Photovoltaic system

Abstract

Provided in the present application is a photovoltaic system, comprising a plurality of combiner apparatuses and a photovoltaic inverter. Each combiner apparatus comprises a plurality of pairs of input terminals, a trip switch, an output terminal and a controller, wherein the input terminals are used for connecting to a 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 terminal. The photovoltaic inverter comprises a plurality of pairs of direct-current (DC) input ends and a plurality of DC / DC conversion units, wherein the DC input ends are used for connecting to the output terminal, and one end of each DC / DC conversion unit is used for connecting to at least some of the sub-switches in one or more combiner apparatuses by means of the DC input ends and the output terminal sequentially, and the other ends of the plurality of DC / DC conversion units are connected in parallel. The controller is used for controlling, when a fault occurs in the photovoltaic string, the trip switch corresponding to a faulty photovoltaic string to trip and driving the plurality of sub-switches comprised therein to open, so as to cut off the electrical connection between the faulty photovoltaic string and the photovoltaic inverter.

Description

A photovoltaic system

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411500978.4, filed on October 25, 2024, entitled "A Photovoltaic System", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of new energy power generation, and in particular to a photovoltaic system. Background Technology

[0004] With the rapid development of the new energy field, photovoltaic (PV) power generation systems are being used more and more. As the core equipment of a PV power generation system, the PV inverter is used to convert direct current (DC) from PV modules into alternating current (AC) and transmit the AC power to the power grid. Currently, the industry includes two mainstream types of PV inverters: centralized PV inverters and string PV inverters. Centralized PV inverters have advantages such as high power output (above 1 MW) and low overall cost. However, the maximum power point tracking (MPPT) voltage range of centralized PV inverters is narrow, making it impossible to monitor the operation of each PV string. Therefore, not every PV string can operate at its maximum power point, reducing power generation. Furthermore, to ensure wiring safety, a combiner box needs to be installed between the PV modules and the centralized PV inverter. High-current circuit breakers and fuses also need to be installed in both the combiner box and the centralized inverter, significantly increasing the hardware cost and maintenance difficulty of the PV power generation system. In contrast, string photovoltaic inverters have a wide MPPT voltage range and flexible configuration, but the number of photovoltaic strings that can be connected to a string photovoltaic inverter is limited, making it difficult to increase power output. Summary of the Invention

[0005] Based on the above-mentioned technical problems, this application provides a photovoltaic system that not only has a large power rating, but also has advantages such as small footprint, convenient installation and transportation, low hardware cost, and high safety performance.

[0006] In a first aspect, this application provides a photovoltaic system including multiple combiner devices and a photovoltaic inverter. Each combiner device includes multiple pairs of input terminals, a trip switch, one or more pairs of output terminals, and a controller. The input terminals are used to connect to a photovoltaic string, and the output terminals are connected to the photovoltaic inverter. The trip switch includes multiple stacked sub-switches connected between the multiple pairs of input terminals and the output terminals. The photovoltaic inverter includes multiple pairs of DC input terminals, multiple DC / DC / DC conversion units, and one or more DC / AC conversion units. The DC input terminals are used to connect to the output terminals of the combiner devices. One end of each DC / DC conversion unit is used to connect sequentially through the DC input terminal and the output terminal to at least some of the sub-switches in the one or more combiner devices. The other ends of the multiple DC / DC conversion units are connected in parallel to connect to the DC / AC conversion unit. The controller is used to trip the trip switch corresponding to the faulty photovoltaic string when a reverse connection or short circuit fault occurs in the photovoltaic string, and drive the multiple sub-switches included therein to disconnect the electrical connection between the faulty photovoltaic string and the corresponding DC / DC converter unit, and to ensure that there are at most three parallel connections of the photovoltaic string corresponding to the tripped trip switch.

[0007] The aforementioned photovoltaic system connects multiple photovoltaic strings and DC / DC converter units by incorporating a trip switch consisting of multiple stacked sub-switches within the combiner unit. This allows for the proactive activation of multiple sub-switches to simultaneously disconnect in the event of a fault in one or more photovoltaic strings. This promptly severs the electrical connection between the faulty photovoltaic string and the corresponding DC / DC converter unit, effectively cutting off reverse current or overcurrent paths and preventing the propagation of reverse connection or short-circuit faults to the DC / DC converter unit, thus improving the safety of the photovoltaic system. Furthermore, the compact arrangement of the multiple sub-switches within the trip switch saves space in the combiner unit, significantly reducing its size. Finally, by incorporating multiple DC / DC converter units within the photovoltaic inverter, each connecting to at least one combiner unit, the DC / DC converter unit can selectively perform MPPT (Multi-Level Testing) on ​​the connected photovoltaic strings, thereby increasing the overall power generation of the photovoltaic system.

[0008] In one possible implementation, the photovoltaic inverter also includes multiple DC switches connected between the DC input terminals and the DC / DC conversion unit. Each DC switch is connected to a pair of DC input terminals, and each DC switch is connected to a DC / DC conversion unit in a one-to-one correspondence. Alternatively, multiple DC switches may be connected to a single DC / DC conversion unit. By using DC switches, maintenance of the photovoltaic inverter can be facilitated. For example, when the photovoltaic inverter needs repair due to a fault, the electrical connection between the photovoltaic inverter and the corresponding combiner device can be disconnected by opening the DC switches. This means there is no need to unplug the cable between the combiner device and the photovoltaic inverter, thus avoiding the safety risks associated with misoperation during rewiring after maintenance.

[0009] In one possible implementation, the photovoltaic inverter also includes a control unit that, when a short circuit or overcurrent fault occurs in the photovoltaic inverter, controls multiple DC switches to disconnect. This configuration prevents internal faults in the photovoltaic inverter from spreading to multiple combiner devices, thereby improving the safety of the photovoltaic system.

[0010] In one possible implementation, when the combiner unit includes a pair of output terminals, all of the multiple sub-switches are connected to a pair of DC input terminals through the pair of output terminals. This configuration simplifies the internal wiring of the combiner unit and also simplifies the wiring between the combiner unit and the photovoltaic inverter, thereby reducing safety risks caused by wiring errors.

[0011] In one possible implementation, the combiner unit further includes a pair of DC buses and a bus switch. The DC buses connect multiple sub-switches to the output terminals. The pair of DC buses includes a first bus and a second bus. The bus switch is connected to at least one of the first bus and the second bus. By including a bus switch, the reliability and maintainability of the combiner unit can be further improved. For example, when a photovoltaic string malfunctions, the controller can further disconnect the bus switch, thereby avoiding safety risks caused by insufficient tripping of the trip switch. Similarly, when maintenance of the combiner unit is required and the photovoltaic string is still connected to the combiner unit, maintenance personnel can manually disconnect the bus switch in addition to manually disconnecting the trip switch, thereby avoiding the risk of electric shock.

