Controllable phase commutated converter bypass pair injection method and system

Abstract

The application discloses a controllable phase-changing converter bypass pair input method and system. When a bypass pair input signal is received, the latest conducting converter valve and the bypass pair to be input are determined according to a trigger signal sent by a valve control system, so that the bypass pair can be formed at the fastest speed, and the control strategy is compatible with an existing direct current engineering bypass pair input strategy. By controlling the operation state of the latest conducting converter valve, the main branch current of the latest conducting converter valve is first introduced into an auxiliary branch, and then the auxiliary branch current is introduced into the main branch after the main branch current is zero-crossed; the main branch of the opposite valve of the bypass pair to be input is conducted, so that the protection effect of the main branch saturated reactor V12 valve bypass thyristor opening process can be exerted on the basis of not interrupting the bypass pair current.

Description

Technical Field

[0001] This invention relates to the field of DC transmission system technology, specifically to a method and system for activating a bypass pair in a controllable commutated converter. Background Technology

[0002] Traditional line-commutated converter high-voltage direct current (LCC-HVDC) transmission systems offer advantages such as long-distance, high-capacity power transmission and controllable active power, leading to their widespread application worldwide. However, because the thyristors used in their converters rely on the AC system for commutation voltage, commutation failures are prone to occur under AC system faults, resulting in a surge in DC current and a rapid and significant loss of DC transmission power. Furthermore, in recent years, some regional power grids in my country have incorporated multiple DC feeds. If a commutation failure occurs on one DC line, it can lead to a cascading failure of multiple DC lines via AC system coupling, posing a more severe challenge to the safe and stable operation of the power grid.

[0003] To address the commutation failure problem in LCC-HVDC systems, a controllable commutation converter combining the advantages of both LCC and VSC converters has been proposed, with the following topology: Figure 1 As shown, each 6-pulse converter bridge consists of a main branch and an auxiliary branch connected in parallel. The main branch is formed by the main branch thyristor valve V. 11 and low-pressure IGBT valve V 12 The auxiliary branch is composed of a high-voltage, low-current IGBT valve V. 13 and high-voltage low-current thyristor valve V 14 It is connected in series.

[0004] When a DC power line needs to be shut down urgently, a bypass pair is usually activated first. This involves selecting two converter valves on the same AC phase as the bypass pair. For traditional LCC converter valves, each valve consists only of thyristors connected in series. Triggering a thyristor valve only requires applying a trigger pulse to the thyristor gate when the valve is subjected to a positive voltage. After the thyristor turns on, removing the trigger pulse allows it to continue conducting. Therefore, activating a bypass pair for traditional LCC converter valves only requires triggering the two converter valves connected on the same AC phase. However, for controllable phase-commutated converter valves, the main branch thyristor valve V... 11 and low-pressure IGBT valve V 12In this configuration, the IGBT valve's conduction requires a continuous voltage applied between the gate and emitter of the IGBT's high-potential board. This consumes the energy stored in the high-potential board. The high-potential board, however, draws energy from the voltage applied across the IGBT after it is turned off. Once a bypass pair is formed, the IGBT will continue to conduct, and the high-potential board cannot replenish its energy storage. Once the energy storage is depleted, the IGBT will no longer be able to trigger conduction, and the bypass pair will cease to function. To address this issue, in V... 12 A bypass thyristor is connected in parallel across the valve. When a bypass pair is needed, the bypass thyristor is turned on. However, when V... 11 Valve and V 12 When the valve IGBT is turned on, the saturated reactor in the main branch is in a saturated state. If V is directly triggered... 12 When a bypass thyristor is used, the saturated reactor cannot limit the rate of current rise of the bypass thyristor, leading to damage to the bypass thyristor. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art that after the energy storage is exhausted after the bypass pair of the controllable commutation converter is put into operation, the IGBT will not be able to be triggered to conduct and the bypass pair will also be unable to work, thereby providing a method and system for putting into operation the bypass pair of the controllable commutation converter.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, embodiments of the present invention provide a method for activating a bypass pair in a controllable commutated converter. The controllable commutated converter includes a converter valve in which each converter valve is composed of a main branch and an auxiliary branch connected in parallel. The converter valves on the same bridge arm constitute a bypass pair. The method includes: when a bypass pair activation signal is received, determining the converter valve that is last to be activated and the bypass pair to be activated based on a trigger signal sent by a valve control system; controlling the operating state of the converter valve that is last to be activated, first diverting its main branch current to the auxiliary branch, and then diverting the auxiliary branch current to the main branch after the main branch current crosses zero; and controlling the main branch of the paired valve of the bypass pair to be activated to be activated to be activated.

