A commutation control method and system for a controllable commutation converter

Abstract

A commutation control method and system for a controllable commutation converter, which detects the DC side voltage and current of the converter at the receiving end of the DC transmission line, and respectively controls the commutation valve group to perform commutation control operations under different states according to the different power magnitudes on both sides of the converter, the pre-judged faults on the AC side and the different fault types. When the AC side operates normally, the control operations of each commutation valve group are carried out according to the normal time sequence. When the current of the current commutation valve group is less than the turn-off current reference value, the current is transferred from the main branch to the auxiliary branch, and then transferred to the next commutation valve group to be commutated through the auxiliary branch; when a fault occurs on the AC side, the turn-off current reference value is adaptively adjusted according to the fault type, and the arrester branch is put into operation while the auxiliary branch is turned off until the main branch current of the next commutation valve group is fully established, and then the arrester branch of the current commutation valve group is disconnected. The present invention realizes different commutation operations based on different conditions, and can effectively avoid the commutation failure of the commutation valve group.

Description

Technical Field

[0001] The present invention belongs to the technical field of power systems, relates to high-voltage direct current (HVDC) transmission technology, and particularly relates to a commutation control method and system for a controllable commutation converter. Background Art

[0002] The wiring modes of converters are diverse, and among them, the three-phase bridge inverter is a circuit form commonly adopted by HVDC transmission converters. For a converter to operate in the inverter state, the following three conditions need to be met:

[0003] (1) The no-load DC voltage of the rectifier must be greater than the no-load DC voltage of the inverter.

[0004] (2) The inverter must also be provided with commutation current by the AC system to ensure that the inverter bridge arms commutate in the correct order. When the six bridge arms of the inverter conduct in sequence, the DC current flows through the valve-side windings of the commutation transformer in sequence, and at this time, corresponding currents will be induced in the grid-side windings, realizing the function of the inverter to convert DC to AC.

[0005] (3) There must be a large enough turn-off angle to ensure safe operation. The characteristics of thyristors determine that they must withstand a negative voltage for a time longer than the reverse turn-off time to turn off reliably. Therefore, when the inverter operates, it is necessary to ensure a sufficient turn-off angle to avoid the bridge arm conducting again when the positive voltage comes, resulting in reverse commutation.

[0006] During the commutation process, if the valve that has just exited conduction fails to recover its blocking ability during the reverse voltage period, or if the commutation process has not ended during the reverse voltage period, it will cause the pre-conducting valve to commutate to the pre-turn-off valve when the valve voltage turns positive, resulting in commutation failure. Commutation failure causes the DC reverse voltage of the inverter to decrease and the DC current to increase for a period of time. The existing technology can only avoid commutation failure under relatively minor and short-duration AC faults; due to the overly complex combined control logic between the controllable capacitor and the converter, it severely restricts the engineering practicability of the converter.

[0007] The prior art CN202111356001.6 discloses a commutation control method, device, converter and readable storage medium for a converter. Among them, the converter includes a plurality of converter valves, and each converter valve includes a main branch and an auxiliary branch. The method includes: obtaining the DC current on the receiving end DC side corresponding to the converter and the first commutation current, where the first commutation current is used to represent the conduction state of the first converter valve; calculating a second commutation current based on the DC current and the first commutation current, where the second commutation current is used to represent the turn-off state of the second converter valve; determining whether the second commutation current is less than a preset value; when the second commutation current is less than the preset value, performing a commutation operation from the main branch of the second converter valve to the auxiliary branch. This patent solution proposes to ensure the operation stability of commutation by adding an auxiliary branch. However, this patent does not consider the influence of DC power and AC faults on commutation, and cannot ensure successful commutation in case of faults.

