Modular multilevel converter and method for switching it

Abstract

The application provides a modular multilevel converter and a method and an electronic device for switching the same. The converter comprises a converter bridge arm, a power module, a damping module, a power module bypass switch and a damping module bypass switch. When the converter bridge arm is working in a fault current condition, the damping module valve control device receives a blocking signal, immediately blocks all damping module switches on the converter bridge arm, and connects a damping resistor to the converter circuit. When the damping module itself fails to bypass, the damping module valve control device sends a bypass command to the adjacent power module. When the damping module valve control device simultaneously detects the power module bypass and / or the damping module itself fails to bypass, the power module bypass switch is closed, the converter is bypassed, the damping module failure does not affect the continuous operation of the system, and the damping module failure information is sent. According to the technical scheme of the application, the bridge arm current can be quickly attenuated, and the bridge arm damping module failure can be processed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flexible direct current transmission of power system, in particular to a modular multilevel converter and a method for switching the same. BACKGROUND

[0002] With the increase of the design capacity of the flexible direct current converter, the impact of the flexible direct current line fault on the alternating current system also increases, and the requirement for the self-clearing and restarting capability of the flexible direct current line fault also increases. Without taking measures, the restarting time of the direct current line after the fault is long, which is in seconds, and is mainly limited by the time of opening the alternating current incoming line switch, the fault current decay and arc extinction time, and the time of opening and reclosing the direct current switch. Among them, the fault current decay and arc extinction time consume the longest time. At present, the direct current line fault solution is, for example, to use a direct current circuit breaker, or to use a full-bridge converter valve, or a double-clamp module. The above full-bridge module, double-clamp module, and improved double-module solution need to modify the structure of the converter valve. If it is considered in a new project, the cost and necessity also need to be considered.

[0003] In addition, in some applications of the flexible direct current bipolar half-bridge converter, when a valve side fault occurs, a fault current path is formed between the valve side grounding point and the direct current side, which also causes the problem of long time consumption of fault current decay and arc extinction. This problem may cause the current zero-crossing time of the alternating current side switch installation to be long, and the opening time of the alternating current side switch to be long.

[0004] In the prior art, a damping module is installed in the bridge arm of the converter valve, and each damping module is composed of a damping resistor and a damping module switch tube in parallel. In normal operation, the damping module switch tube in the damping module is turned on, and the damping resistor is bypassed. In the case of direct current fault, the damping module switch tube is locked, and the damping resistor flows through the fault current.

[0005] The inventor found that in some technical solutions in the prior art, an additional energy storage capacitor is added, which involves charging and energy supplement of the energy storage capacitor in the damping module circuit, and involves two operations of "starting forward current charging state" and "forward current energy supplement state". The two operations are related to the energy supplement of the energy storage capacitor, and additionally involve the operation of the additional switch tube. However, as described above, the fault condition in the actual operation of the technical solution is that the damping bypass switch cannot be closed due to the problem of the external energy supply system itself.

[0006] The control switching strategy of the damping module, such as how to accelerate the restart process after the DC line of the converter fails, and how to accelerate the process of opening the fault current of the AC side switch after the valve side of the converter fails, both of which require the interaction and cooperation between the valve control of the power module and the damping module in the converter, and there is no effective technical solution mentioned at present.

[0007] The above information disclosed in the background section is only intended to strengthen the understanding of the background of the present application, and therefore it can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0008] The present application provides a modular multilevel converter and a protection switching method thereof, which can realize rapid attenuation of bridge arm current effect and bridge arm damping module fault processing.

[0009] The features and advantages of the technical solutions of the present application will become apparent from the following detailed description, or will be learned partly by practice of the present application.

[0010] According to an aspect of the present application, a modular multilevel converter is provided, comprising: a converter bridge arm; a power module arranged on the converter bridge arm, the power module having a power module bypass switch; a damping module arranged on the converter bridge arm, taking power from an adjacent power module, connected in series with the power module, comprising a damping module switch tube and a damping resistor connected in parallel with the damping module switch tube, the power module bypass switch being connected across the adjacent power module and the damping module to bypass the adjacent power module and the damping module at the same time; a damping module valve control device connected with the damping module control and directly or indirectly controlling the adjacent power module bypass switch; and a power module valve control device connected with the power module control.

