Overvoltage protection device and system of switching device

Abstract

The invention provides an overvoltage protection device and system for a switching device, and belongs to the technical field of power electronic converters. The passive overvoltage trigger circuit comprises a passive overvoltage power supply circuit, a passive trigger current shaping circuit and a feedback signal generating circuit; the switching device driving circuit comprises a trigger logic processing module, an active trigger circuit and a turn-off module. Based on the above technical scheme, the method can be easily combined with an existing switching device-MMC topology and switching device drive, and active-passive overvoltage trigger cooperation structures are complementary backups for each other, so that the false triggering possibility is extremely low, and the reliability is improved; and the overvoltage protection action can still be effectively executed under the condition of driving power loss or partial failure, and the method has a relatively high application value in MMC converter station engineering application with relatively high reliability requirements.

Description

Technical Field

[0001] The present invention belongs to the technical field of power electronic converters, and in particular relates to an overvoltage protection device and system for a switching device. Background Art

[0002] During the operation of a power electronic converter system containing switching devices, overvoltage may occur on the switching devices due to control system failure or main circuit failure. If the overvoltage persists, it will easily cause the continued spread of faults and damage in the converter, leading to serious accidents such as converter damage.

[0003] Modular multilevel converter (MMC) is one of the important application scenarios of switching devices, in which the submodule support capacitor is a passive component to be protected. In order to solve the overvoltage protection problem of MMC submodules, the existing technology provides protection by setting a bypass protection element at the AC port of the submodule. When an internal fault occurs in the submodule, the faulty module is reliably bypassed through multi-level means such as active bypass and passive breakdown. The bypass switch at the module port is an active protection element when the power module occurs. When the module has an overvoltage fault, it closes and maintains the flow capacity; the thyristor at the port is a passive protection element when the module fails. When the module has an overvoltage that reaches the thyristor breakdown voltage, the thyristor undergoes passive breakdown and has the flow capacity. However, this method requires the addition of a larger mechanical switch and thyristor on the basis of the submodule, which increases the size of the submodule and the cost.

[0004] On the other hand, the switch device-MMC structure of the prior art utilizes the overvoltage breakdown characteristics of the switch device. As the capacitor voltage increases, the lower switch device can break down due to overvoltage, presenting a reliable short-circuit state, thereby bypassing the sub-module of this level. However, the breakdown voltage of the high-off withstand voltage level switch device is relatively high, which is not conducive to breakdown protection when an overvoltage event occurs. Summary of the invention

[0005] In view of the above problems, the present disclosure proposes an overvoltage protection device and system for a switching device, which can be easily combined with the existing switching device-MMC topology and switching device drive, and the active-passive overvoltage trigger coordination structure complements each other and backs up each other, and the possibility of false triggering is extremely low, thereby improving reliability; and the overvoltage protection action can still be effectively performed in the event of a power failure or partial failure of the drive, and has a high application value in MMC converter station engineering applications with high reliability requirements.

[0006] One embodiment of the present disclosure provides an overvoltage protection device for a switching device, including: Passive overvoltage trigger circuit, switch device driving circuit and switch device; In the non-isolated working mode, the positive electrode of the passive overvoltage trigger circuit is connected to the target detection anode, and the negative electrode of the passive overvoltage trigger circuit is connected to the gate of the switching device; or the positive electrode of the passive overvoltage trigger circuit is connected to the target detection anode; In the isolated working mode, the positive and negative electrodes of the passive overvoltage trigger circuit are connected between the target detection anode and the target detection cathode respectively; The passive overvoltage trigger circuit comprises: a passive overvoltage power supply circuit, a passive trigger current shaping circuit and a feedback signal generating circuit; The positive electrode of the passive overvoltage power supply circuit is connected to the positive electrode of the voltage to be measured, and the negative electrodes of the passive overvoltage power supply circuit and the passive trigger current shaping circuit are connected to the negative electrode of the voltage to be measured; In the non-isolated mode, the positive electrode of the passive trigger current shaping circuit is connected to the gate of the switching device, and there is no negative electrode connection; in the isolated mode, the positive electrode of the passive trigger current shaping circuit is connected to the gate of the switching device, and the negative electrode is connected to the cathode of the switching device; The feedback signal generating circuit is connected to the passive trigger current shaping circuit signal, and is used to receive the passive trigger current shaping circuit action signal and output a feedback signal to the switch device driving circuit; The switch device driving circuit includes: a trigger logic processing module, an active trigger circuit and a shutdown module; the trigger logic processing module is connected to the active trigger circuit and the shutdown module signal, and the active trigger circuit is connected to the gate and cathode of the switch device in parallel with the shutdown module.

