A high-sensitivity flexible DC line internal and external fault identification method and system

Abstract

The present invention discloses a highly sensitive method and system for identifying in-zone and out-zone faults in flexible DC lines. The method comprises: measuring voltage sampling values ​​at a protection installation within a certain period of time after a fault occurs; calculating voltage sampling value differentials based on the voltage sampling values; calculating the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differentials from time t0 to the current time t, and a voltage differential auxiliary value with a threshold based on the voltage sampling value differentials; identifying in-zone faults and distinguishing in-zone faults from out-of-zone faults based on the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differentials from time t0 to the current time t, and the voltage differential auxiliary value with a threshold. Thus, the method can effectively distinguish in-zone and out-of-zone faults while taking into account sensitivity, reliability, and selectivity, and has high practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and more particularly to a method and system for identifying internal and external faults in a highly sensitive flexible direct current line. Background Art

[0002] Flexible DC transmission systems offer low harmonic content and flexible operating characteristics, offering significant advantages over conventional DC transmission systems in addressing grid connection issues related to weakly fed systems, multi-point interconnected operation, and renewable energy integration. However, their fault characteristics differ significantly from those of conventional DC grids, characterized by weak damping and low inertia. Consequently, the formation of flexible DC grids requires protection that is highly sensitive, reliable, rapid, and selective.

[0003] The primary protection systems commonly used in current flexible DC transmission projects often rely on traveling wave protection and differential undervoltage protection, which are based on conventional DC transmission line designs. These protections suffer from significant limitations in sensitivity and selectivity. The former suffers from poor interference immunity and can potentially malfunction in the event of an out-of-zone fault. Both also exhibit poor resistance to transition resistance, with the maximum detectable transition resistance typically below 100Ω in practical applications. Longitudinal differential protection is currently commonly used to identify high-resistance faults within the zone, but its operating time is often measured in seconds, far from meeting practical requirements. Summary of the Invention

[0004] The present invention provides a highly sensitive method and system for identifying faults inside and outside a flexible DC line zone, which solves the technical problem that the longitudinal differential protection principle is currently commonly used to identify high-resistance faults within the zone, but its action time is often in the order of seconds, which is far from meeting actual needs.

[0005] According to a first aspect of the present invention, a method for identifying faults inside and outside a high-sensitivity flexible DC line is provided, comprising:

[0006] Measure the voltage sampling value at the protection installation within a certain period of time after the fault;

[0007] Calculating a voltage sampling value difference based on the voltage sampling value;

[0008] Calculating, based on the voltage sampling value difference, the voltage sampling value difference accumulation amount, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage difference auxiliary amount with a threshold;

[0009] According to the voltage sampling value differential accumulation amount, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary amount with a threshold, the fault within the area is identified and the fault within the area and the fault outside the area are distinguished.

[0010] Optionally, measure the voltage sampling value at the protection installation within a certain period of time after the fault, including:

[0011] Determine the time t0 when the protection device detects the fault and the voltage sampling value of the pole and side measured at the protection installation at time t0 as U m (t0);

[0012] Determine the time auxiliary parameter x and measure the voltage sampling value U from time t0-x to the current time t m .

[0013] Optionally, calculating a voltage sampling value difference according to the voltage sampling value includes:

[0014] Determine a certain time t k The voltage sampling value difference ΔU m (t k ) is: ΔU m (t k )=U m (t k )-U m (t k -1);

[0015] Calculate the voltage sampling value difference ΔU from the moment t0-x+1 to the current moment t m .

[0016] Optionally, calculating the voltage sampling value difference accumulation amount according to the voltage sampling value difference includes:

[0017] According to the voltage sampling value difference, the voltage difference conventional accumulation amount at the current time t is calculated Sum of the absolute value of the voltage difference

[0018] Determine the voltage differential normal accumulation as:

[0019] Determine the voltage differential absolute value accumulation as:

[0020] Where c is the time.

[0021] Optionally, calculating the maximum value of the voltage sampling value difference from time t0 to the current time t based on the voltage sampling value difference includes:

[0022] According to the calculated ΔU m (t0)~ΔU m (t), calculate the maximum difference of the voltage sampling value according to the following formula:

[0023]

[0024] Optionally, calculating a voltage differential auxiliary amount with a threshold according to the voltage sampling value difference includes:

[0025] According to the voltage sampling value difference, calculate the time t k Voltage differential auxiliary quantity with threshold when Where a is a constant.