[0011] According to some embodiments, the damping module switch tube is an IGBT, IGCT, GTO or MOSFET.

[0012] According to some embodiments, the damping module further comprises a damping module bypass switch connected in parallel with the damping module and in interactive communication with the damping module valve control device.

[0013] According to some embodiments, the damping module valve control device is configured with or separate from the power module valve control device on the converter bridge arm.

[0014] According to another aspect of the present application, a switching method for the modular multilevel converter is provided. In the case that the damping module valve control device is used for normal unlocking operation of the converter bridge arm, the damping module valve control device bypasses the damping resistor by triggering the damping module switch tube; after receiving the blocking signal sent by the control protection device, all damping module switch tubes on the converter bridge arm are immediately blocked, and the damping resistor of the damping module is equivalent to being connected to the converter circuit; when the damping module itself fails to bypass, the damping module valve control information processor sends a bypass command to the adjacent power module, so that the adjacent power module bypass switch is closed.

[0015] According to some embodiments, the damping module valve control device sets the number of redundant damping modules on each converter bridge arm; when the damping module bypass failure is detected, the number of redundant damping modules is reduced by one; when the number of redundant damping modules is less than or equal to zero, the damping module valve control device sends a trip request.

[0016] According to some embodiments, the damping module valve control device detects the energy storage capacitor voltage of the power module, the state information of the power module, and the state information of the damping module.

[0017] According to some embodiments, the damping module valve control device communicates with the adjacent power module valve control device, and when the damping module itself fails to bypass, the damping module valve control device sends a bypass command to the adjacent power module to close the power module bypass switch, and receives the bypass information of the adjacent power module.

[0018] According to some embodiments, the damping module valve control device sends the damping module failure information to the background system when it detects that the adjacent power module bypasses and the damping module itself fails to bypass at the same time.

[0019] According to some embodiments, the modular multilevel converter further comprises a damping module bypass switch connected in parallel with the damping module and in communication with the damping module valve control device. When a damping module failure is detected, the damping module bypass switch detects: a failure of the damping module optocoupler power supply; a failure of the high-voltage power supply; a failure of the damping module uplink channel for sending signals to the damping valve control device; a failure of the damping valve control device downlink channel for sending instructions to the damping module; and a failure of the damping module to take power from the power module capacitor voltage below a certain value. The above damping module failures are sent as alarm information to the background system.

[0020] According to some embodiments, the damping valve control device takes power from the energy storage capacitor on the adjacent power module. When the damping module is connected to the energy storage capacitor voltage below a certain value, the damping module bypass switch is closed, and the under-voltage bypass damping module is closed.

[0021] According to an aspect of the present application, an electronic device is provided, including: one or more processors; a storage device for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors implement the method as described above.

[0022] According to the technical solution of the present application, the damping module switching method added on the multi-level converter bridge arm can ensure the normal operation of the damping module, and the normal operation of the entire converter system will not be affected by the bypass of the damping module due to the failure of the damping module.

[0023] By the method of switching the modular multi-level converter, the fault current decay and arc extinction time can be shortened, the release of residual energy in the bridge reactor after a fault occurs can be accelerated, the short-circuit current decay time can be reduced, and after this time is shortened, the entire process from detecting the DC line fault to restarting can be shortened to within 300ms-500ms by using a proper restart strategy, so that the processing capacity of the flexible DC for line faults is greatly improved, and the problem of line fault restart can be conveniently and low-costly solved.

[0024] On the other hand, when the AC valve side of the converter fails, the technical solution of the present application can reduce the time consumption of the current zero point at the installation position of the AC side switch, so that the opening time of the AC side switch is within the normal opening time range.

[0025] It should be understood that the above general description and the following detailed description are only exemplary and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art according to these drawings without departing from the scope of the present application.

[0027] Figure 1a A schematic diagram of a power module and a damping module converter bridge arm according to an exemplary embodiment is shown.

