Direct current area fault positioning method, device and equipment for multi-terminal back-to-back flexible direct current power transmission system

Abstract

This application relates to a method, apparatus, and equipment for locating DC area faults in a multi-terminal back-to-back flexible DC transmission system. The system comprises multiple DC units. The method includes the following steps: acquiring information on the protection devices that have experienced a fault and the direction of the DC measuring point current in the multi-terminal back-to-back flexible DC transmission system; determining the fault area based on the protection device information; and determining the fault location in the DC area based on the direction of the DC measuring point current if the fault area is a single-pole grounding fault in the DC area. This method determines the fault area by acquiring the protection device information after a fault occurs, and then locates the fault location in the DC area by fusing the data based on the DC measuring point current direction, achieving precise determination of the specific location of the fault within the DC area, significantly improving the accuracy and response speed of fault judgment.

Description

Technical Field

[0001] This application relates to the field of fault location technology in power systems, and in particular to a method, apparatus and equipment for DC area fault location in a multi-terminal back-to-back flexible DC transmission system. Background Technology

[0002] With the large-scale development of new energy sources and changes in power load characteristics, the operation of new energy power systems faces more uncertainties, necessitating enhanced flexibility in power system regulation and continuous improvement in the safe operation and risk resistance capabilities of new energy power systems. Currently, some urban power grids face common problems such as excessive short-circuit currents in certain areas, insufficient mutual support capabilities (uneven distribution of power sources and loads), and inadequate extreme risk prevention capabilities. Flexible DC transmission technology VSC-HVDC is a new generation of high-voltage direct current transmission technology based on turn-off devices and voltage source converters. It possesses advantages such as multi-terminal interconnection and mutual support, strong comprehensive control capabilities, and flexible deployment, providing a new approach to effectively solving the problems of power grids in megacities. VSC-HVDC is an abbreviation for "Voltage Source Converter High Voltage Direct Current," referring to voltage source converter-type high-voltage direct current transmission.

[0003] To achieve power system resource sharing and allocation between different regions and address the imbalance in urban power grid development, a certain 220kV DC transmission system adopts four-terminal back-to-back flexible DC transmission technology. The converter station of this technology employs a ±120kV symmetrical monopole structure. The DC side of the converter station is connected by positive and negative busbars and isolated by a high-speed DC switch (HSS). Figure 1 As shown, the basic operating modes of four-terminal back-to-back flexible DC transmission technology include: single-terminal static synchronous compensator (STATCOM), two-terminal HVDC, three-terminal HVDC, four-terminal HVDC, and black start. Single-terminal converter stations are equipped with flexible DC transformer protection, AC connection bus protection, converter protection, and DC pole protection. To achieve fault location in the DC area of ​​multi-terminal converter stations, a multi-terminal protection coordination strategy should be designed; currently, there is a lack of fault location methods for the DC area. For example, when a fault occurs in the DC area of ​​a four-terminal back-to-back flexible DC transmission technology, phase-to-phase faults are easy to identify and operate. However, for single-point grounding faults, due to the large grounding resistance on the transformer valve side, the fault current is relatively small, with an amplitude of only tens of amperes, which cannot reach the operating threshold values ​​of overcurrent protection and differential protection. Furthermore, when a single-pole grounding fault occurs in the DC area, both the grounding overcurrent protection (such as 76SG) and DC voltage imbalance protection (such as 59 / 76DC) within the four-terminal converter station will operate, with little difference in fault characteristics, making it impossible to accurately distinguish the fault location. like Figure 2As shown, taking a positive DC bus fault as an example, when a ground fault occurs in the non-DC common area F7 and F18, due to the presence of a large grounding resistance, the differential current on both sides of the fault point is small. The differential protection of the bridge arm reactor (such as 87BR) cannot accurately identify the fault location. The positive voltage drops, and the ground fault current will flow through the neutral point of the valve side of the flexible DC transformer of the four DC units. The ground overcurrent protection (76SG) of the four-terminal DC unit will meet the criterion action. At the same time, the DC voltage imbalance protection (59 / 76DC) will also meet the protection criterion action: |UdP+UdN|>U_set1&IacZ≥I_set. It is impossible to accurately distinguish the fault end and maintain the normal operation of the non-fault end. UdP is the positive DC pole line voltage, UdN is the negative DC pole line voltage, IacZ is the valve side neutral point current of the flexible DC transformer, U_set1 is the voltage setting value, and I_set is the current action setting value. When a ground fault occurs in the non-DC common area F7, F18 or the DC common area F9, the ground overcurrent protection (76SG) of the four-terminal converter station will meet the criteria and operate. At the same time, the DC voltage imbalance protection (59 / 76DC) will also meet the protection criteria: |UdP+UdN|>U_set1&IacZ≥I_set. The protection operation cannot accurately distinguish the fault area of ​​the DC unit on this side and cannot achieve fault isolation. Summary of the Invention

[0004] This application provides a method, apparatus, and equipment for locating DC area faults in a multi-terminal back-to-back flexible DC transmission system, which solves the technical problem that existing flexible DC transmission systems cannot accurately distinguish the location of faults when they occur in the DC area.

[0005] To achieve the above objectives, this application provides the following technical solution:

[0006] On the one hand, a method for locating DC area faults in a multi-terminal back-to-back flexible DC transmission system is provided, applied to the multi-terminal back-to-back flexible DC transmission system, which includes multiple DC units. The method for locating DC area faults includes the following steps:

[0007] Obtain information on the protection devices that have experienced faults and the direction of the DC measuring point current in the multi-terminal back-to-back flexible DC transmission system;

[0008] Based on the information from the protection device, determine the fault area;

[0009] If the fault area is a single-pole grounding fault in the DC area, the fault location in the DC area is determined according to the direction of the DC measuring point current.

[0010] Optionally, determining the fault location in the DC region based on the direction of the DC measuring point current includes:

[0011] If the positive DC measuring point current direction of all the DC units in the DC measuring point current direction is positive, then the fault location is the positive DC common area; if the negative DC measuring point current direction of all the DC units in the DC measuring point current direction is negative, then the fault location is the negative DC common area.

[0012] If only one of the DC measuring point current directions of the DC unit has a negative positive DC measuring point current direction, then the fault location is the non-DC common area of ​​the DC unit corresponding to the negative positive DC measuring point current direction; if only one of the DC measuring point current directions of the DC unit has a positive negative DC measuring point current direction, then the fault location is the non-DC common area of ​​the DC unit corresponding to the positive negative DC measuring point current direction.

[0013] In the event of a fault in the multi-terminal back-to-back flexible DC transmission system, after the DC unit is locked out and before the AC circuit breaker and the DC high-speed switch are disconnected, the direction of the positive DC measuring point current or the direction of the negative DC measuring point current of the DC unit is obtained as the direction of the DC measuring point current.

