from spreading to the energy storage unit 5. Further, when a fault occurs in the energy storage unit 5, the energy storage unit 5 sends a third fault signal to the control unit 45 of the photovoltaic inverter 4, and the control unit 45 is used to control the DC switch S3 connected to the faulty energy storage unit 5 to disconnect, thereby preventing the fault of the energy storage unit 5 from spreading to the photovoltaic inverter 4. It is worth mentioning that many countries will force the photovoltaic system to be equipped with a certain proportion of energy storage batteries when building photovoltaic power stations, so as to actively support the power grid when a fault occurs in the power grid. Based on this, by setting the bidirectional DC / DC conversion unit 47 in the photovoltaic inverter 4, it is possible to avoid setting up an additional energy storage converter (Power Conversion System, PCS) for the photovoltaic system, simplifying the installation difficulty of the photovoltaic power station and improving the integration of the photovoltaic power station.

[0050] When the current carrying capacity of the first sub-switch S1 and the second sub-switch S2 is different, see Figure 14-18 , Fig.14 This is one of the structural schematic diagrams of the trip switch 32 accommodated in the confluence device 3 in the above embodiment provided by the present application. Fig.15 The second structural schematic diagram of the trip switch 32 accommodated in the confluence device 3 in the above embodiment provided by the present application is as follows: Fig.16 for Fig.14 and Fig.15 The schematic diagram of the partial explosion structure of the trip switch 32 is shown. Fig.17 and Fig.18 The first and second sub-switch S1 and S2 are schematic diagrams of the structure. Fig.14 and Fig.16 The trip switch 32 includes a handle 323, an input shaft 324, a drive mechanism 325, and a plurality of sub-switches stacked along a first direction A. The handle 323 is fixedly connected to the input shaft 324. When the handle 323 is driven to rotate, the input shaft 324 drives the connecting rod or gears in the drive mechanism 325 to rotate, thereby driving at least a portion of the output shaft (not shown) housed in the drive mechanism 325 to rotate. The axis of the output shaft extends along the first direction A.

[0051] Further, see Figure 15-18The first sub-switch S1 and the second sub-switch S2 have similar structures in most aspects, and both include a housing S11, a connection portion S12, a first static contact S13, a moving contact S14, a second static contact S15, a pin portion S16, and an arc extinguishing chamber S17. The first static contact S13, the moving contact S14, the second static contact S15, and the arc extinguishing chamber S17 are all accommodated in the housing S11, the connection portion S12 and the pin portion S16 are exposed and fixed to the housing S11, the connection portion S12 is electrically connected to the first static contact S13, and the pin portion S16 is electrically connected to the second static contact S15. The connection portion S12, the first static contact S13, the moving contact S14, the second static contact S15, and the pin portion S16 are all metal conductors.

[0052] Specifically, the connection portion S12 is one end of the first sub-switch S1 or the second sub-switch S2, which is used to connect the first input terminal 311 and the second input terminal 312 respectively. In practical applications, the connection portion S12 can be integrally formed with the first static contact S13, thereby simplifying the processing. Fig.17 and Fig.18 The wiring portion S12 is a matching structure of screws and nuts. For example, when the wiring portion S12 is used to connect to the first input terminal 311, the wire or conductive copper busbar of the first input terminal 311 is fixed and electrically connected to the wiring portion S12 through the matching of screws and nuts.

[0053] Further, see Fig.15 , the pin portion S16 is a metal flat protrusion, and the pin portion S16 includes a first pin portion S161 and a second pin portion S162. The first pin portion S161 is fixed to the housing S11 of the first sub-switch S1, and the second pin portion S162 is fixed to the housing S11 of the second sub-switch S2. Specifically, the first pin portion S161 is the other end of the first sub-switch S1, which is used to connect the first output terminal 331 of the converging device 3, and the second pin portion S162 is the other end of the second sub-switch S2, which is used to connect the second output terminal 332 of the converging device 3. In actual application, since the pin portion S16 is a flat protrusion structure, the first pin portion S161 and the second pin portion S162 can be directly plugged into the circuit board, and are respectively connected to the first output terminal 331 and the second output terminal 332 through the wiring of the circuit board. In this way, the complicated wiring between the trip switch 32 and the output terminal 33 can be avoided, thereby simplifying the installation steps of the converging device 3.