[0008] The prior art CN202111353541.9 discloses a commutation control method, device, electronic device and readable storage medium for a converter. The method includes: obtaining the commutation state of the converter; determining whether the commutation state is normal; when the commutation state is abnormal, controlling the converter to start an energy consumption mode and adjusting the energy consumption parameters of the converter. Although this patent technical solution considers that AC side faults will cause commutation failure and proposes to reduce the influence of AC faults on commutation by adjusting the energy consumption parameters of the converter. However, this solution does not consider the influence of DC side power, nor does it implement different control strategies for different AC side faults. The MOV1 and MOV2 incorporated in the auxiliary branch always form a path, which will inevitably affect the current transfer from the main branch to the auxiliary branch and the transfer of the auxiliary branch to the next valve group of commutation. Summary of the Invention

[0009] To solve the problem of commutation failure of the converter caused by DC side power and AC side faults, the present invention provides a commutation control method and system for a controllable commutation converter.

[0010] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions.

[0011] On the one hand, the present invention discloses a commutation control method for a controllable commutation converter. The converter includes VT1-VT6 converter valve groups, and each converter valve group includes a main branch, an auxiliary branch and a controllable lightning arrester branch connected in parallel. The main branch includes a main branch thyristor valve V11, a main branch IGBT valve V12 and a second thyristor valve V122 connected in parallel therewith. The auxiliary branch includes an auxiliary branch IGBT valve V13 and an auxiliary branch thyristor valve V14; characterized in that the method includes the following steps:

[0012] Step 1: Detect the DC-side voltage and current of the receiving-end converter of the DC transmission line, the three-phase voltage and current on the AC side in real time, and calculate the DC-side power and the AC-side power , when > , enter Step 2, otherwise enter Step 6;

[0013] Step 2: Put into operation the main branch and the auxiliary branch in each converter valve group, and disconnect the controllable arrester branch;

[0014] Step 3: Judge the operating state of the AC side according to the three-phase voltage and current on the AC side. When there is no fault on the AC side, enter Step 4 for commutation operation, otherwise enter Step 5 for commutation operation;

[0015] Step 4: After receiving the valve control instruction, when the current of the current-phase converter valve group is less than the turn-off current reference value , transfer the current from the main branch to the auxiliary branch, and then transfer it to the next converter valve group to be commutated through the auxiliary branch;

[0016] Step 5: After receiving the valve control instruction, adaptively adjust the turn-off current reference value to according to the fault type, and at the same time of turning off the auxiliary branch, put into operation the arrester branch until the main branch current of the next converter valve group is fully established, and then disconnect the arrester branch of the current valve group;

[0017] Step 6: Block the main-branch IGBT valve V12, close the second thyristor valve in parallel with the main-branch IGBT valve, block the auxiliary-branch IGBT valve V13, disconnect the arrester branch, and perform the control operation of each converter valve group according to the normal operation timing.

[0018] The present invention further includes the following preferred solutions:

[0019] In Step 2, put into operation the main-branch thyristor valve V11 and the main-branch IGBT valve V12, and at the same time block the second thyristor valve V122 in parallel with the main-branch IGBT valve V12; put into operation the auxiliary-branch thyristor V14, put into operation the auxiliary-branch IGBT valve V13, and disconnect the arrester branch.

[0020] Further preferably,

[0021] In Step 3, the operating state of the AC side includes the normal operating state and the fault operating state, where the fault operating state includes single-phase short-circuit faults and inter-phase short-circuit faults.

[0022] Further preferably,

[0023] In Step 4, the turn-off current reference value I d_offSet to 0.15 - 0.25 times the DC pole current rating.

[0024] Further preferably,

[0025] In step 6, control operations of each converter valve group are carried out according to the normal operation timing, specifically including:

[0026] Receive the valve control instruction, and simultaneously trigger and conduct the main branch thyristor valve V11 and the main branch IGBT valve V12 of the current-phase converter valve group. When the commutation turn-off current of this valve group is less than the turn-off current reference value I d_off , turn off the main branch IGBT valve V12, close the auxiliary branch IGBT valve V13 and the auxiliary branch thyristor valve V14, so that the valve current is transferred from the main branch to the auxiliary branch. After a set fixed time delay, the auxiliary branch IGBT valve V13 is turned off, and the current is transferred to the next converter valve group.