[0012] In one possible implementation, each pair of input terminals is used to connect one photovoltaic string. Each pair of input terminals includes a first input terminal and a second input terminal. The first input terminal is connected to a first pole of the photovoltaic string, and the second input terminal is connected to a second pole of the photovoltaic string. The first pole is either positive or negative, and the second pole is the opposite pole in polarity. A pair of output terminals includes a first output terminal and a second output terminal. Multiple sub-switches include one or more first sub-switches and multiple second sub-switches, wherein the current-carrying capacity of the first sub-switches is greater than that of the second sub-switches. One or more first sub-switches are used to connect the first input terminals and first output terminals of multiple pairs of input terminals. Multiple second sub-switches are used to connect the second input terminals and second output terminals of multiple pairs of input terminals, wherein one second sub-switch is connected to at most three second input terminals. That is, multiple first input terminals share the same first sub-switch. This configuration allows for timely fault clearing in case of reverse connection or overcurrent faults in the photovoltaic string, while also saving on the number of switches, thus reducing the size of the combiner device and simplifying the wiring between the first input terminals and the first sub-switches.

[0013] In one possible implementation, when the busbar includes N pairs of output terminals, where N is greater than or equal to 2, multiple sub-switches are divided into N groups, with each group of sub-switches connected to a pair of DC input terminals via a pair of output terminals. By grouping the sub-switches, the current value carried by each first sub-switch during normal operation of the busbar is reduced, thus lowering the requirements for selecting the first sub-switch.

[0014] In one possible implementation, the busbar device further includes N pairs of DC buses and bus switches, wherein each pair of DC buses is connected between a set of sub-switches and a pair of output terminals, each pair of DC buses includes a first bus and a second bus, and the bus switch is connected to at least one of the first bus and the second bus. As described above, by providing bus switches, the reliability and maintainability of the busbar device can be further improved.

[0015] In one possible implementation, each pair of input terminals is used to connect one photovoltaic string. The input terminals include a first input terminal and a second input terminal. The first input terminal is connected to a first pole of the photovoltaic string, and the second input terminal is connected to a second pole of the photovoltaic string. The first pole is either positive or negative, and the second pole is the opposite pole in polarity. Output terminals include 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, where M is greater than or equal to 2. The current-carrying capacity of the first sub-switches is greater than that of the second sub-switches. One or more first sub-switches in each group of sub-switches are used to connect the first input terminals of some of the input pairs to a first output terminal. The M second sub-switches in each group of sub-switches are used to connect the second input terminals of some of the input pairs to a second output terminal, where a second sub-switch is connected to at most three second input terminals. Because the current-carrying capacity of the first sub-switches is greater than that of the second sub-switches, the number of first sub-switches used can be reduced, thereby reducing the size of the tripping switch and facilitating the miniaturization of the combiner device.

[0016] In one possible implementation, the photovoltaic inverter further includes an AC switch, an AC output terminal, and a control unit. The AC switch is connected between the DC / AC conversion unit and the AC output terminal, which is used to connect to the power grid. When a grid fault occurs, the control unit controls the AC switch to disconnect. With this configuration, when a grid fault or a fault occurs within the photovoltaic inverter, the control unit controls the AC switch to disconnect, thereby preventing a faulty grid from affecting the photovoltaic inverter, or preventing the photovoltaic inverter from spreading the fault to the grid side, thus improving the safety performance of the photovoltaic system.

[0017] In one possible implementation, the photovoltaic inverter also includes an energy storage input terminal and a bidirectional DC / DC conversion unit. The energy storage input terminal is used to connect to an energy storage unit, one end of the bidirectional DC / DC conversion unit is used to connect to the energy storage unit via the energy storage input terminal, and the other end of the bidirectional DC / DC conversion unit is used to connect to a DC / AC conversion unit. It is worth noting that many countries mandate a certain proportion of energy storage batteries in photovoltaic power plant construction to proactively support the grid during grid failures. Therefore, by incorporating a bidirectional DC / DC conversion unit within the photovoltaic inverter, the need for an additional energy storage converter for the photovoltaic system can be eliminated, simplifying the installation of the photovoltaic power plant and improving its integration.

[0018] In one possible implementation, the number of first sub-switches in the plurality of sub-switches is less than the number of second sub-switches, and the number of photovoltaic strings connected by the first sub-switches is greater than the number of photovoltaic strings connected by the second sub-switches. This arrangement reduces the number of sub-switches in the trip switch, thus reducing the size of the trip switch and the combiner unit.

[0019] In one possible implementation, the current-carrying capacity of the first sub-switch is greater than that of the second sub-switch. Similarly, this arrangement can reduce the number of sub-switches in the trip switch, thereby reducing the size of the trip switch and the busbar device.

[0020] In one possible implementation, along the stacking direction of the first and second sub-switches, the thickness of the first sub-switch is greater than the thickness of the second sub-switch, and / or, the projected area of ​​the first sub-switch is greater than the projected area of ​​the second sub-switch. Similarly, this arrangement can reduce the number of sub-switches in the trip switch, thereby reducing the volume of the trip switch and the busbar device.

[0021] In one possible implementation, each sub-switch in a multi-sub-switch system 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 housed within the housing, while the wiring portion is exposed and fixed to the housing. The first and second stationary contacts are opposite each other and both are positioned along 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 larger than the surface area of ​​the wiring portion corresponding to the second sub-switch. Similarly, this configuration can reduce the number of sub-switches in a trip switch, thereby reducing the size of the trip switch and the busbar device.