[0007] Preferably, the passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a series connection of a nonlinear varistor-type breakdown diode, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

[0008] Preferably, the passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a first transient voltage suppression diode connected in series, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

[0009] Preferably, the passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a nonlinear varistor-type breakdown diode and a first transient voltage suppression diode connected in series, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

[0010] Preferably, the passively triggered current shaping circuit comprises: a thyristor and a first capacitor; The passive overvoltage trigger circuit is in a non-isolated injection working mode, the first capacitor is connected in parallel to both ends of the current shaping resistor, and the first capacitor is connected in parallel between the gate and cathode of the thyristor; The anode of the thyristor is connected to the anode terminal of the nonlinear voltage-sensitive element breakdown diode in the passive overvoltage power supply circuit.

[0011] Preferably, the passively triggered current shaping circuit comprises: A voltage-stabilized power supply module, an on-pulse current shaping circuit, a drive pulse transformer, a first diode and a first switch; The voltage-stabilized power supply module is electrically connected to the passive overvoltage power supply circuit; the voltage-stabilized power supply module, the opening pulse current shaping circuit and the driving pulse transformer are connected in parallel, and the opening pulse current shaping circuit is signal-connected to the overvoltage detection circuit; One end of the first secondary side of the driving pulse transformer is connected in series with the anode of the first diode, and the other end of the first secondary side of the driving pulse transformer is connected in series with the first end of the first switch; The cathode of the first diode is connected to the gate of the switching device, and the second end of the first switch is connected to the cathode of the switching device.

[0012] Preferably, the passive trigger current shaping circuit further comprises, in the isolation injection working mode: A second diode and a second switch, or a bidirectional switch formed by the second switch; One end of the second secondary side of the driving pulse transformer is connected in series with the anode of the second diode, and the other end of the second secondary side of the driving pulse transformer is connected in series with the first end of the second switch; The cathode of the second diode is connected to the gate of the switching device as a first gate output, and the second end of the second switch is connected to the cathode of the switching device as a first cathode; The cathode of the first diode is connected to the gate of the switching device as a second gate output, and the second end of the first switch is connected to the cathode of the switching device as a second cathode.

[0013] Preferably, the passive trigger current shaping circuit further includes: The driving pulse transformer comprises a first primary side and a second primary side, the first primary side corresponds to a first secondary side, and the second primary side corresponds to a second secondary side; One end of the second secondary side of the driving pulse transformer is connected in series with the anode of the second diode, and the other end of the second secondary side of the driving pulse transformer is connected in series with the first end of the second switch; The first primary side is connected in parallel with the second primary side, and the first primary side and the second primary side are connected in parallel to the turn-on pulse current shaping circuit.

[0014] Preferably, in the passive trigger current shaping circuit in the isolated current injection working mode, the voltage regulated power supply module includes: a second capacitor, a first resistor, a third capacitor, and a second transient voltage suppression diode; The third capacitor and the second transient voltage suppression diode are connected in parallel, the cathode of the second transient voltage suppression diode is connected in series to one end of the first resistor, the other end of the first resistor and the anode of the second transient voltage suppression diode are connected to the first end and the second end of the second capacitor respectively, the first end of the second capacitor is connected to the passive overvoltage power supply, and the second end of the second capacitor is connected to the negative electrode of the measured voltage; Both ends of the third capacitor are connected to the turn-on pulse current shaping module.

[0015] Turn on the pulse current shaping module, including: An overvoltage detection trigger enabling circuit, a PWM drive signal generating circuit and a power tube, wherein the overvoltage detection trigger enabling circuit is connected to the PWM drive signal generating circuit, and the PWM drive signal generating circuit is connected to the base of the power tube.

[0016] Preferably, the passive triggered current shaping circuit turns on the pulse current shaping module in the isolated current injection working mode, including: a second resistor, a fourth capacitor, a bidirectional trigger diode, a fourth resistor and a second thyristor; The second resistor and the fourth capacitor form an RC circuit, and the first end of the second resistor is connected to the voltage-stabilized power supply module; The second end of the second resistor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the voltage-stabilized power supply module; The lead-out end between the second end of the second resistor and the first end of the fourth capacitor is connected to the first end of the bidirectional trigger diode, the second end of the bidirectional trigger diode is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the gate of the second thyristor, the cathode of the second thyristor is connected to the second end of the fourth capacitor, and the anode of the second thyristor is connected to the pulse transformer.

[0017] Based on the same inventive concept, the embodiment of the present disclosure also provides an overvoltage protection system for a switching device. At least two overvoltage protection devices of the switch devices are cascaded to form a first half-bridge submodule, Wherein, the positive and negative electrodes of the passive overvoltage trigger circuit are connected between the target detection anode and the gate of the switch device, and the switch device is connected in parallel with a freewheeling diode; Bridge arm capacitors are connected at both ends of the half-bridge submodule.

[0018] Preferably, the first switch device is connected to the drive circuit, and the second switch device is connected to the passive overvoltage trigger and the drive circuit to form a second half-bridge submodule; The first gate output terminal of the passive overvoltage trigger and drive circuit is connected to the gate of the second switch device, and the second cathode of the passive overvoltage trigger and drive circuit is connected to the anode of the second switch device and the cathode of the first switch device; The second gate output terminal of the passive overvoltage trigger and drive circuit is connected to the gate of the first switching device; The driving circuit is connected to the gate and cathode of the first switching device.

