Three-phase five-level inverter and application circuit thereof

Abstract

The application provides a three-phase five-level inverter and an application circuit thereof, and relates to the field of electronic power. The three-phase five-level inverter comprises a first direct-current voltage dividing capacitor, a second direct-current voltage dividing capacitor, a three-phase common circuit module, an A-phase bridge arm, a B-phase bridge arm and a C-phase bridge arm; the three-phase common circuit module, the A-phase bridge arm, the B-phase bridge arm and the C-phase bridge arm are connected with a plurality of control ends, and under the control of control signals inputted into the control ends, the AC output end of each phase bridge arm can output V dc / 2, V dc / 4, 0, -V dc / 4 and -V dc / 2 five levels respectively. Compared with a traditional three-phase five-level NPC type inverter, the three-phase five-level inverter saves active switching devices and diodes, and significantly reduces the cost under the condition of ensuring the quality of output waveforms.

Description

Technical Field

[0001] This invention relates to the field of electronic power technology, specifically to a three-phase five-level inverter and its application circuit. Background Technology

[0002] Multilevel inverters have been widely used due to their advantages such as reduced dv / dt, low total harmonic distortion, reduced power consumption, fewer filter requirements, easy integration, high frequency operation, and low EMI.

[0003] The existing three-phase multilevel inverter is composed of three single-phase multilevel inverters. The number of power devices in the three-phase inverter is three times that of the single-phase inverter.

[0004] In other words, existing three-phase multilevel inverters use a large number of active devices, resulting in high costs. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a three-phase five-level inverter and its application circuit, which solves the technical problem of the large number of active devices used in existing three-phase multi-level inverters.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a three-phase five-level inverter, wherein the input side is connected to a DC input power supply. V dc The three-phase five-level inverter includes: a first DC voltage divider capacitor, a second DC voltage divider capacitor, a three-phase common circuit module, an A-phase bridge arm, a B-phase bridge arm, and a C-phase bridge arm; The first DC voltage divider capacitor and the second DC voltage divider capacitor are connected in series and then in parallel across the DC input power supply, and the series connection point of the first DC voltage divider capacitor and the second DC voltage divider capacitor is the voltage midpoint of the DC input power supply. The three-phase common circuit module includes: a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first floating capacitor, and a second floating capacitor; the first to eighth switches are connected in series, the first end of the first switch is connected to the positive terminal of the DC input power supply, the second end of the eighth switch is connected to the negative terminal of the DC input power supply, and the common terminal of the fourth and fifth switches is connected to the voltage midpoint; the first end of the first floating capacitor is connected to the connection between the first and second switches, the second end of the first floating capacitor is connected to the connection between the third and fourth switches, the first end of the second floating capacitor is connected to the connection between the fifth and sixth switches, and the second end of the second floating capacitor is connected to the connection between the seventh and eighth switches; The A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm each include three connection terminals. The first terminal of the A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm is connected to the connection between the second and third switching transistors. The second terminal of the A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm is connected to the connection between the sixth and seventh switching transistors. The third terminal of the A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm is connected to the AC output terminal. The three-phase common circuit module, phase A arm, phase B arm, and phase C arm are connected to several control terminals, which are suitable for each phase arm to output AC signals under the control of the control signals input to the control terminals. V dc / 2, V dc / 4, 0, - V dc / 4 and - V dc / 2 five levels.