[0028] Figure 1b A flowchart of a modular multi-level converter switching method according to an exemplary embodiment is shown.

[0029] Figure 2 A schematic diagram of a power module and a damping module converter bridge arm according to another exemplary embodiment is shown.

[0030] Figure 3 A schematic diagram of a damping module valve control device configured alone according to an exemplary embodiment is shown.

[0031] Figure 4 A schematic diagram showing a damping module valve control device merged configuration with a power module valve control device according to an example embodiment.

[0032] Figure 5 A schematic diagram showing a damping module drawing power from an adjacent power module according to an example embodiment.

[0033] Figure 6 A block diagram showing an electronic device according to an example embodiment. DETAILED DESCRIPTION

[0034] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the several views.

[0035] The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the

[0036] Moreover, the terms "first," "second," "third," etc. are used herein to describe various objects, but do not imply an ordering or sequence unless specifically stated. Furthermore, the terms "comprise," "include," "have" and any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements, but can include other not expressly listed steps or elements, or can also include additional steps or elements that are inherent in such process, method, article, or apparatus.

[0037] The terms "first," "second," "third," etc. are used herein to describe various objects, but do not imply an ordering or sequence unless specifically stated. Furthermore, the terms "comprise," "include," "have" and any variations thereof, are intended to cover a non-exclusive inclusion.

[0038] Figure 1a A schematic diagram showing a power module and damping module converter bridge arm according to an example embodiment, Figure 2 A schematic diagram showing a power module and damping module converter bridge arm according to another example embodiment.

[0039] According to the embodiment, a plurality of damping modules 200 are installed on the upper and lower bridge arms of the converter, each of the damping modules 200 being composed of a damping resistor 203 and a damping module switch tube 202 in parallel.

[0040] In a normal operation condition, the damping module switch tube 202 in the damping module 200 is turned on, and the damping resistor 203 is bypassed; and in a DC fault condition, the damping module switch tube 202 is locked, and the damping resistor flows through the fault current.

[0041] When a fault occurs in the DC line of the converter, how to accelerate the restart process, and when a fault occurs in the valve side of the converter, how to accelerate the process of opening the fault current of the switch on the AC side, both of which require the interaction and cooperation between the valve control of the power module and the damping module in the converter, and there is no effective technical solution at present.

[0042] Therefore, the application provides a modular multilevel converter and a protection switching method to shorten the fault current decay and arc extinction time, accelerate the release of residual energy in the bridge reactor after a fault, reduce the short-circuit current decay time, and improve the processing capacity of flexible DC for line faults, which can be applied to fast and low-cost solutions for restarting problems caused by line faults.

[0043] Hereinafter, the example embodiments according to the application will be described in detail with reference to the accompanying drawings.

[0044] As shown in Figure 1a According to the example embodiments of the application, the converter bridge arm is composed of a power module 100 and a damping module 200, and the damping valve control device (not shown in the figure) of the damping module 200 bypasses the damping resistor 203 by triggering the damping module switch tube 202 in a normal unlocking operation condition of the converter bridge arm, the bypass switch 101 of the adjacent power module is connected to the damping module 200, and the damping module bypass switch 201 is connected in parallel with the damping module 200.

[0045] Specifically, the damping module switch tube 202 includes an IGBT and a freewheeling diode connected in anti-parallel to the IGBT, but the application is not limited thereto.

[0046] Optionally, the damping module switch tube 202 can be an IGBT, an IGCT, a GTO or a MOSFET.

[0047] Optionally, the power module bypass switch 101 remains in mechanical action after closing, and can remain in the closed state after receiving a closing signal.

[0048] According to the embodiment, the converter is locked after receiving the locking signal issued by the control protection device, and all the damping module switches 202 of the six converter arms are locked immediately, and the resistance 203 of the damping module of the six converter arms is equivalent to being connected to the converter circuit, thereby playing a role in quickly attenuating the current of the converter arm.

[0049] After the converter is locked, the locking signal received by the control protection device can be a normal locking condition, or an emergency locking condition in the case of a fault current 300 flowing through the power module 100 and the damping module 200 in the case of a DC line fault 500. Details will be described below. Figure 1b The damping module valve control device collects the state information of the power module 100 and the damping module 200, and the fault / alarm state information.

