Inverter and photovoltaic system

Abstract

The utility model discloses an inverter and a photovoltaic system, and belongs to the technical field of electric power. The inverter comprises a direct-current input source, a voltage-sharing circuit, a direct-current bus capacitor, an inverter circuit and a switch module, the direct-current bus capacitor comprises two groups of capacitors connected in series; the voltage-sharing circuit adopts a balance bridge circuit; the inverter circuit comprises a first phase circuit, a second phase circuit and a third phase circuit which all adopt three-level T-shaped structures; the switch module comprises a first switch unit, a second switch unit, a third switch unit and a fourth switch unit; the first end of the first switch unit is connected with the output end of the first phase circuit; the first end of the second switch unit is connected with the output end of the second phase circuit; the first end of the third switch unit is connected with the output end of the third phase circuit; the first end of the fourth switch unit is connected with the neutral point of the bus of the inverter circuit. According to the inverter and the photovoltaic system provided by the invention, three-phase, split-phase and single-phase on-grid and off-grid operation can be realized in various scenes.

Description

Technical Field

[0001] The present application belongs to the field of electric power technology, and in particular relates to an inverter and a photovoltaic system. Background Art

[0002] In the process of renewable energy power generation, it is necessary to convert renewable energy such as solar energy or wind energy into electrical energy through power conversion. The inverter is the core device for realizing power conversion. The output modes of the inverter mainly include three-phase output, split-phase output and single-phase output, etc., to adapt to the standards of different power supply systems.

[0003] However, the general inverter is only suitable for a single type of power grid, has only one output mode, and has a limited scope of application. Developing different inverters with only a single output mode will greatly increase the R&D time and cost of the inverter. In order to solve the above problems, the existing technology mainly adopts two methods: one is to adjust the line of the inverter additionally, and the other is to add a switching unit in the circuit. The additional line adjustment method of the inverter also requires corresponding changes in the wiring method of the inverter or even changes in the single-board wiring to achieve adaptation to multiple power grids, but it still cannot meet the requirements that the same inverter can be applied to three-phase power grid systems and single-phase power grid systems. The method of adding a switching unit in the circuit generally adds a switching unit between the two-phase output terminals of the inverter and between the output terminal of the third-phase branch and the midpoint of the intermediate circuit to achieve switching operation between three-phase output and single-phase output, but it cannot operate in the scenario of off-grid operation with unbalanced load in three-phase mode or independent backflow protection for each phase of the grid. The above technologies all realize the switching between three-phase operation and single-phase operation, and cannot be realized in a split-phase system.

[0004] In summary, the existing technology cannot achieve the switching of three-phase, split-phase and single-phase operation of the same photovoltaic inverter for different power systems. Utility Model Content

[0005] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, the present application proposes an inverter and a photovoltaic system, which realize the switching of three-phase, split-phase and single-phase according to different application scenarios.

[0006] In a first aspect, the present application provides an inverter, comprising: a DC input source, a voltage balancing circuit, a DC bus capacitor, an inverter circuit and a switch module; the DC input source is connected to the inverter circuit through the voltage balancing circuit and the DC bus capacitor in sequence;

[0007] The DC bus capacitor includes two sets of capacitors connected in series;

[0008] The voltage equalizing circuit adopts a balanced bridge circuit;

[0009] The inverter circuit comprises a first phase circuit, a second phase circuit and a third phase circuit; the first phase circuit, the second phase circuit and the third phase circuit all adopt a three-level T-type structure;

[0010] The switch module includes a first switch unit, a second switch unit, a third switch unit and a fourth switch unit;

[0011] The first end of the first switch unit is connected to the output end of the first phase circuit, and the second end of the first switch unit serves as the first output end of the inverter;

[0012] The first end of the second switch unit is connected to the output end of the second phase circuit, and the second end of the second switch unit serves as the second output end of the inverter;

[0013] The first end of the third switch unit is connected to the output end of the third phase circuit, and the second end of the third switch unit serves as the third output end of the inverter;

[0014] The first end of the fourth switch unit is connected to the neutral point of the busbar of the inverter circuit, and the second end of the fourth switch unit serves as the fourth end of the inverter;

[0015] The on / off states of the first switch unit, the second switch unit, the third switch unit, and the fourth switch unit correspond to the operation mode of the inverter.

[0016] According to the inverter of the present application, by adopting the voltage equalization circuit of the balanced bridge circuit, the voltage of the two groups of capacitors of the DC bus capacitor is balanced, so as to avoid the uneven voltage of the two groups of capacitors of the DC bus capacitor due to load imbalance, which causes one of the two groups of capacitors to be damaged due to overvoltage. The inverter can operate in the scenario of unbalanced load (including three-phase mode and split-phase mode), can realize three-phase, split-phase and single-phase parallel and off-grid operation in different scenarios, and can be applied to three-phase, split-phase and single-phase photovoltaic systems that support parallel and off-grid operation. Furthermore, the switching between three-phase output, split-phase output and single-phase output can be realized only by controlling the opening and closing states of each switch unit included in the switch module according to the operating mode of the inverter, without changing the wiring method of the inverter or the wiring of the single board, and the switching between three-phase output, split-phase output and single-phase output is simpler and more convenient.

[0017] According to an embodiment of the present application, the first phase circuit includes: a first power tube, a second power tube, a third power tube, a fourth power tube and a first driving control unit;

[0018] The first power tube is connected in series with the fourth power tube in a forward direction; one end of the first power tube connected with the fourth power tube serves as the output end of the first phase circuit; the second power tube is connected in series with the third power tube in a reverse direction, connecting the neutral point of the busbar of the inverter circuit and the output end of the first phase circuit;

[0019] The first drive control unit is connected to the first power tube, the second power tube, the third power tube and the fourth power tube respectively to control the first power tube, the second power tube, the third power tube and the fourth power tube based on the operation mode of the inverter.

[0020] According to one embodiment of the present application, the second phase circuit includes: a fifth power tube, a sixth power tube, a seventh power tube, an eighth power tube and a second driving control unit;

[0021] The fifth power tube is connected in series with the eighth power tube in a forward direction; one end of the fifth power tube connected to the eighth power tube serves as the output end of the second phase circuit; the sixth power tube is connected in series with the seventh power tube in a reverse direction, connecting the neutral point of the busbar of the inverter circuit and the output end of the second phase circuit;

[0022] The second drive control unit is connected to the fifth power tube, the sixth power tube, the seventh power tube and the eighth power tube respectively to control the fifth power tube, the sixth power tube, the seventh power tube and the eighth power tube based on the operation mode of the inverter.

[0023] According to an embodiment of the present application, the third phase circuit includes: a ninth power tube, a tenth power tube, an eleventh power tube, a twelfth power tube and a third driving control unit;

[0024] The ninth power tube is connected in series with the twelfth power tube in a forward direction; one end of the ninth power tube connected with the twelfth power tube serves as the output end of the third phase circuit; the tenth power tube is connected in series with the eleventh power tube in a reverse direction, connecting the neutral point of the busbar of the inverter circuit and the output end of the third phase circuit;

[0025] The third driving control unit is connected to the ninth power tube, the tenth power tube, the eleventh power tube and the twelfth power tube respectively to control the ninth power tube, the tenth power tube, the eleventh power tube and the twelfth power tube based on the operation mode of the inverter.