[0014] Optionally, the DC area fault location method for the multi-terminal back-to-back flexible DC transmission system further includes: determining a control execution strategy based on the fault location.

[0015] Optionally, the multi-terminal back-to-back flexible DC transmission system further includes an AC circuit breaker and a DC high-speed switch connected to each of the DC units. The control execution strategy is determined based on the fault location, including:

[0016] If the fault location is in the DC common area, then all AC circuit breakers and all DC high-speed switches will be disconnected, and all DC units will stop operating.

[0017] If the fault location is in the non-DC common area of ​​the DC unit corresponding to the positive DC measuring point current direction being negative or the negative DC measuring point current direction being positive, then the DC high-speed switch connected to the faulty DC unit is disconnected, the other DC units are restarted, the working state of the DC high-speed switches connected to the other DC units remains unchanged, and the AC circuit breakers connected to the other DC units are closed.

[0018] Optionally, determining the fault area based on the protection device information includes:

[0019] If the protection device information indicates that the DC voltage imbalance protection and grounding overcurrent protection of all the DC units operate simultaneously, then the fault area is a single-pole grounding fault in the DC area.

[0020] If the protection device information indicates that the DC voltage imbalance protection of all DC units is not activated, then the fault area is a single-pole grounding fault in a non-DC area.

[0021] On the other hand, a DC area fault location device for a multi-terminal back-to-back flexible DC transmission system is provided, which is applied to the multi-terminal back-to-back flexible DC transmission system. The multi-terminal back-to-back flexible DC transmission system includes multiple DC units, and the DC area fault location device includes: a data acquisition module, a fault area determination module, and a fault location determination module.

[0022] The data acquisition module is used to acquire information on the protection devices that have failed in the multi-terminal back-to-back flexible DC transmission system and the direction of the DC measuring point current.

[0023] The fault area determination module is used to determine the fault area based on the protection device information;

[0024] The fault location determination module is used to determine the fault location in the DC region based on the fact that the fault region is a single-pole grounding fault in the DC region and the direction of the DC measuring point current.

[0025] Optionally, the multi-terminal back-to-back flexible DC transmission system further includes an AC circuit breaker and a DC high-speed switch connected to each of the DC units. The fault location determination module is further configured to determine the fault location as follows: if the positive DC measuring point current direction of all the DC units is positive, the fault location is in the positive DC common area; if the negative DC measuring point current direction of all the DC units is negative, the fault location is in the negative DC common area; or, if only one of the DC units has a negative positive DC measuring point current direction, the fault location is in the negative DC common area. The fault location is defined as the non-DC common area of ​​the DC unit corresponding to the negative direction of the positive DC measuring point current. If only one of the DC measuring point current directions has a positive negative DC measuring point current direction, then the fault location is defined as the non-DC common area of ​​the DC unit corresponding to the positive negative DC measuring point current direction. Specifically, when a fault occurs in the multi-terminal back-to-back flexible DC transmission system, after the DC unit is locked out, and before the AC circuit breaker and the DC high-speed switch are disconnected, the positive or negative DC measuring point current direction of the DC unit is obtained as the DC measuring point current direction.

[0026] Optionally, the DC area fault location device of the multi-terminal back-to-back flexible DC transmission system further includes an execution module, which is used to determine a control execution strategy based on the fault location.

[0027] Optionally, the execution module is further configured to, based on the fault location being in the DC common area, control all AC circuit breakers and all DC high-speed switches to disconnect and all DC units to stop operating; or, based on the fault location being in the non-DC common area of ​​the DC unit corresponding to the DC unit where the positive DC measuring point current direction is negative or the negative DC measuring point current direction is positive, control the DC high-speed switch connected to the faulty DC unit to disconnect, control the other DC units to restart, and maintain the operating state of the DC high-speed switches connected to other DC units unchanged and the AC circuit breakers connected to other DC units to close.

[0028] On the other hand, a terminal device is provided, including a processor and a memory;

[0029] The memory is used to store program code and transmit the program code to the processor;

[0030] The processor is used to execute the DC area fault location method of the multi-terminal back-to-back flexible DC transmission system described above, according to the instructions in the program code.

[0031] The DC area fault location method, device, and equipment for a multi-terminal back-to-back flexible DC transmission system are applied to such systems, which include multiple DC units. The DC area fault location method includes the following steps: obtaining information on the protection devices that have caused the fault in the multi-terminal back-to-back flexible DC transmission system and the direction of the DC measuring point current; determining the fault area based on the protection device information; and determining the fault location in the DC area based on the direction of the DC measuring point current if the fault area is a single-pole grounding fault in the DC area.

[0032] As can be seen from the above technical solutions, this application has the following advantages: The DC area fault location method of the multi-terminal back-to-back flexible DC transmission system determines the fault area by obtaining the information of the protection device after the fault occurs. Based on the fact that the fault area is a DC area fault, the location of the DC area fault is located by fusing the data of the DC measuring point current direction. This achieves accurate determination of the specific location of the fault within the DC area, significantly improves the accuracy of fault judgment and response speed, and solves the technical problem that existing flexible DC transmission systems cannot accurately distinguish the fault location when a DC area fault occurs.

[0033] The DC area fault location device of this multi-terminal back-to-back flexible DC transmission system, through a data acquisition module, a fault area determination module, and a fault location determination module, can effectively distinguish the fault location of non-DC common area and DC common area when a fault occurs at this end, and implement effective fault isolation methods and restart strategies; it can also effectively identify the fault location of a certain DC unit in the non-DC common area and quickly isolate the fault. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is the main wiring diagram of an existing four-terminal back-to-back flexible DC transmission system.

[0036] Figure 2 A schematic diagram of the fault points in an existing multi-terminal back-to-back flexible DC transmission system;

[0037] Figure 3 This is a flowchart illustrating the steps of the DC area fault location method for a multi-terminal back-to-back flexible DC transmission system described in an embodiment of this application.

[0038] Figure 4 This is a discharge circuit diagram of a fault occurring at the sending-end converter unit F7 or F18 in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in this application embodiment.

[0039] Figure 5 This is a discharge circuit diagram of a fault occurring at the receiving-end converter unit F7 or F18 in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in this application embodiment.

[0040] Figure 6 This is a discharge circuit diagram of a fault occurring at F9 of the sending-end converter in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in this application embodiment.

