Nine-level t-type inverter and application thereof

Abstract

This invention provides a nine-level T-type inverter and its application, characterized by comprising: a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, and an eighth switch. Multiple capacitors are used as voltage sources, and the on / off states of the switches are selectively controlled to generate different voltage source paths, thereby achieving multi-level output. In summary, this method can achieve multi-level output and improve power quality.

Description

Technical Field

[0001] This invention relates to an inverter, specifically a nine-level T-type inverter, and a long-distance power transmission device using the nine-level T-type inverter. Background Technology

[0002] Underground power systems in coal mines are crucial infrastructure for coal production, and their stability and efficiency directly impact the safety and economic benefits of the mine. As mining depth increases, the underground power load and transmission distance also increase, placing higher technical demands on power transmission equipment. However, existing underground power transmission systems in coal mines still face numerous technical challenges in achieving efficient long-distance power transmission.

[0003] The underground environment in coal mines is complex, characterized by high humidity, high dust levels, high temperatures, and flammable and explosive conditions, requiring power transmission equipment to possess high environmental adaptability. Meanwhile, voltage loss and harmonic interference in transmission lines are also major technical bottlenecks for long-distance power transmission underground.

[0004] High voltage loss: Due to the long transmission distance, traditional power transmission equipment suffers high losses under heavy load conditions, making it difficult to maintain a stable output voltage.

[0005] Harmonic interference: Underground power grids in coal mines typically have a wide variety of loads, resulting in severe harmonic pollution. This affects the normal operation of electrical equipment and increases the risk of equipment failure.

[0006] Currently, long-distance power transmission in coal mines mainly uses traditional two-level or three-level inverters in conjunction with transmission transformers for AC power transmission. This method has the following problems:

[0007] High voltage stress: In traditional two-level and three-level inverters, each switching device needs to withstand the full DC bus voltage, resulting in high device losses and large electromagnetic interference.

[0008] High harmonic content: The output voltage waveform of two-level or three-level topologies is relatively poor, requiring complex filters to meet the harmonic standards of coal mine power grids.

[0009] Insufficient equipment reliability: In the high humidity, high temperature and flammable and explosive underground environment, the power devices of traditional inverters are prone to failure during long-term operation, affecting the continuity of power supply from the grid.

[0010] In summary, existing underground power transmission systems in coal mines still suffer from inefficiency in long-distance power transmission. Summary of the Invention

[0011] This invention was made to solve the above-mentioned problems, and its purpose is to provide a nine-level T-type inverter and its application.

[0012] This invention provides a nine-level T-type inverter for outputting nine different voltages, characterized by comprising: a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, and an eighth switch. One end of the first capacitor is connected to one end of the first switch; the other end of the first switch is connected to one end of the second switch, one end of the third capacitor, and one end of the sixth switch; the other end of the second switch is connected to one end of the third switch and one end of the fourth switch; the other end of the third switch is connected to one end of the fifth switch, one end of the fourth capacitor, and one end of the seventh switch; the other end of the fifth switch is connected to one end of the second capacitor; the other end of the second capacitor is connected to the other end of the first capacitor and the other end of the fourth switch; the other end of the sixth switch is connected to the other end of the seventh switch and one end of the eighth switch; the other end of the eighth switch is connected to the other end of the third capacitor and the other end of the fourth capacitor; one end of the first capacitor and one end of the second capacitor are connected to the positive and negative terminals of the input voltage, respectively; one end of the eighth switch is used for the output voltage; and the other end of the fourth switch is grounded.

[0013] The nine-level T-type inverter provided by this invention may also have the following features: the voltage of the first capacitor and the second capacitor is 4E, the voltage of the third capacitor and the fourth capacitor is E, and the nine different voltages are +4E, +3E, +2E, +E, 0, -1E, -2E, -3E and -4E.