[0019] Preferably, the full-bridge circuit is obtained by cascading a plurality of second half-bridge sub-modules.

[0020] The above one or at least one technical solution in the embodiments of the present disclosure has at least the following technical effects: The present disclosure provides an overvoltage protection device and system for a switching device, wherein, in a non-isolated working mode, the positive and negative electrodes of the passive overvoltage trigger circuit are connected between a target detection anode and a gate of the switching device; in an isolated working mode, the positive and negative electrodes of the passive overvoltage trigger circuit are connected between a target detection anode and a target detection cathode; the passive overvoltage trigger circuit comprises: a passive overvoltage power supply circuit, a passive trigger current shaping circuit and a feedback signal generating circuit; the positive electrode of the passive overvoltage power supply circuit is connected to the positive electrode of the voltage to be measured, and the negative electrodes of the passive overvoltage power supply circuit and the passive trigger current shaping circuit are connected to the negative electrode of the voltage to be measured; the feedback signal generating circuit is signal-connected to the passive trigger current shaping circuit, and is used to receive an action signal of the passive trigger current shaping circuit and output a feedback signal to a switching device driving circuit; the switching device driving circuit comprises: a trigger logic processing module, an active trigger circuit and a shutdown module; the trigger logic processing module is signal-connected to the active trigger circuit and the shutdown module, and the active trigger circuit is connected to the gate and cathode of the switching device in parallel with the shutdown module. Based on the above technical solution, it can be easily combined with the existing switch device-MMC topology and switch device drive, and the active-passive overvoltage trigger coordination structure complements each other, the possibility of false triggering is extremely low, and the reliability is improved; and in the case of power failure or partial failure of the drive, the overvoltage protection action can still be effectively performed, and it has a high application value in the MMC converter station engineering application with high reliability requirements.

[0021] Other features and advantages of the present disclosure will be described in the following description, and partly become apparent from the description, or be understood by implementing the present disclosure. The purpose and other advantages of the present disclosure can be realized and obtained by the structures indicated in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 A schematic diagram of an overvoltage protection device for a switching device in the present disclosure is shown; Figure 2 A second schematic diagram of an overvoltage protection device for a switching device in the present disclosure is shown; Figure 3 A schematic diagram showing a first embodiment of a passive overvoltage trigger circuit in the present disclosure is shown; Figure 4A schematic diagram of a second embodiment of a passive overvoltage trigger circuit in the present disclosure is shown; Figure 5 A third schematic diagram of a passive overvoltage trigger circuit implementation scheme in the present disclosure is shown; Figure 6 A fourth schematic diagram of a passive overvoltage trigger circuit implementation scheme in the present disclosure is shown; Figure 7 A schematic diagram showing an implementation scheme of a passive triggered current shaping module in the present disclosure is shown; Figure 8 A schematic diagram of a second embodiment of a passive triggered current shaping module in the present disclosure is shown; Fig. 9 A third schematic diagram of an implementation scheme of a passive triggered current shaping module in the present disclosure is shown; Fig.10 A schematic diagram showing an implementation example 1 of a voltage-stabilized power supply module and a start-up pulse current shaping module in the present disclosure is shown; Fig.11 A schematic diagram of a second embodiment of a voltage-stabilized power supply module and a start-up pulse current shaping module in the present disclosure is shown; Fig.12 A schematic diagram of an active overvoltage detection circuit in the present disclosure is shown; Fig.13 A schematic diagram of a first half-bridge submodule in the present disclosure is shown; Fig.14 A schematic diagram of a second half-bridge submodule in the present disclosure is shown; Fig.15 A schematic diagram of a full-bridge circuit in the present disclosure is shown. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0025] It should be noted that the terms "first", "second" etc. in the present application are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged in appropriate circumstances, so that the embodiments of the present application described here. In the present application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal" etc. are based on the orientation or positional relationship shown in the accompanying drawings.

[0026] One embodiment of the present disclosure provides an overvoltage protection device for a switching device, see Figure 1 and Figure 2 ,include: Passive overvoltage trigger circuit, switch device driving circuit and switch device; In the non-isolated working mode, the positive electrode of the passive overvoltage trigger circuit is connected to the target detection anode, and the negative electrode of the passive overvoltage trigger circuit is connected to the gate of the switching device; or the positive electrode of the passive overvoltage trigger circuit is connected to the target detection anode; In the isolated working mode, the positive and negative electrodes of the passive overvoltage trigger circuit are connected between the target detection anode and the target detection cathode respectively; The passive overvoltage trigger circuit comprises: a passive overvoltage power supply circuit, a passive trigger current shaping circuit and a feedback signal generating circuit; The positive electrode of the passive overvoltage power supply circuit is connected to the positive electrode of the voltage to be measured, and the negative electrodes of the passive overvoltage power supply circuit and the passive trigger current shaping circuit are connected to the negative electrode of the voltage to be measured; In the non-isolated mode, the positive electrode of the passive trigger current shaping circuit is connected to the gate of the switching device, and there is no negative electrode connection; in the isolated mode, the positive electrode of the passive trigger current shaping circuit is connected to the gate of the switching device, and the negative electrode is connected to the cathode of the switching device; The feedback signal generating circuit is connected to the passive trigger current shaping circuit signal, and is used to receive the passive trigger current shaping circuit action signal and output a feedback signal to the switch device driving circuit; The switch device driving circuit includes: a trigger logic processing module, an active trigger circuit and a shutdown module; the trigger logic processing module is connected to the active trigger circuit and the shutdown module signal, and the active trigger circuit is connected to the gate and cathode of the switch device in parallel with the shutdown module.