[0008] In one embodiment, the process of determining the sequence number of the latest activated converter valve and the sequence number of the bypass pair based on the trigger signal sent by the valve control system includes: comparing the trigger signals of the converter valves sent by the valve control system pairwise to determine the latest activated converter valve; and taking the converter valve of the AC phase in which the latest activated converter valve is located as the bypass pair.

[0009] In one embodiment, the main branch is composed of a main branch thyristor valve and a low-voltage IGBT valve connected in series, and the low-voltage IGBT is connected in parallel to the bypass thyristor; the auxiliary branch is composed of a high-voltage IGBT valve and a high-voltage thyristor valve connected in series.

[0010] In one embodiment, by controlling the operating state of the converter valve that is turned on last, the main branch current is first directed to the auxiliary branch. After the main branch current crosses zero, the auxiliary branch current is then directed to the main branch. This includes: controlling the high-voltage IGBT valve and the high-voltage thyristor valve of the converter valve that is turned on last; and controlling the main branch thyristor valve of the converter valve that is turned on last and the bypass thyristor of the low-voltage IGBT to turn on after the main branch current crosses zero.

[0011] In one embodiment, controlling the main branch conduction of the dual valve of the bypass pair to be engaged includes: controlling the conduction of the main branch thyristor valve of the dual valve and the bypass thyristor of the low-voltage IGBT.

[0012] In one embodiment, the method for engaging the bypass pair of a controllable commutator further includes: shutting off the converter valves not selected as bypass pairs using a natural shut-off method.

[0013] Secondly, embodiments of the present invention provide a bypass pair activation system for a controllable commutator converter. The controllable commutator converter includes a converter valve, each of which is composed of a main branch and an auxiliary branch connected in parallel. The converter valves on the same bridge arm form a bypass pair. The system includes: a determination module, used to determine the converter valve that is turned on last and the bypass pair to be activated based on a trigger signal sent by the valve control system when a bypass pair activation signal is received; an activation module, used to control the operating state of the converter valve that is turned on last, first diverting its main branch current to the auxiliary branch, and then diverting the auxiliary branch current to the main branch after the main branch current crosses zero; and controlling the main branch of the paired valve of the bypass pair to be activated to be turned on.

[0014] In one embodiment, the controllable commutator bypass pair activation system further includes a shutdown module for shutting off the converter valves not selected as bypass pairs using a natural shutdown method.

[0015] Thirdly, embodiments of the present invention provide a computer device, including: at least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the controllable commutator bypass pair activation method of the first aspect of the present invention.

[0016] Fourthly, embodiments of the present invention provide a computer-readable storage medium storing computer instructions for causing a computer to execute the controllable commutator bypass pair activation method of the first aspect of the present invention.

[0017] The technical solution of this invention has the following advantages:

[0018] The controllable commutator bypass pair activation method and system provided by this invention, when a bypass pair activation signal is received, determines the latest activated converter valve and the bypass pair to be activated based on the trigger signal sent by the valve control system. This ensures that the bypass pair is formed as quickly as possible, and the control strategy is compatible with the existing DC engineering bypass pair activation strategy. By controlling the operating state of the latest activated converter valve, its main branch current is first diverted to the auxiliary branch. After the main branch current crosses zero, the auxiliary branch current is diverted to the main branch. The main branch of the paired valve of the bypass pair to be activated is controlled to be activated, thereby enabling the protection function of the bypass thyristor opening process of the main branch saturated reactor V12 valve without interrupting the bypass pair current. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a topology diagram of a controllable commutator provided in an embodiment of the present invention;

[0021] Figure 2 The converter natural commutation operating state valve voltage and current waveforms provided in this embodiment of the invention;

[0022] Figure 3 A flowchart illustrating a specific example of the input method provided in an embodiment of the present invention;

[0023] Figure 4 A flowchart of bypass pair selection provided in an embodiment of the present invention;

[0024] Figure 5 A flowchart illustrating another specific example of the input method provided in this embodiment of the invention;

[0025] Figure 6 , Figures 7(a) to 7(d) , Figure 8 These are circuit diagrams of the bypass pair process provided in the embodiments of the present invention;

[0026] Figure 9 This is a composition diagram of a specific example of a computer device provided in an embodiment of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Example 1

