Single-phase multi-level current source inverter capable of preventing open circuit of inductor

Abstract

The invention provides an inductor open circuit prevention single-phase multi-level current source inverter, and relates to the technical field of multi-level inverters, the inductor open circuit prevention single-phase multi-level current source inverter comprises a plurality of inductor sub-modules, each inductor sub-module comprises an inductor, and each inductor is reversely connected in parallel with a power diode; one end of each inductance sub-module is connected with a power supply anode, and the other end is connected in series with a power switch and a power diode; the plurality of inductance sub-modules are connected in parallel, then connected in series with an H-bridge converter circuit and then connected to the negative electrode of the power supply; a load is connected between bridge arms of the H-bridge type converter circuit, and current is provided for the load through a switch combination strategy based on a power switch. On one hand, fewer IGBT devices are provided, the production cost is reduced, on the other hand, the fault-tolerant capability of open-circuit faults is provided, and the reliability is higher.

Description

Technical Field

[0001] The present invention belongs to the technical field of multi-level inverters, and in particular relates to a single-phase multi-level current source inverter capable of preventing inductor open circuit. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] Inverters can be divided into voltage source inverters (VSI) and current source inverters (CSI) according to the DC side power supply form. Compared with voltage source inverters, current source inverters have better performance in terms of circuit reliability and resistance to DC short circuit faults. In industrial fields such as medium voltage drive and motor control, current source inverters have been widely used. On this basis, in order to reduce the current stress of power devices and improve the output power quality of the inverter, multi-level current source inverters are often used in high-power scenarios.

[0004] The topology of the traditional single-phase five-level current source inverter is as follows: Figure 1 As shown. In general, the circuit includes a DC voltage source and two parallel converter modules. Each converter module consists of an inductor and a single-phase bridge circuit. The single-phase bridge circuit integrates four IGBTs and four power diodes, where each IGBT is connected in series with a power diode. This traditional topology solution faces some inherent disadvantages: on the one hand, it is sensitive to open circuits, and the inductor is prone to induce high voltages at both ends due to misoperation or open circuit failure of the IGBT, thereby damaging the circuit; on the other hand, the number of IGBTs and power diodes is large, so the power density and construction cost of the circuit are not ideal.

[0005] Inductors have the physical property of suppressing sudden changes in current, so they can allow transient short circuits in the circuit, but correspondingly, the branch in which they are located is very sensitive to open circuits. During the commutation process of traditional current source inverters, once the circuit is in an open circuit working state, ultra-high voltage spikes will be generated on both sides of the inductor, causing circuit damage. To address this problem, traditional single-phase five-level current source inverters usually rely on setting the overlap time of the IGBT to prevent the bridge arm from opening through software modulation, but the circuit currently still lacks simple and effective means to deal with abnormal conditions such as switch malfunction or damage. Summary of the invention

[0006] In order to solve the above problems, the present disclosure proposes a single-phase multi-level current source inverter with anti-inductive open circuit. On the one hand, it has fewer IGBT devices, which reduces production costs and reduces the possibility of switch misoperation or damage. On the other hand, it has open circuit fault tolerance and higher reliability.

[0007] In order to achieve the above objectives, the present disclosure provides the following technical solutions:

[0008] A single-phase multi-level current source inverter for preventing inductor open circuit includes a plurality of inductor submodules, each of which includes an inductor, and each inductor is reversely connected in parallel with a power diode;

[0009] One end of each inductor module is connected to the positive pole of the power supply, and the other end is connected in series with a power switch and a power diode;

[0010] A plurality of inductor modules are connected in parallel, and then connected in series to an H-bridge converter circuit and then connected to the negative pole of the power supply;

[0011] The load is connected between the bridge arms of the H-bridge converter circuit, and current is provided to the load through a switch combination strategy based on a power switch.

[0012] Preferably, the H-bridge converter circuit is composed of four IGBTs and four power diodes, one IGBT and one power diode are connected in series as a combination, and two combinations of IGBTs and power diodes are connected in series on the bridge arm of each H-bridge converter circuit;

[0013] A load is connected between the combination of the IGBT and the power diode on each bridge arm.

[0014] Preferably, the switch combination strategy specifically includes:

[0015] When the power switch in a certain inductor submodule is closed and turned on, the power supply passes through the inductance of the inductor submodule, supplies energy to the filter and load components through the power switch, and the current returns to the DC power supply; when the power switch is disconnected, the inductance of the inductor submodule forms a closed loop through the reverse-parallel power diode and enters the freewheeling state.

[0016] Preferably, the single-phase multi-level current source inverter has different levels according to the number of inductor modules connected in parallel;

[0017] When the structure is a parallel connection of two inductor submodules, the single-phase multi-level current source inverter is a single-phase five-level current source inverter. When the structure is a parallel connection of three inductor submodules, the single-phase multi-level current source inverter is a single-phase seven-level current source inverter.