[0041] Figure 7 This is a simulation diagram of the positive DC current and protection action of the four terminals of the P3-F7 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0042] Figure 8 Simulation diagram of the positive DC current and protection action of the four terminals of the P2-F7 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0043] Figure 9 This is a simulation diagram of the positive DC current and protection action of the four terminals of the P3-F18 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0044] Figure 10 Simulation diagram of the positive DC current and protection action of the four terminals of the P2-F18 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0045] Figure 11 This is a simulation diagram of the positive DC current and protection action of the four terminals of the P3-F9 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0046] Figure 12 Simulation diagram of the positive DC current and protection action of the four terminals of the P2-F9 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0047] Figure 13 Simulation diagram of the positive DC current and protection action of the four terminals of the P1-F7 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0048] Figure 14 Simulation diagram of the positive DC current and protection action of the four terminals of the P1-F9 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0049] Figure 15 This is a schematic diagram of the frame of the DC area fault location device for the multi-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0050] Figure 16 This is a schematic diagram of the terminal device described in an embodiment of this application. Detailed Implementation

[0051] To make the inventive objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0052] In the description of the embodiments of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0053] In the embodiments of this application, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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 refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0054] Patent terminology:

[0055] A high-speed DC switch (HSS) is a key piece of equipment used in multi-terminal DC transmission systems. Composed of nearly a thousand precision components, it is designed to achieve millisecond-level rapid switching operations. In two-terminal DC projects, traditional disconnect switches have an operating time of approximately 24 seconds, which cannot support online connection / disconnection or rapid fault isolation at third-terminal sites. In contrast, the operating time of a high-speed DC switch is only 21 milliseconds, significantly improving the flexibility and reliability of system operation.

[0056] This application provides a method, apparatus, and device for locating DC area faults in a multi-terminal back-to-back flexible DC transmission system, solving the technical problem that existing flexible DC transmission systems cannot accurately distinguish the location of faults in the DC area. This method, apparatus, and device for locating DC area faults in a multi-terminal back-to-back flexible DC transmission system is applied to such systems, including three-terminal back-to-back flexible DC transmission systems and four-terminal back-to-back flexible DC transmission systems.

[0057] In the embodiments of this application, the protection devices configured in the DC generation area of ​​the multi-terminal back-to-back flexible DC transmission system include DC overvoltage protection (59DC), DC undervoltage protection (27DC), bridge arm reactor differential protection (87BR), DC voltage imbalance protection (59 / 76DC), DC undervoltage overcurrent protection (27 / 76DC), and grounding overcurrent protection (76SG), etc., and the positive direction of the DC current flowing from the positive pole of the converter unit to the DC side is defined as positive. Among them, the criterion for the differential protection of the bridge arm reactor (87BR) is: Idif_P>max(Ihbd_set1, k_set1*Ires_P), Idif_P=|ΣIbP+IdP|, Ires_P=0.5|ΣIbP-IdP|; the criterion for the DC voltage imbalance protection (59 / 76DC) is: |UdP+UdN|>U_set1&IacZ≥I_set; the criterion for the grounding overcurrent protection (76SG) is: |IacZ_RMS|>I_set. In the formula, Idif_P is the differential current of the upper arm reactor of the converter unit, Ihbd_set1 is the differential current starting setting, Ires_P is the braking current of the upper arm reactor, k_set1 is the differential proportional coefficient, IbP and IdP are the upper arm current and lower arm current respectively; IacZ_RMS is the effective value of the neutral point current on the transformer valve side, and Iset is the current operating setting.

[0058] Example 1:

[0059] Figure 3 This is a flowchart illustrating the steps of the DC area fault location method for a multi-terminal back-to-back flexible DC transmission system described in an embodiment of this application.

[0060] like Figure 3 As shown, this application provides a DC area fault location method for a multi-terminal back-to-back flexible DC transmission system, which is applied to the multi-terminal back-to-back flexible DC transmission system, including multiple DC units.

[0061] It should be noted that the number of DC units in a multi-terminal back-to-back flexible DC transmission system is determined based on the number of terminals in the back-to-back flexible DC transmission system. For example, a four-terminal back-to-back flexible DC transmission system corresponds to four DC units. In this embodiment, the DC unit includes a converter station.

[0062] like Figure 1 As shown, the DC area fault location method of this multi-terminal back-to-back flexible DC transmission system includes the following steps:

[0063] S1. Obtain information on the protection devices that have experienced faults and the direction of the DC measuring point current in the multi-terminal back-to-back flexible DC transmission system.

[0064] It should be noted that in the DC area fault location process of the multi-terminal back-to-back flexible DC transmission system, step S1 involves acquiring data from the multi-terminal back-to-back flexible DC transmission system after a fault occurs in the DC area. This data includes protection device information and the direction of DC measuring point current, providing judgment data for subsequent fault location. In this embodiment, the protection device information includes the activation status, action time, and fault location data of each protection device, used to determine the fault situation and take corresponding protection measures. The direction of DC measuring point current refers to the direction of the positive DC current of each converter unit, and the positive direction of the positive DC current flowing towards the DC side is defined as positive. The negative current refers to the value of the negative DC current of each converter unit.

[0065] For example, step S1 can be understood as follows: During the fault location process in the DC area of ​​a multi-terminal back-to-back flexible DC transmission system, it is necessary to acquire various information related to the protection device when a fault occurs in the DC area during the operation of the multi-terminal back-to-back flexible DC transmission system; simultaneously, it is necessary to acquire the current direction data at each measuring point on the DC side, as well as the specific current value on the negative line. The information related to the protection device may include the protection device's activation status, operating time, protection type, fault location data, etc., used to determine the fault situation and take corresponding protection measures. The current direction at the DC measuring point is crucial for determining the fault location, fault area, and the propagation path of the fault current. The magnitude of the negative current is an important basis for analyzing the fault characteristics of the DC system, assessing the severity of the fault, and performing fault isolation and system recovery.

[0066] S2. Determine the fault area based on the information from the protection device.

[0067] It should be noted that step S2 is based on step S1, which integrates protection device information such as the action signals of the protection devices, fault waveform data, electrical quantity measurements, and equipment status to achieve accurate identification and location of the fault area, providing data for subsequent fault location determination. In this embodiment, if the protection device information indicates that the DC voltage imbalance protection and grounding overcurrent protection of all DC units operate simultaneously, the fault area is a single-pole grounding fault in the DC area; if the protection device information indicates that the DC voltage imbalance protection of all DC units does not operate, the fault area is a single-pole grounding fault in the non-DC area.

[0068] In other embodiments, if the protection device information indicates grounding protection activation and the fault recording data shows abnormal zero-sequence current or voltage, the fault area can be determined to be a single-pole grounding fault in a non-DC area. If the protection device information indicates overload protection activation and the fault recording data shows that the current exceeds the rated value for a long time but does not reach the short-circuit current level, the fault area can be determined to be an overload fault in a non-DC area. This DC area fault location method for a multi-terminal back-to-back flexible DC transmission system determines the fault area for different faults through protection device information and the activation information of various protection devices.

[0069] S3. If the fault area is a single-pole grounding fault in the DC area, the fault location in the DC area is determined according to the direction of the DC measuring point current.

