Inverter unit

Abstract

The utility model discloses an inversion unit, and belongs to the technical field of electrics. The inversion unit comprises a control module, at least two conversion branches, a transformer and a secondary side bridge arm. Wherein the input ends of the conversion branches are respectively used as the input ends of the inversion unit and are connected with a direct current source or a load, the output ends of the conversion branches are sequentially cascaded and then are connected with the input end of the transformer through an excitation inductor of the transformer, and the output end of the transformer is connected with the input end of the secondary side bridge arm. The output end of the secondary side bridge arm is used as the output end of the inversion unit; and the control module is connected with each conversion branch and is used for controlling each conversion branch. According to the inverter unit disclosed by the invention, the output ends of the conversion branches are sequentially cascaded and then are connected with the input end of the transformer through the excitation inductor of the transformer, so that primary inductance is reduced, the conversion efficiency of the inverter unit can be improved, and the number of used magnetic parts can be reduced; therefore, the overall size of the inversion unit can be reduced, and the cost and heating of the inversion unit can be reduced.

Description

Technical Field

[0001] This application belongs to the field of power technology, and particularly relates to an inverter unit. Background Art

[0002] In a photovoltaic energy storage system, the voltage of a DC source or battery (PV / Battery) fluctuates to a certain extent. To suppress the fluctuations and ensure the stable operation of the photovoltaic energy storage system, it is necessary to convert the voltage of the PV / Battery into a stable DC voltage through DC / DC (Direct Current / Direct Current) conversion, and then perform isolated inversion and grid connection.

[0003] The above DC / DC conversion and isolated inversion and grid connection are generally achieved through the inverter unit of the photovoltaic energy storage system. All kinds of DC / DC conversions require the use of inductors, and the subsequent isolated inversion requires the use of transformers. The large number of magnetic components used results in a larger overall size, higher cost, and limited efficiency of the inverter unit and even the entire photovoltaic energy storage system.

[0004] For example, Figure 1 and Figure 2 show the structure of an inverter unit of an existing photovoltaic energy storage system. As Figure 2 shown, two Converters located on the primary side of the transformer and connected to the DC source or battery (PV / Battery) are each provided with an inductor. Through the cooperation of the three Converters on the primary side of the transformer, DC / DC conversion is performed, and the transformer itself is an inductor component. Therefore, the entire inverter unit requires the use of a relatively large number of magnetic components. Summary of the Utility Model

[0005] This application aims to solve at least one of the technical problems existing in the prior art. For this purpose, this application proposes an inverter unit that can improve the conversion efficiency of the inverter unit and the photovoltaic energy storage system.

[0006] This application provides an inverter unit, which includes: a control module, at least two conversion branches, a transformer, and a secondary side bridge arm;

[0007] Wherein, the input ends of each of the conversion branches are respectively used as the input ends of the inverter unit and are connected to a DC source or a load. The output ends of each of the conversion branches are cascaded in sequence and then connected to the input end of the transformer through the exciting inductor of the transformer. The output end of the transformer is connected to the input end of the secondary side bridge arm, and the output end of the secondary side bridge arm is used as the output end of the inverter unit;

[0008] The control module is connected to each of the conversion branches and is used to control each of the conversion branches.

[0009] The inverter unit according to the present application has the input ends of the respective conversion branches serving as the respective input ends of the inverter unit and being connected to a DC source or a load. The output ends of the respective conversion branches are cascaded in sequence and then connected to the input end of a transformer through the exciting inductance of the transformer. Only an inductor is provided in the transformer, and no inductor needs to be provided in the conversion branches, which can reduce one stage of inductors. The voltage of PV / Battery can be converted into a stable DC voltage only through one-stage DC / DC conversion, which can improve the efficiency of the DC / DC conversion of the inverter unit, reduce the number of magnetic components used in the inverter unit, and thus can reduce the overall volume of the inverter unit and lower the cost and heat generation of the inverter unit.

[0010] According to an embodiment of the present application, the conversion branch includes a first H-bridge circuit.

[0011] According to an embodiment of the present application, at least two conversion branches include a first conversion branch and a second conversion branch;

[0012] Wherein, the first conversion branch includes a first switch tube, a second switch tube, a third switch tube, and a fourth switch tube, and the second conversion branch includes a fifth switch tube, a sixth switch tube, a seventh switch tube, and an eighth switch tube;

[0013] The first end of the first switch tube is connected to the first end of the second switch tube and then connected to the DC source. The second end of the first switch tube is connected to the first end of the third switch tube. The second end of the second switch tube and the first end of the fourth switch tube are connected. The second end of the third switch tube and the second end of the fourth switch tube are connected and then connected to the DC source. The second end of the first switch tube is connected to the input end of the transformer through the exciting inductance;

[0014] The first end of the fifth switch tube is connected to the first end of the sixth switch tube and then connected to the load. The second end of the fifth switch tube is connected to the first end of the seventh switch tube. The second end of the sixth switch tube and the first end of the eighth switch tube are connected. The second end of the seventh switch tube and the second end of the eighth switch tube are connected and then connected to the load. The first end of the eighth switch tube is connected to the input end of the transformer through the exciting inductance;

[0015] The first end of the fourth switch tube is connected to the second end of the fifth switch tube.

[0016] According to an embodiment of the present application, the control module is respectively connected to the first conversion branch and the second conversion branch, and is further configured to:

[0017] Control the second switch tube to be in a normally closed state;

[0018] Control the fourth switch tube to be in a normally on state;

[0019] Control the fifth switching tube to be in a normally closed state;

[0020] Control the seventh switching tube to be in a normally on state.

[0021] According to an embodiment of the present application, the control module is further configured to:

[0022] Control the sixth switching tube to be in a normally on state;

[0023] Control the eighth switching tube to be in a normally closed state.

[0024] According to an embodiment of the present application, the control module is further configured to:

[0025] Control the first switching tube to be in a normally on state;

[0026] Control the third switching tube to be in a normally closed state.

[0027] According to an embodiment of the present application, the secondary side bridge arm includes: a first branch, a second branch, a first capacitor, and a third branch;

[0028] Wherein, the output terminal of the transformer is respectively connected to the input terminal of the first branch and the input terminal of the second branch, the output terminal of the first branch is connected to the input terminal of the second branch, the output terminal of the second branch is connected to the input terminal of the third branch through the first capacitor, and the output terminal of the third branch is used as the output terminal of the inverter unit;

[0029] The first branch includes a first module or a second module, the first module includes a first inductor, and the second module includes the first inductor and a second capacitor connected in series.

[0030] According to an embodiment of the present application, the second branch includes a second H-bridge circuit, and the third branch includes a third H-bridge circuit.

[0031] According to an embodiment of the present application, when the first branch includes the first module, the second branch includes:

[0032] A ninth switching tube, a tenth switching tube, a third capacitor, and a fourth capacitor;

[0033] The output terminals of the transformer are respectively connected to the input terminal of the first inductor and the first connection point. The second terminal of the ninth switching transistor is respectively connected to the output terminal of the first inductor and the first terminal of the tenth switching transistor. The first terminal of the ninth switching transistor is connected to the first terminal of the third capacitor. The second terminal of the third capacitor is connected to the first terminal of the fourth capacitor. The second terminal of the fourth capacitor is connected to the second terminal of the tenth switching transistor. The first connection point is located between the second terminal of the third capacitor and the first terminal of the fourth capacitor.

[0034] According to an embodiment of the present application, the secondary side bridge arm includes: a fourth branch and a fifth branch;

[0035] Wherein, the fourth branch includes a second inductor and a fifth capacitor connected in series;

[0036] The fifth branch includes an eleventh switching transistor, a twelfth switching transistor, a thirteenth switching transistor, and a fourteenth switching transistor. The output terminals of the transformer are respectively connected to the input terminal of the fourth branch and the second connection point. The output terminal of the fourth branch is connected to the third connection point. The second terminal of the eleventh switching transistor is connected to the second terminal of the twelfth switching transistor. The second terminal of the thirteenth switching transistor is connected to the second terminal of the fourteenth switching transistor. The first terminal of the twelfth switching transistor is connected to the first terminal of the thirteenth switching transistor. The first terminals of the eleventh switching transistor and the fourteenth switching transistor serve as the output terminals of the inverter unit. The second connection point is located between the second terminal of the thirteenth switching transistor and the second terminal of the fourteenth switching transistor, or the second connection point is determined according to the first terminal of the fourteenth switching transistor. The third connection point is located between the second terminal of the eleventh switching transistor and the second terminal of the twelfth switching transistor, or the third connection point is located between the first terminal of the twelfth switching transistor and the first terminal of the thirteenth switching transistor.

