Photovoltaic inverter and photovoltaic power generation system

Abstract

Provided in the embodiments of the present invention are a photovoltaic inverter and a photovoltaic power generation system. The photovoltaic inverter comprises an input port, an output port, a main power circuit, an input-end lightning protection circuit and an output-end lightning protection circuit, wherein the main power circuit is electrically connected between the input port and the output port, and the main power circuit and the output port are further electrically connected to a neutral wire; the input-end lightning protection circuit is electrically connected between the input port and a grounding end, and the output-end lightning protection circuit is electrically connected between the output port and the grounding end; the input-end lightning protection circuit is used for discharging a lightning strike current at the input port, and the output-end lightning protection circuit is used for discharging a lightning strike current at the output port; and a lightning-protection balancing circuit is electrically connected between the neutral wire and the grounding end, and is used for balancing a protection residual voltage at the input port and a protection residual voltage at the output port during a lightning strike. By means of the embodiments of the present invention, a power device in a main power circuit is prevented from being damaged.

Description

Photovoltaic inverter and photovoltaic power generation system Technical Field

[0001] The embodiments of the present invention relate to the field of electronic power technology, and in particular to a photovoltaic inverter and a photovoltaic power generation system. Background Art

[0002] Most photovoltaic inverter products are installed in places such as mountains, fields, factories or home roofs. Due to the open location and the height difference between the photovoltaic panels and the photovoltaic inverter, the photovoltaic inverter is greatly affected by the impact of lightning current. Therefore, the photovoltaic inverter, the core component of the photovoltaic power generation system, needs to have a comprehensive lightning protection design inside to ensure that the photovoltaic power generation system equipment is not easily damaged when a lightning strike occurs.

[0003] To verify a photovoltaic inverter's ability to withstand lightning strikes, lightning surge current testing is performed during the development phase to assess the device's ability to withstand grid-connected lightning strikes. When a lightning strike occurs in the surrounding environment, the photovoltaic inverter in grid-connected applications will be coupled to strong transient voltages and currents. The cabling of the photovoltaic power generation system (solar panel cables and AC mains grid-connected cables) has a large routing loop area, which can result in strong interference coupling and high levels of damage, easily causing product damage. Photovoltaic inverters are typically designed with lightning protection circuits to protect the device from damage caused by natural phenomena such as lightning strikes during normal operation.

[0004] In the existing technology, photovoltaic inverters have an off-grid power supply mode. In this off-grid power supply mode, due to the asymmetric protection residual voltage of the input port and output port of the photovoltaic inverter during lightning strikes, the lightning current will be discharged through the opposite end due to the large difference in the protection residual voltage of the input port and the output port. At this time, the lightning current flowing through the main power circuit is too large, thereby causing damage to the power devices of the main power circuit.

[0005] Summary of the Invention

[0006] In view of this, embodiments of the present invention provide a photovoltaic inverter and a photovoltaic power generation system for preventing power devices in a main power circuit from being damaged during a lightning strike.

[0007] A first aspect provides a photovoltaic inverter, comprising: an input port, an output port, a main power circuit, an input-end lightning protection circuit, and an output-end lightning protection circuit, wherein the main power circuit is electrically connected between the input port and the output port, the main power circuit and the output port are electrically connected to a neutral line, the input-end lightning protection circuit is electrically connected between the input port and a ground terminal, and the output-end lightning protection circuit is electrically connected between the output port and the ground terminal;

[0008] The input-end lightning protection circuit is used to discharge the lightning current of the input port, and the output-end lightning protection circuit is used to discharge the lightning current of the output port;

[0009] A lightning protection balancing circuit is electrically connected between the neutral line and the ground terminal, and the lightning protection balancing circuit is used to balance the protection residual voltage of the input port and the protection residual voltage of the output port during a lightning strike.

[0010] In an embodiment of the present invention, during a lightning strike, the lightning protection balancing circuit can balance the protective residual voltage of the input port and the protective residual voltage of the output port, so that the difference in the protective residual voltage of the input port and the output port during a lightning strike is small, so that the lightning current of the input port can be discharged through the input end lightning protection circuit, avoiding the large lightning current of the input port from being discharged through the opposite end. At this time, the lightning current flowing through the power devices inside the main power circuit is small, thereby avoiding damage to the power devices of the main power circuit.

[0011] In a possible implementation, the lightning protection balancing circuit includes at least one first inductor.

[0012] In one possible implementation, the first inductor includes an air-core inductor or a magnetic rod inductor. Both the air-core inductor and the magnetic rod inductor are not easily saturated. Using an inductor that is not easily saturated can ensure that a voltage is generated across the first inductor, thereby increasing the residual voltage protection of the lightning discharge path of the output port.

[0013] In a possible implementation, the photovoltaic inverter further includes a first switch;

[0014] The first switch is electrically connected between the neutral line and the lightning protection balancing circuit; or,

[0015] The first switch is electrically connected between the lightning protection balancing circuit and the ground terminal.

[0016] In a possible implementation, the main power circuit includes at least one group of bus capacitors electrically connected between the positive bus and the negative bus, and the midpoint of each group of bus capacitors is electrically connected to the neutral line.

[0017] In a possible implementation, the main power circuit further includes a boost circuit and an inverter circuit, the boost circuit is electrically connected between the input port and the bus capacitor, and the inverter circuit is electrically connected between the bus capacitor and the output port;

[0018] The boost circuit is used to convert the DC voltage input from the input port into an operating voltage;

[0019] The inverter circuit is used to convert the operating voltage into an AC voltage and output the AC voltage to an output port.

[0020] In a possible implementation, the input port includes a negative input terminal and at least one positive input terminal.

[0021] In a possible implementation, the output port includes a three-phase output port and a port N, and the port N is electrically connected to the neutral line.

[0022] In a possible implementation, the output port includes a two-phase output port and a port O, and the port O is electrically connected to the neutral line.

[0023] A second aspect provides a photovoltaic power generation system, characterized by comprising: a photovoltaic panel and the photovoltaic inverter according to the first aspect or any possible implementation of the first aspect, wherein the photovoltaic panel is electrically connected to the input port;

[0024] The photovoltaic panel is used to convert light energy into a DC voltage and output it to the input port;

[0025] The photovoltaic inverter is used to convert the DC voltage into an AC voltage and output the AC voltage through the output port.

[0026] In the technical solution provided by the embodiment of the present invention, the input-end lightning protection circuit is electrically connected between the input port and the ground terminal, the output-end lightning protection circuit is electrically connected between the output port and the ground terminal, and the neutral line and the ground terminal are electrically connected to the lightning protection balancing circuit. During a lightning strike, the lightning protection balancing circuit can balance the protective residual voltage of the input port and the protective residual voltage of the output port, so that the difference in protective residual voltage between the input port and the output port during a lightning strike is small, so that the lightning current of the input port can be discharged through the input-end lightning protection circuit, avoiding the large lightning current of the input port from being discharged through the opposite end. At this time, the lightning current flowing through the power devices inside the main power circuit is small, thereby avoiding damage to the power devices of the main power circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] FIG1A is a schematic structural diagram of a photovoltaic inverter without off-grid power supply function in the related art;

[0029] FIG1B is a schematic structural diagram of another photovoltaic inverter without off-grid power supply function in the related art;

[0030] FIG2A is a schematic structural diagram of a photovoltaic inverter with off-grid power supply function in the related art;

[0031] FIG2B is a schematic structural diagram of another photovoltaic inverter with off-grid power supply function in the related art;

[0032] FIG3 is a schematic structural diagram of a photovoltaic inverter in some embodiments;

[0033] FIG4A is a schematic structural diagram of a photovoltaic inverter in some other embodiments;

[0034] FIG4B is a schematic diagram of the structure of a photovoltaic inverter in other embodiments

[0035] FIG5A is a schematic structural diagram of a photovoltaic inverter in some other embodiments;

[0036] FIG5B is a schematic structural diagram of a photovoltaic inverter in other embodiments;

[0037] FIG6 is a schematic structural diagram of a photovoltaic power generation system in some embodiments. DETAILED DESCRIPTION

[0038] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0039] It should be understood that the embodiments described are only a portion of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0040] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms "a", "an", "the" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0041] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. Furthermore, the character " / " in this document generally indicates an "or" relationship between the associated objects.