[0026] According to an embodiment of the present application, when the operation mode of the inverter is a three-phase grid-connected mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is closed, and the fourth switch unit is closed or opened;

[0027] When the operation mode of the inverter is the three-phase off-grid mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is closed, and the fourth switch unit is closed.

[0028] According to an embodiment of the present application, when the operation mode of the inverter is the split-phase grid-connected mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is closed or opened;

[0029] When the operation mode of the inverter is the split-phase off-grid mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is closed.

[0030] According to an embodiment of the present application, when the operation mode of the inverter is the single-phase grid-connected mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is opened;

[0031] When the operation mode of the inverter is the single-phase off-grid mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is opened.

[0032] According to an embodiment of the present application, the voltage balancing circuit includes: a first switch tube, a second switch tube and an inductor;

[0033] The first switch tube is connected in series with the second switch tube; the first end of the inductor is connected to one end of the first switch tube connected to the second switch tube; the second end of the inductor, as the output end of the voltage balancing circuit, is connected to the neutral point of the busbar of the inverter circuit.

[0034] According to an embodiment of the present application, each group of capacitors in the DC bus capacitor includes: one capacitor or multiple capacitors connected in parallel.

[0035] According to an embodiment of the present application, it further includes: a filtering circuit; the filtering circuit includes a first filtering unit, a second filtering unit and a third filtering unit;

[0036] The input end of the first filtering unit is connected to the output end of the first phase circuit, and the output end of the first filtering unit is connected to the first end of the first switch unit, so as to filter the AC voltage output by the first phase circuit;

[0037] The input end of the second filtering unit is connected to the output end of the second phase circuit, and the output end of the second filtering unit is connected to the first end of the second switch unit, so as to filter the AC voltage output by the second phase circuit;

[0038] The input end of the third filtering unit is connected to the output end of the third phase circuit, and the output end of the third filtering unit is connected to the first end of the third switch unit to filter the AC voltage output by the third phase circuit.

[0039] According to one embodiment of the present application, the first filtering unit, the second filtering unit and the third filtering unit are all LC filters.

[0040] According to one embodiment of the present application, the inverter is a photovoltaic inverter.

[0041] In a second aspect, the present application provides a photovoltaic system, which includes: the inverter as described in the first aspect.

[0042] According to the photovoltaic system of the present application, by adopting the inverter as described in the first aspect, switching among three-phase operation, split-phase operation and single-phase operation can be realized for different systems, and three-phase operation, split-phase operation and single-phase operation can be realized in different grid-connected and off-grid scenarios.

[0043] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0045] Figure 1 is a schematic diagram of the structure of the inverter provided in an embodiment of the present application;

[0046] Figure 2 It is one of the schematic diagrams of the operating state of the inverter provided in the embodiment of the present application;

[0047] Figure 3 This is a second schematic diagram of the operating state of the inverter provided in the embodiment of the present application;

[0048] Figure 4 This is the third schematic diagram of the operating state of the inverter provided in the embodiment of the present application;

[0049] Figure 5 This is a fourth schematic diagram of the operating state of the inverter provided in the embodiment of the present application;

[0050] Figure 6This is a fifth schematic diagram of the operating state of the inverter provided in the embodiment of the present application;

[0051] Figure 7 This is the sixth schematic diagram of the operating state of the inverter provided in the embodiment of the present application;

[0052] Figure 8 It is one of the schematic diagrams of the wave generation mode of the inverter operation provided in the embodiment of the present application;

[0053] Fig. 9 This is the second schematic diagram of the wave generation mode of the inverter operation provided in the embodiment of the present application.

[0054] Reference numerals:

[0055] 100: inverter; 110: DC input source; 120: voltage balancing circuit; 130: DC bus capacitor; 140: inverter circuit; 150: switch module; 160: filter circuit; 200: load; 141: first phase circuit; 142: second phase circuit; 143: third phase circuit; K1: first switch unit; K2: second switch unit; K3: third switch unit; K4: fourth switch unit; BUS_N: neutral point of bus; Q A1 : The first power tube; Q A2 : The second power tube; Q A3 : The third power tube; Q A4 : The fourth power tube; Q B1 : The fifth power tube; Q B2 : The sixth power tube; Q B3 : The seventh power tube; Q B4 : The eighth power tube; Q C1 : The ninth power tube; Q C2 : The tenth power tube; Q C3 : Eleventh power tube; Q C4 : twelfth power tube; Q1: first switch tube; Q2: second switch tube; L1: inductor. DETAILED DESCRIPTION

[0056] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0057] Reference below Figure 1-Figure 9 An inverter and a photovoltaic system according to embodiments of the present application are described.

[0058] Figure 1 Schematic diagram of the structure of the inverter provided in the embodiment of the present application. Figure 1As shown, an inverter 100 includes: a DC input source 110, a voltage balancing circuit 120, a DC bus capacitor 130, an inverter circuit 140 and a switch module 150; the DC input source 110 is connected to the inverter circuit 140 through the voltage balancing circuit 120 and the DC bus capacitor 130 in sequence.

[0059] In actual implementation, the inverter 100 may be a three-level T-type inverter circuit with a balanced bridge circuit. The inverter 100 may be driven and controlled using different control signals according to its own different operating modes, and the inverter 100 may be used in three-phase, split-phase or single-phase power grids. Split Phase, also known as phase separation, refers to the splitting of single-phase DC into multi-phase AC.

[0060] According to the different output modes of the inverter 100, the operation mode of the inverter 100 may include a three-phase mode, a split-phase mode and a single-phase mode. According to whether the inverter 100 is connected to the power grid, the operation mode of the inverter 100 may include a grid-connected mode and an off-grid mode. On this basis, the operation mode of the inverter 100 can be further subdivided into a three-phase grid-connected mode, a three-phase off-grid mode, a split-phase grid-connected mode, a split-phase off-grid mode, a single-phase grid-connected mode and a single-phase off-grid mode. The three-phase grid-connected mode and the three-phase off-grid mode both belong to the three-phase mode; the split-phase grid-connected mode and the split-phase off-grid mode both belong to the split-phase mode; the single-phase grid-connected mode and the single-phase off-grid mode both belong to the single-phase mode. The three-phase grid-connected mode, the split-phase grid-connected mode and the single-phase grid-connected mode all belong to the grid-connected mode; the three-phase off-grid mode, the split-phase off-grid mode and the single-phase off-grid mode all belong to the off-grid mode.

[0061] It should be noted that the split-phase mode can be divided into a split-two-phase mode and a split-three-phase mode. Since the operation mode of the inverter 100 is basically the same in the split-three-phase mode and the three-phase mode, in the embodiment of the present application, the split-phase mode can specifically refer to the split-two-phase mode, and the split-phase power grid is a two-phase power grid.

