Current collection line single-phase earth fault distance measurement method and system based on multi-terminal information
By using a single-phase grounding fault ranging method of collecting lines with multi-end information in wind farms, the fault location is determined using the equalization principle and the damping least squares method, the problem of difficulty in single-ended method is solved, and high-precision fault ranging and cost reduction is achieved.
Patent Information
- Application Number
- CN202411729382.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-28
- Publication Date
- 2025-02-25
AI Technical Summary
In wind farms, it is difficult to measure the distance between a single-phase grounding fault of the collecting line, especially when the system has many branches, the single-ended electrical quantity cannot determine the fault branch.
The single-phase grounding fault ranging method of collecting lines based on multi-terminal information is used to measure the initial fault phase current, the initial fault phase voltage and the zero-sequence current, and the branch current of each fan after the fault and the location of each suspected fault point are determined by measuring the initial fault phase current, the initial fault phase voltage and the zero-sequence current, and multiple sets of measurement devices are installed at these points to determine the actual fault location.
It effectively solves the problem that the single-ended method cannot determine the fault branch, improves the accuracy and accuracy of fault ranging, reduces costs, and has good engineering application prospects.
Smart Images
Figure CN119510984A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of power system fault detection and protection, and in particular to a method and system for measuring single-phase grounding faults in a collector line based on multi-terminal information. Background Art
[0002] As the capacity of wind farms continues to increase, the distance of the collector lines within the field is getting longer and longer, and the probability of collector line failure is also increasing. Among them, single-phase grounding faults are the most frequent. The fault will not only cause the terminal voltage of the wind turbine on the collector line to drop, but also cause the voltage at the wind farm collection bus to drop, which will cause the terminal voltage of the wind turbines on other collector lines connected to the bus to drop, which may cause large-scale wind turbine disconnection accidents. Wind farm collector line failures have become an important factor that seriously restricts the safe and economical operation of wind power generation. Therefore, the rapid location and elimination of faults are of great significance to the safe and economical operation of the system.
[0003] Due to the complex structure of the wind farm collector line, with multiple wind turbine branch power supply access, when performing collector line fault distance measurement, generally only the voltage and current information of the wind farm step-up transformer low-voltage side at the collector line outlet can be obtained, and the terminal voltage and current of each wind turbine branch cannot be obtained, resulting in the current flowing through the collector line. Therefore, the distance measurement information is seriously insufficient and the distance measurement is difficult. In response to this problem, the prior art proposes a frequency domain impedance distance measurement algorithm based on fault section search, which makes full use of the characteristic that the high-voltage side of the wind turbine box transformer adopts a triangle connection method, which makes the zero-sequence current unable to pass through, uses the collector line outlet current to simplify the equivalent solution of the wind turbine branch current, and derives the fault branch voltage drop based on the zero-sequence current at the collector line outlet, which preliminarily solves the single-phase grounding fault distance measurement problem of the wind farm collector line. However, when the number of system branches increases, the single-ended measurement device may collect the same data, so the fault branch cannot be determined by relying solely on the single-ended electrical quantity. Summary of the invention
[0004] The present application provides a method and system for measuring the distance of a single-phase grounding fault of a collector line based on multi-terminal information, so as to at least solve the technical problem that when the number of system branches increases, the fault branch cannot be determined by relying solely on single-terminal electrical quantities.
[0005] The first embodiment of the present application provides a method for measuring the distance of a single-phase grounding fault of a collector line based on multi-terminal information, the method comprising:
[0006] Measure the initial fault phase current, initial fault phase voltage and zero-sequence current at the wind farm collector line outlet protection installation after the preset fault duration;
[0007] Based on the initial fault phase current and zero-sequence current, and using the equalization principle, determine the branch current of each wind turbine after the fault;
[0008] Based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current, the position of each suspected fault point is determined by using a damped least square method, and multiple groups of measuring devices are installed at each suspected fault point;
[0009] Measuring multiple fault phase currents and multiple fault phase voltages at each suspected fault point using multiple groups of measuring devices installed at each suspected fault point;
[0010] The actual fault position is determined according to the multiple fault phase currents and the multiple fault phase voltages at each suspected fault point.