[0037] According to an embodiment of the present application, the secondary side bridge arm includes: a third inductor, a sixth branch, a sixth capacitor, and a seventh capacitor;

[0038] Among them, the sixth branch includes a fifteenth switching tube, a sixteenth switching tube, a seventeenth switching tube, and an eighteenth switching tube. The output end of the transformer is respectively connected to the input end of the third inductor and the first end of the seventeenth switching tube. The output end of the third inductor is connected to a fourth connection point. The second end of the fifteenth switching tube is connected to the second end of the sixteenth switching tube. The first end of the fifteenth switching tube is connected to the first end of the sixth capacitor. The second end of the sixth capacitor is connected to the first end of the seventh capacitor. The first end of the sixteenth switching tube is connected to the first end of the seventeenth switching tube. The second end of the seventeenth switching tube is connected to the second end of the eighteenth switching tube. The first end of the eighteenth switching tube is connected to the second end of the seventh capacitor. The fourth connection point is located between the second end of the sixth capacitor and the first end of the seventh capacitor.

[0039] According to an embodiment of the present application, the inverter unit further includes: a filter;

[0040] Among them, the filter is connected to the output end of the secondary side bridge arm.

[0041] According to an embodiment of the present application, the input ends of each of the conversion branches are respectively connected to a photovoltaic module or an energy storage device.

[0042] The additional aspects and advantages of the present application will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and / or additional aspects and advantages of the present application will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0044] Figure 1 is one of the schematic structural diagrams of the inverter unit in the related art;

[0045] Figure 2 is another schematic structural diagram of the inverter unit in the related art;

[0046] Figure 3 is one of the schematic structural diagrams of the inverter unit provided by the embodiment of the present application;

[0047] Figure 4 is another schematic structural diagram of the inverter unit provided by the embodiment of the present application;

[0048] Figure 5 is the schematic primary side structure diagram of the inverter unit provided by the embodiment of the present application;

[0049] Figure 6 is the schematic diagram of the primary side working state of the inverter unit provided by the embodiment of the present application;

[0050] Figure 7 It is the third structural schematic diagram of the inverter unit provided by the embodiment of the present application;

[0051] Figure 8 It is the fourth structural schematic diagram of the inverter unit provided by the embodiment of the present application;

[0052] Figure 9 It is the fifth structural schematic diagram of the inverter unit provided by the embodiment of the present application;

[0053] Figure 10 It is the sixth structural schematic diagram of the inverter unit provided by the embodiment of the present application;

[0054] Figure 11 It is the seventh structural schematic diagram of the inverter unit provided by the embodiment of the present application;

[0055] Figure 12 It is the eighth structural schematic diagram of the inverter unit provided by the embodiment of the present application. Detailed implementation manners

[0056] Next, the technical solutions in the embodiments of the present application will be clearly described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art belong to the scope protected by the present application.

[0057] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, rather than to describe a specific order or sequence. It should be understood that such used data can be interchanged under appropriate circumstances, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first", "second", etc. generally belong to the same category, and do not limit the number of objects. For example, the first object can be one or multiple. In addition, "and / or" in the specification and claims means at least one of the connected objects, and the character " / " generally represents an "or" relationship between the associated objects.

[0058] In the related art, both PV and Battery are low-voltage and the voltage fluctuates within a certain range. For example, Figure 1 As shown, the inverter unit 100 generally uses a BUCK-BOOST circuit 110 to convert the voltage of PV / Battery into a fixed bus voltage, and then through an isolated DC / AC converter (Converter) located on the secondary side of the transformer ( Figure 1 on the right side of the transformer in the figure) for isolated inversion, and transmits the voltage on the bus to the power grid. The power grid uses alternating current (AC),Figure 1 In the figure, the power grid is represented by AC. In practical applications, the output of the isolated DC / AC converter can be filtered by a grid filter and then input into the power grid.

[0059] Figure 1 In the BUCK-BOOST circuit 110, it mainly consists of three Converters located on the primary side of the transformer ( Figure 1 on the left side of the transformer), and may also include other components such as capacitors. Among the above three Converters, the output terminal of one Converter is connected to the input terminal of the transformer, and the output terminals of the other two Converters are connected to the input terminal of this Converter. The above-mentioned other two Converters are respectively part of a conversion branch, and their input terminals can be connected to PV or Battery.

[0060] The main function of the Converters included in the BUCK-BOOST circuit 110 is to perform DC / DC conversion. Figure 2 Further shows Figure 1 the structures of the three Converters included in the BUCK-BOOST circuit 110. Figure 2 What is shown is the structures of the three Converters based on Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET).

[0061] The above-mentioned inverter unit 100 is completely decoupled in control and the control is simple. However, in the operation of the photovoltaic and energy storage system, from light → storage (i.e., photovoltaic → energy storage), light → power grid (i.e., photovoltaic → power grid), storage → power grid (i.e., energy storage → power grid), and power grid → storage (i.e., power grid → energy storage), etc., all need to go through two magnetic components (two-stage conversion), and the conversion efficiency is relatively low. Moreover, excessive use of magnetic components will also cause certain pressure on the overall machine volume, cost, heat generation, etc., resulting in an increase in the volume of the inverter unit, an increase in cost, and an increase in heat generation.

[0062] Next, in conjunction with the accompanying drawings, the inverter unit provided by the embodiments of the present application will be described in detail through specific embodiments and their application scenarios.

[0063] As Figure 3 shown, an inverter unit 300 includes: a control module 310, at least two conversion branches 320, a transformer 330, and a secondary side bridge arm 340.

[0064] Among them, the input ends of the respective conversion branches 320 are respectively used as the respective input ends of the inverter unit 300 and are connected to a DC source or a load. After the output ends of the respective conversion branches 320 are cascaded in sequence, they are connected to the input end of a transformer 330 through an excitation inductor L of the transformer 330 m and are connected to the input end of the transformer 330. The output end of the transformer 330 is connected to the input end of the secondary side bridge arm 340, and the output end of the secondary side bridge arm 340 is used as the output end of the inverter unit 300.

[0065] A control module 310, connected to the respective conversion branches 320, is configured to control the respective conversion branches 320.

[0066] In actual implementation, the input end of the inverter unit 300 can be connected to a DC source or a load. In a photovoltaic energy storage system, the DC source can be solar photovoltaic (PV, which can be abbreviated as "photovoltaic" for short), and the load can be a storage battery.

[0067] Each input end of the inverter unit 300 can be respectively connected to a DC source or a load. The input end of each conversion branch 320 can all be used as an input end of the inverter unit 300. Therefore, the input end of each conversion branch 320 is connected to a DC source or a load. The function of each conversion branch 320 is to perform DC / DC conversion on the input DC voltage and output a stable (referring to no fluctuation or very small fluctuation, not exceeding a preset threshold) DC voltage.

[0068] Regarding the specific structure of each conversion branch 320, the embodiments of the present application do not make any limitations, as long as it can achieve DC / DC conversion. In some embodiments, any one of the conversion branches 320 can adopt the structure of any Converter in the related art that is not directly connected to the input end of the transformer or other structures.

[0069] In addition to including the basic structure of a normal transformer, the transformer 330 can also have an excitation inductor L added at the input end m . The excitation inductor L of the transformer 330 m can be used as the DC / DC inductor for the PV→Battery (i.e., light→storage) conversion. The output ends of the respective conversion branches 320 are cascaded in sequence and are connected to the input end of the transformer 330 through the excitation inductor L m .

[0070] The output end of the inverter unit 300 can be used to connect to the power grid ( Figure 3 AC is also used to represent the power grid in

[0071] The input end of the secondary bridge arm 340 is connected to the output end of the transformer 330, and the output end of the secondary bridge arm 340 serves as the output end of the inverter unit 300. The secondary bridge arm 340 can be used for isolated inversion. In some embodiments, the secondary bridge arm 340 may include an isolated DC / AC converter or other DC / AC conversion circuits.