[0027] Further preferably,

[0028] In step 5, when a single-phase short-circuit fault occurs on the AC side, adaptively adjust the turn-off current reference value to ;

[0029]

[0030] Wherein, is the turn-off current reference value after adaptive adjustment, is the amplitude of the zero-sequence voltage on the AC side, is the rated voltage amplitude on the AC side.

[0031] Further preferably,

[0032] In step 5, when an inter-phase short-circuit fault occurs on the AC side, adaptively adjust the turn-off current reference value to ;

[0033]

[0034] Wherein, is the short-circuit current value, is the rated current value, is the minimum amplitude of the three-phase voltage during the short-circuit fault, is the DC pole current rating, is the current weight, is the voltage weight, .

[0035] Further preferably,

[0036] When the AC fault is a two-phase short circuit, , ;

[0037] When the AC fault is a three-phase short circuit, , .

[0038] On the other hand, the present invention discloses a commutation control system for a controllable commutation converter using the foregoing commutation control method, including electrical quantity measurement modules on both sides of the converter, AC-DC power calculation modules, AC-side fault detection modules, turn-off current reference value calculation modules, and valve group commutation operation modules; characterized in that:

[0039] The electrical quantity measurement modules on both sides of the converter detect the DC-side voltage and current of the receiving-end converter of the DC transmission line, and the three-phase voltage and current on the AC side in real time;

[0040] The AC-DC power calculation module calculates the DC-side power and the AC-side power. When the DC-side power is not greater than the AC-side power, the valve group commutation operation module performs the following operations: locking the main-branch IGBT valve V12, closing the second thyristor valve in parallel with the main-branch IGBT valve, locking the auxiliary-branch IGBT valve V13, disconnecting the arrester branch, and performing the control operations of each converter valve group according to the normal operation timing;

[0041] When the DC-side power is greater than the AC-side power and the AC-side fault detection module determines that the AC side is operating normally, the valve group commutation operation module performs the following operations: performing the control operations of each converter valve group according to the normal operation timing. After receiving the valve control instruction, when the current of the current-phase converter valve is less than the turn-off current reference value , the current is transferred from the main branch to the auxiliary branch and then transferred to the next converter valve group through the auxiliary branch;

[0042] When the DC-side power is greater than the AC-side power and the AC-side fault detection module determines that the AC side is operating under a short-circuit fault, the valve group commutation operation module performs the following operations: adaptively adjusting the turn-off current reference value to , and then controlling the valve group commutation operation according to the same timing as the normal operation.

[0043] The present invention also discloses a computer-readable storage medium storing one or more programs, characterized in that the one or more programs include instructions that, when executed by a computing device, cause the computing device to execute any one of the foregoing commutation control methods.

[0044] A computing device, characterized by including:

[0045] One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and configured to be executed by the one or more processors, and the one or more programs include instructions for performing any of the commutation control methods described above.

[0046] Compared with the prior art, the present invention has the following beneficial technical effects.

[0047] (1) By providing an independently controllable arrester branch, the present invention can timely control the input and disconnection of the arrester, without affecting the orderly commutation operation under normal operating conditions. Moreover, when a fault occurs on the AC side, the present invention can rely on the arrester to establish a forced commutation voltage, successfully complete the commutation, and avoid commutation failure.

[0048] (2) By connecting a second thyristor across the main branch IGBTs, when the DC side power is not greater than the AC side power, the present invention can effectively block the main branch IGBTs and withdraw from the auxiliary branch, adopting the natural commutation method, which improves the commutation reliability when the DC side power is not greater than the AC side power.

