Fault identification method, device and computer equipment for direct current transmission line

Abstract

This application relates to a fault identification method, apparatus, computer equipment, storage medium, and computer program product for DC transmission lines, belonging to the field of smart grid technology. The method includes: acquiring fault information of the positive and negative poles of the DC transmission line to be identified; when a fault occurs in the target line, collecting voltage and current data at both ends of the target line; the target line includes at least one of the positive and negative poles; performing low-pass filtering on the voltage and current data respectively, then obtaining the average differential current of the target line based on the filtered current data, and obtaining the average distributed capacitance current of the target line based on the filtered voltage data; determining the faulty area of ​​the target line based on the ratio between the average differential current and the average distributed capacitance current. This method can improve the speed of fault identification.

Description

Technical Field

[0001] This application relates to the field of smart grid technology, and in particular to a fault identification method, apparatus, computer equipment, storage medium and computer program product for DC transmission lines. Background Technology

[0002] Currently, DC transmission systems are widely used for long-distance, high-capacity power transmission. Traditional high-voltage DC transmission systems use grid-commutated converters, which place high demands on the strength of the AC system and are prone to commutation failure. Flexible DC transmission systems use voltage source converters, offering advantages such as flexible control and zero commutation failure, making them an important direction for the development of DC transmission technology.

[0003] However, most DC transmission lines are overhead lines, resulting in a high probability of fault occurrence and a rapid rise rate of fault current. Therefore, DC line fault identification, as a key technology in DC transmission, has received widespread attention. Currently, while current differential fault identification can effectively identify high-resistance faults, the speed of fault identification and subsequent fault protection using this method is poor. Furthermore, multi-terminal flexible DC transmission systems have a mesh structure, with multiple converter stations feeding fault current to the fault point through the mesh lines. The fault current rises rapidly, and flexible DC transmission systems use IGBTs (Insulated Gate Bipolar Transistors) for power conversion. However, IGBTs have poor current-carrying capacity, increasing the requirements for the speed of fault identification in multi-terminal flexible DC transmission systems. Summary of the Invention

[0004] Therefore, it is necessary to provide a method, apparatus, computer equipment, computer-readable storage medium, and computer program product for fault identification of DC transmission lines to address DC technology issues.

[0005] Firstly, this application provides a fault identification method for DC transmission lines. The method includes:

[0006] Obtain the fault information of the positive and negative lines in the DC transmission line to be identified;

[0007] For a target line in the positive line and the negative line, in the event of a fault in the target line, voltage data and current data at both ends of the target line are collected respectively; the target line includes at least one of the positive line and the negative line.

[0008] The voltage data and the current data are respectively subjected to low-pass filtering to obtain filtered voltage data and filtered current data;

[0009] Based on the filtered current data, the average differential current of the target line is obtained, and based on the filtered voltage data, the average distributed capacitance current of the target line is obtained.

[0010] Obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and determine the area where the target line has a fault based on the ratio.

[0011] In one embodiment, obtaining the fault status of the positive and negative lines in the DC transmission line to be identified includes:

[0012] For the target line in the positive line and the negative line, obtain the voltage traveling wave change of the target line and obtain the voltage traveling wave change threshold.

[0013] When the voltage traveling wave change of the target line exceeds the voltage traveling wave change threshold, it is determined that the target line has a fault.

[0014] In one embodiment, obtaining the voltage traveling wave change threshold includes:

[0015] Obtain the rated line voltage and voltage variation coefficient corresponding to the target line;

[0016] The product of the rated line voltage and the voltage variation coefficient is used as the threshold for the voltage traveling wave variation.

[0017] In one embodiment, the low-pass filtering of the voltage data and the current data includes:

[0018] Obtain the voltage drop coefficient, transition resistance, and line capacitance corresponding to the target line;

[0019] The low-pass cutoff frequency of the low-pass filter is determined based on the voltage drop coefficient, the transition resistance, and the line capacitance.

[0020] Based on the low-pass cutoff frequency, the voltage data and the current data are respectively subjected to low-pass filtering.

[0021] In one embodiment, the filtered current data includes multiple sets of filtered current data, each set of filtered current data containing filtered current data from both ends of the target line at the same time.

[0022] The step of obtaining the average differential current of the target line based on the filtered current data includes:

[0023] Based on each set of filtered current data, determine the differential current of the target line at the corresponding time of each set of filtered current data;

[0024] The average differential current of the target line is determined based on the differential current corresponding to each set of filtered current data.

[0025] In one embodiment, the filtered voltage data includes multiple sets of filtered voltage data, each set of filtered voltage data containing filtered voltage data at both ends of the target line at the same time.