[0054] Further, the moving contact S14 is connected to the output shaft in a transmission manner and can rotate with the axis of the output shaft as the rotation center, and the first static contact S13 and the second static contact S15 are both arranged on the rotation track of the moving contact S14. The moving contact S14 of the sub-switch closest to the driving mechanism 325 along the first direction A among the multiple sub-switches is fixedly connected to the output shaft, and the moving contacts S14 of the two adjacent sub-switches are sequentially connected in a transmission manner, for example, by snapping. Based on this, when the output shaft rotates, the output shaft can sequentially drive the moving contacts S14 inside the multiple sub-switches to rotate. It can be seen that as the number of sub-switches in the trip switch 32 increases, the driving force received by the moving contact S14 of the sub-switch farthest from the driving mechanism 325 along the first direction A among the multiple sub-switches will also gradually decrease due to sequential transmission, which is likely to cause poor contact between the moving contact S14 and the first static contact S13 and the second static contact S15. Therefore, reducing the number of sub-switches can also improve the reliability of the trip switch 32. When the moving contact S14 contacts the first static contact S13 and the second static contact S15 respectively, the trip switch 32 is closed, and the DC power of the photovoltaic string can be transmitted to the photovoltaic inverter 4 through the trip switch 32 and the output terminal 33 in sequence. When the moving contact S14 is separated from the first static contact S13 and the second static contact S15, the trip switch 32 is opened, and the DC power of the photovoltaic string cannot be transmitted to the photovoltaic inverter 4.

[0055] It should be noted that since the trip switch 32 is connected to multiple photovoltaic strings, the DC current flowing through the trip switch 32 is relatively large. Therefore, when the moving contact S14 is separated from the first static contact S13 and the second static contact S15, an arc usually occurs. In order to extinguish the arc in time and prevent the arc from damaging the trip switch 32, the first sub-switch S1 and the second sub-switch S2 need to be equipped with an arc extinguishing chamber S17.

[0056] Further, continue to combine with see Figure 14-16 , the trip switch 32 also includes a trip device 326. Specifically, when a reverse connection fault or an overcurrent fault occurs in the photovoltaic string, the controller 34 will send a trip signal to the trip device 326, so that the trip device 326 releases the connection with part of the connecting rod in the driving mechanism 325, and then drives the output shaft to rotate, so as to separate the moving contact S14 from the first static contact S13 and the second static contact S15 in the multiple sub-switches. At this time, the controller 34 is housed inside the confluence device 3 as an independent component, and its form is usually a control chip, such as a digital signal processing (DSP) chip. It is worth mentioning that when the controller 34 is in the form of a control chip, it can integrate more protection functions. For example, in Figure 6In the shown confluence device 3, when a photovoltaic string fails, the controller 34 can not only control the trip switch 32 to disconnect, but also further control the bus switch S5 to disconnect. In addition, the controller 34 can also be in the form of a simple mechanical structure or an electromagnetic device. For example, when the controller 34 is in the form of an electromagnetic device, when a reverse connection fault or an overcurrent fault occurs in the photovoltaic string, the controller 34 can directly control the change in magnetic flux based on the change in the current flowing through it, thereby causing the trip device 326 to release the connection with part of the connecting rod in the driving mechanism 325, thereby driving the output shaft to rotate, and realizing the separation of the moving contact S14 from the first static contact S13 and the second static contact S15 in multiple sub-switches. It is worth mentioning that when the controller 34 is in the form of a mechanical structure or an electromagnetic device, it can be integrated inside the trip device 326, thereby improving the integration of the trip switch 32.

[0057] Furthermore, in actual application, in order to reduce the size of the trip switch 32, the number of first input terminals 311 connected to a first sub-switch S1 is much larger than the number of second input terminals 312 connected to a second sub-switch S2. In other words, the number of photovoltaic strings connected to the first sub-switch S1 is much larger than the number of photovoltaic strings connected to the second sub-switch S2. However, it is worth noting that as the number of photovoltaic strings connected to the first sub-switch S1 increases, the current level flowing through the first sub-switch S1 also gradually increases, which puts higher requirements on the current carrying capacity of the first sub-switch S1. In order to avoid the first sub-switch S1 from being damaged due to excessive current flowing through it and to improve the current carrying capacity of the first sub-switch S1, the first sub-switch S1 needs to be specially designed. To this end, the volume of the arc extinguishing chamber S17 in the first sub-switch S1 can be increased.