[0007] Preferably, the A-phase bridge arm includes: Ninth switch, tenth switch, eleventh switch, twelfth switch, first diode, and second diode; among which, The ninth, tenth, eleventh, and twelfth switches are connected in series; the first end of the ninth switch is the first end of the A-phase bridge arm; the second end of the twelfth switch is the second end of the A-phase bridge arm; and the connection between the tenth and eleventh switches is the third end of the A-phase bridge arm. The cathode of the first diode is connected to the junction of the ninth and tenth switching transistors; the anode of the first diode is connected to the cathode of the second diode. The positive terminal of the second diode is connected to the junction of the eleventh and twelfth switching transistors; The B-phase bridge arm includes: The thirteenth, fourteenth, fifteenth, twelfth, and sixteenth switching transistors, the third diode, and the fourth diode; among them, The thirteenth, fourteenth, fifteenth, and twelfth / sixth switches are connected in series; the first end of the thirteenth switch is the first end of the B-phase bridge arm; the second end of the sixteenth switch is the second end of the B-phase bridge arm; and the connection between the fourteenth and fifteenth switches is the third end of the B-phase bridge arm. The negative terminal of the third diode is connected to the connection point between the thirteenth and fourteenth switching transistors; the positive terminal of the third diode is connected to the negative terminal of the fourth diode. The positive terminal of the fourth diode is connected to the connection point between the fifteenth and sixteenth switching transistors; The C-phase bridge arm includes: The seventeenth, eighteenth, nineteenth, and twentieth switching transistors, the fifth diode, and the sixth diode; among them, The seventeenth, eighteenth, nineteenth, and twentieth switches are connected in series; the first end of the seventeenth switch is the first end of the C-phase bridge arm; the second end of the twentieth switch is the second end of the C-phase bridge arm; and the connection between the eighteenth and nineteenth switches is the third end of the C-phase bridge arm. The negative terminal of the fifth diode is connected to the connection point between the seventeenth and eighteenth switching transistors; the positive terminal of the fifth diode is connected to the negative terminal of the sixth diode. The positive terminal of the sixth diode is connected to the junction of the nineteenth and twentieth switching transistors.

[0008] Preferably, in phase A bridge arm, the common terminal of the first diode and the second diode is grounded; In phase B bridge arm, the common terminal of the third diode and the fourth diode is grounded; In the C-phase bridge arm, the common terminal of the fifth and sixth diodes is grounded.

[0009] Preferably, the control terminal is the third terminal of the switching transistor, used to receive control signals, and to turn the switching transistor on or off under the control of the control signals.

[0010] Secondly, the present invention provides a grid-connected application circuit for a three-phase five-level inverter, the grid-connected application circuit comprising: a filter and a three-phase five-level inverter as described above; wherein... The DC input source of the three-phase five-level inverter is a photovoltaic panel or an energy storage battery, and the AC output of the three-phase five-level inverter is connected to the power grid through a filter.

[0011] Preferably, the filter includes an L-type filter, an LC-type filter, and an LCL-type filter.

[0012] Preferably, the grid-connected application circuit further includes a DC / DC converter. The input terminal of the DC / DC converter is connected to a photovoltaic panel or an energy storage battery, and the output terminal is connected to the input side of a three-phase five-level inverter.

[0013] Thirdly, the present invention provides an off-grid application circuit for a three-phase five-level inverter, the off-grid application circuit comprising an LC filter and a three-phase five-level inverter as described above; wherein... The DC input source of the three-phase five-level inverter is a DC power supply, and the AC output of the three-phase five-level inverter is connected to a purely resistive load through an LC filter.

[0014] Fourthly, the present invention provides an off-grid application circuit for a three-phase five-level inverter, the off-grid application circuit comprising an L-filter and a three-phase five-level inverter as described above; wherein, The DC input source of the three-phase five-level inverter is a DC power supply, and the AC output of the three-phase five-level inverter is connected to the motor through an L filter.

[0015] (III) Beneficial Effects This invention provides a three-phase five-level inverter and its application circuit. Compared with the prior art, it has the following advantages: The present invention proposes a three-phase five-level inverter, which, compared with the traditional three-phase five-level NPC type inverter, shares a three-phase common circuit module. While ensuring the quality of the output waveform, it saves active switching devices and diodes, thus significantly reducing costs. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of an existing NPC-type five-level inverter circuit; Figure 2 This is a schematic diagram of an existing FC-type five-level inverter circuit; Figure 3 Here is a schematic diagram of an existing CHB-type five-level inverter circuit; Figure 4 Here is a schematic diagram of an existing ANPC type five-level inverter circuit; Figure 5This is a schematic diagram of the structure of a three-phase five-level inverter according to an embodiment of the present invention; Figure 6 The circuit diagram of the three-phase five-level inverter according to an embodiment of the present invention; Figure 7 for Figure 6 The spatial vector diagram of the three-phase five-level inverter is shown below; Figure 8 This is a schematic diagram of a grid-connected circuit for a three-phase five-level inverter in one embodiment; Figures 9-11 The circuit diagrams show three types of filters used in grid-connected applications. Figure 9 It is an L-type filter. Figure 10 It is an LC type filter. Figure 11 It is an LCL type filter; Figure 12 This is a schematic diagram of a grid-connected application circuit for a three-phase five-level inverter with a DC / DC converter on the DC side. Figure 13 A schematic diagram of an off-grid application circuit for a three-phase five-level inverter with a purely resistive load; Figure 14 This is a schematic diagram of an off-grid application circuit for a three-phase five-level inverter with a motor load. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that, for ease of description, the IGBT is used to represent the controllable (on and off) switching transistor in the embodiments of this invention, but the switching transistor in this invention is not limited to IGBT. An IGBT is used as an example for explanation. The first terminal of the IGBT refers to the collector, the second terminal to the emitter, and the control terminal to the gate. A drive control signal is applied to the control terminal of each switching transistor in the embodiments of this invention. For simplicity, this will not be elaborated further. The power switching transistor in the embodiments of this invention can also be implemented using other controllable switching transistor devices besides IGBT, such as MOSFET. Meanwhile, to ensure the normal operation of each switching device in the embodiments of this invention, a freewheeling diode needs to be connected in parallel with each switching device. The parallel direction of the freewheeling diode is related to the type of switching device, and those skilled in the art can set it according to the type of switching device; it is not limited here. Unless otherwise specified, the switching device implicitly includes a freewheeling diode, which will be indicated in this embodiment in special cases.