[0049] (3) For different AC side faults, an algorithm for adaptively adjusting the reference value of the turn-off current is proposed, so that the converter can reliably complete the active commutation operation under different fault types. Description of the Drawings

[0050] Figure 1 is a schematic diagram of the topology structure of a controllable commutation converter;

[0051] Figure 2 is of the present invention Figure 1 a schematic diagram of the structure of each commutation valve group;

[0052] Figure 3 is a schematic flowchart of the commutation control method for the controllable commutation converter of the present invention. Detailed Embodiments

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only a part of the embodiments of the present invention, rather than all embodiments. Based on the spirit of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0054] Such as Figure 1As shown in the figure, it is the topological structure of a controllable phase-shifting converter. The converters in the converter station are all composed of 6-pulse or 12-pulse converters. In a DC transmission project, in order to increase the output DC voltage level, the DC terminals of two converter valves can be connected in series to form a 12-pulse converter. However, the two series-connected 6-pulse converter valves are decoupled. The embodiments of this application are introduced based on a 6-pulse inverter. The basic structure of a 6-pulse inverter is as Figure 1 shown, and its DC side is connected to the output terminal of the rectifier, L d denotes the smoothing reactor, and the AC side is connected to e a , e b , e c which respectively represent the equivalent phase voltages of the AC system. L μ is the per-phase equivalent inductance of the AC system. The converter includes a valve group VT1-VT6. VT1, VT3, and VT5 form the cathode half-bridge, and VT4, VT6, and VT2 form the anode half-bridge. VT1, VT3, and VT5 are respectively connected to VT4, VT6, and VT2 correspondingly.

[0055] In order to achieve the invention object of the present invention, Figure 2 shows the structure of each converter valve group of the present invention. Figure 1 In the present invention, each converter valve group VT1-VT6 includes a main branch, an auxiliary branch, and a lightning arrester branch. Among them, the main branch includes a main branch thyristor valve V11, a main branch IGBT valve V12, and a second thyristor valve V122 connected in parallel with the main branch IGBT valve V12; the auxiliary branch includes an auxiliary branch IGBT valve V13 and an auxiliary branch thyristor valve V14; in the embodiments of the present invention, an independently controllable lightning arrester branch including a switch K and a lightning arrester Arr is also provided.

[0056] Figure 3 is a schematic flow chart of the phase-shifting control method of the controllable phase-shifting converter of the present invention. The phase-shifting control method of the controllable phase-shifting converter disclosed by the present invention includes the following steps:

[0057] Step 1: Real-time detect the DC side voltage and current of the converter at the receiving end of the DC transmission line, the three-phase voltage and current of the AC side, and calculate the DC side power and the AC side power . During normal operation, > , enter Step 2 for phase-shifting control operation, otherwise enter Step 6 for phase-shifting control operation;

[0058] In this application, when the DC-side power drops below the AC-side power, the commutation operation is carried out in the manner of Step 6; otherwise, it proceeds to Step 2.

[0059] Step 2: Energize the main branch and the auxiliary branch in each converter valve group, and disconnect the arrester branch;

[0060] Energize the main-branch thyristor valve V11, energize the main-branch IGBT valve V12, and at the same time block the second thyristor valve V122 in parallel with the main-branch IGBT valve V12; energize the auxiliary-branch thyristor valve V14, energize the auxiliary-branch IGBT valve V13, and disconnect the arrester branch.

[0061] Step 3: Based on the three-phase voltage and current on the AC side, judge the operating state of the AC side. When there is no fault on the AC side, proceed to Step 4 for commutation operation; otherwise, proceed to Step 5 for commutation operation;

[0062] Among them, the operating state of the AC side includes the normal operating state and the fault operating state, and the fault operating state includes single-phase short-circuit faults and inter-phase short-circuit faults.

[0063] Step 4: Carry out the control operations of each converter valve group according to the normal operating timing. After receiving the valve control instruction, control the current converter valve in the current phase to transfer from the main branch to the auxiliary branch when the current is less than the turn-off current reference value and then transfer to the next converter valve group through the auxiliary branch;

[0064] Turn-off current reference value I d_off is set to 0.15 - 0.25 times the rated value of the DC pole current.