[0018] Preferably, the power diode connected in reverse parallel with the inductor provides a freewheeling path for the inductor, and the remaining power diodes are connected in series with the IGBT to provide reverse blocking capability for each IGBT.

[0019] Preferably, the single-phase multi-level current source inverter is a single-phase five-level current source inverter, and the inverter output current is a five-level current, which is respectively ±2I d , ±I d and 0.

[0020] Preferably, the single-phase multi-level current source inverter is a single-phase five-level current source inverter, the inverter output current is a five-level current, and the current of each branch where the inductor submodule is located is set to I d , the switch working status of the inverter is as follows:

[0021] When the first power switch, the fourth power switch, the fifth power switch and the sixth power switch are turned on and the rest are turned off, the output current is 2I d ;

[0022] When the fifth power switch or the sixth power switch is turned on, and the first power switch and the fourth power switch are turned on, and the others are turned off, the output current is I d ;

[0023] When the fifth power switch or the sixth power switch is turned on, and the second power switch and the third power switch are turned on, and the others are turned off, the output current is -I d ;

[0024] When the second power switch, the third power switch, the fifth power switch and the sixth power switch are turned on and the others are turned off, the output current is -2I d ;

[0025] When the first power switch and the third power switch are turned on, or the second power switch and the fourth power switch are turned on, or the fifth power switch and the sixth power switch are turned off, the output current is zero.

[0026] Preferably, the AC voltage amplitude of the inverter is always smaller than the DC power supply voltage value.

[0027] Preferably, the power diodes connected in anti-parallel with the inductor have the same rated parameters.

[0028] Preferably, multiple inductor sub-modules are configured with the same rated parameters to provide a constant DC current for each branch.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present disclosure provides a single-phase multi-level current source inverter that prevents inductor open circuit. Through the anti-parallel structure of the inductor and the power diode, the problem of preventing inductor open circuit can be directly solved from the hardware structure aspect, which can effectively improve the fault tolerance capability of the device to cope with open circuit faults.

[0031] (2) The single-phase multi-level current source inverter proposed in the present disclosure is resistant to inductive open circuit, and the number of power semiconductor devices is significantly less than that of the traditional topology solution. Under the same condition of outputting 2k+1 level, the traditional topology solution requires 4k IGBTs and 4k power diodes, while the single-phase multi-level current source inverter proposed in the present disclosure only requires 4+k IGBTs and 4+2k power diodes. With fewer power semiconductor devices, the possibility of open circuit failure is reduced. At the same time, since power semiconductor devices are the core hardware of the power electronic inverter, they directly affect the cost and working reliability of the overall equipment. Therefore, the solution proposed in the present disclosure has positive significance in terms of equipment cost and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0033] Figure 1 This is the topology diagram of a traditional single-phase five-level current source inverter;

[0034] Figure 2 It is a topology diagram of a traditional single-phase multi-level current source inverter;

[0035] Figure 3 It is a topology diagram of a single-phase multi-level current source inverter for preventing inductor open circuit disclosed in the present invention;

[0036] Figure 4 This is a topology diagram of a single-phase five-level current source inverter that prevents inductor open circuit disclosed in the present invention. DETAILED DESCRIPTION

[0037] The present disclosure is further described below in conjunction with the accompanying drawings and embodiments.

[0038] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0039] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0040] In the present disclosure, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present disclosure, and do not specifically refer to any part or element in the present disclosure and should not be understood as limitations on the present disclosure.

[0041] In the present disclosure, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. For relevant scientific research or technical personnel in this field, the specific meanings of the above terms in the present disclosure can be determined according to specific circumstances, and they cannot be understood as limitations on the present disclosure.

[0042] First, the professional terms involved in this disclosure are explained:

[0043] Inverter: It is a power electronic conversion device that converts direct current into alternating current.

[0044] Current source inverter: An inverter whose DC side power is in the form of a constant current source. In engineering, it is usually constructed by connecting a voltage source in series with an inductor. This type of inverter needs to always keep the inductor loop closed and is more sensitive to open circuit faults.

[0045] Multi-level current source inverter: The AC side of the inverter approaches a sine wave by outputting a stepped current waveform, so it is usually easier to filter and has better power quality.

