Multistage breakdown circuit for power device and control method thereof

Abstract

The invention provides a multi-stage breakdown circuit for a power device and a control method of the multi-stage breakdown circuit, and relates to the technical field of power conversion. The multi-stage breakdown circuit comprises a positive power supply, a monostable switch, a normally-open switch, a first resistor and n transient voltage suppression diodes, the cathode of the first transient voltage suppression diode is connected with the collector of the power device, and a normally-closed contact of the monostable switch is connected in parallel to the two ends of the cathode of the mth transient voltage suppression diode and the anode of the nth transient voltage suppression diode; and the anode of the first diode is connected with the anode of the nth transient voltage suppression diode, and the cathode of the zth diode is connected with the grid electrode of the power device. The multi-stage breakdown circuit is simple in structure, the control method is simple and reliable, if the control power supply works abnormally, the action voltage of the transient voltage suppression diode connected in series is reduced through the monostable switch, a power device is forced to enter an active working area as soon as possible for breakdown short circuit, and the passive breakdown reliability is improved.

Description

Technical Field

[0001] The present application relates to the technical field of power conversion, and in particular to a multi-level breakdown circuit for a power device and a control method thereof. Background Art

[0002] The modular multilevel converter is composed of multiple cascaded power submodules with the same structure, which is particularly suitable for the field of high-voltage, large-capacity flexible direct current transmission. In order to prevent the failure of the cascaded power submodule from affecting the normal operation of the system, the equipment needs to reliably and promptly complete the bypass operation of the faulty power submodule. Therefore, the power submodules of the converter need to be equipped with bypass switches, and the industry has done a lot of research on improving the reliability of bypass switches.

[0003] However, the reliability of the bypass switch depends on the reliability of the power supply, and there is a risk of the bypass switch mechanism failing to operate. Patent CN110829811A "An MMC power module overvoltage protection circuit and multi-stage bypass method" solves the bypass protection problem of the power submodule after the bypass switch fails to operate by adding thyristors, but the addition of thyristors will increase the cost and volume weight of the power submodule; Patent CN202211028553.9 "Converter valve submodule bypass failure protection method, device, equipment and medium" and CN202111167946.3 "Valve unit and converter valve system with fault protection function" propose to bypass the power submodule by turning on the power device to form a direct failure, but the direct short-circuit method still relies on the reliability of the power supply, and the failure energy is relatively large, and it will cause serious fragmentation of the power semiconductor device, and may even threaten the normal operation of the adjacent modules. Summary of the invention

[0004] In order to solve at least one of the above problems, the present application proposes a multi-level breakdown circuit for a power device and a control method thereof.

[0005] According to the first aspect of the present application, at least one embodiment of the present application provides a multi-stage breakdown circuit for a power device, comprising: a positive power supply, the negative electrode of the positive power supply is connected to the emitter of the power device; a monostable switch, the monostable switch includes a normally open contact and a normally closed contact; a normally open switch; a first resistor, the positive electrode of the positive power supply, the normally open contact of the monostable switch, the normally open switch and the first resistor are sequentially connected in series, and then connected to the gate of the power device; n transient voltage suppression diodes, connected in series with each other, n is an integer greater than or equal to 2, wherein the n transient voltage suppression diodes The cathode of a first transient voltage suppression diode among the n transient voltage suppression diodes is connected to the collector of the power device, and the normally closed contact of the monostable switch is connected in parallel to the cathode of the mth transient voltage suppression diode and the anode of the nth transient voltage suppression diode among the n transient voltage suppression diodes; z diodes are connected in series with each other, z is an integer greater than or equal to 1, the anode of a first diode among the z diodes is connected to the anode of the nth transient voltage suppression diode among the n transient voltage suppression diodes, and the cathode of the zth diode among the z diodes is connected to the gate of the power device.

[0006] For example, in some embodiments of the present application, the positive power supply includes an adjustable voltage source.

[0007] For example, in some embodiments of the present application, the normally open switch includes a MOS tube or an IGBT.

[0008] For example, in some embodiments of the present application, the device further includes: a capacitor connected in parallel with the gate and the emitter of the power device; and a second resistor connected in parallel with the capacitor.