[0070] It should be noted that step S3, based on step S2 determining that the fault area is a DC area fault, judges the DC measurement point current direction data obtained in step S1 to determine whether the fault location is in the common area or non-common area of ​​the DC region of the multi-terminal back-to-back flexible DC transmission system, thus realizing the determination of the DC area fault location of the multi-terminal back-to-back flexible DC transmission system. In this embodiment, the DC area fault location method of the multi-terminal back-to-back flexible DC transmission system can accurately locate the DC area fault by acquiring the information of the faulty protection device and the DC measurement point current direction data, and can quickly isolate the fault and restore the operation of the non-faulty end.

[0071] For example, step S3 can be understood as using the current flow direction information at each measuring point on the DC side obtained from the multi-terminal back-to-back flexible DC transmission system, along with the real-time current value of the negative line, to comprehensively analyze this multi-dimensional data through a specific fault location algorithm or logical judgment process, thereby accurately determining the specific location of the fault within the DC area. For instance, when the current direction at a certain DC measuring point is abnormal and the negative current suddenly increases, and the corresponding protection device is activated, the fault area can be narrowed down by combining the wiring method of the multi-terminal back-to-back flexible DC transmission system; further, by comparing the differences in data from each DC measuring point, the fault location can be finally pinpointed. Locating the fault location in the DC area by fusing multi-source data such as the current direction at DC measuring points and the negative current can significantly improve the accuracy and response speed of fault judgment.

[0072] This application provides a DC area fault location method for a multi-terminal back-to-back flexible DC transmission system, applied to such systems. The multi-terminal back-to-back flexible DC transmission system includes multiple DC units. The DC area fault location method comprises the following steps: acquiring information on the protection devices that have experienced a fault and the direction of the DC measuring point current in the multi-terminal back-to-back flexible DC transmission system; determining the fault area based on the protection device information; and if the fault area is a single-pole grounding fault in the DC area, determining the fault location in the DC area based on the direction of the DC measuring point current. This DC area fault location method for multi-terminal back-to-back flexible DC transmission systems determines the fault area by acquiring the protection device information after a fault occurs. Based on the fact that the fault area is a DC area fault, it further locates the fault location in the DC area by fusing data from the direction of the DC measuring point current. This achieves precise determination of the specific location of the fault within the DC area, significantly improving the accuracy and response speed of fault judgment, and solving the technical problem of existing flexible DC transmission systems being unable to accurately distinguish the fault location when a fault occurs in the DC area.

[0073] In one embodiment of this application, the DC area fault location method of the multi-terminal back-to-back flexible DC transmission system further includes: after a fault occurs in the DC area of ​​the multi-terminal back-to-back flexible DC transmission system, after the DC unit is locked and before the AC circuit breaker and the DC high-speed switch are disconnected, obtaining the positive DC measuring point current direction or the negative DC measuring point current direction of the DC unit as the DC measuring point current direction.

[0074] It should be noted that after a fault occurs in the DC region of a multi-terminal back-to-back flexible DC transmission system, within a specific time window (i.e., before the DC unit's blocking action is completed but the AC circuit breaker and DC high-speed switch have opened), the current flow direction data of the positive line of the DC unit is acquired through a measuring device. This positive or negative DC measuring point current direction information is then used as the DC measuring point current direction required for subsequent fault location analysis. The DC measuring point current direction is obtained from transient data captured after the DC unit is blocked but before the switches (AC circuit breaker and DC high-speed switch) open, significantly improving the accuracy of fault location, and is particularly suitable for the rapid protection requirements of high-voltage, high-capacity flexible DC systems.

[0075] For example, when a fault occurs in the DC region of a multi-terminal back-to-back flexible DC transmission system, the first step is to trigger the blocking protection of the DC-side equipment (such as DC units composed of converters) to prevent the fault current from expanding further. During the brief interval between the completion of the DC unit blocking and the physical disconnection of the AC-side circuit breaker and the DC high-speed switch, the system remains in a measurable electrical state. Obtaining the positive or negative current direction at this time reflects the true propagation path of the fault current within the DC region, avoiding the loss of crucial characteristic information due to sudden current drops or abrupt changes in direction caused by switch disconnection. Specifically, if the positive DC current direction indicates current flowing from the converter to the DC line, while the negative current abnormally increases, combined with the protection device activation signal, it can be inferred that the fault point is located in a section of the DC line, rather than inside the converter.

[0076] In one embodiment of this application, determining the fault location in the DC region based on the direction of the DC measuring point current includes:

[0077] If the positive DC measuring point current direction of all DC units in the DC measuring point current direction is positive, then the fault location is the positive DC common area; if the negative DC measuring point current direction of all DC units in the DC measuring point current direction is negative, then the fault location is the negative DC common area.

[0078] If only one DC unit has a negative positive DC measuring point current direction, the fault location is in the non-DC common area of ​​the DC unit corresponding to the negative positive DC measuring point current direction; if only one DC unit has a positive negative DC measuring point current direction, the fault location is in the non-DC common area of ​​the DC unit corresponding to the positive negative DC measuring point current direction.

[0079] It should be noted that during the fault location determination process based on the information of the protection device, the direction of the DC measuring point current and the negative current, after a fault occurs in the DC area of ​​the multi-terminal back-to-back flexible DC transmission system, the positive voltage of the DC line will decrease. If the DC voltage imbalance protection (59 / 76DC) and grounding overcurrent protection (76SG) of multiple DC units will both meet the criteria and operate simultaneously, and the direction of the DC measuring point current on the positive DC side of each terminal is positive, it is determined that the fault occurs in the DC common area and the fault is a single-pole grounding fault. If the DC voltage imbalance protection (59 / 76DC) and grounding overcurrent protection (76SG) of multiple DC units simultaneously meet the criteria and operate, locking each DC unit (controlling the operation of the DC unit), and controlling the AC circuit breaker at each end to open, then the positive DC measuring point current direction at the fault end is negative or the negative DC measuring point current direction is positive. Based on this, it can be determined that the fault occurred in a non-DC common area, and the fault is a single-pole grounding fault. This allows the DC area fault location method of this multi-terminal back-to-back flexible DC transmission system to achieve fault location of a DC unit in a non-DC common area. In this embodiment, if a grounding fault occurs, the DC voltage imbalance protection (59 / 76DC) and grounding overcurrent protection (76SG) of each DC unit operate simultaneously, and the positive DC measuring point current (e.g., ...) of the DC unit... Figure 1 If all IDP values ​​are positive, the fault can be identified as a single-pole ground fault in the DC common area (e.g., Figure 1 (at F9); if a ground fault occurs, the DC voltage imbalance protection (59 / 76DC) and ground overcurrent protection (76SG) of each DC unit will operate simultaneously, and only the positive DC measuring point current of a certain DC unit will be negative. The fault can be identified as a single-pole ground fault in a DC unit in a non-DC common area (e.g., at F9). Figure 1 (At F7 or F18).