[0011] Preferably, the preset duration is 20ms;
[0012] The multiple groups of measuring devices all include: a current transformer and a voltage transformer.
[0013] Furthermore, the calculation formula of the branch current of each wind turbine after the fault is as follows:
[0014]
[0015] In the formula, i FG is the branch current of each wind turbine after the fault, is the initial fault phase current, i0 is the zero-sequence current, and n is the number of wind turbine branches connected to the collector circuit.
[0016] Furthermore, the method of determining the location of each suspected fault point based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method includes:
[0017] The collector line connected with n wind turbines is divided into n sections with the wind turbine branch grid connection node as the dividing point;
[0018] Search each section separately, and find the optimal solution of the fault distance of each section based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method;
[0019] The position corresponding to the optimal solution of each fault distance is taken as the position of each suspected fault point.
[0020] Furthermore, determining the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point includes:
[0021] Determine the fault distance corresponding to each group of measuring devices at each suspected fault point according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point;
[0022] Determine the difference between the fault distances corresponding to the groups of measuring devices at each suspected fault point;
[0023] Sorting the difference values of the suspected fault points in order from small to large and from left to right to form a difference value sequence;
[0024] The fault distance of the suspected fault point corresponding to the first difference value on the left in the difference value sequence is determined as the actual fault position.
[0025] The second embodiment of the present application proposes a collector line single-phase grounding fault distance measurement system based on multi-terminal information, including:
[0026] The first measurement module is used to measure the initial fault phase current, initial fault phase voltage and zero-sequence current after the preset fault time at the wind farm collector line outlet protection installation location;
[0027] A first determination module is used to determine the branch current of each wind turbine after the fault based on the initial fault phase current and zero-sequence current and using an equal sharing principle;
[0028] A second determination module is used to determine the position of each suspected fault point based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current using a damped least squares method, and to install multiple groups of measuring devices at each suspected fault point;
[0029] The second measurement module is used to measure multiple fault phase currents and multiple fault phase voltages at each suspected fault point by using multiple groups of measurement devices installed at each suspected fault point;
[0030] The third determination module is used to determine the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point.
[0031] Preferably, the preset duration is 20ms;
[0032] The multiple groups of measuring devices all include: a current transformer and a voltage transformer.
[0033] Furthermore, the calculation formula of the branch current of each wind turbine after the fault is as follows:
[0034]
[0035] In the formula, i FG is the branch current of each wind turbine after the fault, is the initial fault phase current, i0 is the zero-sequence current, and n is the number of wind turbine branches connected to the collector circuit.
[0036] Furthermore, the second determining module is further used for:
[0037] The collector line connected with n wind turbines is divided into n sections with the wind turbine branch grid connection node as the dividing point;
[0038] Searching each section respectively, and finding the optimal solution of the fault distance of each section based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method;
[0039] The position corresponding to the optimal solution of each fault distance is taken as the position of each suspected fault point.
[0040] Furthermore, the third determination module is also used for:
[0041] Determine the fault distance corresponding to each group of measuring devices at each suspected fault point according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point;
[0042] Determine the difference between the fault distances corresponding to the groups of measuring devices at each suspected fault point;
[0043] Sorting the difference values of the suspected fault points in order from small to large and from left to right to form a difference value sequence;
[0044] The fault distance of the suspected fault point corresponding to the first difference value on the left in the difference value sequence is determined as the actual fault position.
[0045] The third aspect of the present application provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in the first aspect is implemented.
[0046] A fourth aspect of the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described in the first aspect of the present application.