[0014] The nine-level T-type inverter provided by this invention may also have the following characteristics: when the first, third, and sixth switches are turned on, the output voltage is +4E; when the first, third, and eighth switches are turned on, the output voltage is +3E; when the first, third, and seventh switches are turned on, the output voltage is +2E; when the third, fourth, and eighth switches are turned on, the output voltage is +E; when the third, fourth, and seventh switches are turned on, the output voltage is 0; when the second, fourth, and eighth switches are turned on, the output voltage is -E; when the second, fourth, and seventh switches are turned on, the output voltage is -2E; when the second, fifth, and eighth switches are turned on, the output voltage is -3E; and when the second, fifth, and seventh switches are turned on, the output voltage is -4E.

[0015] The nine-level T-type inverter provided by this invention may also have the following feature: wherein the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch and the eighth switch are all power switching transistors.

[0016] The nine-level T-type inverter provided by this invention may also have the following feature: wherein the power switching transistors include IGBTs and MOSFETs.

[0017] This invention also provides a long-distance power transmission device for providing three-phase AC power to a load device at a long distance, characterized by comprising: an input DC power supply module for performing DC voltage grading on the input high-voltage DC to generate a multi-level DC input voltage; an inverter module including three sets of nine-level T-type inverters for generating three-phase AC power based on the multi-level DC input voltage; a power filtering module for filtering out high-frequency harmonics of the three-phase AC power to obtain high-quality three-phase AC power; and a long-distance power transmission module for transmitting the high-quality three-phase AC power to the load device, wherein the three sets of nine-level T-type inverters respectively generate stepped waveforms for phases A, B, and C, and the nine-level T-type inverter is the nine-level T-type inverter of any one of claims 1 to 4.

[0018] The long-distance power transmission device provided by the present invention may also have the following feature: wherein the power filtering module includes a low-pass filter containing an inductor and a capacitor, and the low-pass filter filters out high-frequency harmonics by smoothing the stepped waveform.

[0019] The role and effect of invention

[0020] According to the nine-level T-type inverter and its application of the present invention, by setting multiple capacitors as voltage sources and selectively controlling the on / off states of the switches, different voltage source paths are generated to achieve multi-level output, thereby reducing the harmonic content in the output waveform and improving power quality. Furthermore, it can improve the accuracy of the output voltage, making the voltage stress distribution more uniform. Therefore, the nine-level T-type inverter and its application of the present invention can achieve multi-level output and improve power quality. Attached Figure Description

[0021] Figure 1 This is a block diagram of a long-distance power transmission device in an embodiment of the present invention;

[0022] Figure 2 This is a circuit diagram of a nine-level T-type inverter in an embodiment of the present invention;

[0023] Figure 3 This is a schematic diagram illustrating the process of a long-distance power transmission device supplying power to a load device in an embodiment of the present invention. Detailed Implementation

[0024] To make the technical means, creative features, objectives and effects of this invention easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the nine-level T-type inverter of this invention and its applications.

[0025] This embodiment provides a long-distance power transmission device for long-distance power transmission in coal mines, that is, to provide three-phase AC power to load equipment in coal mines over long distances, which can meet the power supply requirements of line voltage of 1140V and reactive power of 500kVAR or 1000kVAR.

[0026] Figure 1 This is a block diagram of a long-distance power transmission device in an embodiment of the present invention.

[0027] like Figure 1 As shown, the long-distance power transmission device 100 includes an input DC power supply module 11, an inverter module 12, a power filter module 13, and a long-distance power transmission module 14.

[0028] The input DC power supply module 11 performs DC voltage grading on the input high-voltage DC to generate a multi-level DC input voltage.

[0029] In this embodiment, the input DC power module 11 generates multiple DC levels through voltage-dividing capacitors or a tiered DC bus, and forms a multi-level DC input voltage through a multi-stage DC bus or a group of voltage-dividing capacitors. Each voltage level node is implemented by multiple capacitors connected in series or in parallel to ensure a stable DC input voltage.

[0030] Inverter module 12 includes three sets of nine-level T-type inverters that generate three-phase AC power based on multi-level DC input voltage.