[0080] Figure 4 This is a discharge circuit diagram of a fault occurring at converter unit F7 or F18 at the sending end in the DC region fault location method of the four-terminal back-to-back flexible DC transmission system described in this application embodiment. Figure 5 This is a discharge circuit diagram of a fault occurring at the receiving-end converter unit F7 or F18 in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in this application embodiment. Figure 6 This is a discharge circuit diagram of a fault occurring at the sending-end converter F9 in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in this application embodiment.

[0081] like Figures 4 to 6As shown in the embodiments of this application, the DC area fault location method of the multi-terminal back-to-back flexible DC transmission system is illustrated using a four-terminal back-to-back flexible DC transmission system as an example, with converters as converter units. Converter 1 and converter 2 are used as receiving ends, and converter 3 and converter 4 are used as sending ends. The positive direction of the current measurement point in the DC area is defined as follows: Figure 1 As shown, during normal operation, the positive DC current directions of the four-terminal converter are -, -, +, and +, respectively.

[0082] For example, when a single-pole ground fault occurs in the non-common area (such as F7 or F18) of the sending-end converter, taking the ground fault on the positive DC bus of converter 3 as an example, the DC voltage imbalance protection (59 / 76DC) and grounding overcurrent protection (76SG) of the four-terminal converter will both meet the protection criteria and operate, locking the converter valve of the four-terminal converter. When the DC high-speed switch HSS on the DC side is not open, the capacitor discharge of the four-terminal converter causes the short-circuit current to feed into the fault point. Since the fault points F7 and F18 are on the opposite side of the DC measurement point IDP at the fault end, the current direction of the DC measurement point at the fault end becomes negative, while the current direction of the DC measurement point at the non-fault end is positive. Figure 4 As shown, at this time, the direction of the positive DC current of the four-terminal converter changes to +, +, -, +, and the value of the negative positive current becomes 0. When a ground fault occurs in the non-common area of ​​the receiving-end converter (such as at F7 or F18), taking the ground fault at the positive terminal of converter 2 as an example, the DC voltage imbalance protection (59 / 76DC) and the ground overcurrent protection (76SG) of the four-terminal converter will both meet the protection criteria and operate, blocking the converter valve of the four-terminal converter. When the DC high-speed switch HSS on the DC side is not disconnected, the capacitor discharge of the four-terminal converter causes the short-circuit current to feed into the fault point. Since the fault points F7 and F18 are on the opposite side of the DC measurement point IDP, the direction of the DC measurement point current at the fault end becomes negative, while the direction of the DC measurement point current at the non-fault end is positive. Figure 5 As shown, at this time, the direction of the positive DC current of the four-terminal converter becomes +, -, +, +, and the value of the negative positive current becomes 0.

[0083] For another example, when a ground fault occurs at point F9 in the DC common area of ​​the sending and receiving converters, both the DC voltage imbalance protection (59 / 76DC) and the ground fault overcurrent protection (76SG) of the four-terminal converter will meet the protection criteria and operate, locking the converter valve of the four-terminal converter. If the DC high-speed switch HSS on the DC side is not open, the capacitor discharge of the four-terminal converter causes a short-circuit current to flow into the fault point. Since the fault point F9 is on the positive side of the DC measurement point IDP at the fault end, if... Figure 6 As shown, at this time, the positive DC current direction of the four-terminal converter is +, and the negative positive current value becomes 0.

[0084] Figure 7This is a simulation diagram of the positive DC current and protection operation of the four terminals of the P3-F7 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application. Figure 8 This is a simulation diagram of the positive DC current and protection operation of the four terminals of the P2-F7 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application. Figure 9 This is a simulation diagram of the positive DC current and protection operation at the four terminals of the P3-F18 fault location method for the DC area of ​​the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application. Figure 10 This is a simulation diagram of the positive DC current and protection action of the four terminals of the P2-F18 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0085] In the embodiments of this application, according to Figure 1 The topology was used to construct a simulation model in the electromagnetic transient simulation software of the power system. In the simulation model, ground faults were set at F7 and F18 in the non-DC common area of ​​converters 2 and 3, respectively. The fault occurred after 5 seconds and lasted for 1 second. The waveforms of the positive DC current of the four-terminal converters and the protection action after the fault are shown in the figure. Figures 6 to 10 As shown. By Figure 7 It can be seen that a ground fault occurred at F7 of converter 3 at 5s. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter tripped; 11ms later, the ground overcurrent protection 76SG tripped; 20ms later, the four-terminal converter was locked; 50ms later, the AC circuit breaker tripped; and 60ms later, the DC high-speed switch HSS opened. Between the lockout and tripping of the four-terminal converter, only the current direction at the positive DC measuring point of converter 3 at the fault end changed from positive to negative. Figure 8 It can be seen that a ground fault occurred at F7 of converter 2 at 5s. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter tripped; 11ms later, the ground overcurrent protection 76SG tripped; 20ms later, the four-terminal converter was locked out; 50ms later, the AC circuit breaker tripped; and 60ms later, the DC high-speed switch HSS tripped. After the four-terminal converter was locked out but before tripping, only the positive DC measuring point current of the faulty converter 2 was negative. Figure 9 It can be seen that a ground fault occurred at F18 of converter 3 at 5s. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter tripped; 11ms later, the ground overcurrent protection 76SG tripped; 20ms later, the four-terminal converter was locked out; 50ms later, the AC circuit breaker opened; and 60ms later, the DC high-speed switch HSS opened. After the four-terminal converter was locked out but before tripping, only the current direction at the positive DC measuring point of the faulty converter 3 changed from positive to negative. Figure 10It can be seen that at 5s, a ground fault occurred at F18 of converter 2. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter was activated. 11ms later, the ground overcurrent protection 76SG was activated. 20ms later, the four-terminal converter was locked. 50ms later, the AC circuit breaker was opened. 60ms later, the DC high-speed switch HSS was opened. After the four-terminal converter was locked and before the trip, only the positive DC measuring point current of the faulty converter 2 was negative.

[0086] Figure 11 This is a simulation diagram of the positive DC current and protection operation of the four terminals of the P3-F9 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application. Figure 12 This is a simulation diagram of the positive DC current and protection action of the four terminals of the P2-F9 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0087] In the embodiments of this application, according to Figure 1 The topology was used to construct a simulation model in the electromagnetic transient simulation software of the power system. In the simulation model, a ground fault was set at F9, the DC common area of ​​converters 2 and 3, occurring after 5 seconds and lasting for 1 second. The waveforms of the positive DC current of the four-terminal converters and the protection action after the fault are shown below. Figure 11 and Figure 12 As shown. By Figure 11 It can be seen that a ground fault occurred at F9 of converter 3 at 5s. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter tripped; 11ms later, the ground overcurrent protection 76SG tripped; 20ms later, the four-terminal converter was locked out; 50ms later, the AC circuit breaker opened; and 60ms later, the DC high-speed switch HSS opened. After the four-terminal converter was locked out but before tripping, the positive DC current direction of the four-terminal converter was positive. Figure 12 It can be seen that at 5s, a ground fault occurred at F9 of converter 2. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter was activated. 11ms later, the ground overcurrent protection 59 / 76DC was activated. 20ms later, the four-terminal converter was locked. 50ms later, the AC circuit breaker was opened. 60ms later, the DC high-speed switch HSS was opened. After the four-terminal converter was locked and before the trip, the positive DC current direction of the four-terminal converter was also positive.

