Controllable breakdown bypass protection circuit and method for IGCT-MMC submodule

Abstract

The invention provides a controllable breakdown bypass protection circuit and method for an IGCT-MMC sub-module, and relates to the technical field of flexible DC power transmission. The controllable breakdown bypass protection circuit comprises an overvoltage detection module which is connected with an IGCT-MMC sub-module and is used for detecting the voltage of a high-voltage capacitor and outputting an overvoltage signal under the condition that the voltage of the high-voltage capacitor is higher than a second set threshold value; the trigger module is connected with the overvoltage detection module and is used for receiving the overvoltage signal and outputting a control signal and conduction current; the IGCT gate pole driving module is respectively connected with the trigger module and the IGCT-MMC sub-module and is used for receiving the control signal, so that the conduction current is transferred to the IGCT-MMC sub-module, an IGCT device is conducted, and a bypass of the IGCT-MMC sub-module is realized; and the energy taking module is used for taking energy from the high-voltage capacitor of the IGCT-MMC sub-module and converting the energy into working voltage to realize power supply. According to the controllable breakdown bypass protection circuit provided by the invention, controllable breakdown bypass of the IGCT under the bypass switch failure can be realized, and the direct-current short-circuit fault loss is controlled in the sub-module.

Description

Technical Field

[0001] The present application relates to the field of flexible direct current transmission technology, and in particular to a controllable breakdown bypass protection circuit and method for an IGCT-MMC submodule. Background Art

[0002] With the development of power electronic devices, flexible DC transmission technology is currently regarded as an important way to solve the problem of ultra-long-distance and ultra-large capacity transmission. Modular multilevel converter (MMC) has outstanding advantages such as common DC terminal, excellent system harmonic characteristics, and low switching loss, and has a good application scenario in flexible DC transmission projects.

[0003] The rated voltage of power electronic devices is usually only at the kilovolt level, which cannot withstand the high voltage of high-voltage direct current transmission. Therefore, a single commutation bridge arm of a modular multilevel converter is usually composed of hundreds or thousands of power sub-modules connected in series. The power devices used in traditional modular multilevel converters are mainly IGBTs, which have a mature driving method, high switching frequency, and good self-shutdown characteristics. However, compared with the current-type power device IGCT, IGBT still has the disadvantages of complex process and low reliability.

[0004] IGCT is expected to significantly improve the performance of submodule multilevel converter valves in high-voltage and large-capacity flexible DC transmission due to its advantages of low manufacturing cost, compact structure, greater flow capacity, and higher blocking voltage. However, IGCT does not have desaturation characteristics, and its current shutoff capability is weak. When the control function of a single submodule fails, the power submodule enters an uncontrollable state, and the bridge arm current continues to charge the high-voltage capacitor, which can cause serious breakdown and vaporization of the capacitor, causing an explosion. The failure of a single power submodule expands to the surrounding submodules, seriously threatening the safety and reliability of the overall operation of the converter valve. Therefore, the fault bypass technology of the power submodule has become an important research direction of modular multilevel converter technology.

[0005] CN110739837A proposes an MMC power module with dual bypass switches and an overvoltage triple bypass method, which further improves the reliability of the power module by adding a redundant bypass switch, but still cannot avoid the problem of bypass switch mechanism refusing to operate; CN115377944A provides a modular multi-level converter submodule active breakdown bypass protection circuit and method, which realizes active bypass by actively breaking down the bypass module, but the control unit, energy extraction unit, and breakdown trigger unit inside the module are too broad and do not involve specific implementation methods; CN107026577B provides a circuit that can cut off DC short-circuit faults A modular multilevel converter for current is provided. By connecting a fast mechanical switch, an auxiliary electronic switch and an energy absorption capacitor in series in the submodule circuit, the submodule of the modular multilevel converter has the ability to self-cut off the DC fault current. However, the added fast mechanical switch and other devices are expensive, which greatly increases the cost of the converter. CN108616223B provides a modular multilevel converter and a fault handling method based on IGCT. By adding a buffer circuit in the power circuit, the requirements for the current carrying capacity of the equipment are reduced, and the reliability of the DC fault handling capability is improved. However, this method greatly increases the number of power devices of the converter, and the cost is still high.

[0006] Therefore, a more specific and implementable IGCT controllable breakdown bypass protection circuit and method is needed to solve the problem of bypass switch mechanism refusal to operate, while avoiding the cost problem caused by the increase of a large number of power devices. Summary of the invention

[0007] In order to solve at least one of the above problems, the present application proposes a controllable breakdown bypass protection circuit and method for an IGCT-MMC submodule.