[0042] FIG1A is a schematic diagram of the structure of a photovoltaic inverter without off-grid power supply function in the related art. As shown in FIG1A , the photovoltaic inverter includes an input port 10, an output port 20, a main power circuit, an input-end lightning protection circuit 60, and an output-end lightning protection circuit 70. The main power circuit is electrically connected between the input port 10 and the output port 20. The main power circuit and the output port 20 are electrically connected to the neutral line 40. The input-end lightning protection circuit 60 is electrically connected between the input port 10 and the ground terminal PE. The output-end lightning protection circuit 70 is electrically connected between the output port 20 and the ground terminal PE.

[0043] The main power circuit includes two bus capacitors electrically connected between the positive bus BUS+ and the negative bus BUS-. The midpoint N1 of each bus capacitor is electrically connected to the neutral line 40. One bus capacitor includes a first capacitor C1 and a second capacitor C2 connected in series between the positive bus BUS+ and the negative bus BUS-. The other bus capacitor includes a first capacitor C3 and a second capacitor C4 connected in series between the positive bus BUS+ and the negative bus BUS-. The main power circuit also includes a boost circuit 301, an inverter circuit 302, and a first filter circuit 303.

[0044] As shown in Figure 1A, the specific description of the input port 10, the output port 20, the input-end lightning protection circuit 60, the output-end lightning protection circuit 70, the boost circuit 301, the inverter circuit 302 and the first filter circuit 303 can be found in the description of the embodiment shown in Figure 4A below, and will not be repeated here.

[0045] As shown in Figure 1A, input port 10 is a high-voltage direct current (HDVC) port, and output port 20 is an AC output port. The input-side lightning protection circuit 60 can employ a 510 varistor in series with a 385 varistor. This allows the input port 10 to achieve lightning protection through a 510 varistor in series with a 385 varistor. The output-side lightning protection circuit 70 can employ a 385 varistor in series with a 510 varistor. This allows the output port 20 to achieve lightning protection through a 385 varistor in series with a 510 varistor. During a lightning strike, when the overvoltage amplitude coupled to the input port 10 or the output port 20 reaches the action voltage of the varistor, the internal resistance of the varistor is instantly reduced to a short-circuit state through its piezoelectric characteristics. At this time, the protective residual voltage of the input port 10 is equivalent to the protective residual voltage of the output port 20, that is, the difference in the protective residual voltages of the input port 10 and the output port 20 is small, and the lightning current is discharged nearby, that is: the lightning current of the input port 10 is discharged through the input-end lightning protection circuit 60, and the lightning current of the output port 20 is discharged through the output-end lightning protection circuit 70. At this time, the lightning current flowing through the power devices inside the main power circuit is small and lower than the lightning overcurrent capability of the power devices, so that the power devices of the main power circuit will not be damaged.

[0046] FIG1B is a schematic diagram of the structure of another photovoltaic inverter without off-grid power supply function in the related art. As shown in FIG1B , the photovoltaic inverter includes an input port 10, an output port 20, a main power circuit, an input-end lightning protection circuit 60, and an output-end lightning protection circuit 70. The main power circuit is electrically connected between the input port 10 and the output port 20, and the main power circuit and the output port 20 are electrically connected to the neutral line 40. The input-end lightning protection circuit 60 is electrically connected between the input port 10 and the ground terminal PE, and the output-end lightning protection circuit 70 is electrically connected between the output port 20 and the ground terminal PE.

[0047] The main power circuit includes a bus capacitor electrically connected between the positive bus BUS+ and the negative bus BUS-. The midpoint O1 of the bus capacitor is electrically connected to the neutral line 40. The bus capacitor may include a first capacitor C1 and a second capacitor C2 connected in series between the positive bus BUS+ and the negative bus BUS-. The main power circuit also includes a second filter circuit 304, a boost circuit 301, an inverter circuit 302, and a third filter circuit 305.

[0048] As shown in Figure 1B, the specific description of the input port 10, the output port 20, the input-end lightning protection circuit 60, the output-end lightning protection circuit 70, the second filtering circuit 304, the boost circuit 301, the inverter circuit 302 and the third filtering circuit 305 can be found in the description of the embodiment shown in Figure 5A below, and will not be repeated here.

[0049] As shown in FIG1B , input port 10 is an HDVC port, and output port 20 is an AC output port. Input-side lightning protection circuit 60 can employ a varistor solution, thereby enabling input port 10 to achieve lightning protection through the varistor solution; output-side lightning protection circuit 70 can employ a varistor solution, thereby enabling output port 20 to achieve lightning protection through the varistor solution. During a lightning strike, when the overvoltage amplitude coupled to the input port 10 or the output port 20 reaches the action voltage of the varistor, the internal resistance of the varistor is instantly reduced to a short-circuit state through its piezoelectric characteristics. At this time, the protective residual voltage of the input port 10 is equivalent to the protective residual voltage of the output port 20, that is, the difference in the protective residual voltages of the input port 10 and the output port 20 is small, and the lightning current is discharged nearby, that is: the lightning current of the input port 10 is discharged through the input-end lightning protection circuit 60, and the lightning current of the output port 20 is discharged through the output-end lightning protection circuit 70. At this time, the lightning current flowing through the power devices inside the main power circuit is small and lower than the lightning overcurrent capability of the power devices, so that the power devices of the main power circuit will not be damaged.

[0050] To sum up, for a photovoltaic inverter without an off-grid power supply function, under the action of the input-end lightning protection circuit 60 and the output-end lightning protection circuit 70, the protection residual voltages of the input port 10 and the output port 20 during a lightning strike are symmetrical, that is, the difference in protection residual voltages between the input port 10 and the output port 20 is small. Therefore, during a lightning strike, the lightning current will not be discharged through the opposite end due to the large difference in protection residual voltage, so that the lightning current flowing through the main power circuit is small, thereby preventing damage to the power devices of the main power circuit.

[0051] To enable the photovoltaic inverter in Figures 1A and 1B to provide off-grid power supply functionality, the photovoltaic inverter in Figures 1A and 1B can be upgraded to include a neutral wire 40 electrically connected to the ground terminal PE, as shown in Figures 2A and 2B.

[0052] FIG2A is a schematic structural diagram of a photovoltaic inverter with an off-grid power supply function in the related art. As shown in FIG2A , based on the embodiment shown in FIG1A , the neutral line 40 is electrically connected to the ground terminal PE.

[0053] FIG2B is a schematic structural diagram of another photovoltaic inverter with off-grid power supply function in the related art. As shown in FIG2B , based on the embodiment shown in FIG1B , the neutral line 40 is electrically connected to the ground terminal PE.

[0054] Furthermore, as shown in Figures 2A and 2B, a first switch K1 can be provided between the neutral line 40 and the ground terminal PE. When the PV inverter is in grid-connected power supply mode, the first switch K1 is open, disconnecting the neutral line 40 from the ground terminal PE. When the PV inverter is in off-grid power supply mode, the first switch K1 is closed, connecting the neutral line 40 to the ground terminal PE.