[0050] According to the embodiment, the damping valve control device of the damping module 200 takes power by connecting to the capacitor voltage of the adjacent power module 100, and the damping module valve control collects the bypass information of the adjacent power module 100. When the damping module 200 itself fails to bypass, the damping module valve control device sends a bypass command to the adjacent power module 100. When the damping module valve control device detects that the power module bypass switch 101 is closed and the damping module 200 itself fails at the same time, the damping module failure does not affect the continuous operation of the system, and the damping module valve control device collects the damping module failure alarm information.

[0051] According to the embodiment, the damping valve control device takes power by connecting to the energy storage capacitor on the adjacent power module 100. When the voltage of the energy storage capacitor connected by the damping module 200 is lower than a certain value, the damping module bypass switch 201 is closed, and the under-voltage bypass damping module 200.

[0052] According to the technical solution of the present application, the above method can ensure the normal operation of the damping module, and will not affect the normal operation of the entire converter system due to the failure of the damping module to bypass.

[0053] Figure 1b A flowchart of a method for switching a modular multilevel converter according to an example embodiment is shown.

[0054] Referring to Figure 1a In the embodiment of the application, in S101, in the case of normal unlocking operation of the converter arm, the damping module valve control device (not shown in the figure) bypasses the damping resistor 200 by triggering the conduction of the damping module switch 202.

[0055] After receiving the blocking signal sent by the control and protection device (not shown in the figure) at S103, the damping module switch tube 202 on the converter bridge arm is immediately blocked, and the damping resistance 203 of the damping module is equivalent to being connected to the converter circuit to attenuate the fault current.

[0056] When the damping module 200 itself fails to bypass at S105, the damping valve control device sends a bypass command to the adjacent power module 100, so that the adjacent power module bypass switch 101 is closed.

[0057] As shown in Figure 2 According to the example embodiments of the present application, as shown in the above valve side fault 500 case, after the converter is blocked, the damping valve control device blocks the damping module 200, and the resistance 203 of the damping module is equivalent to being connected to the converter bridge arm.

[0058] The fault current 300 flows through the power module 100, the damping module 200, and forms a loop through the DC side grounding point 400 and the fault point. The equivalent connection of the resistance 203 of the damping module will accelerate the attenuation of the converter bridge arm fault current 300 and speed up the disconnection time of the AC side switch.

[0059] According to the embodiments, the damping module valve control device sets the number of redundant damping modules on each converter bridge arm; when the damping module fails to bypass is detected, the number of redundant damping modules is reduced by one; when the number of redundant damping modules is less than or equal to zero, the damping module valve control device sends a trip request.

[0060] According to the embodiments, the damping module valve control device detects the energy storage capacitor voltage of the power module, the state information of the power module, and the state information of the damping module. When the damping valve control device detects the damping module fault information, the damping module fault information is sent as alarm information to the background system, specifically including: the optical coupling 24V power supply fault of the damping module; high voltage power supply fault; uplink channel fault of the damping module to the damping valve control device; downlink channel fault of the damping valve control device to the damping module; the voltage of the damping module taking energy from the power module capacitor is lower than the set value. The damping module valve control device, the power module valve control device, and the control and protection device all belong to the background system management.

[0061] According to the embodiments, the damping valve control device collects the bypass information of the adjacent power module 100 connected, and the damping valve control device can send a bypass command to the adjacent power module 100, and the bypass switch 101 of the adjacent power module 100 is connected across the damping module 201. In the case of simultaneously detecting the power module bypass switch 101 and the damping module 200 itself failure, the damping module failure does not affect the system to continue running, and only the damping module failure alarm information is sent.

[0062] Figure 3A schematic diagram of a separate configuration of the damping module valve control device according to an exemplary embodiment is shown. Figure 4 A schematic diagram of a combined configuration of the damping module valve control device and the power module valve control device according to an exemplary embodiment is shown.