[0022] In summary, the photovoltaic system provided in this application greatly simplifies the structure of the combiner unit and the photovoltaic inverter, facilitating equipment transportation and installation while ensuring high safety performance of the photovoltaic system. At the same time, since both the combiner unit and the photovoltaic inverter are exempt from fuses, the construction cost and subsequent maintenance difficulty of the photovoltaic power station are significantly reduced. Attached Figure Description

[0023] Figure 1 is a schematic diagram of the structure of a centralized photovoltaic power generation system;

[0024] Figure 2 is a schematic diagram of the combiner box in a centralized photovoltaic power generation system;

[0025] Figure 3 is a schematic diagram of the structure of a centralized inverter in a centralized photovoltaic power generation system;

[0026] Figure 4 is a schematic diagram of a photovoltaic system provided in an embodiment of this application;

[0027] Figure 5 is a schematic diagram of another structure of the photovoltaic system provided in the embodiment of this application;

[0028] Figure 6 is a schematic diagram of a combiner device in a photovoltaic system provided in an embodiment of this application;

[0029] Figure 7 is a schematic diagram of another structure of the combiner device in the photovoltaic system provided in the embodiment of this application;

[0030] Figure 8 is a schematic diagram of a photovoltaic inverter in a photovoltaic system provided in an embodiment of this application;

[0031] Figure 9 is a schematic diagram of another structure of the photovoltaic system provided in the embodiment of this application;

[0032] Figure 10 is a schematic diagram of another structure of the photovoltaic system provided in the embodiment of this application;

[0033] Figure 11 is a schematic diagram of another structure of the photovoltaic system provided in the embodiment of this application;

[0034] Figure 12 is a schematic diagram of another structure of the photovoltaic system provided in the embodiment of this application;

[0035] Figure 13 is a schematic diagram of another structure of the photovoltaic system provided in the embodiment of this application;

[0036] Figure 14 is one of the structural schematic diagrams of the trip switch in the combiner device of the photovoltaic system provided in the embodiments of this application;

[0037] Figure 15 is a second schematic diagram of the structure of the trip switch in the combiner device of the photovoltaic system provided in the embodiment of this application;

[0038] Figure 16 is an exploded view of the trip switch shown in Figures 14 and 15;

[0039] Figure 17 is a schematic diagram of the structure of the first sub-switch in Figures 14-16;

[0040] Figure 18 is a schematic diagram of the structure of the second sub-switch in Figures 14-16. Detailed Implementation

[0041] Referring to Figure 1, which is a schematic diagram of a centralized photovoltaic (PV) power generation system, the system includes PV modules, combiner boxes, a centralized inverter, a transformer, and a power grid. The PV modules convert solar energy into direct current (DC) and transmit it to the combiner box. The combiner box ensures the orderly connection and collection of PV modules and transmits the collected DC power to the centralized inverter. The centralized inverter converts the DC power into alternating current (AC) and transmits it to the transformer. The transformer steps up the AC output from the centralized inverter and transmits the stepped-up AC power to the power grid, ultimately achieving AC grid connection.

[0042] Referring to Figure 2, which is a schematic diagram of the combiner box in Figure 1, it is worth noting that in a centralized photovoltaic power generation system, in addition to its connection and current collection functions, the combiner box can also disconnect the electrical connection between the photovoltaic strings and the centralized inverter when faults such as reverse connection or short circuit occur in the photovoltaic strings. This prevents the fault in the photovoltaic strings from spreading to the centralized inverter, ensuring the power supply safety of the centralized photovoltaic power generation system. Specifically, the combiner box includes multiple input terminals 10, multiple fuses 11, a molded case circuit breaker 12, and an output terminal 13. The multiple input terminals 10 are used to connect the photovoltaic strings, and they are also used to connect one end of the multiple fuses 11. The other ends of the multiple fuses 11 are connected in parallel to the molded case circuit breaker 12. The terminals 121 of the molded case circuit breaker 12 are further electrically connected to the output terminal 13, thereby transmitting the collected DC power to the downstream centralized inverter through the output terminal 13. When a photovoltaic (PV) module experiences a reverse connection or short circuit fault, the DC current generated by other PV strings connected in parallel with the faulty PV string will directly flow into the faulty PV string, causing the fuse 11 connected in series with the faulty PV module to overheat and burn out, thus cutting off the overcurrent path. While this design prevents the PV string with a reverse connection or short circuit fault from burning out due to overcurrent, the fuse 11 is a one-time use device. To ensure the power generation of the centralized PV power generation system, maintenance personnel still need to be dispatched to replace the fuse 11, increasing the difficulty and cost of maintenance. Before replacing the fuse 11, maintenance personnel must switch the molded case circuit breaker 12 to the open state to avoid accidental electric shock and ensure the personal safety of maintenance personnel. After replacing the fuse 11, maintenance personnel must switch the molded case circuit breaker 12 back to the closed state. Based on this, it can be seen that the existing combiner 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 combiner box also needs to be equipped with a molded case circuit breaker 12 with a large current carrying capacity, which increases the size of the combiner box and the hardware cost.

[0043] Referring to Figure 3, which is a structural schematic of the centralized inverter shown in Figure 1, the centralized inverter includes multiple bus cables 21, multiple fuses 22, a power distribution switch 23, and a power converter 24. One end of each bus cable 21 is connected to a combiner box, and the other end is connected to a corresponding fuse 22. Multiple fuses 22 are connected in parallel to the power distribution switch 23, which in turn is connected to the power converter 24. When a combiner box experiences a reverse connection or short circuit fault, the DC current transmitted from other combiner boxes connected in parallel with the faulty combiner box will directly flow into the faulty combiner box, causing the fuse 22 connected in series with the faulty combiner box to overheat and burn out, thus cutting off the overcurrent path. Similar to the combiner box, while the use of fuses 22 can prevent the faulty combiner box from burning out due to overcurrent, it still requires maintenance personnel to replace the fuses 22, increasing the difficulty and cost of maintenance. Furthermore, the multiple bus cables 21 and fuses 22 occupy a significant amount of space inside the centralized inverter, resulting in an excessively large overall size that hinders its transportation and installation. Similarly, maintenance personnel must switch the power distribution switch 23 to the open state before replacing fuse 22, and then switch it back to the closed state after replacement to restore normal operation of the centralized inverter. It is worth noting that the power distribution switch 23 typically has an automatic tripping function. For example, in the event of a short circuit fault inside the centralized inverter, when the current flowing through the power distribution switch 23 exceeds a certain threshold, the switch can trip in time, thus preventing the short circuit fault from spreading. Further, the power converter 24 is used for MPPT (Multi-Pulse Test) and also for converting DC power to AC power. As mentioned in the background section, since multiple combiner boxes are connected to the power converter 24 via the distribution switch 23, the power converter 24 cannot perform MPPT (Maximum Power Point Tracking) specifically for each combiner box. This means it cannot guarantee that each combiner box operates at its maximum power point, reducing the power generation of the centralized photovoltaic power generation system. Simultaneously, the power converter 24 typically performs MPPT and DC-to-AC conversion simultaneously. However, to prioritize DC-to-AC conversion, the power converter 24 cannot maintain MPPT continuously, thus reducing the power generation of the centralized photovoltaic power generation system. In summary, existing centralized inverters are large, difficult to transport, complex to operate and maintain, have a narrow MPPT tracking range, high hardware costs, and cannot meet the development trend of simplified, safe, and efficient operation and maintenance of photovoltaic power plants.