[0055] Photovoltaic inverters with off-grid functionality generate new technical problems during lightning strikes: the photovoltaic inverter is in off-grid power supply mode (the first switch K1 is closed). When the input port 10 is coupled to the lightning current, since the neutral line 40 is electrically connected to the ground terminal PE, the protection residual voltage and impedance of the lightning discharge path of the output port 20 are low, and the lightning current of the input port 10 will be discharged through the discharge path of the output port 20. For example, as shown in FIG2A , the common-mode current of a lightning strike at input port 10 is 10 kA. Since the neutral line 40 is electrically connected to the ground terminal PE (K1 is closed at this time) to form a low-impedance path, the lightning current can be discharged through the discharge path (diode → bus capacitor → point N2 → ground terminal PE). This lightning current discharge path causes a large lightning current to flow through the main power circuit, thereby causing overcurrent damage to the power devices in the main power circuit. As shown in FIG2B , the common-mode current of a lightning strike at input port 10 is 10 kA. Since the neutral line 40 is electrically connected to the ground terminal PE (K1 is closed at this time) to form a low-impedance path, the lightning current can be discharged through the discharge path (diode → bus capacitor → point O2 → ground terminal PE). This lightning current discharge path causes a large lightning current to flow through the main power circuit, thereby causing overcurrent damage to the power devices in the main power circuit. In actual product applications, the lightning current discharge paths shown in FIG2A and FIG2B may also be other paths, and the above discharge paths are only examples.

[0056] To address the technical problems existing in the above-mentioned related technologies, embodiments of the present invention provide a photovoltaic inverter and a photovoltaic power generation system. In the photovoltaic inverter, an input-end lightning protection circuit is electrically connected between the input port and the ground terminal, an output-end lightning protection circuit is electrically connected between the output port and the ground terminal, and a lightning protection balancing circuit is electrically connected between the neutral line and the ground terminal. During a lightning strike, the lightning protection balancing circuit can balance the protective residual voltage of the input port and the protective residual voltage of the output port, so that the difference in protective residual voltage between the input port and the output port during a lightning strike is small, thereby allowing the lightning current of the input port to be discharged through the input-end lightning protection circuit, avoiding the large lightning current of the input port from being discharged through the opposite end. At this time, the lightning current flowing through the power devices in the main power circuit is small, thereby avoiding damage to the power devices in the main power circuit.

[0057] Figure 3 is a structural schematic diagram of a photovoltaic inverter in some embodiments. As shown in Figure 3, the photovoltaic inverter may include an input port 10, an output port 20 and a main power circuit 30. The main power circuit 30 is electrically connected between the input port 10 and the output port 20. The main power circuit 30 and the output port 20 are electrically connected to a neutral line 40. A lightning protection balancing circuit 50 is electrically connected between the neutral line 40 and the ground terminal PE.

[0058] The input port 10 can receive the DC voltage output by the photovoltaic panel and output the DC voltage to the main power circuit 30. The main power circuit 30 can convert the DC voltage into an AC voltage and output the AC voltage to the output port 20. The output port 20 can output the AC voltage.

[0059] To provide lightning protection for the photovoltaic inverter, the inverter may also include an input lightning protection circuit 60 and an output lightning protection circuit 70. The input lightning protection circuit 60 is electrically connected between the input port 10 and the ground terminal PE, while the output lightning protection circuit 70 is electrically connected between the output port 20 and the ground terminal PE. During a lightning strike, the input lightning protection circuit 60 can be used to discharge the lightning current from the input port 10, while the output lightning protection circuit 70 can be used to discharge the lightning current from the output port 20, thereby achieving the nearest discharge of the lightning current.

[0060] The lightning protection balancing circuit 50 is used to balance the protection residual voltage of the input port 10 and the protection residual voltage of the output port 20 during a lightning strike.

[0061] In the embodiment of the present invention, the lightning strike process may be a lightning strike process during a simulated lightning strike experiment.

[0062] In some embodiments, the photovoltaic inverter is a hybrid inverter, and the photovoltaic inverter has a grid-connected power supply mode and an off-grid power supply mode, and the photovoltaic inverter can switch between the grid-connected power supply mode and the off-grid power supply mode. The photovoltaic inverter also includes a first switch K1. As an optional solution, as shown in Figure 3, the first switch K1 is electrically connected between the neutral line 40 and the lightning protection balancing circuit 50. Specifically, the first end of the first switch K1 is electrically connected to the neutral line 40, the second end of the first switch K1 is electrically connected to the first end of the lightning protection balancing circuit 50, and the second end of the lightning protection balancing circuit 50 is electrically connected to the ground terminal PE. As another optional solution, the first switch K1 is electrically connected between the lightning protection balancing circuit 50 and the ground terminal PE. Specifically, the first end of the lightning protection balancing circuit 50 is electrically connected to the neutral line 40, the second end of the lightning protection balancing circuit 50 is electrically connected to the first end of the first switch K1, and the second end of the first switch K1 is electrically connected to the ground terminal PE. This situation is not specifically drawn in the figure. As shown in Figure 3, if the photovoltaic inverter is in the grid-connected power supply mode, the first switch K1 is disconnected. At this time, the neutral line 40 and the lightning protection balancing circuit 50 are disconnected, and the neutral line 40 cannot be electrically connected to the ground terminal PE through the lightning protection balancing circuit 50; if the photovoltaic inverter is in the off-grid power supply mode, the first switch K1 is closed. At this time, the neutral line 40 and the lightning protection balancing circuit 50 are connected, and the neutral line 40 can be electrically connected to the ground terminal PE through the lightning protection balancing circuit 50, that is, the lightning protection balancing circuit 50 is electrically connected between the neutral line 40 and the ground terminal PE.

[0063] In some embodiments, the lightning protection balancing circuit 50 may include at least one first inductor. During a lightning strike, when the photovoltaic inverter is in off-grid power supply mode, the lightning protection balancing circuit 50 can balance the protection residual voltage of the input port 10 and the protection residual voltage of the output port 20, so that the difference in the protection residual voltage of the input port and the output port during a lightning strike is small. The input-end lightning protection circuit 60 can discharge the lightning current of the input port 10, thereby preventing the large lightning current of the input port 10 from being discharged through the opposite end.

[0064] In the technical solution of the photovoltaic inverter provided by the embodiment of the present invention, the input-end lightning protection circuit is electrically connected between the input port and the ground terminal, the output-end lightning protection circuit is electrically connected between the output port and the ground terminal, and the neutral line and the ground terminal are electrically connected to the lightning protection balancing circuit. During a lightning strike, the lightning protection balancing circuit can balance the protective residual voltage of the input port and the protective residual voltage of the output port, so that the difference in protective residual voltage between the input port and the output port during a lightning strike is small, so that the lightning current of the input port can be discharged through the input-end lightning protection circuit, avoiding the large lightning current of the input port from being discharged through the opposite end. At this time, the lightning current flowing through the power devices inside the main power circuit is small, thereby avoiding damage to the power devices of the main power circuit.

[0065] In an embodiment of the present invention, the photovoltaic inverter shown in FIG3 may include a three-phase photovoltaic inverter or a two-phase photovoltaic inverter. The three-phase photovoltaic inverter is described in detail below with reference to FIG4A and FIG4B , and the two-phase photovoltaic inverter is described in detail with reference to FIG5A and FIG5B .

[0066] FIG4A is a schematic diagram of the structure of a photovoltaic inverter in another embodiment. As shown in FIG4A , the photovoltaic inverter is a three-phase photovoltaic inverter. The photovoltaic inverter includes an input port 10, an output port 20, a main power circuit, a lightning protection balancing circuit 50, an input-end lightning protection circuit 60, and an output-end lightning protection circuit 70. The main power circuit is electrically connected between the input port 10 and the output port 20, the main power circuit and the output port 20 are electrically connected to the neutral line 40, the lightning protection balancing circuit 50 is electrically connected between the neutral line 40 and the ground terminal PE, the input-end lightning protection circuit 60 is electrically connected between the input port 10 and the ground terminal PE, and the output-end lightning protection circuit 70 is electrically connected between the output port 20 and the ground terminal PE.

[0067] The input port 10 can be electrically connected to a photovoltaic panel, which can convert light energy into a DC voltage and output the DC voltage to the input port 10. The input port 10 may include a negative input terminal PV- and at least one positive input terminal PV+. As an alternative, the input port 10 may include one positive input terminal PV+ and one negative input terminal PV-. As another alternative, the input port 10 may include multiple positive input terminals PV+ and one negative input terminal PV-. For example, as shown in FIG4A , the input port 10 includes two positive input terminals PV+ and one negative input terminal PV-.