[0046] Embodiment 1

[0047] like Figure 3As shown, this embodiment proposes a single-phase multi-level current source inverter that prevents inductor open circuit, including multiple inductor sub-modules, each of which includes an inductor, and each inductor is reverse-connected in parallel with a power diode to provide a freewheeling path for the inductor, which can directly solve the problem of inductor open circuit from the hardware structure aspect, and can effectively improve the fault tolerance of the equipment to cope with open circuit faults. One end of each inductor sub-module is connected to the positive pole of the power supply, and the other end is connected in series with a power switch and a power diode; after multiple inductor sub-modules are connected in parallel, an H-bridge converter circuit is connected in series and then connected to the negative pole of the power supply. The load is connected between the bridge arms of the H-bridge converter circuit, and current is provided to the load through a switch combination strategy based on the power switch.

[0048] Among them, the H-bridge converter circuit is composed of four IGBTs and four power diodes, one IGBT and one power diode are connected in series as a combination, and two combinations of IGBTs and power diodes are connected in series on the bridge arm of each H-bridge converter circuit; a load is connected between the combination of IGBTs and power diodes on each bridge arm.

[0049] The power diode connected in reverse parallel with the inductor provides a freewheeling path for the inductor, while the remaining power diodes are connected in series with the IGBT to provide reverse blocking capability for each IGBT to prevent the AC side filter from being short-circuited.

[0050] Switch combination strategy, including:

[0051] When the power switch in a certain inductor submodule is closed and turned on, the power supply passes through the inductance of the inductor submodule, supplies energy to the filter and load components through the power switch, and the current returns to the DC power supply; when the power switch is disconnected, the inductance of the inductor submodule forms a closed loop through the reverse-parallel power diode and enters the freewheeling state.

[0052] The single-phase multi-level current source inverter has different levels depending on the number of inductor modules connected in parallel;

[0053] When the structure is a parallel connection of two inductor submodules, the single-phase multi-level current source inverter is a single-phase five-level current source inverter. When the structure is a parallel connection of three inductor submodules, the single-phase multi-level current source inverter is a single-phase seven-level current source inverter.

[0054] Due to the presence of anti-parallel power diodes at both ends of the inductor, the charging / discharging operation rules of the inductor are opposite to those of the traditional single-phase five-level current source inverter, which requires that the AC voltage amplitude of the inverter is always smaller than the DC power supply voltage value.

[0055] The power diodes connected in reverse parallel with the inductor have the same rated parameters. The multiple inductor submodules are configured with the same rated parameters to provide a constant DC current for each branch.

[0056] like Figure 2 As shown, the traditional single-phase multi-level current source inverter is usually constructed by connecting several H-bridge converter modules in parallel. In order to obtain 2k+1 level current on the AC side, the traditional topology solution requires k H-bridge converter modules in parallel. That is, the traditional topology solution requires 4k IGBTs and 4k power diodes under the condition of outputting 2k+1 level, while the present disclosure only requires 4+k IGBTs and 4+2k power diodes. Under the same condition of outputting 2k+1 level, the technical solution of the present disclosure requires fewer power semiconductor devices, and the possibility of open circuit failure is smaller. Since the power semiconductor device is the core hardware of the power electronic inverter, it directly affects the cost and working reliability of the overall equipment. Therefore, the solution proposed in the present disclosure has positive significance in terms of equipment cost and reliability.

[0057] For ease of understanding, the present disclosure takes a single-phase five-level current source inverter as an example for detailed description. Figure 4 As shown, the single-phase multi-level current source inverter is a single-phase five-level current source inverter, and the inverter output current is a five-level current, which is ±2I d , ±I d and 0. The circuit components include a DC power supply (E), two inductor modules and an H-bridge converter circuit.

[0058] In each inductor submodule, the inductor and a power diode form an anti-parallel structure, which is then connected in series with an IGBT and a power diode; the H-bridge converter circuit consists of four IGBTs (S 1 ~S 4 ) and four power diodes (D 1 ~D 4 ) in the whole circuit. There are two inductors (L 1 , L 2 ), six IGBTs (S 1 ~S 6 ) and eight power diodes (D 1 ~D 8 ). Power diode D 6 , D 8 The main function is to 1 , L 2 It provides a freewheeling path for the inductor, thereby preventing the occurrence of an inductor open circuit in hardware; the remaining power diodes are connected in series with the IGBT and are responsible for providing reverse blocking capability for each IGBT.

[0059] Assume that the current flowing through each inductor is I d , then S 5 , S 6 , D 5 ~D 8The rated current is I d , and S 1 ~S 4 , D 1 ~D 4 The rated current is 2I d Based on this, the inverter can configure the IGBT and power diode differently, thereby further reducing the cost of the overall equipment while reducing the IGBT.

