Inverter

Abstract

The utility model provides an inverter, and relates to the technical field of inversion. The inverter comprises a first transformer, a first switch element, a first power switch, a second transformer, a second switch element and a second power switch; a first end of the first switch element is connected with a first end of a secondary winding of the first transformer, a second end of the first switch element is connected with a first end of a power grid and a first end of the first power switch, and a second end of the first power switch is connected with a second end of the secondary winding of the first transformer. The first end of the second switch element is connected with the first end of the secondary winding of the second transformer, the second end of the second switch element is connected with the second end of the power grid and the first end of the second power switch, and the second end of the second power switch is connected with the second end of the secondary winding of the second transformer. According to the inverter, only one switching element and one power switch are arranged in the circuit of the secondary side of the transformer when the inverter provides the half-cycle power grid voltage, so that on-state loss is generated, and efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of inverter, in particular to an inverter. Background Art

[0002] Existing isolated unipolar inverters usually adopt flyback and industrial frequency full-bridge inverter topology structures. Figure 1 A schematic diagram of the structure of an existing inverter is shown; Figure 2 FIG. 2 shows a schematic diagram of the structure of another conventional inverter. Figure 1 As shown, the existing inverter includes a transformer T11 and a secondary circuit, wherein the secondary circuit includes a diode D10, and power switches Q11, Q12, Q13 and Q14; the transformer T11 includes a primary winding and a secondary winding. One end of the secondary winding is connected to the anode of the diode D10, the cathode of the diode D10 is connected to the first ends of the power switches Q11 and Q12, the first end of the power switch Q13 is connected to the second end of the power switch Q11, the first end of the power switch Q14 is connected to the second end of the power switch Q12, the second ends of the power switches Q13 and Q14 are connected to the other end of the secondary winding, and the second end of the power switch Q11 and the second end of the power switch Q12 are connected to the power grid Vgrid, for providing AC power to the power grid Vgrid. When the power switches Q11 and Q14 are turned on, the secondary winding, the diode D10, the power switches Q11 and Q14, and the power grid Vgrid form a forward current path, for providing the positive half cycle of the power grid voltage to the power grid Vgrid. When the power switches Q12 and Q13 are turned on, the secondary winding, the diode D10, the power switches Q12 and Q13, and the grid Vgrid form a negative current loop for providing the grid Vgrid with a negative half cycle of the grid voltage.

[0003] A complete AC voltage is formed by the positive half cycle of the grid voltage and the negative half cycle of the grid voltage. When the existing inverter provides the grid Vgrid with the positive half cycle of the grid voltage, the diode D10, the power switches Q11 and Q14 are turned on, and when the existing inverter provides the grid Vgrid with the negative half cycle of the grid voltage, the diode D10, the power switches Q12 and Q13 are turned on. It can be seen that in the positive half cycle or the negative half cycle of the grid voltage output by the existing inverter, there is a diode and two power switches turned on in the circuit of the secondary side of the transformer, so that the conduction loss of the diode and the two power switches accounts for a large proportion, thereby making the efficiency of the existing inverter low.

[0004] like Figure 2As shown, the existing inverter includes a transformer T11 and a secondary circuit. The secondary circuit includes a first capacitor C1, a second capacitor C2, diodes D11 and D12, a bus capacitor Cbus, and power switches Q11, Q12, Q13 and Q14. The transformer T11 includes a primary winding and a secondary winding. One end of the first capacitor C1 and one end of the second capacitor C2 are connected to the first end of the secondary winding of the transformer 11, the other end of the first capacitor C1, the cathode of the diode D11, one end of the bus capacitor Cbus, the first end of the power switch Q11 and the first end of the power switch Q12 are connected, the anode of the diode D11 is connected to the cathode of the diode D12, the first end of the power switch Q13 is connected to the second end of the power switch Q11, the first end of the power switch Q14 is connected to the second end of the power switch Q12, the second ends of the power switches Q13 and Q14, the other end of the bus capacitor Cbus, the other end of the second capacitor, the anode of the diode D12 and the other end of the secondary winding are connected, and the second end of the power switch Q11 and the second end of the power switch Q12 are connected to the power grid Vgrid for providing alternating current to the power grid Vgrid.

[0005] When the power switches Q11 and Q14 are turned on, the secondary winding, the diode D11, the power switches Q11 and Q14, and the power grid Vgrid form a forward current path for providing the positive half cycle of the power grid voltage to the power grid Vgrid. When the power switches Q12 and Q13 are turned on, the secondary winding, the diode D12, the power switches Q12 and Q13, and the power grid Vgrid form a negative current loop for providing the negative half cycle of the power grid voltage to the power grid Vgrid. A complete AC voltage is formed by the positive half cycle of the power grid voltage and the negative half cycle of the power grid voltage. When the existing inverter provides the grid Vgrid with the positive half cycle of the grid voltage, the diode D11 and the power switches Q11 and Q14 are turned on. When the existing inverter provides the grid Vgrid with the negative half cycle of the grid voltage, the diode D12 and the power switches Q12 and Q13 are turned on. It can be seen that in the positive half cycle or the negative half cycle of the grid voltage output by the existing inverter, there is a diode and two power switches turned on in the secondary circuit, so that the conduction loss of the diode and the two power switches accounts for a large proportion, thereby making the efficiency of the existing inverter low.