[0032] This invention provides a method for activating the bypass pair of a controllable commutator converter, such as... Figure 1 As shown, the controllable commutator includes a converter valve in which each converter valve is composed of a main branch and an auxiliary branch connected in parallel. The converter valves on the same bridge arm form a bypass pair. The main branch is a main branch thyristor valve V. 11 and low-pressure IGBT valve V 12 The system consists of a series connection, with low-voltage IGBTs connected in parallel to bypass thyristors; the auxiliary branch is a high-voltage IGBT valve V. 13 and high-voltage thyristor valve V 14 It is connected in series. The voltage and current waveforms of each converter valve (V1, V3, V5 / V2, V4, V6) in the converter are as follows: Figure 2 As shown, valves whose numbers are both odd or both even are naturally commutated (e.g., V1 and V3 commutate, V3 and V5 commutate, and so on).

[0033] based on Figure 1 The topology shown illustrates the working principle of this controllable commutator converter: the main branch is periodically turned on, allowing direct current to flow; when the main branch has been turned on for 120°, current flows through the low-voltage IGBT valve V. 12 V, the main branch thyristor valve 11 The current is transferred to the controllably turn-off auxiliary branch. After the main thyristor valve recovers its turn-off capability (500μs), the forward blocking capability of that bridge arm is restored using the turn-off current characteristics of the high-voltage IGBT valve, successfully completing the inter-bridge arm commutation. The above switching logic is as follows: Figure 2 As shown, the bridge arm current can be controlled in both steady state and AC fault conditions, 100% solving the commutation failure problem.

[0034] like Figure 3 As shown, the bypass connection method for a controllable commutator includes:

[0035] Step S11: When a bypass pair activation signal is received, determine the latest activated converter valve and the bypass pair to be activated based on the trigger signal sent by the valve control system.

[0036] Specifically, in this embodiment of the invention, the trigger signals of the converter valves sent by the valve control system are compared pairwise to determine the converter valve that is triggered last; the converter valves of the AC phase in which the converter valve that is triggered last are taken as the bypass pair.

[0037] For example, with Figure 1 Taking the 6-pulse controllable commutator shown as an example, each commutator valve is labeled. Using the labels in the diagram as an example, the process for determining the last commutator valve to be activated and the bypass pair to be put into operation is as follows: Figure 4 As shown. In this example, the converter valves on the same bridge arm form a bypass pair and are paired valves.

[0038] Step S12: By controlling the operating state of the converter valve that is turned on last, first guide its main branch current into the auxiliary branch, and after the main branch current crosses zero, guide the auxiliary branch current into the main branch; control the main branch of the dual valve of the bypass pair to be put into operation to turn on.

[0039] Specifically, in this embodiment of the invention, the main branch current is introduced into the auxiliary current, so that... Figure 1 The main branch thyristor valve V 11 After the high-potential board is charged, the auxiliary branch current is introduced into the main branch only after the main branch current crosses zero. This avoids the direct conduction of the thyristor valve V in the main branch. 11 This results in the high-potential board being unable to replenish energy storage. Once the energy storage is depleted, the IGBT will be unable to trigger conduction, and the bypass pair will also fail to work.

[0040] Optionally, such as Figure 5As shown, step S12 is executed from steps S21 to S22, specifically as follows:

[0041] Step S21: Control the conduction of the high-pressure IGBT valve and the high-pressure thyristor valve of the converter valve that is turned on last.

[0042] Specifically, when engaging the bypass pair, the main branch circuit needs to be connected to the auxiliary branch first. At this time, the thyristor valve V in the main branch... 11 and low-pressure IGBT valve V 12 All shut-off, high-pressure IGBT valve V 13 and high-voltage thyristor valve V 14 When the circuit is turned on, the current flows from the autonomous branch into the auxiliary branch.

[0043] For example, if the last converter valve to be turned on is V1, then the bypass pair to be put into operation is V1 and V4, such as... Figure 6 As shown. Before the bypass is engaged, the main branch thyristor valve V1 is used as the commutator valve. 11 and low-pressure IGBT valve V 12 All circuits are now open, as shown in Figure 7(a). When engaging the bypass pair, the main branch thyristor valve V... 11 and low-pressure IGBT valve V 12 All shut-off, high-pressure IGBT valve V 13 and high-voltage thyristor valve V 14 When the circuit is turned on, the current flows from the autonomous branch into the auxiliary branch, as shown in Figure 7(b).

