A method, system, terminal and storage medium for inhibiting direct current line permanent ground fault loop isolation

Abstract

The application discloses a kind of inhibiting permanent ground fault loop current isolation method and system of direct current line, comprising: according to the permanent ground fault of detected direct current line, if interstation communication is normal and meet restart condition, then execute rectification side fault clearing mode, low voltage monitoring control protection lockout after cutting off rectification side neutral bus switch NBS1 and inverter side neutral bus switch NBS2;If interstation communication is normal and do not meet restart condition, for the lockout of bypass mode, inverter side executes phase shift to 90 after lockout, and cut off inverter side neutral bus switch NBS2;For the lockout of not bypass mode, inverter side delay lockout and do not execute phase shift 90 °;If interstation communication is abnormal, then execute inverter side fault clearing mode, low voltage monitoring control protection lockout inverter side high-end converter valve H3 and low-end converter valve H4, and cut off inverter side neutral bus switch NBS2.The application is conducive to eliminating direct current system abnormal operation mode, and is convenient for fault maintenance.

Description

Technical Field

[0001] This invention relates to the field of control and protection technology for ultra-high voltage direct current transmission systems, and in particular to a method, system, terminal, and storage medium for isolating circulating currents during permanent grounding faults in DC lines. Background Technology

[0002] Ultra-high voltage direct current (UHVDC) transmission systems have various operating modes, among which the double-polar grounding return mode is the most common. However, when a permanent grounding fault occurs on one pole of the DC line, an abnormal circulating current can easily form between the fault grounding point and the grounding electrode lead of the DC transmission system. This circulating current poses a significant hidden danger for the maintenance of the fault pole and affects the safe and stable operation of the DC system.

[0003] Among them, DC line faults are more likely to form abnormal circulating currents than other fault types due to factors such as clearing strategies, inter-station communication, and protection configuration. The unique aspect of DC line fault circulating current isolation lies in the fact that the main protection traveling wave protection of DC lines is generally configured on the rectifier side, while the inverter side mainly relies on voltage surge protection. However, the inverter side voltage surge protection is affected by factors such as transition resistance, line parameters, and operating mode. If the fault point is close to the rectifier side outlet, the inverter side surge protection may fail to operate. Since the line fault grounding point is located outside the rectifier side line outgoing line, single-end isolation on the rectifier side alone cannot isolate the circulating current. When an abnormal circulating current forms, the current response mainly relies on manual intervention. Operators monitor the screen and, upon discovering the anomaly, promptly separate the neutral bus circuit breaker (NBS) corresponding to the faulty pole to isolate the faulty pole from the non-faulty pole. This approach has a low degree of automation and is not conducive to fault repair. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method, system, terminal and storage medium for isolating circulating currents in DC lines under permanent grounding faults, which can eliminate abnormal circulating currents formed by permanent grounding faults in DC lines under different operating conditions.

[0005] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides a method for isolating circulating currents in a permanent ground fault in a DC line, the method comprising:

[0007] After a permanent grounding fault occurs on a DC line, the inter-station communication status is determined based on the operating status of the DC system.

[0008] If the inter-station communication is normal and the high-end converter valve group meets the restart conditions, the rectifier side fault clearing mode is executed. After the low voltage monitoring and control protection is locked, the rectifier side neutral bus switch NBS1 and the inverter side neutral bus switch NBS2 are disconnected.

[0009] If the inter-station communication is normal and the high-end converter valve group does not meet the restart conditions, and the blocking setting for the inverter side is the bypass mode, then after the inverter side phase shifts to 90°, the inverter side bypass switch BPS3 and bypass switch BPS4 are closed, blocking the trigger pulses of the high-end converter valve H3 and the low-end converter valve H4, and disconnecting the inverter side neutral bus switch NBS2; if the blocking setting for the inverter side is not the bypass mode, then the bypass switch BPS3 and bypass switch BPS4 are kept in the open state, the inverter side delays the blocking and does not perform the 90° phase shift;

[0010] If the inter-station communication is abnormal, the inverter-side fault clearing mode is executed, the low voltage monitoring and control protection blocks the inverter-side high-end converter valve H3 and low-end converter valve H4, and disconnects the inverter-side neutral bus switch NBS2.