[0006] Therefore, the industry urgently needs to develop an inverter with a smaller proportion of conduction losses in the power switches and higher efficiency. Utility Model Content

[0007] In view of the above-mentioned problems that the conduction loss of the diodes and power switches in the secondary circuit of the existing inverter accounts for a large proportion and the efficiency is low.

[0008] The present application provides an inverter, comprising a first transformer, a first switching element, a first power switch, a second transformer, a second switching element and a second power switch;

[0009] The first transformer comprises a first primary winding and a first secondary winding;

[0010] A first end of the first switch element is connected to a first end of the first secondary winding, and a second end of the first switch element is connected to a first end of a power grid;

[0011] A first end of the first power switch is connected to a second end of the first switch element, and a second end of the first power switch is connected to a second end of the first secondary winding;

[0012] The second transformer comprises a second primary winding and a second secondary winding;

[0013] A first end of the second switch element is connected to a first end of the second secondary winding, and a second end of the second switch element is connected to a second end of the power grid;

[0014] The first end of the second power switch is connected to the second end of the second switch element, and the second end of the second power switch is connected to the second end of the second secondary winding.

[0015] Optionally, during the operation of the first switching element and the second power switch and during the non-operation of the first power switch, the first switching element, the power grid and the second power switch form a first current path to provide the power grid with a first half-cycle power grid voltage; during the operation of the second switching element and the first power switch and during the non-operation of the second power switch, the second switching element, the power grid and the first power switch form a second current path to provide the power grid with a second half-cycle power grid voltage.

[0016] Optionally, the grid voltage of the first half cycle and the grid voltage of the second half cycle form a complete AC voltage.

[0017] Optionally, the first switching element is a diode, or a half-controlled active device, or a fully-controlled active device; the second switching element is a diode, or a half-controlled active device, or a fully-controlled active device.

[0018] Optionally, the inverter further includes a third secondary winding, a fourth secondary winding, a third switching element and a fourth switching element;

[0019] The first end of the third secondary winding is connected to the second end of the first secondary winding, the second end of the third secondary winding is connected to the first end of the third switch element, and the second end of the third switch element is connected to the second end of the first switch element;

[0020] The first end of the fourth secondary winding is connected to the second end of the second secondary winding, the second end of the fourth secondary winding is connected to the first end of the fourth switch element, and the second end of the fourth switch element is connected to the second end of the second switch element.

[0021] Optionally, the inverter further includes a first capacitor and a second capacitor;

[0022] The first capacitor is connected in parallel with the first power switch;

[0023] The second capacitor is connected in parallel with the second power switch.

[0024] Optionally, the inverter further includes a first primary circuit and a second primary circuit;

[0025] The first primary circuit is connected between a first DC power supply and the first primary winding;

[0026] The second primary circuit is connected between a second DC power supply and the second primary winding.

[0027] Optionally, the first DC power supply and the second DC power supply are the same DC power supply.

[0028] Optionally, the first primary circuit includes a third power switch, a fourth power switch, a fifth power switch, a sixth power switch and a first inductor;

[0029] The first end of the third power switch and the first end of the fourth power switch are connected to the first end of the first DC power supply; the first end of the fifth power switch is connected to the second end of the third power switch; the first end of the sixth power switch is connected to the second end of the fourth power switch; the second end of the fifth power switch and the second end of the sixth power switch are connected to the second end of the first DC power supply; the first inductor is connected between the second end of the third power switch and the first primary winding.

[0030] Optionally, the second primary circuit includes a seventh power switch, an eighth power switch, a ninth power switch, a tenth power switch and a second inductor;

[0031] The first end of the seventh power switch and the first end of the eighth power switch are connected to the first end of the second DC power supply; the first end of the ninth power switch is connected to the second end of the seventh power switch; the first end of the tenth power switch is connected to the second end of the eighth power switch; the second end of the ninth power switch and the second end of the tenth power switch are connected to the second end of the second DC power supply; the second inductor is connected between the second end of the seventh power switch and the second primary winding.

[0032] Optionally, the first primary circuit includes an eleventh power switch, a twelfth power switch, a thirteenth power switch, a fourteenth power switch, a third inductor and a third capacitor;

[0033] The first end of the eleventh power switch and the first end of the twelfth power switch are connected to the first end of the first DC power supply; the first end of the thirteenth power switch is connected to the second end of the eleventh power switch; the first end of the fourteenth power switch is connected to the second end of the twelfth power switch; the second end of the thirteenth power switch and the second end of the fourteenth power switch are connected to the second end of the first DC power supply; the first end of the third inductor is connected to the second end of the eleventh power switch, the second end of the third inductor is connected to the first end of the third capacitor, and the second end of the third capacitor is connected to the first primary winding.

[0034] Optionally, the second primary circuit includes a fifteenth power switch, a sixteenth power switch, a seventeenth power switch, an eighteenth power switch, a fourth inductor and a fourth capacitor;

[0035] The first end of the fifteenth power switch and the first end of the sixteenth power switch are connected to the first end of the second DC power supply; the first end of the seventeenth power switch is connected to the second end of the fifteenth power switch; the first end of the eighteenth power switch is connected to the second end of the sixteenth power switch; the second end of the seventeenth power switch and the second end of the eighteenth power switch are connected to the second end of the second DC power supply; the first end of the fourth inductor is connected to the second end of the fifteenth power switch, the second end of the fourth inductor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the second primary winding.