[0009] According to the second aspect of the present application, at least one embodiment of the present application provides a control method for a multi-stage breakdown circuit of a power device, which is used to control the multi-stage breakdown circuit as described in any one of the first aspects, including: judging whether the power device is working normally; when the power device is working normally, controlling the normally open contact of the monostable switch to be closed and the normally closed contact to be opened; adjusting the voltage amplitude of the positive power supply to the control voltage amplitude of the saturation working area of ​​the power device; controlling the normally open switch to be closed so that the positive power supply charges the gate of the power device, so that the power device enters the saturation working area.

[0010] For example, in some embodiments of the present application, it also includes: when the power device is abnormal and needs to be broken down, determining whether the positive power supply is working normally.

[0011] For example, in some embodiments of the present application, the power sub-module includes at least two power devices connected in series and a capacitor connected in parallel with the two power devices connected in series, and the control method also includes: when the positive power supply is operating normally, determining whether the capacitor voltage of the power sub-module exceeds the action voltage of the transient voltage suppression diode connected in series.

[0012] For example, in some embodiments of the present application, it also includes: when the capacitor voltage of the power sub-module does not exceed the action voltage of the transient voltage suppression diode connected in series, controlling the normally open contact of the monostable switch to close and the normally closed contact to open; adjusting the voltage amplitude of the positive power supply to the control voltage amplitude of the active working area of ​​the power device; controlling the normally open switch to close so that the positive power supply charges the gate of the power device, so that the power device enters the active working area, and the power device overheats and breaks down to short-circuit.

[0013] For example, in some embodiments of the present application, it also includes: when the capacitor voltage of the power sub-module exceeds the action voltage of the transient voltage suppression diode connected in series, the transient voltage suppression diode connected in series charges the gate of the power device; the normally open contact of the monostable switch is controlled to be closed and the normally closed contact is opened; the voltage amplitude of the positive power supply is adjusted to the control voltage amplitude of the active working area of ​​the power device; the normally open switch is controlled to be closed so that the positive power supply charges the gate of the power device, so that the power device enters the active working area, and the power device overheats and breaks down to short-circuit.

[0014] For example, in some embodiments of the present application, it also includes: when the positive power supply operates abnormally, controlling the normally open contact of the monostable switch to be disconnected and the normally closed contact to be closed; reducing the action voltage of the transient voltage suppression diode connected in series to a first preset voltage, so that when the voltage between the collector and the emitter of the power device exceeds the first preset voltage, the transient voltage suppression diode connected in series charges the gate of the power device, the power device enters the active working area, and the power device overheats and breaks down to short-circuit.

[0015] Through the above example embodiments, the present application provides a multi-stage breakdown circuit for power devices and a control method thereof: when the bypass switch cannot bypass, if the control power supply works normally, the power device can be actively controlled to enter the active working area to achieve control and adjustment of the breakdown threshold, and at a lower voltage, the power device can be short-circuited and broken down, reducing the short-circuit energy impact and avoiding threats to adjacent modules; if the control power supply works abnormally, the action voltage of the series transient voltage suppression diode is reduced through the monostable switch, forcing the power device to enter the active working area as soon as possible to break down the short circuit, thereby improving the reliability of passive breakdown. The multi-stage breakdown circuit has a simple structure, a simple and reliable control method, and does not require the addition of other power devices. It can improve the reliability of fault bypass of power submodules in the field of high-voltage direct current transmission and ensure reliable operation of the system.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] By describing in detail exemplary embodiments thereof with reference to the accompanying drawings, the above and other objects, features and advantages of the present application will become more apparent. The accompanying drawings described below are only some embodiments of the present application, and are not intended to limit the present application.

[0018] Figure 1 A schematic diagram of a multi-level breakdown circuit for a power device according to an exemplary embodiment is shown;

[0019] Figure 2a The first embodiment shows an exemplary multi-level breakdown circuit arranged in a power submodule;

[0020] Figure 2b A second embodiment showing an exemplary multi-level breakdown circuit arranged in a power submodule;

[0021] Figure 3 A flow chart showing a control method for a multi-level breakdown circuit of a power device according to an exemplary embodiment. DETAILED DESCRIPTION

[0022] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0023] The described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of these specific details, or other modes, components, materials, devices, etc. may be adopted. In these cases, known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0024] The flowcharts shown in the accompanying drawings are only exemplary and do not necessarily include all the contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps can be decomposed, and some operations / steps can be combined or partially combined, so the actual execution order may change according to actual conditions.

[0025] The terms "first", "second", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0026] Those skilled in the art will appreciate that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present application, and therefore cannot be used to limit the scope of protection of the present application.

[0027] Figure 1 A schematic diagram of a multi-level breakdown circuit for a power device according to an exemplary embodiment is shown.

