Method, system and device for restarting a bipolar line fault in a high voltage direct current transmission system

Abstract

This invention discloses a method, system, and equipment for restarting a bipolar line in a high-voltage direct current (HVDC) transmission system after a fault. The method includes: each pole of the bipolar line in the HVDC transmission system detecting whether a fault has occurred in the DC line; when a fault is detected in one pole, deionization is controlled and a blocking restart signal is sent to the opposite pole; if the pole receives the blocking restart signal from the opposite pole within a time window, it is determined that the bipolar line is faulty; the pole to be blocked and restarted after the deionization time ends is determined based on the states of the two poles connected to the bipolar line. This invention, by adding a bipolar line fault detection function and improving the existing restart logic function, correctly identifies simultaneous faults in both bipolar DC lines. By using the DC line restart function to bypass the fault period, one pole performs restart while the other is directly blocked, reducing the impact of simultaneous bipolar blocking on the AC systems on both sides and improving the reliability of the power grid operation.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high voltage direct current transmission control, and particularly relates to a method, system and equipment for restarting bipolar lines in a high voltage direct current transmission system after a fault. Background Technology

[0002] In high-voltage direct current (HVDC) transmission projects, the DC line is a crucial component connecting the two converter stations and completing the transmission of DC power. The converter stations at both ends detect changes in the DC line voltage and current to determine whether a ground fault has occurred. When a ground fault is detected, the line restart function reduces the DC current to zero by phase shifting or controlling the DC current to zero. After a period of deionization to avoid the fault period, the voltage and current are re-established, restoring the DC system to operation.

[0003] The existing DC line restart function includes on-voltage restart and reduced-voltage restart. If the fault persists after a set number of on-voltage restarts, a reduced-voltage restart can be performed. If the reduced-voltage restart also fails, the DC line is blocked. The deionization time for DC line restart is determined according to the engineering design, generally set to 150ms for the first on-voltage restart, 200ms for the second on-voltage restart, and 200ms for the reduced-voltage restart. In bipolar operation, the restart functions of the two poles are mutually coordinated. When the bipolar DC power exceeds a set value, the restart function of the opposite pole is blocked for 5 seconds during the restart of one pole. If a line fault occurs on the other pole within these 5 seconds, the pole with the subsequent line fault is directly blocked. Therefore, when both bipolar DC lines experience faults simultaneously, both the pole and the opposite pole will receive a signal from the other pole to block the DC line restart function, resulting in simultaneous blocking of both poles and posing a risk to the stable operation of the power grids on both sides. A review of recent bipolar line fault types reveals that de-icing in AC / DC line crossing areas and foreign objects such as kites and membranes can all cause bipolar line faults. Currently, the consequence of protection activation for this type of fault is simultaneous bipolar blocking, which has a significant impact on the AC systems at both ends and is detrimental to grid stability. Because this type of fault is relatively short-lived, it can be classified as a transient bipolar DC line fault. By improving the control and protection logic, bipolar blocking caused by bipolar line faults can be avoided, thus preventing large power fluctuations from impacting the AC systems on both sides. Summary of the Invention

[0004] The purpose of this invention is to provide a method, system, and equipment for restarting bipolar lines in a high-voltage direct current transmission system after a fault, which can reduce the impact of simultaneous bipolar blocking on the AC systems on both sides and improve the reliability of power grid operation.

[0005] To achieve the above objectives, the solution of the present invention is:

[0006] A method for restarting a bipolar line in a high-voltage direct current transmission system after a fault includes,

[0007] In ultra-high voltage direct current transmission systems, each pole of a bipolar line detects whether a fault has occurred in the DC line; when a fault is detected in a pole, the deionization is controlled and a blocking restart signal is sent to the opposite pole.

[0008] If a pole receives a blocking restart signal from the opposite pole within the time window, it is determined to be a bipolar line fault.

[0009] The pole to be locked and restarted after the deionization time is determined based on the state of the two poles connected by the bipolar circuit.

[0010] The two poles connected by the bipolar line exchange information through inter-pole communication.

[0011] The time window is at least twice the inter-polar communication channel delay.

[0012] Among them, determining the pole to be locked and restarted after the phase shift deionization time ends includes selecting the optimal pole for restarting based on the principle of retaining the optimal pole for operation, and locking the other pole.

[0013] Among them, the principle of retaining the optimal pole operation includes determining the optimal pole based on the operating conditions of each pole.

[0014] A fault restart system for bipolar lines in a high-voltage direct current transmission system includes,

[0015] The DC line fault detection module is configured in each pole of the bipolar line in the UHVDC transmission system to detect whether a fault has occurred in the DC line of that pole.

[0016] The communication module is configured to send a blocking restart signal to the opposite pole when the DC line fault detection module detects a fault in the local pole line, and to receive a blocking restart signal from the opposite pole.