[0036] This application can achieve the following beneficial effects:

[0037] In the inverter of the present application, the first end of the first switch element is connected to the first end of the first secondary winding, and the second end of the first switch element is connected to the first end of the power grid; the first end of the first power switch is connected to the second end of the first switch element, and the second end of the first power switch is connected to the second end of the first secondary winding; the first end of the second switch element is connected to the first end of the second secondary winding, and the second end of the second switch element is connected to the second end of the power grid; the first end of the second power switch is connected to the second end of the second switch element, and the second end of the second power switch is connected to the second end of the second secondary winding; the first switch element and the second power switch and the second switch element and the first power switch work alternately, respectively, to provide the power grid with the first half-cycle power grid voltage and the second half-cycle power grid voltage, wherein the first half-cycle power grid voltage and the second half-cycle power grid voltage together constitute a complete AC voltage. When the inverter provides the power grid with a half-cycle power grid voltage, only one switch element and one power switch are needed in the circuit of the secondary side of the transformer, which is one less switch device than the traditional inverter, and the number of switch devices is reduced, the cost is reduced, the conduction loss is reduced, and the efficiency is improved.

[0038] The above is a fairly broad overview of the features and technical advantages of the present application, so that the following detailed description of the present application can be better understood. The additional features and advantages of the present application will be described below, and they form the subject matter of the claims of the present application. It will be appreciated by those skilled in the art that the disclosed concepts and specific embodiments can be easily utilized as the basis for modifying or designing other structures or processes for realizing the same purpose of the present application. It will also be appreciated by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present application as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more fully understand the present application and its advantages, reference is now made to the following description in conjunction with the accompanying drawings:

[0040] In the figure:

[0041] Figure 1 A schematic diagram of the structure of an existing inverter is shown;

[0042] Figure 2 A schematic diagram of the structure of another existing inverter is shown;

[0043] Figure 3 A schematic diagram of the structure of an inverter according to an embodiment of the present application is shown;

[0044] Figure 4 A schematic diagram of the structure of an inverter according to the first embodiment of the present application is shown;

[0045] Figure 5 for Figure 4The current path diagram of the inverter in the first half of the power frequency cycle;

[0046] Figure 6 for Figure 4 The current path diagram of the inverter in the middle and latter half of the power frequency cycle;

[0047] Figure 7 shows a voltage waveform diagram output by the inverter according to an embodiment of the present application;

[0048] Figure 8 A schematic structural diagram of an inverter according to a second embodiment of the present application is shown;

[0049] Fig. 9 A schematic structural diagram of an inverter according to a third embodiment of the present application is shown;

[0050] Fig.10 A schematic structural diagram of an inverter according to a fourth embodiment of the present application is shown.

[0051] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0052] Various exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0053] The word "exemplary" used herein means "serving as an example, embodiment or illustrative". Any embodiment described herein as "exemplary" is not necessarily to be interpreted as being superior or better than other embodiments. The terms "first", "second", "third", etc. (if any) in the specification and claims of the present utility model and the drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0054] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "coupled", "connected", and "connected" should be understood in a broad sense. For example, it can be an electrical connection or mutual communication, it can be a direct connection, it can also be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] In addition, in order to better illustrate the utility model, numerous specific details are given in the specific embodiments below. It should be understood by those skilled in the art that the utility model can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the main purpose of the utility model.

[0056] Figure 3 The structure of the inverter of the embodiment of the present application is shown. Figure 3 As shown, the inverter includes: a first transformer T1, a first switch element 32, a first power switch Q1, a second transformer T2, a second switch element 33 and a second power switch Q2. The first transformer T1 includes a first primary winding and a first secondary winding; the first end of the first switch element 32 is connected to the first end of the first secondary winding, and the second end of the first switch element 32 is connected to the first end of the power grid Vgrid; the first end of the first power switch Q1 is connected to the second end of the first switch element 32, and the second end of the first power switch Q1 is connected to the second end of the first secondary winding. The second transformer T2 includes a second primary winding and a second secondary winding; the first end of the second switch element 33 is connected to the first end of the second secondary winding, and the second end of the second switch element 33 is connected to the second end of the power grid Vgrid; the first end of the second power switch Q2 is connected to the second end of the second switch element 33, and the second end of the second power switch Q2 is connected to the second end of the second secondary winding.

[0057] Preferably, during the operation of the first switching element 32 and the second power switch Q2 and the non-operation of the first power switch Q1, the first switching element 32, the power grid Vgrid and the second power switch Q2 form a first current path to provide the power grid Vgrid with a first half-cycle power grid voltage; during the operation of the second switching element 33 and the first power switch Q1 and the non-operation of the second power switch Q2, the second switching element 33, the power grid Vgrid and the first power switch Q1 form a second current path to provide the power grid Vgrid with a second half-cycle power grid voltage.