[0020] This application provides a three-phase five-level inverter and its application circuit, which solves the technical problem of the large number of active devices used in existing three-phase multi-level inverters, thereby saving active devices and reducing device costs.

[0021] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows: Figures 1-4 Four classic types of five-level inverter structures are shown. Theoretically, these four types can extend the output to any level, and the more levels there are, the higher the output power quality. However, as the number of levels increases, the number of components in the multilevel inverter increases excessively, the structure becomes complex, and efficiency is reduced. Problems such as capacitor voltage imbalance also exist. For the classic multilevel structure with n levels, the number of power switching devices required is 2(n-1). In addition, the CHB type requires (n-1) / 2 DC sources, which limits its practical application. The NPC type requires (n-1) or more DC-side voltage divider capacitors and (n-1) / (n-2) clamping diodes. Similarly, the FC type requires (n-1) voltage divider capacitors and (n-1) / (n-2) / 2 flying capacitors. Therefore, high-level MLI requires a large number of components, leading to reduced overall system efficiency and power density, hindering the application of multilevel inverters in the field of power conversion. To address the aforementioned issues, this invention proposes a three-phase five-level inverter. Compared to existing three-phase five-level NPC inverters, this inverter saves four active switching devices and 18 diodes while maintaining output waveform quality, effectively reducing device costs.

[0022] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0023] like Figure 5 As shown, the three-phase five-level inverter of this embodiment of the invention has a DC input power supply connected to its input side. V dc The inverter includes a first DC voltage divider capacitor C1 and a second DC voltage divider capacitor C2. The first and second DC voltage divider capacitors are connected in series and then in parallel across the DC input power supply. The series connection point of the first DC voltage divider capacitor C1 and the second DC voltage divider capacitor C2 is the voltage midpoint O of the DC input power supply. The inverter also includes a three-phase common circuit module, an A-phase bridge arm, a B-phase bridge arm, and a C-phase bridge arm; wherein... The three-phase common circuit module includes: a first switch S1, a second switch S2, a third switch S3, a fourth switch S4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8, a first floating capacitor C3, and a second floating capacitor C4; the first switch S1 to the eighth switch S8 are connected in series, and the first terminal of the first switch S1 is connected to the DC input power supply. V dc The positive terminal of the eighth switch S8 is connected to the DC input power supply. V dc The negative terminal of the first floating capacitor C3 is connected to the common terminal of the fourth switch S4 and the fifth switch S5, which is connected to the voltage midpoint O. The first terminal of the first floating capacitor C3 is connected to the connection between the first switch S1 and the second switch S2, the second terminal of the first floating capacitor C3 is connected to the connection between the third switch S3 and the fourth switch S4, the first terminal of the second floating capacitor C4 is connected to the connection between the fifth switch S5 and the sixth switch S6, and the second terminal of the second floating capacitor C4 is connected to the connection between the seventh switch S7 and the eighth switch S8. The first end of the A-phase bridge arm is connected to the connection between the second switch S2 and the third switch S3, the second end is connected to the connection between the sixth switch S6 and the seventh switch S7, and the third end is the AC output end. The first end of the B-phase bridge arm is connected to the connection between the second switch S2 and the third switch S3, the second end is connected to the connection between the sixth switch S6 and the seventh switch S7, and the third end is the AC output end. The first end of the C-phase bridge arm is connected to the connection between the second switch S2 and the third switch S3, the second end is connected to the connection between the sixth switch S6 and the seventh switch S7, and the third end is the AC output end. The three-phase common circuit module, phase A bridge arm, phase B bridge arm, and phase C bridge arm are connected to several control terminals, allowing each phase bridge arm to output its own signal under the control of the control signals input to the control terminals. V dc / 2, V dc / 4, 0, - V dc / 4 and - V dc / 2 five levels.