[0017] The fault diagnosis module is configured to determine a bipolar line fault upon receiving a blocking restart signal from the opposite pole within a time window after the communication module sends a blocking restart signal to the opposite pole; and,

[0018] The control module is configured to control deionization when the DC line fault detection module detects a fault in the local pole line, and to control blocking and restarting of the pole after the deionization time is determined based on the state of the two poles connected by the bipolar line.

[0019] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor; when the processor executes the computer program, it implements the steps of the above-described method for restarting a bipolar line fault in a high-voltage direct current transmission system.

[0020] A computer-readable storage medium storing a computer program; when executed by a processor, the computer program implements the steps of the above-described method for restarting a bipolar line fault in a high-voltage direct current transmission system.

[0021] By adopting the above scheme, the present invention improves and enhances the existing method. By adding a bipolar line fault detection function and improving the existing restart logic function, it correctly identifies the simultaneous faults of bipolar DC lines. By using the DC line restart function to avoid the fault period, one pole performs a restart while the other pole is directly blocked, reducing the impact of simultaneous bipolar blocking on the AC systems on both sides and improving the reliability of power grid operation. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual process of the method, etc. involved in the embodiments of this disclosure.

[0023] Figure 1 This is a schematic diagram of a typical ultra-high voltage direct current (UHVDC) project with bipolar wiring.

[0024] Figure 2 Logic diagram for the lockout restart signal;

[0025] Figure 3 Logic diagram for pre-locking pole selection in case of bipolar DC line fault. Detailed Implementation

[0026] This invention provides a method for restarting a bipolar line in a high-voltage direct current transmission system after a fault, comprising the following steps:

[0027] Step 1: Configure the restart function of the bipolar line in the high voltage DC transmission system according to the pole. Each pole connected to the bipolar line will detect whether the DC line of its own pole is faulty.

[0028] Step 2: When the restart function of the bipolar line of the high voltage DC transmission system detects a fault in the local pole line, it controls the deionization and sends a blocking restart signal to the opposite pole.

[0029] In particular, the restart function of the bipolar line of the high-voltage direct current transmission system configured on both poles can exchange information through inter-pole communication, and its communication channel has a delay T. delay This can be obtained through actual measurement;

[0030] Step 3: When the restart function of the bipolar line of the high-voltage DC transmission system of a certain pole sends a restart signal to the opposite pole when a restart signal is received from the opposite pole within the time window, it is determined to be a bipolar line fault.

[0031] The time window T for determining whether a polar line is faulty should be at least the inter-polar communication channel delay T. delay Twice as much;

[0032] Step 4: The restart function of the bipolar line in the high voltage DC transmission system determines whether to lock out or restart after the deionization time ends based on the state of the pole.

[0033] When a DC line fault is detected, the pole to be pre-locked is selected according to the principle of retaining the best pole operation, and the best pole executes the restart strategy; the pole to be pre-locked is determined according to the operating conditions of the two poles, such as the number of valve groups, control mode, and operating mode.

[0034] Existing DC line restart functions are configured per pole, with each pole detecting whether a fault has occurred in the DC line. When both poles experience a line fault simultaneously, both poles will simultaneously receive a restart prohibition signal from the opposite pole, thus directly blocking the restart process without performing a phase-shift restart. Considering the transmission time of the inter-pole signal link and software processing, tests show that it takes approximately 10ms for the pole to receive the restart prohibition signal from the opposite pole. According to the functional logic of existing technology, if the time interval between two line faults is less than 10ms, the fault status of both poles cannot be correctly identified, and a bipolar blockade will be executed. (If the time interval between two line faults is greater than 10ms, the control system can distinguish the order of the two line faults; the pole that faults first executes the line fault restart function and sends a restart blockade signal to the pole that faults later. Upon receiving this signal, the pole that faults later does not execute the restart function and directly blocks the restart.)

[0035] The restart process after a line fault lasts 150ms or 200ms, which is much longer than the 10ms inter-pole signal transmission time. Therefore, this time can be used to determine the fault status of the two poles. This invention addresses the situation where the time interval between line faults between poles is less than the 10ms inter-pole signal transmission and processing time. Simultaneously, a double communication delay detection window is activated when a blocking restart signal is sent to the opposite pole. That is, if the blocking restart signal from the opposite pole is received within 20ms, it is determined that a line fault has occurred simultaneously on both poles. In this case, one pole performs line restart while the other pole is blocked, avoiding bipolar blocking, reducing DC power loss, and mitigating AC grid impact.