[0063] Referring to Figure 3 , the valve control unit 3000 is optionally configured to separately connect the damping valve control device control board through the fiber interface board in the case of separate configuration of the damping module valve control device and the power module valve control device of the converter bridge arm.

[0064] Referring to Figure 4 , the valve control unit 4000 is optionally configured to connect the damping valve control device and the power module packaged control board through the fiber interface board in the case of combined configuration of the damping module 200 and the power module 100 in the case of combined configuration of the damping module valve control device and the power module valve control device of the converter bridge arm.

[0065] According to the technical solution of the present application, the structure of the converter does not need to be modified, and when a fault occurs in the DC line of the converter, the valve control devices of the power module and the damping module interact and cooperate, and a trip request is sent by detecting the number of redundant damping modules. The normal operation of the damping module can be ensured, and the normal operation of the entire converter system will not be affected by the bypass of the damping module due to the failure of the damping module.

[0066] Figure 5 A schematic diagram of the damping module taking power from the adjacent power module according to an exemplary embodiment is shown.

[0067] Referring to Figure 5 , according to the embodiment, the power module control board card 102 outputs the control signal of the power module valve control device, including the trigger signal of the upper and lower power switch tubes on the power module 100 and the trigger bypass signal of the power module bypass switch 101.

[0068] The damping module control board card 204 outputs the control signal of the damping module valve control device, including the trigger signal of the damping module switch tube 202 on the damping module 200 and the trigger bypass signal of the damping module bypass switch 201.

[0069] The power module control board card 102 and the damping module control board card 204 respectively obtain power supply energy through the power module power supply system and the damping module power supply system, so that the damping module valve control device is connected with the damping module control, and directly or indirectly controls the adjacent power module bypass switch 101.

[0070] According to some embodiments, the damping valve control device is powered by a damping module power supply system, which is powered by an energy storage capacitor on an adjacent module. When the voltage of the damping module switch tube 202 on the damping module 200 is lower than a certain value, the damping module bypass switch 201 is closed, and the damping module 200 is bypassed.

[0071] Figure 6 A block diagram of an electronic device according to an example embodiment is shown.

[0072] Reference will now be made to Figure 6 An electronic device 600 according to this implementation of the present application is described below. Figure 6 The electronic device 600 shown is merely an example and should not limit the function and scope of use of the embodiments of the present application in any way.

[0073] As Figure 6 shown, the electronic device 600 is in the form of a general computing device. The components of the electronic device 600 can include, but are not limited to, at least one processing unit 610, at least one storage unit 620, a bus 630 connecting different system components, including the storage unit 620 and the processing unit 610, a display unit 640, and the like.

[0074] The storage unit stores program code that can be executed by the processing unit 610, so that the processing unit 610 performs the methods described in this specification according to various example implementations of the present application.

[0075] The bus 630 can represent one or more of several types of bus structures, including a storage unit bus or storage unit controller, a peripheral bus, a graphics acceleration port, a processing unit, or a local bus using any of a variety of bus structures.

[0076] Electronic device 600 can also communicate with one or more external devices 700 (e.g., keyboard, pointing device, Bluetooth device, etc.), and with one or more devices that enable a user to interact with electronic device 600, and / or with any device that enables electronic device 600 to communicate with one or more other computing devices (e.g., router, modem, etc.). This communication can be performed via input / output (I / O) interface 650. Furthermore, electronic device 600 can also communicate with one or more networks (e.g., local area network (LAN), wide area network (WAN), and / or public networks, such as the Internet) via network adapter 660. Network adapter 660 can communicate with other modules of electronic device 600 via bus 630. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with electronic device 600, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0077] According to embodiments of this application, the switching method of a modular multilevel converter with a damping module can, on the one hand, shorten the fault current decay and arc extinction time, accelerate the release of residual energy in the bridge arm reactor after a fault, and reduce the short-circuit current decay time. After shortening this time, with the aid of an appropriate restart strategy, the entire process from detecting a DC line fault to restarting will be shortened to within 300ms to 500ms, which greatly advances the ability of flexible DC to handle line faults and can conveniently and cost-effectively solve some applications that require line fault restarting. On the other hand, when there is a fault on the AC valve side of the converter, the technical solution of this application can reduce the time of the current zero crossing at the AC side switch installation point, thereby ensuring that the AC side switch disconnection time is within the normal disconnection time range.