[0072] In actual implementation, each conversion branch 320 may include at least one switching tube, and the control module 310 can control the switching states of the switching tubes included in each conversion branch 320, thereby controlling each conversion branch 320. Through the control of each conversion branch 320 by the control module 310, the overall cooperation of each conversion branch 320 and the excitation inductor L of the transformer 330 m can be equivalent to a BUCK - BOOST circuit for DC / DC conversion, satisfying all operating states of PV→Battery.

[0073] All operating states of PV→Battery include: BUCK mode and BOOST mode. When the voltage of PV is higher than the voltage of Battery, the BUCK - BOOST circuit operates in the BUCK mode; when the voltage of PV is lower than the voltage of Battery, the BUCK - BOOST circuit operates in the BOOST mode.

[0074] It should be noted that since the overall cooperation of each conversion branch 320 and the excitation inductor L of the transformer 330 m can be equivalent to a BUCK - BOOST circuit for DC / DC conversion, the part of the transformer 330 other than the excitation inductor L m can implement the functions of a transformer in related technologies, and the secondary bridge arm 340 can be equivalent to an isolated DC / AC converter in related technologies. Therefore, the inverter unit 300 provided in the embodiments of the present application can implement the mechanism in related technologies of converting the voltage of PV / Battery into a stable DC voltage through DC / DC conversion and then performing isolated inversion and grid connection.

[0075] It should be noted that although Figure 3 the illustration shows the case where the inverter unit 300 includes two conversion branches 320, based on Figure 3 this, those skilled in the art can understand the case where the inverter unit 300 includes three or more conversion branches 320. In the case where the inverter unit 300 includes three or more conversion branches 320, any conversion branch 320 with an input end connected to PV, any conversion branch 320 with an input end connected to Battery, and the excitation inductor L of the transformer 330 mWith the overall cooperation, DC / DC conversion can be achieved to convert the voltage of PV / Battery into a stable DC voltage.

[0076] It should be noted that, compared with the related technology, in the light → storage conversion mode, the related technology requires two levels of inductors for two-level DC / DC conversion, which has a greater impact on the conversion efficiency and the conversion efficiency is low. However, for the inverter unit provided in the embodiments of the present application, in the light → storage conversion mode, only an inductor is provided in the transformer, and no inductor needs to be provided in the conversion branch. Only one level of inductor is required for one-level DC / DC conversion, thereby reducing the number of magnetic components and improving the conversion efficiency.

[0077] According to the inverter unit provided in the embodiments of the present application, the input ends of each conversion branch are respectively used as the input ends of the inverter unit and are connected to a DC source or a load. The output ends of each conversion branch are cascaded in sequence and then connected to the input end of the transformer through the exciting inductor of the transformer. Only an inductor is provided in the transformer, and no inductor needs to be provided in the conversion branch. One level of inductor can be reduced, and the voltage of PV / Battery can be converted into a stable DC voltage only through one-level DC / DC conversion, which can improve the efficiency of the inverter unit for DC / DC conversion, reduce the number of magnetic components used in the inverter unit, and thus reduce the overall volume of the inverter unit and lower the cost and heat generation of the inverter unit.

[0078] In some embodiments, the conversion branch 320 includes a first H-bridge circuit.

[0079] In actual implementation, each conversion branch 320 may include an H-bridge circuit. The H-bridge circuit included in the conversion branch 320 may be denoted as the first H-bridge circuit. Since the conversion branch 320 is located on the primary side of the transformer, the first H-bridge circuit is the primary-side H-bridge circuit.

[0080] The H-bridge (H-Bridge) circuit is named because its shape is similar to the letter "H". In some embodiments, the first H-bridge circuit may be composed of 4 triodes to form 4 vertical legs of the letter "H". The function of the triode can be used as a switching tube. The specific type of the triode is not limited in the embodiments of the present application. By opening and closing the switching tube, DC / DC conversion can be performed on the voltage input to the first H-bridge circuit.

[0081] According to the inverter unit provided in the embodiments of the present application, by adopting an H-bridge circuit in the conversion branch, the control is simple, the energy consumption is low, the functions are rich, and the adaptability is strong.

[0082] In some embodiments, as Figure 4 shown, at least two conversion branches 320 include a first conversion branch 410 and a second conversion branch 420.

[0083] In actual implementation, the inverter unit 300 may include two conversion branches 320: a first conversion branch 410 and a second conversion branch 420.

[0084] Among them, the first conversion branch 410 includes a first switching tube S 1-1 , a second switching tube S 1-2 , a third switching tube S 1-3 , and a fourth switching tube S 1-4 . The second conversion branch 420 includes a fifth switching tube S 2-1 , a sixth switching tube S 2-2 , a seventh switching tube S 2-3 , and an eighth switching tube S 2-4 .

[0085] In actual implementation, both the first conversion branch 410 and the second conversion branch 420 may include 4 switching tubes of the same type, forming 4 vertical legs of the letter "H". The 4 switching tubes included in the first conversion branch 410 may be respectively the first switching tube S 1-1 , the second switching tube S 1-2 , the third switching tube S 1-3 , and the fourth switching tube S 1-4 . The 4 switching tubes included in the second conversion branch 420 may be respectively the fifth switching tube S 2-1 , the sixth switching tube S 2-2 , the seventh switching tube S 2-3 , and the eighth switching tube S 2-4 .

[0086] The switching tubes included in the first conversion branch 410 and the second conversion branch 420 may adopt any kind of triode, such as high speed thyristor, gate turn-off thyristor (GTO), power transistor (GTR), MOSFET or insulated gate bipolar transistor (IGBT), etc. MOSFET may adopt vertical metal oxide semiconductor (VMOS), etc.

[0087] The first end of the first switching tube S 1-1 is connected to the first end of the second switching tube S 1-2 and then connected to the DC source. The second end of the first switching tube S 1-1 is connected to the first end of the third switching tube S 1-3 . The second end of the second switching tube S 1-2 and the first end of the fourth switching tube S 1-4 are connected. The third switching tube S1-3 The second end of is connected to the fourth switching transistor S 1-4 After the second end of is connected, it is connected to the DC source. The second end of the first switching transistor S 1-1 is connected to the input end of the transformer 330 through the exciting inductor L m

[0088] In actual implementation, the first conversion branch 410 includes 4 switching transistors of the same type. The first switching transistor S 1-1 , the second switching transistor S 1-2 , the third switching transistor S 1-3 and the fourth switching transistor S 1-4 have the same polarity at the first ends. The first switching transistor S 1-1 , the second switching transistor S 1-2 , the third switching transistor S 1-3 and the fourth switching transistor S 1-4 have the same polarity at the second ends. The first switching transistor S 1-1 , the second switching transistor S 1-2 , the third switching transistor S 1-3 and the fourth switching transistor S 1-4 have the same polarity at the third ends.

[0089] In some embodiments, when the first switching transistor S 1-1 , the second switching transistor S 1-2 , the third switching transistor S 1-3 and the fourth switching transistor S 1-4 are all IGBTs, the first end is the collector and the second end is the emitter. Alternatively, when the first switching transistor S 1-1 , the second switching transistor S 1-2 , the third switching transistor S 1-3 and the fourth switching transistor S 1-4 are all MOSFETs, the first end is the drain and the second end is the source.

[0090] The first end of the first switching transistor S 1-1 and the first end of the second switching transistor S 1-2 are both connected to one end of the DC source ( Figure 4 denoted by PV in). The second end of the third switching transistor S 1-3 and the second end of the fourth switching transistor S 1-4 are both connected to the other end of the DC source. In some embodiments, the first end of the first switching transistor S 1-1 and the first end of the second switching transistor S 1-2 are both connected to the positive pole of the DC source. The second end of the third switching transistor S 1-3 and the second end of the fourth switching transistor S 1-4 are both connected to the negative pole of the DC source; or, the first end of the first switching transistor S 1-1 and the first end of the second switching transistor S​1-2 The first ends of all are connected to the negative pole of the DC power source, and the third switching transistor S 1-3 The second end and the fourth switching transistor S 1-4 The second ends of all are connected to the positive pole of the DC power source.

