A three-phase four-leg nine-level converter

Abstract

This application provides a three-phase four-leg nine-level converter. The converter includes leg A, leg B, leg C, and leg n, and the structures of the four legs are the same. Each leg is connected to the load through an inductor and a filter capacitor. Leg A includes ten power electronic switching tubes, two power diodes, two DC bus capacitors, and two flying capacitors. Compared with traditional nine-level converters, the number of power electronic switching tubes in this application is greatly reduced, and the complexity of the multi-level converter is greatly reduced. At the same time, this invented device can maintain higher power quality under both unbalanced and nonlinear operating conditions, and is applicable to balanced and unbalanced loads. It has good application prospects in medium- and high-voltage new energy power generation systems.

Description

Technical Field

[0001] The present application relates to the technical field of converters, and particularly to a three-phase four-leg nine-level converter. Background Art

[0002] Multilevel inverters have received extensive attention in the fields of new energy power generation systems and motor drive applications due to advantages such as lower common-mode voltage, smaller voltage stress on switching tubes, and lower distortion in output voltage and current, and have become a research hotspot for scholars at home and abroad. The most common topological structures of multilevel converters mainly have three types: diode-clamped type, flying-capacitor type, and cascaded H-bridge type.

[0003] Compared with converters of other different topological structures, the diode-clamped three-level converter has been widely used in new energy power generation and motor drive. However, when the number of output levels of the diode-clamped multilevel converter topology exceeds three, due to the sharp increase in the number of clamping diodes and switching tubes required, the structure of the multilevel converter becomes complex.

[0004] The flying-capacitor multilevel converter uses capacitors instead of diodes for clamping and outputs multiple voltage waveforms through the balancing capacitors between each phase bus. When the number of output levels of the converter exceeds three, a large number of clamping capacitors are also required, and the problem of balancing the voltages of each capacitor on the DC side will also become complex and difficult to control.

[0005] The cascaded H-bridge multilevel converter requires many isolated power supplies, which makes the topological structure of the cascaded H-bridge multilevel converter more complex.

[0006] In order to address issues such as fossil energy shortages and environmental pollution, the country strongly advocates the use of clean and pollution-free energy such as solar energy and wind energy. As a result, converters, which are devices for realizing power conversion and the interface between loads and the power grid, have also been vigorously developed. With the widespread application of unbalanced and nonlinear loads, traditional three-phase three-leg converters are not suitable for unbalanced loads. Summary of the Invention

[0007] Aiming at the problems of traditional three-phase multilevel converters, the present application proposes a novel three-phase four-leg nine-level converter, which combines a diode-clamped multilevel converter and a flying-capacitor multilevel converter.

[0008] Based on the above purpose, the present application proposes a three-phase four-leg nine-level converter, including:

[0009] The converter includes leg A, leg B, leg C, and leg n, and the structures of the four legs are the same.

[0010] Further, each leg is connected to a load through an inductor and a filter capacitor.

[0011] Further, the A arm includes a first power electronic switch, a second power electronic switch, a third power electronic switch, a fourth power electronic switch, a fifth power electronic switch, a sixth power electronic switch, a seventh power electronic switch, an eighth power electronic switch, a ninth power electronic switch, a tenth power electronic switch, a first power diode, a second power diode, a first DC bus capacitor, a second DC bus capacitor, a first flying capacitor, and a second flying capacitor.

[0012] Further, the drain of the first power electronic switch is connected to the positive P point of the input power supply, and the source of the first power electronic switch is connected to the drain of the second power electronic switch at point P a1 point, and the source of the second power electronic switch is connected to the drain of the third power electronic switch at point P a2 point.

[0013] Further, the source of the third power electronic switch is connected to the drain of the fourth power electronic switch S a4 at point O, the cathode of the first power diode Da1 is connected to point P a2 point, and the anode of the first power diode Da1 is connected to point O.