[0026] The step of obtaining the average distributed capacitance current of the target line based on the filtered voltage data includes:

[0027] Based on each set of filtered voltage data, determine the voltage difference between the two ends of the target line at the corresponding time of each set of filtered voltage data;

[0028] Obtain the time interval between the line capacitance corresponding to the target line and the corresponding time of two adjacent sets of filtered voltage data;

[0029] The average distributed capacitance current of the target line is obtained based on the line capacitance, the time interval, and the voltage difference between the two ends corresponding to each set of filtered voltage data.

[0030] In one embodiment, determining the area where the target line is faulty based on the ratio includes:

[0031] Obtain the line protection setting value of the target line;

[0032] When the ratio is greater than the line protection setting value, a fault is determined to occur within the target line's fault zone.

[0033] When the ratio is less than or equal to the line protection setting value, it is determined that the target line has experienced an out-of-area fault.

[0034] Secondly, this application also provides a fault identification device for DC transmission lines. The device includes:

[0035] The fault acquisition module is used to acquire the fault status of the positive and negative lines in the DC transmission line to be identified.

[0036] The data acquisition module is used to collect voltage and current data at both ends of the target line in the case of a fault in the target line, for the positive line and the negative line respectively; the target line includes at least one of the positive line and the negative line.

[0037] The filtering module is used to perform low-pass filtering on the voltage data and the current data respectively to obtain filtered voltage data and filtered current data.

[0038] The data calculation module is used to obtain the average differential current of the target line based on the filtered current data, and to obtain the average distributed capacitance current of the target line based on the filtered voltage data.

[0039] The region determination module is used to obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and to determine the region where the target line has a fault based on the ratio.

[0040] Thirdly, this application also provides a computer device. The computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program to perform the following steps:

[0041] Obtain the fault information of the positive and negative lines in the DC transmission line to be identified;

[0042] For a target line in the positive line and the negative line, in the event of a fault in the target line, voltage data and current data at both ends of the target line are collected respectively; the target line includes at least one of the positive line and the negative line.

[0043] The voltage data and the current data are respectively subjected to low-pass filtering to obtain filtered voltage data and filtered current data;

[0044] Based on the filtered current data, the average differential current of the target line is obtained, and based on the filtered voltage data, the average distributed capacitance current of the target line is obtained.

[0045] Obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and determine the area where the target line has a fault based on the ratio.

[0046] Fourthly, this application also provides a computer-readable storage medium. The computer-readable storage medium stores a computer program thereon, which, when executed by a processor, performs the following steps:

[0047] Obtain the fault information of the positive and negative lines in the DC transmission line to be identified;

[0048] For a target line in the positive line and the negative line, in the event of a fault in the target line, voltage data and current data at both ends of the target line are collected respectively; the target line includes at least one of the positive line and the negative line.

[0049] The voltage data and the current data are respectively subjected to low-pass filtering to obtain filtered voltage data and filtered current data;

[0050] Based on the filtered current data, the average differential current of the target line is obtained, and based on the filtered voltage data, the average distributed capacitance current of the target line is obtained.

[0051] Obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and determine the area where the target line has a fault based on the ratio.

[0052] Fifthly, this application also provides a computer program product. The computer program product includes a computer program that, when executed by a processor, performs the following steps:

[0053] Obtain the fault information of the positive and negative lines in the DC transmission line to be identified;

[0054] For a target line in the positive line and the negative line, in the event of a fault in the target line, voltage data and current data at both ends of the target line are collected respectively; the target line includes at least one of the positive line and the negative line.

[0055] The voltage data and the current data are respectively subjected to low-pass filtering to obtain filtered voltage data and filtered current data;

[0056] Based on the filtered current data, the average differential current of the target line is obtained, and based on the filtered voltage data, the average distributed capacitance current of the target line is obtained.

[0057] Obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and determine the area where the target line has a fault based on the ratio.

[0058] The aforementioned fault identification method, apparatus, computer equipment, storage medium, and computer program product for DC transmission lines first acquire the fault information of the positive and negative lines in the DC transmission line to be identified. For the target line among the positive and negative lines, when a fault occurs in the target line, voltage and current data at both ends of the target line are collected respectively. The target line includes at least one of the positive and negative lines. Then, the voltage and current data are subjected to low-pass filtering to obtain filtered voltage and current data. By performing low-pass filtering on the voltage and current data, transient high-frequency interference can be filtered out, improving the sensitivity and accuracy of fault identification. Next, based on the filtered current data, the average differential current of the target line is obtained, and based on the filtered voltage data, the average distributed capacitance current of the target line is obtained. Using these average values ​​to construct the fault identification criterion provides better noise immunity. Finally, the ratio between the average differential current and the average distributed capacitance current is obtained. Based on this ratio, the faulty area of ​​the target line is determined. Identifying the faulty area in the line using the ratio between the average differential current and the average distributed capacitance current improves the speed of fault identification and reduces the influence of transition resistance, thereby increasing the sensitivity of fault identification and enabling more timely protection of the faulty line. The above-described fault identification method for DC transmission lines, using the ratio between the average differential current and the average distributed capacitance current as the fault identification criterion, features simple criterion setting, requires no simulation, improves the speed of fault identification, and reduces the influence of transition resistance, thus enhancing the sensitivity of fault identification. Attached Figure Description