[0027] It should be noted that the switching device referred to in the present disclosure is not limited to a certain type of switching device, and can be a switching device such as IGBT, IGCT or GTO. IGCT can be used as an example in the present disclosure, and the selection of the switching device will not be repeated here.

[0028] Combine the following Figure 1 The overvoltage protection device of the present disclosure is described.

[0029] See also Figure 1 , A, G, K of the switch device in the present disclosure are respectively the anode, gate and cathode of the switch device; The passive overvoltage trigger circuit includes three modules: a passive overvoltage power supply circuit, a passive trigger current shaping circuit and a feedback signal generating circuit.

[0030] The passive overvoltage power supply circuit detects whether the target voltage is overvoltage, draws power from the voltage source under test, and is used to provide a gate trigger current for the switch device when overvoltage occurs. The passive overvoltage power supply circuit can have one or more circuits with different overvoltage trigger thresholds, corresponding to different turn-on action voltages; the overvoltage trigger threshold setting of the present disclosure is based on the debugging method of the passive overvoltage power supply circuit in the present disclosure and is not described in detail in this application.

[0031] The main function of the passive overvoltage trigger circuit is to inject gate current into the switch device to trigger it to turn on when an overvoltage event occurs. Its current injection method can be isolated or non-isolated; its positive and negative poles can be connected between the target detection anode and the gate of the switch device to work in a non-isolated manner, or it can be connected between the target detection anode and the target detection cathode to generate a power supply to provide a trigger current when the detected voltage is overvoltage, and connect the gate of the switch device through an additional interface to work in an isolated or non-isolated manner.

[0032] The negative pole of the passive overvoltage power supply circuit and the passive trigger current shaping circuit may be connected to the negative pole of the voltage to be measured, or may not be connected, which is determined by their internal structures.

[0033] See also Figure 2 The feedback signal generating circuit outputs a feedback signal to the driving circuit when the passive trigger current shaping circuit is in operation, and cooperates with the driving circuit to perform the overvoltage trigger opening action. The circuit and the passive overvoltage feedback signal are optional.

[0034] The driving circuit consists of a trigger logic processing module, an active trigger circuit and a shutdown module, and serves as a driver for the switching device under normal working conditions.

[0035] In some specific embodiments, see Figure 3 , the passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a series connection of a nonlinear varistor-type breakdown diode, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

[0036] Specifically, see Figure 3 The passive overvoltage trigger circuit includes a passive overvoltage power supply circuit composed of a nonlinear varistor breakdown diode (BOD) in series, a passive trigger current shaping circuit composed of a current shaping resistor, and an optional feedback signal generation circuit; the circuit draws power from the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit, and then injects it into the gate of the switching device, providing a gate trigger current for the switching device when overvoltage occurs.

[0037] In some specific embodiments, see Figure 4 , the passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a first transient voltage suppression diode connected in series, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

[0038] In some specific embodiments, see Figure 5 , the passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a nonlinear varistor-type breakdown diode and a first transient voltage suppression diode connected in series, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

[0039] In some specific embodiments, see Figure 6 , the passive trigger current shaping circuit comprises: a thyristor and a first capacitor; Specifically, in the non-isolated injection working mode of the passive overvoltage trigger circuit, the first capacitor is connected in parallel to both ends of the current shaping resistor, and the first capacitor is connected in parallel between the gate and cathode of the thyristor; The anode of the thyristor is connected to the anode terminal of the nonlinear voltage-sensitive element breakdown diode in the passive overvoltage power supply circuit.

[0040] In some specific embodiments, see Figure 7 , the passive trigger current shaping circuit comprises: A voltage-stabilized power supply module, an on-pulse current shaping circuit, a drive pulse transformer, a first diode and a first switch; The voltage-stabilized power supply module is electrically connected to the passive overvoltage power supply circuit; the voltage-stabilized power supply module, the opening pulse current shaping circuit and the driving pulse transformer are connected in parallel, and the opening pulse current shaping circuit is signal-connected to the overvoltage detection circuit; One end of the first secondary side of the driving pulse transformer is connected in series with the anode of the first diode, and the other end of the first secondary side of the driving pulse transformer is connected in series with the first end of the first switch; The cathode of the first diode is connected to the gate of the switching device, and the second end of the first switch is connected to the cathode of the switching device.