[0031] The three sets of nine-level T-type inverters generate stepped waveforms for phases A, B, and C, respectively. The phase difference between phases A, B, and C is 120°, and the total harmonic distortion (THD) of the output waveform of the nine-level T-type inverter is less than 1%.

[0032] Figure 2 This is a circuit diagram of a nine-level T-type inverter in an embodiment of the present invention.

[0033] like Figure 2 As shown, the nine-level T-type inverter 200 includes a first capacitor C1, a second capacitor C2, and a third capacitor C... fx1 Fourth capacitor C fx2 The switches are: first switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, sixth switch S6, seventh switch S7, and eighth switch S8.

[0034] In this embodiment, the first switch S1, the second switch S2, the third switch S3, the fifth switch S5, the sixth switch S6, and the seventh switch S7 are each composed of a transistor and a diode. The collector of the transistor is connected to the negative terminal of the diode, and the emitter is connected to the positive terminal of the diode.

[0035] In this embodiment, the fourth switch S4 and the eighth switch S8 are composed of two transistors and two diodes. The collector of one transistor is connected to the cathode of one diode, the emitter of the transistor is connected to the anode of the diode, the emitter of the other transistor, and the anode of the other diode, respectively, and the collector of the other transistor is connected to the cathode of the other diode.

[0036] In other embodiments, power switching transistors are selected as the first switch S1, the second switch S2, the third switch S3, the fourth switch S4, the fifth switch S5, the sixth switch S6, the seventh switch S7, and the eighth switch S8 as needed. Further, the power switching transistors include IGBTs and MOSFETs.

[0037] One end of the first capacitor C1 is connected to one end of the first switch S1, which is the negative terminal of the corresponding diode.

[0038] The other end of the first switch S1, i.e., the positive terminal of the corresponding diode, is connected to one end of the second switch S2, i.e., the negative terminal of the corresponding diode, and the third capacitor C. fx1 One end of the diode is connected to one end of the sixth switch S6, which is the negative terminal of the corresponding diode.

[0039] The other end of the second switch S2, i.e., the positive terminal of the corresponding diode, is connected to one end of the third switch S3, i.e., the negative terminal of the corresponding diode, and one end of the fourth switch S4, i.e., the negative terminal of the corresponding diode.

[0040] The other end of the third switch S3, i.e., the positive terminal of the corresponding diode, is connected to one end of the fifth switch S5, i.e., the negative terminal of the corresponding diode, and the fourth capacitor C. fx2 One end of the diode is connected to one end of the seventh switch S7, which is the positive terminal of the corresponding diode.

[0041] The other end of the fifth switch S5, which is the positive terminal of the corresponding diode, is connected to one end of the second capacitor C2.

[0042] The other end of the second capacitor C2 is connected to the other end of the first capacitor C1 and the other end of the fourth switch S4, which is the negative terminal of the corresponding diode.

[0043] The other end of the sixth switch S6, i.e. the positive terminal of the corresponding diode, is connected to the other end of the seventh switch S7, i.e. the negative terminal of the corresponding diode, and one end of the eighth switch S8, i.e. the negative terminal of the corresponding diode.

[0044] The other end of the eighth switch S8, which is the cathode of the corresponding other diode, is connected to the third capacitor C. fx1 The other end and the fourth capacitor C fx2 The other end is connected.

[0045] One end of the first capacitor C1 and one end of the second capacitor C2 are connected to the positive and negative terminals of the input voltage, respectively. One end of the eighth switch S8 is used for the output voltage. The other end of the fourth switch S4 is grounded.

[0046] Among them, the voltage of the first capacitor C1 and the second capacitor C2 is 4E, and the voltage of the third capacitor C... fx1 and the fourth capacitor C fx2 The voltages are all E. The nine-level T-type inverter 200 outputs voltages with different levels: +4E, +3E, +2E, +E, 0, -1E, -2E, -3E, and -4E. The specific correspondence between switch on / off states and voltage levels is as follows:

[0047] When the first switch S1, the third switch S3, and the sixth switch S6 are turned on, the current i out Starting from point O, the circuit passes through the first capacitor C1, the first switch S1, and the sixth switch S6 in sequence, resulting in an output voltage of +4E.