[0059] Figure 1 This is a flowchart illustrating a fault identification method for a DC transmission line in one embodiment;

[0060] Figure 2 This is a complete flowchart of a fault identification method for DC transmission lines in another embodiment;

[0061] Figure 3 This is a schematic diagram of the DC transmission line to be identified in one embodiment;

[0062] Figure 4 This is a structural block diagram of a fault identification device for a DC transmission line in one embodiment;

[0063] Figure 5 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0065] In one embodiment, such as Figure 1 As shown, a fault identification method for DC transmission lines is provided. This embodiment illustrates the application of this method to a terminal. It is understood that this method can also be applied to a server, and further to a system including both a terminal and a server, and implemented through interaction between the terminal and the server. In this embodiment, the method includes the following steps:

[0066] Step S101: Obtain the fault status of the positive and negative lines in the DC transmission line to be identified.

[0067] For example, for the DC transmission line to be identified, the parameters corresponding to the positive and negative lines are obtained. Based on these parameters and the corresponding judgment criteria, it is determined whether the positive and negative lines have faults. If a fault occurs, the next step is to determine the fault area in the positive or negative line where the fault occurred.

[0068] Step S102: For the target line in the positive and negative lines, in the event of a fault in the target line, collect the voltage and current data at both ends of the target line respectively; the target line includes at least one of the positive and negative lines.

[0069] For example, after determining that a fault has occurred in the target line in step S101, multiple sets of current data and voltage data at both ends of the target line are collected at a preset sampling frequency. Each set of current data is the current at the beginning and end of the target line at the same time. Similarly, each set of voltage data is the voltage at the beginning and end of the target line at the same time.

[0070] Step S103: Perform low-pass filtering on the voltage data and current data respectively to obtain filtered voltage data and filtered current data.

[0071] For example, the line parameters in the line are obtained, the cutoff frequency of the low-pass filter is determined based on the line parameters, and the voltage data and current data are low-pass filtered according to the cutoff frequency to eliminate high-frequency transient interference that may be caused by components such as switches.

[0072] Step S104: Based on the filtered current data, obtain the average differential current of the target line, and based on the filtered voltage data, obtain the average distributed capacitance current of the target line.

[0073] For example, differential current is the current difference between the two ends of a transmission line. Under normal circumstances, the differential current at both ends of the transmission line should be zero because the magnitude and direction of the current at both ends should be equal, which is one of the basic characteristics of a DC transmission line. However, when a fault occurs in the line, such as a ground fault or insulation damage between conductors, the currents at both ends of the line will no longer be equal, thus generating differential current. Based on the filtered current data, the differential current corresponding to each set of current data is calculated, and then the average value of the differential current is calculated. Distributed capacitance current refers to the current in a DC transmission line caused by the capacitance between the two conductors. In a DC transmission line, because the capacitance between the two conductors is relatively large, a distributed capacitance current is generated when the voltage across the line changes. The magnitude of this current depends on the rate of voltage change and the capacitance between the two conductors. Distributed capacitance current is usually very small, but in some cases, such as when a line fault occurs or there are operational changes, the change in distributed capacitance current may become relatively large. Based on the sampling time interval between each group of voltage data and the filtered voltage data, the distributed capacitance current corresponding to each group of voltage data is calculated, and then the average value of the distributed capacitance current is calculated.

[0074] Step S105: Obtain the ratio between the average differential current and the average distributed capacitance current, and determine the area where the target line has a fault based on the ratio.

[0075] For example, the ratio between the average differential current and the average distributed capacitance current, along with the corresponding fault judgment threshold, is obtained. When the ratio exceeds the judgment threshold, it is determined that an intra-zone fault has occurred on the target line, thus requiring line protection processing. When the ratio does not exceed the judgment threshold, it is determined that an extra-zone fault has occurred on the target line, and no line protection processing is required.

[0076] In the above-mentioned fault identification method for DC transmission lines, firstly, the fault status of the positive and negative lines in the DC transmission line to be identified is obtained. For the target line in the positive and negative lines, when the target line has a fault, the voltage and current data at both ends of the target line are collected respectively. The target line includes at least one of the positive and negative lines. Then, the voltage and current data are low-pass filtered to obtain filtered voltage and current data. By performing low-pass filtering on the voltage and current data, transient high-frequency interference can be filtered out, improving the sensitivity and accuracy of fault identification. Next, based on the filtered current data, the average differential current of the target line is obtained, and based on the filtered voltage data, the average distributed capacitance current of the target line is obtained. Using these average values ​​to extract the fault identification criterion provides better noise immunity. Finally, the ratio between the average differential current and the average distributed capacitance current is obtained. Based on this ratio, the faulty area of ​​the target line is determined. Identifying the faulty area in the line using the ratio between the average differential current and the average distributed capacitance current improves the speed of fault identification and reduces the influence of transition resistance, thereby increasing the sensitivity of fault identification and enabling more timely protection of the faulty line. The above-described fault identification method for DC transmission lines, using the ratio between the average differential current and the average distributed capacitance current as the fault identification criterion, features simple criterion setting, requires no simulation, improves the speed of fault identification, and reduces the influence of transition resistance, thus enhancing the sensitivity of fault identification.