[0058] Preferably, the grid voltage of the first half cycle and the grid voltage of the second half cycle constitute an AC voltage of a complete power frequency cycle. In this embodiment, the grid voltage of the first half cycle may be a positive half cycle of the grid voltage, and the grid voltage of the second half cycle may be a negative half cycle of the grid voltage. In other embodiments, the grid voltage of the first half cycle may be a negative half cycle of the grid voltage, and the grid voltage of the second half cycle may be a positive half cycle of the grid voltage.

[0059] In this embodiment, the first switch element 32 and the second power switch Q2 work alternately with the second switch element 33 and the first power switch Q1, that is, when the first switch element 32 and the second power switch Q2 work, the second switch element 33 and the first power switch Q1 do not work, or when the second switch element 33 and the first power switch Q1 work, the first switch element 32 and the second power switch Q2 do not work. In this embodiment, the first secondary winding, the first switch element 32, the power grid Vgrid and the second power switch Q2 form a positive current path to generate a positive half cycle of current and generate a positive half cycle of power grid voltage at both ends of the power grid Vgrid; the second secondary winding, the second switch element 33, the power grid Vgrid and the first power switch Q1 form a negative current path to generate a negative half cycle of current and generate a negative half cycle of power grid voltage at both ends of the power grid Vgrid. The positive half cycle of the power grid voltage and the negative half cycle of the power grid voltage constitute an AC voltage of a complete power frequency cycle.

[0060] In this embodiment, when the inverter outputs the positive half cycle of the grid voltage, only the first switch element 32 and the second power switch Q2 in the circuit of the secondary side of the transformer are working, and when the inverter outputs the negative half cycle of the grid voltage, only the second switch element 33 and the first power switch Q1 in the circuit of the secondary side of the transformer are working. It can be seen that when the inverter outputs the half cycle of the grid voltage, there are fewer switching devices in the working state, the conduction loss is small, the cost is low, and the efficiency is improved.

[0061] Preferably, the first power switch Q1 and the second power switch Q2 may be MOS tubes or IGBTs.

[0062] Preferably, during the operation period of the first power switch Q1 , the first power switch Q1 operates by high-frequency switching; and during the operation period of the second power switch Q2 , the second power switch Q2 operates by high-frequency switching.

[0063] Preferably, the inverter further includes a first primary circuit 31 and a second primary circuit 34. The first primary circuit 31 is connected between the first DC power supply Vdc1 and the first primary winding of the first transformer T1; the second primary circuit 34 is connected between the second DC power supply Vdc2 and the second primary winding of the second transformer T2.

[0064] Preferably, the first DC power source Vdc1 and the second DC power source Vdc2 may be two independent DC power sources or a common DC power source. In this embodiment, the first DC power source Vdc1 and the second DC power source Vdc2 are used to provide power to the inverter.

[0065] Preferably, the inverter further includes a first capacitor Co1 and a second capacitor Co2. The first capacitor Co1 is connected in parallel with the first power switch Q1; the second capacitor Co2 is connected in parallel with the second power switch Q2. The first capacitor Co1 and the second capacitor Co2 play a filtering role respectively.

[0066] Figure 4 A schematic structural diagram of an inverter according to the first embodiment of the present application is shown. Figure 5 for Figure 4 The current path diagram of the inverter in the first half of the power frequency cycle. Figure 6 for Figure 4 The current path diagram of the inverter in the middle and latter half of the power frequency cycle. Figure 4 As shown, the first switch element 32 is a diode D1, and the second switch element 33 is a diode D2. The first primary circuit 31 includes a first bus capacitor Cin1 and a first primary power switch Qp1; the first bus capacitor Cin1 is connected in parallel to the first DC power supply Vdc1, one end of the first primary winding is connected to one end of the first bus capacitor Cin1, the other end of the first primary winding is connected to the first end of the first primary power switch Qp1, and the second end of the first primary power switch Qp1 is connected to the other end of the first bus capacitor Cin1. The second primary circuit 34 includes a first bus capacitor Cin2 and a second primary power switch Qp2; the second bus capacitor Cin2 is connected in parallel to the second DC power supply Vdc2, one end of the second primary winding is connected to one end of the second bus capacitor Cin2, the other end of the second primary winding is connected to the first end of the second primary power switch Qp2, and the second end of the second primary power switch Qp2 is connected to the other end of the second bus capacitor Cin2.

[0067] like Figure 4 and 5As shown, during the operation of the first primary power switch Qp1 and the second power switch Q2, the first primary power switch Qp1 and the second power switch Q2 are both switched at high frequency and the first primary power switch Qp1 and the second power switch Q2 are alternately turned on. In this embodiment, during the operation of the first primary power switch Qp1, the second power switch Q2 is turned off, and the electric energy on the first DC power supply Vdc1 is stored in the first primary winding. During the operation of the first primary power switch Qp1, the second power switch Q2 is turned on, and the first secondary winding, the diode D1, the power grid Vgrid, and the second power switch Q2 form a first current path, such as a forward current path, so that the energy on the first secondary winding is provided to the power grid Vgrid through the diode D1 and the second power switch Q2. In this embodiment, during the operation of the first primary power switch Qp1 and the second power switch Q2, the first secondary winding, the diode D1, the power grid Vgrid, and the second power switch Q2 generate a current of the positive half cycle of the power grid, and provide the positive half cycle of the power grid voltage to the power grid Vgrid. When the grid voltage is in the positive half cycle, only the diode D1 and the second power switch Q2 generate conduction loss in the circuit on the secondary side of the transformer, so there are fewer switching devices, lower costs, and higher efficiency.