[0065] Carry out the control operations of each converter valve group according to the normal operating timing, specifically including:

[0066] Receive the valve control instruction, and at the same time trigger and conduct the main-branch thyristor valve V11 and the main-branch IGBT valve V12 of the current-phase converter valve group. When the commutation turn-off current of this valve group is less than the turn-off current reference value I d_off turn off the main-branch IGBT valve V12, close the auxiliary-branch IGBT valve V13 and the auxiliary-branch thyristor valve V14, so that the valve current is converted from the main branch to the auxiliary branch. After a set fixed time delay, the auxiliary-branch IGBT valve V13 is turned off, and the current is transferred to the next converter valve group.

[0067] Step 5: The commutation sequence is the same as the normal operating timing. After receiving the valve control instruction, adaptively adjust the turn-off current reference value to according to the fault type, and at the same time, when the auxiliary branch is turned off, energize the arrester branch until the main-branch current of the next converter valve group is fully established, and disconnect the arrester branch of the current valve group;

[0068] In step 5,

[0069] 5.1 When a single-phase short-circuit fault occurs on the AC side, adaptively adjust the turn-off current reference value to ;

[0070]

[0071] wherein, is the turn-off current reference value after adaptive adjustment, is the amplitude of the zero-sequence voltage on the AC side, is the rated voltage amplitude on the AC side.

[0072] 5.2 When an inter-phase short-circuit fault occurs on the AC side, adaptively adjust the turn-off current reference value to ;

[0073]

[0074] wherein, is the short-circuit current value, is the rated current value, is the minimum amplitude of the three-phase voltage during the short-circuit fault, is the rated value of the DC pole current, is the current weight, is the voltage weight, .

[0075] In a preferred embodiment of the present invention,

[0076] when the AC fault is a two-phase short circuit, , ;

[0077] when the AC fault is a three-phase short circuit, , .

[0078] This application also discloses a commutation control system for a controllable commutation converter of the foregoing commutation control method, including an electrical quantity measurement module on both sides of the converter, an AC-DC power calculation module, an AC-side fault detection module, a turn-off current reference value calculation module, and a valve group commutation operation module;

[0079] The electrical quantity measurement module on both sides of the converter detects the DC-side voltage and current of the receiving-end converter of the DC transmission line and the three-phase voltage and current on the AC side in real time;

[0080] The AC / DC power calculation module calculates the DC-side power and the AC-side power. When the DC-side power is not greater than the AC-side power, the valve group commutation operation module performs the following operations: blocking the main-branch IGBT valve V12, closing the second thyristor valve in parallel with the main-branch IGBT valve, blocking the auxiliary-branch IGBT valve V13, disconnecting the arrester branch, and controlling the operation of each converter valve group according to the normal operation timing;

[0081] When the DC-side power is greater than the AC-side power and the AC-side fault detection module determines that the AC side is operating normally, the valve group commutation operation module performs the following operations: controlling the operation of each converter valve group according to the normal operation timing. After receiving the valve control instruction, when the current of the current-phase converter valve is less than the turn-off current reference value the current is transferred from the main branch to the auxiliary branch and then transferred to the next converter valve group through the auxiliary branch;

[0082] When the DC-side power is greater than the AC-side power and the AC-side fault detection module determines that the AC side is operating in a short-circuit fault, the valve group commutation operation module performs the following operations: adaptively adjusting the turn-off current reference value according to the fault type and then controlling the valve group commutation operation according to the same timing as the normal operation.

[0083] The present invention also discloses a computer-readable storage medium storing one or more programs, characterized in that the one or more programs include instructions which, when executed by a computing device, cause the computing device to execute any one of the commutation control methods described above.