[0077] In one embodiment, step S101 of obtaining the fault status of the positive and negative lines in the DC transmission line to be identified specifically includes: for the target line in the positive and negative lines, obtaining the voltage traveling wave change amount of the target line and obtaining the voltage traveling wave change amount threshold; when the voltage traveling wave change amount of the target line exceeds the voltage traveling wave change amount threshold, it is determined that the target line has a fault.

[0078] For example, voltage traveling wave refers to an electromagnetic wave signal that propagates along a DC transmission line when the voltage changes due to the line's capacitance and inductance, similar to a "sound wave" in a DC transmission line. When a fault occurs in a DC transmission line, it causes a change in the voltage traveling wave. The change in voltage traveling wave is the change in the voltage traveling wave of a DC transmission line over a time series, and the voltage traveling wave of a DC transmission line needs to be collected on the DC transmission line itself.

[0079] Furthermore, in one embodiment, the above-mentioned acquisition of the voltage traveling wave change threshold specifically includes: acquiring the rated line voltage and voltage change coefficient corresponding to the target line; and using the product of the rated line voltage and the voltage change coefficient as the voltage traveling wave change threshold.

[0080] For example, the fault condition of a DC transmission line can be determined using the following formula:

[0081] |ΔU|>ΔU set =k0U ref

[0082] Where ΔU represents the voltage traveling wave change, ΔU set U is used as a criterion for determining fault conditions. ref denoted as the rated line voltage of the target line, and k0 as the voltage variation coefficient.

[0083] In this embodiment, the detection of DC transmission line faults can be achieved by monitoring and analyzing the voltage traveling wave variation.

[0084] In one embodiment, step S103 above performs low-pass filtering on voltage data and current data respectively, specifically including: obtaining the voltage drop coefficient, transition resistance and line capacitance corresponding to the target line; determining the low-pass cutoff frequency of the low-pass filtering based on the voltage drop coefficient, transition resistance and line capacitance; and performing low-pass filtering on voltage data and current data respectively based on the low-pass cutoff frequency.

[0085] For example, the cutoff frequency of a low-pass filter can be determined by the following formula:

[0086]

[0087] Where, ω c k is the cutoff angular frequency of the low-pass filter. v R is the voltage drop coefficient. f C0 is the transition resistance, C0 is the line capacitance per unit length, and L is the line length of the target line. C0L is the line capacitance of the target line.

[0088] This embodiment provides a method for calculating the low-pass filter cutoff frequency, which facilitates subsequent low-pass filtering of voltage and current data, thereby improving the sensitivity and accuracy of fault identification.

[0089] In one embodiment, the filtered current data includes multiple sets of filtered current data, each set of filtered current data containing filtered current data from both ends of the target line at the same time; step S104 above obtains the average differential current of the target line based on the filtered current data, specifically including: determining the differential current of the target line at the time corresponding to each set of filtered current data based on each set of filtered current data; and determining the average differential current of the target line based on the differential current corresponding to each set of filtered current data.

[0090] For example, the average differential current can be calculated using the following formula:

[0091]

[0092] Among them, i 12, Let i1 and i2 represent the current data at both ends of the target line, i1 and i2 represent the current data at both ends of the target line, j represent the j-th data group, and N represent the number of data groups.

[0093] In this embodiment, the fault identification criterion is extracted by calculating the average value of the differential current, which makes the criterion more resistant to interference and thus improves the reliability of the fault identification results.

[0094] In one embodiment, the filtered voltage data includes multiple sets of filtered voltage data, each set containing filtered voltage data at both ends of the target line at the same time. Step S104 above, based on the filtered voltage data, obtains the average distributed capacitance current of the target line, specifically including: determining the voltage difference between the two ends of the target line at the corresponding time of each set of filtered voltage data; obtaining the line capacitance corresponding to the target line and the time interval between the corresponding times of two adjacent sets of filtered voltage data; and obtaining the average distributed capacitance current of the target line based on the line capacitance, the time interval, and the voltage difference between the two ends corresponding to each set of filtered voltage data.