[0036] The pole to be pre-locked is selected according to the principle of preserving the optimal pole operation. When a fault is detected in both poles of the DC line at the same time, the pole to be pre-locked is determined based on the operating conditions of each pole (pole 1 and pole 2), such as the number of valve groups, control mode, and operating mode. The specific execution method is as follows:

[0037] 1) When one pole is operating with a dual valve group and the other pole is operating with a single valve, the single valve operating pole is locked.

[0038] 2) When one pole is under bipolar power control and the other pole is under unipolar power / current control, the unipolar power / current control operating pole is blocked.

[0039] 3) When both poles are bipolar power control or unipolar power / current control, if one pole is operating at full voltage and the other is operating at reduced voltage, the pole operating at reduced voltage will be locked out first.

[0040] 4) If none of the above conditions can be determined, then select one of the poles to block, such as pole 1.

[0041] The technical solutions in some embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments provided by the present invention are within the scope of protection of the present invention.

[0042] like Figure 1 The high-voltage direct current (HVDC) transmission system shown is an ultra-high-voltage direct current (UHVDC) transmission system. Each station in an UHVDC transmission system includes two poles, and each pole includes two valve groups. The DC line restart function is configured per pole. Each pole can independently switch between bipolar power control and unipolar power control, as well as between full-voltage and step-down operation modes. Both valve groups on each pole can operate simultaneously, or only one valve group can operate. The selection of the pre-blocking pole when both poles experience simultaneous DC line faults is obtained by comparing the power control methods, full-voltage or step-down operation modes, and the number of operating valve groups of the two poles.

[0043] The following example illustrates the situation where the DC line of pole 1 fails first, followed by the DC line of pole 2, with the inter-pole communication time set at 10ms.

[0044] (1) The fault time interval between the two pole DC lines is greater than the inter-pole communication time of 10ms.

[0045] Assuming the fault time difference between the two poles is 12ms, after a fault occurs in the DC line of pole 1, when the bipolar power exceeds the limit, the line protection activates, generating the RL_BLK_OP signal to pole 2, and also generating a 20ms pulse width RL_BLK_WD signal. Figure 2As shown. Pole 2 receives the RL_BLK_FOP signal sent by pole 1 after 10ms. At this time, pole 2 has not yet failed, so it will not send the RL_BLK_OP signal to pole 1, and pole 2's RL_BLK_WD is 0, as... Figure 3 As shown, selector 4 selects the lower input and blocks the restart function of pole 2 by widening RL_BLK_FOP to RL_OPBLK_P signal for 5s. When pole 2 has a DC line fault after 12ms, it is directly blocked.

[0046] (2) The fault time interval between the two pole DC lines is less than 10ms between poles.

[0047] Assuming a 9.9ms time difference between the two faults, after a fault occurs on the DC line of pole 1, when the bipolar power exceeds the limit, the line protection activates, generating an RL_BLK_OP signal to pole 2 and a 20ms pulse-width RL_BLK_WD signal. Pole 2, after its line protection activates 9.9ms later, has not yet received the RL_BLK_FOP signal from pole 1, so it also generates an RL_BLK_OP signal to pole 1 and a 20ms pulse-width RL_BLK_WD signal. Considering a 10ms inter-pole communication delay, after 19.9ms, pole 1 receives the RL_BLK_FOP signal from pole 2, and... Figure 3 As shown, when pole 1 fails, the 20ms pulse width RL_BLK_WD signal still exists. At this time, selector 4 selects the upper input, and pole 1 determines whether to perform interlocking based on the operating mode. Similarly, since pole 2 fails at 9.9ms, considering the inter-pole communication delay of 10ms, pole 2 receives the RL_BLK_FOP signal from pole 1 at 10ms. At this time, the 20ms pulse width RL_BLK_WD signal generated when pole 2 fails still exists. Figure 3 As shown, at this time, selector 4 selects the upper input, and pole 2 determines whether to perform blocking based on the operating mode. Finally, when a bipolar DC line fault occurs, the optimal pole is selected through pre-blocking to perform line fault restart, while the other pole is directly blocked.

[0048] This invention also provides a fault restart system for bipolar lines in a high-voltage direct current transmission system, comprising:

[0049] A DC line fault detection module is configured in each pole of a bipolar line in a high-voltage DC transmission system to detect whether a fault has occurred in the DC line of that pole.

[0050] The communication module is configured to send a blocking restart signal to the opposite pole when the DC line fault detection module detects a fault in the local pole line, and to receive a blocking restart signal from the opposite pole.

[0051] The communication modules at both ends of the bipolar line can exchange information through inter-pole communication, and the communication channel delay T delay This can be obtained through actual measurement;

[0052] The fault diagnosis module is configured to determine a bipolar line fault upon receiving a blocking restart signal from the opposite pole within a time window after the communication module sends a blocking restart signal to the opposite pole; and,

[0053] The control module is configured to control deionization when the DC line fault detection module detects a fault in the local pole line, and to control blocking and restarting of the pole after the deionization time is determined based on the state of the two poles connected by the bipolar line.