[0008] According to the first aspect of the present application, at least one embodiment of the present application provides a controllable breakdown bypass protection circuit for an IGCT-MMC submodule, wherein the IGCT-MMC submodule includes an IGCT device and a high-voltage capacitor connected in series, and the controllable breakdown bypass protection circuit includes: an overvoltage detection module, connected to the IGCT-MMC submodule, for detecting the voltage of the high-voltage capacitor, and outputting an overvoltage signal when the voltage of the high-voltage capacitor is higher than a second set threshold; a trigger module, connected to the overvoltage detection module, for receiving the overvoltage signal, and outputting a control signal signal and conduction current; an IGCT gate drive module, which is respectively connected to the trigger module and the IGCT-MMC sub-module, and is used to receive the control signal so that the conduction current is transferred to the IGCT-MMC sub-module, so that the IGCT device is turned on, and the IGCT-MMC sub-module is bypassed; an energy extraction module, which is respectively connected to the IGCT-MMC sub-module, the overvoltage detection module and the trigger module, and is used to extract energy from the high-voltage capacitor of the IGCT-MMC sub-module and convert it into a working voltage to power the overvoltage detection module and the trigger module.

[0009] For example, in some embodiments of the present application, the energy acquisition module includes: a first resistor, one end of which is connected to the high-voltage capacitor of the IGCT-MMC sub-module; a second resistor, one end of which is connected to the other end of the first resistor, and the other end of the second resistor is grounded; a first diode, an anode of which is connected to the other end of the first resistor, and a cathode of which serves as a working voltage output end, and is respectively connected to the overvoltage detection module and the trigger module; a first capacitor, one end of which is connected to the cathode of the first diode, and the other end of the first capacitor is grounded; a first switch unit, a first end of which is connected to the anode of the first diode, and a second end is grounded; a first comparison unit, one end of which is connected to the cathode of the first diode, and the other end of the first comparison unit is connected to the third end of the first switch unit.

[0010] For example, in some embodiments of the present application, the energy acquisition module is configured as follows: the first comparison unit collects the voltage of the first capacitor, and when the voltage of the first capacitor is greater than or equal to a first set threshold, the first comparison unit outputs a control signal to turn on the first switch unit.

[0011] For example, in some embodiments of the present application, the overvoltage detection module includes: a third resistor, one end of which is connected to the high-voltage capacitor of the IGCT-MMC sub-module; a fourth resistor, one end of which is connected to the other end of the third resistor, and the other end of the fourth resistor is grounded; a second switch unit, a first end of which is connected to the energy acquisition module, and a second end of which is connected to the trigger module, so that when the voltage of the high-voltage capacitor is higher than the second set threshold, the voltage provided by the energy acquisition module is converted into the overvoltage signal and output to the trigger module; a second comparison unit, one end of which is connected to the other end of the third resistor, and the other end of the second comparison unit is connected to the third end of the second switch unit.

[0012] For example, in some embodiments of the present application, the overvoltage detection module is configured as follows: when the voltage of the high-voltage capacitor is higher than the second set threshold, the second comparison unit outputs a control signal to turn on the second switch unit, and the second switch unit outputs the overvoltage signal.

[0013] For example, in some embodiments of the present application, the trigger module includes: a signal isolation unit, whose input end is connected to the overvoltage signal output end of the overvoltage detection module to receive the overvoltage signal, and whose output end is connected to the IGCT gate drive module to output the control signal; a delay unit, whose input end is connected to the overvoltage signal output end of the overvoltage detection module to receive the overvoltage signal; a trigger unit, which is connected to the delay unit to receive the overvoltage signal; a third switch unit, whose third end is connected to the trigger unit to receive the trigger signal; a drive isolation unit, whose first end is connected to the second end of the third switch unit, and whose first end is connected to the energy acquisition module, so that when the voltage of the high-voltage capacitor is higher than the second set threshold, the third switch unit converts the voltage provided by the energy acquisition module into a drive signal and outputs it to the drive isolation unit; the second end of the drive isolation unit is grounded, and the first output end and the second output end of the drive isolation unit are connected to the IGCT gate drive module to output the on-current.

[0014] For example, in some embodiments of the present application, the signal isolation unit includes: one of an optical isolation device, a capacitive isolation device, and a magnetic isolation device.

[0015] For example, in some embodiments of the present application, the driving isolation unit includes: one of a pulse transformer and a driving optocoupler.

[0016] For example, in some embodiments of the present application, the IGCT gate drive module includes: a second diode, an anode connected to the first output end of the drive isolation unit, and a cathode connected to the gate of an IGCT device in the IGCT-MMC submodule; a third diode, an anode connected to the third output end of the drive isolation unit, and a cathode connected to the gate of another IGCT device in the IGCT-MMC submodule; a second capacitor, a positive electrode connected to the first return end of the drive isolation unit; a third capacitor, a positive electrode connected to the second return end of the drive isolation unit; a first control unit connected to the first output end of the signal isolation unit for receiving a control signal of the signal isolation unit; a second control unit connected to the second output end of the signal isolation unit for receiving a control signal of the signal isolation unit; a first switch, one end of which is connected to the cathode of the second diode, the other end of which is connected to the negative electrode of the second capacitor, and the first switch is connected to the first control unit for receiving a control signal of the first control unit; a second switch, one end of which is connected to the cathode of the third diode, the other end of which is connected to the negative electrode of the third capacitor, and the second switch is connected to the second control unit for receiving a control signal of the second control unit.