[0024] like Figure 6 As shown, this embodiment of the invention includes two DC voltage divider capacitors. C 1 and C 2. Two floating capacitors, 20 active power switching devices S 1~ S 20 . Vdc This is a DC power supply. P, O, and N represent the positive, neutral, and negative terminals of the power supply, respectively. A, B, and C represent the three-phase output of the inverter, and the capacitors... C 1 and C The voltages of 2 are both V dc / 2, capacitor C 3 and C The voltage of 4 is V dc / 4, i a , i b , i c These are the three-phase output currents.

[0025] Two switching transistors are connected between the first and third ends of the three-phase bridge arms A, B, and C. Two switching transistors are also connected between the second and third ends of the three-phase bridge arms A, B, and C. At the same time, two diodes are connected in parallel between the intermediate switching transistors. S 9. S 10 , S 11 , S 12 , D 1 and D 2 constitutes phase A bridge arm, S 13 , S 14 , S 15 , S 16 , D 3 and D 4 constitutes phase B of the bridge arm. S 17 , S 18 , S 19 , S 20 , D 5 and D 6 form the C-phase bridge arm.

[0026] In phase A bridge arm, the switching transistor S 9. S 10 , S 11 , S 12 The ninth switch is connected in series. S The first terminal of switch 9 is connected to the connection between the second switch S2 and the third switch S3; the twelfth switch... S12 The second end is connected at the connection between the sixth switch S6 and the seventh switch S7; the ninth switch S9 and the tenth switch S... 10 The connection point is connected to the negative terminal of the first diode D1, the positive terminal of the first diode D1 is connected to the negative terminal of the second diode D2, and the positive terminal of the second diode D2 is connected to the eleventh switching transistor S. 11 With the twelfth switch S 12 The connection point of the first diode D1 and the second diode D2 is grounded. The tenth switch S... 10 and the eleventh switch S 11 Connect the AC output terminal at the connection point.

[0027] In phase B bridge arm, the switching transistor S 13 , S 14 , S 15 , S 16 The thirteenth switch is connected in series. S 13 The first end is connected to the connection between the second switch S2 and the third switch S3; the sixteenth switch... S 16 The second end is connected at the connection between the sixth switch S6 and the seventh switch S7; the thirteenth switch S... 13 With the fourteenth switch S 14 The connection point is connected to the negative terminal of the third diode D3, the positive terminal of the third diode D3 is connected to the negative terminal of the fourth diode D4, and the positive terminal of the fourth diode D4 is connected to the fifteenth switching transistor S. 15 With the sixteenth switch S 16 The connection point of diodes D3 and D4 is grounded. The fourteenth switch S... 14 and the fifteenth switch S 15 Connect the AC output terminal at the connection point.

[0028] In the C-phase bridge arm, the switching transistor S 17 , S 18 , S 19 , S 20 The seventeenth switch is connected in series. S 17 The first end is connected to the connection between the second switch S2 and the third switch S3; the twentieth switch... S 20 The second end is connected at the connection between the sixth switch S6 and the seventh switch S7; the seventeenth switch S...17 With the eighteenth switching transistor S 18 The connection point is connected to the negative terminal of the fifth diode D5, the positive terminal of the fifth diode D5 is connected to the negative terminal of the sixth diode D6, and the positive terminal of the sixth diode D6 is connected to the nineteenth switching transistor S. 19 With the twentieth switching transistor S 20 The connection point of diodes D5 and D6. The common terminal of diode D5 and D6 is grounded. The eighteenth switching transistor S. 18 and the nineteenth switch S 19 Connect the AC output terminal at the connection point.