[0028] like Figure 1 As shown, a multi-stage breakdown circuit 10 for a power device includes: a positive power supply VCC, a monostable switch K1, a normally open switch K2, a first resistor R1, n transient voltage suppression diodes T1...Tn, connected in series with each other, and z diodes D1...Dz, connected in series with each other. n is an integer greater than or equal to 2, and z is an integer greater than or equal to 1.

[0029] According to an exemplary embodiment, the power device in the present application takes IGBT as an example, but the present application is not limited thereto.

[0030] Among them, the negative electrode of the positive power supply VCC is connected to the emitter of the power device (not shown in the figure). The monostable switch K1 includes a normally open contact K1a and a normally closed contact K1b. The positive electrode of the positive power supply VCC, the normally open contact K1a of the monostable switch, the normally open switch K2 and the first resistor R1 are connected in series in sequence, and then connected to the gate of the power device. The cathode of the first transient voltage suppression diode T1 among the n transient voltage suppression diodes is connected to the collector of the power device, and the normally closed contact K1b of the monostable switch is connected in parallel to the cathode of the mth transient voltage suppression diode Tm and the anode of the nth transient voltage suppression diode Tn among the n transient voltage suppression diodes. The anode of the first diode D1 among the z diodes is connected to the anode of the nth transient voltage suppression diode Tn among the n transient voltage suppression diodes, and the cathode of the zth diode Dz among the z diodes is connected to the gate of the power device.

[0031] According to some embodiments, the positive power supply VCC includes an adjustable voltage source.

[0032] According to some embodiments, the normally open switch K2 includes a MOS tube or an IGBT.

[0033] According to some embodiments, the series action voltage value of transient voltage suppression diodes is determined according to the operating conditions and withstand voltage of the power device, and then the number of series connections is determined according to the action value of a selected single transient voltage suppression diode.

[0034] According to an example embodiment, the multi-level breakdown circuit further includes a capacitor C1 and a second resistor R2.

[0035] The capacitor C1 is connected in parallel with the gate and the emitter of the power device. The second resistor R2 is connected in parallel with the capacitor C1.

[0036] like Figure 2a and Figure 2b As shown, at least one power device equipped with a multi-stage breakdown circuit is connected in parallel to the AC port of the power submodule. The power submodule can be any one of a half-bridge structure, a full-bridge structure, or a hybrid structure formed by connecting a full-bridge and a half-bridge.

[0037] like Figure 2a As shown, when the power submodule is a half-bridge structure, two power devices are connected in series and then connected in parallel at both ends of the DC capacitor C2. An AC port is formed between the midpoints of the series-connected power devices and the negative electrode of the DC energy storage capacitor, and the multi-stage breakdown circuit 10 is arranged on the power device of the AC port. The bypass switch K3 is connected in parallel to the AC port.

[0038] like Figure 2bAs shown, when the power submodule is a full-bridge structure, two groups of two power devices are connected in series and then connected in parallel at both ends of the DC capacitor C2. Among them, an AC port is formed between the midpoints of the two groups of power devices connected in series, and the bypass switch K3 is connected in parallel to the AC port. The multi-stage breakdown circuit 10 is arranged on the power device of the AC port. When the power submodule abnormally needs to be bypassed, but the bypass switch K3 fails to bypass, the multi-stage breakdown circuit 10 can achieve a breakdown short circuit of the power device of the AC port and bypass the faulty power submodule. The multi-stage breakdown circuit 10 can be arranged in a cascade topology including but not limited to a half-bridge or full-bridge structure, and arranged on the power device of the AC port, which can serve as the last line of defense for bypass protection of the power submodule.

[0039] The present application can control the degree and time of a power device entering an active working region and a saturated working region by adjusting the power supply voltage.

[0040] Figure 3 A flow chart showing a control method for a multi-level breakdown circuit of a power device according to an exemplary embodiment.

[0041] like Figure 3 As shown, the control method for the multi-stage breakdown circuit of the power device includes steps S301-S304. According to different operating conditions of the power submodule, the control method of the multi-stage breakdown circuit of the power device of the present application is described. According to the characteristics of the power device, the control voltage amplitude of the saturated working area of ​​the power device is V1, and the control voltage amplitude of the active working area of ​​the power device is V2 as an example:

[0042] In step S301, it is determined whether the power device operates normally.

[0043] When the power device is operating normally, the process proceeds to step S3011 ; when the power device is abnormal and needs to be broken down, the process proceeds to step S302 .