[0088] In this embodiment, when a ground fault occurs at F7 or F18 in the sending or receiving converter, after the four-terminal converter is locked but before tripping, the fault current of the non-faulty converter flows to the fault point through the positive DC measuring point current of the faulty terminal. Therefore, only the positive DC measuring point current of the faulty terminal is negative. When a ground fault occurs at F9 in the sending or receiving converter, after the four-terminal converter is locked but before tripping, the fault current of the four-terminal converter flows to the fault point through the positive DC measuring point current of its own terminal. Therefore, the positive DC current direction is positive in both cases.

[0089] It should be noted that the fault location of the negative grounding fault in the DC area of ​​the multi-terminal back-to-back flexible DC transmission system is the same, and the conclusion is the same as that of the positive grounding fault.

[0090] Figure 13 This is a simulation diagram of the positive DC current and protection operation of the four terminals of the P1-F7 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application. Figure 14 This is a simulation diagram of the positive DC current and protection action of the four terminals of the P1-F9 fault in the DC area fault location method of the four-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0091] In this embodiment, the DC area fault location method for the multi-terminal back-to-back flexible DC transmission system takes a four-terminal back-to-back flexible DC transmission system with one sending end and three receiving ends as an example, and the converters are used as converter units. Converter 1 is the sending end, and converters 2, 3, and 4 are the receiving ends. During normal operation, the positive DC current directions of the four converters are +, -, -, and -, respectively. When a ground fault occurs at F7 or F18 of the sending-end converter, taking the ground fault at the positive terminal of converter 1 as an example, the DC voltage imbalance protection (59 / 76DC) and grounding overcurrent protection (76SG) of the four-terminal converter will both meet the protection criteria and operate, locking the four-terminal converter valve. When the DC high-speed switch HSS on the DC side is not disconnected, the capacitor discharge of the four-terminal converter causes the short-circuit current to be fed into the fault point. Since the fault point F7 or F18 is on the opposite side of the DC measurement point IDP at the fault end, the direction of the DC measurement point current at the fault end becomes negative, while the direction of the DC measurement point current at the non-fault end is positive. At this time, the direction of the positive DC current of the four-terminal converter becomes -, +, +, +, and the negative DC current becomes 0. When a ground fault occurs at F7 or F18 of the receiving-end converter, taking the ground fault at the positive terminal of converter 2 as an example, the DC voltage imbalance protection (59 / 76DC) and ground overcurrent protection (76SG) of the four-terminal converter will both meet the protection criteria and operate, locking the four-terminal converter valve. When the DC high-speed switch HSS on the DC side is not disconnected, the capacitor discharge of the four-terminal converter causes the short-circuit current to be fed into the fault point. Since the fault points F7 and F18 are on the opposite side of the DC measurement point IDP at the fault end, the direction of the DC measurement point current at the fault end becomes negative, while the direction of the DC measurement point current at the non-fault end is positive. At this time, the direction of the positive DC current of the four-terminal converter becomes +, -, +, +, and the negative DC current becomes 0. When a ground fault occurs at point F9 in both the sending-end and receiving-end converters, the DC voltage imbalance protection (59 / 76DC) and ground overcurrent protection (76SG) of the four-terminal converter will both meet the protection criteria and operate, locking the four-terminal converter valve. When the DC high-speed switch HSS on the DC side is not disconnected, the capacitor discharge of the four-terminal converter causes the short-circuit current to be fed into the fault point. Since the fault point F9 is on the positive side of the DC measurement point IDP at the fault end, the positive DC current of the four-terminal converter is positive, and the negative DC current becomes 0.

[0092] It should be noted that, according to Figure 1 The topology was used to construct a simulation model in the electromagnetic transient simulation software of the power system. Ground faults were set at points F7 and F9 of converter 1, occurring after 5 seconds and lasting for 1 second. The waveforms of the positive DC current and protection action of the four-terminal converter after the fault are shown below. Figure 13 and Figure 14 As shown. By Figure 13It is known that a ground fault occurred at F7 of converter 1 at 5s. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter tripped; 11ms later, the ground overcurrent protection 76SG tripped; 20ms later, the four-terminal converter was locked; 50ms later, the AC circuit breaker opened; and 60ms later, the DC high-speed switch HSS opened. Between the lockout and tripping of the four-terminal converter, only the current direction at the positive DC measuring point of converter 1 at the fault end changed from positive to negative. Figure 14 It is known that a ground fault occurs at F9 of converter 1 at 5s. 10ms later, the DC voltage imbalance protection 59 / 76DC of the four-terminal converter operates, 11ms later, the ground overcurrent protection 76SG operates, 20ms later, the four-terminal converter is locked, 50ms later, the AC circuit breaker opens, and 60ms later, the DC high-speed switch HSS opens. After the four-terminal converter is locked but before tripping, the positive DC current of the four-terminal converter is positive. In this embodiment, the one-sender-end and three-receive-end operation mode is the same as the two-sender-end and two-receive-end operation mode. When a ground fault occurs at F7 or F18 of the converter, after the four-terminal converter is locked but before tripping, the fault current of the non-faulty end converter flows to the fault point through the positive DC measuring point current of the faulty end. Therefore, only the positive DC measuring point current of the faulty end is negative. When a ground fault occurs at F9 on the sending and receiving end converter, after the four-terminal converter is locked and before it trips, the fault current of the four-terminal converter flows to the fault point through the positive DC measuring point current of this end. Therefore, the positive DC measuring point current is in the positive direction.

[0093] In this embodiment, the DC area fault location method of the multi-terminal back-to-back flexible DC transmission system can effectively distinguish the fault location of the non-DC common area and the DC common area when the fault occurs at this end by adding fault feature criteria (such as the DC measuring point current direction change of the DC measuring point current direction after the four-terminal converter is locked and before the trip). This enables the implementation of effective fault isolation methods and restart strategies. It can also effectively identify the fault location of a certain DC unit in the non-DC common area and quickly isolate the fault.

[0094] In one embodiment of this application, the DC area fault location method of the multi-terminal back-to-back flexible DC transmission system further includes: S4. Determining a control execution strategy based on the fault location; the multi-terminal back-to-back flexible DC transmission system further includes an AC circuit breaker and a DC high-speed switch connected to each DC unit, and determining the control execution strategy based on the fault location includes:

[0095] If the fault location is in the DC common area, then all AC circuit breakers and all DC high-speed switches will be disconnected, and all DC units will stop operating.