[0095] For example, the distributed capacitance current at the corresponding time point for each set of voltage data can be calculated using the following formula:

[0096]

[0097] The average value of the distributed capacitance current is:

[0098]

[0099] Among them, i c i represents the distributed capacitance current of the target line at the corresponding time point of each set of voltage data. c,aveThe value represents the average distributed capacitance current of the target line, u1 and u2 represent the voltage data at both ends of the target line, C0 is the line capacitance per unit length, L is the line length of the target line, Δt is the time interval between the corresponding times of the two sets of voltage data, j represents the j-th set of data, because the distributed capacitance current needs to depend on the voltage data of the previous set, so the value of j starts from 2; N represents the number of sets of voltage data.

[0100] In this embodiment, the fault identification criterion is extracted by calculating the average value of the distributed capacitance current, which makes the criterion more resistant to interference and thus improves the reliability of the fault identification result.

[0101] In one embodiment, step S105, which determines the area where the target line has a fault based on the ratio, specifically includes: obtaining the line protection setting value of the target line; determining that the target line has a fault within the fault zone when the ratio is greater than the line protection setting value; and determining that the target line has a fault outside the fault zone when the ratio is less than or equal to the line protection setting value.

[0102] For example, the line protection setting value k set It can be calculated using the following formula:

[0103] k set =k rel *1

[0104] Where, k rel This represents the reliability coefficient, with a value ranging from 1.2 to 2.0.

[0105] Furthermore, fault selection can be achieved by identifying the fault regions in the positive and negative lines:

[0106] If k ave,p >k set ,k ave,q ≤k set If k is positive, then it is a positive electrode fault; if k ave,p ≤k set ,k ave,q >k set If k is negative, then it is a negative electrode fault; ave,p >k set ,k ave,q >k set If the above conditions are not met, it is an inter-pole (two-stage) fault; if none of the above conditions are met, it is a two-stage out-of-range fault. Where k ave,p k represents the ratio of the average differential current to the average distributed capacitance current in the positive circuit. ave,q It represents the ratio of the average differential current to the average distributed capacitance current of the negative line.

[0107] Furthermore, if a fault occurs in the positive line, the line protection for the positive line will be activated; if a fault occurs in the negative line, the line protection for the negative line will be activated.

[0108] In this embodiment, by comparing the ratio of the average differential current and the average distributed capacitance current of the target line with the line protection setting value, the area where the target line has a fault is determined, and then the line protection is activated to ensure the safe operation of the line.

[0109] In another embodiment, such as Figure 2 As shown, a fault identification method for DC transmission lines is provided, including the following steps:

[0110] Step S201: For the target line in the DC transmission line to be identified, obtain the voltage traveling wave change of the target line. The target line includes at least one of the positive and negative lines in the transmission line to be identified.

[0111] Step S202: Obtain the rated line voltage and voltage variation coefficient corresponding to the target line; use the product of the rated line voltage and voltage variation coefficient as the voltage traveling wave change threshold.

[0112] Step S203: When the voltage traveling wave change of the target line exceeds the voltage traveling wave change threshold, it is determined that the target line has a fault, and the voltage data and current data at both ends of the target line are collected respectively.

[0113] Step S204: Obtain the voltage drop coefficient, transition resistance, and line capacitance corresponding to the target line. Based on the voltage drop coefficient, transition resistance, and line capacitance, determine the low-pass cutoff frequency for low-pass filtering.

[0114] Step S205: Based on the low-pass cutoff frequency, perform low-pass filtering on the voltage data and current data respectively to obtain filtered voltage data and filtered current data.

[0115] Step S206: Based on each set of filtered current data, determine the differential current of the target line at the corresponding time of each set of filtered current data.

[0116] Step S207: Determine the average differential current of the target line based on the differential current corresponding to each group of filtered current data.

[0117] Step S208: Based on each set of filtered voltage data, determine the voltage difference between the two ends of the target line at the corresponding time of each set of filtered voltage data.

[0118] Step S209: Obtain the line capacitance corresponding to the target line and the time interval between the corresponding times of two adjacent sets of filtered voltage data.

[0119] Step S210: Based on the line capacitance, time interval, and voltage difference between the two ends corresponding to each group of filtered voltage data, the average value of the distributed capacitance current of the target line is obtained.

[0120] Step S211: Obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and obtain the line protection setting value of the target line.

[0121] In step S212, if the ratio is greater than the line protection setting value, it is determined that the target line has a fault within the zone; if the ratio is less than or equal to the line protection setting value, it is determined that the target line has a fault outside the zone.