[0068] As shown in FIG. 4A , the output port 20 may include a three-phase output port and a port N. The three-phase output port may include a port A, a port B, and a port C. The port N is electrically connected to the neutral line 40 .

[0069] The main power circuit includes at least one set of bus capacitors electrically connected between the positive bus BUS+ and the negative bus BUS-, with the midpoint N1 of each set of bus capacitors electrically connected to the neutral line 40. As an alternative, each set of bus capacitors may include a first capacitor and a second capacitor, with the connection point between the first capacitor and the second capacitor being the midpoint N1 of the bus capacitors. Since the midpoints of the two sets of bus capacitors are connected to each other, the midpoints of both sets of bus capacitors can be referred to as midpoint N1. For example, as shown in FIG4A , the main power circuit includes two sets of bus capacitors connected in parallel, wherein one set of bus capacitors may include a first capacitor C1 and a second capacitor C2 connected in series between the positive bus BUS+ and the negative bus BUS-, and the other set of bus capacitors may include a first capacitor C3 and a second capacitor C4 connected in series between the positive bus BUS+ and the negative bus BUS-, with the connection point between the first capacitor C1 and the second capacitor C2 being the midpoint N1, and the connection point between the first capacitor C3 and the second capacitor C4 also being the midpoint N1. A first end of the first capacitor C1 is electrically connected to the positive bus BUS+, a second end of the first capacitor C1 is electrically connected to the midpoint N, a first end of the second capacitor C2 is electrically connected to the midpoint N1, and a second end of the second capacitor C2 is electrically connected to the negative bus BUS-; a first end of the first capacitor C3 is electrically connected to the positive bus BUS+, a second end of the first capacitor C3 is electrically connected to the midpoint N1, a first end of the second capacitor C4 is electrically connected to the midpoint N1, and a second end of the second capacitor C4 is electrically connected to the negative bus BUS-. Midpoint N1 is electrically connected to the neutral line 40.

[0070] In this embodiment of the present invention, the main power circuit further includes a boost circuit 301 and an inverter circuit 302. The boost circuit 301 is electrically connected between the input port 10 and the bus capacitor, and the inverter circuit 302 is electrically connected between the bus capacitor and the output port 20. The boost circuit 301 is used to convert the DC voltage input from the input port 10 into an operating voltage; the inverter circuit 302 is used to convert the operating voltage into an AC voltage and output the AC voltage to the output port 20.

[0071] In some embodiments, the boost circuit 301 includes a boost sub-circuit corresponding to each positive input terminal PV+. For example, as shown in FIG4A , since the input port 10 includes two positive input terminals PV+, the boost circuit 301 includes two boost sub-circuits. As shown in FIG4A , the boost sub-circuit may include a second inductor L2, a first diode D1, and a first switch Q1. A first end of the second inductor L2 is electrically connected to the positive input terminal PV+, a second end of the second inductor L2 is electrically connected to the anode of the first diode D1, and a cathode of the first diode D1 is electrically connected to the bus BUS+. A control end of the first switch Q1 is electrically connected to a control circuit (not shown in the figure), a first end of the first switch Q1 is electrically connected to the second end of the second inductor L2 and the anode of the first diode Q1, and a second end of the first switch Q1 is electrically connected to the negative bus BUS-.

[0072] In some embodiments, the inverter circuit 302 may include multiple inverter sub-circuits, each of which corresponds to one of the output ports. For example, as shown in FIG4A , the inverter circuit 302 includes three inverter sub-circuits, corresponding to port A, port B, and port C, respectively. The inverter sub-circuit corresponding to port A is described as an example. The inverter sub-circuit includes a second switch transistor Q21, a third switch transistor Q22, a fourth switch transistor Q23, and a fifth switch transistor Q24. The second switch transistor Q21 and the third switch transistor Q22 are connected in series between the positive bus BUS+ and the negative bus BUS-. The fourth switch transistor Q23 and the fifth switch transistor Q24 are connected in series between the midpoint N1 of the bus capacitor and the connection point B between the second switch transistor Q21 and the third switch transistor Q22. Specifically, the control terminal of the second switch Q21 is electrically connected to the control circuit, the first terminal of the second switch Q21 is electrically connected to the positive bus BUS+, the second terminal of the second switch Q21 is electrically connected to the first terminal of the third switch Q22, the control terminal of the third switch Q21 is electrically connected to the control circuit, and the second terminal of the third switch Q22 is electrically connected to the negative bus BUS-. The control terminal of the fourth switch Q23 is electrically connected to the control circuit, the first terminal of the fourth switch Q23 is electrically connected to the midpoint N1 of the bus capacitor, the second terminal of the fourth switch Q23 is electrically connected to the first terminal of the fifth switch Q24, the control terminal of the fifth switch Q24 is electrically connected to the control circuit, and the second terminal of the fifth switch Q24 is electrically connected to the connection point B. The inverter sub-circuit also includes a third inductor L3 and a third capacitor C5. The third inductor L3 is electrically connected to the connection point B and is electrically connected to the neutral line 40 via the third capacitor C5. Specifically, a first end of the third inductor L3 is electrically connected to connection point B, a second end of the third inductor L3 is electrically connected to a first end of a third capacitor C5, and a second end of the third capacitor C5 is electrically connected to the neutral line 40. The third inductor L3 is a filter inductor, and the third capacitor C5 is a filter capacitor. Furthermore, the second end of the third inductor L3 and the first end of the third capacitor C5 can also be electrically connected to port A of the output port 20, although this is not specifically shown.

[0073] In the embodiment of the present invention, for example, the first to fifth switching transistors Q1 to Q24 may each include an insulated gate bipolar transistor (IGBT) or a metal-oxide-semiconductor field-effect transistor (MOSFET). Furthermore, a control circuit may be used to control the on / off states of the first to fifth switching transistors Q1 to Q24.

[0074] In some embodiments, the main power circuit may further include a first filter circuit 303, electrically connected between the inverter circuit 302 and the output port 20. The first filter circuit 303 is configured to filter the AC voltage output by the inverter circuit 302 and output the filtered AC voltage to the output port 20. The first filter circuit 303 includes a plurality of fourth inductors L4. For example, as shown in FIG4A , the first filter circuit 303 includes four fourth inductors L4. The four fourth inductors L4 may include, from top to bottom in FIG4A , a first fourth inductor L4, a second fourth inductor L4, a third fourth inductor L4, a fourth fourth inductor L4, and a fifth fourth inductor L4. Among them, the first end of the first fourth inductor L4 is electrically connected to the corresponding third inductor L3, and the second end of the first fourth inductor L4 is electrically connected to port A; the first end of the second fourth inductor L4 is electrically connected to the corresponding third inductor L3, and the second end of the second fourth inductor L4 is electrically connected to port B; the first end of the third fourth inductor L4 is electrically connected to the corresponding third inductor L3, and the second end of the third fourth inductor L4 is electrically connected to port C; the fourth fourth inductor L4 is arranged on the neutral line 40, so that the first end of the fourth fourth inductor L4 can be electrically connected to the midpoint N1 of the bus capacitor through the neutral line 40 and the second end is electrically connected to port N through the neutral line 40.

[0075] In some embodiments, the input lightning protection circuit 60 may include a pressure-sensitive component, which may include multiple varistors. At least one varistor is electrically connected between each positive input terminal PV+ and the ground terminal PE, and at least one varistor is electrically connected between the negative input terminal PV- and the ground terminal PE. As shown in FIG4A , two varistors are connected in series between each positive input terminal PV+ and the ground terminal PE, and the connection points between the two series-connected varistors are all connected. For example, the two series-connected varistors may include a 510 varistor and a 385 varistor. The 510 varistor and the 385 varistor are connected in series between the first positive input terminal PV+ and the ground terminal PE, the 510 varistor and the 385 varistor are connected in series between the second positive input terminal PV+ and the ground terminal PE, and the 510 varistor and the 385 varistor are connected in series between the negative input terminal PV- and the ground terminal PE, and the connection points between the three series-connected 510 varistor and the 385 varistor are all connected.