[0011] In conjunction with the first aspect, preferably, the method further includes: after the rectifier side has completed the set number of restarts, if the DC voltage is not established, the DC line restart is unsuccessful, and the high-end converter valve H1 and the low-end converter valve H2 on the rectifier side are directly locked.

[0012] In conjunction with the first aspect, preferably, the number of restarts includes two full-pressure restarts and one reduced-pressure restart, or only one full-pressure restart.

[0013] In conjunction with the first aspect, preferably, the restart condition of the high-end converter valve group refers to the simultaneous fulfillment of the requirements for traveling wave protection operation by the operating conditions of ground mode wave, polar line wave, voltage, and current.

[0014] In conjunction with the first aspect, preferably, the step of performing the rectifier-side fault clearing method includes:

[0015] If the DC line restarted on the rectifier side fails, the high-end converter valve H1 and low-end converter valve H2 on the rectifier side will be locked, and the high-end converter valve H1 will be restarted.

[0016] After receiving the signal from the rectifier side to lock the high-end converter valve H1 and the low-end converter valve H2, the inverter side locks the high-end converter valve H3 and the low-end converter valve H4.

[0017] If the high-side converter valve H1 fails to restart on the rectifier side, the high-side converter valve H1 will be locked by the low voltage monitoring and control protection on the rectifier side, and the neutral bus switch NBS1 on the rectifier side will be disconnected.

[0018] After receiving the low voltage monitoring and control protection lockout signal from the rectifier side, the inverter side locks out the high-end converter valve H3 and disconnects the neutral bus switch NBS2 on the reverse side.

[0019] In conjunction with the first aspect, preferably, the step of executing the inverter-side fault clearing method includes:

[0020] If the DC line restarted on the rectifier side fails, the high-end converter valve H1 and the low-end converter valve H2 on the rectifier side will be locked.

[0021] After receiving the signal from the rectifier side to lock the high-end converter valve H1 and the low-end converter valve H2, the inverter side shifts the phase to 90°.

[0022] After the inverter side phase shifts to 90°, the inverter side bypass switches BPS3 and BPS4 are closed. The low voltage monitoring and control protection locks out the inverter side high-end converter valve H3 and low-end converter valve H4, and disconnects the inverter side neutral bus switch NBS2.

[0023] In conjunction with the first aspect, preferably, the low voltage monitoring and control protection is a low voltage protection action or a low voltage monitoring action.

[0024] Secondly, the present invention provides a method system for isolating circulating currents during permanent grounding faults in DC lines, the system comprising:

[0025] The communication status judgment module is used to determine whether the inter-station communication is normal based on the detection of a permanent grounding fault in the DC line.

[0026] The first circulating current isolation module is used to execute the rectifier side fault clearing mode and disconnect the rectifier side neutral bus switch NBS1 and the inverter side neutral bus switch NBS2 after the low voltage monitoring and control protection is locked out when the inter-station communication is normal and the high-end converter valve group meets the restart conditions.

[0027] The second circulating isolation module is used to, if the inter-station communication is normal and the high-end converter valve group does not meet the restart conditions, lock the high-end converter valve H3 and the low-end converter valve H4 when the blocking mode set for the inverter side is bypass mode. Then, after the phase shift to 90°, the inverter side bypass switch BPS3 and bypass switch BPS4 are closed, and the inverter side neutral bus switch NBS2 is disconnected. If the blocking mode set for the inverter side is not bypass mode, the bypass switch BPS3 and bypass switch BPS4 are kept in the open state, the inverter side is delayed in blocking and does not perform phase shift of 90°.

[0028] The third circulating current isolation module is used to execute the inverter side fault clearing mode if the inter-station communication is abnormal, and to block the inverter side high-end converter valve H3 and low-end converter valve H4, and disconnect the inverter side neutral bus switch NBS2.

[0029] Thirdly, the present invention provides a terminal, including a processor and a storage medium;

[0030] The storage medium is used to store instructions;

[0031] The processor is configured to operate according to the instructions to perform the steps of the method for isolating circulating currents in a DC line permanent ground fault as described in any of the first aspects.

