Pole selection method, system, equipment and medium for single-pole grounding fault in DC distribution network

Abstract

The present invention discloses a method, system, device, and medium for selecting a single-pole ground fault in a DC distribution network. The method includes: determining whether a line fault has occurred based on the zero-mode voltage of the line in the DC distribution network to be selected; when a line fault is determined, collecting the positive and negative currents at the beginning and end of the line, and performing linear fitting on the positive and negative currents to obtain the fitted intercepts of the positive beginning current, the positive end current, the negative beginning current, and the negative end current; and performing fault pole selection based on the fitted intercepts of the positive beginning current, the positive end current, the negative beginning current, and the negative end current to obtain the fault pole. The present invention solves the problem that the prior art cannot accurately and reliably determine the fault pole.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current (DC) distribution networks, and in particular to a method, system, device and medium for selecting a pole for a single-pole grounding fault in a DC distribution network. Background Art

[0002] In recent years, with the rapid development of power electronics technology, large-capacity and high-proportion distributed power sources (DGs) have been connected to the grid. DC distribution networks can directly use DGs to power electric vehicle charging stations, data centers, ship power supplies, smart homes, and other applications, reducing losses during energy conversion and significantly increasing the ability to absorb renewable energy. The IT grounding system (the "I" in the IT grounding system indicates that the power supply end (the converter side) is not directly grounded or is grounded through a high impedance; the "T" indicates that the exposed conductive parts of the electrical equipment (such as the metal casing) are independently grounded) is the mainstream safety solution for DC distribution networks. In the event of a single-pole ground fault, the sudden change in fault current is minimal, allowing the system to continue supplying power despite the fault, thereby maintaining a high degree of power continuity.

[0003] However, when a single-pole ground fault occurs in an IT-grounded low-voltage DC power supply system, the fault current varies little compared to the normal operating current, making it difficult to detect the fault and complete fault pole selection in a timely manner, resulting in increased losses at the unisolated fault point. Prolonged operation with the fault may cause multiple ground faults, which in severe cases may deteriorate into a short-circuit fault, causing a sharp increase in fault current and making it impossible to maintain normal power supply. Furthermore, the DC distribution network based on VSCs (voltage source converters) can be damaged by overcurrent due to their low damping and low inertia. Traditional methods typically rely on current fluctuations or voltage fluctuations alone to determine the fault location, but these methods cannot accurately determine the fault section and fault pole, especially in complex distribution networks. Furthermore, many traditional fault detection methods require manual intervention, such as manual inspection of current or voltage data, which increases the risk of human error.

[0004] Therefore, for single-pole grounding faults in low-voltage DC distribution networks with IT wiring, timely and accurate fault pole selection is particularly important. Summary of the Invention

[0005] The present invention provides a method, system, device and medium for selecting a pole for a single-pole grounding fault in a DC distribution network, which are used to solve the problem that the prior art cannot accurately and reliably determine the fault pole.

[0006] In view of this, a first aspect of the present invention provides a method for selecting a pole for a single-pole grounding fault in a DC power distribution network, the method comprising:

[0007] Determine whether a line fault occurs according to the zero-mode voltage of the line in the DC distribution network of the selected pole;

[0008] When a line fault is determined, the positive and negative currents at the beginning and end of the line are collected, and a straight line fitting is performed on the positive and negative currents respectively to obtain the fitting intercept of the positive beginning current, the fitting intercept of the positive end current, the fitting intercept of the negative beginning current, and the fitting intercept of the negative end current;

[0009] A fault pole is selected based on the fitting intercept of the positive electrode first-end current, the fitting intercept of the positive electrode terminal current, the fitting intercept of the negative electrode first-end current, and the fitting intercept of the negative electrode terminal current to obtain a fault pole.

[0010] Optionally, the determining whether a line fault occurs by detecting the line zero mode voltage in the DC distribution network of the to-be-selected pole includes:

[0011] The positive and negative voltages at the head end of a line in a DC distribution network to be selected are detected in real time, the line zero-mode voltage is calculated based on the positive and negative voltages, and whether a line fault occurs is determined based on the line zero-mode voltage.