[0044] Step S22: After the main branch current crosses zero, the main branch thyristor valve that controls the last converter valve to turn on and the bypass thyristor of the low-voltage IGBT are turned on.

[0045] Specifically, after the main branch current crosses zero, the main branch thyristor valve V... 11 and low-pressure IGBT valve V 12 The bypass thyristors are all conducting, and the high-voltage IGBT valve V is also conducting. 13 and high-voltage thyristor valve V 14 All are shut off, thus avoiding direct triggering of the low-pressure IGBT valve V. 12 The bypass thyristor is damaged because the saturated reactor cannot limit the rate of rise of the bypass thyristor current.

[0046] For example, if the last converter valve to be turned on is V1, then the bypass pair to be put into operation is V1 and V4, such as... Figure 6 As shown. After the main branch current crosses zero, the main branch thyristor valve V... 11 and low-pressure IGBT valve V 12 The bypass thyristors are all conducting, and the high-voltage IGBT valve V is also conducting. 13 and high-voltage thyristor valve V 14All circuits are turned off, and the auxiliary current is introduced into the main branch, as shown in Figure 7(c).

[0047] In one specific embodiment, controlling the main branch conduction of the dual valve of the bypass pair to be put into operation includes: controlling the conduction of the main branch thyristor valve of the dual valve and the bypass thyristor of the low-voltage IGBT.

[0048] For example, if the last converter valve to be turned on is V1, then the bypass pair to be put into operation is V1 and V4, such as... Figure 6 As shown. The control method of the converter valve V1 is as described in steps S21 to S22. Then the main branch thyristor valve of V4 and the bypass thyristor of the low voltage IGBT are turned on, thereby realizing the activation of the bypass pair, as shown in 7(d).

[0049] In one specific embodiment, the method for engaging the bypass pair of a controllable commutator further includes: shutting off the converter valves not selected as bypass pairs using a natural shut-off method.

[0050] For example, if the last converter valve to be turned on is V1, then the bypass pair to be put into operation is V1 and V4, such as... Figure 6 As shown. The V6 valve, not selected as a bypass pair, uses a natural shut-off method, such as... Figure 8 As shown, after the bypass valve is turned on, the V6 valve will quickly shut off under the action of the bypass current.

[0051] Example 2

[0052] This invention provides a bypass pair activation system for a controllable commutated converter. The controllable commutated converter includes a converter valve, each of which is composed of a main branch and an auxiliary branch connected in parallel. The converter valves on the same bridge arm form a bypass pair. The system includes:

[0053] The determination module is used to determine the latest activated converter valve and the bypass pair to be activated based on the trigger signal sent by the valve control system when a bypass pair activation signal is received. This module executes the method described in step S11 of embodiment 1, which will not be repeated here.

[0054] The input module is used to control the operating state of the last converter valve to be turned on, first directing its main branch current to the auxiliary branch, and then directing the auxiliary branch current to the main branch after the main branch current crosses zero; and control the main branch of the dual valve of the bypass pair to be turned on to be turned on; this module performs the method described in step S12 of embodiment 1, which will not be repeated here.

[0055] In one specific embodiment, the controllable commutator bypass to the system further includes:

[0056] The shutdown module is used to shut off the converter valves that are not selected as bypass pairs using a natural shutdown method; this module performs the method described in step S1 of embodiment 1, which will not be repeated here.

[0057] Example 3

[0058] This invention provides a computer device, such as... Figure 9 As shown, the system includes: at least one processor 401, such as a CPU (Central Processing Unit), at least one communication interface 403, a memory 404, and at least one communication bus 402. The communication bus 402 is used to enable communication between these components. The communication interface 403 may include a display screen or a keyboard; optionally, the communication interface 403 may also include a standard wired interface or a wireless interface. The memory 404 may be high-speed RAM (Random Access Memory) or non-volatile memory, such as at least one disk drive. Optionally, the memory 404 may also be at least one storage device located remotely from the processor 401. The processor 401 can execute the controlled commutator bypass pair activation method of Embodiment 1. The memory 404 stores a set of program code, and the processor 401 calls the program code stored in the memory 404 to execute the controlled commutator bypass pair activation method of Embodiment 1.

[0059] The communication bus 402 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The communication bus 402 can be divided into an address bus, a data bus, and a control bus, etc. For ease of representation, Figure 9 The symbol is represented by only one line, but this does not mean that there is only one bus or one type of bus.

[0060] The memory 404 may include volatile memory, such as random-access memory (RAM); the memory may also include non-volatile memory, such as flash memory, hard disk drive (HDD) or solid-state drive (SSD); the memory 404 may also include a combination of the above types of memory.