[0041] Specifically, see Figure 8 , the passive trigger current shaping circuit in the isolated injection working mode further includes: A second diode and a second switch, or a bidirectional switch formed by the second switch; One end of the second secondary side of the driving pulse transformer is connected in series with the anode of the second diode, and the other end of the second secondary side of the driving pulse transformer is connected in series with the first end of the second switch; The cathode of the second diode is connected to the gate of the switching device as a first gate output, and the second end of the second switch is connected to the cathode of the switching device as a first cathode; The cathode of the first diode is connected to the gate of the switching device as a second gate output, and the second end of the first switch is connected to the cathode of the switching device as a second cathode.

[0042] Specifically, see Fig. 9 , after the measured target voltage loaded between the positive and negative electrodes of the measured voltage is over-voltage, the passive over-voltage power supply circuit draws power from the anode to provide power for the voltage-stabilizing power supply module; the enable signal for turning on the pulse current shaping circuit can be generated from the over-voltage detection circuit, and can be enabled immediately when the passive over-voltage power supply circuit starts to provide power, or can use internal enable logic, etc.; after detecting that the measured voltage is higher than its over-voltage threshold, the turn-on pulse current shaping circuit starts to work, driving the pulse transformer to generate a turn-on pulse current on the secondary side, and transmits the trigger signal to the feedback signal generation circuit; the pulse transformer and the first diode D1 and the first switch S1 send the pulse trigger current to the gate of the switching device to trigger the turn-on. The first diode D1 prevents reverse current from flowing through the pulse transformer, and the first switch S1 prevents the gate current injection loop from being turned on due to the gate cathode reverse voltage when the switching device is in the off state.

[0043] In some specific embodiments, see Fig.10 , the passive trigger current shaping circuit further includes: The driving pulse transformer comprises a first primary side and a second primary side, the first primary side corresponds to a first secondary side, and the second primary side corresponds to a second secondary side; One end of the second secondary side of the driving pulse transformer is connected in series with the anode of the second diode, and the other end of the second secondary side of the driving pulse transformer is connected in series with the first end of the second switch; The first primary side is connected in parallel with the second primary side, and the first primary side and the second primary side are connected in parallel to the turn-on pulse current shaping circuit.

[0044] Specifically, the passive trigger current shaping circuit can have two isolated outputs, and realize the simultaneous triggering of the upper and lower tubes in a structure with upper and lower tubes (such as an MMC submodule). The two-way isolated output can be achieved using a dual-secondary pulse transformer or two independent pulse transformers.

[0045] In some specific embodiments, see Fig.10 , the passive trigger current shaping circuit is in the isolated current injection working mode, and the voltage regulated power supply module includes: a second capacitor, a first resistor, a third capacitor, and a second transient voltage suppression diode; The third capacitor and the second transient voltage suppression diode are connected in parallel, the cathode of the second transient voltage suppression diode is connected in series to one end of the first resistor, the other end of the first resistor and the anode of the second transient voltage suppression diode are connected to the first end and the second end of the second capacitor respectively, the first end of the second capacitor is connected to the passive overvoltage power supply, and the second end of the second capacitor is connected to the negative electrode of the measured voltage; Both ends of the third capacitor are connected to the turn-on pulse current shaping module.

[0046] Specifically, in the isolated current injection mode of the passive trigger current shaping circuit, the voltage regulated power supply module and the opening pulse current shaping module are implemented as follows: The voltage-stabilized power supply module can be composed of discrete components, and the voltage regulator tube can ensure the stability of the power supply voltage; other voltage-stabilized power supply structures such as integrated circuit chips can also be used. When the pulse current shaping circuit detects that the measured voltage exceeds its overvoltage detection threshold, the overvoltage detection triggering enabling circuit enables the PWM drive signal generating circuit, and drives the pulse transformer to generate the isolated switching device gate injection current.

[0047] In some specific embodiments, see Fig.11 , turn on the pulse current shaping module, including: An overvoltage detection trigger enabling circuit, a PWM drive signal generating circuit and a power tube, wherein the overvoltage detection trigger enabling circuit is connected to the PWM drive signal generating circuit, and the PWM drive signal generating circuit is connected to the base of the power tube.

[0048] Specifically, the pulse current shaping circuit can also be turned on by Fig.11 The method shown in the figure is implemented as follows: the voltage change of the voltage-stabilized power supply module is detected by the RC branch. When the voltage exceeds the threshold of the bidirectional trigger diode, the T1 switch element is triggered, and a pulse current for triggering the switch device is generated on the primary and secondary sides of the pulse transformer. The T1 element can be a thyristor or other switch elements such as a triode.