[0017] For example, in some embodiments of the present application, the trigger module is configured as follows: when the voltage of the high-voltage capacitor is higher than the second set threshold, the signal isolation unit and the delay unit receive the overvoltage signal; when the first switch and / or the second switch are closed, the signal isolation unit outputs a control signal to the first control unit and / or the second control unit of the IGCT gate drive module, so that the first control unit and / or the second control unit output a control signal to the first switch and / or the second switch, so that the first switch and / or the second switch are opened; the delay unit delays the first time to forward the overvoltage signal to the trigger unit; the trigger unit outputs a trigger signal to the third switch unit, so that the third switch unit is turned on; the third switch unit Output the driving signal to the driving isolation unit; the driving isolation unit outputs the conduction current, which is transmitted to the IGCT-MMC submodule through the second diode and the third diode of the IGCT gate driving module, so that the IGCT device is turned on; when the first switch and the second switch are turned on, the delay unit directly forwards the overvoltage signal to the trigger unit; the trigger unit outputs the trigger signal to the third switch unit, so that the third switch unit is turned on; the third switch unit outputs the driving signal to the driving isolation unit; the driving isolation unit outputs the conduction current, which is transmitted to the IGCT-MMC submodule through the second diode and the third diode of the IGCT gate driving module, so that the IGCT device is turned on.

[0018] For example, in some embodiments of the present application, the first switch and the second switch are respectively one of: a MOSFET, a thyristor, and a triode.

[0019] For example, in some embodiments of the present application, the IGCT device is connected using a half-bridge structure or a full-bridge structure.

[0020] According to the second aspect of the present application, at least one embodiment of the present application provides a controllable breakdown bypass protection method for an IGCT-MMC submodule, which is performed by a controllable breakdown bypass protection circuit as described in any one of the first aspects, and the controllable breakdown bypass protection method includes: the overvoltage detection module detects whether the voltage of the high-voltage capacitor is higher than the second set threshold; when the voltage of the high-voltage capacitor is higher than the second set threshold, the overvoltage detection module outputs the overvoltage signal; the trigger module receives the overvoltage signal; when the IGCT gate drive module is powered, the trigger module outputs a control signal so that the first switch and the second switch of the IGCT gate drive module are turned on, and the on-current is output with a first delay; or, when the IGCT gate drive module is not powered, the trigger module directly outputs the on-current; the IGCT gate drive module transmits the on-current to the IGCT device of the IGCT-MMC submodule, so that the IGCT device is turned on, and the high-voltage capacitor releases current to break down the IGCT device, thereby bypassing the IGCT-MMC submodule.

[0021] Beneficial Effects

[0022] Through the above-mentioned example embodiments, the present application provides a controllable breakdown bypass protection circuit and method for an IGCT-MMC submodule. Without changing the main topology of the IGCT-MMC submodule, the DC short-circuit fault loss is controlled within the submodule by adding an energy extraction module, an overvoltage detection module, a trigger module and an IGCT gate drive module. Without adding power devices, the IGCT controllable breakdown bypass is realized under the failure of the bypass switch, thereby controlling the cost of the converter. In addition, the energy extraction unit in the controllable breakdown bypass protection circuit for the IGCT-MMC submodule has an overcharge protection function, which can ensure the stable power supply of the controllable breakdown bypass protection circuit; and by adjusting the resistance value of the relevant module resistor, the overvoltage detection threshold and the voltage of the energy storage capacitor can be flexibly controlled, which is more suitable for complex application scenarios. And, in the case of a black module, the loss can be controlled at the submodule level to improve the reliability of the converter operation.

[0023] 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

[0024] 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.

[0025] Figure 1A schematic diagram of a controllable breakdown bypass protection circuit for an IGCT-MMC submodule according to an exemplary embodiment is shown;

[0026] Figure 2 A schematic diagram of an energy extraction module of an exemplary embodiment is shown;

[0027] Figure 3 A schematic diagram of an overvoltage detection module is shown in an exemplary embodiment;

[0028] Figure 4 A schematic diagram of a trigger module of an exemplary embodiment is shown;

[0029] Figure 5 A schematic diagram of an IGCT gate drive module of an exemplary embodiment is shown;

[0030] Figure 6 shows an exemplary IGCT-MMC submodule schematic diagram;

[0031] Figure 7 A flow chart of a controllable breakdown bypass protection method for an IGCT-MMC submodule according to an exemplary embodiment is shown. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] Figure 1 A schematic diagram of a controllable breakdown bypass protection circuit for an IGCT-MMC submodule according to an exemplary embodiment is shown.