[0047] The technical solution provided by the embodiments of the present application brings at least the following beneficial effects:
[0048] The present application proposes a method and system for measuring the distance of a single-phase grounding fault of a collector line based on multi-terminal information, the method comprising: measuring the initial fault phase current, initial fault phase voltage, and zero-sequence current after the preset fault duration at the installation location of the outlet protection of the collector line of the wind farm; based on the initial fault phase current and zero-sequence current, and using the principle of equal distribution to determine the branch current of each wind turbine after the fault; based on the initial fault phase voltage, initial fault phase current, and zero-sequence current, and using the damped least squares method to determine the location of each suspected fault point, and installing multiple groups of measuring devices at each suspected fault point; using the multiple groups of measuring devices installed at each suspected fault point to measure multiple fault phase currents and multiple fault phase voltages at each suspected fault point; determining the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point. The technical solution proposed in the present application determines the actual fault location by using the electrical quantities collected by the additional measuring device under different fault conditions, solving the problem that multiple suspected fault points are obtained on different branches in the single-terminal method, and the actual fault location cannot be determined. The cost is low and has good engineering application prospects.
[0049] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0050] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:
[0051] Figure 1 A flowchart of a collector line single-phase grounding fault distance measurement method based on multi-terminal information provided according to an embodiment of the present application;
[0052] Figure 2 A schematic diagram of a double-fed wind farm model provided according to an embodiment of the present application;
[0053] Figure 3 A schematic diagram of fan branch wiring provided according to an embodiment of the present application;
[0054] Figure 4 A simplified equivalent network diagram of a single-phase grounding fault of an electric field collector line provided according to an embodiment of the present application;
[0055] Figure 5 The present invention is a structural diagram of a collector line single-phase grounding fault distance measurement system based on multi-terminal information according to an embodiment of the present application. DETAILED DESCRIPTION
[0056] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.
[0057] The present application proposes a method and system for measuring the distance of a single-phase grounding fault of a collector line based on multi-terminal information, the method comprising: measuring the initial fault phase current, initial fault phase voltage, and zero-sequence current after the preset fault duration at the installation location of the outlet protection of the collector line of the wind farm; based on the initial fault phase current and zero-sequence current, and using the principle of equal distribution to determine the branch current of each wind turbine after the fault; based on the initial fault phase voltage, initial fault phase current, and zero-sequence current, and using the damped least squares method to determine the location of each suspected fault point, and installing multiple groups of measuring devices at each suspected fault point; using the multiple groups of measuring devices installed at each suspected fault point to measure multiple fault phase currents and multiple fault phase voltages at each suspected fault point; determining the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point. The technical solution proposed in the present application determines the actual fault location by using the electrical quantities collected by the additional measuring device under different fault conditions, solving the problem that multiple suspected fault points are obtained on different branches in the single-terminal method, and the actual fault location cannot be determined. The cost is low and has good engineering application prospects.
[0058] The following describes a method and system for measuring single-phase grounding faults in a collector line based on multi-terminal information in accordance with an embodiment of the present application with reference to the accompanying drawings.
[0059] Embodiment 1
[0060] Figure 1 The flowchart of a method for measuring the distance of a collector line single-phase ground fault based on multi-terminal information is provided according to an embodiment of the present application. Figure 1 As shown, the method includes:
[0061] Step 1: Measure the initial fault phase current, initial fault phase voltage, and zero-sequence current at the wind farm collector line outlet protection installation point after the fault preset time;
[0062] It should be noted that the preset time length may be 20 ms.
[0063] Step 2: Based on the initial fault phase current and zero-sequence current, the branch current of each wind turbine after the fault is determined by using the equalization principle;
[0064] In the disclosed embodiment, the calculation formula of the branch current of each wind turbine after the fault is as follows:
[0065]
[0066] In the formula, i FG is the branch current of each wind turbine after the fault, is the initial fault phase current, i0 is the zero-sequence current, and n is the number of wind turbine branches connected to the collector circuit.