[0049] In some specific embodiments, see Fig.11, the passive trigger current shaping circuit opens the pulse current shaping module in the isolated current injection working mode, including: a second resistor, a fourth capacitor, a bidirectional trigger diode, a fourth resistor and a second thyristor; The second resistor and the fourth capacitor form an RC circuit, and the first end of the second resistor is connected to the voltage-stabilized power supply module; The second end of the second resistor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the voltage-stabilized power supply module; The lead-out end between the second end of the second resistor and the first end of the fourth capacitor is connected to the first end of the bidirectional trigger diode, the second end of the bidirectional trigger diode is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the gate of the second thyristor, the cathode of the second thyristor is connected to the second end of the fourth capacitor, and the anode of the second thyristor is connected to the pulse transformer.

[0050] See also Fig.12 , Cooperation with active overvoltage detection module: This solution can cooperate with the overvoltage trigger opening solution based on active overvoltage detection. Active overvoltage detection works when the switch device driver is powered. The active overvoltage trigger works when the switch device driver is powered. Its setting threshold is lower than the passive overvoltage trigger threshold. When the driver detects overvoltage, the opening action is performed.

[0051] Based on the same inventive concept, the present disclosure also provides an overvoltage protection system for a switching device, see Fig.13 , At least two overvoltage protection devices of the switch devices are cascaded to form a first half-bridge submodule, Wherein, the positive and negative electrodes of the passive overvoltage trigger circuit are connected between the target detection anode and the gate of the switch device, and the switch device is connected in parallel with a freewheeling diode; Bridge arm capacitors are connected at both ends of the half-bridge submodule.

[0052] In some specific implementations, the first switch device is connected to the drive circuit, and the second switch device is connected to the passive overvoltage trigger and the drive circuit to form a second half-bridge submodule; The first gate output terminal of the passive overvoltage trigger and drive circuit is connected to the gate of the second switch device, and the second cathode of the passive overvoltage trigger and drive circuit is connected to the anode of the second switch device and the cathode of the first switch device; The second gate output terminal of the passive overvoltage trigger and drive circuit is connected to the gate of the first switching device; The driving circuit is connected to the gate and cathode of the first switching device.

[0053] Preferably, the full-bridge circuit is obtained by cascading a plurality of second half-bridge sub-modules.

[0054] Specifically, with respect to an overvoltage protection system for a switching device, the present disclosure provides a specific implementation of the overvoltage breakdown protection method in a switching device-MMC submodule.

[0055] The embodiment of the present invention provides an overvoltage protector suitable for an MMC submodule constructed using a 4500V switch device, the structure of which is as follows: Figure 13-Figure 15 The passive overvoltage trigger and drive circuit is composed of a passive overvoltage trigger circuit and a drive circuit. The internal connection is as follows: Figure 1 As shown, the cooperation with the MMC submodule is as follows Figure 13-Figure 15 shown.

[0056] See also Fig.13 When the switch device driver in the switch device-MMC submodule completely loses power or fails to perform the opening action, a turn-on current will be injected into the gate of the switch device through the trigger circuit to turn it on.

[0057] The voltage that triggers the overvoltage protection can be calculated using the following formula:

[0058] in, and are the number of BOD and TVS connected in series in the passive overvoltage power supply circuit, and are the above-mentioned BOD and TVS conduction voltages respectively. When the anode and cathode pressure of the switching device exceeds the overvoltage trigger threshold, the passive overvoltage power supply circuit starts to work, and the passive trigger current shaping circuit injects a turn-on trigger pulse current into the gate of the switching device to turn it on. When the upper and lower tubes are turned on at the same time, the energy released instantly will cause the lower tube switch device to break down and enter a reliable direct-on state, so that the MMC submodule can be reliably bypassed.

[0059] When the switch device is driven normally, can receive the trigger instruction issued by the valve control, and can execute the opening logic, but the switch device cannot inject the trigger current due to a fault in the driving opening circuit, the passive overvoltage trigger circuit can be used to trigger the switch device to open.

[0060] When the switch device is driven normally, but the communication between the driver and the valve control is abnormal and the trigger command issued by the valve control cannot be received, the opening logic cannot be executed and it remains in the off state. In this case, the active overvoltage detection module is required to send an overvoltage signal when the positive and negative overvoltages are detected, so that the driver executes the logic strategy of turning off the MOSFET array and turning on the circuit. The active overvoltage detection module is effective when the driver is powered. When overvoltage occurs, an opening signal will be sent to the switch device driver to turn on the switch device. Therefore, the action threshold of the active overvoltage detection module can be set to be slightly lower than the action threshold of the passive overvoltage trigger circuit, and the active overvoltage detection module is relied on to trigger the internal opening of the driver.

[0061] In another embodiment, see Fig.13 , the positive and negative poles of the measured voltage of the lower switch device are connected to the positive and negative poles of the support capacitor. When the support capacitor of the MMC sub-module is over-voltage, the passive overvoltage power supply circuit starts to work, and injects a turn-on trigger pulse current into the gate of the switch device through the passive trigger current shaping circuit to turn it on. The above process first occurs in the lower tube of the MMC sub-module. When the lower tube is triggered to turn on, the upper tube begins to bear pressure. When its passive overvoltage protection threshold is reached, the gate of the upper tube is injected with current, so that the upper tube is turned on and the bridge arm is directly connected. At this time, the loop composed of the upper tube, the lower tube and the support capacitor of the bridge arm will begin to flow through a very large current, causing the lower tube switch device to break down and enter a reliable direct-on state, so that the MMC sub-module can be reliably bypassed.