[0012] Optionally, calculating the line zero-mode voltage according to the positive electrode voltage and the negative electrode voltage includes:

[0013] Substituting the positive electrode voltage and the negative electrode voltage into a calculation formula of the line zero mode voltage to calculate the line zero mode voltage;

[0014] Among them, the calculation formula of the line zero mode voltage is:

[0015] ;

[0016] Where, and are the positive electrode voltage and the negative electrode voltage at the head end of the line respectively; is the line zero mode voltage.

[0017] Optionally, determining whether a line fault occurs according to the line zero mode voltage includes:

[0018] When the line zero-mode voltage is greater than a preset zero-mode voltage start-up setting value, it is determined that a line fault occurs.

[0019] Optionally, the positive and negative currents at the beginning and end of the acquisition circuit include:

[0020] The positive and negative currents at the beginning and end of the line are collected through the feeder terminal units, wherein the feeder terminal units are respectively arranged at the beginning and end of the line.

[0021] Optionally, performing straight-line fitting on the positive and negative electrode currents includes:

[0022] Fit the positive and negative electrode currents based on the fitting formula and calculate the fitting intercept;

[0023] Wherein, the expression of the fitting formula is:

[0024] ;

[0025] Where, is the fitting slope; is the fitting intercept; N is the total number of pole current sampling points, , , , ; is the pole current for straight line fitting; is the corresponding time series, and n is the pole current sampling point.

[0026] Optionally, the performing fault pole selection based on the fitted intercept of the positive electrode head-end current, the fitted intercept of the positive electrode terminal current, the fitted intercept of the negative electrode head-end current, and the fitted intercept of the negative electrode terminal current to obtain the fault pole includes:

[0027] S31, determining whether the signs of the fitted intercept of the positive electrode head-end current and the fitted intercept of the positive electrode terminal current, as well as the signs of the fitted intercept of the negative electrode head-end current and the fitted intercept of the negative electrode terminal current are the same; if they are the same, determining that there is no fault in the line pole; otherwise, executing step S32;

[0028] S32, calculating the fitted intercept difference based on the fitted intercept difference calculation formula;

[0029] Wherein, the expression of the fitting intercept difference calculation formula is:

[0030] ;

[0031] Where, is the fitted intercept difference, is the difference in the fitted intercept of the positive or negative pole of line i, is the fitted intercept of the current at the positive or negative end of line i, is the fitted intercept of the current at the positive or negative terminal of line i;

[0032] S33: The positive electrode or negative electrode of the line corresponding to the item with the largest fitting intercept difference is defined as the fault electrode of the faulty line.

[0033] A second aspect of the present invention provides a single-pole grounding fault pole selection system for a DC power distribution network, the system comprising:

[0034] a judgment unit, configured to judge whether a line fault occurs according to the zero-mode voltage of the line in the DC distribution network of the selected pole;

[0035] A fitting unit is used to collect the positive and negative currents at the beginning and end of the line after determining that a line fault has occurred, and perform linear fitting on the positive and negative currents respectively to obtain the fitting intercept of the positive beginning current, the fitting intercept of the positive end current, the fitting intercept of the negative beginning current, and the fitting intercept of the negative end current of the line;

[0036] The pole selection unit is used to perform fault pole selection based on the fitting intercept of the positive pole head end current, the fitting intercept of the positive pole terminal current, the fitting intercept of the negative pole head end current and the fitting intercept of the negative pole terminal current to obtain the fault pole.

[0037] A third aspect of the present invention provides a device for selecting a single-pole ground fault in a DC distribution network, the device comprising a processor and a memory:

[0038] The memory is used to store program code and transmit the program code to the processor;

[0039] The processor is configured to execute the steps of the method for selecting a pole for a single-pole grounding fault in a DC distribution network as described in the first aspect according to the instructions in the program code.

[0040] A fourth aspect of the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium is used to store program code, and the program code is used to execute the method described in the first aspect.