[0084] A computing device, characterized in that it includes:

[0085] One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing any one of the commutation control methods described above.

[0086] The present disclosure may be a system, a method, and / or a computer program product. The computer program product may include a computer-readable storage medium having thereon computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0087] A computer-readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. A computer-readable storage medium may be, for example—but not limited to—an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer-readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disc (DVD), a memory stick, a floppy disk, a mechanically encoded device such as a punched card or raised structures in grooves having instructions stored thereon, and any suitable combination of the foregoing. The computer-readable storage medium as used herein is not construed as being a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., an optical pulse through an optical fiber cable), or an electrical signal transmitted through a wire.

[0088] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to respective computing / processing devices, or can be downloaded to an external computer or an external storage device through a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network may include a copper transmission cable, an optical fiber transmission, a wireless transmission, a router, a firewall, a switch, a gateway computer, and / or an edge server. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in a computer-readable storage medium in each computing / processing device.

[0089] Computer program instructions for performing the operations of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine - related instructions, microcode, firmware instructions, state - setting data, or source code or object code written in any combination of one or more programming languages, including object - oriented programming languages such as Smalltalk, C++, etc., and conventional procedural programming languages such as the "C" language or similar programming languages. The computer - readable program instructions may be executed entirely on the user's computer, partially on the user's computer, executed as a stand - alone software package, partially on the user's computer and partially on a remote computer, or entirely on the remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., through the Internet using an Internet service provider). In some embodiments, by using the state information of the computer - readable program instructions to customize an electronic circuit, such as a programmable logic circuit, a field - programmable gate array (FPGA), or a programmable logic array (PLA), the electronic circuit can execute the computer - readable program instructions to implement various aspects of the present disclosure.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: it is still possible to modify the specific embodiments of the present invention or make equivalent substitutions, and any modification or equivalent substitution that does not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. A commutation control method for a controllable commutation converter. The converter includes a commutation valve group VT1-VT6. Each commutation valve group includes a main branch, an auxiliary branch, and a controllable lightning arrester branch connected in parallel. The main branch includes a main branch thyristor valve V11, a main branch IGBT valve V12, and a second thyristor valve V122 connected in parallel therewith. The auxiliary branch includes an auxiliary branch IGBT valve V13 and an auxiliary branch thyristor valve V14; characterized in that, The method includes the following steps: Step 1: Detect the DC side voltage and current of the receiving converter of the DC transmission line, and the three-phase voltage and current on the AC side in real time, and calculate the DC side power and the AC side power , when > , enter Step 2, otherwise enter Step 6; Step 2: Energize the main branch and the auxiliary branch in each converter valve group, and disconnect the controllable arrester branch; Step 3: Judge the operating state of the AC side according to the three-phase voltage and current on the AC side. When there is no fault on the AC side, proceed to Step 4 for commutation operation; otherwise, proceed to Step 5 for commutation operation; Step 4: After receiving the valve control instruction, when the current of the current phase converter valve group is less than the reference value of the turn-off current, transfer the current from the main branch to the auxiliary branch, and then transfer it to the next converter valve group to be commutated through the auxiliary branch; when the current is less than the turn-off current reference value, transfer the current from the main branch to the auxiliary branch, and then transfer it to the next converter valve group to be commutated through the auxiliary branch; Step 5: After receiving the valve control instruction, adaptively adjust the turn-off current reference value according to the fault type to , and while turning off the auxiliary branch, switch on the arrester branch until the main branch current of the next converter valve group is fully established, and then disconnect the arrester branch of the current valve group; is the amplitude of the zero-sequence voltage on the AC side, is the rated voltage amplitude on the AC side, is the short-circuit current value, is the rated current value, is the minimum amplitude of the three-phase voltage during a short-circuit fault, is the rated value of the DC pole current, is the current weight, is the voltage weight, ; Step 6: Block the IGBT valve V12 of the main branch, close the second thyristor valve in parallel with the IGBT valve of the main branch, block the IGBT valve V13 of the auxiliary branch, disconnect the arrester branch, and perform the control operation of each converter valve group according to the normal operation timing.