[0091] The second end of the first switching transistor S 1-1 is connected to the first end of the third switching transistor S 1-3 and the second end of the first switching transistor S 1-1 and the first end of the third switching transistor S 1-3 are both connected to the excitation inductor L m to be connected to the input end of the transformer 330.

[0092] The second end of the second switching transistor S 1-2 and the first end of the fourth switching transistor S 1-4 are connected, and are connected to the second end of the fifth switching transistor S 2-1 and the first end of the seventh switching transistor S 2-3 of all.

[0093] The first end of the fifth switching transistor S 2-1 is connected to the first end of the sixth switching transistor S 2-2 and then connected to the load. The second end of the fifth switching transistor S 2-1 is connected to the first end of the seventh switching transistor S 2-3 The second end of the sixth switching transistor S 2-2 is connected to the first end of the eighth switching transistor S 2-4 The second end of the seventh switching transistor S 2-3 is connected to the second end of the eighth switching transistor S 2-4 and then connected to the load. The first end of the eighth switching transistor S 2-4 is connected to the input end of the transformer 330 through the excitation inductor L m ; The first end of the fourth switching transistor S 1-4 is connected to the second end of the fifth switching transistor S 2-1 of all.

[0094] In actual implementation, the second conversion branch 420 includes 4 switching transistors of the same type. The fifth switching transistor S 2-1 , the sixth switching transistor S 2-2 , the seventh switching transistor S 2-3 and the eighth switching transistor S 2-4 have the same polarity at the first ends. The fifth switching transistor S 2-1 , the sixth switching transistor S 2-2 , the seventh switching transistor S 2-3 and the eighth switching transistor S 2-4 have the same polarity at the second ends. The fifth switching transistor S 2-1 , the sixth switching transistor S 2-2 , the seventh switching transistor S2-3 and the eighth switching transistor S 2-4 have the same polarity at the third terminal.

[0095] In some embodiments, when the fifth switching transistor S 2-1 , the sixth switching transistor S 2-2 , the seventh switching transistor S 2-3 and the eighth switching transistor S 2-4 are all IGBTs, the first terminal is the collector and the second terminal is the emitter. Alternatively, when the fifth switching transistor S 2-1 , the sixth switching transistor S 2-2 , the seventh switching transistor S 2-3 and the eighth switching transistor S 2-4 are all MOSFETs, the first terminal is the drain and the second terminal is the source.

[0096] The first terminal of the fifth switching transistor S 2-1 and the first terminal of the sixth switching transistor S 2-2 are both connected to one end of the load ( Figure 4 represented by Battery in 2-3 ). The second terminal of the seventh switching transistor S 2-4 and the second terminal of the eighth switching transistor S 2-1 are both connected to the other end of the DC source. In some embodiments, the first terminal of the fifth switching transistor S 2-2 and the first terminal of the sixth switching transistor S 2-1 are both connected to the positive pole of the DC source, and the first terminal of the fifth switching transistor S 2-2 and the first terminal of the sixth switching transistor S 1-1 are both connected to the negative pole of the DC source; or, the first terminal of the first switching transistor S 1-2 and the first terminal of the second switching transistor S 2-3 are both connected to the negative pole of the DC source, and the second terminal of the seventh switching transistor S 2-4 and the second terminal of the eighth switching transistor S

[0097] The second terminal of the fifth switching transistor S 2-1 is connected to the first terminal of the seventh switching transistor S 2-3 , and is also connected to the second terminal of the second switching transistor S 1-2 and the first terminal of the fourth switching transistor S 1-4 .

[0098] The second terminal of the sixth switching transistor S 2-2 is connected to the first terminal of the eighth switching transistor S 2-4 , and the second terminal of the sixth switching transistor S 2-2 and the first terminal of the eighth switching transistor S 2-4 are both connected to the excitation inductor L m , thereby connecting to the input end of the transformer 330.

[0099] The first switching transistor S 1-1 's second terminal and the third switching transistor S 1-3 's first terminal are both connected to the first terminal of the exciting inductor L m ; the second terminal of the sixth switching transistor S 2-2 and the first terminal of the eighth switching transistor S 2-4 are both connected to the second terminal of the exciting inductor L m . That is, the second terminal of the first switching transistor S 1-1 and the first terminal of the third switching transistor S 1-3 , and the second terminal of the sixth switching transistor S 2-2 and the first terminal of the eighth switching transistor S 2-4 are respectively connected to both ends of the exciting inductor L m , rather than the same terminal.

[0100] It should be noted that although Figure 4 it shows the case where the first conversion branch 410 is connected to the PV and the second conversion branch 420 is connected to the Battery, based on Figure 4 this, those skilled in the art can understand the case where the first conversion branch 410 is connected to the Battery and the second conversion branch 420 is connected to the PV.

[0101] According to the inverter unit provided by the embodiments of the present application, the first conversion branch is formed by the first switching transistor, the second switching transistor, the third switching transistor and the fourth switching transistor, and the second conversion branch is formed by the fifth switching transistor, the sixth switching transistor, the seventh switching transistor and the eighth switching transistor. The first conversion branch, the second conversion branch and the exciting inductor can be equivalent to an H-bridge circuit, so that the voltage of the PV / Battery can be converted into a stable DC voltage only through one-stage DC / DC conversion, one-stage inductor can be reduced, the efficiency of the inverter unit for DC / DC conversion can be improved, the number of magnetic components used in the inverter unit can be reduced, thereby reducing the overall volume of the inverter unit and lowering the cost and heat generation of the inverter unit.

[0102] In some embodiments, the control module 310 is respectively connected to the first conversion branch 410 and the second conversion branch 420. The control module 310 is further configured to: control the second switching transistor S 1-2 to be in a normally closed state; control the fourth switching transistor S 1-4 to be in a normally on state; control the fifth switching transistor S 2-1 to be in a normally closed state; and control the seventh switching transistor S 2-3 to be in a normally on state.

[0103] In actual implementation, the specific working modes of the primary side bridge arm include: the first switching transistor S 1-1 and the third switching transistor S 1-3can be used as a high-frequency tube. The sixth switching tube S in the second conversion branch 420 2-2 and the eighth switching tube S 2-4 can be used as high-frequency tubes. The first switching tube S 1-1 , the third switching tube S 1-3 , the sixth switching tube S 2-2 and the eighth switching tube S 2-4 are all used for DC / DC conversion. And the second switching tube S 1-2 is in a normally closed state, the fourth switching tube S 1-4 is in a normally on state, the fifth switching tube S 2-1 is in a normally closed state, and the seventh switching tube S 2-3 is in a normally on state.

[0104] Among them, the second switching tube S 1-2 is in a normally closed state, the fourth switching tube S 1-4 is in a normally on state, the fifth switching tube S 2-1 is in a normally closed state, and the seventh switching tube S 2-3 is in a normally on state, and all can be controlled by the control module 310.

[0105] When the second switching tube S 1-2 is in a normally closed state, the fourth switching tube S 1-4 is in a normally on state, the fifth switching tube S 2-1 is in a normally closed state, and the seventh switching tube S 2-3 is in a normally on state, as shown in part (a) of Figure 5 , the first conversion branch 410, the second conversion branch 420 and the excitation inductor L m can be equivalent to the H-bridge type BUCK-BOOST circuit shown in part (b) of Figure 5 , satisfying all working states of PV→Battery. As shown in part (b) of Figure 5 , the first switching tube S 1-1 , the third switching tube S 1-3 , the sixth switching tube S 2-2 and the eighth switching tube S 2-4 constitute the 4 vertical legs of the letter "H", and the excitation inductor L m constitutes the horizontal side of the letter "H".

[0106] It should be noted that Figure 5 and the following Figures 6 to 12 are mainly described from the circuit perspective, so the control module 310 whose main function is to control the conversion branch 320 is not shown.

[0107] According to the inverter unit provided by the embodiments of the present application, by controlling the control module to keep the second switch tube in a normally closed state, the fourth switch tube in a normally on state, the fifth switch tube in a normally closed state, and the seventh switch tube in a normally on state, the first conversion branch, the second conversion branch, and the excitation inductor can be equivalent to a BUCK-BOOST circuit. Therefore, the voltage of PV / Battery can be converted into a stable DC voltage only through one-stage DC / DC conversion, which can reduce one-stage inductor, improve the efficiency of the DC / DC conversion of the inverter unit, reduce the number of magnetic components used in the inverter unit, and thus reduce the overall volume of the inverter unit and lower the cost and heat generation of the inverter unit.