[0038] like Figure 1 As shown, the controllable breakdown bypass protection circuit for the IGCT-MMC submodule includes: an energy acquisition module 10 , an overvoltage detection module 20 , a trigger module 30 and an IGCT gate drive module 40 .

[0039] Among them, the energy acquisition module 10 and the overvoltage detection module 20 are connected to the IGCT-MMC submodule 50 through port 101. The overvoltage detection module 20 is connected to the trigger module 30 through port 203. The trigger module 30 is connected to the IGCT gate drive module through ports 302, 303, 304, 305, 306, and 307. The IGCT gate drive module 40 is connected to the IGCT-MMC submodule 50 through ports 405 and 406.

[0040] The energy acquisition module 10 is used to obtain the high voltage capacitor C of the IGCT-MMC submodule 50. HV Energy is taken and converted into a stable working voltage to power the overvoltage detection module 20 and the trigger module 30.

[0041] like Figure 2 As shown, the energy acquisition module 10 includes: a first resistor R1, a second resistor R2, a first diode D1, a first capacitor C1, a first switch unit 1011 and a first comparison unit 1012. One end of the first resistor R1 is connected to the high-voltage capacitor C1 of the IGCT-MMC submodule. HVThe first comparison unit 1012 is connected to the cathode of the first diode D1, and the other end of the first comparison unit 1012 is connected to the third end of the first switch unit 1011.

[0042] According to an exemplary embodiment, the first resistor R1 is a high-end voltage-dividing resistor, and the second resistor R2 is a low-end voltage-dividing resistor. HV The voltage is input from port 101, and forms a voltage at port 102 through high and low voltage divider resistors R1 and R2. The voltage charges the energy storage capacitor C1 through the charging diode D1, and finally forms a stable voltage at port 103 at the upper end of the energy storage capacitor C1, and the output is a power supply for the overvoltage detection module 20 and the trigger module 30.

[0043] According to some embodiments, the energy acquisition module 10 also has an overcharge protection function: the first comparison unit 1012 collects the voltage of the first capacitor C1 at the collection end, and compares it with the internal first set threshold Vref1 in real time. When the voltage of the first capacitor C1 exceeds Vref1, the first switch unit 1011 is controlled to be turned on, bypassing the second resistor R2, and the first diode D1 is reversely cut off, and the voltage of the first capacitor C1 no longer rises.

[0044] The energy acquisition module 10 can flexibly control the power supply voltage by adjusting the resistance of the first resistor R1, the second resistor R2, and the threshold value Vref1 of the first comparison unit 1012. Specifically, the working voltage is the smaller value of Vref1 and the voltage of the second resistor R2 to ground.

[0045] The overvoltage detection module 20 is connected to the IGCT-MMC submodule to detect the high voltage capacitor C HV The voltage on the high voltage capacitor C HV When the voltage is higher than the second set threshold Vref2, an overvoltage signal is output.

[0046] like Figure 3 As shown, the overvoltage detection module 20 includes: a third resistor R3, a fourth resistor R4, a second switch unit 2011 and a second comparison unit 2012. One end of the third resistor R3 is connected to the high voltage capacitor C of the IGCT-MMC submodule. HVOne end of the fourth resistor R4 is connected to the other end of the third resistor R3, and the other end of the fourth resistor R4 is grounded. The first end of the second switch unit 2011 is connected to the port 103 of the energy acquisition module 10, and the second end is connected to the trigger module 30 to connect the high voltage capacitor C HV When the voltage of the second comparison unit 2012 is higher than the second set threshold, the voltage provided by the energy acquisition module 10 is converted into an overvoltage signal and output to the trigger module 30. One end of the second comparison unit 2012 is connected to the other end of the third resistor R3, and the other end of the second comparison unit 2012 is connected to the third end of the second switch unit 2011.

[0047] According to an exemplary embodiment, the third resistor R3 is a high-end voltage-dividing resistor, and the fourth resistor R4 is a low-end voltage-dividing resistor. HV The voltage is connected from port 201, passes through high and low end voltage-dividing resistors R3 and R4, and forms a divided voltage on port 202. The acquisition end of the second comparison unit 2012 is connected to port 202, collects the divided voltage, and compares it with the second set threshold value Vref2 in real time. When the voltage of port 202 exceeds the voltage of Vref2, the second comparison unit 2012 controls the second switch unit 2011 to turn on, and converts the power energy provided by the energy acquisition module 10 into an overvoltage signal and outputs it to port 203.

[0048] The overvoltage detection module 20 can adjust the resistance of the third resistor R3, the fourth resistor R4, the threshold value Vref2 of the second comparison unit 2012, and adjust the high-voltage capacitor C HV Specifically, the high voltage capacitor C HV The over-voltage threshold is the smaller value between Vref2 and the voltage of the fourth resistor R4 to ground.

[0049] The trigger module 30 is connected to the overvoltage detection module 20 and is used for receiving an overvoltage signal and outputting a control signal and a conduction current.