[0041] It can be seen from the above technical solutions that the present invention has the following advantages:

[0042] The present invention provides a method for selecting a pole for a single-pole ground fault in a DC distribution network. The method first determines whether a line fault has occurred based on the zero-mode voltage of the line in the DC distribution network at the pole to be selected. Next, when a line fault occurs, a linear fit is performed on the decaying portion of the post-fault pole current to determine the fitting intercept. Finally, the faulty pole is selected based on the fitting intercept. By detecting the direction of the double-terminal same-pole current mutation and performing a linear fit on the decaying portion of the current, the present invention can more accurately determine the faulty section and pole, avoiding the possibility of misjudgment. Furthermore, the present invention implements automated calculation and fault diagnosis, reducing human intervention, lowering manual errors, and improving the accuracy and reliability of fault diagnosis. This method thus addresses the problem of prior art inability to accurately and reliably determine the faulty pole. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 A flow chart of a method for selecting a pole for a single-pole grounding fault in a DC distribution network provided by an embodiment of the present invention;

[0045] Figure 2 Schematic diagram of a 400V low-voltage DC distribution network provided in an embodiment of the present invention;

[0046] Figure 3 A schematic structural diagram of a single-pole grounding fault pole selection system for a DC distribution network provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0047] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0048] See also Figure 1 , a method for selecting a pole for a single-pole grounding fault in a DC distribution network provided in an embodiment of the present invention includes:

[0049] Step 101: Determine whether a line fault occurs based on the zero-mode voltage of the line in the DC distribution network of the selected pole.

[0050] In one embodiment, step 101 includes:

[0051] The positive and negative voltages at the head end of the line in the DC distribution network to be selected are detected in real time, the line zero-mode voltage is calculated based on the positive and negative voltages, and whether the line is faulty is determined based on the line zero-mode voltage.

[0052] like Figure 2As shown in the figure, in specific applications, feeder terminal units (FTUs) are installed in each section of the distribution line. FTUs are key equipment in power system automation, responsible for monitoring and controlling the distribution network. They communicate with substations, circuit breakers, and other equipment to monitor current, voltage, and switch status in real time, and support remote control and fault diagnosis. Signal measurement and communication are performed by FTUs at both ends of the line. For example, FTU1 and FTU12 jointly collect the positive and negative currents of Line 1.

[0053] It should be noted that the present invention first detects the positive voltage and negative voltage of the line head end in the DC distribution network to be selected in real time through the feeder terminal unit; then substitutes the positive voltage and negative voltage into the calculation formula of the line zero mode voltage to calculate the line zero mode voltage;

[0054] Among them, the calculation formula of the line zero mode voltage is:

[0055] ; (1)

[0056] Where, and are the positive electrode voltage and the negative electrode voltage at the head end of the line respectively; is the line zero mode voltage.

[0057] Finally, it is determined whether the line zero-mode voltage is greater than the preset zero-mode voltage start setting value. When the line zero-mode voltage is greater than the preset zero-mode voltage start setting value, it is determined that a line fault has occurred. If no fault has occurred, the positive and negative voltages at the head end of the line in the DC distribution network to be selected are continued to be detected in real time through the feeder terminal unit.

[0058] The judgment formula is as follows:

[0059] ; (2)

[0060] Where, It is the setting value for zero mode voltage startup.

[0061] It is understood that this step accurately determines whether a line fault has occurred by detecting the positive and negative voltages at the line headend in real time, calculating the line zero-mode voltage based on these voltage values, and comparing this zero-mode voltage with a preset zero-mode voltage startup setting value. The present invention can promptly detect whether a line fault has occurred in a DC distribution network.

[0062] Step 102: When it is determined that a line fault occurs, the positive and negative currents at the beginning and end of the line are collected, and straight line fitting is performed on the positive and negative currents respectively to obtain the fitting intercept of the positive beginning current of the line, the fitting intercept of the positive end current, the fitting intercept of the negative beginning current, and the fitting intercept of the negative end current of the line.

[0063] In one embodiment, step 102 includes:

[0064] When a line fault is determined, the positive and negative currents at the beginning and end of the line are collected through the feeder terminal unit, where the feeder terminal unit is set at the beginning and end of the line respectively; then the positive and negative currents are fitted based on the fitting formula to obtain the fitting intercept.