[0108] In some embodiments, the control module 310 is further configured to: control the sixth switch tube S 2-2 to be in a normally on state; control the eighth switch tube S 2-4 to be in a normally closed state.

[0109] In actual execution, as Figure 6 shown in part (a) therein, the control module 310 can also control the sixth switch tube S 2-2 to be in a normally on state and control the eighth switch tube S 2-4 to be in a normally closed state. At this time, the equivalent BUCK-BOOST circuit of the first conversion branch 410, the second conversion branch 420, and the excitation inductor L m can operate in the BUCK mode.

[0110] According to the inverter unit provided by the embodiments of the present application, by controlling the control module to keep the sixth switch tube in a normally on state and the eighth switch tube in a normally closed state, the equivalent BUCK-BOOST circuit of the first conversion branch, the second conversion branch, and the excitation inductor L m can operate in the BUCK mode. The voltage of PV / Battery can be converted into a stable DC voltage only through one-stage DC / DC conversion, which can reduce one-stage inductor, improve the efficiency of the DC / DC conversion of the inverter unit, reduce the number of magnetic components used in the inverter unit, and thus reduce the overall volume of the inverter unit and lower the cost and heat generation of the inverter unit.

[0111] In some embodiments, the control module 310 is further configured to: control the first switch tube S 1-1 to be in a normally on state; control the third switch tube S 1-3 to be in a normally closed state.

[0112] In actual execution, as Figure 6 shown in part (b) therein, the control module 310 can also control the first switch tube S 1-1 to be in a normally on state and control the third switch tube S 1-3is in the normally closed state. At this time, the first conversion branch 410, the second conversion branch 420, and the exciting inductor L m The equivalent BUCK - BOOST circuit can operate in the BOOST mode.

[0113] According to the inverter unit provided by the embodiments of the present application, by controlling the first switch tube to be in the normally - on state and the third switch tube to be in the normally - closed state through the control module, the first conversion branch, the second conversion branch, and the exciting inductor L m The equivalent BUCK - BOOST circuit operates in the BOOST mode, can convert the voltage of PV / Battery into a stable DC voltage only through one - stage DC / DC conversion, can reduce one - stage inductor, can improve the efficiency of the DC / DC conversion of the inverter unit, can reduce the number of magnetic components used in the inverter unit, thereby can reduce the overall volume of the inverter unit and lower the cost and heat generation of the inverter unit.

[0114] In some embodiments, when any conversion branch 320 includes a first H - bridge circuit, the control module 310 can also be used to control the upper arm or the lower arm of the first H - bridge circuit included in the conversion branch 320 to conduct when the input end of the conversion branch 320 is suspended (referring to no connection, that is, neither connected to the DC source nor the load). Among them, the upper arm includes two switch tubes (which can be called "upper tubes") for directly connecting to the first end of the DC source or the load. Correspondingly, the lower arm includes two switch tubes (which can be called "lower tubes") for directly connecting to the second end of the DC source or the load.

[0115] For any conversion branch 320, when the input end of the conversion branch 320 has no connection and the input ends of other conversion branches 320 are connected to the photovoltaic panel or the energy storage battery, the normal operation of other conversion branches 320 can be ensured by conducting the upper arm (including two upper tubes) or the lower arm (including two lower tubes) of the first H - bridge circuit included in the conversion branch 320.

[0116] In some embodiments, controlling the upper arm or the lower arm of the first H - bridge circuit included in the conversion branch 320 to conduct can include controlling the upper arm and the lower arm of the first H - bridge circuit included in the conversion branch 320 to conduct alternately according to a preset logic.

[0117] In some embodiments, the preset logic can include according to a preset time period or the parameters of the two conducting switch tubes exceeding a preset threshold value, etc. The above - mentioned parameters can include at least one of temperature and current, etc.

[0118] In order to eliminate the difference in the long-term reliability between the upper bridge arm or the lower bridge arm of the first H-bridge circuit included in the conversion branch 320 without any access, which is always in the on state, and the non-conducting lower bridge arm or upper bridge arm due to the long-term difference in the working state, resulting in a difference in the long-term reliability between the upper bridge arm and the lower bridge arm and affecting the working life of the whole machine, the upper bridge arm and the lower bridge arm of the first H-bridge circuit can be switched on and off to ensure the consistency of the life of each power device.

[0119] When the input end of any conversion branch 320 is suspended, the upper tubes of the H-bridge circuit included in the conversion branch 320 need to be turned on simultaneously or the lower tubes need to be turned on simultaneously to ensure the normal operation of other conversion branches 320. If the upper tubes of the first H-bridge circuit included in the conversion branch 320 are always turned on simultaneously or the lower tubes of the H-bridge circuit included in the conversion branch 320 are always turned on simultaneously, due to the long-term difference in the working state between the upper tubes and the lower tubes, the lives of the upper tubes and the lower tubes are inconsistent. Therefore, by controlling the upper tubes and the lower tubes of the first H-bridge circuit included in the conversion branch 320 to conduct alternately according to a preset logic, the long-term working states of the upper tubes and the lower tubes of the first H-bridge circuit included in the conversion branch 320 can be made consistent, extending the service life.

[0120] As Figures 7 - 8 shown, in some embodiments, the secondary side bridge arm 340 includes: a first branch, a second branch 720, and a first capacitor C bus and a third branch 730;

[0121] Wherein, the output ends of the transformer 330 are respectively connected to the input end of the first branch and the input end of the second branch 720, the output end of the first branch is connected to the input end of the second branch 720, the output end of the second branch 720 is connected to the input end of the third branch 730 through the first capacitor C bus and the output end of the third branch 730 is used as the output end of the inverter unit 300;

[0122] The first branch includes a first module 811 or a second module 711, the first module 811 includes a first inductor L1, and the second module 711 includes a first inductor L1 and a second capacitor C2 connected in series.

[0123] In actual implementation, the secondary side bridge arm 340 can adopt a two-stage structure. Figure 7 The secondary side bridge arm 340 in Figure 8 is specifically a resonant type,

[0124] The function of the second module 711 is to serve as a resonant unit. The first branch may include the first module 811 with an inductor, or the second module 711 that resonates with a series-connected inductor and a capacitor. The inductor used in the first module 811 and the second module 711 is the first inductor L1. The function of the first inductor L1 in the second module 711 is to serve as the resonant inductor L r In some embodiments, the first inductor L1 may be the leakage inductance of the secondary side of the transformer 330 or an external inductor. The capacitor included in the second module 711 is the second capacitor C2. The function of the second capacitor C2 is to serve as the resonant capacitor C r .

[0125] The input end of the first branch may be connected to the first output end among the output ends of the transformer 330, the second input end among the input ends of the second branch 720 may be connected to the second output end among the output ends of the transformer 330, and the output end of the first branch may be connected to the first input end among the input ends of the second branch 720.

[0126] The output end of the second branch 720 and the input end of the third branch 730 may be connected through the first capacitor C bus . The first capacitor C bus may be a high-voltage bus capacitor. The first capacitor C bus can be used to absorb the double-frequency ripple fluctuation of the single-phase power grid.

[0127] According to the inverter unit provided by the embodiments of the present application, through the cooperation of the first branch, the second branch, the first capacitor, and the third branch, etc., DC / DC conversion, AC / DC conversion, and DC / AC grid connection conversion can be realized on the secondary side, with simple control, low energy consumption, rich functions, and strong adaptability.

[0128] In some embodiments, the second branch 720 includes a second H-bridge circuit, and the third branch 730 includes a third H-bridge circuit.

[0129] According to the inverter unit provided by the embodiments of the present application, by both the second branch and the third branch adopting H-bridge circuits, the control is simple, the energy consumption is low, the functions are rich, and the adaptability is strong.