[0050] like Figure 4As shown, the trigger module 30 includes: a signal isolation unit 3011, a delay unit 3012, a trigger unit 3013, a third switch unit 3014 and a drive isolation unit 3015. Among them, the input end of the signal isolation unit 3011 is connected to the overvoltage signal output end 203 of the overvoltage detection module 20 to receive the overvoltage signal, and the output end of the signal isolation unit 3011 is connected to the IGCT gate drive module 40 to output the control signal. The input end of the delay unit 3012 is connected to the overvoltage signal output end 203 of the overvoltage detection module 20 to receive the overvoltage signal. The trigger unit 3013 is connected to the delay unit 3012 to receive the overvoltage signal. The third end of the third switch unit 3014 is connected to the trigger unit 3013 to receive the trigger signal. The first end of the third switch unit 3014 is connected to the port 103 of the energy acquisition module 10, and the first end of the drive isolation unit 3015 is connected to the second end of the third switch unit 3014 to output the control signal on the high voltage capacitor C HV When the voltage of the power module 10 is higher than the second set threshold, the third switch unit 3014 converts the voltage provided by the energy acquisition module 10 into a driving signal and outputs it to the driving isolation unit 3015. The second end of the driving isolation unit 3015 is grounded, and the first output end 305 and the second output end 306 of the driving isolation unit 3015 are connected to the IGCT gate driving module 40 to output a conduction current, and return the current through the first return end 304 and the second return end 307 of the driving isolation unit 3015 to form a current path.

[0051] The signal isolation unit 3011 is used to transmit the overvoltage signal and electrically isolate the IGCT gate driving module 40 and other units of the trigger module 30 .

[0052] According to some embodiments, the signal isolation unit 3011 includes: one of an optical isolation device, a capacitive isolation device and a magnetic isolation device. Preferably, an optical isolation device is used, and optionally, a capacitive isolation device or a magnetic isolation device is used.

[0053] The drive isolation unit 3015 is used to convert the energy of the first capacitor C1 into the on-current required to turn on the IGCT device, and has electrical isolation capability to isolate other units in the trigger module 30 and the IGCT gate drive module 40 .

[0054] According to some embodiments, the drive isolation unit 3015 includes: one of a pulse transformer and a drive optical coupler, preferably a pulse transformer, and optionally a drive optical coupler.

[0055] According to some embodiments, the first switch unit 1011 , the second switch unit 2011 , and the third switch unit 3014 include switch devices and supporting circuits therein.

[0056] The IGCT gate drive module 40 is connected to the trigger module 30 and the IGCT-MMC submodule respectively, and is used to drive the IGCT device to turn on and off. HV When the voltage is higher than the second set threshold value Vref2, it is used to receive a control signal to transfer the conduction current to the IGCT-MMC sub-module, so that the IGCT device is turned on, thereby realizing the bypass of the IGCT-MMC sub-module.

[0057] like Figure 5 As shown, the IGCT gate drive module 40 includes: a second diode D2, a third diode D3, a second capacitor C2, a third capacitor C3, a first control unit 4011, a second control unit 4012, a first switch S1 and a first switch S2. Among them, the anode of the second diode D2 is connected to the first output terminal 305 of the drive isolation unit 3015, and the cathode is connected to the gate of an IGCT device in the IGCT-MMC submodule. The anode of the third diode D3 is connected to the third output terminal 306 of the drive isolation unit 3015, and the cathode is connected to the gate of another IGCT device in the IGCT-MMC submodule. The positive electrode of the second capacitor C2 is connected to the first return terminal 304 of the drive isolation unit 3015. The positive electrode of the third capacitor C3 is connected to the second return terminal 307 of the drive isolation unit 3015. The first control unit 4011 is connected to the first output terminal 303 of the signal isolation unit 3011, and is used to receive the control signal of the signal isolation unit 3011. The second control unit 4012 is connected to the second output terminal 302 of the signal isolation unit 3011, and is used to receive the control signal of the signal isolation unit 3011. One end of the first switch S1 is connected to the cathode of the second diode D2, and the other end of the first switch S1 is connected to the negative electrode of the second capacitor C2. The first switch S1 is connected to the first control unit 4011, and is used to receive the control signal of the first control unit 4011. One end of the second switch S2 is connected to the cathode of the third diode D3, and the other end of the second switch S2 is connected to the negative electrode of the third capacitor C3. The second switch S2 is connected to the second control unit 4012, and is used to receive the control signal of the second control unit 4012.

[0058] According to some embodiments, the first switch S1 and the second switch S2 are respectively one of: MOSFET, thyristor and triode. Preferably, MOSFET is used, and thyristor and triode are optionally used.