[0048] When the first switch S1, the third switch S3, and the eighth switch S8 are turned on, the current i out Starting from point O, pass sequentially through the first capacitor C1, the first switch S1, and the third capacitor C. fx1 And the eighth switch S8, so that the output voltage is +3E.

[0049] When the first switch S1, the third switch S3, and the seventh switch S7 are turned on, the current i out Starting from point O, pass sequentially through the first capacitor C1, the first switch S1, and the third capacitor C. fx1 Fourth capacitor C fx2 And the seventh switch S7, so that the output voltage is +2E.

[0050] When the third switch S3, the fourth switch S4, and the eighth switch S8 are turned on, the current i out Starting from point O, pass through the fourth switch S4, the third switch S3, and the fourth capacitor C in sequence. fx2 And the eighth switch S8, so that the output voltage is +E.

[0051] When the third switch S3, the fourth switch S4, and the seventh switch S7 are turned on, the current i out Starting from point O, the circuit passes through the fourth switch S4, the third switch S3, and the seventh switch S7 in sequence, resulting in an output voltage of 0.

[0052] When the second switch S2, the fourth switch S4, and the eighth switch S8 are turned on, the current i out Starting from point O, pass through the fourth switch S4, the second switch S2, and the third capacitor C in sequence. fx1 And the eighth switch S8, so that the output voltage is -E.

[0053] When the second switch S2, the fourth switch S4, and the seventh switch S7 are turned on, the current i out Starting from point O, pass through the fourth switch S4, the second switch S2, and the third capacitor C in sequence. fx1 Fourth capacitor C fx2 And the seventh switch S7, so that the output voltage is -2E.

[0054] When the second switch S2, the fifth switch S5, and the eighth switch S8 are turned on, the current i out Starting from point O, pass sequentially through the second capacitor C2, the fifth switch S5, and the fourth capacitor C. fx2 And the eighth switch S8, so that the output voltage is -3E.

[0055] When the second switch S2, the fifth switch S5, and the seventh switch S7 are turned on, the current i out Starting from point O, the circuit passes through the second capacitor C2, the fifth switch S5, and the seventh switch S7 in sequence, resulting in an output voltage of -4E.

[0056] The power filtering module 13 filters out high-frequency harmonics in the three-phase AC power to obtain high-quality three-phase AC power.

[0057] The power filtering module 13 includes a low-pass filter containing an inductor and a capacitor. The low-pass filter filters out high-frequency harmonics by smoothing the stepped waveform.

[0058] The long-distance power transmission module 14 delivers high-quality three-phase AC power to the load equipment. In this embodiment, the long-distance power transmission module 14 uses low-loss three-phase AC power transmission technology, combined with optimized insulation and protection measures, to ensure efficient power transmission at a line voltage of 1140V.

[0059] The following description, in conjunction with the accompanying drawings, illustrates the process of supplying power to load equipment using a long-distance power transmission device 100.

[0060] Figure 3 This is a schematic diagram illustrating the process of a long-distance power transmission device supplying power to a load device in an embodiment of the present invention.

[0061] like Figure 3 As shown, the long-distance power transmission device 100 supplies power to the load equipment through the following steps:

[0062] Step S1: The input DC power supply module 11 is used to perform DC voltage grading on the input high voltage DC to generate a multi-level DC input voltage.

[0063] Step S2: The inverter module 12 generates three-phase AC power based on the multi-level DC input voltage.

[0064] Step S3: The power filter module 13 is used to filter out the high-frequency harmonics of the three-phase AC power to obtain high-quality three-phase AC power.

[0065] Step S4: High-quality three-phase AC power is transmitted to the load equipment using the long-distance power transmission module 14.