[0014] Further, the source of the fourth power electronic switch is connected to the drain of the fifth power electronic switch at point Na2, the cathode of the second power diode is connected to point O, and the anode of the second power diode is connected to point Na2.

[0015] Further, the source of the fifth power electronic switch is connected to the drain of the sixth power electronic switch at point Na1, and the source of the sixth power electronic switch is connected to point N.

[0016] Further, the source of the seventh power electronic switch is connected to the drain of the eighth power electronic switch at the output terminal A, the drain of the seventh power electronic switch is connected to point P a1 point, and the source of the eighth power electronic switch is connected to point Na1.

[0017] Further, the source of the ninth power electronic switch is connected to the drain of the tenth power electronic switch, the drain of the ninth power electronic switch is connected to point O a1 point, and the drain of the tenth power electronic switch is connected to the output terminal A.

[0018] Further, one end of the first DC bus filter capacitor is connected to point A, the other end is connected to point O, one end of the second DC bus filter capacitor is connected to point O, the other end is connected to point N, and one end of the first flying capacitor is connected to P a1One end is connected to point Oa1, and the other end is connected to point Oa1. One end of the second flying capacitor is connected to point Oa1, and the other end is connected to point Na1.

[0019] Generally speaking, the advantages of this application and the experience brought to users are as follows:

[0020] Compared with the traditional nine-level converter, the number of power electronic switching tubes is greatly reduced, and the complexity of the multi-level converter is greatly reduced. At the same time, this invented device adds an additional bridge arm on the basis of the traditional three-phase three-bridge-arm converter. The midpoint of the bridge arm is connected to the load neutral point to provide a path for zero-sequence current and control the neutral point voltage, so that the converter can maintain higher power quality under unbalanced and non-linear operating conditions and is applicable to balanced and unbalanced loads. Therefore, the invented three-phase four-bridge-arm nine-level converter has good application prospects in medium- and high-voltage new energy power generation systems. Brief Description of the Drawings

[0021] In the drawings, unless otherwise specified, the same reference numerals throughout the several views denote the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in this application and should not be regarded as limiting the scope of this application.

[0022] Figure 1 Shows the schematic structural diagram of the three-phase four-bridge-arm nine-level converter of this application.

[0023] Figure 2 Shows the structural diagram of the A bridge arm of the three-phase four-bridge-arm nine-level converter according to an embodiment of this application.

[0024] Figure 3 Shows the schematic diagram of the output V1 state of the A bridge arm of the three-phase four-bridge-arm nine-level converter according to an embodiment of this application.

[0025] Figure 4 Shows the schematic diagram of the output V2 state of the A bridge arm of the three-phase four-bridge-arm nine-level converter according to an embodiment of this application.

[0026] Figure 5 Shows the schematic diagram of the output V3 state of the A bridge arm of the three-phase four-bridge-arm nine-level converter according to an embodiment of this application.

[0027] Figure 6 Shows the schematic diagram of the output V4 state of the A bridge arm of the three-phase four-bridge-arm nine-level converter according to an embodiment of this application.

[0028] Figure 7 Shows the schematic diagram of the output V5 state of the A bridge arm of the three-phase four-bridge-arm nine-level converter according to an embodiment of this application.

[0029] Figure 8Shows the schematic diagram of the output V6 state of the A arm of the three-phase four-leg nine-level converter according to an embodiment of the present application.

[0030] Figure 9 Shows the schematic diagram of the output V7 state of the A arm of the three-phase four-leg nine-level converter according to an embodiment of the present application.

[0031] Figure 10 Shows the schematic diagram of the output V8 state of the A arm of the three-phase four-leg nine-level converter according to an embodiment of the present application.

[0032] Figure 11 Shows the schematic diagram of the output V9 state of the A arm of the three-phase four-leg nine-level converter according to an embodiment of the present application.

[0033] Figure 12 Shows the schematic diagram of the output V10 state of the A arm of the three-phase four-leg nine-level converter according to an embodiment of the present application.