[0062] It should be noted that split phase is caused by single phase. In the scenario where only three-phase and single-phase are distinguished, the three-phase operation of the inverter includes three-phase grid-connected mode and three-phase off-grid mode; the single-phase operation of the inverter includes single-phase mode and split phase mode, specifically including split phase grid-connected mode, split phase off-grid mode, single-phase grid-connected mode and single-phase off-grid mode.

[0063] The inverter 100 may mainly include a DC input source 110 , a voltage balancing circuit 120 , a DC bus capacitor 130 , an inverter circuit 140 and a switch module 150 .

[0064] The DC input source 110 is used to generate a DC voltage. The DC voltage can be denoted as U dcThe DC input source 110 is connected to the voltage balancing circuit 120, the voltage balancing circuit 120 is connected to the DC bus capacitor 130, and the DC bus capacitor 130 is connected to the inverter circuit 140. The DC voltage output by the DC input source 110 passes through the voltage balancing circuit 120 and the DC bus capacitor 130 in sequence, and then is converted into an AC voltage by the inverter circuit 140.

[0065] The DC bus capacitor 130 includes two sets of capacitors connected in series.

[0066] In actual implementation, the function of the DC bus capacitor 130 is to stabilize the bus voltage of the inverter circuit 140 so that the maximum fluctuation of the potential of the neutral point BUS_N of the bus of the inverter circuit 140 does not exceed the target threshold.

[0067] It is understood that the bus is a DC bus. The target threshold can be determined based on the voltage difference between the positive and negative electrodes of the bus. The specific value of the target threshold is not limited in the embodiment of the present application. For example, the target threshold can be 0.05-0.1V BUS , V BUS Indicates the voltage difference between the positive and negative poles of the busbar.

[0068] In some embodiments, the DC bus capacitor 130 may include two groups of capacitors, which are connected in series.

[0069] In some embodiments, each group of capacitors may include one or more capacitors.

[0070] In some embodiments, any capacitor included in each group of capacitors may be an electrolytic capacitor or a film capacitor, but is not limited to an electrolytic capacitor and a film capacitor.

[0071] The voltage equalizing circuit 120 adopts a balanced bridge circuit.

[0072] In actual implementation, the voltage balancing circuit 120 is used to balance the voltages of the two groups of capacitors included in the DC bus capacitor 130, that is, to make the voltages of the two groups of capacitors substantially equal to avoid the phenomenon of overvoltage in one group of capacitors. The voltage balancing circuit 120 can usually adopt a balanced bridge circuit.

[0073] It should be noted that in the three-phase output scenario operating in off-grid mode and with an unbalanced load, the inverter 100 provided in the embodiment of the present application can balance the voltage of the two groups of capacitors of the DC bus capacitor 130 by adopting the voltage equalization circuit 120 of the balanced bridge circuit, thereby avoiding the unbalanced voltage of the two groups of capacitors of the DC bus capacitor 130 due to load imbalance, resulting in damage to one of the two groups of capacitors due to overvoltage.

[0074] The inverter circuit 140 includes a first phase circuit 141 , a second phase circuit 142 and a third phase circuit 143 ; the first phase circuit 141 , the second phase circuit 142 and the third phase circuit 143 all adopt a three-level T-type structure.

[0075] In actual implementation, the inverter circuit 140 may include three parts, each corresponding to a phase of the power grid. The three parts may be a first phase circuit 141, a second phase circuit 142, and a third phase circuit 143. The first phase circuit 141, the second phase circuit 142, and the third phase circuit 143 are all one-phase circuits included in the inverter circuit 140.

[0076] In some embodiments, the first phase circuit 141, the second phase circuit 142 and the third phase circuit 143 may all adopt a three-level T-type structure. The functions of the first phase circuit 141, the second phase circuit 142 and the third phase circuit 143 are to convert the input DC voltage into AC voltage and then output it based on the operation mode of the inverter 100.

[0077] The switch module 150 includes a first switch unit K1 , a second switch unit K2 , a third switch unit K3 and a fourth switch unit K4 .

[0078] In actual implementation, the switch module 150 is used to connect the inverter 100 and the load 200. In the grid-connected mode, the load 200 is various types of grids, such as a three-phase grid, a split-phase grid or a single-phase grid; in the off-grid mode, the load 200 can be represented by an impedance Z.

[0079] The switch module 150 may include a switch device as an output terminal of the inverter 100 and a switch device connected in series from a neutral point BUS_N of a bus of the inverter circuit 140 .

[0080] In some embodiments, the switching device may be a relay, any switching circuit or any other element with a switching function (such as a switching diode or a transistor, etc.).

[0081] In some embodiments, the switch device at the output end of the inverter 100 may include a first switch unit K1, a second switch unit K2 and a third switch unit K3; the switch device connected in series from the neutral point BUS_N of the busbar of the inverter circuit 140 may be a fourth switch unit K4.

[0082] A first end of the first switch unit K1 is connected to the output end of the first phase circuit 141 , and a second end of the first switch unit K1 serves as a first output end of the inverter 100 .

[0083] In actual implementation, the first switch unit K1 , the second switch unit K2 , and the third switch unit K3 may correspond one-to-one to the three parts included in the inverter circuit 140 .

[0084] The first switch unit K1 may correspond to the first phase circuit 141. Two ends of the first switch unit K1 may be respectively connected to the output end of the first phase circuit 141 and the load 200. One end of the first switch unit K1 connected to the load 200 (i.e., the second end of the first switch unit K1) is the first output end of the inverter 100.

[0085] A first end of the second switch unit K2 is connected to the output end of the second phase circuit 142 , and a second end of the second switch unit K2 serves as a second output end of the inverter 100 .

[0086] In actual implementation, the second switch unit K2 may correspond to the second phase circuit 142. Two ends of the second switch unit K2 may be respectively connected to the output end of the second phase circuit 142 and the load 200. One end of the second switch unit K2 connected to the load 200 (i.e., the second end of the second switch unit K2) is the second output end of the inverter 100.

[0087] A first end of the third switch unit K3 is connected to the output end of the third phase circuit, and a second end of the third switch unit K3 serves as a third output end of the inverter 100.

[0088] In actual implementation, the third switch unit K3 may correspond to the third phase circuit 143. Two ends of the third switch unit K3 may be respectively connected to the output end of the third phase circuit 143 and the load 200. One end of the third switch unit K3 connected to the load 200 (i.e., the second end of the third switch unit K3) is the third output end of the inverter 100.

[0089] A first end of the fourth switch unit K4 is connected to the neutral point of the busbar of the inverter circuit, and a second end of the fourth switch unit serves as a fourth end of the inverter 100 .

[0090] In actual implementation, the two ends of the fourth switch unit K4 can be used to connect the neutral point BUS_N of the bus of the inverter circuit 140 and the load 200 respectively. The first end of the fourth switch unit K4 is connected to the neutral point BUS_N of the bus of the inverter circuit 140. When the fourth switch unit K4 is in a closed state, the load 200 can be connected to the neutral point BUS_N of the bus of the inverter circuit 140.

[0091] The on / off states of the first switch unit K1 , the second switch unit K2 , the third switch unit K3 and the fourth switch unit K4 correspond to the operation mode of the inverter 100 .