[0066] The role and effect of the embodiments

[0067] Based on the nine-level T-type inverter and its application described in this embodiment, by setting multiple capacitors as voltage sources and selectively controlling the on / off states of the switches, different voltage source paths are generated to achieve multi-level output, thereby reducing the harmonic content in the output waveform and improving power quality. Furthermore, it can improve the accuracy of the output voltage, resulting in a more uniform voltage stress distribution. In summary, this method can achieve multi-level output and improve power quality.

[0068] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A nine-level T-type inverter for outputting nine different voltages, characterized by, include: First capacitor, second capacitor, third capacitor, fourth capacitor, first switch, second switch, third switch, fourth switch, fifth switch, sixth switch, seventh switch, and eighth switch. One end of the first capacitor is connected to one end of the first switch. The other end of the first switch is connected to one end of the second switch, one end of the third capacitor, and one end of the sixth switch, respectively. The other end of the second switch is connected to one end of the third switch and one end of the fourth switch, respectively. The other end of the third switch is connected to one end of the fifth switch, one end of the fourth capacitor, and one end of the seventh switch, respectively. The other end of the fifth switch is connected to one end of the second capacitor. The other end of the second capacitor is connected to the other end of the first capacitor and the other end of the fourth switch, respectively. The other end of the sixth switch is connected to the other end of the seventh switch and one end of the eighth switch, respectively. The other end of the eighth switch is connected to the other end of the third capacitor and the other end of the fourth capacitor, respectively. One end of the first capacitor and one end of the second capacitor are respectively connected to the positive and negative terminals of the input voltage. One end of the eighth switch is used to output the voltage. The other end of the fourth switch is grounded.

2. The nine-level T-type inverter according to claim 1, characterized in that: wherein The voltage across both the first capacitor and the second capacitor is 4E. The voltage of both the third capacitor and the fourth capacitor is E. The nine different voltages are +4E, +3E, +2E, +E, 0, -1E, -2E, -3E, and -4E.

3. The nine-level T-type inverter of claim 2, Its features are: When the first switch, the third switch, and the sixth switch are turned on, the output voltage is +4E; When the first switch, the third switch, and the eighth switch are turned on, the output voltage is +3E; When the first switch, the third switch, and the seventh switch are turned on, the output voltage is +2E; When the third switch, the fourth switch, and the eighth switch are turned on, the output voltage is +E; When the third switch, the fourth switch, and the seventh switch are turned on, the output voltage is 0; When the second switch, the fourth switch, and the eighth switch are turned on, the output voltage is -E; When the second switch, the fourth switch, and the seventh switch are turned on, the output voltage is -2E; When the second switch, the fifth switch, and the eighth switch are turned on, the output voltage is -3E; When the second switch, the fifth switch, and the seventh switch are turned on, the output voltage is -4E.

4. The nine-level T-type inverter according to claim 1, characterized in that: wherein The first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch, the seventh switch, and the eighth switch are all power switching transistors.

5. The nine-level T-type inverter according to claim 4, characterized in that: wherein, The power switching transistors include IGBTs and MOSFETs.

6. A long distance power transmission apparatus for supplying three-phase alternating current to a load device at a long distance, characterized by comprising: include: The input DC power supply module performs DC voltage grading on the input high-voltage DC to generate multi-level DC input voltage; The inverter module includes three sets of nine-level T-type inverters, which generate three-phase AC power according to the multi-level DC input voltage. The power filtering module filters out high-frequency harmonics in the three-phase AC power to obtain high-quality three-phase AC power. The long-distance power transmission module delivers the high-quality three-phase AC power to the load device. The three sets of nine-level T-type inverters respectively generate stepped waveforms for phases A, B, and C. The nine-level T-type inverter is the nine-level T-type inverter as described in any one of claims 1 to 4.

7. The long-distance power transmission device according to claim 6, characterized in that: wherein The power filtering module includes a low-pass filter comprising an inductor and a capacitor. The low-pass filter smooths the stepped waveform and filters out the high-frequency harmonics.

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