[0032] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method for isolating circulating currents in a permanent ground fault of a DC line as described in any of the first aspects.

[0033] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0034] This invention analyzes the causes of abnormal circulating currents under different operating conditions and optimizes the process by employing strategies such as different pole isolation strategies, a 90° phase shift and re-blocking strategy, and inverter-side bypass operation to eliminate abnormal circulating currents formed by the inherent grounding point of the DC system and the fault grounding point of the line. This helps to eliminate abnormal operating modes of the DC system, reduce DC power loss, facilitate fault repair of the faulty pole DC line, and improve the safety and reliability of operation. The method of this invention is applicable to UHVDC transmission systems and also has reference value for circulating current suppression in conventional DC systems. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating a method for isolating circulating currents in a permanent grounding fault of a DC line, provided by an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the main circuit structure of a dual twelve-pulse ultra-high voltage direct current main wiring system provided in an embodiment of the present invention;

[0037] Figure 3 This is a timing diagram of circulating current isolation control for high-end converter valve group with communication DC line fault restart provided in an embodiment of the present invention;

[0038] Figure 4 (a) and (b) are timing diagrams of the circulating current isolation control provided in the embodiments of the present invention, which includes blocking in bypass mode when a communication DC line fault occurs and blocking in non-bypass mode.

[0039] Figure 5 This is a timing diagram for direct blocking circulating current isolation control for DC line faults without communication provided in an embodiment of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments and specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations thereof. In the absence of conflict, the embodiments and technical features in the embodiments can be combined with each other.

[0041] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0042] Example 1:

[0043] Reference Figure 1 As shown in the figure, this embodiment introduces a method for isolating circulating currents to suppress permanent grounding faults in DC lines, applicable to... Figure 2 The diagram shows a dual-twelve-pulse UHVDC main wiring system; the dual-twelve-pulse UHVDC system mainly includes: rectifier-side high-end converter valve H1, rectifier-side low-end converter valve H2, rectifier-side bypass switch BPS1, rectifier-side bypass switch BPS2, rectifier-side neutral bus switch NBS1; inverter-side high-end converter valve H3, inverter-side low-end converter valve H4, inverter-side bypass switch BPS3, inverter-side bypass switch BPS4, inverter-side neutral bus switch NBS2, and DC lines, I d1 and I d2 Indicates the direction of the line current; the method specifically includes the following steps:

[0044] First, after the control and protection system detects a permanent ground fault on a DC line, it determines whether inter-station communication is normal; and then adopts three different circulating current isolation methods for the following three different situations:

[0045] Circulating current isolation method 1: If the inter-station communication is normal and the high-end converter valve group meets the restart conditions, the rectifier side fault clearing method is executed. After the low voltage monitoring and control protection is locked, the rectifier side neutral bus switch NBS1 and the inverter side neutral bus switch NBS2 are disconnected.

[0046] Specifically, after the inter-station communication is detected to be normal, it should be determined whether the current operating conditions meet the conditions for restarting the high-end valve group (i.e., the high-end converter valve H1 on the rectifier side and the high-end converter valve H3 on the inverter side). If the conditions are met, the low-end converter valve H2 on the rectifier side and the low-end converter valve H4 on the inverter side remain in the locked state, while the converter valve H1 on the rectifier side and the converter valve H3 on the inverter side are restarted. Since the ground fault is a permanent fault, the rectifier side low voltage protection or low voltage monitoring lockout will activate and lock the high-end converter valve H1. After receiving the rectifier side lockout signal through inter-station communication, the inverter side will lock its own high-end converter valve H3. After the rectifier side low voltage protection or low voltage monitoring lockout is activated, it will issue a command to cut off the neutral bus switch NBS1 on its own side. After receiving the rectifier side lockout command, the inverter side will issue a command to cut off the neutral bus switch NBS2 on its own side.