[0092] In actual implementation, the on / off states of the first switch unit K1 , the second switch unit K2 , and the third switch unit K3 all correspond to the operation mode of the inverter 100 .

[0093] When the operation mode of the inverter 100 is the three-phase mode, the first switch unit K1 , the second switch unit K2 and the third switch unit K3 are all in a closed state.

[0094] When the operation mode of the inverter 100 is the three-phase mode, two of the first switch unit K1, the second switch unit K2, and the third switch unit K3 are in a closed state, and the remaining one is in an open state. Specifically, which two of the first switch unit K1, the second switch unit K2, and the third switch unit K3 are in a closed state is determined according to the specific connection mode between the load 200 and the inverter 100. As to which two of the first switch unit K1, the second switch unit K2, and the third switch unit K3 are in a closed state, the embodiment of the present application does not limit it.

[0095] When the operation mode of the inverter 100 is the single-phase mode, two of the first switch unit K1, the second switch unit K2, and the third switch unit K3 are in a closed state, and the remaining one is in an open state. Specifically, which two of the first switch unit K1, the second switch unit K2, and the third switch unit K3 are in a closed state is determined according to the specific connection mode between the load 200 and the inverter 100. As to which two of the first switch unit K1, the second switch unit K2, and the third switch unit K3 are in a closed state, the embodiment of the present application does not limit it.

[0096] The on / off state of the fourth switch unit K4 also corresponds to the operation mode of the inverter 100. When the operation mode of the inverter 100 is the grid-connected mode and the three-phase off-grid mode, the fourth switch unit K4 is in the open state. When the operation mode of the inverter 100 is the three-phase off-grid mode and the split-phase off-grid mode, the fourth switch unit K4 is in the closed state to connect the load 200 and the neutral point BUS_N of the busbar of the inverter circuit 140.

[0097] According to the inverter provided in the embodiment of the present application, by adopting the voltage equalization circuit of the balanced bridge circuit, the voltage of the two groups of capacitors of the DC bus capacitor is balanced, so as to avoid the uneven voltage of the two groups of capacitors of the DC bus capacitor due to load imbalance, which causes one of the two groups of capacitors to be damaged due to overvoltage. It can operate in scenarios with unbalanced loads (including three-phase mode and split-phase mode), and can realize three-phase, split-phase and single-phase parallel and off-grid operation in different scenarios, and can be applied to three-phase, split-phase and single-phase photovoltaic systems that support parallel and off-grid operation. Furthermore, by controlling the opening and closing states of each switch unit included in the switch module according to the operating mode of the inverter, the switching between three-phase output, split-phase output and single-phase output can be realized, without changing the wiring method of the inverter or the wiring of the single board, and the switching between three-phase output, split-phase output and single-phase output is simpler and more convenient.

[0098] In some embodiments, Figures 1 to 7 As shown, the first phase circuit 141 includes: a first power tube Q A1 , the second power tube Q A2 、The third power tube Q A3 、The fourth power tube Q A4 and a first drive control unit.

[0099] In actual implementation, each phase circuit included in the inverter circuit 140 may be composed of four power transistors and a drive control unit. The drive control unit is used to drive the above four power transistors to achieve each phase circuit converting the input DC voltage in different operating modes into the corresponding AC voltage for output.

[0100] In some embodiments, each of the power tubes can be formed by connecting a diode and a switch device in parallel.

[0101] The four power tubes included in the first phase circuit 141 may be: the first power tube Q A1 , the second power tube Q A2 、The third power tube Q A3 And the fourth power tube Q A4 The first phase circuit 141 includes a driving control unit which is a first driving control unit ( Figures 1 to 7 not shown).

[0102] The first power tube Q A1 With the fourth power tube Q A4 Forward series connection; the first power tube Q A1 With the fourth power tube Q A4 One end connected is used as the output end of the first phase circuit 141; the second power tube Q A2 With the third power tube Q A3 The inverter circuit 140 is connected in reverse series to connect the neutral point BUS_N of the busbar and the output end of the first phase circuit 141 .

[0103] In actual implementation, a second power tube Q is provided between the neutral point BUS_N of the busbar of the inverter circuit 140 and the output end of the first phase circuit 141. A2 With the third power tube Q A3 , the second power tube Q A2 With the third power tube Q A3 Reverse series connection, the second power tube Q A2 The third power tube Q is not connected A3 One end of the third power tube Q A3 The second power tube Q is not connected A2 One end of the first power tube Q can be connected to the neutral point BUS_N of the busbar of the inverter circuit 140. A1With the fourth power tube Q A4 Forward series connection, the first power tube Q A1 With the fourth power tube Q A4 The connection point is the output end of the first phase circuit 141, and the first power tube Q A1 The end not connected to the output end of the first phase circuit 141 can be connected to the positive electrode of the DC input source 110. A4 The end not connected to the output end of the first phase circuit 141 can be connected to the negative electrode of the DC input source 110. A1 , the second power tube Q A2 、The third power tube Q A3 And the fourth power tube Q A4 Based on the above connection relationship, a three-level T-type structure can be formed.

[0104] The first driving control unit is respectively connected to the first power tube Q A1 , the second power tube Q A2 、The third power tube Q A3 And the fourth power tube Q A4 connected to control the first power tube Q based on the operating mode of the inverter 100 A1 , the second power tube Q A2 、The third power tube Q A3 And the fourth power tube Q A4 .

[0105] In actual implementation, the first drive control unit is respectively connected to the first power tube Q A1 , the second power tube Q A2 、The third power tube Q A3 And the fourth power tube Q A4 The first driving control unit can generate a control signal corresponding to the operating mode based on the operating mode of the inverter 100 to control the first power tube Q A1 , the second power tube Q A2 、The third power tube Q A3 And the fourth power tube Q A4 After the DC voltage input to the first phase circuit 141 is converted into an AC voltage, the AC voltage is output from the output end of the first phase circuit 141 .

[0106] According to the inverter provided in the embodiment of the present application, after the second power tube and the third power tube are connected in reverse series, they are connected to the connection point of the first power tube and the fourth power tube in forward series, forming a first phase circuit of a three-level T-type structure, which can reduce the voltage stress on the input side of the first phase circuit and can more effectively suppress the harmonics of the output voltage.

[0107] In some embodiments, the second phase circuit 142 includes: a fifth power tube Q B1 、The sixth power tube QB2 、The seventh power tube Q B3 、The eighth power tube Q B4 and a second drive control unit.

[0108] In actual implementation, the four power tubes included in the second phase circuit 142 may be: the fifth power tube Q B1 、The sixth power tube Q B2 、The seventh power tube Q B3 And the eighth power tube Q B4 The second phase circuit 142 includes a driving control unit which is a second driving control unit ( Figures 1 to 7 not shown).

[0109] The fifth power tube Q B1 With the eighth power tube Q B4 Forward series connection; the fifth power tube Q B1 With the eighth power tube Q B4 One end connected is used as the output end of the second phase circuit 142; the sixth power tube Q B2 With the seventh power tube Q B3 The neutral point BUS_N of the busbar of the inverter circuit 140 and the output end of the second phase circuit 142 are connected in reverse series.