[0068] like Figure 4 and 6As shown, during the operation of the second primary power switch Qp2 and the first power switch Q1, the second primary power switch Qp2 and the first power switch Q1 are both switched at high frequency and the second primary power switch Qp2 and the first power switch Q1 are alternately turned on. In this embodiment, during the operation of the second primary power switch Qp2, the first power switch Q1 is turned off, and the electric energy on the second DC power supply Vdc2 is stored in the second primary winding. During the operation of the second primary power switch Qp2, the first power switch Q1 is turned on, and the second secondary winding, the diode D2, the power grid Vgrid, and the first power switch Q1 form a second current path, such as a negative current path, so that the energy on the second secondary winding is provided to the power grid Vgrid through the diode D2 and the first power switch Q1. In this embodiment, during the operation of the second primary power switch Qp2 and the first power switch Q1, the second secondary winding, the diode D2, the power grid Vgrid, and the first power switch Q1 generate a current of the negative half cycle of the power grid, and provide the negative half cycle of the power grid voltage to the power grid Vgrid. When the grid voltage is in the negative half cycle, only the diode D2 and the first power switch Q1 in the circuit of the secondary side of the transformer generate conduction loss, with fewer switching devices, low cost, and high efficiency. In this embodiment, the working period of the first primary power switch Qp1 and the working period of the second primary power switch Qp2 are alternated, that is, the working period of the first primary power switch Qp1 ends, and the working period of the second primary power switch Qp2 begins; the working period of the second primary power switch Qp2 ends, and the working period of the first primary power switch Qp1 begins, and the cycle repeats, so that the inverter completes the inversion function and provides AC power to the grid Vgrid.

[0069] Figure 7 FIG. 2 shows a voltage waveform diagram of the inverter output according to an embodiment of the present application. Figure 7 As shown, during the operation of the first primary power switch Qp1, the inverter outputs a positive half cycle of the grid voltage with a phase angle of 0° to 180° (also referred to as a positive grid voltage), and during the operation of the second primary power switch Qp2, the inverter outputs a negative half cycle of the grid voltage with a phase angle of 180° to 360° (also referred to as a negative grid voltage). It can be seen that during the operation of the first primary power switch Qp1 and the operation of the second primary power switch Qp2, the inverter outputs a complete industrial frequency AC voltage. In this embodiment, in each half cycle of the grid voltage, only one switching element and one power switch are working in the circuit of the secondary side of the transformer, which reduces the number of switching devices in operation, reduces costs, reduces conduction losses, and improves efficiency.

[0070] Figure 8 FIG. 2 shows a schematic diagram of the structure of an inverter according to a second embodiment of the present application. Figure 3 , Figure 4 and Figure 8 As shown, Figure 8and Figure 4 The structures of the inverters are basically the same, and the same parts of the structures are not repeated here, and the different parts are the first switch element 32 and the second switch element 33, wherein the first switch element 32 is a power switch Q3, wherein the power switch Q3 can be a fully controlled active device, such as a MOS tube or an IGBT, etc., and the second switch element 33 is a power switch Q4, wherein the power switch Q4 can be a fully controlled active device, such as a MOS tube or an IGBT, etc. During the operation of the first primary power switch Qp1 and the power switch Q3, the second power switch Q2 is always on, the first primary power switch Qp1 and the power switch Q3 are both switched at high frequency, and the first primary power switch Qp1 and the power switch Q3 are alternately turned on. When the first primary power switch Qp1 is turned on, the power switch Q3 is turned off, and the energy of the first DC power supply Vdc1 is stored in the transformer T1. When the first primary power switch Qp1 is turned off, the power switch Q3 is turned on, and the secondary winding, the power switch Q3, the grid Vgrid, and the second power switch Q2 form a forward current path to generate a positive half cycle of the grid current and provide the grid Vgrid with a positive half cycle of the grid voltage.

[0071] During the operation of the second primary power switch Qp2 and the power switch Q4, the first power switch Q1 is always on, the second primary power switch Qp2 and the power switch Q4 are both switched at high frequency, and the second primary power switch Qp2 and the power switch Q4 are alternately turned on. When the second primary power switch Qp2 is turned on, the power switch Q4 is turned off, and the energy of the second DC power supply Vdc2 is stored in the transformer T2. When the second primary power switch Qp2 is turned off, the power switch Q4 is turned on. During the operation of the second primary power switch Qp2 and the power switch Q4, the first power switch Q1 is always on, the second primary power switch Qp2 and the power switch Q4 are both switched at high frequency, and the second primary power switch Qp2 and the power switch Q4 are alternately turned on. The secondary winding, the power switch Q4, the power grid Vgrid, and the first power switch Q1 form a forward current path to generate a negative half cycle of the power grid current, and provide the power grid Vgrid with a negative half cycle of the power grid voltage.