[0061] The processor 401 can be a central processing unit (CPU), a network processor (NP), or a combination of CPU and NP.

[0062] The processor 401 may further include a hardware chip. This hardware chip may be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), or a combination thereof. The PLD may be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof.

[0063] Optionally, the memory 404 is also used to store program instructions. The processor 401 can call the program instructions to implement the controllable commutator bypass pair activation method as described in Embodiment 1 of this application.

[0064] This invention also provides a computer-readable storage medium storing computer-executable instructions that can execute the controllable commutator bypass pair activation method of Embodiment 1. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), random access memory (HDD), or solid-state drive (SSD), etc.; the storage medium may also include combinations of the above types of memory.

[0065] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for activating a bypass pair in a controllable commutator converter, characterized in that, The controllable commutator includes multiple converter valves, each of which is composed of a main branch and an auxiliary branch connected in parallel. The converter valves on the same bridge arm form a bypass pair. The method includes: When a bypass pair activation signal is received, the latest activated converter valve and the bypass pair to be activated are determined based on the trigger signal sent by the valve control system. By controlling the operating state of the converter valve that is turned on last, its main branch current is first directed to the auxiliary branch. After the main branch current crosses zero, the auxiliary branch current is directed to the main branch. The main branch of the valve to be put into the bypass pair is turned on. The main branch is composed of a main branch thyristor valve and a low-voltage IGBT valve connected in series, and the low-voltage IGBT is connected in parallel to the bypass thyristor; the auxiliary branch is composed of a high-voltage IGBT valve and a high-voltage thyristor valve connected in series.

2. The method for activating the bypass pair of a controllable commutator converter according to claim 1, characterized in that, The process of determining the sequence number of the latest activated converter valve and the bypass pair based on the trigger signal sent by the valve control system includes: The trigger signals of the converter valves sent by the valve control system are compared pairwise to determine the converter valve that was triggered last. The converter valve of the AC phase that is triggered last is designated as the bypass pair.

3. The method for activating the bypass pair of a controllable commutator converter according to claim 2, characterized in that, By controlling the operating state of the converter valve that is turned on last, its main branch current is first diverted to the auxiliary branch. After the main branch current crosses zero, the auxiliary branch current is then diverted to the main branch. This includes: The high-voltage IGBT valve and high-voltage thyristor valve that control the latest-to-be-activated converter valve are turned on. After the main branch current crosses zero, the main branch thyristor valve that controls the last converter valve to turn on and the bypass thyristor of the low-voltage IGBT are turned on.

4. The method for activating the bypass pair of a controllable commutator converter according to claim 2, characterized in that, Controlling the main branch conduction of the dual valve of the bypass pair to be put into operation includes: The main branch thyristor valve of the control coupler valve and the bypass thyristor of the low-voltage IGBT are turned on.

5. The method for activating the bypass pair of a controllable commutator converter according to claim 1, characterized in that, Also includes: The converter valve that is not selected as a bypass pair is shut off using the natural shut-off method.

6. A controllable commutator bypass pair activation system, characterized in that, The controllable phase-commutation converter includes a converter valve consisting of a main branch and an auxiliary branch connected in parallel, with converter valves on the same bridge arm forming a bypass pair. The system includes: The determination module is used to determine the latest activated converter valve and the bypass pair to be activated based on the trigger signal sent by the valve control system when a bypass pair activation signal is received. The input module is used to control the operating status of the last converter valve to be turned on, first directing its main branch current to the auxiliary branch, and then directing the auxiliary branch current to the main branch after the main branch current crosses zero; and to control the main branch conduction of the dual valve of the bypass pair to be put into operation. The main branch is composed of a main branch thyristor valve and a low-voltage IGBT valve connected in series, and the low-voltage IGBT is connected in parallel to the bypass thyristor; the auxiliary branch is composed of a high-voltage IGBT valve and a high-voltage thyristor valve connected in series.

7. The controllable commutator bypass system according to claim 6, characterized in that, Also includes: The shutdown module is used to shut off the converter valves that are not selected as bypass pairs using a natural shutdown method.

8. A computer device, characterized in that, include: At least one processor, and a memory communicatively connected to the at least one processor, wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to cause the at least one processor to perform the controllable commutator bypass pair activation method according to any one of claims 1-5.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing the computer to perform the controllable commutator bypass pair activation method according to any one of claims 1-5.

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