[0026] Voltage differential auxiliary quantity with threshold:

[0027] Optionally, identifying an in-zone fault based on the voltage sampling value differential accumulation amount, the maximum value of the voltage sampling value differential from time t0 to the current time t, and a voltage differential auxiliary amount with a threshold includes:

[0028] According to the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold, the fault identification criterion within the area is determined:

[0029]

[0030] Where C1 is an auxiliary parameter; ΔU set1 is the constant value of the conventional accumulation of voltage difference; when the above formula is satisfied, it is considered that an intra-zone fault has occurred.

[0031] Optionally, distinguishing between internal faults and external faults based on the voltage sampling value differential accumulation amount, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary amount with a threshold includes:

[0032] According to the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold, the fault identification and distinction criteria for inside and outside the zone are determined:

[0033]

[0034] Among them, k1 and k2 are auxiliary time parameters, ΔU set2 Sets the absolute value of the voltage differential accumulation.

[0035] According to another aspect of the present invention, a high-sensitivity flexible DC line internal and external fault identification system is provided, which is characterized by comprising:

[0036] The voltage sampling value measurement module is used to measure the voltage sampling value at the protection installation within a certain period of time after the fault;

[0037] A voltage sampling value difference calculation module is used to calculate the voltage sampling value difference according to the voltage sampling value;

[0038] A module for calculating difference-related parameters, configured to calculate, based on the voltage sampling value difference, the voltage sampling value difference accumulation amount, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage difference auxiliary amount with a threshold;

[0039] The module for distinguishing internal and external faults is used to identify internal faults and distinguish internal faults from external faults based on the accumulated differential amount of the voltage sampling values, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary amount with a threshold.

[0040] Optionally, the voltage sampling value measurement module includes:

[0041] Determine the local pole local side voltage sampling value submodule, the user determines the time t0 when the protection device detects the fault and the local pole local side voltage sampling value measured at the protection installation at time t0 as U m (t0);

[0042] Determine the voltage sampling value submodule, which is used to determine the time auxiliary parameter x and measure the voltage sampling value U from time t0-x to the current time t m .

[0043] Optionally, the voltage sampling value difference calculation module includes:

[0044] Determine the voltage sampling value difference at a certain moment submodule, used to determine the voltage sampling value difference at a certain moment t k The voltage sampling value difference ΔU m (t k ) is: ΔU m (t k )=U m (t k )-U m (t k -1);

[0045] The voltage sampling value obtaining submodule is used to obtain the voltage sampling value difference ΔU from the time t0-x+1 to the current time t m .

[0046] Optionally, a module for calculating differential related parameters includes:

[0047] The voltage differential accumulation quantum calculation module is used to calculate the voltage differential conventional accumulation quantity at the current time t according to the voltage sampling value difference Sum of the absolute value of the voltage difference

[0048] Determine the voltage differential normal accumulation quantum module, used to determine the voltage differential normal accumulation quantum is:

[0049] Determine the voltage differential absolute value accumulation as:

[0050] Where c is the time.

[0051] Optionally, a module for calculating differential related parameters includes:

[0052] The submodule for calculating the maximum difference of voltage sampling values ​​is used to calculate the ΔU m (t0)~ΔU m (t), calculate the maximum difference of the voltage sampling value according to the following formula:

[0053]

[0054] Optionally, a module for calculating differential related parameters includes:

[0055] The voltage differential auxiliary quantum module is used to calculate the voltage at a certain moment t according to the voltage sampling value difference. k Voltage differential auxiliary quantity with threshold when Where a is a constant.

[0056] Voltage differential auxiliary quantity with threshold:

[0057] Optionally, identifying a fault module within a zone includes:

[0058] The submodule for determining the criterion for identifying the fault within the zone is used to determine the criterion for identifying the fault within the zone based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold:

[0059]

[0060] Where C1 is an auxiliary parameter; ΔU set1 is the constant value of the conventional accumulation of voltage difference; when the above formula is satisfied, it is considered that an intra-zone fault has occurred.