[0130] As Figure 9 shown, in some embodiments, when the first branch includes the first module, the second branch 720 includes: the ninth switch tube S9, the tenth switch tube S10, the third capacitor C3, and the fourth capacitor C4;

[0131] The output terminals of the transformer 330 are respectively connected to the input terminal of the first inductor L1 and the first connection point. The second terminal of the ninth switching transistor S9 is respectively connected to the output terminal of the first inductor L1 and the first terminal of the tenth switching transistor S10. The first terminal of the ninth switching transistor S9 is connected to the first terminal of the third capacitor C3. The second terminal of the third capacitor C3 is connected to the first terminal of the fourth capacitor C4. The second terminal of the fourth capacitor C4 is connected to the second terminal of the tenth switching transistor S10. The first connection point is located between the second terminal of the third capacitor C3 and the first terminal of the fourth capacitor C4.

[0132] In actual implementation, the secondary side bridge arm 340 can adopt a two-stage structure. Figure 9 The secondary side bridge arm 340 in [reference] is specifically a voltage multiplier type. In this case, the second branch 720 may not adopt an H-bridge circuit, but may include two switching transistors of the same type and two capacitors. The above two switching transistors of the same type are the ninth switching transistor S9 and the tenth switching transistor S10. The above two capacitors are the third capacitor C3 and the fourth capacitor C4.

[0133] The ninth switching transistor S9 and the tenth switching transistor S10 are switching transistors of the same type. The polarities of the first terminals of the ninth switching transistor S9 and the tenth switching transistor S10 are the same. The polarities of the second terminals of the ninth switching transistor S9 and the tenth switching transistor S10 are the same. The polarities of the third terminals of the ninth switching transistor S9 and the tenth switching transistor S10 are the same.

[0134] The ninth switching transistor S9 and the tenth switching transistor S10 can adopt any type of triode, such as High-Speed Thyristor, Gate Turn-Off Thyristor (GTO), GTR, MOSFET, or Insulated Gate Bipolar Transistor (IGBT), etc. The MOSFET can adopt Vertical Metal Oxide Semiconductor (VMOS), etc.

[0135] In some embodiments, when both the ninth switching transistor S9 and the tenth switching transistor S10 are IGBTs, the first terminal is the collector and the second terminal is the emitter. Alternatively, when both the ninth switching transistor S9 and the tenth switching transistor S10 are MOSFETs, the first terminal is the drain and the second terminal is the source.

[0136] The input terminal of the first inductor L1 can be connected to the first output terminal among the output terminals of the transformer 330. The output terminal of the first inductor L1 can be connected to the second terminal of the ninth switching transistor S9 and the first terminal of the tenth switching transistor S10. The third capacitor C3 and the fourth capacitor C4 are connected in series. One end of the third capacitor C3 that is not connected to the fourth capacitor C4 (the first terminal of the third capacitor C3) is connected to the first terminal of the ninth switching transistor S9, and one end of the fourth capacitor C4 that is not connected to the third capacitor C3 (the second terminal of the fourth capacitor C4) is connected to the tenth switching transistor S10.

[0137] The connection point of the third capacitor C3 and the fourth capacitor C4 is the first connection point. In the circuit diagram, it can be regarded that the first connection point is located between the second terminal of the third capacitor C3 and the first terminal of the fourth capacitor C4. The first connection point is connected to the second output terminal among the output terminals of the transformer 330.

[0138] According to the inverter unit provided by the embodiment of the present application, by forming a second branch circuit composed of the ninth switching transistor, the tenth switching transistor S, the third capacitor, and the fourth capacitor, etc., it is possible to achieve DC / DC conversion, AC / DC conversion, DC / AC grid connection conversion, and voltage doubling processing on the secondary side, with simple control, low energy consumption, rich functions, and strong adaptability.

[0139] For the convenience of understanding the above embodiments of the secondary side bridge arm, the following takes Figure 7 as an example to illustrate the specific working states and working modes of the inverter unit when the secondary side bridge arm 340 adopts a two-stage structure.

[0140] When a DC source (taking the DC source as a photovoltaic panel as an example) or a load (taking the load as an energy storage battery as an example) is connected to the primary side of the transformer 330 (that is, each conversion branch circuit is connected), and the secondary side is connected to the grid, the inverter unit may have the following several states:

[0141] ① Both the primary sides are connected to photovoltaic panels: In this state, there is only a working mode of photovoltaic → grid.

[0142] In the photovoltaic → grid mode, the first conversion branch circuit 410 and the second conversion branch circuit 420 perform MPPT control on the photovoltaic panel, and after the first conversion branch circuit 410 and the second conversion branch circuit 420 are cascaded, they form a DC / DC conversion with the transformer 330, the second module 711, and the second branch circuit 720, and the third branch circuit 730 performs DC / AC grid connection conversion.

[0143] ② Both the primary sides are connected to energy storage batteries: In this state, there are two working modes of energy storage → grid and grid → energy storage.

[0144] In the energy storage → grid mode, the first conversion branch 410 and the second conversion branch 420 perform high-frequency conversion and are cascaded, and then form a DC / DC conversion with the transformer 330, the second module 711, and the second branch 720. The third branch 730 performs a DC / AC grid connection conversion. In the grid → energy storage mode, the third branch 730 performs an AC / DC conversion, and the second branch 720, the second module 711, the transformer 330, the first conversion branch 410, and the second conversion branch 420 form a DC / DC conversion.

[0145] ③ The primary side access is the photovoltaic panel and the energy storage battery: In this state, there are four working modes: photovoltaic → grid, energy storage → grid, grid → energy storage, and photovoltaic → energy storage.

[0146] In the photovoltaic → grid mode, the energy storage battery does not participate in the operation. The upper arm or the lower arm of the conversion branch connected to the energy storage battery (one of the first conversion branch 410 and the second conversion branch 420) conducts simultaneously. The conversion branch connected to the photovoltaic panel (the other of the first conversion branch 410 and the second conversion branch 420) performs MPPT control and forms a DC / DC conversion with the transformer 330, the second module 711, and the second branch 720. The third branch 730 performs a DC / AC grid connection conversion.

[0147] In the energy storage → grid mode, the photovoltaic panel does not participate in the operation. The upper arm or the lower arm of the conversion branch connected to the photovoltaic panel (one of the first conversion branch 410 and the second conversion branch 420) conducts simultaneously. The conversion branch connected to the energy storage battery (the other of the first conversion branch 410 and the second conversion branch 420) performs high-frequency conversion and forms a DC / DC conversion with the transformer 330, the second module 711, and the second branch 720. The third branch 730 performs a DC / AC grid connection conversion.

[0148] In the grid → energy storage mode, the photovoltaic panel does not participate in the operation. The upper arm or the lower arm of the conversion branch connected to the photovoltaic panel (one of the first conversion branch 410 and the second conversion branch 420) conducts simultaneously. The third branch 730 performs an AC / DC conversion, and the second branch 720, the second module 711, the transformer 330, and the conversion branch connected to the energy storage battery (the other of the first conversion branch 410 and the second conversion branch 420) form a DC / DC conversion.

[0149] In the photovoltaic → energy storage mode, the exciting inductance L of the first conversion branch 410, the second conversion branch 420, and the transformer 330 mIt constitutes a DC / DC conversion. In this mode, it is the content of the foregoing embodiments. Only an inductor is provided in the transformer, and no inductor needs to be provided in the conversion branch, which can reduce one stage of inductor. The voltage of PV / Battery can be converted into a stable DC voltage only through one-stage DC / DC conversion.

[0150] It should be noted that based on the above embodiments, those skilled in the art can also understand Figure 8 and Figure 9 the specific working states and working modes of the inverter unit.

[0151] As Figures 10 - 11 shown, the secondary side bridge arm 340 includes: a fourth branch 1010 and a fifth branch 1020;

[0152] Among them, the fourth branch 1010 includes a second inductor L2 and a fifth capacitor C5 connected in series;

[0153] The fifth branch 1020 includes an eleventh switch tube S11, a twelfth switch tube S12, a thirteenth switch tube S13, and a fourteenth switch tube S14. The output end of the transformer 330 is respectively connected to the input end of the fourth branch 1010 and the second connection point. The output end of the fourth branch 1010 is connected to the third connection point. The second end of the eleventh switch tube S11 is connected to the second end of the twelfth switch tube S12. The second end of the thirteenth switch tube S13 is connected to the second end of the fourteenth switch tube S14. The first end of the twelfth switch tube S12 is connected to the first end of the thirteenth switch tube S13. The first end of the eleventh switch tube S11 and the first end of the fourteenth switch tube S14 serve as the output end of the inverter unit 300. The second connection point is located between the second end of the thirteenth switch tube S13 and the second end of the fourteenth switch tube S14, or the second connection point is determined according to the first end of the fourteenth switch tube S14. The third connection point is located between the second end of the eleventh switch tube S11 and the second end of the twelfth switch tube S12, or the third connection point is located between the first end of the twelfth switch tube S12 and the first end of the thirteenth switch tube S13.