[0034] Figure 13 Shows the schematic diagram of the output V11 state of the A arm of the three-phase four-leg nine-level converter according to an embodiment of the present application.

[0035] Figure 14 Shows the schematic diagram of the output V12 state of the A arm of the three-phase four-leg nine-level converter according to an embodiment of the present application. Detailed implementation mode

[0036] The present application will be further described in detail below with reference to the drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the related invention, rather than limiting the invention. Additionally, it should be noted that for the convenience of description, only the parts related to the relevant invention are shown in the drawings.

[0037] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and embodiments.

[0038] The topological structure of the novel three-phase four-leg nine-level converter device of the present application is as Figure 1 shown. The converter is composed of an A arm, a B arm, a C arm, and an n arm, and the structures of the four arms are the same. Each phase arm of the three-phase four-leg nine-level conversion device is connected to the load through an inductor L and a filter capacitor C. The structural diagram of the A arm of the novel three-phase four-leg nine-level conversion device is as Figure 2 shown. It can be seen from Figure 2 that the A arm is composed of power electronic switch tubes S a1 , power electronic switch tubes S a2 , power electronic switch tubes S a3 , power electronic switch tubes S a4 , power electronic switch tubes Sa5 , power electronic switch tube S a6 , power electronic switch tube S a7 , power electronic switch tube S a8 , power electronic switch tube S a9 , power electronic switch tube S a10 , power diodes Da1, Da2, and DC bus capacitor C d1 , DC bus capacitor C d2 , flying capacitor C a1 , flying capacitor C a2 is composed of. The drain of power electronic switch tube S a1 is connected to the positive P point of the input power supply. The source of power electronic switch tube S a1 is connected to the drain of power electronic switch tube S a2 at point P a1 . The source of power electronic switch tube S a2 is connected to the drain of power electronic switch tube S a3 at point P a2 . The source of power electronic switch tube S a3 is connected to the drain of power electronic switch tube S a4 at point O. The cathode of power diode Da1 is connected to point P a2 . The anode of power diode Da1 is connected to point O. The source of power electronic switch tube S a4 is connected to the drain of power electronic switch tube S a5 at point Na2. The cathode of power diode Da2 is connected to point O. The anode of power diode Da2 is connected to point Na2. The source of power electronic switch tube S a5 is connected to the drain of power electronic switch tube S a6 at point Na1. The source of power electronic switch tube S a6 is connected to point N. The source of power electronic switch tube S a7 is connected to the drain of power electronic switch tube S a8 at the output terminal A. The drain of power electronic switch tube S a7 is connected to point P a1 . The source of power electronic switch tube S a8 is connected to point Na1. The source of power electronic switch tube S a9 is connected to the drain of power electronic switch tube S a10 . The drain of power electronic switch tube S a9 is connected to point O a1 . The drain of power electronic switch tube S a10 is connected to the output terminal A. One end of the DC bus filter capacitor C d1 is connected to point A, and the other end is connected to point O. One end of the DC bus filter capacitor C d2One end is connected to point O, and the other end is connected to point N, with flying capacitor C a1 One end is connected to P a1 point, and the other end is connected to point Oa1, with flying capacitor C a2 One end is connected to point Oa1, and the other end is connected to point Na1.

[0039] The output voltage and switching states of arm A of the three-phase four-leg nine-level converter are shown in Table 1. Among them, the DC input capacitor voltage C d1 and the input capacitor voltage C d2 are controlled to be 4Vdc / 8, and the flying capacitor C a1 and the flying capacitor C a2 voltage is controlled to be Vdc / 8. In the table, "1" represents the conduction of the power electronic switch tube, and "0" represents the turn-off of the power electronic switch tube. It can be seen from Table 1 that the arm A of the three-phase four-leg nine-level converter outputs nine different levels: -4Vdc / 8, -3Vdc / 8, -2Vdc / 8, -Vdc / 8, 0, Vdc / 8, 2Vdc / 8, 3Vdc / 8, 4Vdc / 8, greatly improving the performance of the converter.