[0072] In this embodiment, the working period of the first primary power switch Qp1 is alternated with the working period of the second primary power switch Qp2 to provide the power grid Vgrid with complete industrial frequency AC power. In this embodiment, in each half industrial frequency cycle, only two switching devices in the circuit of the secondary side of the transformer are in working state, which reduces the number of switching devices involved in the work, reduces the cost, reduces the conduction loss, and improves the efficiency. In other embodiments, during the working period of the first primary power switch Qp1, the power switch Q3 and the second power switch Q2, the first primary power switch Qp1, the power switch Q3 and the second power switch Q2 are all switched at high frequency, and the first primary power switch Qp1 is alternately turned on with the power switch Q3 and the second power switch Q2, wherein the power switch Q3 and the second power switch Q2 are turned on and off at the same time. During the operation of the second primary power switch Qp2, the power switch Q4 and the first power switch Q1, the second primary power switch Qp2, the power switch Q4 and the first power switch Q1 are all switched at high frequency, and the second primary power switch Qp2 is alternately turned on with the power switch Q4 and the first power switch Q1, wherein the power switch Q4 and the first power switch Q1 are turned on and off at the same time. In other embodiments, the first switch element 32 may be a half-controlled active device, such as a thyristor, and the second switch element 33 may be a half-controlled active device, such as a thyristor.

[0073] Fig. 9 FIG. 2 shows a schematic diagram of the structure of an inverter according to a third embodiment of the present application. Figure 3 and Fig. 9 As shown, the inverter further includes a third secondary winding, a fourth secondary winding, a third switch element, such as a diode D3, and a fourth switch element, such as a diode D4. In this embodiment, the first switch element may be a diode D1, and the second switch element may be a diode D2. The first end of the third secondary winding is connected to the second end of the first secondary winding, the second end of the third secondary winding is connected to the first end of the third switch element D3, and the second end of the third switch element D3 is connected to the second end of the first switch element D1; the first end of the fourth secondary winding is connected to the second end of the second secondary winding, the second end of the fourth secondary winding is connected to the first end of the fourth switch element D4, and the second end of the fourth switch element D4 is connected to the second end of the second switch element D2.

[0074] Preferably, if Figure 3 and Fig. 9As shown, the first primary circuit 31 includes a third power switch Q31, a fourth power switch Q32, a fifth power switch Q33, a sixth power switch Q34 and a first inductor Lr1. The first end of the third power switch Q31 and the first end of the fourth power switch Q32 are connected to the first end of the first DC power source Vdc1; the first end of the fifth power switch Q33 is connected to the second end of the third power switch Q31; the first end of the sixth power switch Q34 is connected to the second end of the fourth power switch Q32; the second end of the fifth power switch Q33 and the second end of the sixth power switch Q34 are connected to the second end of the first DC power source Vdc1; the first inductor Lr1 is connected between the second end of the third power switch Q31 and the first primary winding.

[0075] The second primary circuit 34 includes a seventh power switch Q41, an eighth power switch Q41, a ninth power switch Q43, a tenth power switch Q44 and a second inductor Lr2. The first end of the seventh power switch Q41 and the first end of the eighth power switch Q42 are connected to the first end of the second DC power source Vdc2; the first end of the ninth power switch Q43 is connected to the second end of the seventh power switch Q41; the first end of the tenth power switch Q44 is connected to the second end of the eighth power switch Q42; the second end of the ninth power switch Q443 and the second end of the tenth power switch Q44 are connected to the second end of the second DC power source Vdc2; the second inductor Lr2 is connected between the second end of the seventh power switch Q41 and the second primary winding.

[0076] Preferably, the first primary circuit 31 further includes a first bus capacitor Cin1, which is connected in parallel to both ends of the first DC power supply Vdc1. The second primary circuit 34 further includes a second bus capacitor Cin2, which is connected in parallel to both ends of the second DC power supply Vdc2. The first bus capacitor Cin1 and the second bus capacitor Cin2 are used for energy storage and filtering of the first DC power supply Vdc1 and the second DC power supply Vdc2, respectively.

[0077] Combination Figure 3 and Fig. 9The working principle of the inverter is as follows: the third power switch Q31 and the sixth power switch Q34, as well as the fourth power switch Q32 and the fifth power switch Q33 are turned on in pairs in a complementary manner, that is, the third power switch Q31 and the sixth power switch Q34 are turned on and off at the same time, and the fourth power switch Q32 and the fifth power switch Q33 are turned on and off at the same time. During the operation of the first primary circuit 31, the third power switch Q31 and the sixth power switch Q34, as well as the fourth power switch Q32 and the fifth power switch Q33 are turned on in a complementary manner, wherein the turn-on time of the third power switch Q31 and the sixth power switch Q34 and the turn-on time of the fourth power switch Q32 and the fifth power switch Q33 constitute a switching cycle. In a switching cycle, when the third power switch Q31 and the sixth power switch Q34 are turned on, the second power switch Q2 is always on, at which time the diode D1 is turned on, and the first secondary winding, the diode D1, the power grid Vgrid and the second power switch Q2 form a forward current path; when the fourth power switch Q32 and the fifth power switch Q33 are turned on, the second power switch Q2 is always on, at which time the diode D3 is turned on, and the first secondary winding, the diode D3, the power grid Vgrid and the second power switch Q2 form a forward current path.