[0058] Based on this, continue to combine Figure 14-16 , along the first direction A, the thickness A1 of the first sub-switch S1 is greater than the thickness A2 of the second sub-switch S2. In practical applications, the area of ​​the first sub-switch S1 projected along the first direction A can also be increased, that is, the area of ​​the first sub-switch S1 projected along the first direction A is greater than the area of ​​the second sub-switch S2 projected along the first direction A, thereby accommodating a larger arc extinguishing chamber S17.

[0059] Furthermore, in order to ensure a stable connection of the connection portion S12 corresponding to the first sub-switch S1, it is necessary to increase the volume of the connection portion S12. For example, the surface area of ​​the connection portion S12 exposed to the housing S11 of the first sub-switch S1 is greater than the surface area of ​​the connection portion S12 exposed to the housing S11 of the second sub-switch S2.

[0060] In general, the photovoltaic system provided by the present application greatly simplifies the structure of the converging device 3 and the photovoltaic inverter 4, reduces the cost and volume of the converging device 3 and the photovoltaic inverter 4, facilitates the transportation and installation of the equipment, and ensures the high safety performance of the photovoltaic system. At the same time, since the converging device 3 is free from the need to set the fuse 11 and the photovoltaic inverter 4 is free from the need to set the fuse 22, the construction cost and subsequent maintenance difficulty of the photovoltaic power station are significantly reduced.

[0061] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A photovoltaic system, characterized in that: It includes a plurality of converging devices and a photovoltaic inverter; wherein, The merging device comprises a plurality of pairs of input terminals, a trip switch, one or more pairs of output terminals and a controller, wherein the input terminals are used to connect photovoltaic strings, the output terminals are connected to the photovoltaic inverter, the trip switch comprises a plurality of sub-switches arranged in a stacked manner, and the plurality of sub-switches are connected between the plurality of pairs of input terminals and the output terminals; The photovoltaic inverter comprises a plurality of pairs of DC input terminals, a plurality of DC / DC conversion units and one or more DC / AC conversion units, wherein the DC input terminal is used to connect the output terminal of the busbar device, one end of the DC / DC conversion unit is used to connect at least part of the sub-switches in one or more busbar devices through the DC input terminal and the output terminal in sequence, and the other ends of the plurality of DC / DC conversion units are connected in parallel and used to connect the DC / AC conversion unit; The controller is used to control the trip switch corresponding to the faulty photovoltaic string to trip and drive the multiple sub-switches included therein to disconnect when a reverse connection or short circuit fault occurs in the photovoltaic string, so as to disconnect the electrical connection between the faulty photovoltaic string and the corresponding DC / DC conversion unit, and to ensure that at most three photovoltaic strings corresponding to the tripped trip switch are connected in parallel.

2. The photovoltaic system according to claim 1, characterized in that: The photovoltaic inverter also includes a plurality of DC switches, wherein the DC switches are connected between the DC input terminal and the DC / DC conversion unit, one DC switch is connected to a pair of the DC input terminals correspondingly, the DC switch is connected to the DC / DC conversion unit one-to-one, or a plurality of the DC switches are connected to one DC / DC conversion unit correspondingly.

3. The photovoltaic system according to claim 2, characterized in that: The photovoltaic inverter further includes a control unit, and when a short circuit or overcurrent fault occurs in the photovoltaic inverter, the control unit is used to control the multiple DC switches to be disconnected.

4. The photovoltaic system according to any one of claims 1 to 3, characterized in that: When the current converging device includes a pair of output terminals, all of the plurality of sub-switches are connected to a pair of DC input terminals through the pair of output terminals.

5. The photovoltaic system according to claim 4, characterized in that: The merging device also includes a pair of DC busbars and a busbar switch, wherein the DC busbar is connected between the multiple sub-switches and the output terminals, the pair of DC busbars includes a first busbar and a second busbar, and the busbar switch is connected to at least one of the first busbar and the second busbar.