[0029] like Figure 7 As shown, the three-phase five-level inverter of this embodiment has a total of 77 operating modes (vectors). For ease of representation during modal analysis, the five levels are represented as... V dc / 2, V dc / 4, 0, - V dc / 4 and - V dc / 2 is represented by 4, 3, 2, 1, and 0 respectively. The distribution of all vectors on the plane is as follows: Figure 7 As shown. Based on their magnitudes, all vectors can be divided into five categories. The five vectors at the center have a magnitude of 0 and are called zero vectors; a total of 12 vectors are distributed on the first hexagon, which can be divided into 6 groups, each containing 2 redundant vectors, and their vector lengths are... V dc / 6; A total of 24 vectors are distributed on the second hexagon, of which 18 vectors have a length of V dc / 3, each group contains 3 redundant vectors, and the length of the 6 vectors is V dc / 6, each group has only 1 vector; the third hexagon has a total of 24 vectors, of which 12 vectors have a length of 1 / 6. V dc / 2, each group contains 2 redundant vectors, and the length of the 12 vectors is V dc / 6; 12 vectors are distributed on the outermost hexagon, of which 6 vectors have a length of 2. V dc / 3, the other 6 vectors have lengths of V dc / 3. In the spatial vector diagram, the redundant vector has opposite effects on the voltage of the floating capacitor and the bus capacitor, and can be used to balance the capacitors. Therefore, the proposed inverter does not require an additional capacitor balancing circuit, saving costs.

[0030] This invention also provides a grid-connected application circuit for a three-phase five-level inverter, such as... Figure 8 As shown, the grid-connected application circuit includes: the aforementioned three-phase five-level inverter and filter. The DC input source of the three-phase five-level inverter is a photovoltaic panel or an energy storage battery, and the AC output of the three-phase five-level inverter is connected to the power grid through the filter.

[0031] like Figure 9 , Figure 10 , Figure 11 As shown, the filter types include L-type, LC-type, and LCL-type.

[0032] like Figure 12 As shown, a DC / DC converter can be added to the front end of the grid-connected application circuit to change the voltage, thereby widening the input voltage range of the three-phase five-level inverter application circuit.

[0033] This invention also provides an off-grid application circuit for a three-phase five-level inverter, such as... Figure 13 As shown, the off-grid application circuit includes the aforementioned three-phase five-level inverter and LC filter. The DC input source of the three-phase five-level inverter is a DC power supply, and the AC output of the three-phase five-level inverter is connected to a purely resistive load through the LC filter.

[0034] This invention also provides an off-grid application circuit for a three-phase five-level inverter, such as... Figure 14 As shown, the off-grid application circuit includes the aforementioned three-phase five-level inverter and L filter. The DC input source of the three-phase five-level inverter is a DC power supply, and the AC output of the three-phase five-level inverter is connected to the motor through the L filter.

[0035] In summary, compared with existing technologies, it has the following beneficial effects: 1. This invention proposes a three-phase five-level inverter. Compared with the traditional three-phase five-level NPC inverter, this three-phase five-level inverter uses a common three-phase circuit module. While ensuring the quality of the output waveform, it saves active switching devices and diodes, thus significantly reducing costs.

[0036] 2. The three-phase five-level inverter of this embodiment does not require an additional capacitor balancing circuit, thus saving costs.