[0122] To facilitate understanding of the embodiments of this application by those skilled in the art, the following will be described in conjunction with the appendix. Figure 3 Specific examples illustrate this application; among them, Figure 3This is a multi-terminal flexible DC transmission system. It should be noted that currently, most DC transmission lines are overhead lines, with a high probability of fault occurrence and a large fault current rise rate. Therefore, DC line fault protection, as a key technology in DC transmission, has received widespread attention. Line fault protection methods based on the DC line voltage change rate lack sensitivity under high transition resistance; while line fault protection methods based on traveling waves, although improving the ability to withstand transition resistance, often rely on boundary elements. When the value of the current-limiting reactor is small and the attenuation of high-frequency electrical quantities traveling waves is weak, the expected protection effect may not be achieved. To ensure that the line fault protection scheme can reliably identify faults under high-resistance faults and guarantee the safe operation of the line, current differential fault protection is often used as a backup protection method in existing practical projects. Current differential fault protection can effectively identify high-resistance faults, but in long-distance transmission lines, the influence of distributed capacitance is significant. Under faults outside the protection zone, the differential current is easily affected by the distributed capacitance current and exceeds the setting value, causing protection maloperation. Therefore, current differential fault protection often needs to use protection delays to avoid the transient process of distributed capacitance discharge, thus reducing the speed of fault protection. Meanwhile, multi-terminal flexible DC transmission systems are mostly mesh structures, with multiple converter stations feeding fault current to the fault point through mesh lines. The rise rate of the fault current is relatively fast. Furthermore, flexible DC transmission systems use IGBTs for power conversion, and IGBTs have relatively poor current-carrying capacity, which undoubtedly increases the requirements for the speed of line fault protection in multi-terminal flexible DC transmission systems. Further, for flexible DC transmission systems, the selectivity of protection is crucial; that is, after a fault occurs on a line, the circuit breakers on both sides must be able to accurately disconnect the faulty line to ensure the stability of the entire system. For longitudinal protection schemes, if one end misidentifies the fault zone, identifying an internal fault as an external one, it will lead to erroneous failure to execute protection, failing to disconnect the faulty line, causing the system to be in an overcurrent state for a long time, damaging power electronic equipment. If an external fault is identified as an internal fault, healthy lines will be mistakenly disconnected, preventing normal power transmission.

[0123] In this example, with Figure 3 Line 1 in the diagram is used as the DC transmission line to be identified.

[0124] In this example, the converter in a multi-terminal flexible DC transmission system— Figure 3 The main parameters of the MMC (Modular Multilevel Converter) are shown in Table 1.

[0125] Table 1 Main Parameters of Converter Station

[0126] Converter station 1 2 3 4 Rated capacity / MVA 600 300 800 1000 Valve-side AC bus voltage / kV 220 220 220 220 DC voltage / kV 400 400 400 400 Number of submodules in a single bridge arm 200 200 200 200 Submodule rated voltage / kV 1.6 1.6 1.6 1.6 Submodule capacitance value / mF 10 10 10 10 Bridge arm reactance / mH 29 116 29 19

[0127] Table 2 shows the parameters and their values ​​used in the fault identification method in this example.

[0128] Table 2 Fault Identification Parameter Values

[0129] parameter <![CDATA[k0]]> <![CDATA[ΔU set ]]> L <![CDATA[k v ]]> <![CDATA[C0]]> <![CDATA[R f ]]> <![CDATA[k rel ]]> <![CDATA[k set ]]> Value 0.08 30 500km 0.9 <![CDATA[0.72*10 -11 F / m]]> 600Ω 1.8 1.8

[0130] Table 3 shows the fault identification results of the positive line of Line 1 under different conditions in this example.

[0131] Table 3 Fault identification results of the positive line of Line 1

[0132]

[0133] Furthermore, such as Figure 3 As shown, f1 and f3 are the locations of faults outside the zone, and f2 is the location of faults inside the zone.

[0134] In this embodiment, the ratio of the sum of differential current and distributed capacitance current is used as the criterion, which can weaken the influence of transition resistance on the criterion and improve the sensitivity of the protection. Furthermore, the protection criterion setting is simple, requiring no electromagnetic transient simulation, and inherently possesses fault polarity selection capabilities. Extracting fault identification features through average value makes the protection more reliable, eliminates the need for strict data synchronization, and has strong noise interference resistance. In addition, this solution is applicable not only to multi-terminal flexible DC transmission lines but also to traditional high-voltage DC transmission lines or hybrid multi-terminal DC transmission lines, effectively and accurately identifying faults to ensure the safe operation of the entire DC transmission system.

[0135] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0136] Based on the same inventive concept, this application also provides a fault identification device for DC transmission lines to implement the fault identification method for DC transmission lines described above. The solution provided by this device is similar to the solution described in the above method. Therefore, the specific limitations of one or more embodiments of the fault identification device for DC transmission lines provided below can be found in the limitations of the fault identification method for DC transmission lines described above, and will not be repeated here.

[0137] In one embodiment, such as Figure 4 As shown, a fault identification device for DC transmission lines is provided, comprising: a fault acquisition module 401, a data acquisition module 402, a filtering module 403, a data calculation module 404, and a region determination module 405, wherein:

[0138] The fault acquisition module 401 is used to acquire the fault status of the positive and negative lines in the DC transmission line to be identified.