[0062] See also Fig.14 The passive overvoltage trigger circuit is set in the lower tube, injects the turn-on pulse current in an isolated manner, and has two isolated turn-on trigger pulse current injection channels. When the MMC submodule supports the capacitor overvoltage, the passive overvoltage power supply circuit starts to work, and injects the turn-on trigger pulse current into the gate of the switch device of the upper and lower tubes through the passive trigger current shaping circuit, so that they are turned on at the same time, thereby causing the lower tube switch device to break down and enter a reliable direct-through state, so that the MMC submodule is reliably bypassed.

[0063] See also Fig.15 , this implementation is applicable to the full-bridge MMC sub-module. One of the half-bridge arms uses overvoltage protection, and the other half-bridge arm is not modified. When the anode and cathode pressure of the switching device exceeds the overvoltage trigger threshold overvoltage, the passive overvoltage power supply circuit starts to work, and injects a turn-on trigger pulse current into the gate of the switching device through the passive trigger current shaping circuit to turn it on. When the upper and lower tubes are turned on at the same time, the energy released instantaneously will cause the switching device to break down and enter a reliable through-state, so that the MMC sub-module can be reliably bypassed. The implementation method of overvoltage protection of the switching device in the full-bridge MMC module is not limited to the implementation method in the figure, and the half-bridge MMC implementation methods in implementation methods 1-3 can all be used for the full-bridge MMC.

[0064] The present invention adopts a structure combining passive overvoltage detection and active overvoltage detection to realize overvoltage detection and protection function triggering. The components used are small in size and low in cost. It is easy to combine with the existing switch device-MMC topology and switch device drive. The active-passive overvoltage trigger coordination structure complements each other as a backup, is stable and reliable, easy to maintain, and has a very low possibility of false triggering. In the event of drive power failure or partial failure, the overvoltage protection action can still be effectively performed. It has high application value in MMC converter station engineering applications with high reliability requirements.

[0065] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An overvoltage protection device for a switching device, characterized in that: include: Passive overvoltage trigger circuit, switch device driving circuit and switch device; In the non-isolated working mode, the positive electrode of the passive overvoltage trigger circuit is connected to the target detection anode, and the negative electrode of the passive overvoltage trigger circuit is connected to the gate of the switching device; or the positive electrode of the passive overvoltage trigger circuit is connected to the target detection anode; In the isolated working mode, the positive and negative electrodes of the passive overvoltage trigger circuit are connected between the target detection anode and the target detection cathode respectively; The passive overvoltage trigger circuit comprises: a passive overvoltage power supply circuit and a passive trigger current shaping circuit; The positive electrode of the passive overvoltage power supply circuit is connected to the positive electrode of the voltage to be measured, and the negative electrodes of the passive overvoltage power supply circuit and the passive trigger current shaping circuit are connected to the negative electrode of the voltage to be measured; In the non-isolated mode, the positive electrode of the passive trigger current shaping circuit is connected to the gate of the switching device; in the isolated mode, the positive electrode of the passive trigger current shaping circuit is connected to the gate of the switching device, and the negative electrode is connected to the cathode of the switching device.

2. The overvoltage protection device according to claim 1, characterized in that: Also included is a feedback signal generating circuit; The feedback signal generating circuit is connected to the passive trigger current shaping circuit signal, and is used for receiving the passive trigger current shaping circuit action signal and outputting a feedback signal to the switch device driving circuit.

3. The overvoltage protection device according to claim 1, characterized in that: The passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a series connection of a nonlinear varistor-type breakdown diode, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

4. The overvoltage protection device according to claim 1, characterized in that: The passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a first transient voltage suppression diode connected in series, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

5. The overvoltage protection device according to claim 1, characterized in that: The passive overvoltage trigger circuit comprises: A passive overvoltage power supply circuit composed of a nonlinear varistor-type breakdown diode and a first transient voltage suppression diode connected in series, a passive trigger current shaping circuit composed of a current shaping resistor, and a feedback signal generating circuit; The feedback signal generating circuit is connected in parallel with the current shaping resistor; The passive overvoltage trigger circuit obtains the current of the anode of the power supply under test, generates an injection current through the passive trigger current shaping circuit and transmits it to the gate of the switching device.

6. The overvoltage protection device according to claim 3 or 4, characterized in that: The passive trigger current shaping circuit comprises: a thyristor and a first capacitor; The passive overvoltage trigger circuit is in a non-isolated injection working mode, the first capacitor is connected in parallel to both ends of the current shaping resistor, and the first capacitor is connected in parallel between the gate and cathode of the thyristor; The anode of the thyristor is connected to the anode terminal of the nonlinear voltage-sensitive element breakdown diode in the passive overvoltage power supply circuit.