[0040] Switching state V1: Power electronic switches S a1 , S a5 , S a7 conduct, and power electronic switches S a2 , S a3 , S a4 , S a6 , S a7 , S a9 , S a10 turn off. The output V1 state of arm A of the three-phase four-leg nine-level converter is as Figure 3 shown.

[0041] Switching state V2: Power electronic switches S a1 , S a5 , S a9 , S a10 conduct, and power electronic switches S a2 , S a3 , S a4 , S a6 , S a7 , S a8 turn off. The output V2 state of arm A of the three-phase four-leg nine-level converter is as Figure 4 shown.

[0042] Switching state V3: Power electronic switches S a1 , S a5 , S a8 conduct, and power electronic switches S a2 , S a3 , S a4, S a6 , S a7 , S a9 , S a10 Turn off. The output V3 state of the A arm of the three-phase four-leg nine-level converter is as shown in Figure 5 .

[0043] Switch state V4: The power electronic switches S a3 , S a4 , S a5 , S a7 Turn on. The power electronic switches S a1 , S a2 , S a4 , S a6 , S a8 , S a9 , S a10 Turn off. The output V4 state of the A arm of the three-phase four-leg nine-level converter is as shown in Figure 6 .

[0044] Switch state V5: The power electronic switches S a3 , S a4 , S a5 , S a9 , S a10 Turn on. The power electronic switches S a1 , S a2 , S a6 , S a7 , S a8 Turn off. The output V5 state of the A arm of the three-phase four-leg nine-level converter is as shown in Figure 7 .

[0045] Switch state V6: The power electronic switches S a3 , S a4 , S a5 , S a8 Turn on. The power electronic switches S a1 , S a2 , S a6 , S a7 , S a9 , S a10 Turn off. The output V6 state of the A arm of the three-phase four-leg nine-level converter is as shown in Figure 8 .

[0046] Switch state V7: The power electronic switches S a2 , S a3 , S a4 , S a7 Turn on. The power electronic switches S a1 , S a5 , S a6 , S a8 , Sa9 and S a10 is turned off. The output V7 state of arm A of the three-phase four-leg nine-level converter is as Figure 9 shown.

[0047] Switch state V8: Power electronic switches S a2 and S a3 and S a4 and S a9 and S a10 are turned on, and power electronic switches S a1 and S a5 and S a6 and S a7 and S a8 are turned off. The output V8 state of arm A of the three-phase four-leg nine-level converter is as Figure 10 shown.

[0048] Switch state V9: Power electronic switches S a2 and S a3 and S a4 and S a8 are turned on, and power electronic switches S a1 and S a5 and S a6 and S a7 and S a9 and S a10 are turned off. The output V9 state of arm A of the three-phase four-leg nine-level converter is as Figure 11 shown.

[0049] Switch state V10: Power electronic switches S a2 and S a3 and S a4 and S a8 are turned on, and power electronic switches S a1 and S a5 and S a6 and S a7 and S a9 and S a10 are turned off. The output V10 state of arm A of the three-phase four-leg nine-level converter is as Figure 12 shown.

[0050] Switch state V11: Power electronic switches S a2 and S a6 and S a9 and S a10 are turned on, and power electronic switches S a1 and S a3 and S a4 and S a5 and S a7 and S a8 are turned off. The output V11 state of arm A of the three-phase four-leg nine-level converter is asFigure 13 as shown

[0051] Switch state V12: The power electronic switch S a2 , S a6 , S a8 turns on, and the power electronic switches S a1 , S a3 , S a4 , S a5 , S a7 , S a9 , S a10 turns off, and the output V12 state of the A arm of the three-phase four-leg nine-level converter is as Figure 14 shown

[0052] Table 1 Output voltage of the A arm of the three-phase four-leg nine-level converter and switch state

[0053]

[0054] It should be noted that

[0055] In the specification provided herein, a large number of specific details are described. However, it can be understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known methods, structures, and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0056] Similarly, it should be understood that, in order to streamline the present application and assist in understanding one or more of the various inventive aspects, in the above description of the exemplary embodiments of the present application, the various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting an intention that the claimed present application requires more features than are expressly recited in each claim. Rather, as reflected by the following claims, the inventive aspects lie in less than all of the features of the single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into the detailed description, where each claim stands on its own as a separate embodiment of the present application.