[0044] To address the aforementioned problems of existing centralized photovoltaic power generation systems, this application proposes a photovoltaic system that possesses both a large power output and advantages such as small size, high safety level, and convenient operation and maintenance. The photovoltaic system provided in this application will be described in detail below with reference to Figures 4-18.

[0045] Referring to Figure 4, which is a schematic diagram of a photovoltaic system provided in an embodiment of this application, the photovoltaic system includes multiple combiner devices 3 and a photovoltaic inverter 4. Each combiner device 3 includes multiple 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 to one photovoltaic string. 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 to the positive terminal of the photovoltaic string, and the second input terminal 312 is used to connect to the negative terminal of the photovoltaic string. It should be noted that a photovoltaic string is generally composed of multiple photovoltaic modules connected in series or parallel. The positive and negative terminals of the photovoltaic string are the exposed positive and negative terminals of the multiple photovoltaic modules connected in series. The trip switch 32 includes multiple sub-switches stacked together. These sub-switches include a first sub-switch S1 and multiple second sub-switches S2. One end of the first sub-switch S1 is used to connect to all the first input terminals 311 of the combiner device 3, and one end of each second sub-switch S2 is used to connect to two second input terminals 312 of the combiner device 3. Further, the output terminals 33 are used to connect to the photovoltaic inverter 4. A pair of output terminals 33 includes a first output terminal 331 and a second output terminal 332. The first output terminal 331 is used to connect to the other end of the first sub-switch S1 via a first bus (positive DC bus BUS+) of a pair of DC buses, and the second output terminal 332 is used to connect to the other ends of all the second sub-switches S2 in the combiner device 3 via a second bus (negative DC bus BUS-) of a pair of DC buses.

[0046] In the photovoltaic system shown in Figure 4, when the connection between the photovoltaic strings and the combiner device 3 is normal and the combiner device 3 is working normally, the DC current generated by all the photovoltaic strings connected to the combiner device 3 flows out from the positive terminal and flows together through the first sub-switch S1 to the first bus and the first output terminal 331. Subsequently, the DC current flows through the photovoltaic inverter 4 and back to the combiner device 3 through the second output terminal 332 and the second bus. Further, the DC current is split and flows through multiple second sub-switches S2, and finally flows back to the negative terminal of each photovoltaic string. At this time, the current direction flowing through the first sub-switch S1 and the current direction of the second sub-switch S2 are both positive currents. For the first sub-switch S1, the direction of the positive current is from the input terminal 31 to the output terminal 33, and for the second sub-switch S2, the direction of the positive current is from the output terminal 33 to the input terminal 31.

[0047] When a photovoltaic string connected to a pair of input terminals 31 experiences a reverse connection or short circuit fault, the DC 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 its positive terminal, directly to the first input terminal 311 corresponding to the faulty photovoltaic string, and through the faulty photovoltaic string. Subsequently, the DC current passes through the second input terminal 312 corresponding to the faulty photovoltaic string and finally flows back to the negative terminal of the aforementioned photovoltaic string. Similarly, the DC current generated by other photovoltaic strings that do not share the same second sub-switch S2 with the faulty photovoltaic string flows out from its positive terminal, directly to the first input terminal 311 corresponding to the faulty photovoltaic string, and through the faulty photovoltaic string. Subsequently, the DC 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 DC current returns to the negative terminal of the photovoltaic string through the second sub-switch S2 corresponding to that photovoltaic string. It is worth noting that the direction of the DC 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, which is opposite to the direction of the forward current. This current is called the reverse current. Based on this, it can be understood that when a photovoltaic string connected to a pair of input terminals 31 experiences a reverse connection fault or a short circuit fault, all the DC current generated by other photovoltaic strings will flow into the faulty photovoltaic string. Simultaneously, the second sub-switch S2 corresponding to the faulty photovoltaic string will receive current from photovoltaic strings that do not share the second sub-switch S2 with the faulty photovoltaic string. At this time, the current received by the second sub-switch S2 corresponding to the faulty photovoltaic string is the reverse current, and the value of the reverse current will increase sharply.

[0048] Therefore, to prevent photovoltaic strings from malfunctioning or burning out due to reverse connection or short circuit, the combiner device 3 also includes a controller 34. Specifically, referring to Figure 4, when a photovoltaic string connected to the combiner device 3 experiences a reverse connection or short circuit fault, the second sub-switch S2 corresponding to the faulty photovoltaic string will experience reverse current or overcurrent. The controller 34, based on the reverse current or overcurrent signal, controls the trip switch 32 to trip, causing multiple sub-switches included in the trip switch 32 to open, thereby disconnecting the electrical connection between the faulty photovoltaic module and the photovoltaic inverter 4, preventing the fault from spreading to the photovoltaic inverter 4. Furthermore, after the multiple sub-switches included in the trip switch 32 open, 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, thus preventing other photovoltaic strings from feeding back current into the faulty photovoltaic string. It is worth mentioning that, in order to detect the occurrence of reverse current or overcurrent in a timely manner, the combiner device 3 is also equipped with a sensor (not shown). When the sensor detects that the current flowing through a certain sub-switch is a reverse current, or when the sensor detects that the current flowing through a certain sub-switch exceeds a set threshold, the sensor is used to send a reverse current or overcurrent signal to the controller 34. It is also worth mentioning that, although the photovoltaic string sharing the same second sub-switch S2 with the faulty photovoltaic string will still send reverse current to the faulty photovoltaic string, the faulty photovoltaic string can withstand the reverse current from the faulty photovoltaic string, so there is no risk of the photovoltaic string burning out.

[0049] It should be noted that a photovoltaic string can typically withstand the reverse current from two other photovoltaic strings connected in parallel. In other words, in practical applications, one end of the second sub-switch S2 can connect to a maximum of three second input terminals 312. Therefore, when a photovoltaic string experiences a reverse connection or short circuit fault, and all the sub-switches included in the trip switch 32 are open, there will be at most three photovoltaic strings connected in parallel. Of course, after all the sub-switches included in the trip switch 32 are open, depending on the connection relationship between the actual input terminals 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 connected in parallel.

[0050] Furthermore, in the photovoltaic system shown in Figure 4, one end of each second sub-switch S2 is used to connect to two second input terminals 312 of the combiner device 3. In practical applications, the number of second input terminals 312 of the combiner device 3 connected to one end of each second sub-switch S2 can be different (as long as it is less than or equal to 3), or one end of each second sub-switch S2 can be used to connect to three second input terminals 312 of the combiner device 3, thereby improving the adaptability and flexibility of the combiner device 3.