[0110] In actual implementation, a sixth power tube Q is provided between the neutral point BUS_N of the busbar of the inverter circuit 140 and the output end of the second phase circuit 142. B2 With the seventh power tube Q B3 , the sixth power tube Q B2 With the seventh power tube Q B3 Reverse series connection, the sixth power tube Q B2 The seventh power tube Q is not connected B3 One end of the seventh power tube Q B3 The sixth power tube Q is not connected B2 One end of the fifth power tube Q can be connected to the neutral point BUS_N of the busbar of the inverter circuit 140. B1 With the eighth power tube Q B4 Forward series connection, the fifth power tube Q B1 With the eighth power tube Q B4 The connection point of the fifth power tube Q is the output end of the second phase circuit 142. B1 The end not connected to the output end of the second phase circuit 142 can be connected to the positive electrode of the DC input source 110. B4 The end not connected to the output end of the second phase circuit 142 can be connected to the negative electrode of the DC input source 110. B1 、The sixth power tube Q B2 、The seventh power tube Q B3And the eighth power tube Q B4 Based on the above connection relationship, a three-level T-type structure can be formed.

[0111] The second driving control unit is respectively connected to the fifth power tube Q B1 、The sixth power tube Q B2 、The seventh power tube Q B3 And the eighth power tube Q B4 connected to control the fifth power tube Q based on the operating mode of the inverter 100 B1 、The sixth power tube Q B2 、The seventh power tube Q B3 And the eighth power tube Q B4 .

[0112] In actual implementation, the second drive control unit is respectively connected to the fifth power tube Q B1 、The sixth power tube Q B2 、The seventh power tube Q B3 And the eighth power tube Q B4 The second driving control unit can generate a control signal corresponding to the operating mode based on the operating mode of the inverter 100 to control the fifth power tube Q B1 、The sixth power tube Q B2 、The seventh power tube Q B3 And the eighth power tube Q B4 After the DC voltage input to the second phase circuit 142 is converted into an AC voltage, the AC voltage is output from the output end of the second phase circuit 142 .

[0113] According to the inverter provided in the embodiment of the present application, after the sixth power tube and the seventh power tube are connected in reverse series, they are connected to the connection point where the fifth power tube and the eighth power tube are connected in forward series, forming a second phase circuit of a three-level T-type structure, which can reduce the voltage stress on the input side of the second phase circuit and can more effectively suppress the harmonics of the output voltage.

[0114] In some embodiments, the third phase circuit 143 includes: a ninth power tube Q C1 、The tenth power tube Q C2 , Eleventh power tube Q C3 , the twelfth power tube Q C4 and a third drive control unit.

[0115] In actual implementation, the four power tubes included in the third phase circuit 143 may be: the ninth power tube Q C1 、The tenth power tube Q C2 , Eleventh power tube Q C3 , the twelfth power tube Q C4 The third phase circuit 143 includes a driving control unit which is a third driving control unit ( Figures 1 to 7 not shown).

[0116] The ninth power tube Q C1 With the twelfth power tube Q C4 Forward series connection; the ninth power tube Q C1 With the twelfth power tube Q C4 One end connected is used as the output end of the third phase circuit 143; the tenth power tube Q C2 With the eleventh power tube Q C3 The inverter circuit 140 is connected in reverse series to connect the neutral point BUS_N of the busbar and the output end of the third phase circuit 143 .

[0117] In actual implementation, a tenth power tube Q is provided between the neutral point BUS_N of the busbar of the inverter circuit 140 and the output end of the third phase circuit 143. C2 With the eleventh power tube Q C3 , the tenth power tube Q C2 With the eleventh power tube Q C3 Reverse series connection, the tenth power tube Q C2 The eleventh power tube Q is not connected C3 One end of the eleventh power tube Q C3 The tenth power tube Q is not connected C2 One end of the ninth power tube Q can be connected to the neutral point BUS_N of the busbar of the inverter circuit 140. C1 With the twelfth power tube Q C4 Forward series connection, the ninth power tube Q C1 With the twelfth power tube Q C4 The connection point is the output end of the third phase circuit 143, and the ninth power tube Q C1 The end not connected to the output end of the third phase circuit 143 can be connected to the positive electrode of the DC input source 110. C4 The end not connected to the output end of the third phase circuit 143 can be connected to the negative electrode of the DC input source 110. C1 、The tenth power tube Q C2 , Eleventh power tube Q C3 , the twelfth power tube Q C4 Based on the above connection relationship, a three-level T-type structure can be formed.

[0118] The third driving control unit is respectively connected to the ninth power tube Q C1 、The tenth power tube Q C2 , Eleventh power tube Q C3 And the twelfth power tube Q C4 connected to control the ninth power tube Q based on the operating mode of the inverter 100 C1 、The tenth power tube Q C2 , Eleventh power tube QC3 And the twelfth power tube Q C4 .

[0119] In actual implementation, the third drive control unit is respectively connected to the ninth power tube Q C1 、The tenth power tube Q C2 , Eleventh power tube Q C3 And the twelfth power tube Q C4 The third driving control unit can generate a control signal corresponding to the operating mode based on the operating mode of the inverter 100 to control the ninth power tube Q C1 、The tenth power tube Q C2 , Eleventh power tube Q C3 And the twelfth power tube Q C4 After the DC voltage input to the third phase circuit 143 is converted into an AC voltage, the AC voltage is output from the output end of the third phase circuit 143 .

[0120] According to the inverter provided in the embodiment of the present application, after the tenth power tube and the eleventh power tube are connected in reverse series, they are connected to the connection point where the ninth power tube and the twelfth power tube are connected in forward series, forming a third phase circuit of a three-level T-type structure, which can reduce the voltage stress on the input side of the third phase circuit and can more effectively suppress the harmonics of the output voltage.

[0121] In some embodiments, when the operation mode of the inverter 100 is the three-phase grid-connected mode, the first switch unit K1 is closed, the second switch unit K2 is closed, the third switch unit K3 is closed, and the fourth switch unit K4 is closed or open.

[0122] Figure 2 FIG. 1 is one of the schematic diagrams of the operating state of the inverter provided in the embodiment of the present application. In actual implementation, the operating state of the inverter 100 in the three-phase grid-connected mode can be as follows: Figure 2 In the three-phase grid-connected mode, the three output terminals of the inverter 100 can be connected to one phase of the grid respectively. The first output terminal of the inverter 100 can be connected to the A phase of the grid ( Figure 2 China-Israel grid_A The second output terminal of the inverter 100 can be connected to the B phase of the power grid ( Figure 2 China-Israel grid_B The third output terminal of the inverter 100 can be connected to the C phase ( Figure 2 China-Israel grid_C ), the third switch unit K3 is closed; and the fourth switch unit K4 is open.

[0123] It should be noted that Figure 2The figure shows the operating state of the inverter 100 in the three-phase grid-connected mode when the inverter 100 adopts the three-phase three-wire system. When the inverter 100 adopts the three-phase three-wire system, the fourth switch unit K4 of the inverter 100 in the three-phase grid-connected mode is disconnected. In some embodiments, when the inverter 100 adopts the three-phase four-wire system, the fourth switch unit K4 of the inverter 100 in the three-phase grid-connected mode is closed.