[0057] Those skilled in the art can understand that the modules in the devices in the embodiments can be adaptively changed and arranged in one or more devices different from those of the embodiments. The modules or units or components in the embodiments can be combined into one module or unit or component, and in addition, they can be divided into multiple sub-modules or sub-units or sub-components. Except that at least some of such features and / or processes or units are mutually exclusive, any combination can be used to combine all the features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all the processes or units of any method or device so disclosed. Unless otherwise explicitly stated, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) can be replaced by an alternative feature that provides the same, equivalent, or similar purpose.

[0058] In addition, those skilled in the art can understand that although some of the embodiments described herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of this application and forms different embodiments. For example, in the following claims, any one of the claimed embodiments can be used in any combination.

[0059] It should be noted that the above embodiments illustrate the present application rather than limit the present application, and those skilled in the art can design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present application can be implemented by means of hardware including several different elements and by means of a properly programmed computer. In the unit claims listing several systems, several of these systems can be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words can be interpreted as names.

[0060] As described above, this is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of various changes or substitutions within the technical scope disclosed by the present application, and these should all be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claimed claims.

Claims

1. A three-phase four-leg nine-level converter, characterized in that the converter includes leg A, leg B, leg C and leg n, and the structures of the four legs are the same; leg A includes a first power electronic switch, a second power electronic switch, a third power electronic switch, a fourth power electronic switch, a fifth power electronic switch, a sixth power electronic switch, a seventh power electronic switch, an eighth power electronic switch, a ninth power electronic switch, a tenth power electronic switch, a first power diode, a second power diode, a first DC bus capacitor, a second DC bus capacitor, a first flying capacitor, and a second flying capacitor; The drain of the first power electronic switch tube is connected to the positive electrode P point of the input power supply, and the source of the first power electronic switch tube is connected to the drain of the second power electronic switch tube at point P a1 point, and the source of the second power electronic switch tube is connected to the drain of the third power electronic switch tube at point P a2 point; The source electrode of the third power electronic switch tube is connected to the drain electrode of the fourth power electronic switch tube at point O, and the cathode of the first power diode is connected to point P a2 point, and the anode of the first power diode is connected to point O; The source electrode of the fourth power electronic switch tube is connected to the drain electrode of the fifth power electronic switch tube at point N a2 The cathode of the second power diode is connected to point O, and the anode of the second power diode is connected to point N a2 point; The source electrode of the fifth power electronic switch tube is connected to the drain electrode of the sixth power electronic switch tube at point N a1 The source electrode of the sixth power electronic switch tube is connected to point N; The source of the seventh power electronic switch tube is connected to the drain of the eighth power electronic switch tube at the output terminal point A, and the drain of the seventh power electronic switch tube is connected to point P a1 point, and the source of the eighth power electronic switch tube is connected to point N a1 point; The source electrode of the ninth power electronic switch tube is connected to the drain electrode of the tenth power electronic switch tube, and the drain electrode of the ninth power electronic switch tube is connected to point O a1 The drain electrode of the tenth power electronic switch tube is connected to the output terminal at point A; One end of the first DC bus capacitor is connected to point P, and the other end is connected to point O. One end of the second DC bus capacitor is connected to point O, and the other end is connected to point N. One end of the first flying capacitor is connected to point P a1 point, and the other end is connected to point O a1 point. One end of the second flying capacitor is connected to point O a1 point, and the other end is connected to point N a1 point.

2. The three-phase four-leg nine-level converter according to claim 1, characterized in that each leg is connected to the load through an inductor and a filter capacitor.

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