[0060] In terms of commutation mechanism, S 5 , S 6 Used to manage the inductor current of its branch, S 1 ~S 4 Responsible for providing the necessary flow loop for the filter and load components. The operating principle is as follows: 5 The inductor module is used as an example to illustrate (assuming that S 1 , S 4 Both are in closed conduction state): When S 5 When closed, the power supply E passes through L 1 , via S 5 and D 5 , S 1 and D 1 Supply energy to the filter and load components, the current from S 4 and D 4 Return to the negative terminal of the direct source; when S 5 When disconnected, the inductor L 1 By D 6 A closed loop is formed and the continuous current state is entered. Similarly, S 6 The inductor module can also be connected through S 6 The on and off operation makes the inductor L 2 Works in charging and freewheeling states. Overall, the circuit can provide ±2I for the AC load through the combination of the on-off operation of six IGBTs. d ±I d , 0, a total of five currents, thus achieving five-level inversion. Specifically, the switch working state of the circuit is shown in Table 1. Based on the commutation modulation principle and the set switch working state, by executing the pulse width modulation (PWM) strategy, a five-level output current can be obtained at the AC port.

[0061] Table 1: Switching state table of the single-phase five-level current source inverter proposed in the present disclosure

[0062]

[0063] It is understandable that, according to the same construction method, other embodiments can also realize a single-phase seven-level current source inverter through a parallel structure of three inductor modules, which will not be described in detail in the present invention.

[0064] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0065] Although the above describes the specific implementation methods of the present disclosure in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present disclosure. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present disclosure, various modifications or variations that can be made by those skilled in the art without creative work are still within the scope of protection of the present disclosure.

Claims

1. A single-phase multi-level current source inverter with anti-inductor open circuit, characterized in that: It includes a plurality of inductor submodules, each of which includes an inductor, and each inductor is connected in reverse parallel with a power diode; One end of each inductor module is connected to the positive pole of the power supply, and the other end is connected in series with a power switch and a power diode; A plurality of inductor modules are connected in parallel, and then connected in series to an H-bridge converter circuit and then connected to the negative pole of the power supply; The bridge arms of the H-bridge current conversion circuit are connected to a load, and current is provided to the load through a switch combination strategy based on a power switch.

2. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 1, characterized in that: The H-bridge converter circuit is composed of four IGBTs and four power diodes, one IGBT and one power diode are connected in series to form a combination, and two IGBT and power diode combinations are connected in series on the bridge arm of each H-bridge converter circuit; A load is connected between the combination of the IGBT and the power diode on each bridge arm.

3. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 1, characterized in that: The switch combination strategy specifically includes: When the power switch in a certain inductor submodule is closed and turned on, the power supply passes through the inductance of the inductor submodule, supplies energy to the filter and load components through the power switch, and the current returns to the DC power supply; when the power switch is disconnected, the inductance of the inductor submodule forms a closed loop through the reverse-parallel power diode and enters the freewheeling state.

4. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 1, characterized in that: The single-phase multi-level current source inverter has different levels according to the number of inductor modules connected in parallel; When the structure is a parallel connection of two inductor submodules, the single-phase multi-level current source inverter is a single-phase five-level current source inverter. When the structure is a parallel connection of three inductor submodules, the single-phase multi-level current source inverter is a single-phase seven-level current source inverter.

5. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 2, characterized in that: The power diode connected in reverse parallel with the inductor provides a freewheeling path for the inductor, and the remaining power diodes are connected in series with the IGBT to provide reverse blocking capability for each IGBT.

6. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 4, characterized in that: The single-phase multi-level current source inverter is a single-phase five-level current source inverter, and the inverter output current is a five-level current, which is respectively ±2I d , ±I d and 0.

7. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 6, characterized in that: The single-phase multi-level current source inverter is a single-phase five-level current source inverter, the inverter output current is a five-level current, and the current of each branch where the inductor submodule is located is set to I d , the switch working state of the inverter is as follows: When the first power switch, the fourth power switch, the fifth power switch and the sixth power switch are turned on and the rest are turned off, the output current is 2I d ; When the fifth power switch or the sixth power switch is turned on, and the first power switch and the fourth power switch are turned on, and the others are turned off, the output current is I d ; When the fifth power switch or the sixth power switch is turned on, and the second power switch and the third power switch are turned on, and the others are turned off, the output current is -I d ; When the second power switch, the third power switch, the fifth power switch and the sixth power switch are turned on and the others are turned off, the output current is -2I d ; When the first power switch and the third power switch are turned on, or the second power switch and the fourth power switch are turned on, or the fifth power switch and the sixth power switch are turned off, the output current is zero.

8. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 1, characterized in that: The AC voltage amplitude of the inverter is always smaller than the DC power supply voltage value.

9. The single-phase multi-level current source inverter with inductive open circuit protection as claimed in claim 1, characterized in that: The power diodes connected in anti-parallel with the inductor have the same rated parameters.

10. The single-phase multi-level current source inverter with inductor open circuit protection as claimed in claim 1, characterized in that: The plurality of inductor submodules are configured with the same rated parameters to provide a constant direct current for each branch.

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