[0124] In some embodiments, when the operation mode of the inverter 100 is the three-phase off-grid mode, the first switch unit K1 is closed, the second switch unit K2 is closed, the third switch unit K3 is closed, and the fourth switch unit K4 is closed.

[0125] Figure 3 FIG. 2 is a second schematic diagram of the operating state of the inverter provided in the embodiment of the present application. In actual implementation, the operating state of the inverter 100 in the three-phase off-grid mode can be as follows: Figure 3 In the three-phase off-grid mode, the three output terminals of the inverter 100 can be connected to the impedance of one phase respectively. The first output terminal of the inverter 100 can be connected to the impedance of the A phase ( Figure 3 China-Israel A The second output terminal of the inverter 100 can be connected to the impedance of the B phase ( Figure 3 China-Israel B The third output terminal of the inverter 100 can be connected to the impedance of the C phase ( Figure 3 China-Israel C (indicates) connection, the third switch unit K3 is closed; the fourth switch unit K4 is closed.

[0126] In some embodiments, when the operation mode of the inverter 100 is the split-phase grid-connected mode, the first switch unit K1 is closed, the second switch unit K2 is closed, the third switch unit K3 is opened, and the fourth switch unit K4 is closed or opened.

[0127] Figure 4 FIG. 3 is a schematic diagram of the operating state of the inverter provided in the embodiment of the present application. In actual implementation, the operating state of the inverter 100 in the split-phase grid-connected mode can be as follows: Figure 4 In the split-phase grid-connected mode, two of the three output terminals of the inverter 100 can be connected to one phase of the grid respectively. The first output terminal of the inverter 100 can be connected to the L1 phase of the grid ( Figure 4 China-Israel grid_L1 The second output terminal of the inverter 100 can be connected to the L2 phase of the power grid ( Figure 4 China-Israel grid_L2(indicates) connection, the second switch unit K2 is closed; the third output terminal of the inverter 100 can be suspended, the third switch unit K3 is disconnected; the fourth switch unit K4 is disconnected.

[0128] It should be noted that Figure 4 The figure shows the operating state of the inverter 100 in the split-phase grid-connected mode when the inverter 100 adopts the split-phase two-wire system. When the inverter 100 adopts the split-phase two-wire system, the fourth switch unit K4 of the inverter 100 is disconnected in the split-phase grid-connected mode. In some embodiments, when the inverter 100 adopts the split-phase three-wire system, the fourth switch unit K4 of the inverter 100 in the split-phase grid-connected mode is closed.

[0129] In some embodiments, when the operation mode of the inverter 100 is the split-phase off-grid mode, the first switch unit K1 is closed, the second switch unit K2 is closed, the third switch unit K3 is opened, and the fourth switch unit K4 is closed.

[0130] Figure 5 FIG. 4 is a schematic diagram of the operating state of the inverter provided in the embodiment of the present application. In actual implementation, the operating state of the inverter 100 in the split-phase off-grid mode can be as follows: Figure 5 In the split-phase off-grid mode, two of the three output terminals of the inverter 100 can be connected to the impedance of one phase respectively. The first output terminal of the inverter 100 can be connected to the impedance of the L1 phase ( Figure 5 China-Israel L1 The first switch unit K1 is closed; the second output terminal of the inverter 100 can be connected to the impedance of the L2 phase ( Figure 5 China-Israel L2 The third output terminal of the inverter 100 can be suspended, the third switch unit K3 is disconnected, and the fourth switch unit K4 is closed.

[0131] In some embodiments, when the operation mode of the inverter 100 is the single-phase grid-connected mode, the first switch unit K1 is closed, the second switch unit K2 is closed, the third switch unit K3 is opened, and the fourth switch unit K4 is opened.

[0132] Figure 6 FIG. 5 is a fifth schematic diagram of the operating state of the inverter provided in the embodiment of the present application. In actual implementation, the operating state of the inverter 100 in the single-phase grid-connected mode can be as follows: Figure 6 In the single-phase grid-connected mode, two of the three output terminals of the inverter 100 can be connected to the grid to form a loop. The first output terminal of the inverter 100 can be connected to the L phase ( Figure 6 China-Israel grid_LThe second output terminal of the inverter 100 can be connected to the L phase ( Figure 6 China-Israel grid_L The other end of the inverter 100 is connected, the second switch unit K2 is closed; the third output end of the inverter 100 can be suspended, the third switch unit K3 is disconnected; the fourth switch unit K4 is disconnected.

[0133] In some embodiments, when the operation mode of the inverter 100 is the single-phase off-grid mode, the first switch unit K1 is closed, the second switch unit K2 is closed, the third switch unit K3 is opened, and the fourth switch unit K4 is opened.

[0134] Figure 7 FIG. 6 is a sixth schematic diagram of the operating state of the inverter provided in the embodiment of the present application. In actual implementation, the operating state of the inverter 100 in the single-phase off-grid mode can be as follows: Figure 7 In the single-phase off-grid mode, two of the three output terminals of the inverter 100 can be connected to the two ends of the single-phase impedance respectively. The first output terminal of the inverter 100 can be connected to the L-phase impedance ( Figure 7 China-Israel L The first switch unit K1 is closed; the second output terminal of the inverter 100 can be connected to the impedance of the L phase ( Figure 7 China-Israel L The other end of the inverter 100 is connected, the second switch unit K2 is closed; the third output end of the inverter 100 can be suspended, the third switch unit K3 is disconnected; the fourth switch unit K4 is disconnected.

[0135] According to the inverter provided in the embodiment of the present application, switching between three-phase output, split-phase output and single-phase output can be achieved only by controlling the opening and closing states of each switch unit included in the switch module according to the operating mode of the inverter. There is no need to change the wiring method of the inverter or the wiring of the single board. Switching between three-phase output, split-phase output and single-phase output is simpler and more convenient.

[0136] In some embodiments, Figures 1 to 7 As shown, the voltage equalizing circuit 120 includes: a first switch tube Q1, a second switch tube Q2 and an inductor L1.

[0137] In actual implementation, the voltage balancing circuit 120 may be composed of two switch tubes connected in series and an inductor. The two switch tubes may be: a first switch tube Q1 and a second switch tube Q2. The inductor may be an inductor L1.

[0138] In some embodiments, each of the above-mentioned switching tubes can be formed by connecting a diode and a switching device in parallel.

[0139] The first switch tube Q1 is connected in series with the second switch tube Q2; the first end of the inductor L1 is connected to one end of the first switch tube Q1 connected to the second switch tube Q2; the second end of the inductor L1, as the output end of the voltage equalizing circuit 120, is connected to the neutral point BUS_N of the busbar of the inverter circuit 140.

[0140] In actual implementation, the first switch tube Q1 is connected in series with the second switch tube Q2. From the connection point between the first switch tube Q1 and the second switch tube Q2, the output end of the voltage balancing circuit 120 can be led out through the inductor L1. The output end of the voltage balancing circuit 120 can be connected to the neutral point BUS_N of the busbar of the inverter circuit 140. Based on the above connection relationship, the first switch tube Q1, the second switch tube Q2 and the inductor L1 can form a balanced bridge circuit.