[0139] The data acquisition module 402 is used to collect voltage and current data at both ends of a target line in the case of a fault in the target line, which is either a positive line or a negative line.

[0140] The filtering module 403 is used to perform low-pass filtering on the voltage data and the current data respectively to obtain the filtered voltage data and the filtered current data.

[0141] The data calculation module 404 is used to obtain the average differential current of the target line based on the filtered current data, and to obtain the average distributed capacitance current of the target line based on the filtered voltage data.

[0142] The area determination module 405 is used to obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and to determine the area where the target line has a fault based on the ratio.

[0143] In one embodiment, the fault acquisition module 401 is further configured to acquire the voltage traveling wave change of the target line in the positive and negative lines, and acquire the voltage traveling wave change threshold; when the voltage traveling wave change of the target line exceeds the voltage traveling wave change threshold, it is determined that a fault has occurred in the target line.

[0144] In one embodiment, the fault acquisition module 401 is further configured to acquire the rated line voltage and voltage variation coefficient corresponding to the target line; and use the product of the rated line voltage and voltage variation coefficient as the voltage traveling wave change threshold.

[0145] In one embodiment, the filtering module 403 is further configured to obtain the voltage drop coefficient, transition resistance, and line capacitance corresponding to the target line; determine the low-pass cutoff frequency for low-pass filtering based on the voltage drop coefficient, transition resistance, and line capacitance; and perform low-pass filtering on the voltage data and current data respectively based on the low-pass cutoff frequency.

[0146] In one embodiment, the filtered current data includes multiple sets of filtered current data, each set of filtered current data containing filtered current data at both ends of the target line at the same time. The data calculation module 404 is further configured to determine the differential current of the target line at the time corresponding to each set of filtered current data based on each set of filtered current data; and to determine the average value of the differential current of the target line based on the differential current corresponding to each set of filtered current data.

[0147] In one embodiment, the filtered voltage data includes multiple sets of filtered voltage data, each set containing filtered voltage data at both ends of the target line at the same time. The data calculation module 404 is further configured to determine the voltage difference between the two ends of the target line at the corresponding time of each set of filtered voltage data based on each set of filtered voltage data; obtain the line capacitance corresponding to the target line and the time interval between the corresponding times of two adjacent sets of filtered voltage data; and obtain the average value of the distributed capacitance current of the target line based on the line capacitance, the time interval, and the voltage difference between the two ends corresponding to each set of filtered voltage data.

[0148] In one embodiment, the aforementioned region determination module 405 is further configured to obtain the line protection setting value of the target line; if the ratio is greater than the line protection setting value, it is determined that the target line has an in-zone fault; if the ratio is less than or equal to the line protection setting value, it is determined that the target line has an out-of-zone fault.

[0149] Each module in the aforementioned fault identification device for DC transmission lines can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device, or stored in the memory of a computer device as software, so that the processor can call and execute the corresponding operations of each module.

[0150] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 5As shown, the computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores line parameters and fault identification parameters of the DC transmission line to be identified. The I / O interfaces are used for information exchange between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When the computer program is executed by the processor, it implements a fault identification method for DC transmission lines.

[0151] Those skilled in the art will understand that Figure 5 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0152] In one embodiment, a computer device is also provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to implement the steps in the above method embodiments.

[0153] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon that, when executed by a processor, implements the steps in the above method embodiments.

[0154] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0155] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data shall comply with the relevant laws, regulations and standards of the relevant countries and regions.

[0156] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0157] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0158] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A fault identification method for DC transmission lines, characterized in that, The method includes: Obtain the fault information of the positive and negative lines in the DC transmission line to be identified; For a target line in the positive line and the negative line, in the event of a fault in the target line, voltage data and current data at both ends of the target line are collected respectively; the target line includes at least one of the positive line and the negative line. Obtain the voltage drop coefficient, transition resistance, and line capacitance corresponding to the target line; determine the low-pass cutoff frequency for low-pass filtering based on the voltage drop coefficient, transition resistance, and line capacitance; perform low-pass filtering on the voltage data and current data respectively based on the low-pass cutoff frequency to obtain filtered voltage data and filtered current data; the filtered voltage data includes multiple sets of filtered voltage data, each set containing filtered voltage data at both ends of the target line at the same time; the range of the low-pass cutoff frequency is determined by the following formula: in, The low-pass cutoff frequency is... The voltage drop coefficient is mentioned above. The transition resistance, Let L be the capacitance per unit length of the line, and L be the length of the target line. The line capacitance of the target line; Based on the filtered current data, the average differential current of the target line is obtained, and based on each set of filtered voltage data, the voltage difference between the two ends of the target line at the corresponding time of each set of filtered voltage data is determined; the line capacitance corresponding to the target line and the time interval between the corresponding times of two adjacent sets of filtered voltage data are obtained; based on the line capacitance, the time interval, and the voltage difference between the two ends of each set of filtered voltage data, the average distributed capacitance current of the target line is obtained; the distributed capacitance current at the corresponding time of each set of filtered voltage data is calculated using the following formula: in, For each group of filtered data, the first... The distributed capacitance current corresponding to the group voltage data at that time. The time interval is... and These represent the voltage data at both ends of the target line, respectively. The ratio between the average value of the differential current and the average value of the distributed capacitance current is obtained to obtain the line protection setting value of the target line; when the ratio is greater than the line protection setting value, the fault in the target line is determined to be within the fault zone; when the ratio is less than or equal to the line protection setting value, the fault in the target line is determined to be outside the fault zone.