[0051] It is worth mentioning that, in order to save on the number of sub-switches and reduce the size 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-switches S1 and second sub-switches S2 have the same current-carrying capacity and can withstand the sum of the currents of five or six photovoltaic strings, 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 a maximum of three second input terminals 312. If the combiner device 3 includes more than five or six pairs of input terminals 31, then the number of first sub-switches S1 needs to be increased.

[0052] In other embodiments of the present invention, to further reduce the number of sub-switches, the current-carrying capacity of the first sub-switch S1 and the second sub-switch S2 differs, that is, the current-carrying capacity of the first sub-switch S1 is greater than that 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 connected to the first sub-switch S1 is much larger than the number of second input terminals 312 connected to the second sub-switch S2. When the current-carrying capacity of the first sub-switch S1 is sufficiently large, it is feasible for a trip switch 32 to include only one first sub-switch S1. For example, in Figure 4, all the first input terminals 311 of the busbar 3 are connected to one first sub-switch S1. It should also be explained that the current-carrying capacity of a sub-switch is positively correlated with the maximum current that the sub-switch can withstand. By matching the first sub-switches S1 and 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 while ensuring the safety of the trip switch 32.

[0053] Referring again to Figure 4, the photovoltaic inverter 4 includes multiple pairs of DC input terminals 41, multiple DC / DC conversion units 42, one DC / AC conversion unit 43, and one AC output terminal 44. The DC input terminals 41 are used to connect to the output terminals 33 of the combiner device 3. Each pair of DC input terminals 41 includes a first DC input terminal 411 and a second DC input terminal 412. 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 and output terminals 33 are connected in a one-to-one correspondence. One end of the DC / DC converter unit 42 is connected sequentially to multiple sub-switches included in the trip switch 32 via a DC input terminal 41 and an output terminal 33. The other ends of the multiple DC / DC converter units 42 are connected in parallel to connect to the DC / AC converter unit 43. The DC / DC converter unit 42 is used to convert the DC power transmitted by the corresponding combiner device 3 into DC power with a suitable voltage. The DC / AC converter unit 43 is used to convert the DC power converted by the multiple DC / DC converter 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 converter unit 42 for each combiner device 3, so that each combiner device 3 can operate independently at the maximum power point, thereby improving the power generation of the photovoltaic system. At the same time, the DC / DC converter unit 42 undertakes the MPPT function, while the DC / AC converter unit 43 performs the DC to AC conversion. Therefore, the MPPT function of the DC / DC converter unit 42 is independent of the DC / AC converter unit 43, so the MPPT can be maintained for a long time, thereby improving the power generation of the photovoltaic power generation system. Furthermore, by setting multiple DC / DC conversion units 42, backflow between multiple combiner devices 3 connected to the photovoltaic inverter 4 can be avoided. For example, when a combiner device 3 is reverse-connected to the photovoltaic inverter 4 (i.e., the first output terminal 331 of the combiner device 3 is connected to the second DC input terminal 412 of the photovoltaic inverter 4, and the second output terminal 332 of the combiner 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 reverse-connected combiner device 3 can block backflow current from other combiner devices 3, improving the safety of the photovoltaic system. The situation is similar to the case of a combiner device 3 being reverse-connected to the photovoltaic inverter 4, and will not be described further here.

[0054] Referring again to Figure 4, the photovoltaic inverter 4 also includes multiple DC switches S3, each connected between a pair of DC input terminals 41 and a DC / DC conversion unit 42. Notably, each DC switch S3 includes two switching units: one connected between the first DC input terminal 411 and the DC / DC conversion unit 42, and the other connected between the second DC input terminal 412 and the DC / DC conversion unit 42. In practical applications, at least one switching unit is sufficient for the DC switch S3. The DC switch S3 facilitates the maintenance of the photovoltaic inverter 4. For example, when the photovoltaic inverter 4 needs repair due to a fault, the electrical connection between the photovoltaic inverter 4 and the corresponding combiner device 3 can be disconnected by opening the DC switch S3. This means there is no need to unplug the cable between the combiner device 3 and the photovoltaic inverter 4, thus avoiding the safety risks associated with misoperation during rewiring after maintenance.

[0055] Referring again to Figure 4, the photovoltaic inverter 4 also includes a control unit 45. Specifically, when a fault such as a short circuit or overcurrent occurs inside the photovoltaic inverter 4, the control unit 45 will control multiple DC switches S3 to disconnect based on the short circuit or overcurrent signal, thereby disconnecting the electrical connection between multiple combiner devices 3 and the corresponding DC / DC conversion unit 42, preventing the internal fault of the photovoltaic inverter 4 from spreading to multiple combiner devices 3.

[0056] Referring again to 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 noting that when the AC grid is a three-phase three-wire system, there are three AC switches S4, which are respectively connected to the A-phase, B-phase, and C-phase cables. Specifically, when the photovoltaic inverter 4 is operating normally, the AC switch S4 is closed, allowing the AC power output from the DC / AC conversion unit 43 to be smoothly transmitted to the grid. When a grid fault occurs or a fault occurs inside the photovoltaic inverter 4, the control unit 45 controls the AC switch S4 to open, thereby preventing the faulty grid from affecting the photovoltaic inverter 4, or preventing the photovoltaic inverter 4 from spreading the fault to the grid side, thus improving the safety performance of the photovoltaic system.

[0057] In the photovoltaic system shown in Figure 4, to further improve the safety performance of the photovoltaic system, the combiner unit 3 and the photovoltaic inverter 4 can communicate. Specifically, when the photovoltaic inverter 4 malfunctions, or when the photovoltaic inverter 4 needs to be actively shut down due to a grid fault, the photovoltaic inverter 4 sends a first fault signal to the combiner unit 3. Subsequently, the controller 34 within the combiner unit 3 controls all sub-switches included in the trip switch 32 to open, thereby effectively preventing the spread and propagation of the fault and improving the safety of the photovoltaic system. Similarly, when the photovoltaic string or the combiner unit 3 malfunctions, the combiner unit 3 sends a second fault signal to the photovoltaic inverter 4. Subsequently, the control unit 45 within the photovoltaic inverter 4 controls all DC switches S3 to open, thereby effectively preventing the spread and propagation of the fault and improving the safety of the photovoltaic system.

[0058] It is understood that in the photovoltaic system provided in this application embodiment, the combiner device 3 is exempt from the multiple fuses 11 and molded case circuit breakers 12 shown in FIG. 2. Therefore, the size of the combiner device 3 is significantly reduced, facilitating its transportation, simplifying its later maintenance, and lowering its hardware cost. Furthermore, in the photovoltaic system provided in this application embodiment, the photovoltaic inverter 4 is exempt from the multiple fuses 22 and distribution switches 23 shown in FIG. 3. Therefore, the size of the photovoltaic inverter 4 is significantly reduced, facilitating its transportation, ensuring that multiple combiner devices 3 can operate independently at their maximum power point, and improving the overall power generation of the photovoltaic system.