[0044] Working condition 1: When the power device is switched normally:

[0045] In step S3011, the normally open contact of the monostable switch is controlled to be closed, and the normally closed contact is controlled to be opened.

[0046] In step S3012, the voltage amplitude of the positive power supply is adjusted to a control voltage amplitude V1 in the saturation operating region of the power device.

[0047] In step S3013, the normally open switch is controlled to be closed.

[0048] The normally open switch is controlled to close so that the positive power supply charges the gate of the power device, causing the power device to enter a saturation operating region.

[0049] When the power device is abnormal and needs to be broken down, the process proceeds to step S302 .

[0050] According to some embodiments, the power sub-module may be directly bypassed by closing the bypass switch without breaking down the power device.

[0051] In step S302, it is determined whether the positive power supply is operating normally.

[0052] When the positive power supply works normally, go to step S303; when the positive power supply works abnormally, go to step S304.

[0053] In step S303 , it is determined whether the capacitor voltage of the power submodule exceeds the operating voltage Vnz of the transient voltage suppressor diode connected in series.

[0054] When the capacitor voltage of the power submodule exceeds the action voltage of the transient voltage suppression diode connected in series, go to step S3031; when the capacitor voltage of the power submodule does not exceed the action voltage of the transient voltage suppression diode connected in series, go to step S3032.

[0055] Among them, the capacitance of the power submodule is Figure 2a and Figure 2b The DC capacitor C2 in.

[0056] Working condition 2: when the power device needs to be broken down, and the first positive power supply works normally, the capacitor voltage of the power submodule exceeds the action voltage of the transient voltage suppression diode connected in series:

[0057] In step S3031, the series-connected transient voltage suppressor diode charges the gate of the power device.

[0058] In step S3032, the normally open contact of the monostable switch is controlled to be closed, and the normally closed contact is controlled to be opened.

[0059] In step S3033, the voltage amplitude of the positive power supply is adjusted to the control voltage amplitude V2 of the active working area of ​​the power device.

[0060] In step S3034, the normally open switch is controlled to close.

[0061] The normally open switch is controlled to close so that the positive power supply charges the gate of the power device, causing the power device to enter the active working area, and the power device overheats and breaks down to short-circuit.

[0062] According to the example embodiment, the only difference between operating condition 3 and operating condition 2 is that the capacitor voltage of the power submodule does not exceed the action voltage of the transient voltage suppression diode connected in series. In this case, there is no need to use the transient voltage suppression diode connected in series to charge the gate of the power device, and step S3032 can be directly executed.

[0063] Working condition 4: when the power device needs to be broken down and the first positive power supply is working abnormally:

[0064] In step S304, the normally open contact of the monostable switch is controlled to be opened, and the normally closed contact is controlled to be closed.

[0065] In step S3041 , the operating voltage of the series-connected transient voltage suppressor diodes is reduced to a first preset voltage.

[0066] The action voltage Vnz of the transient voltage suppression diode connected in series is reduced to the first preset voltage Vmz, so that when the voltage between the collector and the emitter of the power device exceeds the first preset voltage Vmz, the transient voltage suppression diode connected in series charges the gate of the power device, the gate voltage of the power device rises, the power device enters the active working area, and the power device overheats and breaks down to short-circuit.

[0067] The present application provides a multi-stage breakdown circuit for power devices and a control method thereof: when the bypass switch cannot bypass, if the control power supply works normally, the power device can be actively controlled to enter the active working area to achieve control and adjustment of the breakdown threshold, and at a lower voltage, the power device can be short-circuited and broken down, reducing the short-circuit energy impact and avoiding threats to adjacent modules; if the control power supply works abnormally, the action voltage of the series transient voltage suppression diode is reduced through the monostable switch, forcing the power device to enter the active working area as soon as possible to break down the short circuit, thereby improving the reliability of passive breakdown. The multi-stage breakdown circuit has a simple structure, a simple and reliable control method, and does not require the addition of other power devices. It can improve the reliability of fault bypass of power submodules in the field of high-voltage direct current transmission and ensure reliable operation of the system.

[0068] It should be clearly understood that the present application describes how to form and use specific examples, but the present application is not limited to any details of these examples. On the contrary, based on the teaching of the content disclosed in the present application, these principles can be applied to many other embodiments.