[0154] In actual implementation, the secondary side bridge arm 340 can adopt a one-stage structure. At this time, the secondary side bridge arm 340 belongs to a kind of cycloconverter. Figure 10 The secondary side bridge arm 340 in Figure 11 is specifically a resonant type,

[0155] The function of the fourth branch 1010 is to serve as a resonant unit. The fourth branch 1010 can include a second inductor L2 and a fifth capacitor C5. The second inductor L2 and the fifth capacitor C5 are connected in series for resonance. The second inductor L2 can be connected to the first output end among the output ends of the transformer 330 and the fifth capacitor C5.

[0156] The fifth branch 1020 may include four switching tubes of the same type, namely the eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14.

[0157] The eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14 are switching tubes of the same type. The polarities of the first ends of the eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14 are the same. The polarities of the second ends of the eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14 are the same. The polarities of the third ends of the eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14 are the same.

[0158] Each of the eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14 may adopt any kind of triode, such as a high-speed thyristor, a gate turn-off thyristor (GTO), a power transistor (GTR), a MOSFET, or an insulated gate bipolar transistor (IGBT), etc. The MOSFET may adopt a vertical metal oxide semiconductor (VMOS), etc.

[0159] In some embodiments, when the eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14 are all IGBTs, the first end is the collector and the second end is the emitter. Alternatively, when the eleventh switching tube S11, the twelfth switching tube S12, the thirteenth switching tube S13, and the fourteenth switching tube S14 are all MOSFETs, the first end is the drain and the second end is the source.

[0160] The second end of the eleventh switching tube S11 may be connected to the second end of the twelfth switching tube S12. The second end of the thirteenth switching tube S13 may be connected to the second end of the fourteenth switching tube S14. The first end of the twelfth switching tube S12 may be connected to the first end of the thirteenth switching tube S13. The output end of the fourth branch 1010 (which may be the end of the fifth capacitor C5 not connected to the second inductor L2) may be connected to the third connection point, and the second output end of the output ends of the transformer 330 may be connected to the second connection point.

[0161] In some embodiments, the connection point of the second end of the eleventh switch tube S11 and the second end of the twelfth switch tube S12 may be the third connection point, and in the circuit diagram, it can be regarded that the third connection point is located between the second end of the eleventh switch tube S11 and the second end of the twelfth switch tube S12. The connection point of the second end of the thirteenth switch tube S13 and the second end of the fourteenth switch tube S14 may be the second connection point, and in the circuit diagram, it can be regarded that the second connection point is located between the second end of the thirteenth switch tube S13 and the second end of the fourteenth switch tube S14.

[0162] In some embodiments, the third connection point may be the connection point of the first end of the twelfth switch tube S12 and the first end of the thirteenth switch tube S13, and in the circuit diagram, it can be regarded that the third connection point is located between the first end of the twelfth switch tube S12 and the first end of the thirteenth switch tube S13. The second connection point can be determined according to the first end of the fourteenth switch tube S14. For example, the second connection point may be the first end of the fourteenth switch tube S14.

[0163] According to the inverter unit provided by the embodiments of the present application, a one-stage cycloconverter is formed by the fourth branch and the fifth branch, which can achieve DC / DC conversion, AC / DC conversion and DC / AC grid connection conversion on the secondary side, with simple control, low energy consumption, rich functions and strong adaptability.

[0164] As Figure 12 shown, the secondary side bridge arm 340 includes: a third inductor L3, a sixth branch 1210, a sixth capacitor C6 and a seventh capacitor C7;

[0165] Wherein, the sixth branch includes a fifteenth switch tube S15, a sixteenth switch tube S16, a seventeenth switch tube S17 and an eighteenth switch tube S18. The output end of the transformer 330 is respectively connected to the input end of the third inductor L3 and the first end of the seventeenth switch tube S17. The output end of the third inductor L3 is connected to the fourth connection point. The second end of the fifteenth switch tube S15 is connected to the second end of the sixteenth switch tube S16. The first end of the fifteenth switch tube S15 is connected to the first end of the sixth capacitor C6. The second end of the sixth capacitor C6 is connected to the first end of the seventh capacitor C7. The first end of the sixteenth switch tube S16 is connected to the first end of the seventeenth switch tube S17. The second end of the seventeenth switch tube S17 is connected to the second end of the eighteenth switch tube S18. The first end of the eighteenth switch tube S18 is connected to the second end of the seventh capacitor. The fourth connection point is located between the second end of the sixth capacitor C6 and the first end of the seventh capacitor C7.

[0166] In actual implementation, the secondary side bridge arm 340 may adopt a one-stage structure, and at this time, the secondary side bridge arm 340 belongs to a kind of cycloconverter. Figure 12 The secondary side bridge arm 340 in

[0167] The sixth branch 1210 may include 4 switching tubes of the same type, namely the fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18.

[0168] The fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18 are switching tubes of the same type. The polarities of the first ends of the fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18 are the same. The polarities of the second ends of the fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18 are the same. The polarities of the third ends of the fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18 are the same.

[0169] Each of the fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18 may adopt any type of triode, such as a high-speed thyristor, a gate turn-off thyristor (GTO), a power transistor (GTR), a MOSFET, or an insulated gate bipolar transistor (IGBT), etc. The MOSFET may adopt a vertical metal oxide semiconductor (VMOS), etc.

[0170] In some embodiments, when the fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18 are all IGBTs, the first end is the collector and the second end is the emitter. Alternatively, when the fifteenth switching tube S15, the sixteenth switching tube S16, the seventeenth switching tube S17, and the eighteenth switching tube S18 are all MOSFETs, the first end is the drain and the second end is the source.

[0171] The second end of the fifteenth switching tube S15 may be connected to the second end of the sixteenth switching tube S16. The second end of the seventeenth switching tube S17 may be connected to the second end of the eighteenth switching tube S18. The first end of the sixteenth switching tube S16 may be connected to the first end of the seventeenth switching tube S17.

[0172] The sixth capacitor C6 and the seventh capacitor C7 are connected in series, and the connection point of the sixth capacitor C6 and the seventh capacitor C7 is the fourth connection point. The output end of the third inductor L3 can be connected to the fourth connection point. The input end of the third inductor L3 can be connected to the first output end among the output ends of the transformer 330. The second output end among the output ends of the transformer 330 can be connected to the first end of the seventeenth switching transistor S17, that is, also connected to the first end of the sixteenth switching transistor S16.

[0173] It should be noted that the specific working states and working modes of the inverter unit when the secondary side bridge arm 340 adopts a one-stage structure are the same as those of the inverter unit when the secondary side bridge arm 340 adopts a two-stage structure. Reference can be made to the foregoing embodiments of the present application, and details will not be elaborated here.

[0174] It should be noted that Figures 3 to 12 in Figures 3 to 12 , the positive poles of PV and Battery are on the upper side and the negative poles are on the lower side. However, those skilled in the art can also understand the connection relationships and working processes of each branch and other components when the positive poles of PV and Battery are on the lower side and the negative poles are on the upper side on this basis.

[0175] According to the inverter unit provided by the embodiments of the present application, a one-stage cycloconverter is formed by the third inductor, the sixth branch, the sixth capacitor and the seventh capacitor, which can achieve DC / DC conversion, AC / DC conversion, DC / AC grid connection conversion and voltage doubling processing on the secondary side, with simple control, low energy consumption, rich functions and strong adaptability.

[0176] In some embodiments, the inverter unit 300 is characterized by further comprising: a filter 350; wherein, the filter 350 is connected to the output end of the secondary side bridge arm 340.

[0177] In actual implementation, in some embodiments, the output end of the inverter unit 100 can be connected to the power grid through the filter 350. The output end of the secondary side bridge arm 340 serves as the output end of the inverter unit 300. Therefore, the filter 350 is specifically connected to the output end of the secondary side bridge arm 340.