[0047] Circulating isolation method two: If the inter-station communication is normal and the high-end converter valve group does not meet the restart conditions, and the blocking setting for the inverter side is the bypass mode, then after the inverter side phase shifts to 90°, the bypass switches BPS3 and BPS4 are closed, and then the high-end converter valve H3 and the low-end converter valve H4 are blocked, and the inverter side neutral bus switch NBS2 is disconnected; if the blocking setting for the inverter side is not the bypass mode, then the bypass switches BPS3 and BPS4 are kept in the open state, the inverter side is delayed in blocking and does not perform a 90° phase shift;

[0048] Specifically, when communication between testing stations is normal, but the conditions for restarting the high-end valve group are not met, the rectifier-side control and protection system issues a command to lock the rectifier-side high-end converter valve H1, low-end converter valve H2, and inverter-side high-end converter valve H3 and low-end converter valve H4. Since the bypass switches BPS1 and BPS2 will not be closed after the rectifier-side fault lockout, the DC system grounding point and the fault grounding point will not form an abnormal circulating current through the rectifier-side bypass branch. At this time, it is necessary to determine whether the inverter-side bypass switches BPS3 and BPS4 are closed after the fault. If the inverter-side bypass switches BPS3 and BPS4 are closed after the fault, to prevent the DC line grounding point and the rectifier-side grounding point from forming an abnormal circulating current through the inverter-side bypass branch... In case of a normal circulating current, the inverter side issues a command to disconnect the neutral bus switch NBS2. It should be noted that if the inverter side bypass switches BPS3 and BPS4 are disconnected after a fault, the commonly used method is to release the DC line energy by phase shifting and delaying the blocking. However, due to the discharge of the circuit resistance by the distributed capacitance of the line, the DC system grounding point and the line fault grounding point will form an abnormal circulating current through the converter valve, causing the high-end converter valve H3 and the low-end converter valve H4 on the inverter side to fail to close. Therefore, if the inverter side bypass switches BPS3 and BPS4 are in the open state after a fault, this embodiment of the invention suppresses the generation of abnormal circulating current by delaying the blocking on the inverter side and not performing the 90° phase shifting operation.

[0049] Circulating current isolation method three: If the inter-station communication is abnormal, the inverter side fault clearing method is executed, the low voltage monitoring and control protection blocks the inverter side high-end converter valve H3 and low-end converter valve H4, and disconnects the inverter side neutral bus switch NBS2.

[0050] Specifically, when communication between monitoring stations is abnormal, the rectifier-side line protection will lock the high-end converter valve H1 and low-end converter valve H2 on the rectifier side after activation. Since the bypass switches BPS1 and BPS2 will not be closed after the rectifier-side fault lockout, the DC system grounding point and the fault grounding point will not form an abnormal circulating current through the rectifier-side bypass branch. However, due to the loss of inter-station communication, the inverter side cannot obtain the rectifier-side lockout command. At this time, the inverter side will lock the high-end converter valve H3 and low-end converter valve H4 on its own side through low-voltage control monitoring. Since the inverter-side bypass switches BPS3 and BPS4 will be closed after the low-voltage control monitoring lockout, in order to prevent the DC system grounding point and the DC line grounding point on the rectifier side from forming a circulating current through the inverter-side bypass branch, the inverter-side low-voltage control monitoring will issue a command to cut off the neutral bus switch NBS2 on its own side after the lockout.

[0051] The following section will provide a detailed introduction to the three circulation isolation methods mentioned above, using practical applications as examples.

[0052] Reference Figure 3 The image shows an embodiment of the circulating current isolation control for restarting the high-end valve group during a communication DC line fault, provided by the present invention.

[0053] After a DC permanent ground fault occurs, the traveling wave protection on the rectifier side operates at time t0 and sends a phase-shifting restart signal. Since the traveling wave protection contains four criteria: ground mode wave, pole wave, voltage, and current, the line protection will send a phase-shifting restart command only when all four criteria are met. Therefore, in this embodiment, t0 is 10 to 30 ms.

[0054] If the DC voltage still fails to be established after the rectifier side has performed the prescribed number of restarts, it is determined that the DC line restart has failed. At time t1, the high-end converter valve H1 and the low-end converter valve H2 are locked, and the high-end converter valve H1 is restarted sequentially (i.e., Reboot sequential control is performed). The DC line restart is divided into original voltage restart and reduced voltage restart. Since different projects use different numbers of restarts, some projects only contain one original voltage restart, while some projects contain not only two original voltage restarts but also one reduced voltage restart. Therefore, t1 is set to 260~1200ms.