[0141] According to the inverter provided in the embodiment of the present application, the first switch tube and the second switch tube are connected in series, and the inductor connects the connection point between the first switch tube and the second switch tube and the neutral point of the bus of the inverter circuit to form a voltage equalizing circuit including a balancing bridge, which can more effectively balance the voltage of the two groups of capacitors included in the DC bus capacitor.

[0142] In some embodiments, each group of capacitors in the DC bus capacitor 130 includes: one capacitor or multiple capacitors connected in parallel.

[0143] In actual implementation, any group of capacitors included in the DC bus capacitor 130 can be represented as a connecting capacitor.

[0144] like Figures 1 to 7 As shown, the two groups of capacitors can be represented by connecting capacitors C1 and C2 respectively, that is, the connecting capacitors C1 and C2 can each include a group of capacitors. The above group of capacitors can include at least one capacitor.

[0145] In some embodiments, any group of capacitors (connecting capacitors C1 or C2) included in the DC bus capacitor 130 may be composed of one capacitor, or any group of capacitors (connecting capacitors C1 or C2) included in the DC bus capacitor 130 may also be composed of multiple capacitors. In the case where any group of capacitors (connecting capacitors C1 or C2) included in the DC bus capacitor 130 is composed of multiple capacitors, the multiple capacitors constituting the group of capacitors are connected in parallel.

[0146] According to the inverter provided in the embodiment of the present application, any group of capacitors included in the DC bus capacitor formed by one capacitor or multiple capacitors in parallel can more effectively stabilize the bus voltage of the inverter circuit and more effectively suppress voltage ripple.

[0147] In some embodiments, Figures 1 to 7 As shown, the inverter 100 further includes: a filter circuit 160; the filter circuit 160 includes a first filter unit, a second filter unit and a third filter unit.

[0148] In actual implementation, a filter circuit 160 may be provided between the inverter circuit 140 and the switch module 150. The filter circuit 160 may be used to filter the output of the inverter circuit 140.

[0149] Corresponding to the three parts of the inverter circuit 140 , the filter circuit 160 may also include three parts: a first filter unit, a second filter unit and a third filter unit. The three parts of the filter circuit 160 correspond to the three parts of the inverter circuit 140 one by one.

[0150] The input end of the first filter unit is connected to the output end of the first phase circuit 141 , and the output end of the first filter unit is connected to the first end of the first switch unit K1 , so as to filter the AC voltage output by the first phase circuit 141 .

[0151] In actual implementation, the first filter unit may correspond to the first phase circuit 141. The function of the first filter unit may be to filter the AC voltage output by the first phase circuit 141. Therefore, the input end of the first filter unit may be connected to the output end of the first phase circuit 141, and the output end of the first filter unit may be connected to the first end of the first switch unit K1.

[0152] The input end of the second filter unit is connected to the output end of the second phase circuit 142 , and the output end of the second filter unit is connected to the first end of the second switch unit K2 , so as to filter the AC voltage output by the second phase circuit 142 .

[0153] In actual implementation, the second filtering unit may correspond to the second phase circuit 142. The function of the second filtering unit may be to filter the AC voltage output by the second phase circuit 142. Therefore, the input end of the second filtering unit may be connected to the output end of the second phase circuit 142, and the output end of the second filtering unit may be connected to the first end of the second switch unit K2.

[0154] The input end of the third filter unit is connected to the output end of the third phase circuit 143 , and the output end of the third filter unit is connected to the first end of the third switch unit K3 , so as to filter the AC voltage output by the third phase circuit 143 .

[0155] In actual implementation, the third filter unit may correspond to the third phase circuit 143. The function of the third filter unit may be to filter the AC voltage output by the third phase circuit 143. Therefore, the input end of the third filter unit may be connected to the output end of the third phase circuit 143, and the output end of the third filter unit may be connected to the first end of the third switch unit K3.

[0156] According to the inverter provided in the embodiment of the present application, by setting a filter circuit to filter the output of the inverter circuit, the noise in the output of the inverter can be effectively removed, making the output signal more stable and pure.

[0157] In some embodiments, the first filter unit, the second filter unit and the third filter unit are all LC filters.

[0158] In actual implementation, the first filtering unit, the second filtering unit and the third filtering unit may all adopt LC filters.

[0159] In some embodiments, Figures 1 to 7 As shown, the first filtering unit may include a series inductor L A And the parallel capacitor C A The AC voltage output by the first phase circuit 141 can be sequentially passed through L A And filter capacitor C A The second filtering unit may include an inductor L connected in series. B And the parallel capacitor C B The AC voltage output by the second phase circuit 142 can be sequentially passed through L B And filter capacitor C B The third filtering unit may include an inductor L connected in series. C And the parallel capacitor C C The AC voltage output by the third phase circuit 143 can be sequentially transmitted through L C And filter capacitor C C Perform filtering.

[0160] According to the inverter provided in the embodiment of the present application, by using LC filters in the first filter unit, the second filter unit and the third filter unit, noise in the output of the inverter can be more effectively removed, making the output signal more stable and pure.

[0161] In some embodiments, inverter 100 is a photovoltaic inverter.

[0162] In order to facilitate the understanding of the above embodiments of the present application, Figure 8 and Fig. 9 The operation of the inverter provided in any of the above embodiments is described.

[0163] Figure 8 This is one of the schematic diagrams of the wave generation mode of the inverter operation provided in the embodiment of the present application. Figure 8 The three-phase wave generation mode shown in the figure has a phase shift of 120°, generates a control signal, and drives Figure 2 or Figure 3The inverter 100 shown in the figure realizes three-phase operation. The inverter 100 can adopt both three-phase three-wire and three-phase four-wire wiring methods. The control signal and the output waveform of each power tube included in the inverter circuit 140 can be as follows: Figure 8 shown.

[0164] For Figure 3 The inverter 100 shown in the figure has an operating mode of a three-phase off-grid mode, and the fourth switch unit K4 is closed. If the voltage balancing circuit 120 is not provided, the unbalanced three-phase load will cause the connection capacitors C1 and C2 of the DC bus capacitor to be unbalanced, resulting in overvoltage damage to a certain connection capacitor, causing the inverter to fail to operate. By providing the voltage balancing circuit 120, the voltages of the connection capacitors C1 and C2 can be balanced in the three-phase output scenario of off-grid operation with an unbalanced load to avoid damage to the connection capacitors, so that the inverter 100 can operate normally in the three-phase output scenario of off-grid operation with an unbalanced load, and thus can realize the switching between three-phase output and single-phase output in the three-phase output scenario of off-grid operation with an unbalanced load.

[0165] Fig. 9 This is a second schematic diagram of the wave generation mode of the inverter operation provided in the embodiment of the present application. Fig. 9 As shown, it can be Fig. 9 The two-phase wave generation mode shown in the figure has a phase shift of 120°, which generates a control signal to drive the Figures 4 to 7 Any of the inverters 100 shown can realize single-phase operation. The control signal and the output waveform of each power tube included in the inverter circuit 140 can be as follows: Fig. 9 shown.