7. The overvoltage protection device according to claim 1, characterized in that: The passive trigger current shaping circuit comprises: A voltage-stabilized power supply module, an on-pulse current shaping circuit, a drive pulse transformer, a first diode and a first switch, or a bidirectional switch formed by the first switch; The voltage-stabilized power supply module is electrically connected to the passive overvoltage power supply circuit; the voltage-stabilized power supply module, the opening pulse current shaping circuit and the driving pulse transformer are connected in parallel, and the opening pulse current shaping circuit is signal-connected to the overvoltage detection circuit; One end of the first secondary side of the driving pulse transformer is connected in series with the anode of the first diode, and the other end of the first secondary side of the driving pulse transformer is connected in series with the first end of the first switch; The cathode of the first diode is connected to the gate of the switching device, and the second end of the first switch is connected to the cathode of the switching device.

8. The overvoltage protection device according to claim 7, characterized in that: The passive trigger current shaping circuit further includes, in the isolation injection working mode: A second diode and a second switch, or a bidirectional switch formed by the second switch; One end of the second secondary side of the driving pulse transformer is connected in series with the anode of the second diode, and the other end of the second secondary side of the driving pulse transformer is connected in series with the first end of the second switch; The cathode of the second diode is connected to the gate of the switching device as a first gate output, and the second end of the second switch is connected to the cathode of the switching device as a first cathode; The cathode of the first diode is connected to the gate of the switching device as a second gate output, and the second end of the first switch is connected to the cathode of the switching device as a second cathode.

9. The overvoltage protection device according to claim 8, characterized in that: The passive trigger current shaping circuit further includes: The driving pulse transformer comprises a first primary side and a second primary side, the first primary side corresponds to a first secondary side, and the second primary side corresponds to a second secondary side; One end of the second secondary side of the driving pulse transformer is connected in series with the anode of the second diode, and the other end of the second secondary side of the driving pulse transformer is connected in series with the first end of the second switch; The first primary side is connected in parallel with the second primary side, and the first primary side and the second primary side are connected in parallel to the turn-on pulse current shaping circuit.

10. The overvoltage protection device according to claim 7, characterized in that: The passive trigger current shaping circuit is in the isolated current injection working mode, and the voltage regulated power supply module includes: a second capacitor, a first resistor, a third capacitor, and a second transient voltage suppression diode; The third capacitor and the second transient voltage suppression diode are connected in parallel, the cathode of the second transient voltage suppression diode is connected in series to one end of the first resistor, the other end of the first resistor and the anode of the second transient voltage suppression diode are connected to the first end and the second end of the second capacitor respectively, the first end of the second capacitor is connected to the passive overvoltage power supply, and the second end of the second capacitor is connected to the negative electrode of the measured voltage; The two ends of the third capacitor are connected to the on-pulse current shaping module; Turn on the pulse current shaping module, including: An overvoltage detection trigger enabling circuit, a PWM drive signal generating circuit and a power tube, wherein the overvoltage detection trigger enabling circuit is connected to the PWM drive signal generating circuit, and the PWM drive signal generating circuit is connected to the base of the power tube.

11. The overvoltage protection device according to claim 7, characterized in that: The passive trigger current shaping circuit turns on the pulse current shaping module in the isolated current injection working mode, including: a second resistor, a fourth capacitor, a bidirectional trigger diode, a fourth resistor and a second thyristor; The second resistor and the fourth capacitor form an RC circuit, and the first end of the second resistor is connected to the voltage-stabilized power supply module; The second end of the second resistor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the voltage-stabilized power supply module; The lead-out end between the second end of the second resistor and the first end of the fourth capacitor is connected to the first end of the bidirectional trigger diode, the second end of the bidirectional trigger diode is connected to the first end of the fourth resistor, the second end of the fourth resistor is connected to the gate of the second thyristor, the cathode of the second thyristor is connected to the second end of the fourth capacitor, and the anode of the second thyristor is connected to the pulse transformer.

12. An overvoltage protection system for a switching device, characterized in that: At least two switch devices are cascaded to form a first half-bridge submodule, wherein the positive and negative electrodes of the passive overvoltage trigger circuit are connected between the target detection anode and the gate of the switch device, and the switch device is connected in parallel with a freewheeling diode; Bridge arm capacitors are connected at both ends of the half-bridge submodule.

13. The overvoltage protection system according to claim 12, characterized in that: The first switch device is connected to the driving circuit, and the second switch device is connected to the passive overvoltage trigger and the driving circuit to form a second half-bridge submodule; The first gate output terminal of the passive overvoltage trigger and drive circuit is connected to the gate of the second switch device, and the second cathode of the passive overvoltage trigger and drive circuit is connected to the anode of the second switch device and the cathode of the first switch device; The second gate output terminal of the passive overvoltage trigger and drive circuit is connected to the gate of the first switching device; The driving circuit is connected to the gate and cathode of the first switching device.

14. The overvoltage protection system according to claim 13, characterized in that: include: A full-bridge circuit is obtained by cascading multiple second half-bridge sub-modules.

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