[0076] In some embodiments, the output lightning protection circuit 70 may include a pressure-sensitive component, which may include multiple varistors. At least one varistor is electrically connected between each of the output ports 20 and the ground terminal PE, and at least one varistor is electrically connected between each of the ports A, B, and C and the port N. As shown in FIG4A , for example, a 385 varistor is electrically connected between port A and port N, a 385 varistor is electrically connected between port B and port N, and a 385 varistor is electrically connected between port C and port N. In addition, one end of four 385 varistors is electrically connected to port A, port B, port C, and port N, respectively, and the other ends of the four 385 varistors are electrically connected to one end of a 510 varistor, the other end of which is electrically connected to the ground terminal PE.

[0077] As shown in FIG. 4A , in actual applications, according to product design requirements, varistors may use varistors with different operating voltages, which is not limited in the embodiment of the present invention.

[0078] In some embodiments, the lightning protection balancing circuit 50 includes at least one first inductor L1. As shown in FIG4A , as an optional solution, the lightning protection balancing circuit 50 includes a first inductor L1, a first end of the first inductor L1 being electrically connected to the neutral line 40, and a second end of the first inductor L1 being electrically connected to the ground terminal PE. As another optional solution, the lightning protection balancing circuit 50 may include multiple first inductors L1, and the multiple first inductors L1 may be electrically connected in parallel and / or in series, although this is not specifically shown in the figure.

[0079] In some embodiments, the first inductor L1 may be an inductor that is not easily saturated. As an optional solution, the first inductor L1 may include an air-core inductor or a magnetic rod inductor. Both the air-core inductor and the magnetic rod inductor are inductors that are not easily saturated. The use of an inductor that is not easily saturated can ensure that a voltage is generated on the first inductor L1, thereby improving the protective residual voltage of the lightning discharge path of the output port 20. As shown in Figure 4A, for example, the first inductor L1 is an air-core inductor. The inductance value of the first inductor L1 can be set according to product design requirements. For example, the inductance value of the first inductor L1 can be 25uH, which is not limited in this embodiment of the present invention.

[0080] In some embodiments, as shown in FIG4A , the photovoltaic inverter may further include a first switch K1 electrically connected between the neutral line 40 and the first inductor L1. A first end of the first switch K1 is electrically connected to the neutral line 40, a second end of the first switch K1 is electrically connected to the first end of the first inductor L1, and the second end of the first inductor L1 is electrically connected to the ground terminal PE. In actual applications, the first switch K1 may also be electrically connected between the first inductor L1 and the ground terminal PE, where the first end of the first inductor L1 is electrically connected to the neutral line 40, the second end of the first inductor L1 is electrically connected to the first end of the first switch K1, and the second end of the first switch L1 is electrically connected to the ground terminal PE. This embodiment is not specifically shown. When the photovoltaic inverter is in off-grid power supply mode, the first switch K1 is closed, and conduction is established between the neutral line 40 and the first inductor L1. The neutral line 40 may be electrically connected to the ground terminal PE via the first inductor L1, i.e., the first inductor L1 is electrically connected between the neutral line 40 and the ground terminal PE. When the photovoltaic inverter is in the grid-connected power supply mode, the first switch K1 is disconnected. At this time, the neutral line 40 and the first inductor L1 are disconnected, and the neutral line 40 cannot be electrically connected to the ground terminal PE through the first inductor L1.

[0081] As shown in FIG4A , the midpoint N1 of the busbar capacitor is electrically connected to the ground terminal PE via the first inductor L1. During a lightning strike, the input port 10 is coupled to the lightning voltage, i.e., the input port 10 is instantaneously induced by the lightning voltage. Consequently, the voltage at the input port 10 increases, reaching the operating voltage of the varistor in the input lightning protection circuit 60. At this point, under the action of the first inductor L1, the protective residual voltage of the lightning discharge path of the output port 20 increases, minimizing the difference in protective residual voltage between the input port 10 and the output port 20. This means that the first inductor L1 can balance the protective residual voltages of the input port 10 and the output port 20. The varistor in the input lightning protection circuit 60 discharges the lightning overvoltage and overcurrent, achieving localized discharge of the lightning current, preventing large lightning currents from flowing through the main power circuit, and thereby preventing damage to the power devices in the main power circuit. The voltage of the first inductor L1 can be L*di / dt, where L is the inductance of the first inductor L1 and di / dt is the rate of change of current with respect to time.

[0082] As shown in FIG4A , the technical solution of the embodiment of the present invention can effectively solve the problem of unbalanced residual voltage protection of the input port 10 and the output port 20 during a lightning strike in the topology of the hybrid photovoltaic inverter. The common-mode protection capability of the input port 10 can reach a two-wire common-mode current of 5KA to 10kA, and the lightning protection capability of the photovoltaic inverter can meet the lightning protection specification of a two-wire common-mode current of 5KA to 10kA. As an optional solution, in the embodiment of the present invention, the lightning protection capability of the photovoltaic inverter can meet the lightning protection specification of a two-wire common-mode current of 10kA. Among them, the "two-wire" in the two-wire common-mode current refers to the positive input terminal PV+ and the negative input terminal PV-. For example, in FIG4A , the two-wire common-mode current of the first positive input terminal PV+ and the negative input terminal PV- is 10kA, and the two-wire common-mode current of the second positive input terminal PV+ and the negative input terminal PV- is 10kA.

[0083] FIG4B is a schematic structural diagram of a photovoltaic inverter in some other embodiments. As shown in FIG4B , the difference from the photovoltaic inverter shown in FIG4A is that the input-end lightning protection circuit 60 further includes a first gas discharge tube G1, and the output-end lightning protection circuit 70 further includes a second gas discharge tube G2.

[0084] The first gas discharge tube G1 is electrically connected between the pressure-sensitive component and the ground terminal PE, and the pressure-sensitive component can be electrically connected to the ground terminal PE through the first gas discharge tube G1. The first end of the first gas discharge tube G1 is electrically connected to the pressure-sensitive component (the three 385 varistors of the pressure-sensitive component shown in Figure 4B), and the second end of the first gas discharge tube G1 is electrically connected to the ground terminal PE.

[0085] The second gas discharge tube G2 is electrically connected between the pressure sensitive component and the ground terminal PE. The first end of the second gas discharge tube G2 is electrically connected to the pressure sensitive component (the 510 varistor of the pressure sensitive component shown in Figure 4B), and the second end of the second gas discharge tube G2 is electrically connected to the ground terminal PE.

[0086] For a detailed description of the pressure-sensitive component, please refer to the description of the embodiment shown in FIG4A , which will not be repeated here.

[0087] As shown in Figure 4B, the midpoint N1 of the bus capacitor is electrically connected to the ground terminal PE through the first inductor L1. During a lightning strike, the input port 10 is coupled to the lightning voltage, that is, the input port 10 instantaneously senses the lightning voltage, so the voltage of the input port 10 increases, and the voltage of the input port 10 reaches the operating voltage of the varistor and the first gas discharge tube G1 in the input-end lightning protection circuit 60. At this time, under the action of the first inductor L1, the protective residual voltage of the lightning current discharge path of the output port 20 increases, so that the difference in the protective residual voltage between the input port 10 and the output port 20 is small, that is, the first inductor L1 can balance the protective residual voltage of the input port 10 and the output port 20. The varistor and the first gas discharge tube G1 of the input-end lightning protection circuit 60 discharge the lightning overvoltage and overcurrent, thereby achieving the nearest discharge of the lightning current, avoiding a large lightning current from flowing through the main power circuit, and thus avoiding damage to the power devices in the main power circuit. The voltage of the first inductor L1 may be L*di / dt, where L is the inductance of the first inductor L1 and di / dt is the rate of change of current with respect to time.

[0088] Compared with the technical solution in Figure 4A, the input-end lightning protection circuit 60 and the output-end lightning protection circuit 70 in Figure 4B are both provided with gas discharge tubes electrically connected to the pressure-sensitive components, which improves the discharge capacity of the input-end lightning protection circuit 60 and the output-end lightning protection circuit 70 for lightning current, further avoids large lightning currents flowing through the main power circuit, and thus further avoids damage to power devices in the main power circuit.