[0067] Step 3: Determine the location of each suspected fault point based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current using the damped least squares method, and install multiple groups of measuring devices at each suspected fault point;
[0068] It should be noted that the multiple groups of measuring devices all include: a current transformer and a voltage transformer.
[0069] In the embodiment of the present disclosure, the location of each suspected fault point is determined based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method, including:
[0070] The collector line connected with n wind turbines is divided into n sections with the wind turbine branch grid connection node as the dividing point;
[0071] Search each section separately, and find the optimal solution of the fault distance of each section based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method;
[0072] The position corresponding to the optimal solution of each fault distance is taken as the position of each suspected fault point.
[0073] Specifically, the collector line connected to n wind turbines is divided into n sections with the wind turbine branch grid connection node as the dividing point, and the length of each section is l1, l2...l n , start searching for the l1 segment from m=1, set the initial value of the fault distance l to half of the longest distance of the collector line, use the damped least squares method to fit the optimal solution, and get the distance measurement result of the mth segment; the m value increases successively, and the corresponding search segment also increases accordingly, until all segments are searched, and all possible fault points, that is, all suspected fault points, are obtained.
[0074] For example, if there are 6 wind turbines connected to the collector circuit, the collector circuit is divided into 6 sections;
[0075] Assuming that the first segment l1 is faulty, the formula for the optimal solution obtained by the damped least squares method is as follows:
[0076]
[0077] Assuming that the second segment l2 fails, the formula for the optimal solution obtained by the damped least squares method is as follows:
[0078]
[0079] Assuming that the fault occurs in the 6th segment, the formula for the optimal solution obtained by the damped least squares method is as follows:
[0080]
[0081] In the formula, is the initial fault phase voltage, k R for, is the positive sequence resistance of the collector line, l is the optimal solution for the fault distance, k L is the inductor zero-sequence current compensation coefficient, is the positive sequence inductance of the collector line, R f is the transition resistance, l2 is the length of the second segment, l3 is the length of the third segment, l4 is the length of the fourth segment, and l5 is the length of the fifth segment, where:
[0082]
[0083] Among them, assuming that the mth segment l m When a fault occurs, the formula for the optimal solution obtained by the damped least squares method is as follows:
[0084]
[0085] It should be noted that in the above formula, m may be equal to n.
[0086] It should be noted that if the optimal solution of the fault distance obtained in each segment is within the range of its corresponding division, the optimal solution of the fault distance is taken as the suspected fault point.
[0087] Step 4: using multiple groups of measuring devices installed at each suspected fault point to measure multiple fault phase currents and multiple fault phase voltages at each suspected fault point;
[0088] Step 5: Determine the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point.
[0089] In the embodiment of the present disclosure, step 5 specifically includes:
[0090] Determine the fault distance corresponding to each group of measuring devices at each suspected fault point according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point;
[0091] Determine the difference between the fault distances corresponding to the groups of measuring devices at each suspected fault point;
[0092] Sorting the difference values of the suspected fault points in order from small to large and from left to right to form a difference value sequence;
[0093] The fault distance of the suspected fault point corresponding to the first difference value on the left in the difference value sequence is determined as the actual fault position.
[0094] It should be noted that the calculation formula for the difference between the fault distances corresponding to each group of measurement devices at each suspected fault point is as follows:
[0095]
[0096] In the formula, f k is the difference between the fault distances corresponding to each group of measuring devices at the kth suspected fault point, l ki is the fault distance corresponding to the i-th group of measuring devices, l kj is the fault distance corresponding to the jth group of measuring devices, and p is the total number of measuring devices installed at a fault point.