[0059] Referring to Figure 5, which is a schematic diagram of a photovoltaic system provided in this application, the combination device 3 shown in Figure 5 differs from the photovoltaic system shown in Figure 4 in that 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. Further, one end of each first sub-switch S1 is used to connect to a portion of the first input terminal 311, and the other ends of the two first sub-switches S1 are connected in parallel to the same first output terminal 331. One end of each second sub-switch S2 is used to connect to a second input terminal 312, and the other ends of the multiple second sub-switches S2 are connected in parallel 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. This configuration reduces the number of output terminals, simplifies the connection between the combination device 3 and the photovoltaic inverter 4, reduces connection costs, and also reduces the risk caused by incorrect wiring between the combination device 3 and the photovoltaic inverter 4. It is worth mentioning that only two first sub-switches S1 are shown in Figure 5. In actual applications, the number of first sub-switches S1 can be set as needed.

[0060] Referring to Figure 6, which is a schematic diagram of a combiner device 3 provided in this application, the combiner device 3 shown in Figure 4 differs from the combiner device 3 shown in Figure 6 in that it also includes a bus switch S5. The bus switch S5 includes two small switches, one of which is connected to the first bus, i.e., BUS+, and the other of which is connected to the second bus, i.e., 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 combiner device 3 can be further improved. For example, when a photovoltaic string fails, the controller 34 can not only control the trip switch 32 to open, but also further control the bus switch S5 to open, thereby avoiding the safety risks caused by insufficient opening of the trip switch 32. At the same time, it also disconnects the electrical connection between the photovoltaic inverter 4 and the trip switch 32, reducing the risk of electric shock. Similarly, when maintenance is required on combiner device 3 and the photovoltaic string is still connected to combiner device 3, maintenance personnel can manually disconnect trip switch 32 and further manually disconnect bus switch S5 to avoid the risk of electric shock.

[0061] Referring to Figure 7, which is a schematic diagram of a combiner device 3 provided in this application, the combiner device 3 shown in Figure 7 differs from the combiner device 3 shown in Figure 4 in that the first input terminal 311 is used to connect to the negative terminal of the photovoltaic string, and the second input terminal 312 is used to connect to the positive terminal of the photovoltaic string. Further, the first output terminal 331 is used to connect to the first sub-switch S1 via the second DC bus (negative DC bus BUS-) of a pair of DC buses, and the second output terminal 332 is used to connect to all the second sub-switches S2 in the combiner device 3 via the first DC bus (positive DC bus BUS+) of 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 combiner device 3 can be adapted to photovoltaic strings and photovoltaic inverters 4 with different characteristics.

[0062] Referring to Figure 8, which is a structural schematic diagram of a photovoltaic inverter 4 provided in this application, the photovoltaic inverter 4 shown in Figure 8 includes two DC / AC conversion units 43 and six AC switches S4. Three AC switches S4 are connected to phases A, B, and C of one DC / AC conversion unit 43, respectively, while the remaining three AC switches S4 are connected to phases A, B, and C of the other DC / AC conversion unit 43. Specifically, when the power rating of the photovoltaic inverter 4 is large, additional DC / AC conversion units 43 can be added to avoid overloading a single DC / AC conversion unit 43, thereby ensuring the normal operation of the photovoltaic inverter 4.

[0063] Referring to Figure 9, which is a schematic diagram of a photovoltaic system provided in this application, the combiner device 3 shown in Figure 4 differs from the combiner device 3 shown in Figure 9 in that it includes two pairs of output terminals 33. Further, in the combiner device 3 shown in Figure 9, the trip switch 32 includes sub-switches divided into two groups: a first group of sub-switches 321 and a second group of sub-switches 322. Multiple pairs of input terminals 31 are also divided into corresponding groups, with each group of sub-switches connected between a group of input terminals 31 and a pair of output terminals 33. Further, each group of sub-switches includes one first sub-switch S1 and M second sub-switches S2, where M is greater than or equal to 2. The first sub-switch S1 of each group is used to connect all the first input terminals 311 in the corresponding group of input terminals 31, and each second sub-switch S2 in each group is used to connect two second input terminals 312 in the corresponding group of input terminals 31. By grouping the sub-switches, the current value carried by each first sub-switch S1 during normal operation of the busbar 3 will also decrease, thus reducing the requirements for selecting the first sub-switch S1. It is worth mentioning that each group of sub-switches in Figure 9 includes one first sub-switch S1 and M second sub-switches S2, where M is greater than or equal to 2. In practical applications, a group of sub-switches may include multiple first sub-switches S1, that is, multiple first sub-switches S1 in each group of sub-switches share the same first output terminal 331.

[0064] It is worth mentioning that, in practical applications, to reduce the number of sub-switches stacked and ensure the stability of sub-switch disconnection, multiple trip switches 32 can be placed in the bus device 3. Each trip switch 32 is used to connect to one or N pairs of output terminals 33, where N is greater than or equal to 2. It is also worth noting that when there are N pairs of output terminals 33, the number of DC buses and bus switches is also N. Furthermore, when one 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, with each group of sub-switches including one or more first sub-switches S1.

[0065] Referring to Figure 10, which is a schematic diagram of a photovoltaic system provided in this application, the photovoltaic inverter 4 shown in Figure 10 differs from the photovoltaic inverter 4 shown in Figure 9 in that each DC / DC conversion unit 42 is connected to two pairs of DC input terminals 41. It is worth noting 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, i.e., the number of output terminals 33 connected to each DC / DC conversion unit 42, the power rating of each DC / DC conversion unit 42 can be adjusted, thereby optimizing the overall performance, cost, and size of the DC / DC conversion units 42 in the photovoltaic inverter 4.

[0066] Referring to Figure 11, which is a schematic diagram of a photovoltaic system provided in this application, unlike the photovoltaic system shown in Figure 10, in the photovoltaic inverter 4 shown in Figure 11, one DC / DC conversion unit 42 is connected to two combiner devices 3. Specifically, the DC / DC conversion unit 42 is connected to all the sub-switches of one of the combiner devices 3 in sequence through a pair of DC input terminals 41 and a pair of output terminals 33. Furthermore, the DC / DC conversion unit 42 is also connected to some sub-switches (a set of sub-switches) of the other combiner device 3 in sequence through another pair of DC input terminals 41 and another pair of output terminals 33. When the photovoltaic strings corresponding to the two combiner devices 3 are close to each other, the maximum power points of the photovoltaic strings corresponding to the two combiner devices 3 are also close. Therefore, the photovoltaic strings can reuse the same DC / DC conversion unit 42. This arrangement can reduce the number of DC / DC conversion units 42, reduce the hardware cost of the DC / DC conversion units 42, and reduce the size of the photovoltaic inverter 4.