[0055] After receiving signals from the high-end converter valve H1 and the low-end converter valve H2 on the rectifier side, the inverter side locks the high-end converter valve H3 and the low-end converter valve H4 at time t2. The delay between the inverter side and the rectifier side in issuing the lockout of the converter valves should only include the inter-station communication delay. t2 is set to 280ms~1220ms.

[0056] The high-end converter valves H1 and H3 on the rectifier and inverter sides are restarted at time t3. The restart time is related to the operation time of the primary equipment disconnector, especially the pole isolation and pole connection time, and is also related to the control and protection execution cycle. Therefore, t3 is set to 60280ms~181220ms.

[0057] The rectifier-side DC low voltage protection or low voltage monitoring operates at time t4, locking the high-end converter valve H1 and issuing a request for polarity isolation signal, and disconnecting the rectifier-side neutral bus switch NBS1. The low voltage monitoring or low voltage protection operation time is generally between 2300 and 3000 ms, so t4 should be set to 62580 ms to 184220 ms.

[0058] After receiving the blocking and request pole isolation signals from the rectifier side, the inverter side blocks the high-end converter valve H3 on its own side at time t5 and sends a request pole isolation signal, disconnecting the neutral bus switch NBS2 on the inverter side. When inter-station communication is normal, the delay of the inverter side blocking the high-end valve group compared to the rectifier side should be the inter-station communication delay. The inter-station communication delay is generally 20ms, so t5 is set to 62600ms~184240ms.

[0059] Reference Figure 4 As shown in (a) and (b), these are embodiments of the circulating current isolation control provided by the present invention, which includes a bypass mode blocking when there is a communication DC line fault and a non-bypass mode blocking.

[0060] After a permanent DC ground fault occurs, the traveling wave protection on the rectifier side activates at time t0 and sends a phase-shifting restart signal, t0 being set to 10–30 ms. If the DC voltage still fails to establish after the rectifier side performs the prescribed number of restarts, it is determined that the DC line restart has failed. At time t1, the high-side converter valve H1 and the low-side converter valve H2 are locked, and the high-side converter valve H1 restart sequence control is initiated, t1 being set to 260–1200 ms. After receiving the lockout command from the rectifier side, the inverter side performs a phase shift to 90° release at time t2. For DC line energy discharge operations, the inter-station communication delay is generally 20ms, so t2 should be set to 280ms~1220ms; after the inverter side phase shifts to 90°, it executes the command to block the high-end converter valve H3 and the low-end converter valve H4; at time t3, it enters bypass mode and issues the command to cut off the neutral bus switch NBS2 on this side. The inverter side generally needs 200ms to perform the 90° phase shift operation, and it generally needs 30ms to close the bypass switch, so t3 is set to 510ms~1450ms.

[0061] If the inverter side fails and chooses not to enter bypass mode, there is no significant difference in the timing of the rectifier side. The inverter side should perform a 90° phase shift operation. After receiving the rectifier side's instruction to lock the high-end converter valve H1 and the low-end converter valve H2, the inverter side should not shift the phase by 90°, nor close the bypass switches BPS3 and BPS4. At time t2, the high-end converter valve H3 and the low-end converter valve H4 should be locked. The delay pulse time is generally 100ms, so t2 should be set to 360~1300ms.

[0062] Reference Figure 5The image shows an embodiment of the circulating current isolation control without communication DC line faults in the third circulating current isolation method provided by the present invention.