[0059] According to an exemplary embodiment, the trigger module 30 is configured as follows: when the voltage of the high-voltage capacitor of the IGCT-MMC submodule is higher than the second set threshold, the signal isolation unit 3011 and the delay unit 3012 receive the overvoltage signal. When the gate drive module 40 is powered, that is, the first switch S1 and / or the second switch S2 are powered, the first switch S1 and / or the second switch S2 are closed, and the signal isolation unit 3011 outputs a control signal to the first control unit 4011 and / or the second control unit 4012 of the IGCT gate drive module 40, so that the first control unit 4011 and / or the second control unit 4012 outputs a control signal to the first switch S1 and / or the second switch S2, so that the first switch S1 and / or the second switch S2 are opened. The delay unit 3012 delays the first time to forward the overvoltage signal to the trigger unit 3013. The trigger unit 3013 outputs a trigger signal to the third switch unit 3014, so that the third switch unit 3014 is turned on. The third switch unit 3014 outputs a drive signal to the drive isolation unit 3015. The driving isolation unit 3015 outputs a conduction current, which is transmitted to the IGCT-MMC sub-module through the second diode D2 and the third diode D3 of the IGCT gate driving module 40 to turn on the IGCT device.

[0060] The delay unit 3012 is used to delay the overvoltage signal sent to the trigger unit 3013, ensuring that the overvoltage signal is first sent to the first control unit and the second control unit of the IGCT gate drive module via the signal isolation unit 3011, cutting off the first switch and the second switch, and ensuring that the IGCT conduction current output by the drive isolation unit 3015 is not absorbed by the second capacitor and the third capacitor.

[0061] According to some embodiments, the first time can be set by itself, and it is only necessary to ensure that the conduction current is transmitted to the IGCT-MMC submodule through the second diode D2 and the third diode D3 after the first switch S1 and the second switch S2 are turned on.

[0062] The trigger module 30 is further configured as follows: when the first switch S1 and the second switch S2 are not energized, the first switch S1 and the second switch S2 are opened, and the delay unit 3012 directly forwards the overvoltage signal to the trigger unit 3013. The trigger unit 3013 outputs a trigger signal to the third switch unit 3014 to turn on the third switch unit 3014. The third switch unit 3014 outputs a drive signal to the drive isolation unit 3015. The drive isolation unit 3015 outputs a conduction current, which is transmitted to the IGCT-MMC submodule through the second diode D2 and the third diode D3 of the IGCT gate drive module 40 to turn on the IGCT device.

[0063] The IGCT-MMC submodule is used to receive the IGCT conduction current. Figure 6As shown, the IGCT-MMC submodule includes two IGCT devices, upper and lower tubes, a bypass switch P1, and a high-voltage capacitor C HV The gate of the IGCT is connected to the port 502 and the port 503 to receive the conduction current. The bypass switch P1 is connected in parallel with the lower IGCT. The IGCT is connected in series with the high voltage capacitor C HV Parallel, high voltage capacitor C HV The positive pole is connected to port 101.

[0064] According to the exemplary embodiment, when the voltage of the high-voltage capacitor of the IGCT-MMC submodule is higher than the second set threshold, the overvoltage detection unit 20 outputs an overvoltage signal, the trigger module 3 outputs a control signal and a conduction current based on the overvoltage signal, and the IGCT gate drive module transmits the conduction current to the IGCT device. The upper and lower IGCTs are turned on at the same time, and the high-voltage capacitor C HV By short-circuiting the upper and lower IGCTs, the released large current directly breaks down the upper and lower IGCTs, and the short-circuit failure characteristics of the IGCT are utilized to bypass the IGCT power sub-module.

[0065] According to some embodiments, the present application only takes the IGCT-MMC submodule including two IGCT devices and connected in a half-bridge structure as an example, but the IGCT-MMC submodule can also be connected in a full-bridge structure, including four IGCT devices. The present application only takes this as an example, but is not limited thereto.

[0066] The controllable breakdown bypass protection circuit provided in the present application actively breaks down the upper and lower tube IGCTs to achieve submodule bypass when the voltage of the high-voltage capacitor reaches a set overvoltage threshold in the case of a submodule black module, which can effectively improve the long-term operation reliability of the converter valve.

[0067] The present application also provides a controllable breakdown bypass protection method for an IGCT-MMC submodule, which is performed by the controllable breakdown bypass protection circuit as described above.

[0068] like Figure 7 As shown, the controllable breakdown bypass protection method for the IGCT-MMC submodule includes steps S701-S704:

[0069] In step S701, the overvoltage detection module detects whether the voltage of the high-voltage capacitor is higher than a second set threshold.

[0070] In step S702, when the voltage of the high-voltage capacitor is higher than the second set threshold, the overvoltage detection module outputs an overvoltage signal.

[0071] In step S703, the trigger module receives the overvoltage signal, and the trigger module outputs a control signal and conducts current.

[0072] The trigger module receives the overvoltage signal, and when the IGCT gate drive module is powered, the trigger module outputs a control signal to open the first switch and the second switch of the IGCT gate drive module, and delays the output of the conduction current for a first time.

[0073] When the IGCT gate drive module is not powered, the trigger module directly outputs the conduction current.