[0067] Referring to Figure 12, which is a schematic diagram of a photovoltaic system provided in this application, unlike the photovoltaic system shown in Figure 11, in the photovoltaic inverter 4 shown in Figure 12, a DC / DC conversion unit 42 is sequentially connected to a portion of the sub-switches (a set of sub-switches) of two combiner devices 3 via two pairs of DC input terminals 41 and two pairs of output terminals 33. When the photovoltaic strings corresponding to the portion of the sub-switches (a set of sub-switches) of the two combiner devices 3 are close to each other, the maximum power points of the photovoltaic strings corresponding to the two combiner devices 3 are also close. Therefore, the photovoltaic strings can reuse the same DC / DC conversion unit 42. This arrangement can reduce the number of DC / DC conversion units 42, reduce the hardware cost of the DC / DC conversion units 42, and reduce the size of the photovoltaic inverter 4.

[0068] Referring to Figure 13, which is a schematic diagram of a photovoltaic system provided in this application, the photovoltaic inverter 4 shown in Figure 13, unlike the photovoltaic inverter 4 shown in Figure 4, also includes multiple pairs of energy storage input terminals 46 and a bidirectional DC / DC conversion unit 47. The bidirectional DC / DC conversion unit 47 is used to connect to the energy storage unit 5 through the energy storage input terminals 46. Furthermore, the energy storage input terminals 46 and the bidirectional DC / DC conversion unit 47 are also equipped with DC switches 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 in the photovoltaic inverter 4 from spreading to the energy storage unit 5. Furthermore, when the energy storage unit 5 fails, it sends a third fault signal to the control unit 45 of the photovoltaic inverter 4. The control unit 45 then controls the DC switches S3 connected to the faulty energy storage unit 5 to disconnect, thereby preventing the fault in the energy storage unit 5 from spreading to the photovoltaic inverter 4. It is worth mentioning that many countries mandate the inclusion of a certain proportion of energy storage batteries in photovoltaic (PV) systems during PV power plant construction, enabling proactive grid support during grid failures. Based on this, by incorporating a bidirectional DC / DC conversion unit 47 within the PV inverter 4, the need for an additional power conversion system (PCS) in the PV system can be eliminated, simplifying the installation of the PV power plant and increasing its integration.

[0069] When the current-carrying capacities of the first sub-switch S1 and the second sub-switch S2 are different, refer to Figures 14-18. Figure 14 is one of the structural schematic diagrams of the trip switch 32 housed in the busbar device 3 in the above embodiments provided in this application. Figure 15 is another structural schematic diagram of the trip switch 32 housed in the busbar device 3 in the above embodiments provided in this application. Figure 16 is a partial exploded structural schematic diagram of the trip switch 32 shown in Figures 14 and 15. Figures 17 and 18 are structural schematic diagrams of the first sub-switch S1 and the second sub-switch S2, respectively. Referring to Figures 14 and 16, the trip switch 32 includes a handle 323, an input shaft 324, a drive mechanism 325, and multiple sub-switches stacked along the first direction A. The handle 323 is fixedly connected to the input shaft 324. When the handle 323 is driven to rotate, it will drive the connecting rod or gear and other transmission mechanism inside the drive mechanism 325 to rotate through the input shaft 324, thereby driving at least part 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.

[0070] Furthermore, referring to Figures 15-18, the first sub-switch S1 and the second sub-switch S2 have largely similar structures, both including a housing S11, a wiring portion S12, a first stationary contact S13, a moving contact S14, a second stationary contact S15, a pin portion S16, and an arc-extinguishing chamber S17. The first stationary contact S13, the moving contact S14, the second stationary contact S15, and the arc-extinguishing chamber S17 are all housed within the housing S11. The wiring portion S12 and the pin portion S16 are exposed and fixed to the housing S11. The wiring portion S12 is electrically connected to the first stationary contact S13, and the pin portion S16 is electrically connected to the second stationary contact S15. The wiring portion S12, the first stationary contact S13, the moving contact S14, the second stationary contact S15, and the pin portion S16 are all metal conductors.

[0071] Specifically, the wiring portion S12, which is one end of the first sub-switch S1 or the second sub-switch S2, is used to connect the first input terminal 311 and the second input terminal 312, respectively. In practical applications, part of the wiring portion S12 can be integrally formed with the first stationary contact S13, thereby simplifying the manufacturing process. Referring again to Figures 17 and 18, the wiring portion S12 has a screw and nut mating structure. 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 screw and nut mating.

[0072] Further, referring to Figure 15, the pin portion S16 is a flat metal protrusion. 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, which is the other end of the first sub-switch S1, is used to connect to the first output terminal 331 of the combiner device 3, and the second pin portion S162, which is the other end of the second sub-switch S2, is used to connect to the second output terminal 332 of the combiner device 3. In practical applications, since the pin portion S16 has a flat protrusion structure, the first pin portion S161 and the second pin portion S162 can be directly inserted into the circuit board and connected to the first output terminal 331 and the second output terminal 332 respectively through the traces on the circuit board. This configuration can eliminate the complex wiring between the trip switch 32 and the output terminal 33, thereby simplifying the installation steps of the combiner device 3.

[0073] Furthermore, the moving contact S14 is drivenly connected to the output shaft and can rotate around the axis of the output shaft. The first stationary contact S13 and the second stationary contact S15 are both arranged on the rotation trajectory of the moving contact S14. Among the multiple sub-switches, the moving contact S14 of the sub-switch closest to the drive mechanism 325 along the first direction A is fixedly connected to the output shaft. The moving contacts S14 of two adjacent sub-switches are sequentially drivenly connected, for example, by snap-fit. 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 on the moving contact S14 of the sub-switch farthest from the drive mechanism 325 along the first direction A among the multiple sub-switches will gradually decrease due to sequential transmission, which may easily lead to poor contact between the moving contact S14 and the first stationary contact S13 and the second stationary 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 stationary contact S13 and the second stationary contact S15 respectively, the trip switch 32 closes, 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 separates from the first stationary contact S13 and the second stationary contact S15, the trip switch 32 opens, and the DC power of the photovoltaic string cannot be transmitted to the photovoltaic inverter 4.

[0074] 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 separates from the first stationary contact S13 and the second stationary contact S15, an electric arc usually occurs. In order to extinguish the arc in time and prevent the arc from damaging the trip switch 32, both the first sub-switch S1 and the second sub-switch S2 need to be equipped with an arc-extinguishing chamber S17.