[0037] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0038] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-phase five-level inverter, wherein a DC input power supply is connected to the input side. V dc Its characteristics are, The three-phase five-level inverter includes: a first DC voltage divider capacitor, a second DC voltage divider capacitor, a three-phase common circuit module, an A-phase bridge arm, a B-phase bridge arm, and a C-phase bridge arm; The first DC voltage divider capacitor and the second DC voltage divider capacitor are connected in series and then in parallel across the DC input power supply, and the series connection point of the first DC voltage divider capacitor and the second DC voltage divider capacitor is the voltage midpoint of the DC input power supply. The three-phase common circuit module includes: a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first floating capacitor, and a second floating capacitor; the first to eighth switches are connected in series, the first end of the first switch is connected to the positive terminal of the DC input power supply, the second end of the eighth switch is connected to the negative terminal of the DC input power supply, and the common terminal of the fourth and fifth switches is connected to the voltage midpoint; the first end of the first floating capacitor is connected to the connection between the first and second switches, the second end of the first floating capacitor is connected to the connection between the third and fourth switches, the first end of the second floating capacitor is connected to the connection between the fifth and sixth switches, and the second end of the second floating capacitor is connected to the connection between the seventh and eighth switches; The A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm each include three connection terminals. The first terminal of the A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm is connected to the connection between the second and third switching transistors. The second terminal of the A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm is connected to the connection between the sixth and seventh switching transistors. The third terminal of the A-phase bridge arm, B-phase bridge arm, and C-phase bridge arm is connected to the AC output terminal. The A-phase bridge arm includes: Ninth switch, tenth switch, eleventh switch, twelfth switch, first diode, and second diode; among which, The ninth, tenth, eleventh, and twelfth switches are connected in series; the first end of the ninth switch is the first end of the A-phase bridge arm; the second end of the twelfth switch is the second end of the A-phase bridge arm; and the connection between the tenth and eleventh switches is the third end of the A-phase bridge arm. The cathode of the first diode is connected to the junction of the ninth and tenth switching transistors; the anode of the first diode is connected to the cathode of the second diode; the common terminal of the first and second diodes is grounded. The positive terminal of the second diode is connected to the junction of the eleventh and twelfth switching transistors; The B-phase bridge arm includes: The thirteenth, fourteenth, fifteenth, twelfth, and sixteenth switching transistors, the third diode, and the fourth diode; among them, The thirteenth, fourteenth, fifteenth, and twelfth / sixth switches are connected in series; the first end of the thirteenth switch is the first end of the B-phase bridge arm; the second end of the sixteenth switch is the second end of the B-phase bridge arm; and the connection between the fourteenth and fifteenth switches is the third end of the B-phase bridge arm. The negative terminal of the third diode is connected to the connection point of the thirteenth and fourteenth switching transistors; the positive terminal of the third diode is connected to the negative terminal of the fourth diode; the common terminal of the third and fourth diodes is grounded. The positive terminal of the fourth diode is connected to the connection point between the fifteenth and sixteenth switching transistors; The C-phase bridge arm includes: The seventeenth, eighteenth, nineteenth, and twentieth switching transistors, the fifth diode, and the sixth diode; among them, The seventeenth, eighteenth, nineteenth, and twentieth switches are connected in series; the first end of the seventeenth switch is the first end of the C-phase bridge arm; the second end of the twentieth switch is the second end of the C-phase bridge arm; and the connection between the eighteenth and nineteenth switches is the third end of the C-phase bridge arm. The negative terminal of the fifth diode is connected to the connection point of the seventeenth and eighteenth switching transistors; the positive terminal of the fifth diode is connected to the negative terminal of the sixth diode; the common terminal of the fifth and sixth diodes is grounded. The positive terminal of the sixth diode is connected to the connection point between the nineteenth and twentieth switching transistors; The three-phase common circuit module, phase A arm, phase B arm, and phase C arm are connected to several control terminals, which are suitable for each phase arm to output AC signals under the control of the control signals input to the control terminals. V dc / 2, V dc / 4, 0, - V dc / 4 and - V dc / 2 five levels.

2. The three-phase five-level inverter as described in claim 1, characterized in that, The control terminal is the third terminal of the switching transistor, used to receive control signals and, under the control of the control signals, to turn the switching transistor on or off.

3. A grid-connected application circuit for a three-phase five-level inverter, characterized in that, The grid-connected application circuit includes: a filter and a three-phase five-level inverter as described in any one of claims 1 to 2; wherein... The DC input source of the three-phase five-level inverter is a photovoltaic panel or an energy storage battery, and the AC output of the three-phase five-level inverter is connected to the power grid through a filter.

4. The grid-connected application circuit of the three-phase five-level inverter as described in claim 3, characterized in that, The filters include L-type filters, LC-type filters, and LCL-type filters.

5. The grid-connected application circuit of the three-phase five-level inverter as described in claim 3 or 4, characterized in that, The grid-connected application circuit also includes a DC / DC converter. The input terminal of the DC / DC converter is connected to a photovoltaic panel or an energy storage battery, and the output terminal is connected to the input side of a three-phase five-level inverter.

6. An off-grid application circuit for a three-phase five-level inverter, characterized in that, The off-grid application circuit includes an LC filter and a three-phase five-level inverter as described in any one of claims 1-2; wherein... The DC input source of the three-phase five-level inverter is a DC power supply, and the AC output of the three-phase five-level inverter is connected to a purely resistive load through an LC filter.

7. An off-grid application circuit for a three-phase five-level inverter, characterized in that, The off-grid application circuit includes an L-filter and a three-phase five-level inverter as described in any one of claims 1-2; wherein... The DC input source of the three-phase five-level inverter is a DC power supply, and the AC output of the three-phase five-level inverter is connected to the motor through an L filter.

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