[0166] For Figure 5 The inverter 100 shown in the figure has an operation mode of a split-phase off-grid mode, and the fourth switch unit K4 is closed. If the voltage balancing circuit 120 is not provided, the unbalanced three-phase load will cause the connection capacitors C1 and C2 of the DC bus capacitor to be unbalanced, resulting in overvoltage damage to a certain connection capacitor, causing the inverter to fail to operate. By providing the voltage balancing circuit 120, the voltages of the connection capacitors C1 and C2 can be balanced in the three-phase output scenario of off-grid operation with an unbalanced load to avoid damage to the connection capacitors, so that the inverter 100 can operate normally in the three-phase output scenario of off-grid operation with an unbalanced load, and thus can realize the switching between three-phase output and single-phase output in the three-phase output scenario of off-grid operation with an unbalanced load.

[0167] The present application also provides a photovoltaic system, including: an inverter 100 provided by any of the above inverter embodiments.

[0168] In actual implementation, the photovoltaic system may use the inverter 100 provided in any of the above embodiments to perform inversion processing on the output of the photovoltaic panel.

[0169] According to the system provided in the embodiment of the present application, switching among three-phase operation, split-phase operation and single-phase operation is realized for different systems, and three-phase operation, split-phase operation and single-phase operation can be realized in different grid-connected and off-grid scenarios.

[0170] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0171] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. An inverter, characterized in that: include: A DC input source, a voltage balancing circuit, a DC bus capacitor, an inverter circuit and a switch module; the DC input source passes through the voltage balancing circuit and the DC bus capacitor in sequence and is connected to the inverter circuit; The DC bus capacitor includes two sets of capacitors connected in series; The voltage equalizing circuit adopts a balanced bridge circuit; The inverter circuit comprises a first phase circuit, a second phase circuit and a third phase circuit; the first phase circuit, the second phase circuit and the third phase circuit all adopt a three-level T-type structure; The switch module includes a first switch unit, a second switch unit, a third switch unit and a fourth switch unit; The first end of the first switch unit is connected to the output end of the first phase circuit, and the second end of the first switch unit serves as the first output end of the inverter; The first end of the second switch unit is connected to the output end of the second phase circuit, and the second end of the second switch unit serves as the second output end of the inverter; The first end of the third switch unit is connected to the output end of the third phase circuit, and the second end of the third switch unit serves as the third output end of the inverter; The first end of the fourth switch unit is connected to the neutral point of the busbar of the inverter circuit, and the second end of the fourth switch unit serves as the fourth end of the inverter; The on / off states of the first switch unit, the second switch unit, the third switch unit, and the fourth switch unit correspond to the operation mode of the inverter.

2. The inverter according to claim 1, characterized in that: The first phase circuit includes: a first power tube, a second power tube, a third power tube, a fourth power tube and a first driving control unit; The first power tube is connected in series with the fourth power tube in a forward direction; one end of the first power tube connected with the fourth power tube serves as the output end of the first phase circuit; the second power tube is connected in series with the third power tube in a reverse direction, connecting the neutral point of the busbar of the inverter circuit and the output end of the first phase circuit; The first drive control unit is connected to the first power tube, the second power tube, the third power tube and the fourth power tube respectively to control the first power tube, the second power tube, the third power tube and the fourth power tube based on the operation mode of the inverter.

3. The inverter according to claim 1, characterized in that: The second phase circuit includes: a fifth power tube, a sixth power tube, a seventh power tube, an eighth power tube and a second drive control unit; The fifth power tube is connected in series with the eighth power tube in a forward direction; one end of the fifth power tube connected to the eighth power tube serves as the output end of the second phase circuit; the sixth power tube is connected in series with the seventh power tube in a reverse direction, connecting the neutral point of the busbar of the inverter circuit and the output end of the second phase circuit; The second drive control unit is connected to the fifth power tube, the sixth power tube, the seventh power tube and the eighth power tube respectively to control the fifth power tube, the sixth power tube, the seventh power tube and the eighth power tube based on the operation mode of the inverter.

4. The inverter according to claim 1, characterized in that: The third phase circuit includes: a ninth power tube, a tenth power tube, an eleventh power tube, a twelfth power tube and a third driving control unit; The ninth power tube is connected in series with the twelfth power tube in a forward direction; one end of the ninth power tube connected with the twelfth power tube serves as the output end of the third phase circuit; the tenth power tube is connected in series with the eleventh power tube in a reverse direction, connecting the neutral point of the busbar of the inverter circuit and the output end of the third phase circuit; The third driving control unit is connected to the ninth power tube, the tenth power tube, the eleventh power tube and the twelfth power tube respectively to control the ninth power tube, the tenth power tube, the eleventh power tube and the twelfth power tube based on the operation mode of the inverter.

5. The inverter according to claim 1, characterized in that: When the operation mode of the inverter is the three-phase grid-connected mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is closed, and the fourth switch unit is closed or opened; When the operation mode of the inverter is the three-phase off-grid mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is closed, and the fourth switch unit is closed.

6. The inverter according to claim 1, characterized in that: When the operation mode of the inverter is the split-phase grid-connected mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is closed or opened; When the operation mode of the inverter is the split-phase off-grid mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is closed.

7. The inverter according to claim 1, characterized in that: When the operation mode of the inverter is the single-phase grid-connected mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is opened; When the operation mode of the inverter is the single-phase off-grid mode, the first switch unit is closed, the second switch unit is closed, the third switch unit is opened, and the fourth switch unit is opened.

8. The inverter according to claim 1, characterized in that: The voltage balancing circuit comprises: a first switch tube, a second switch tube and an inductor; The first switch tube is connected in series with the second switch tube; the first end of the inductor is connected to one end of the first switch tube connected to the second switch tube; the second end of the inductor, as the output end of the voltage balancing circuit, is connected to the neutral point of the busbar of the inverter circuit.

9. The inverter according to claim 1, characterized in that: Each group of capacitors in the DC bus capacitors includes: one capacitor or a plurality of capacitors connected in parallel.

10. The inverter according to any one of claims 1 to 9, characterized in that: Also includes: Filter circuit; The filtering circuit comprises a first filtering unit, a second filtering unit and a third filtering unit; The input end of the first filtering unit is connected to the output end of the first phase circuit, and the output end of the first filtering unit is connected to the first end of the first switch unit, so as to filter the AC voltage output by the first phase circuit; The input end of the second filtering unit is connected to the output end of the second phase circuit, and the output end of the second filtering unit is connected to the first end of the second switch unit, so as to filter the AC voltage output by the second phase circuit; The input end of the third filtering unit is connected to the output end of the third phase circuit, and the output end of the third filtering unit is connected to the first end of the third switch unit to filter the AC voltage output by the third phase circuit.

11. The inverter according to claim 10, characterized in that: The first filtering unit, the second filtering unit and the third filtering unit are all LC filters.

12. The inverter according to claim 1, characterized in that: The inverter is a photovoltaic inverter.

13. A photovoltaic system, characterized in that: include: An inverter as claimed in any one of claims 1 to 12.

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