[0089] FIG5A is a schematic diagram of the structure of a photovoltaic inverter in another embodiment. As shown in FIG5A , the photovoltaic inverter is a two-phase photovoltaic inverter. The photovoltaic inverter includes an input port 10, an output port 20, a main power circuit, a lightning protection balancing circuit 50, an input-end lightning protection circuit 60, and an output-end lightning protection circuit 70. The main power circuit is electrically connected between the input port 10 and the output port 20, the main power circuit and the output port 20 are electrically connected to the neutral line 40, the lightning protection balancing circuit 50 is electrically connected between the neutral line 40 and the ground terminal PE, the input-end lightning protection circuit 60 is electrically connected between the input port 10 and the ground terminal PE, and the output-end lightning protection circuit 70 is electrically connected between the output port 20 and the ground terminal PE.

[0090] The input port 10 can be electrically connected to a photovoltaic panel, which can convert light energy into a DC voltage and output the DC voltage to the input port 10. The input port 10 may include a negative input terminal PV- and at least one positive input terminal PV+. As an alternative, the input port 10 may include multiple positive input terminals PV+ and one negative input terminal PV-. As another alternative, the input port 10 may include one positive input terminal PV+ and one negative input terminal PV-. For example, as shown in FIG5A , the input port 10 includes one positive input terminal PV+ and one negative input terminal PV-.

[0091] As shown in FIG. 5A , the output port 20 includes a two-phase output port and a port O. The two-phase output port includes a port U and a port W. The port O is electrically connected to the neutral line 40 .

[0092] The main power circuit includes a set of bus capacitors electrically connected between the positive bus BUS+ and the negative bus BUS-, with a midpoint O1 of the set of bus capacitors electrically connected to the neutral line 40. For example, as shown in FIG5A , the set of bus capacitors may include a first capacitor C1 and a second capacitor C2 connected in series between the positive bus BUS+ and the negative bus BUS-, with the connection point between the first capacitor C1 and the second capacitor C2 being the midpoint O1. A first end of the first capacitor C1 is electrically connected to the positive bus BUS+, a second end of the first capacitor C1 is electrically connected to the midpoint O1, a first end of the second capacitor C2 is electrically connected to the midpoint O1, a second end of the second capacitor C2 is electrically connected to the negative bus BUS-, and the midpoint O1 is electrically connected to the neutral line 40.

[0093] In an embodiment of the present invention, the main power circuit further includes a boost circuit 301 and an inverter circuit 302. The boost circuit 301 is electrically connected between the input port 10 and the bus capacitor, and the inverter circuit 302 is electrically connected between the bus capacitor and the output port 20. The boost circuit 301 is configured to convert the DC voltage input from the input port 10 into an operating voltage; the inverter circuit 302 is configured to convert the operating voltage into an AC voltage and output the AC voltage to the output port 20. In some embodiments, the main power circuit further includes a second filter circuit 304, electrically connected between the input port 10 and the boost circuit 301. The second filter circuit 304 is configured to filter the DC voltage input from the input port 10 and output the filtered DC voltage to the boost circuit 301. In some embodiments, the main power circuit further includes a third filter circuit 305, electrically connected between the inverter circuit 302 and the output port 20. The third filter circuit 305 is configured to filter the AC voltage output from the inverter circuit 302 and output the filtered AC voltage to the output port 20.

[0094] In some embodiments, the second filtering circuit 304 includes a fourth capacitor C6, a fifth capacitor C7, a fifth inductor L5, and a sixth inductor L6. A first end of the fourth capacitor C6 is electrically connected to the positive input terminal PV+, and a second end of the fourth capacitor C6 is electrically connected to the negative input terminal PV-; a first end of the fifth inductor L5 is electrically connected to the positive input terminal PV+ and the first end of the fourth capacitor C6, and a second end of the fifth inductor L5 is electrically connected to the first end of the fifth capacitor C7 and the boost circuit 301; a first end of the fifth capacitor C7 is electrically connected to the boost circuit 301, and a second end of the fifth capacitor C7 is electrically connected to the second end of the sixth inductor L6 and the boost circuit 301; a first end of the sixth inductor L6 is electrically connected to the negative input terminal PV- and the second end of the fourth capacitor C6, and a second end of the sixth inductor L6 is electrically connected to the boost circuit 301.

[0095] In some embodiments, the boost circuit 301 includes a second diode D2, a seventh inductor L7, a third diode D3, and a sixth switch Q3. The anode of the second diode D2 is electrically connected to the first end of the seventh inductor L7, the second end of the fifth inductor L5, and the first end of the fifth capacitor C7 in the second filter circuit 304. The cathode of the second diode D2 is electrically connected to the cathode of the third diode D3 and the bus capacitor. The first end of the seventh inductor L7 is electrically connected to the second end of the fifth inductor L6 and the first end of the fifth capacitor C7 in the second filter circuit 304. The second end of the seventh inductor L7 is electrically connected to the anode of the third diode D3. The cathode of the third diode D3 is electrically connected to the bus capacitor. The control terminal of the sixth switch Q3 is electrically connected to the control circuit. The first end of the sixth switch Q3 is electrically connected to the second end of the seventh inductor L7 and the anode of the third diode D3. The second end of the sixth switch Q3 is electrically connected to the bus capacitor.

[0096] In some embodiments, the inverter circuit 302 may include a seventh switching transistor Q41, an eighth switching transistor Q42, a ninth switching transistor Q43, a tenth switching transistor Q44, an eleventh switching transistor Q45, a twelfth switching transistor Q46, an eighth inductor L8, a ninth inductor L9, a sixth capacitor C8, a seventh capacitor C9, and an eighth capacitor C10. The seventh switching transistor Q41 and the eighth switching transistor Q42 are connected in series between the positive bus BUS+ and the negative bus BUS-, and the ninth switching transistor Q43 and the tenth switching transistor Q44 are connected in series between the positive bus BUS+ and the negative bus BUS-. Among them, the control end of the seventh switch tube Q41 is electrically connected to the control circuit, the first end of the seventh switch tube Q41 is electrically connected to the positive bus BUS+, and the second end of the seventh switch tube Q41 is electrically connected to the connection point C; the control end of the eighth switch tube Q42 is electrically connected to the control circuit, the first end of the eighth switch tube Q42 is electrically connected to the connection point C, and the second end of the eighth switch tube Q42 is electrically connected to the negative bus BUS-; the control end of the ninth switch tube Q43 is electrically connected to the control circuit, the first end of the ninth switch tube Q43 is electrically connected to the positive bus BUS+, and the second end of the ninth switch tube Q43 is electrically connected to the connection point D; the control end of the tenth switch tube Q44 is electrically connected to the control circuit, the first end of the tenth switch tube Q44 is electrically connected to the connection point D, and the second end of the tenth switch tube Q44 is electrically connected to the negative bus BUS-. The eleventh switch transistor Q45 and the twelfth switch transistor Q46 are connected in series between connection point C and connection point D. The control terminal of the eleventh switch transistor Q45 is electrically connected to the control circuit, the first terminal of the eleventh switch transistor Q45 is electrically connected to connection point C, and the second terminal of the eleventh switch transistor Q45 is electrically connected to the first terminal of the twelfth switch transistor Q46. The control terminal of the twelfth switch transistor Q46 is electrically connected to the control circuit, and the second terminal of the twelfth switch transistor Q46 is electrically connected to connection point D. The first terminal of the eighth inductor L8 is electrically connected to connection point C, and the second terminal of the eighth inductor L8 is electrically connected to connection point E. The first terminal of the ninth inductor L9 is electrically connected to connection point D, and the second terminal of the ninth inductor L9 is electrically connected to connection point F. The sixth capacitor C8, the seventh capacitor C9 and the eighth capacitor C10 are connected in series between the positive bus BUS+ and the negative bus BUS-, wherein the first end of the sixth capacitor C8 is electrically connected to the positive bus BUS+, and the second end of the sixth capacitor C8 is electrically connected to the connection point E; the first end of the seventh capacitor C9 is electrically connected to the connection point E, and the second end of the seventh capacitor C9 is electrically connected to the connection point F; the first end of the eighth capacitor C10 is electrically connected to the connection point F, and the second end of the eighth capacitor C10 is electrically connected to the negative bus BUS-.