[0178] The output end of the filter 350 is connected to the power grid. Therefore, the filter 350 can be referred to as a grid filter (GridFilter) and connected to the power grid. The specific structure of the filter 350 is not limited in the embodiments of the present application.

[0179] In some embodiments, the filter 350 can adopt any LC filter circuit. For example, as Figures 7 - 12 shown, the filter 350 can adopt an LC filter circuit composed of an inductor and a capacitor.

[0180] According to the inverter unit provided by the embodiments of the present application, the output of the secondary arm is filtered by a filter, which can effectively suppress excessive fluctuations in the output current of the secondary arm.

[0181] In some embodiments, the input ends of the respective conversion branches 320 are respectively connected to a photovoltaic module or an energy storage device.

[0182] In actual implementation, for any conversion branch 320, the DC source connected to the input end of the conversion branch 320 may be a photovoltaic module, and the load connected to the input end of the conversion branch 320 may be an energy storage device. The photovoltaic module may include any one of photovoltaic panels, etc. The energy storage device may include any one or more energy storage batteries.

[0183] According to the inverter unit provided by the embodiments of the present application, by connecting the input end of the conversion branch 320 to a photovoltaic module or an energy storage device, the efficiency of DC / DC conversion and overall photovoltaic-energy storage conversion in the photovoltaic-energy storage system can be achieved.

[0184] It should be noted that in this text, the terms "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device including a series of elements not only includes those elements but also other elements not explicitly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of additional identical elements in the process, method, article or device including that element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in a reverse order according to the functions involved. For example, the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, the features described with reference to certain examples may be combined in other examples.

[0185] The embodiments of the present application have been described above in conjunction with the accompanying drawings. However, the present application is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Those of ordinary skill in the art, under the inspiration of the present application and without departing from the spirit and scope protected by the claims of the present application, can still make many forms, all of which fall within the protection scope of the present application.

[0186] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0187] Although the embodiments of this application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of this application, and the scope of this application is defined by the claims and their equivalents.

Claims

1. An inverter unit, characterized in that: include: A control module, at least two transformation branches, a transformer, and a secondary bridge arm; The input ends of the conversion branches are respectively used as the input ends of the inverter unit and connected to a DC source or a load. The output ends of the conversion branches are sequentially cascaded and connected to the input end of the transformer through the excitation inductance of the transformer. The output end of the transformer is connected to the input end of the secondary bridge arm, and the output end of the secondary bridge arm is used as the output end of the inverter unit. The control module is connected to each of the conversion branches and is used to control each of the conversion branches.

2. The inverter unit according to claim 1, characterized in that: The conversion branch includes a first H-bridge circuit.

3. The inverter unit according to claim 1, characterized in that: The at least two transformation branches include a first transformation branch and a second transformation branch; Wherein, the first conversion branch includes a first switch tube, a second switch tube, a third switch tube and a fourth switch tube, and the second conversion branch includes a fifth switch tube, a sixth switch tube, a seventh switch tube and an eighth switch tube; The first end of the first switch tube is connected to the first end of the second switch tube and then connected to the DC source, the second end of the first switch tube is connected to the first end of the third switch tube, the second end of the second switch tube is connected to the first end of the fourth switch tube, the second end of the third switch tube is connected to the second end of the fourth switch tube and then connected to the DC source, and the second end of the first switch tube is connected to the input end of the transformer through the excitation inductor; The first end of the fifth switch tube is connected to the first end of the sixth switch tube and then connected to the load, the second end of the fifth switch tube is connected to the first end of the seventh switch tube, the second end of the sixth switch tube is connected to the first end of the eighth switch tube, the second end of the seventh switch tube is connected to the second end of the eighth switch tube and then connected to the load, and the first end of the eighth switch tube is connected to the input end of the transformer through the excitation inductor; The first end of the fourth switch tube is connected to the second end of the fifth switch tube.

4. The inverter unit according to claim 3, characterized in that: The control module is connected to the first transformation branch and the second transformation branch respectively, and is further used for: Controlling the second switch tube to be in a normally closed state; Controlling the fourth switch tube to be in a normally-on state; Controlling the fifth switch tube to be in a normally closed state; The seventh switch tube is controlled to be in a normally-on state.

5. The inverter unit according to claim 4, characterized in that: The control module is also used for: Controlling the sixth switch tube to be in a normally-on state; The eighth switch tube is controlled to be in a normally closed state.

6. The inverter unit according to claim 4, characterized in that: The control module is also used for: Controlling the first switch tube to be in a normally-on state; The third switch tube is controlled to be in a normally closed state.

7. The inverter unit according to claim 1, characterized in that: The secondary bridge arm comprises: a first branch, a second branch, a first capacitor and a third branch; The output end of the transformer is connected to the input end of the first branch and the input end of the second branch respectively, the output end of the first branch is connected to the input end of the second branch, the output end of the second branch is connected to the input end of the third branch through the first capacitor, and the output end of the third branch serves as the output end of the inverter unit; The first branch includes a first module or a second module, the first module includes a first inductor, and the second module includes the first inductor and a second capacitor connected in series.

8. The inverter unit according to claim 7, characterized in that: The second branch includes a second H-bridge circuit, and the third branch includes a third H-bridge circuit.

9. The inverter unit according to claim 7, characterized in that: In the case where the first branch includes the first module, the second branch includes: a ninth switch tube, a tenth switch tube, a third capacitor and a fourth capacitor; The output end of the transformer is respectively connected to the input end and the first connection point of the first inductor, the second end of the ninth switch tube is respectively connected to the output end of the first inductor and the first end of the tenth switch tube, the first end of the ninth switch tube is connected to the first end of the third capacitor, the second end of the third capacitor is connected to the first end of the fourth capacitor, the second end of the fourth capacitor is connected to the second end of the tenth switch tube, and the first connection point is located between the second end of the third capacitor and the first end of the fourth capacitor.

10. The inverter unit according to claim 1, characterized in that: The secondary bridge arm comprises: a fourth branch and a fifth branch; Wherein, the fourth branch includes a second inductor and a fifth capacitor connected in series; The fifth branch includes an eleventh switch tube, a twelfth switch tube, a thirteenth switch tube and a fourteenth switch tube. The output end of the transformer is respectively connected to the input end and the second connection point of the fourth branch. The output end of the fourth branch is connected to the third connection point. The second end of the eleventh switch tube is connected to the second end of the twelfth switch tube, the second end of the thirteenth switch tube is connected to the second end of the fourteenth switch tube, the first end of the twelfth switch tube is connected to the first end of the thirteenth switch tube, the first end of the eleventh switch tube and the first end of the fourteenth switch tube serve as the output end of the inverter unit, the second connection point is located between the second end of the thirteenth switch tube and the second end of the fourteenth switch tube, or the second connection point is determined according to the first end of the fourteenth switch tube, the third connection point is located between the second end of the eleventh switch tube and the second end of the twelfth switch tube, or the third connection point is located between the first end of the twelfth switch tube and the first end of the thirteenth switch tube.

11. The inverter unit according to claim 1, characterized in that: The secondary bridge arm comprises: a third inductor, a sixth branch, a sixth capacitor and a seventh capacitor; Among them, the sixth branch includes a fifteenth switch tube, a sixteenth switch tube, a seventeenth switch tube and an eighteenth switch tube, the output end of the transformer is respectively connected to the input end of the third inductor and the first end of the seventeenth switch tube, the output end of the third inductor is connected to the fourth connection point, the second end of the fifteenth switch tube is connected to the second end of the sixteenth switch tube, the first end of the fifteenth switch tube is connected to the first end of the sixth capacitor, the second end of the sixth capacitor is connected to the first end of the seventh capacitor, the first end of the sixteenth switch tube is connected to the first end of the seventeenth switch tube, the second end of the seventeenth switch tube is connected to the second end of the eighteenth switch tube, the first end of the eighteenth switch tube is connected to the second end of the seventh capacitor, and the fourth connection point is located between the second end of the sixth capacitor and the first end of the seventh capacitor.

12. The inverter unit according to any one of claims 1 to 11, characterized in that: Also includes: filter; Wherein, the filter is connected to the output end of the secondary bridge arm.

13. The inverter unit according to any one of claims 1 to 11, characterized in that: The input end of each conversion branch is connected to a photovoltaic module or an energy storage device respectively.

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