[0061] Optionally, distinguishing between internal and external fault modules includes:

[0062] The submodule for determining the criterion for identifying and distinguishing faults within and outside the zone is used to determine the criterion for identifying and distinguishing faults within and outside the zone based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold:

[0063]

[0064] Among them, k1 and k2 are auxiliary time parameters, ΔU set2 Sets the absolute value of the voltage differential accumulation.

[0065] Therefore, a flexible DC line high-resistance and in-zone fault identification method based on voltage differential accumulation is constructed based on the differential accumulation of line voltage sampling values. This method can tolerate large transition resistance and is reliable and will not malfunction under various disturbances outside the zone. It can effectively distinguish in-zone and out-zone faults while taking into account sensitivity, reliability and selectivity, and has high practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0067] Figure 1 Schematic diagram of the flow of a method for identifying internal and external faults of a highly sensitive flexible DC line according to this embodiment;

[0068] Figure 2 Schematic diagram of the flexible DC transmission system described in this embodiment

[0069] Figure 3 This is a schematic diagram of the simulation results of the intra-zone high-resistance fault according to this embodiment;

[0070] Figure 4 Schematic diagram of the simulation result of the out-of-zone fault described in this embodiment;

[0071] Figure 5 This is the overall protection action logic diagram described in this embodiment;

[0072] Figure 6 Schematic diagram of a high-sensitivity flexible DC line internal and external fault identification system according to this embodiment. DETAILED DESCRIPTION

[0073] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a thorough and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments shown in the accompanying drawings is not intended to limit the present invention. In the accompanying drawings, identical elements are denoted by the same reference numerals.

[0074] Unless otherwise specified, the terms used herein (including technical terms) have the meanings commonly understood by those skilled in the art. In addition, it is understood that terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0075] According to a first aspect of the present invention, a method 100 for identifying internal and external faults in a high-sensitivity flexible DC line is provided. Figure 1 As shown, the method 100 includes:

[0076] S101: measuring the voltage sampling value at the protection installation within a certain period of time after the fault;

[0077] S102: Calculating a voltage sampling value difference based on the voltage sampling value;

[0078] S103: Calculating, based on the voltage sampling value difference, the voltage sampling value difference accumulation amount, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage difference auxiliary amount with a threshold;

[0079] S104: Identify faults in the area based on the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold.

[0080] , distinguish between faults within the area and faults outside the area.

[0081] Specifically, Figure 2 A simulation model of the flexible direct current transmission system is built, and the effectiveness of the method of the present invention is verified by using simulation waveforms when faults of different attributes occur at each fault point.

[0082] (1) Measure the voltage sampling value at the protection installation within a certain period of time after the fault.

[0083] Define t0 as the moment when the protection device detects a fault; the voltage sampling value of the pole and side measured at the protection installation at t0 is U m (t0). Define x as the time auxiliary parameter, and measure the voltage sampling value U from time t0-x to the current time t m .

[0084] (2) Calculate the voltage sampling value difference.

[0085] Define a time t k The voltage sampling value difference ΔU m (t k ) is: ΔU m (t k )=U m (t k )-U m (t k -1). Calculate the voltage sampling value difference ΔU from time t0-x+1 to the current time t m .

[0086] (3) Calculate the differential accumulation of voltage sampling values

[0087] Define and calculate the conventional accumulation of voltage difference at the current time t as follows: Sum of the absolute value of the voltage difference Where c is the time.

[0088] Voltage differential normal accumulation:

[0089] Voltage differential absolute value accumulation:

[0090] (4) Calculate the maximum value of the voltage sampling value difference from time t0 to the current time t

[0091] For the calculated ΔU m (t0)~ΔU m (t), calculate the maximum difference of the voltage sampling value according to the following formula:

[0092]

[0093] (5) Calculate the voltage differential auxiliary quantity with threshold

[0094] Define and calculate a certain time t as follows k Voltage differential auxiliary quantity with threshold when Where a is a constant.