[0097] For example, the double-fed wind farm model using the method of the present invention is as follows: Figure 2 The fan branch wiring diagram is as shown in Figure 3 As shown in the figure, the simplified equivalent network of the single-phase grounding fault of the wind farm collector line is as follows: Figure 4 As shown; the length of the collector line is 8km, and the line parameter values are shown in Table 1. A total of 6 1.5MW double-fed wind turbines are connected to the collector line, and the distance between every two wind turbines on the collector line is 2km. Therefore, the wind farm collector line is divided into 6 sections, and the length of each section is 2km. The fault distance measurement device using the method of the present invention measures the bus voltage and the current value at the collector line outlet through a voltage transformer (PT) and a current transformer (CT). Assume Figure 2 A single-phase grounding fault occurs at phase A at the midpoint of segment EF. The actual fault distance is 7 km and the transition resistance is set to 10 Ω.
[0098] Table 1 Main parameters of wind farm collector lines
[0099]
[0100] 1) Measure 100 sets of data (80 sets of data in one cycle) 20ms after the fault of the line at the protection installation as the input quantity, that is, the initial phase voltage u a , initial phase current i a , zero sequence current i0;
[0101] 2) Calculate the branch current i of each wind turbine after the fault based on the equal distribution principle FG :
[0102]
[0103] 3) The ranging results are shown in Table 2:
[0104] Table 2 Distance measurement results and errors of different fault points on wind farm collector lines
[0105]
[0106] It can be seen from Table 2 that the collector line single-phase grounding fault location method based on multi-terminal information provided by this embodiment has high accuracy.
[0107] To sum up, the present embodiment proposes a method for measuring the distance of a single-phase grounding fault of a collector line based on multi-terminal information. The method uses the electrical quantities collected by the additional measuring device under different fault conditions to determine the actual fault location. This solves the problem that multiple suspected fault points are obtained on different branches of the single-terminal method and the actual fault location cannot be determined. The method has low cost and good engineering application prospects.
[0108] Embodiment 2
[0109] Figure 5 The structure diagram of a collector line single-phase grounding fault distance measurement system based on multi-terminal information according to an embodiment of the present application is as follows: Figure 5 As shown, the system comprises:
[0110] The first measurement module 100 is used to measure the initial fault phase current, initial fault phase voltage and zero-sequence current after a preset fault time at the wind farm collector line outlet protection installation location;
[0111] Wherein, the preset duration is 20ms;
[0112] A first determination module 200 is used to determine the branch current of each wind turbine after the fault based on the initial fault phase current and zero-sequence current and using an equal distribution principle;
[0113] Among them, the calculation formula of the branch current of each wind turbine after the fault is as follows:
[0114]
[0115] In the formula, i FG is the branch current of each wind turbine after the fault, is the initial fault phase current, i0 is the zero-sequence current, and n is the number of wind turbine branches connected to the collector circuit.
[0116] A second determination module 300 is used to determine the position of each suspected fault point based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current using a damped least squares method, and to install multiple groups of measuring devices at each suspected fault point;
[0117] Wherein, the multiple groups of measuring devices all include: a current transformer and a voltage transformer;
[0118] The second measurement module 400 is used to measure multiple fault phase currents and multiple fault phase voltages at each suspected fault point using multiple groups of measurement devices installed at each suspected fault point;
[0119] The third determination module 500 is used to determine the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point.
[0120] In the embodiment of the present disclosure, the second determining module 300 is further configured to:
[0121] The collector line connected with n wind turbines is divided into n sections with the wind turbine branch grid connection node as the dividing point;
[0122] Search each section separately, and find the optimal solution of the fault distance of each section based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method;
[0123] The position corresponding to the optimal solution of each fault distance is taken as the position of each suspected fault point.
[0124] In the embodiment of the present disclosure, the third determining module 500 is further used to:
[0125] Determine the fault distance corresponding to each group of measuring devices at each suspected fault point according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point;
[0126] Determine the difference between the fault distances corresponding to the groups of measuring devices at each suspected fault point;
[0127] Sorting the difference values of the suspected fault points in order from small to large and from left to right to form a difference value sequence;
[0128] The fault distance of the suspected fault point corresponding to the first difference value on the left in the difference value sequence is determined as the actual fault position.