[0065] It should be noted that the feeder terminal unit in this step can be found in Figure 2 , and refer to the description of the feeder terminal unit in step 101.

[0066] It should be noted that after determining that a line fault has occurred, the positive and negative currents at both ends of each line are collected through the FTU at both ends of each section of the line, and a straight line fitting is performed on the double-end currents after the fault. The straight line fitting steps are as follows:

[0067] Setting up the objective function , ask for When taking the minimum value 、 parameter.

[0068] Specifically, first calculate according to formula (3) Parameters and Then set it to zero to get Equation (3), and solve this equation to get Equation (4).

[0069] (3)

[0070] (4)

[0071] Where, To perform linear fitting of the pole current, set the sampling rate to 100kHz, collect the pole currents of the positive and negative poles at the beginning and end of each line from 0.0001s to 0.0005s after the fault, perform linear fitting on each, and obtain the corresponding fitting slope; n represents the nth sampling point; N is the total number of sampling points; is the corresponding time series; , , , ; is the fitting slope; is the fitted intercept.

[0072] Finally, let the fitted intercept of the current at the positive terminal of line i be , the fitted intercept of the positive terminal current of line i is , the fitted intercept of the current at the negative terminal of line i is , the fitted intercept of the negative terminal current of line i is .

[0073] Step 103 : performing fault pole selection based on the fitted intercept of the positive electrode head-end current, the fitted intercept of the positive electrode terminal current, the fitted intercept of the negative electrode head-end current, and the fitted intercept of the negative electrode terminal current to obtain the fault pole.

[0074] In one embodiment, step 103 includes:

[0075] Step 1031: Determine whether the signs of the fitting intercept of the positive pole head-end current and the fitting intercept of the positive pole terminal current, as well as the signs of the fitting intercept of the negative pole head-end current and the fitting intercept of the negative pole terminal current are the same; if they are the same, determine that there is no fault in the line; otherwise, execute step 1032.

[0076] It should be noted that, according to the fitted intercepts of the positive and negative beginning and end currents of each line obtained in step 102, the and 、 and Are the signs the same? If the signs are the same, it means that there is no fault on the line. If the signs are opposite, execute step 1032.

[0077] Step 1032: Calculate the fitted intercept difference based on the fitted intercept difference calculation formula.

[0078] Among them, the expression for calculating the fitting intercept difference is:

[0079] ;

[0080] Where, is the fitted intercept difference, is the difference in the fitted intercept of the positive or negative electrode of line i.

[0081] Step 1033: The positive electrode or negative electrode of the line corresponding to the item with the largest fitting intercept difference is defined as the fault electrode of the faulty line.

[0082] It should be noted that the positive or negative pole of the line corresponding to the item with the largest intercept difference is determined to be the fault pole of the fault line. The positive electrode of line 2 is judged to be faulty.

[0083] It can be understood that if the signs of the fitted intercepts of the same-pole current at the head end and the end end are the same, it is determined that no fault has occurred in the pole line; if the signs of the fitted intercepts are opposite, the difference between the fitted intercepts at the head end and the end end is taken, and there may be multiple sets of results. It is necessary to take the one with the largest absolute value of the intercept difference among all the calculation results. The line corresponding to this result is the fault pole.

[0084] The present invention provides a method for selecting a pole for a single-pole ground fault in a DC distribution network. The method first determines whether a line fault has occurred based on the zero-mode voltage of the line in the DC distribution network at the pole to be selected. Next, when a line fault occurs, a linear fit is performed on the decaying portion of the post-fault pole current to determine the fitting intercept. Finally, the faulty pole is selected based on the fitting intercept. By detecting the direction of the double-terminal same-pole current mutation and performing a linear fit on the decaying portion of the current, the present invention can more accurately determine the faulty section and pole, avoiding the possibility of misjudgment. Furthermore, the present invention implements automated calculation and fault diagnosis, reducing human intervention, lowering manual errors, and improving the accuracy and reliability of fault diagnosis. This method thus addresses the problem of prior art inability to accurately and reliably determine the faulty pole.