[0078] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this application. Furthermore, any changes or modifications made by those skilled in the art based on the ideas of this application, and on the specific implementation methods and application scope of this application, are all within the scope of protection of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for switching modular multilevel converters, characterized in that, The modular multilevel converter includes: a converter arm, a power module, a damping module, a damping module valve control device, and a power module valve control device. The power module and the damping module are connected in series and mounted on the converter arm. The power module includes a power module bypass switch, and the damping module includes a damping module switch transistor and a damping resistor connected in parallel with the damping module switch transistor. The power module bypass switch is connected across adjacent power modules and damping modules to simultaneously bypass adjacent power modules and damping modules. The damping module valve control device is controlled by the damping module. The method includes: Under normal unlocked operation of the converter arm, the damping module valve control device bypasses the damping resistor by triggering the conduction of the damping module switching transistor; Upon receiving the blocking signal from the control and protection equipment, the switching transistor of the damping module on the converter bridge arm immediately blocks, and the damping resistor of the damping module is effectively connected to the converter circuit to attenuate the fault current. When the damping module itself fails and cannot bypass, the damping module valve control device sends a bypass command to the adjacent power module, causing the bypass switch of the adjacent power module to close.

2. The method according to claim 1, characterized in that, Also includes: The damping module valve control device sets the number of redundant damping modules on each of the converter bridge arms; When a fault bypass of the damping module is detected, the number of redundant damping modules is reduced by one. When the number of redundant damping modules is less than or equal to zero, the damping module valve control device issues a trip request.

3. The method according to claim 1, characterized in that, Also includes: The damping module valve control device detects the energy storage capacitor voltage of the power module, the status information of the power module, and the status information of the damping module.

4. The method according to claim 1, characterized in that, The damping module valve control device communicates with the adjacent power module valve control device. When the damping module itself fails and cannot bypass, the damping module valve control device sends a bypass command to the adjacent power module to close the bypass switch of the power module, and at the same time receives the bypass information of the adjacent power module.

5. The method according to claim 1, characterized in that, When the damping module valve control device simultaneously detects that the adjacent power module is bypassed and the damping module itself is faulty and cannot be bypassed, it sends the damping module fault information to the background system.

6. The method as described in claim 2, characterized in that, The modular multilevel converter also includes a damping module bypass switch connected in parallel with the damping module. When the damping module valve control device detects a damping module fault, it closes the damping module bypass switch. The damping module fault includes one or more of the following: The optical coupler power supply of the damping module failed. High-voltage power supply failure; The damping module uploads a signal to the uplink channel of the damping valve control device due to a fault. The damping valve control device sends a command to the downlink channel of the damping module indicating a fault; The damping module detects faults where the voltage of the energy storage capacitor in the power module is lower than a predetermined value. Among them, the aforementioned damping module failure is sent as an alarm message to the back-end system.

7. The method according to claim 6, characterized in that, When the voltage of the energy storage capacitor of the power module falls below a certain value, the damping module is undervoltage bypassed.

8. A modular multilevel converter, characterized in that, The modular multilevel converter is used to perform the method as described in any one of claims 1-7, the modular multilevel converter comprising: Converter bridge arm; Power module; The damping module draws energy from the adjacent power module; Damping module valve control equipment directly or indirectly controls the bypass switch of adjacent power modules; A power module valve control device, connected to the power module control.

9. The modular multilevel converter according to claim 8, characterized in that, It also includes a damping module bypass switch, which is connected in parallel with the damping module and communicates with the valve control device of the damping module.

10. The modular multilevel converter according to claim 8, characterized in that, The damping module switching transistor is an IGBT, IGCT, GTO, or MOSFET.

11. The modular multilevel converter according to claim 8, characterized in that, The damping module valve control device is configured in the same device or separately from the power module valve control device on the converter bridge arm.

12. An electronic device, characterized in that, include: One or more processors; Storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the method as described in any one of claims 1-7.

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