[0074] In step S704 , the IGCT gate drive module transmits the on-current to the IGCT device of the IGCT-MMC submodule.

[0075] The IGCT gate drive module transmits the conduction current to the IGCT device of the IGCT-MMC submodule, so that the IGCT device is turned on, and the high-voltage capacitor releases current to break down the IGCT device, and the IGCT-MMC submodule is bypassed by utilizing the IGCT failure short-circuit characteristic.

[0076] The present application provides a controllable breakdown bypass protection circuit and method for an IGCT-MMC submodule. Without changing the main topology of the IGCT-MMC submodule, the DC short-circuit fault loss is controlled within the submodule by adding an energy-taking module, an overvoltage detection module, a trigger module, and an IGCT gate drive module. Without adding power devices, the IGCT controllable breakdown bypass is realized under bypass switch failure, thereby controlling the cost of the converter. In addition, the energy-taking unit in the controllable breakdown bypass protection circuit for the IGCT-MMC submodule has an overcharge protection function, which can ensure the stable power supply of the controllable breakdown bypass protection circuit; and by adjusting the resistance value of the relevant module resistor, the overvoltage detection threshold and the voltage of the energy storage capacitor can be flexibly controlled, which is more suitable for complex application scenarios. And, in the case of a black module, the loss can be controlled at the submodule level to improve the reliability of the converter operation.

[0077] 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.

[0078] 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.

[0079] 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 controllable breakdown bypass protection circuit for an IGCT-MMC submodule, characterized in that: The IGCT-MMC submodule includes an IGCT device and a high-voltage capacitor connected in series, and the controllable breakdown bypass protection circuit includes: an overvoltage detection module, connected to the IGCT-MMC submodule, for detecting the voltage of the high-voltage capacitor and outputting an overvoltage signal when the voltage of the high-voltage capacitor is higher than a second set threshold; A trigger module, connected to the overvoltage detection module, configured to receive the overvoltage signal and output a control signal and a conduction current; An IGCT gate drive module, connected to the trigger module and the IGCT-MMC submodule respectively, for receiving the control signal to transfer the conduction current to the IGCT-MMC submodule, so that the IGCT device is turned on, and the IGCT-MMC submodule is bypassed; The energy acquisition module is connected to the IGCT-MMC submodule, the overvoltage detection module and the trigger module respectively, and is used to obtain energy from the high-voltage capacitor of the IGCT-MMC submodule and convert it into a working voltage to power the overvoltage detection module and the trigger module.

2. The controllable breakdown bypass protection circuit according to claim 1, characterized in that: The energy acquisition module comprises: A first resistor, one end of which is connected to the high-voltage capacitor of the IGCT-MMC submodule; a second resistor, one end of which is connected to the other end of the first resistor, and the other end of the second resistor is grounded; a first diode, an anode of which is connected to the other end of the first resistor, and a cathode of which serves as a working voltage output end and is connected to the overvoltage detection module and the trigger module respectively; A first capacitor, one end of which is connected to the cathode of the first diode, and the other end of the first capacitor is grounded; A first switch unit, a first end of which is connected to the anode of the first diode and a second end of which is grounded; A first comparing unit has one end connected to the cathode of the first diode, and the other end of the first comparing unit is connected to the third end of the first switching unit.

3. The controllable breakdown bypass protection circuit according to claim 2, characterized in that: The energy acquisition module is configured as follows: The first comparison unit collects the voltage of the first capacitor, and when the voltage of the first capacitor is greater than or equal to a first set threshold, the first comparison unit outputs a control signal to turn on the first switch unit.

4. The controllable breakdown bypass protection circuit according to claim 1, characterized in that: The overvoltage detection module comprises: A third resistor, one end of which is connected to the high-voltage capacitor of the IGCT-MMC submodule; a fourth resistor, one end of which is connected to the other end of the third resistor, and the other end of the fourth resistor is grounded; a second switch unit, a first end of which is connected to the energy acquisition module, and a second end of which is connected to the trigger module, so as to convert the voltage provided by the energy acquisition module into the overvoltage signal when the voltage of the high-voltage capacitor is higher than the second set threshold value, and output the overvoltage signal to the trigger module; A second comparing unit has one end connected to the other end of the third resistor, and the other end of the second comparing unit is connected to the third end of the second switch unit.

5. The controllable breakdown bypass protection circuit according to claim 4, characterized in that: The overvoltage detection module is configured as follows: When the voltage of the high-voltage capacitor is higher than the second set threshold, the second comparison unit outputs a control signal to turn on the second switch unit, and the second switch unit outputs the overvoltage signal.