[0097] In the embodiment of the present invention, the sixth to twelfth switching transistors Q3 to Q46 may each comprise an IGBT or a MOSFET. In addition, the control circuit may be used to control the on / off switching of the sixth to twelfth switching transistors Q3 to Q46.

[0098] In some embodiments, the third filtering circuit 305 may include a ninth capacitor C11, a tenth capacitor C12, a tenth inductor L10, an eleventh inductor L11, and a twelfth inductor L12. The ninth capacitor C11 and the tenth capacitor C12 are connected in series between a connection point E and a connection point F, with a first end of the ninth capacitor C11 electrically connected to the connection point E, a second end of the ninth capacitor C11 electrically connected to a first end of the tenth capacitor C12; a second end of the tenth capacitor C12 electrically connected to the connection point F; a connection point between the ninth capacitor C11 and the tenth capacitor C12 electrically connected to a neutral line 40; a first end of the tenth inductor L10 electrically connected to the connection point E, and a second end of the twelfth inductor L12 electrically connected to a port U; a first end of the eleventh inductor L11 electrically connected to the connection point F, and a second end of the eleventh inductor L11 electrically connected to a port W; and the twelfth inductor L12 is disposed on the neutral line 40 such that a first end of the twelfth inductor L12 is electrically connected to a midpoint O1 of the bus capacitor via the neutral line 40, and a second end of the twelfth inductor L12 is electrically connected to the port O via the neutral line 40.

[0099] In some embodiments, the input lightning protection circuit 60 may include a pressure-sensitive component, which includes multiple varistors. At least one varistor is electrically connected between the positive input terminal PV+ and the ground terminal PE; at least one varistor is electrically connected between the negative input terminal PV+ and the ground terminal PE. As shown in Figure 5A, a varistor is electrically connected between the positive input terminal PV+ and the ground terminal PE, with a first end of the varistor electrically connected to the positive input terminal PV+ and a second end of the varistor electrically connected to the ground terminal PE; a varistor is provided between the negative input terminal PV+ and the ground terminal PE, with a first end of the varistor electrically connected to the negative input terminal PV- and a second end of the varistor electrically connected to the ground terminal PE.

[0100] In some embodiments, the output lightning protection circuit 70 may include a pressure-sensitive component including a plurality of varistors, with at least one varistor electrically connected between each of the output ports 20 and the ground terminal PE. As shown in FIG5B , a varistor is electrically connected between port U and the ground terminal PE, with a first end of the varistor electrically connected to port U and a second end of the varistor electrically connected to the ground terminal PE; a varistor is electrically connected between port W and the ground terminal PE, with a first end of the varistor electrically connected to port W and a second end of the varistor electrically connected to the ground terminal PE; and a varistor is electrically connected between port O and the ground terminal PE, with a first end of the varistor electrically connected to port O and a second end of the varistor electrically connected to the ground terminal PE.

[0101] As shown in FIG5A , a varistor is electrically connected between port O and the PE terminal to ensure symmetry of the protection residual voltages of the input port and the output port, prevent unbalanced shunting of lightning current between the input port and the output port, and avoid damage to power devices.

[0102] As shown in FIG. 5A , in actual applications, according to product design requirements, varistors with different operating voltages may be used, which is not limited in the embodiment of the present invention.

[0103] In some embodiments, the lightning protection balancing circuit 50 includes at least one first inductor L1. As shown in FIG5A , as an optional solution, the lightning protection balancing circuit 50 includes a first inductor L1, a first end of the first inductor L1 being electrically connected to the neutral line 40, and a second end of the first inductor L1 being electrically connected to the ground terminal PE. As another optional solution, the lightning protection balancing circuit 50 may include multiple first inductors L1, and the multiple first inductors L1 may be electrically connected in parallel and / or in series, although this is not specifically shown in the figure.

[0104] In some embodiments, the first inductor L1 can be an inductor that is not easily saturated. As an alternative, the first inductor L1 can include an air-core inductor or a magnetic rod inductor. Both air-core inductors and magnetic rod inductors are not easily saturated. Using an inductor that is not easily saturated can ensure that a voltage is generated across the first inductor L1, thereby increasing the protective residual voltage of the lightning discharge path of the output port 20. As shown in Figure 5A, for example, the first inductor L1 is an air-core inductor.

[0105] In some embodiments, as shown in FIG5A , the photovoltaic inverter may further include a first switch K1 electrically connected between the neutral line 40 and the first inductor L1. A first end of the first switch K1 is electrically connected to the neutral line 40, a second end of the first switch K1 is electrically connected to the first end of the first inductor L1, and the second end of the first inductor L1 is electrically connected to the ground terminal PE. In actual applications, the first switch K1 may also be electrically connected between the first inductor L1 and the ground terminal PE, where the first end of the first inductor L1 is electrically connected to the neutral line 40, the second end of the first inductor L1 is electrically connected to the first end of the first switch K1, and the second end of the first switch L1 is electrically connected to the ground terminal PE. This embodiment is not specifically shown. When the photovoltaic inverter is in off-grid power supply mode, the first switch K1 is closed, and conduction is established between the neutral line 40 and the first inductor L1. The neutral line 40 may be electrically connected to the ground terminal PE via the first inductor L1, i.e., the first inductor L1 is electrically connected between the neutral line 40 and the ground terminal PE. When the photovoltaic inverter is in the grid-connected power supply mode, the first switch K1 is disconnected. At this time, the neutral line 40 and the first inductor L1 are disconnected, and the neutral line 40 cannot be electrically connected to the ground terminal PE through the first inductor L1.

[0106] As shown in FIG5A , the midpoint O1 of the busbar capacitor is electrically connected to the ground terminal PE via the first inductor L1. During a lightning strike, the input port 10 is coupled to the lightning voltage, i.e., the input port 10 is instantaneously induced by the lightning voltage. Consequently, the voltage at the input port 10 increases, reaching the operating voltage of the varistor in the input lightning protection circuit 60. At this point, under the action of the first inductor L1, the protective residual voltage of the lightning discharge path of the output port 20 increases, minimizing the difference in protective residual voltage between the input port 10 and the output port 20. This means that the first inductor L1 can balance the protective residual voltages of the input port 10 and the output port 20. The varistor in the input lightning protection circuit 60 discharges the lightning overvoltage and overcurrent, achieving localized discharge of the lightning current, preventing large lightning currents from flowing through the main power circuit, and thereby preventing damage to the power devices in the main power circuit. The voltage of the first inductor L1 can be L*di / dt, where L is the inductance of the first inductor L1 and di / dt is the rate of change of current with respect to time.

[0107] As shown in FIG5A , the technical solution of the embodiment of the present invention can effectively solve the problem of unbalanced residual voltage protection of the input port 10 and the output port 20 during a lightning strike in the topology of the hybrid photovoltaic inverter. The common-mode protection capability of the input port 10 can reach a two-wire common-mode current of 5KA to 10kA, and the lightning protection capability of the photovoltaic inverter can meet the lightning protection specification of a two-wire common-mode current of 5KA to 10kA. As an optional solution, in the embodiment of the present invention, the lightning protection capability of the photovoltaic inverter can meet the lightning protection specification of a two-wire common-mode current of 10kA. Among them, the "two-wire" in the two-wire common-mode current refers to the positive input terminal PV+ and the negative input terminal PV-. For example, in FIG5A , the two-wire common-mode current of the positive input terminal PV+ and the negative input terminal PV- is 10kA.