[0063] After a permanent DC ground fault occurs, the traveling wave protection on the rectifier side activates at time t0 and sends a phase-shifting restart signal. t0 should be set to 10–30 ms. If the DC voltage still fails to establish after the rectifier side completes the specified number of restarts, it is determined that the DC line restart was unsuccessful. At time t1, the high-side converter valve H1 and the low-side converter valve H2 are locked, and the high-side converter valve H1 is restarted sequentially. Therefore, t1 should also be set to 260–1200 ms. On the inverter side, at time t2, the low-voltage monitoring and control protection locks the high-side converter valve H3. The low-end converter valve H4 first shifts the phase to 90° to release the DC line energy. Since the low voltage monitoring and blocking delay on the inverter side is 6000ms, t2 is set to 6260~7200ms. After the inverter side shifts the phase to 90°, it executes the blocking command and enters the bypass mode at time t3, issuing a command to disconnect the neutral bus switch NBS2. The inverter side generally needs 200ms to perform the 90° phase shift operation and generally needs 30ms to close the bypass switch. Therefore, in this embodiment, t3 is set to 6490~7430ms.

[0064] Example 2:

[0065] This invention provides an isolation system for suppressing circulating currents during permanent grounding faults in DC lines, which can be used to implement the method described in Embodiment 1, specifically including:

[0066] The communication status judgment module is used to determine whether the inter-station communication is normal based on the detection of a permanent grounding fault in the DC line.

[0067] The first circulating current isolation module is used to execute the rectifier side fault clearing mode and disconnect the rectifier side neutral bus switch NBS1 and the inverter side neutral bus switch NBS2 after the low voltage monitoring and control protection is locked out when the inter-station communication is normal and the high-end converter valve group meets the restart conditions.

[0068] The second circulating isolation module is used to close the inverter-side bypass switch BPS3 and bypass switch BPS4 after the phase shift is 90° if the inter-station communication is normal and the high-end converter valve group does not meet the restart conditions. This locks the high-end converter valve H3 and the low-end converter valve H4 and disconnects the inverter-side neutral bus switch NBS2. If the lock is not set to bypass mode on the inverter side, the bypass switch BPS3 and bypass switch BPS4 are kept in the open state, and the inverter side is locked for a delay and does not perform a 90° phase shift.

[0069] The third circulating current isolation module is used to execute the inverter side fault clearing mode if the inter-station communication is abnormal, and to block the inverter side high-end converter valve H3 and low-end converter valve H4, and disconnect the inverter side neutral bus switch NBS2.

[0070] The circulating current isolation system for suppressing permanent grounding faults in DC lines provided in this embodiment of the invention is based on the same technical concept as the circulating current isolation method for suppressing permanent grounding faults in DC lines provided in Embodiment 1, and can produce the beneficial effects described in Embodiment 1. For the contents not described in detail in this embodiment, please refer to Embodiment 1.

[0071] Example 3:

[0072] This invention provides a terminal, including a processor and a storage medium;

[0073] The storage medium is used to store instructions;

[0074] The processor is configured to operate according to instructions to perform steps according to any of the methods in Embodiment 1.

[0075] Example 4:

[0076] This invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of any of the methods in Embodiment 1.

[0077] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0078] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0079] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0080] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for isolating circulating currents during permanent grounding faults in DC lines, characterized in that, The method includes: Based on the detected permanent grounding fault in the DC line, determine whether the inter-station communication is normal; If the inter-station communication is normal and the high-end converter valve group meets the restart conditions, the rectifier side fault clearing mode is executed. After the low voltage monitoring and control protection is locked, the rectifier side neutral bus switch NBS1 and the inverter side neutral bus switch NBS2 are disconnected. If the inter-station communication is normal and the high-end converter valve group does not meet the restart conditions, and the blocking setting for the inverter side is the bypass mode, then after the inverter side phase shifts to 90°, the inverter side bypass switch BPS3 and bypass switch BPS4 are closed, the high-end converter valve H3 and the low-end converter valve H4 are blocked, and the inverter side neutral bus switch NBS2 is disconnected; if the blocking setting for the inverter side is not the bypass mode, then the bypass switch BPS3 and bypass switch BPS4 are kept in the open state, the inverter side is delayed in blocking and the 90° phase shift is not performed. If the inter-station communication is abnormal, the inverter-side fault clearing mode is executed, the low voltage monitoring and control protection blocks the inverter-side high-end converter valve H3 and low-end converter valve H4, and disconnects the inverter-side neutral bus switch NBS2.