[0078] It can be seen that during the operation of the first primary circuit 31, the first secondary winding, the diode D1 or the diode D3, the grid Vgrid and the second power switch Q2 form a forward current path to output the positive half cycle of the grid current and provide the positive half cycle of the grid voltage. The seventh power switch Q41 and the tenth power switch Q44, as well as the eighth power switch Q42 and the ninth power switch Q43 are turned on in pairs in a complementary manner, that is, the seventh power switch Q41 and the tenth power switch Q44 are turned on and off at the same time, and the eighth power switch Q42 and the ninth power switch Q43 are turned on and off at the same time. During the operation of the second primary circuit 34, the seventh power switch Q41 and the tenth power switch Q44, as well as the eighth power switch Q42 and the ninth power switch Q43 are turned on in a complementary manner, wherein the turn-on time of the seventh power switch Q41 and the tenth power switch Q44 and the turn-on time of the eighth power switch Q42 and the ninth power switch Q43 constitute a switching cycle. In a switching cycle, when the seventh power switch Q41 and the tenth power switch Q44 are turned on, the first power switch Q1 is always on, at which time the diode D2 is turned on, and the second secondary winding, the diode 2, the power grid Vgrid and the first power switch Q1 form a negative current path; when the eighth power switch Q42 and the ninth power switch Q43 are turned on, the first power switch Q1 is always on, at which time the diode D4 is turned on, and the first secondary winding, the diode D4, the power grid Vgrid and the first power switch Q1 form a forward current path. It can be seen that during the operation of the second primary circuit 34, the second secondary winding, the diode D2 or the diode D4, the power grid Vgrid and the first power switch Q1 form a forward current path to output the negative half cycle of the power grid current and provide the negative half cycle of the power grid voltage.

[0079] Preferably, the first switch element, the second switch element, the third switch element and the fourth switch element may be half-controlled active devices, such as thyristors, or fully-controlled active devices, such as MOS tubes or IGBTs.

[0080] In this embodiment, during the operation of the first primary circuit 31, the inverter provides the grid Vgrid with the positive half cycle of the grid voltage (i.e., the positive grid voltage), and during the operation of the second primary circuit 34, the inverter provides the grid Vgrid with the negative half cycle of the grid voltage (i.e., the negative grid voltage), and the positive grid voltage and the negative grid voltage constitute a complete power frequency AC voltage. In this embodiment, in each half power frequency cycle, only two switching devices in the circuit of the secondary side of the transformer are in working state, which reduces the number of switching devices involved in the operation, reduces the cost, reduces the conduction loss, and improves the efficiency.

[0081] Fig.10 A schematic structural diagram of an inverter according to a fourth embodiment of the present application is shown. Fig.10 and Fig. 9The structures and principles are basically the same, and the same parts are not repeated here. The difference between the two structures lies in the structure of the first primary circuit and the structure of the second primary circuit. Figure 3 and Fig.10 As shown, the first primary circuit 31 includes a power switch Q31, a power switch Q32, a power switch Q33, a power switch Q34, an inductor Lr1 and a third capacitor Cr1. The first end of the power switch Q31 and the first end of the power switch Q32 are connected to the first end of the first DC power supply Vdc1; the first end of the power switch Q33 is connected to the second end of the power switch Q31; the first end of the power switch Q34 is connected to the second end of the power switch Q32; the second end of the power switch Q33 and the second end of the power switch Q34 are connected to the second end of the first DC power supply Vdc1; the first end of the inductor Lr1 is connected to the second end of the power switch Q31, the second end of the inductor Lr1 is connected to the first end of the third capacitor Cr1, and the second end of the third capacitor Cr1 is connected to the first primary winding. The second primary circuit 34 includes a power switch Q41, a power switch Q42, a power switch Q43, a power switch Q44, an inductor Lr2 and a fourth capacitor Cr2. The first end of the power switch Q41 and the first end of the power switch Q42 are connected to the first end of the second DC power supply Vdc2; the first end of the power switch Q43 is connected to the second end of the power switch Q41; the first end of the power switch Q44 is connected to the second end of the power switch Q42; the second end of the power switch Q43 and the second end of the power switch Q44 are connected to the second end of the second DC power supply Vdc2; the first end of the inductor Lr2 is connected to the second end of the power switch Q41, the second end of the inductor Lr2 is connected to the first end of the fourth capacitor Cr2, and the second end of the fourth capacitor Cr2 is connected to the second primary winding.

[0082] In this embodiment, during the operation of the first primary circuit 31, the inverter provides the grid Vgrid with the positive half cycle of the grid voltage (i.e., the positive grid voltage), and during the operation of the second primary circuit 34, the inverter provides the grid Vgrid with the negative half cycle of the grid voltage (i.e., the negative grid voltage), and the positive grid voltage and the negative grid voltage constitute a complete power frequency AC voltage. In this embodiment, in each half power frequency cycle, only two switching devices in the circuit of the secondary side of the transformer are in working state, which reduces the number of switching devices involved in the operation, reduces the cost, reduces the conduction loss, and improves the efficiency.

[0083] Although the embodiments of the present application and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

[0084] In addition, the scope of the present application is not limited to the specific embodiments of the processes, machines, manufactures, material compositions, modes, methods, and steps described in this specification. Those skilled in the art will readily understand from the disclosure of the present application that, according to the present application, currently existing or later to be developed processes, machines, manufactures, material compositions, modes, methods, or steps that perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein may be utilized. Therefore, it is intended that the appended claims include such processes, machines, manufactures, material compositions, modes, methods, or steps within their scope.