[0069] In addition, it should be noted that the above figures are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, and are not intended to be limiting. It is easy to understand that the processes shown in the above figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0070] The exemplary embodiments of the present application are specifically shown and described above. It should be understood that the present application is not limited to the detailed structures, configurations or implementations described herein; on the contrary, the present application is intended to cover various modifications and equivalent configurations included in the spirit and scope of the appended claims.

Claims

1. A multi-stage breakdown circuit for a power device, characterized in that: include: A positive power supply, wherein a negative electrode of the positive power supply is connected to an emitter of the power device; A monostable switch, wherein the monostable switch comprises a normally open contact and a normally closed contact; Normally open switch; A first resistor, a positive electrode of the positive power supply, a normally open contact of the monostable switch, the normally open switch and the first resistor are sequentially connected in series, and then connected to the gate of the power device; n transient voltage suppression diodes are connected in series with each other, where n is an integer greater than or equal to 2, wherein the cathode of a first transient voltage suppression diode among the n transient voltage suppression diodes is connected to the collector of the power device, and the normally closed contact of the monostable switch is connected in parallel to the cathode of an mth transient voltage suppression diode and the anode of an nth transient voltage suppression diode among the n transient voltage suppression diodes; z diodes are connected in series with each other, z is an integer greater than or equal to 1, an anode of a first diode among the z diodes is connected to an anode of an nth transient voltage suppression diode among the n transient voltage suppression diodes, and a cathode of a zth diode among the z diodes is connected to a gate of the power device.

2. The multi-stage breakdown circuit according to claim 1, characterized in that: The positive power supply includes an adjustable voltage source.

3. The multi-stage breakdown circuit according to claim 1, characterized in that: The normally open switch includes a MOS tube or an IGBT.

4. The multi-stage breakdown circuit according to claim 1, characterized in that: Also includes: A capacitor is connected in parallel with the gate and the emitter of the power device. A second resistor is connected in parallel with the capacitor.

5. A control method for a multi-stage breakdown circuit of a power device, characterized in that: Used to control the multi-stage breakdown circuit according to any one of claims 1 to 4, comprising: Determining whether the power device is operating normally; When the power device is operating normally, the normally open contact of the monostable switch is controlled to be closed and the normally closed contact is controlled to be disconnected; Adjusting the voltage amplitude of the positive power supply to a control voltage amplitude of a saturation operating region of the power device; The normally open switch is controlled to be closed so that the positive power supply charges the gate of the power device, so that the power device enters a saturation working region.

6. The control method according to claim 5, characterized in that: Also includes: In the case where the power device is abnormal and needs to be broken down, it is determined whether the positive power supply operates normally.

7. The control method according to claim 6, characterized in that: The power submodule includes at least two power devices connected in series and a capacitor connected in parallel with the two power devices connected in series, and the control method further includes: When the positive power supply operates normally, it is determined whether the capacitor voltage of the power submodule exceeds the action voltage of the transient voltage suppression diode connected in series.

8. The control method according to claim 7, characterized in that: Also includes: When the capacitor voltage of the power submodule does not exceed the action voltage of the transient voltage suppression diode connected in series, the normally open contact of the monostable switch is controlled to be closed and the normally closed contact is controlled to be opened; Adjusting the voltage amplitude of the positive power supply to the control voltage amplitude of the active working area of ​​the power device; The normally open switch is controlled to be closed so that the positive power supply charges the gate of the power device, so that the power device enters the active working area, and the power device overheats and breaks down to short-circuit.

9. The control method according to claim 7, characterized in that: Also includes: When the capacitor voltage of the power submodule exceeds the action voltage of the transient voltage suppression diode connected in series, the transient voltage suppression diode connected in series charges the gate of the power device; Controlling the normally open contact of the monostable switch to close and the normally closed contact to open; Adjusting the voltage amplitude of the positive power supply to the control voltage amplitude of the active working area of ​​the power device; The normally open switch is controlled to be closed so that the positive power supply charges the gate of the power device, so that the power device enters the active working area, and the power device overheats and breaks down to short-circuit.

10. The control method according to claim 6, characterized in that: Also includes: When the positive power supply works abnormally, the normally open contact of the monostable switch is controlled to be disconnected and the normally closed contact is controlled to be closed; The action voltage of the transient voltage suppression diode connected in series is reduced to a first preset voltage, so that when the voltage between the collector and the emitter of the power device exceeds the first preset voltage, the transient voltage suppression diode connected in series charges the gate of the power device, the power device enters the active working area, and the power device overheats and breaks down to short-circuit.

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