[0096] If the fault location is in the non-DC common area of ​​a DC unit corresponding to the negative or positive DC measuring point current direction, then the DC high-speed switch connected to the faulty DC unit will be disconnected, other DC units will be restarted, the operating state of the DC high-speed switches connected to other DC units will remain unchanged, and the AC circuit breakers connected to other DC units will be closed.

[0097] It should be noted that, based on the located fault position in the DC area, differentiated control execution strategies are adopted to achieve fault isolation and rapid system recovery. Specifically: when a fault occurs in the DC common area, the fault point is located in the common connection area (such as the DC bus, common connection equipment, etc.) on the DC side of the multi-terminal back-to-back flexible DC transmission system; all AC circuit breakers and all DC high-speed switches are disconnected to completely isolate the electrical connection between the DC common area and the AC side and other DC units; all DC units (such as converters) are shut down to prevent the fault current from spreading to other healthy parts through the common area, avoid cascading reactions caused by the common area fault, and ensure the overall safe shutdown of the multi-terminal back-to-back flexible DC transmission system. When a fault occurs in a non-DC common area (within a specific DC unit), and the fault point is located in the non-common area of ​​a DC unit (such as inside a converter, a DC line section, etc.), the current direction of the positive DC measuring point is negative during the fault (i.e., the current flows from the DC unit to the common area, indicating that the fault current path is related to this DC unit); only the DC high-speed switch connected to the faulty DC unit is disconnected to cut off the connection between the faulty unit and the DC common area; other healthy DC units are immediately restarted to restore the operation of the non-faulty areas; the DC high-speed switches connected to other DC units maintain their original working state (such as closed or operating according to preset logic); the AC circuit breakers connected to other DC units remain closed to ensure the continuity of AC power supply; thus, while isolating the faulty DC unit, the operation of the healthy DC units is maintained to the maximum extent, improving the availability of this multi-terminal back-to-back flexible DC transmission system.

[0098] For example, the control execution strategy achieves graded response of protection actions through accurate fault location determination, taking into account both the safety and operational continuity of the multi-terminal back-to-back flexible DC transmission system, and demonstrating the intelligent fault handling capability of the multi-terminal back-to-back flexible DC transmission system.

[0099] Example 2:

[0100] Figure 15 This is a schematic diagram of the frame of the DC area fault location device for the multi-terminal back-to-back flexible DC transmission system described in the embodiments of this application.

[0101] like Figure 15As shown, this application embodiment provides a DC area fault location device for a multi-terminal back-to-back flexible DC transmission system, which is applied to the multi-terminal back-to-back flexible DC transmission system. The multi-terminal back-to-back flexible DC transmission system includes multiple DC units, and the DC area fault location device includes: a data acquisition module 10, a fault area determination module 20, and a fault location determination module 30.

[0102] Data acquisition module 10 is used to acquire information on the protection devices that have failed in the multi-terminal back-to-back flexible DC transmission system and the direction of the DC measuring point current.

[0103] The fault area determination module 20 is used to determine the fault area based on the protection device information;

[0104] The fault location determination module 30 is used to determine the fault location in the DC region based on the fact that the fault area is a single-pole grounding fault in the DC region and the direction of the DC measuring point current.

[0105] It should be noted that the content of the modules in the device of Embodiment 2 has already been described in the steps of the method of Embodiment 1. Therefore, the content of the modules in the DC area fault location device of the multi-terminal back-to-back flexible DC transmission system will not be repeated in this embodiment. In this embodiment, the DC area fault location device of the multi-terminal back-to-back flexible DC transmission system, through the data acquisition module, fault area determination module, and fault location determination module, can effectively distinguish the fault location of the non-DC common area and the DC common area when a fault occurs at this end, and implement effective fault isolation methods and restart strategies; it can also effectively identify the fault location of a certain DC unit in the non-DC common area and quickly isolate the fault.

[0106] In the embodiments of this application, the multi-terminal back-to-back flexible DC transmission system further includes an AC circuit breaker and a DC high-speed switch connected to each DC unit. The fault location determination module 30 is further configured to determine the fault location as follows: if the positive DC measuring point current direction of all DC units is positive, the fault location is in the positive DC common area; or if the negative DC measuring point current direction of all DC units is negative, the fault location is in the negative DC common area; if only one DC unit has a negative positive DC measuring point current direction... The fault location is the non-DC common area of ​​the DC unit corresponding to the negative direction of the positive DC measuring point current; or, based on the fact that only one DC unit has a positive negative DC measuring point current direction, the fault location is the non-DC common area of ​​the DC unit corresponding to the positive negative DC measuring point current direction. In the case of a fault in a multi-terminal back-to-back flexible DC transmission system, after the DC unit is locked out and before the AC circuit breaker and DC high-speed switch are opened, the positive or negative DC measuring point current direction of the DC unit is obtained as the DC measuring point current direction.

[0107] In one embodiment of this application, the DC area fault location device of the multi-terminal back-to-back flexible DC transmission system further includes an execution module 40, which is used to determine a control execution strategy based on the fault location.

[0108] In this embodiment, the execution module 40 is further configured to, if the fault location is in the DC common area, control all AC circuit breakers and all DC high-speed switches to open and all DC units to stop operating; if the fault location is in the non-DC common area of ​​a DC unit corresponding to a DC unit where the current direction of the positive DC measuring point is negative or the current direction of the negative DC measuring point is positive, control the DC high-speed switches connected to the faulty DC unit to open, control other DC units to restart, and maintain the operating state of the DC high-speed switches connected to other DC units unchanged and the AC circuit breakers connected to other DC units to close.

[0109] Example 3:

[0110] Figure 16 This is a schematic diagram of the terminal device described in an embodiment of this application.

[0111] like Figure 16 As shown, this application provides a terminal device, including a processor and a memory;

[0112] Memory is used to store program code and transfer the program code to the processor;

[0113] The processor is used to execute the above-mentioned DC area fault location method for multi-terminal back-to-back flexible DC transmission system according to the instructions in the program code.

[0114] It should be noted that the processor is used to execute the steps in the above-described embodiment of a DC area fault location method for a multi-terminal back-to-back flexible DC transmission system according to the instructions in the program code. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the above-described system / device embodiments.

[0115] For example, a computer program can be divided into one or more modules / units, one or more of which are stored in memory and executed by a processor to complete this application. One or more modules / units can be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in a terminal device.

[0116] Terminal devices can be computing devices such as desktop computers, laptops, handheld computers, and cloud servers. Terminal devices may include, but are not limited to, processors and memory. Those skilled in the art will understand that this does not constitute a limitation on the terminal device, which may include more or fewer components than illustrated, or combinations of certain components, or different components. For example, a terminal device may also include input / output devices, network access devices, buses, etc.