[0095] Voltage differential auxiliary quantity with threshold:

[0096] (6) In-area fault identification

[0097] The fault identification criteria within the design area are as follows:

[0098]

[0099] Hereinafter, it is referred to as sub-criterion 1. Where C1 is an auxiliary parameter; ΔU set1 is the fixed value of the conventional accumulation of voltage differential. When the above equation is satisfied, an internal fault is considered to have occurred. Because the voltage differential accumulation is used as the comparison criterion, this criterion is insensitive to transition resistance and can identify high-resistance internal faults.

[0100] It's important to note that while transition resistance directly affects the magnitude of the fault transient excitation, it doesn't directly participate in the propagation of the traveling wave generated by the fault excitation along the line. In other words, transition resistance doesn't alter the fluctuation trend of the fault transient traveling wave. Therefore, when the fault transient traveling wave reaches the protection installation, the fluctuation trend of the measured electrical quantity is largely unaffected by transition resistance. Because this criterion uses the accumulated voltage differential, which reflects the fluctuation trend, as a comparison variable, it is insensitive to transition resistance and can identify high-resistance faults within the zone with high sensitivity.

[0101] (7) Identification and differentiation of faults inside and outside the area

[0102] The criteria for identifying and distinguishing faults inside and outside the design area are as follows:

[0103]

[0104] Hereinafter, it is referred to as sub-criterion 2. Where k1 and k2 are auxiliary time parameters, ΔU set2 is the fixed value of the voltage differential absolute value accumulation. When the above formula is satisfied, it is considered that an internal fault has occurred. Due to the difference in voltage drop characteristics when there is a fault inside and outside the zone, when there is a fault outside the zone, Often very small, making the criterion invalid; and when the fault occurs within the area is large, so that the judgment can be established.

[0105] When an internal fault occurs, the voltage always drops rapidly and dramatically before gradually recovering. When an external fault occurs, the voltage exhibits a prolonged, slow decline. Transition resistance does not alter these basic characteristics, so the voltage sampling differential is insensitive to transition resistance, and even high-resistance faults exhibit distinct fault characteristics. The voltage differential accumulation further highlights the fault characteristics by summing and averaging the voltage sampling differentials.

[0106] The protection action logic is to simultaneously meet the requirements of high-resistance fault identification and internal and external fault differentiation. The protection will be activated when any one of the criteria is met.

[0107] (8) When Figure 2 When a 500Ω high-resistance ground fault occurs at point F1 in the zone, the protection criterion waveform is as follows: Figure 3 As shown. If sub-criteria 1 is not satisfied, it means that a high-resistance fault within the zone or an external fault may have occurred; while sub-criteria 2 is satisfied, eliminating the possibility of an external fault. At this point, the fault is successfully identified as an internal fault, and the protection is reliably operated.

[0108] (9) When Figure 2 When a metallic ground fault occurs at point F2 outside the zone, the protection criterion waveform is as follows: Figure 4 As shown in Figure 1, failure of sub-criteria 1 indicates a possible intra-zone high-resistance fault or extra-zone fault. Failure of sub-criteria 2 eliminates the possibility of an intra-zone terminal high-resistance fault. The fault is thus identified as a forward extra-zone fault, and the protection system remains reliably inoperative.

[0109] The voltage differential accumulation further highlights the fault characteristics by summing and averaging the voltage sampling value differences. The protection action logic is to meet the requirements of high-resistance fault identification and internal and external fault differentiation at the same time. The protection will be activated when any of the criteria is met. The overall protection action logic diagram is shown in the attached figure. Figure 5 shown.

[0110] Therefore, a flexible DC line high-resistance and in-zone fault identification method based on voltage differential accumulation is constructed based on the differential accumulation of line voltage sampling values. This method can tolerate large transition resistance and is reliable and will not malfunction under various disturbances outside the zone. It can effectively distinguish in-zone and out-zone faults while taking into account sensitivity, reliability and selectivity, and has high practical value.

[0111] Optionally, measure the voltage sampling value at the protection installation within a certain period of time after the fault, including:

[0112] Determine the time t0 when the protection device detects the fault and the voltage sampling value of the pole and side measured at the protection installation at time t0 as U m (t0);

[0113] Determine the time auxiliary parameter x and measure the voltage sampling value U from time t0-x to the current time t m .