[0085] The above is a method for selecting a pole for a single-pole grounding fault in a DC distribution network provided in an embodiment of the present invention. The following is a system for selecting a pole for a single-pole grounding fault in a DC distribution network provided in an embodiment of the present invention.

[0086] See also Figure 3 , an embodiment of the present invention provides a single-pole grounding fault pole selection system for a DC distribution network, comprising:

[0087] The judging unit 201 is configured to judge whether a line fault occurs according to the line zero mode voltage in the DC distribution network of the selected pole.

[0088] The fitting unit 202 is used to collect the positive and negative currents at the beginning and end of the line when it is determined that a line fault has occurred, and perform linear fitting on the positive and negative currents respectively to obtain the fitting intercept of the positive beginning current of the line, the fitting intercept of the positive end current, the fitting intercept of the negative beginning current, and the fitting intercept of the negative end current of the line.

[0089] The pole selection unit 203 is used to select the fault pole based on the fitting intercept of the positive pole head end current, the fitting intercept of the positive pole terminal current, the fitting intercept of the negative pole head end current and the fitting intercept of the negative pole terminal current to obtain the fault pole.

[0090] Furthermore, an embodiment of the present invention provides a device for selecting a single-pole ground fault in a DC distribution network, the device comprising a processor and a memory:

[0091] The memory is used to store program code and transmit the program code to the processor;

[0092] The processor is configured to execute the steps of the method for selecting a pole for a single-pole grounding fault in a DC distribution network as described in the above method embodiment according to the instructions in the program code.

[0093] Furthermore, an embodiment of the present invention further provides a computer-readable storage medium for storing program code, wherein the program code is used to execute the method for selecting a pole for a single-pole grounding fault in a DC distribution network as described in the above method embodiment.

[0094] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0095] In the several embodiments provided by the present invention, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0096] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0097] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0098] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the portion that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the various embodiments of the method of the present invention. The aforementioned storage medium includes various media that can store program code, such as USB flash drives, mobile hard drives, read-only memories (ROMs), random access memories (RAMs), magnetic disks, or optical disks.

[0099] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for selecting a pole for a single-pole ground fault in a DC distribution network, characterized in that: include: Determine whether a line fault occurs according to the zero-mode voltage of the line in the DC distribution network of the selected pole; When a line fault is determined, the positive and negative currents at the beginning and end of the line are collected, and a straight line fitting is performed on the positive and negative currents respectively to obtain the fitting intercept of the positive beginning current, the fitting intercept of the positive end current, the fitting intercept of the negative beginning current, and the fitting intercept of the negative end current; Performing fault pole selection based on the fitting intercept of the positive electrode first-end current, the fitting intercept of the positive electrode terminal current, the fitting intercept of the negative electrode first-end current, and the fitting intercept of the negative electrode terminal current to obtain a fault pole; The performing fault pole selection based on the fitted intercept of the positive electrode first-end current, the fitted intercept of the positive electrode terminal current, the fitted intercept of the negative electrode first-end current, and the fitted intercept of the negative electrode terminal current to obtain the fault pole includes: S31, determining whether the signs of the fitted intercept of the positive electrode head-end current and the fitted intercept of the positive electrode terminal current, as well as the signs of the fitted intercept of the negative electrode head-end current and the fitted intercept of the negative electrode terminal current are the same; if they are the same, determining that there is no fault in the line pole; otherwise, executing step S32; S32, calculating the fitted intercept difference based on the fitted intercept difference calculation formula; Wherein, the expression of the fitting intercept difference calculation formula is: ； Where, is the fitted intercept difference, is the difference in the fitted intercept of the positive or negative pole of line i, is the fitted intercept of the current at the positive or negative end of line i, is the fitted intercept of the current at the positive or negative terminal of line i; S33: Determine the positive pole or negative pole of the line corresponding to the item with the largest fitting intercept difference as the fault pole of the faulty line.