[0117] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor.

[0118] Memory can be an internal storage unit of a terminal device, such as a hard drive or RAM. Memory can also be an external storage device, such as a plug-in hard drive, SmartMedia Card (SMC), Secure Digital (SD) card, or Flash Card. Furthermore, memory can include both internal and external storage units. Memory is used to store computer programs and other programs and data required by the terminal device. Memory can also be used to temporarily store data that has been output or will be output.

[0119] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0120] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between apparatuses or units through some interfaces, and may be electrical, mechanical, or other forms.

[0121] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0122] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0123] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0124] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for locating DC area faults in a multi-terminal back-to-back flexible DC transmission system, applied to the multi-terminal back-to-back flexible DC transmission system, wherein the multi-terminal back-to-back flexible DC transmission system comprises multiple DC units, characterized in that... The DC region fault location method includes the following steps: Obtain information on the protection devices that have experienced faults and the direction of the DC measuring point current in the multi-terminal back-to-back flexible DC transmission system; Based on the information from the protection device, determine the fault area; If the fault area is a single-pole grounding fault in the DC area, the fault location in the DC area is determined according to the direction of the DC measuring point current.

2. The DC area fault location method for a multi-terminal back-to-back flexible DC transmission system according to claim 1, characterized in that, The multi-terminal back-to-back flexible DC transmission system also includes an AC circuit breaker and a DC high-speed switch connected to each DC unit. Determining the fault location in the DC region based on the direction of the DC measuring point current includes: If the positive DC measuring point current direction of all the DC units in the DC measuring point current direction is positive, then the fault location is the positive DC common area; if the negative DC measuring point current direction of all the DC units in the DC measuring point current direction is negative, then the fault location is the negative DC common area. If only one of the DC measuring point current directions of the DC unit has a negative positive DC measuring point current direction, then the fault location is the non-DC common area of ​​the DC unit corresponding to the negative positive DC measuring point current direction; if only one of the DC measuring point current directions of the DC unit has a positive negative DC measuring point current direction, then the fault location is the non-DC common area of ​​the DC unit corresponding to the positive negative DC measuring point current direction. In the event of a fault in the multi-terminal back-to-back flexible DC transmission system, after the DC unit is locked out and before the AC circuit breaker and the DC high-speed switch are disconnected, the direction of the positive DC measuring point current or the direction of the negative DC measuring point current of the DC unit is obtained as the direction of the DC measuring point current.

3. The DC area fault location method for a multi-terminal back-to-back flexible DC transmission system according to claim 1, characterized in that, Based on the information from the protection device, the fault area is determined to include: If the protection device information indicates that the DC voltage imbalance protection and grounding overcurrent protection of all the DC units operate simultaneously, then the fault area is a single-pole grounding fault in the DC area. If the protection device information indicates that the DC voltage imbalance protection of all DC units is not activated, then the fault area is a single-pole grounding fault in a non-DC area.

4. The DC area fault location method for a multi-terminal back-to-back flexible DC transmission system according to claim 1, characterized in that, Also includes: Based on the location of the fault, a control execution strategy is determined.

5. The DC area fault location method for a multi-terminal back-to-back flexible DC transmission system according to claim 4, characterized in that, The multi-terminal back-to-back flexible DC transmission system also includes an AC circuit breaker and a DC high-speed switch connected to each DC unit. The control execution strategy is determined based on the fault location, including: If the fault location is in the DC common area, then all AC circuit breakers and all DC high-speed switches are disconnected, and all DC units stop operating. If the fault location is in the non-DC common area of ​​the DC unit corresponding to the positive DC measuring point current direction being negative or the negative DC measuring point current direction being positive, then the DC high-speed switch connected to the faulty DC unit is disconnected, the other DC units are restarted, the working state of the DC high-speed switches connected to the other DC units remains unchanged, and the AC circuit breakers connected to the other DC units are closed.

6. A DC area fault location device for a multi-terminal back-to-back flexible DC transmission system, applied to the multi-terminal back-to-back flexible DC transmission system, the multi-terminal back-to-back flexible DC transmission system comprising multiple DC units, characterized in that, The DC area fault location device includes: a data acquisition module, a fault area determination module, and a fault location determination module; The data acquisition module is used to acquire information on the protection devices that have failed in the multi-terminal back-to-back flexible DC transmission system and the direction of the DC measuring point current. The fault area determination module is used to determine the fault area based on the protection device information; The fault location determination module is used to determine the fault location in the DC region based on the fact that the fault region is a single-pole grounding fault in the DC region and the direction of the DC measuring point current.

7. The DC area fault location device for a multi-terminal back-to-back flexible DC transmission system according to claim 6, characterized in that, The multi-terminal back-to-back flexible DC transmission system also includes an AC circuit breaker and a DC high-speed switch connected to each DC unit. The fault location determination module is further configured to determine the fault location as follows: if the positive DC measuring point current direction of all DC units is positive, the fault location is in the positive DC common area; if the negative DC measuring point current direction of all DC units is negative, the fault location is in the negative DC common area; or, if only one DC unit has a negative positive DC measuring point current direction, the fault location is... The location is defined as the non-DC common area of ​​the DC unit where the positive DC measuring point current direction is negative; if only one of the DC measuring point current directions has a positive negative DC measuring point current direction, then the fault location is defined as the non-DC common area of ​​the DC unit where the negative DC measuring point current direction is positive; wherein, when a fault occurs in the multi-terminal back-to-back flexible DC transmission system, after the DC unit is locked and before the AC circuit breaker and the DC high-speed switch are disconnected, the positive or negative DC measuring point current direction of the DC unit is obtained as the DC measuring point current direction.

8. The DC area fault location device for a multi-terminal back-to-back flexible DC transmission system according to claim 7, characterized in that, It also includes an execution module, which is used to determine a control execution strategy based on the fault location.

9. The DC area fault location device for a multi-terminal back-to-back flexible DC transmission system according to claim 8, characterized in that, The execution module is further configured to, based on the fault location being in the DC common area, control all AC circuit breakers and all DC high-speed switches to disconnect and all DC units to stop operating; or, based on the fault location being in the non-DC common area of ​​the DC unit corresponding to the DC unit where the positive DC measuring point current direction is negative or the negative DC measuring point current direction is positive, control the DC high-speed switch connected to the faulty DC unit to disconnect, control the other DC units to restart, and maintain the operating state of the DC high-speed switches connected to other DC units unchanged and the AC circuit breakers connected to other DC units to close.

10. A terminal device, characterized in that, Including the processor and memory; The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute, according to the instructions in the program code, the DC area fault location method for a multi-terminal back-to-back flexible DC transmission system as described in any one of claims 1-5.

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