[0114] Optionally, calculating a voltage sampling value difference according to the voltage sampling value includes:

[0115] Determine a certain time t k The voltage sampling value difference ΔU m (t k ) is: ΔU m (t k )=U m (t k )-U m (t k -1);

[0116] Calculate the voltage sampling value difference ΔU from the moment t0-x+1 to the current moment t m .

[0117] Optionally, calculating the voltage sampling value difference accumulation amount according to the voltage sampling value difference includes:

[0118] According to the voltage sampling value difference, the voltage difference conventional accumulation amount at the current time t is calculated Sum of the absolute value of the voltage difference

[0119] Determine the voltage differential normal accumulation as:

[0120] Determine the voltage differential absolute value accumulation as:

[0121] Where c is the time.

[0122] Optionally, calculating the maximum value of the voltage sampling value difference from time t0 to the current time t based on the voltage sampling value difference includes:

[0123] According to the calculated ΔU m (t0)~ΔU m (t), calculate the maximum difference of the voltage sampling value according to the following formula:

[0124]

[0125] Optionally, calculating a voltage differential auxiliary amount with a threshold according to the voltage sampling value difference includes:

[0126] According to the voltage sampling value difference, calculate the time t k Voltage differential auxiliary quantity with threshold when Where a is a constant.

[0127] Voltage differential auxiliary quantity with threshold:

[0128] Optionally, identifying an in-zone fault based on the voltage sampling value differential accumulation amount, the maximum value of the voltage sampling value differential from time t0 to the current time t, and a voltage differential auxiliary amount with a threshold includes:

[0129] According to the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold, the fault identification criterion within the area is determined:

[0130]

[0131] Where C1 is an auxiliary parameter; ΔU set1 When the above equation is satisfied, it is considered that an intra-zone fault has occurred.

[0132] Optionally, distinguishing between internal faults and external faults based on the voltage sampling value differential accumulation amount, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary amount with a threshold includes:

[0133] According to the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold, the fault identification and distinction criteria for inside and outside the zone are determined:

[0134]

[0135] Among them, k1 and k2 are auxiliary time parameters, ΔU set2 Sets the absolute value of the voltage differential accumulation.

[0136] Therefore, a flexible DC line high-resistance and in-zone fault identification method based on voltage differential accumulation is constructed based on the differential accumulation of line voltage sampling values. This method can tolerate large transition resistance and is reliable and will not malfunction under various disturbances outside the zone. It can effectively distinguish in-zone and out-zone faults while taking into account sensitivity, reliability and selectivity, and has high practical value.

[0137] According to another aspect of the present invention, a highly sensitive flexible DC line internal and external fault identification system 600 is provided, comprising:

[0138] The voltage sampling value measuring module 610 is used to measure the voltage sampling value at the protection installation within a certain period of time after the fault;

[0139] A voltage sampling value difference calculation module 620 is configured to calculate a voltage sampling value difference based on the voltage sampling value;

[0140] a difference-related parameter calculation module 630 for calculating, based on the voltage sampling value difference, a voltage sampling value difference accumulation amount, a maximum value of the voltage sampling value difference from time t0 to the current time t, and a voltage difference auxiliary amount with a threshold;

[0141] An in-zone fault identification module 640 is configured to identify an in-zone fault based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and a voltage difference auxiliary value with a threshold;

[0142] The internal and external fault distinguishing module 650 is used to distinguish internal faults from external faults based on the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold.

[0143] Optionally, the voltage sampling value measuring module 610 includes:

[0144] Determine the local pole local side voltage sampling value submodule, the user determines the time t0 when the protection device detects the fault and the local pole local side voltage sampling value measured at the protection installation at time t0 as U m (t0);

[0145] Determine the voltage sampling value submodule, which is used to determine the time auxiliary parameter x and measure the voltage sampling value U from time t0-x to the current time t m .

[0146] Optionally, the voltage sampling value difference calculation module 620 includes:

[0147] Determine the voltage sampling value difference at a certain moment submodule, used to determine the voltage sampling value difference at a certain moment t k The voltage sampling value difference ΔU m (tk ) is: ΔU m (t k )=U m (t k )-U m (t k -1);

[0148] The voltage sampling value obtaining submodule is used to obtain the voltage sampling value difference ΔU from the time t0-x+1 to the current time t m .