2. The commutation control method of the controllable commutation converter according to claim 1, wherein: In Step 2, energize the thyristor valve V11 of the main branch and the IGBT valve V12 of the main branch, and at the same time block the second thyristor valve V122 in parallel with the IGBT valve V12 of the main branch; energize the thyristor valve V14 of the auxiliary branch, energize the IGBT valve V13 of the auxiliary branch, and disconnect the arrester branch.

3. The commutation control method of the controllable commutation converter according to claim 2, wherein: In Step 3, the operating state of the AC side includes a normal operating state and a fault operating state, and the fault operating state includes a single-phase short-circuit fault and an inter-phase short-circuit fault.

4. The commutation control method of the controllable commutation converter according to claim 1 or 3, wherein: In step 4, the turn-off current reference value I d_off is set to 0.15 - 0.25 times the DC pole current rating.

5. The commutation control method of the controllable commutation converter according to claim 4, wherein: In Step 6, perform the control operation of each converter valve group according to the normal operation timing, specifically including: Receive the valve control instruction, and simultaneously trigger the conduction of the main branch thyristor valve V11 and the main branch IGBT valve V12 of the current phase converter valve group. When the commutation turn-off current of this converter valve group is less than the turn-off current reference value I d_off turn off the main branch IGBT valve V12, close the auxiliary branch IGBT valve V13 and the auxiliary branch thyristor valve V14, so that the valve current is transferred from the main branch to the auxiliary branch. After a set fixed time delay, the auxiliary branch IGBT valve V13 is turned off, and the current is transferred to the next converter valve group.

6. The commutation control method of the controllable commutation converter according to claim 1, wherein: When the AC fault is a two-phase short circuit, , ; When the AC fault is a three-phase short circuit, , .

7. A commutation control system for a controllable commutation converter using the method according to any one of claims 1-6, comprising an electrical quantity measurement module on both sides of the converter, an AC / DC power calculation module, an AC side fault detection module, a turn-off current reference value calculation module, and a valve group commutation operation module; wherein: The electrical quantity measurement module on both sides of the converter detects the DC side voltage and current of the receiving-end converter of the DC transmission line, and the three-phase voltage and current of the AC side in real time; The AC / DC power calculation module calculates the DC side power and the AC side power. When the DC side power is not greater than the AC side power, the valve group commutation operation module performs the following operations: block the IGBT valve V12 of the main branch, close the second thyristor valve in parallel with the IGBT valve of the main branch, block the IGBT valve V13 of the auxiliary branch, disconnect the arrester branch, and perform the control operation of each converter valve group according to the normal operation timing; When the DC-side power is greater than the AC-side power and the AC-side fault detection module determines that the AC side is operating normally, the valve group commutation operation module performs the following operations: Control the commutation valves of each converter valve group according to the normal operation timing. After receiving the valve control instruction, when the current of the current-phase commutation valve is less than the turn-off current reference value transfer the current from the main branch to the auxiliary branch, and then transfer it to the next converter valve group through the auxiliary branch; When the DC-side power is greater than the AC-side power and the AC-side fault detection module determines that the AC-side has a short-circuit fault and is operating, the valve group commutation operation module performs the following operations: adaptively adjusts the turn-off current reference value according to the fault type to , and then controls the valve group commutation operation according to the same time sequence as in normal operation.

8. A computer-readable storage medium storing one or more programs, characterized in that, The one or more programs include instructions that, when executed by a computing device, cause the computing device to execute any one of the methods according to claims 1-6.

9. A computing device, characterized in that, Including: One or more processors, one or more memories, and one or more programs, wherein the one or more programs are stored in the one or more memories and are configured to be executed by the one or more processors, and the one or more programs include instructions for executing any one of the methods according to claims 1-6.

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