6. The controllable breakdown bypass protection circuit according to claim 1, characterized in that: The trigger module comprises: A signal isolation unit, whose input end is connected to the overvoltage signal output end of the overvoltage detection module to receive the overvoltage signal, and whose output end is connected to the IGCT gate drive module to output the control signal; A delay unit, whose input end is connected to the overvoltage signal output end of the overvoltage detection module to receive the overvoltage signal; A trigger unit, connected to the delay unit to receive the overvoltage signal; A third switch unit, a third end of which is connected to the trigger unit to receive a trigger signal; A driving isolation unit, wherein the first end is connected to the second end of the third switch unit, and the first end of the third switch unit is connected to the energy acquisition module, so that when the voltage of the high-voltage capacitor is higher than the second set threshold, the third switch unit converts the voltage provided by the energy acquisition module into a driving signal and outputs it to the driving isolation unit; the second end of the driving isolation unit is grounded, and the first output end and the second output end of the driving isolation unit are connected to the IGCT gate drive module to output the on-current.

7. The controllable breakdown bypass protection circuit according to claim 6, characterized in that: The signal isolation unit comprises: one of an optical isolation device, a capacitive isolation device and a magnetic isolation device.

8. The controllable breakdown bypass protection circuit according to claim 6, characterized in that: The driving isolation unit includes: one of a pulse transformer and a driving optical coupler.

9. The controllable breakdown bypass protection circuit according to claim 6, characterized in that: The IGCT gate drive module comprises: a second diode, an anode of which is connected to the first output terminal of the driving isolation unit, and a cathode of which is connected to a gate of an IGCT device in the IGCT-MMC submodule; a third diode, an anode of which is connected to the third output terminal of the driving isolation unit, and a cathode of which is connected to the gate of another IGCT device in the IGCT-MMC submodule; A second capacitor, a positive electrode of which is connected to the first return terminal of the driving isolation unit; A third capacitor, a positive electrode of which is connected to the second return end of the drive isolation unit; A first control unit, connected to the first output terminal of the signal isolation unit, and configured to receive a control signal of the signal isolation unit; A second control unit, connected to the second output end of the signal isolation unit, and configured to receive a control signal from the signal isolation unit; a first switch, one end of which is connected to the cathode of the second diode, the other end of which is connected to the negative electrode of the second capacitor, and the first switch is connected to the first control unit to receive a control signal of the first control unit; A second switch has one end connected to the cathode of the third diode, the other end of the second switch is connected to the negative electrode of the third capacitor, and the second switch is connected to the second control unit for receiving a control signal of the second control unit.

10. The controllable breakdown bypass protection circuit according to claim 9, characterized in that: The trigger module is configured as follows: When the voltage of the high-voltage capacitor is higher than the second set threshold, the signal isolation unit and the delay unit receive the overvoltage signal; When the first switch and / or the second switch is closed, the signal isolation unit outputs a control signal to the first control unit and / or the second control unit of the IGCT gate drive module, so that the first control unit and / or the second control unit outputs a control signal to the first switch and / or the second switch, so that the first switch and / or the second switch is opened; the delay unit delays the first time and forwards the overvoltage signal to the trigger unit; the trigger unit outputs a trigger signal to the third switch unit, so that the third switch unit is turned on; the third switch unit outputs the drive signal to the drive isolation unit; The drive isolation unit outputs the conduction current, and transmits it to the IGCT-MMC submodule through the second diode and the third diode of the IGCT gate drive module, so as to turn on the IGCT device; When the first switch and the second switch are turned on, the delay unit directly forwards the overvoltage signal to the trigger unit; the trigger unit outputs the trigger signal to the third switch unit to turn on the third switch unit; the third switch unit outputs the drive signal to the drive isolation unit; The drive isolation unit outputs the conduction current, which is transmitted to the IGCT-MMC submodule through the second diode and the third diode of the IGCT gate drive module, so as to turn on the IGCT device.

11. The controllable breakdown bypass protection circuit according to claim 9, characterized in that: The first switch and the second switch are respectively one of: a MOSFET, a thyristor and a triode.

12. The controllable breakdown bypass protection circuit according to claim 1, characterized in that: The IGCT devices are connected in a half-bridge structure or a full-bridge structure.

13. A controllable breakdown bypass protection method for an IGCT-MMC submodule, characterized in that: The controllable breakdown bypass protection method is performed by the controllable breakdown bypass protection circuit according to any one of claims 1 to 12, and comprises: The overvoltage detection module detects whether the voltage of the high-voltage capacitor is higher than the second set threshold; When the voltage of the high-voltage capacitor is higher than the second set threshold, the overvoltage detection module outputs the overvoltage signal; The trigger module receives the overvoltage signal; when the IGCT gate drive module is powered, the trigger module outputs a control signal so that the first switch and the second switch of the IGCT gate drive module are turned on, and the conduction current is output after a first delay; or, when the IGCT gate drive module is not powered, the trigger module directly outputs the conduction current; The IGCT gate drive module transmits the conduction current to the IGCT device of the IGCT-MMC submodule, so that the IGCT device is turned on, and the high-voltage capacitor releases current to break down the IGCT device, thereby bypassing the IGCT-MMC submodule.

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