2. The method for suppressing circulating current isolation in permanent grounding faults of DC lines according to claim 1, characterized in that, The method further includes: after the rectifier side completes the set number of restarts, if the DC voltage is not established, the DC line restart is unsuccessful, and the high-end converter valve H1 and the low-end converter valve H2 on the rectifier side are directly locked.

3. The method for suppressing circulating current isolation in permanent grounding faults of DC lines according to claim 2, characterized in that, The number of restarts may include two restarts under the original pressure and one restart under reduced pressure, or only one restart under the original pressure.

4. The method for suppressing circulating current isolation in permanent grounding faults of DC lines according to any one of claims 1 to 3, characterized in that, The restart condition for the high-end converter valve group is that the operating conditions of ground mode wave, polar line wave, voltage, and current simultaneously meet the requirements for traveling wave protection operation.

5. The method for suppressing circulating current isolation in permanent grounding faults of DC lines according to claim 1, characterized in that, The steps for performing the rectifier-side fault clearing method include: If the DC line restarted on the rectifier side fails, the high-end converter valve H1 and low-end converter valve H2 on the rectifier side will be locked, and the high-end converter valve H1 will be restarted. After receiving the signal from the rectifier side to lock the high-end converter valve H1 and the low-end converter valve H2, the inverter side locks the high-end converter valve H3 and the low-end converter valve H4. If the high-side converter valve H1 fails to restart on the rectifier side, the high-side converter valve H1 will be locked by the low voltage monitoring and control protection on the rectifier side, and the neutral bus switch NBS1 on the rectifier side will be disconnected. After receiving the low voltage monitoring and control protection lockout signal from the rectifier side, the inverter side locks out the high-end converter valve H3 and disconnects the neutral bus switch NBS2 on the reverse side.

6. The method for suppressing circulating current isolation in permanent grounding faults of DC lines according to claim 1, characterized in that, The steps for performing the inverter-side fault clearing method include: If the DC line restarted on the rectifier side fails, the high-end converter valve H1 and the low-end converter valve H2 on the rectifier side will be locked. After receiving the signal from the rectifier side to lock the high-end converter valve H1 and the low-end converter valve H2, the inverter side shifts the phase to 90°. After the inverter side phase shifts to 90°, the inverter side bypass switches BPS3 and BPS4 are closed, the inverter side high-end converter valve H3 and low-end converter valve H4 are locked, and the inverter side neutral bus switch NBS2 is disconnected.

7. The method for suppressing circulating current isolation in permanent grounding faults of DC lines according to claim 1, characterized in that, The low voltage monitoring and control protection is either a low voltage protection action or a low voltage monitoring action.

8. A circulating current isolation system for suppressing permanent grounding faults in DC lines, characterized in that, The system includes: The communication status judgment module is used to determine whether the inter-station communication is normal based on the detection of a permanent grounding fault in the DC line. The first circulating current isolation module is used to execute the rectifier side fault clearing mode and disconnect the rectifier side neutral bus switch NBS1 and the inverter side neutral bus switch NBS2 after the low voltage monitoring and control protection is locked out when the inter-station communication is normal and the high-end converter valve group meets the restart conditions. The second circulating isolation module is used to close the inverter-side bypass switch BPS3 and bypass switch BPS4 after the phase shift is 90° if the inter-station communication is normal and the high-end converter valve group does not meet the restart conditions. This locks the high-end converter valve H3 and the low-end converter valve H4 and disconnects the inverter-side neutral bus switch NBS2. If the lock is not set to bypass mode on the inverter side, the bypass switch BPS3 and bypass switch BPS4 are kept in the open state, and the inverter side is locked for a delay and does not perform a 90° phase shift. The third circulating current isolation module is used to execute the inverter side fault clearing mode if the inter-station communication is abnormal, and to block the inverter side high-end converter valve H3 and low-end converter valve H4, and disconnect the inverter side neutral bus switch NBS2.

9. A terminal, characterized in that, Including processor and storage media; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method for isolating circulating currents in a DC line permanent ground fault as described in any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the method for isolating circulating currents in a permanent ground fault in a DC line as described in any one of claims 1 to 7.

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