2. The method according to claim 1, characterized in that, The process of obtaining fault information for the positive and negative poles of the DC transmission line to be identified includes: For the target line in the positive line and the negative line, obtain the voltage traveling wave change of the target line and obtain the voltage traveling wave change threshold. When the voltage traveling wave change of the target line exceeds the voltage traveling wave change threshold, it is determined that the target line has a fault.

3. The method according to claim 2, characterized in that, The step of obtaining the voltage traveling wave change threshold includes: Obtain the rated line voltage and voltage variation coefficient corresponding to the target line; The product of the rated line voltage and the voltage variation coefficient is used as the threshold for the voltage traveling wave variation.

4. The method according to claim 1, characterized in that, The filtered current data includes multiple sets of filtered current data, and each set of filtered current data contains the filtered current data at both ends of the target line at the same time. The step of obtaining the average differential current of the target line based on the filtered current data includes: Based on each set of filtered current data, determine the differential current of the target line at the corresponding time of each set of filtered current data; The average differential current of the target line is determined based on the differential current corresponding to each set of filtered current data.

5. A fault identification device for a DC transmission line, characterized in that, The device includes: The fault acquisition module is used to acquire the fault status of the positive and negative lines in the DC transmission line to be identified. The data acquisition module is used to collect voltage and current data at both ends of the target line in the case of a fault in the target line, for the positive line and the negative line respectively; the target line includes at least one of the positive line and the negative line. A filtering module is used to obtain the voltage drop coefficient, transition resistance, and line capacitance corresponding to the target line; determine the low-pass cutoff frequency for low-pass filtering based on the voltage drop coefficient, transition resistance, and line capacitance; perform low-pass filtering on the voltage data and current data respectively based on the low-pass cutoff frequency to obtain filtered voltage data and filtered current data; the filtered voltage data includes multiple sets of filtered voltage data, each set containing filtered voltage data at both ends of the target line at the same time; the range of the low-pass cutoff frequency is determined by the following formula: in, The low-pass cutoff frequency is... The voltage drop coefficient is mentioned above. The transition resistance, Let L be the capacitance per unit length of the line, and L be the length of the target line. The line capacitance of the target line; The data calculation module is used to obtain the average differential current of the target line based on the filtered current data, and to determine the voltage difference between the two ends of the target line at the corresponding time of each set of filtered voltage data based on each set of filtered voltage data; to obtain the line capacitance corresponding to the target line and the time interval between the corresponding times of two adjacent sets of filtered voltage data; and to obtain the average distributed capacitance current of the target line based on the line capacitance, the time interval, and the voltage difference between the two ends of each set of filtered voltage data. The distributed capacitance current at the corresponding time of each set of filtered voltage data is calculated using the following formula: in, For each group of filtered data, the first... The distributed capacitance current corresponding to the group voltage data at that time. The time interval is... and These represent the voltage data at both ends of the target line, respectively. The region determination module is used to obtain the ratio between the average value of the differential current and the average value of the distributed capacitance current, and to obtain the line protection setting value of the target line; when the ratio is greater than the line protection setting value, the target line is determined to have a fault within the region; when the ratio is less than or equal to the line protection setting value, the target line is determined to have a fault outside the region.

6. The apparatus according to claim 5, characterized in that, The fault acquisition module is also used to acquire the voltage traveling wave change of the target line in the positive line and the negative line, and to acquire the voltage traveling wave change threshold. When the voltage traveling wave change of the target line exceeds the voltage traveling wave change threshold, it is determined that the target line has a fault.

7. The apparatus according to claim 6, characterized in that, The fault acquisition module is further configured to acquire the rated line voltage and voltage variation coefficient corresponding to the target line; and to use the product of the rated line voltage and the voltage variation coefficient as the voltage traveling wave change threshold.

8. The apparatus according to claim 5, characterized in that, The data calculation module is further configured to determine the differential current of the target line at the corresponding time of each set of filtered current data based on each set of filtered current data; and to determine the average differential current of the target line based on the differential current corresponding to each set of filtered current data.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 4.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 4.

11. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 4.

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