[0108] FIG5B is a schematic structural diagram of a photovoltaic inverter in some other embodiments. As shown in FIG5B , the difference from the photovoltaic inverter shown in FIG5A is that the input-end lightning protection circuit 60 further includes a first gas discharge tube G1, and the output-end lightning protection circuit 70 further includes a second gas discharge tube G2.

[0109] The first gas discharge tube G1 is electrically connected between the pressure-sensitive component and the ground terminal PE, and the pressure-sensitive component can be electrically connected to the ground terminal PE through the first gas discharge tube G1. The first end of the first gas discharge tube G1 is electrically connected to the pressure-sensitive component, and the second end of the first gas discharge tube G1 is electrically connected to the ground terminal PE.

[0110] The second gas discharge tube G2 is electrically connected between the plurality of varistors and the ground terminal PE. A first end of the second gas discharge tube G2 is electrically connected to the varistor assembly, and a second end of the second gas discharge tube G2 is electrically connected to the ground terminal PE.

[0111] As shown in FIG5B , the midpoint O1 of the bus capacitor is electrically connected to the ground terminal PE via the first inductor L1. During a lightning strike, the input port 10 is coupled to the lightning voltage, i.e., the input port 10 instantaneously senses the lightning voltage. As a result, the voltage of the input port 10 increases, and the voltage of the input port 10 reaches the operating voltage of the varistor and the first gas discharge tube G1 in the input-end lightning protection circuit 60. At this time, under the action of the first inductor L1, the protective residual voltage of the lightning discharge path of the output port 20 increases, so that the difference in the protective residual voltage between the input port 10 and the output port 20 is small. That is, the first inductor L1 can balance the protective residual voltage between the input port 10 and the output port 20. The varistor and the first gas discharge tube G1 of the input-end lightning protection circuit 60 discharge the lightning overvoltage and overcurrent, thereby achieving local discharge of the lightning current, preventing a large lightning current from flowing through the main power circuit, and thus preventing damage to the power devices in the main power circuit. The voltage of the first inductor L1 may be L*di / dt, where L is the inductance of the first inductor L1 and di / dt is the rate of change of current with respect to time.

[0112] Compared with the technical solution in Figure 5A, the input-end lightning protection circuit 60 and the output-end lightning protection circuit 70 in Figure 5B are both provided with gas discharge tubes electrically connected to the pressure-sensitive components, which improves the discharge capacity of the input-end lightning protection circuit 60 and the output-end lightning protection circuit 70 for lightning current, further avoids large lightning current flowing through the main power circuit, and thus further avoids damage to the power devices in the main power circuit.

[0113] FIG6 is a schematic diagram of the structure of a photovoltaic power generation system in some embodiments. As shown in FIG6 , the photovoltaic power generation system includes a photovoltaic panel 1 and a photovoltaic inverter 2. The photovoltaic inverter 2 can be the photovoltaic inverter shown in FIG3 , FIG4A , FIG4Bb , FIG5A , or FIG5B . For a detailed description, please refer to the description of the embodiments shown in FIG3 , FIG4A , FIG4Bb , FIG5A , or FIG5B .

[0114] The photovoltaic panel 1 is electrically connected to the input port 10 . The photovoltaic panel 1 is used to convert light energy into a DC voltage and output it to the input port 10 . The photovoltaic inverter 2 is used to convert the DC voltage into an AC voltage and output it through the output port 20 .

[0115] In some embodiments, the output port 20 of the photovoltaic inverter 2 is electrically connected to the grid 3. When the photovoltaic inverter is in a grid-connected power supply mode, the photovoltaic inverter 2 outputs an AC voltage to the grid 3 through the output port 20. In some embodiments, the output port 20 of the photovoltaic inverter 2 is electrically connected to a load 4. When the photovoltaic inverter is in an off-grid power supply mode, the photovoltaic inverter 2 outputs an AC voltage to the load 4 through the output port 20 to power the load 4. For example, the load 4 may include a refrigerator, a television, a computer, etc.

[0116] In some embodiments, the photovoltaic power generation system further includes an energy storage device 5, which can provide additional DC power input to the photovoltaic inverter 2 when the photovoltaic power generation system's energy input is insufficient, and can also store excess energy when the photovoltaic power generation system's energy output is excessive. For example, the energy storage device 5 can be a battery.

[0117] In the technical solution provided by the embodiment of the present invention, the input-end lightning protection circuit is electrically connected between the input port and the ground terminal, the output-end lightning protection circuit is electrically connected between the output port and the ground terminal, and the neutral line and the ground terminal are electrically connected to the lightning protection balancing circuit. During a lightning strike, the lightning protection balancing circuit can balance the protective residual voltage of the input port and the protective residual voltage of the output port, so that the difference in protective residual voltage between the input port and the output port during a lightning strike is small, so that the lightning current of the input port can be discharged through the input-end lightning protection circuit, avoiding the large lightning current of the input port from being discharged through the opposite end. At this time, the lightning current flowing through the power devices inside the main power circuit is small, thereby avoiding damage to the power devices of the main power circuit.

[0118] In the embodiment of the present invention, "at least one" refers to one or more, and "more" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and subsequent associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0119] The above description is merely a specific embodiment of the present invention. Any modifications or substitutions that may be readily conceived by a person skilled in the art within the technical scope disclosed herein are intended to be encompassed within the scope of protection of the present invention. The scope of protection of the present invention shall be determined by the scope of protection of the claims.

Claims

1. A photovoltaic inverter, characterized in that: include: An input port, an output port, a main power circuit, an input-end lightning protection circuit, and an output-end lightning protection circuit, wherein the main power circuit is electrically connected between the input port and the output port, the main power circuit and the output port are electrically connected to a neutral line, the input-end lightning protection circuit is electrically connected between the input port and a ground terminal, and the output-end lightning protection circuit is electrically connected between the output port and the ground terminal; The input-end lightning protection circuit is used to discharge the lightning current of the input port, and the output-end lightning protection circuit is used to discharge the lightning current of the output port; A lightning protection balancing circuit is electrically connected between the neutral line and the ground terminal, and the lightning protection balancing circuit is used to balance the protection residual voltage of the input port and the protection residual voltage of the output port during a lightning strike.

2. The photovoltaic inverter according to claim 1, characterized in that: The lightning protection balancing circuit includes at least one first inductor.

3. The photovoltaic inverter according to claim 2, characterized in that: The first inductor includes an air-core inductor or a magnetic rod inductor.

4. The photovoltaic inverter according to any one of claims 1 to 3, characterized in that: The photovoltaic inverter further includes a first switch; The first switch is electrically connected between the neutral line and the lightning protection balancing circuit; or, The first switch is electrically connected between the lightning protection balancing circuit and the ground terminal.

5. The photovoltaic inverter according to claim 1, characterized in that: The main power circuit includes at least one group of bus capacitors electrically connected between the positive bus and the negative bus, and the midpoint of each group of bus capacitors is electrically connected to the neutral line.

6. The photovoltaic inverter according to claim 5, characterized in that: The main power circuit further includes a boost circuit and an inverter circuit, wherein the boost circuit is electrically connected between the input port and the bus capacitor, and the inverter circuit is electrically connected between the bus capacitor and the output port; The boost circuit is used to convert the DC voltage input from the input port into an operating voltage; The inverter circuit is used to convert the operating voltage into an AC voltage and output the AC voltage to an output port.

7. The photovoltaic inverter according to claim 1, characterized in that: The input port includes a negative input terminal and at least one positive input terminal.

8. The photovoltaic inverter according to claim 1, characterized in that: The output port includes a three-phase output port and a port N, and the port N is electrically connected to the neutral line.

9. The photovoltaic inverter according to claim 1, characterized in that: The output port includes a two-phase output port and a port O, and the port O is electrically connected to the neutral line.

10. A photovoltaic power generation system, characterized in that: include: A photovoltaic panel and a photovoltaic inverter according to any one of claims 1 to 9, wherein the photovoltaic panel is electrically connected to the input port; The photovoltaic panel is used to convert light energy into a DC voltage and output it to the input port; The photovoltaic inverter is used to convert the DC voltage into an AC voltage and output the AC voltage through the output port.

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