Claims

1. An inverter, characterized in that: include: A first transformer, a first switching element, a first power switch, a second transformer, a second switching element, and a second power switch; The first transformer comprises a first primary winding and a first secondary winding; A first end of the first switch element is connected to a first end of the first secondary winding, and a second end of the first switch element is connected to a first end of a power grid; A first end of the first power switch is connected to a second end of the first switch element, and a second end of the first power switch is connected to a second end of the first secondary winding; The second transformer comprises a second primary winding and a second secondary winding; A first end of the second switch element is connected to a first end of the second secondary winding, and a second end of the second switch element is connected to a second end of the power grid; The first end of the second power switch is connected to the second end of the second switch element, and the second end of the second power switch is connected to the second end of the second secondary winding.

2. The inverter according to claim 1, characterized in that: During the operation of the first switching element and the second power switch and during the non-operation of the first power switch, the first switching element, the power grid and the second power switch form a first current path to provide the power grid with a first half-cycle power grid voltage; during the operation of the second switching element and the first power switch and during the non-operation of the second power switch, the second switching element, the power grid and the first power switch form a second current path to provide the power grid with a second half-cycle power grid voltage.

3. The inverter according to claim 2, characterized in that: The grid voltage of the first half cycle and the grid voltage of the second half cycle form a complete AC voltage.

4. The inverter according to claim 1, characterized in that: The first switch element is a diode, or a half-controlled active device, or a fully-controlled active device; the second switch element is a diode, or a half-controlled active device, or a fully-controlled active device.

5. The inverter according to claim 1, characterized in that: It also includes a third secondary winding, a fourth secondary winding, a third switching element and a fourth switching element; The first end of the third secondary winding is connected to the second end of the first secondary winding, the second end of the third secondary winding is connected to the first end of the third switch element, and the second end of the third switch element is connected to the second end of the first switch element; The first end of the fourth secondary winding is connected to the second end of the second secondary winding, the second end of the fourth secondary winding is connected to the first end of the fourth switch element, and the second end of the fourth switch element is connected to the second end of the second switch element.

6. The inverter according to claim 1, characterized in that: Also includes a first capacitor and a second capacitor; The first capacitor is connected in parallel with the first power switch; The second capacitor is connected in parallel with the second power switch.

7. The inverter according to claim 1, characterized in that: Also includes a first primary circuit and a second primary circuit; The first primary circuit is connected between a first DC power supply and the first primary winding; The second primary circuit is connected between a second DC power supply and the second primary winding.

8. The inverter according to claim 7, characterized in that: The first DC power supply and the second DC power supply are the same DC power supply.

9. The inverter according to claim 7, characterized in that: The first primary circuit includes a third power switch, a fourth power switch, a fifth power switch, a sixth power switch and a first inductor; The first end of the third power switch and the first end of the fourth power switch are connected to the first end of the first DC power supply; the first end of the fifth power switch is connected to the second end of the third power switch; the first end of the sixth power switch is connected to the second end of the fourth power switch; the second end of the fifth power switch and the second end of the sixth power switch are connected to the second end of the first DC power supply; the first inductor is connected between the second end of the third power switch and the first primary winding.

10. The inverter according to claim 7 or 9, characterized in that: The second primary circuit includes a seventh power switch, an eighth power switch, a ninth power switch, a tenth power switch and a second inductor; The first end of the seventh power switch and the first end of the eighth power switch are connected to the first end of the second DC power supply; the first end of the ninth power switch is connected to the second end of the seventh power switch; the first end of the tenth power switch is connected to the second end of the eighth power switch; the second end of the ninth power switch and the second end of the tenth power switch are connected to the second end of the second DC power supply; the second inductor is connected between the second end of the seventh power switch and the second primary winding.

11. The inverter according to claim 7, characterized in that: The first primary circuit includes an eleventh power switch, a twelfth power switch, a thirteenth power switch, a fourteenth power switch, a third inductor and a third capacitor; The first end of the eleventh power switch and the first end of the twelfth power switch are connected to the first end of the first DC power supply; the first end of the thirteenth power switch is connected to the second end of the eleventh power switch; the first end of the fourteenth power switch is connected to the second end of the twelfth power switch; the second end of the thirteenth power switch and the second end of the fourteenth power switch are connected to the second end of the first DC power supply; the first end of the third inductor is connected to the second end of the eleventh power switch, the second end of the third inductor is connected to the first end of the third capacitor, and the second end of the third capacitor is connected to the first primary winding.

12. The inverter according to claim 7 or 11, characterized in that: The second primary circuit includes a fifteenth power switch, a sixteenth power switch, a seventeenth power switch, an eighteenth power switch, a fourth inductor and a fourth capacitor; The first end of the fifteenth power switch and the first end of the sixteenth power switch are connected to the first end of the second DC power supply; the first end of the seventeenth power switch is connected to the second end of the fifteenth power switch; the first end of the eighteenth power switch is connected to the second end of the sixteenth power switch; the second end of the seventeenth power switch and the second end of the eighteenth power switch are connected to the second end of the second DC power supply; the first end of the fourth inductor is connected to the second end of the fifteenth power switch, the second end of the fourth inductor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the second primary winding.

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