[0149] Optionally, the differential related parameter calculation module 630 includes:

[0150] The voltage differential accumulation quantum calculation module is used to calculate the voltage differential conventional accumulation quantity at the current time t according to the voltage sampling value difference Sum of the absolute value of the voltage difference

[0151] Determine the voltage differential normal accumulation quantum module, used to determine the voltage differential normal accumulation quantum is:

[0152] Determine the voltage differential absolute value accumulation as:

[0153] Where c is the time.

[0154] Optionally, the differential related parameter calculation module 630 includes:

[0155] The submodule for calculating the maximum difference of voltage sampling values ​​is used to calculate the ΔU m (t0)~ΔU m (t), calculate the maximum difference of the voltage sampling value according to the following formula:

[0156]

[0157] Optionally, the differential related parameter calculation module 630 includes:

[0158] The voltage differential auxiliary quantum module is used to calculate the voltage at a certain moment t according to the voltage sampling value difference. k Voltage differential auxiliary quantity with threshold when Where a is a constant.

[0159] Voltage differential auxiliary quantity with threshold:

[0160] Optionally, the intra-zone fault identification module 640 includes:

[0161] The submodule for determining the criterion for identifying the fault within the zone is used to determine the criterion for identifying the fault within the zone based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold:

[0162]

[0163] Where C1 is an auxiliary parameter; ΔU set1 is the constant value of the conventional accumulation of voltage difference; when the above formula is satisfied, it is considered that an intra-zone fault has occurred.

[0164] Optionally, the internal and external fault distinguishing module 650 includes:

[0165] The submodule for determining the criterion for identifying and distinguishing faults within and outside the zone is used to determine the criterion for identifying and distinguishing faults within and outside the zone based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold:

[0166]

[0167] Among them, k1 and k2 are auxiliary time parameters, ΔU set2 The constant value of the voltage differential absolute value accumulation;.

[0168] A high-sensitivity flexible DC line internal and external fault identification system 600 of an embodiment of the present invention corresponds to a high-sensitivity flexible DC line internal and external fault identification method 100 of another embodiment of the present invention, and will not be described in detail here.

[0169] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the application can adopt 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.) that contain computer-usable program code. The scheme in the embodiment of the present application can be implemented in various computer languages, for example, object-oriented programming language Java and literal translation scripting language JavaScript, etc.

[0170] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0171] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0172] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0173] Although the preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0174] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. Thus, if these modifications and variations of this application fall within the scope of the claims of this application and their equivalents, this application is intended to include these modifications and variations.

Claims

1. A high-sensitivity method for identifying faults inside and outside a flexible DC line, characterized in that: include: Measure the voltage sampling value at the protection installation within a certain period of time after the fault; Calculating a voltage sampling value difference based on the voltage sampling value; Calculating, based on the voltage sampling value difference, the voltage sampling value difference accumulation amount, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage difference auxiliary amount with a threshold; Identify faults within the zone and distinguish between faults within the zone and faults outside the zone based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold; Calculating the voltage sampling value difference accumulation amount according to the voltage sampling value difference includes: According to the voltage sampling value difference, the voltage difference conventional accumulation amount at the current time t is calculated Sum of the absolute value of the voltage difference Determine the voltage differential normal accumulation as: Determine the voltage differential absolute value accumulation as: Among them, c is the moment, and x is the auxiliary parameter for determining the time; Calculating a voltage differential auxiliary quantity with a threshold according to the voltage sampling value difference includes: According to the voltage sampling value difference, calculate the time t k Voltage differential auxiliary quantity with threshold when Where a is a constant value, Voltage differential auxiliary quantity with threshold: According to the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold, the fault identification criterion within the area is determined: Where C1 is an auxiliary parameter; ΔU set1 is the constant value of the conventional accumulation of voltage difference. When the above formula is satisfied, it is considered that an intra-zone fault has occurred.

2. The method according to claim 1, characterized in that Measure the voltage sampling value at the protection installation within a certain period of time after the fault, including: Determine the time t0 when the protection device detects the fault and the voltage sampling value of the pole and side measured at the protection installation at time t0 as U m (t0); Determine the time auxiliary parameter x and measure the voltage sampling value U from time t0-x to the current time t m .