[0054] Specifically, the time window T for the fault diagnosis module to determine whether the two pole lines are faulty should be at least the inter-pole communication channel delay T. delay Twice as much.

[0055] Specifically, when the fault judgment module determines a DC line fault, the control module selects the pre-locked pole according to the principle of retaining the optimal pole operation, and the optimal pole executes the phase shift restart strategy; the pre-locked pole is determined according to the operating conditions of the two poles, such as the number of valve groups, control mode, and operating mode.

[0056] This invention also provides another computer device, including a processor and a memory configured to store a computer program capable of running on the processor; wherein, when the processor is configured to run the computer program, it performs the method steps described in the foregoing embodiments.

[0057] In practical applications, the aforementioned processor includes a Field-Programmable Gate Array (FPGA), and the processor can be a Central Processing Unit (CPU) or a Digital Signal Processor (DSP). It is understood that for different devices, the electronic devices used to implement the functions of the aforementioned processor can also be other types, and this embodiment of the invention does not impose specific limitations.

[0058] The aforementioned memory can be volatile memory, such as random-access memory (RAM); or non-volatile memory, such as read-only memory (ROM), flash memory, hard disk drive (HDD), or solid-state drive (SSD); or a combination of the above types of memory, and provides instructions and data to the processor.

[0059] In an exemplary embodiment, the present invention also provides a computer-readable storage medium for storing a computer program.

[0060] Optionally, the computer-readable storage medium can be applied to any of the methods in the embodiments of the present invention, and the computer program causes the computer to execute the corresponding processes implemented by the processor in the various methods of the embodiments of the present invention. For the sake of brevity, these will not be described in detail here.

[0061] In the several embodiments provided by this invention, it should be understood that the disclosed devices and methods can be implemented in other ways. The device embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components can be combined, or integrated into another system, or some features can be ignored or not executed. In addition, the coupling, direct coupling, or communication connection between the various components shown or discussed can be through some interfaces, and the indirect coupling or communication connection between devices or units can be electrical, mechanical, or other forms.

[0062] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product implemented 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. The solutions in the embodiments of the present invention can be implemented using various computer languages, such as the object-oriented programming language Java and the interpreted scripting language JavaScript.

[0063] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. 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 illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0064] 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.

[0065] 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.

[0066] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0067] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for restarting a bipolar line in a high-voltage direct current transmission system after a fault, characterized in that: include, In a high-voltage direct current transmission system, each pole of a bipolar line detects whether a fault has occurred in the DC line; when a fault is detected in a pole, the deionization is controlled and a blocking restart signal is sent to the opposite pole. If a pole receives a blocking restart signal from the opposite pole within the time window, it is determined to be a bipolar line fault. The pole to be locked and restarted after the deionization time is determined based on the state of the two poles connected by the bipolar circuit.

2. The method as described in claim 1, characterized in that: The two poles connected by the bipolar line exchange information through inter-pole communication.

3. The method as described in claim 2, characterized in that: The time window is at least twice the inter-pole communication channel delay.

4. The method as described in claim 1, characterized in that: Determine the pole to be locked and restarted after the deionization time ends, including selecting the optimal pole for restarting based on the principle of retaining the optimal pole for operation, and locking the other pole.

5. The method as described in claim 4, characterized in that: The principle of retaining the optimal pole for operation includes selecting the pole with the better operating condition as the optimal pole based on the operating conditions of the two poles.

6. A fault restart system for bipolar lines in a high-voltage direct current transmission system, characterized in that: include, A DC line fault detection module is configured in each pole of a bipolar line in a high-voltage DC transmission system to detect whether a fault has occurred in the DC line of that pole. The communication module is configured to send a blocking restart signal to the opposite pole when the DC line fault detection module detects a fault in the local pole line, and to receive a blocking restart signal from the opposite pole. The fault judgment module is configured to determine a bipolar line fault when it receives a blocking restart signal from the opposite pole within a time window after the communication module sends a blocking restart signal to the opposite pole. as well as, The control module is configured to control deionization when the DC line fault detection module detects a fault in the local pole line, and to control blocking and restarting of the pole after the deionization time is determined based on the state of the two poles connected by the bipolar line.

7. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor; characterized in that: When the processor executes the computer program, it implements the steps of the method for restarting a bipolar line fault in a high-voltage direct current transmission system as described in any one of claims 1 to 5.

8. A computer-readable storage medium storing a computer program; characterized in that: When the computer program is executed by the processor, it implements the steps of the method for restarting a bipolar line fault in a high-voltage direct current transmission system as described in any one of claims 1 to 5.

Images