[0075] Furthermore, referring to Figures 14-16, the trip switch 32 also includes a tripping device 326. Specifically, when a reverse connection fault or overcurrent fault occurs in the photovoltaic string, the controller 34 sends a tripping signal to the tripping device 326, causing the tripping device 326 to release the connection with a portion of the linkage in the drive mechanism 325, thereby driving the output shaft to rotate and separating the moving contact S14 from the first stationary contact S13 and the second stationary contact S15 in the multiple sub-switches. At this time, the controller 34 is housed as an independent component inside the combiner device 3, 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 the combiner device 3 shown in Figure 6, when a fault occurs in the photovoltaic string, the controller 34 can not only control the trip switch 32 to open, but also further control the bus switch S5 to open. In addition, the controller 34 can also be a simple mechanical structure or an electromagnetic device. For example, when the controller 34 is an electromagnetic device, when a reverse connection fault or 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 tripping device 326 to release the connection with part of the connecting rod in the drive mechanism 325, and then drive the output shaft to rotate, realizing the separation of the moving contact S14 from the first stationary contact S13 and the second stationary contact S15 in the multiple sub-switches. It is worth mentioning that when the controller 34 is a mechanical structure or an electromagnetic device, it can be integrated inside the tripping device 326, thereby improving the integration of the tripping switch 32.

[0076] Furthermore, in practical applications, 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 greater 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 greater 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 places higher demands on the current-carrying capacity of the first sub-switch S1. To prevent the first sub-switch S1 from being damaged due to excessive current and to improve its current-carrying capacity, the first sub-switch S1 needs to be specially designed. One way to do this is to increase the volume of the arc-extinguishing chamber S17 in the first sub-switch S1.

[0077] Based on this, continuing with Figures 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 projected by the first sub-switch S1 along the first direction A can also be increased, that is, the area projected by the first sub-switch S1 along the first direction A is greater than the area projected by the second sub-switch S2 along the first direction A, thereby accommodating a larger volume arc-extinguishing chamber S17.

[0078] Furthermore, in order to ensure a stable connection of the wiring portion S12 corresponding to the first sub-switch S1, the volume of the wiring portion S12 needs to be increased. For example, the surface area of ​​the wiring portion S12 exposed in the housing S11 of the first sub-switch S1 is greater than the surface area of ​​the wiring portion S12 exposed in the housing S11 of the second sub-switch S2.

[0079] In summary, the photovoltaic system provided in this application greatly simplifies the structure of the combiner unit 3 and the photovoltaic inverter 4, reducing their cost and size. This facilitates equipment transportation and installation while ensuring high safety performance of the photovoltaic system. Furthermore, since the combiner unit 3 is exempt from the need for fuse 11 and the photovoltaic inverter 4 is exempt from the need for fuse 22, the construction cost and subsequent maintenance difficulty of the photovoltaic power station are significantly reduced.

[0080] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A photovoltaic system, characterized in that, Includes multiple combiner units and one photovoltaic inverter; among which, The combiner device includes multiple pairs of input terminals, a trip switch, one or more pairs of output terminals, and a controller. The input terminals are used to connect to the photovoltaic string, the output terminals are connected to the photovoltaic inverter, and the trip switch includes multiple sub-switches stacked together, which are connected between the multiple pairs of input terminals and the output terminals. The photovoltaic inverter includes multiple pairs of DC input terminals, multiple DC / DC conversion units, and one or more DC / AC conversion units. The DC input terminals are used to connect to the output terminals of the combiner device. One end of each DC / DC conversion unit is used to connect to at least some of the sub-switches in one or more of the combiner device in sequence through the DC input terminals and the output terminals. The other ends of the multiple DC / DC conversion units are connected in parallel to the DC / AC conversion unit. The controller is configured to, when a reverse connection or short circuit fault occurs in the photovoltaic string, control the trip switch corresponding to the faulty photovoltaic string to trip and drive the plurality of sub-switches included therein to disconnect the electrical connection between the faulty photovoltaic string and the corresponding DC / DC conversion unit, and ensure that there are at most three parallel connections of the photovoltaic string corresponding to the tripped trip switch.

2. The photovoltaic system according to claim 1, characterized in that, The photovoltaic inverter also includes multiple DC switches, which 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, and the DC switches are connected to the DC / DC conversion units one-to-one. Alternatively, multiple DC switches are connected to one DC / DC conversion unit.

3. The photovoltaic system according to claim 2, characterized in that, The photovoltaic inverter also includes a control unit, which controls the multiple DC switches to disconnect when the photovoltaic inverter experiences a short circuit or overcurrent fault.

4. The photovoltaic system according to any one of claims 1-3, characterized in that, When the combiner 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 busbar device further includes a pair of DC buses and a bus switch, wherein the DC buses are connected between the plurality of sub-switches and the output terminals, the pair of DC buses includes a first bus and a second bus, and the bus switch is connected to at least one of the first bus and the second bus.

6. The photovoltaic system according to claim 4, characterized in that, Each pair of input terminals is used to connect one of the photovoltaic strings. Each pair of input terminals includes a first input terminal and a second input terminal. 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 either positive or negative, and the second pole is the pole with the opposite polarity 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 terminal of the plurality of pairs of input terminals to 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 to the second output terminals, wherein one second sub-switch is connected to at most three second input terminals.

7. The photovoltaic system according to any one of claims 1-3, characterized in that, When the busbar includes N pairs of output terminals, where 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 through a pair of output terminals.

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

9. The photovoltaic system according to claim 7, characterized in that, Each pair of input terminals is used to connect one of the photovoltaic strings. The input terminals include a first input terminal and a second input terminal. 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 either positive or negative, and the second pole is the opposite pole to the first pole. The output terminals include 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 sub-switches are used to connect the first input terminal of a portion of the multiple pairs of input terminals to a first output terminal; Each group of M second sub-switches is used to connect the second input terminals of some of the multiple pairs of input terminals to a second output terminal, wherein a 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 terminal, and a control unit. The AC switch is connected between the DC / AC conversion unit and the AC output terminal. The AC output terminal is used to connect to the power grid. When the power grid fails, 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. The energy storage input terminal is used to connect to the energy storage unit. One end of the bidirectional DC / DC conversion unit is used to connect to 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 to the DC / AC conversion unit.

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

15. The photovoltaic system according to claim 13, characterized in that, Each of the plurality of sub-switches 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 housed within the housing. The wiring portion is exposed and fixed to the housing. The first stationary contact and the second stationary contact are opposite each other and are both disposed on the rotation path of the moving contact. The wiring portion is electrically connected to the first stationary contact. 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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