6. The photovoltaic system according to claim 4, characterized in that: Each pair of the input terminals is used to connect one photovoltaic string, and each pair of the input terminals includes a first input terminal and a second input terminal, wherein the first input terminal is used to connect to a first pole of the photovoltaic string, and the second input terminal is used to connect to a second pole of the photovoltaic string, the first pole is a positive pole or a negative pole, and the second pole is another pole with a polarity opposite to the first pole; The pair of output terminals includes a first output terminal and a second output terminal; The plurality of sub-switches include one or more first sub-switches and a plurality of second sub-switches, wherein the current carrying capacity of the first sub-switches is greater than the current carrying capacity of the second sub-switches; The one or more first sub-switches are used to connect the first input terminals of the plurality of pairs of input terminals with the first output terminal; The plurality of second sub-switches are used to connect the second input terminals of the plurality of pairs of input terminals with the second output terminal, wherein one second sub-switch is connected to at most three second input terminals.

7. The photovoltaic system according to any one of claims 1 to 3, characterized in that: When the busbar device includes N pairs of output terminals, N is greater than or equal to 2, the plurality of sub-switches are divided into N groups, and each group of sub-switches is connected to a pair of DC input terminals via a pair of output terminals.

8. The photovoltaic system according to claim 7, characterized in that: The busbar device also includes N pairs of DC busbars and busbar switches, wherein each pair of the DC busbars is connected between a group of the sub-switches and a pair of the output terminals, each pair of the DC busbars includes a first busbar and a second busbar, and the busbar switch is connected to at least one of the first busbar and the second busbar.

9. The photovoltaic system according to claim 7, characterized in that: Each pair of the input terminals is used to connect one photovoltaic string, and the input terminals include a first input terminal and a second input terminal, wherein the first input terminal is used to connect to a first pole of the photovoltaic string, and the second input terminal is used to connect to a second pole of the photovoltaic string, the first pole is a positive pole or a negative pole, and the second pole is another pole with a polarity opposite to the first pole; The output terminal comprises a first output terminal and a second output terminal; Each group of sub-switches includes one or more first sub-switches and M second sub-switches, wherein M is greater than or equal to 2, and the current carrying capacity of the first sub-switches is greater than the current carrying capacity of the second sub-switches; One or more first sub-switches of each group of the sub-switches are used to connect first input terminals of some pairs of input terminals among the plurality of pairs of input terminals with one of the first output terminals; The M second sub-switches of each group of the sub-switches are used to connect the second input terminals of some pairs of input terminals among the multiple pairs of input terminals with one second output terminal, wherein one second sub-switch is connected to at most three second input terminals.

10. The photovoltaic system according to any one of claims 1-3, 5, 6, 8, and 9, characterized in that: The photovoltaic inverter also includes an AC switch, an AC output end and a control unit. The AC switch is connected between the DC / AC conversion unit and the AC output end. The AC output end is used to connect to a power grid. When a fault occurs in the power grid, the control unit is used to control the AC switch to disconnect.

11. The photovoltaic system according to any one of claims 1-3, 5, 6, 8, and 9, characterized in that: The photovoltaic inverter also includes an energy storage input terminal and a bidirectional DC / DC conversion unit, wherein the energy storage input terminal is used to connect the energy storage unit, one end of the bidirectional DC / DC conversion unit is used to connect the energy storage unit through the energy storage input terminal, and the other end of the bidirectional DC / DC conversion unit is used to connect the DC / AC conversion unit.

12. The photovoltaic system according to claim 6 or 9, characterized in that: The number of the first sub-switches among the plurality of sub-switches is less than the number of the second sub-switches, and the number of the photovoltaic strings connected by the first sub-switches is greater than the number of the photovoltaic strings connected by the second sub-switches.

13. The photovoltaic system according to claim 6 or 9, characterized in that: The current carrying capacity of the first sub-switch is greater than the current carrying capacity of the second sub-switch.

14. The photovoltaic system according to claim 13, characterized in that: Along the stacking direction of the first sub-switch and the second sub-switch, the thickness of the first sub-switch is greater than the thickness of the second sub-switch, and / or the projection area of ​​the first sub-switch is greater than the projection area of ​​the second sub-switch.

15. The photovoltaic system according to claim 13, characterized in that: Each of the multiple sub-switches includes a shell, a moving contact, a first static contact, a second static contact and a wiring portion. The moving contact, the first static contact and the second static contact are accommodated in the shell, and the wiring portion is exposed and fixed to the shell. The first static contact and the second static contact are opposite to each other and are both arranged on the rotation path of the moving contact. The wiring portion is electrically connected to the first static contact, and the surface area of ​​the wiring portion corresponding to the first sub-switch is greater than the surface area of ​​the wiring portion corresponding to the second sub-switch.

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