3. The method according to claim 1, characterized in that Calculating a voltage sampling value difference according to the voltage sampling value includes: Determine a certain time t k The voltage sampling value difference ΔU m (t k ) is: ΔU m (t k )=U m (t k )-U m (t k -1); Calculate the voltage sampling value difference ΔU from the moment t0-x+1 to the current moment t m .

4. The method according to claim 1, wherein Calculating the maximum value of the voltage sampling value difference from time t0 to the current time t based on the voltage sampling value difference includes: According to the calculated ΔU m (t0)~ΔU m (t), calculate the maximum difference of the voltage sampling value according to the following formula:

5. The method according to claim 1, characterized in that Distinguishing between internal and external faults according to the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold includes: According to the voltage sampling value differential accumulation, the maximum value of the voltage sampling value differential from time t0 to the current time t, and the voltage differential auxiliary value with a threshold, the fault identification and distinction criteria for inside and outside the zone are determined: Among them, k1 and k2 are auxiliary time parameters, ΔU set2 Sets the absolute value of the voltage differential accumulation.

6. A high-sensitivity flexible DC line internal and external fault identification system, characterized by: include: The voltage sampling value measurement module is used to measure the voltage sampling value at the protection installation within a certain period of time after the fault; A voltage sampling value difference calculation module is used to calculate the voltage sampling value difference according to the voltage sampling value; A module for calculating difference-related parameters, configured to calculate, based on the voltage sampling value difference, the voltage sampling value difference accumulation amount, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage difference auxiliary amount with a threshold; A module for distinguishing internal and external faults is used to identify internal faults and distinguish internal faults from external faults based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold; Module for calculating differential related parameters, including: The voltage differential accumulation quantum calculation module is used to calculate the voltage differential conventional accumulation quantity at the current time t according to the voltage sampling value difference Sum of the absolute value of the voltage difference Determine the voltage differential normal accumulation as: Determine the voltage differential absolute value accumulation as: Among them, c is the moment, and x is the auxiliary parameter for determining the time; Module for calculating differential related parameters, including: The voltage differential auxiliary quantum module is used to calculate the voltage at a certain moment t according to the voltage sampling value difference. k Voltage differential auxiliary quantity with threshold when Where a is a constant value, Voltage differential auxiliary quantity with threshold: Distinguish between internal and external fault modules, including: The submodule for determining the criterion for identifying the fault within the zone is used to determine the criterion for identifying the fault within the zone based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold: Where C1 is an auxiliary parameter; ΔU set1 is the constant value of the conventional accumulation of voltage difference. When the above formula is satisfied, it is considered that an intra-zone fault has occurred.

7. The system according to claim 6, characterized in that The voltage sampling value measurement module includes: The submodule for determining the voltage sampling value of the local pole and local side is used to determine the time t0 when the protection device detects the fault and the voltage sampling value of the local pole and local side measured at the protection installation at time t0 as U m (t0); Determine the voltage sampling value submodule, which is used to determine the time auxiliary parameter x and measure the voltage sampling value U from time t0-x to the current time t m .

8. The system according to claim 6, wherein: The voltage sampling value difference calculation module includes: Determine the voltage sampling value difference at a certain moment submodule, used to determine the voltage sampling value difference at a certain moment t k The voltage sampling value difference ΔU m (t k ) is: ΔU m (t k )=U m (t k )-U m (t k -1); The voltage sampling value obtaining submodule is used to obtain the voltage sampling value difference ΔU from the time t0-x+1 to the current time t m .

9. The system according to claim 6, wherein: The module for calculating differential related parameters also includes: The submodule for calculating the maximum difference of voltage sampling values ​​is used to calculate the ΔU m (t0)~ΔU m (t), calculate the maximum difference of the voltage sampling value according to the following formula:

10. The system according to claim 6, wherein: The module for distinguishing internal and external faults also includes: The submodule for determining the criterion for identifying and distinguishing faults within and outside the zone is used to determine the criterion for identifying and distinguishing faults within and outside the zone based on the accumulated voltage sampling value difference, the maximum value of the voltage sampling value difference from time t0 to the current time t, and the voltage differential auxiliary value with a threshold: Among them, k1 and k2 are auxiliary time parameters, ΔU set2 Sets the absolute value of the voltage differential accumulation.

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