2. The method for selecting a pole for a single-pole ground fault in a DC distribution network according to claim 1, wherein: The determining whether a line fault occurs according to the line zero mode voltage in the DC distribution network of the selected pole includes: The positive and negative voltages at the head end of a line in a DC distribution network to be selected are detected in real time, the line zero-mode voltage is calculated based on the positive and negative voltages, and whether a line fault occurs is determined based on the line zero-mode voltage.

3. The method for selecting a pole for a single-pole grounding fault in a DC distribution network according to claim 2, wherein: The calculating the line zero mode voltage according to the positive electrode voltage and the negative electrode voltage includes: Substituting the positive electrode voltage and the negative electrode voltage into a calculation formula of the line zero mode voltage to calculate the line zero mode voltage; Among them, the calculation formula of the line zero mode voltage is: ； Where, and are the positive electrode voltage and the negative electrode voltage at the head end of the line respectively; is the line zero mode voltage.

4. The method for selecting a pole for a single-pole grounding fault in a DC distribution network according to claim 2, wherein: The determining whether a line fault occurs according to the line zero mode voltage includes: When the line zero-mode voltage is greater than a preset zero-mode voltage start-up setting value, it is determined that a line fault occurs.

5. The method for selecting a pole for a single-pole grounding fault in a DC distribution network according to claim 1, wherein: The positive and negative currents at the beginning and end of the acquisition circuit include: The positive and negative currents at the beginning and end of the line are collected through the feeder terminal units, wherein the feeder terminal units are respectively arranged at the beginning and end of the line.

6. The method for selecting a pole for a single-pole ground fault in a DC distribution network according to claim 5, characterized in that: The linear fitting of the positive and negative electrode currents includes: Fit the positive and negative electrode currents based on the fitting formula and calculate the fitting intercept; Wherein, the expression of the fitting formula is: ； Where, is the fitting slope; is the fitting intercept; N is the total number of pole current sampling points, , , , ; is the pole current for straight line fitting; is the corresponding time series, and n is the pole current sampling point.

7. A single-pole ground fault selection system for a DC distribution network, characterized in that: include: a judgment unit, configured to judge whether a line fault occurs according to the zero-mode voltage of the line in the DC distribution network of the selected pole; A fitting unit is used to collect the positive and negative currents at the beginning and end of the line after determining that a line fault has occurred, and perform linear fitting on the positive and negative currents respectively to obtain the fitting intercept of the positive beginning current, the fitting intercept of the positive end current, the fitting intercept of the negative beginning current, and the fitting intercept of the negative end current of the line; a pole selection unit, configured to perform fault pole selection based on the fitted intercept of the positive pole head-end current, the fitted intercept of the positive pole terminal current, the fitted intercept of the negative pole head-end current, and the fitted intercept of the negative pole terminal current to obtain a fault pole; The performing fault pole selection based on the fitted intercept of the positive electrode first-end current, the fitted intercept of the positive electrode terminal current, the fitted intercept of the negative electrode first-end current, and the fitted intercept of the negative electrode terminal current to obtain the fault pole includes: S31, determining whether the signs of the fitted intercept of the positive electrode head-end current and the fitted intercept of the positive electrode terminal current, as well as the signs of the fitted intercept of the negative electrode head-end current and the fitted intercept of the negative electrode terminal current are the same; if they are the same, determining that there is no fault in the line pole; otherwise, executing step S32; S32, calculating the fitted intercept difference based on the fitted intercept difference calculation formula; Wherein, the expression of the fitting intercept difference calculation formula is: ； Where, is the fitted intercept difference, is the difference in the fitted intercept of the positive or negative pole of line i, is the fitted intercept of the current at the positive or negative end of line i, is the fitted intercept of the current at the positive or negative terminal of line i; S33: Determine the positive pole or negative pole of the line corresponding to the item with the largest fitting intercept difference as the fault pole of the faulty line.

8. A single-pole ground fault selection device for a DC distribution network, characterized in that: The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is configured to execute the method for selecting a pole for a single-pole grounding fault in a DC distribution network according to any one of claims 1 to 6 according to instructions in the program code.

9. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store program codes, and the program codes are used to execute the method for selecting a pole for a single-pole grounding fault in a DC distribution network according to any one of claims 1 to 6.

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