[0129] In summary, the present embodiment proposes a collector line single-phase grounding fault distance measurement system based on multi-terminal information, which uses the electrical quantities collected by the additional measuring device under different fault conditions to determine the actual fault location, thereby solving the problem of obtaining multiple suspected fault points on different branches in the single-terminal method and being unable to determine the actual fault location. The system has low cost and good engineering application prospects.
[0130] Embodiment 3
[0131] In order to implement the above embodiments, the present disclosure further proposes an electronic device, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the method described in Embodiment 1 is implemented.
[0132] Embodiment 4
[0133] In order to implement the above embodiments, the present disclosure further proposes a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the method described in the first embodiment is implemented.
[0134] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.
[0135] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or more executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.
[0136] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.
Claims
1. A method for measuring the distance of a single-phase grounding fault of a collector line based on multi-terminal information, characterized in that: The method comprises: Measure the initial fault phase current, initial fault phase voltage and zero-sequence current at the wind farm collector line outlet protection installation after the preset fault duration; Based on the initial fault phase current and zero-sequence current, and using the equalization principle, determine the branch current of each wind turbine after the fault; Based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current, the position of each suspected fault point is determined by using a damped least square method, and multiple groups of measuring devices are installed at each suspected fault point; Measuring multiple fault phase currents and multiple fault phase voltages at each suspected fault point using multiple groups of measuring devices installed at each suspected fault point; The actual fault position is determined according to the multiple fault phase currents and the multiple fault phase voltages at each suspected fault point.
2. The method according to claim 1, characterized in that The preset duration is 20ms; The multiple groups of measuring devices all include: a current transformer and a voltage transformer.
3. The method according to claim 2, characterized in that The calculation formula of the branch current of each fan after the fault is as follows: In the formula, i FG is the branch current of each wind turbine after the fault, is the initial fault phase current, i0 is the zero-sequence current, and n is the number of wind turbine branches connected to the collector circuit.
4. The method according to claim 3, characterized in that The method of determining the location of each suspected fault point based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current and using the damped least squares method includes: The collector line connected with n wind turbines is divided into n sections with the wind turbine branch grid connection node as the dividing point; Searching each section respectively, and finding the optimal solution of the fault distance of each section based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method; The position corresponding to the optimal solution of each fault distance is taken as the position of each suspected fault point.
5. The method according to claim 4, characterized in that Determining the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at the suspected fault points includes: Determine the fault distance corresponding to each group of measuring devices at each suspected fault point according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point; Determine the difference between the fault distances corresponding to the groups of measuring devices at each suspected fault point; Sorting the difference values of the suspected fault points in order from small to large and from left to right to form a difference value sequence; The fault distance of the suspected fault point corresponding to the first difference value on the left in the difference value sequence is determined as the actual fault position.
6. A collector line single-phase grounding fault distance measurement system based on multi-terminal information, characterized in that: The system comprises: The first measurement module is used to measure the initial fault phase current, initial fault phase voltage and zero-sequence current after the preset fault time at the wind farm collector line outlet protection installation location; A first determination module is used to determine the branch current of each wind turbine after the fault based on the initial fault phase current and zero-sequence current and using an equal sharing principle; A second determination module is used to determine the position of each suspected fault point based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current using a damped least squares method, and to install multiple groups of measuring devices at each suspected fault point; The second measurement module is used to measure multiple fault phase currents and multiple fault phase voltages at each suspected fault point by using multiple groups of measurement devices installed at each suspected fault point; The third determination module is used to determine the actual fault location according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point.
7. The system according to claim 6, characterized in that The preset duration is 20ms; The multiple groups of measuring devices all include: a current transformer and a voltage transformer.
8. The system according to claim 7, characterized in that The calculation formula of the branch current of each fan after the fault is as follows: In the formula, i FG is the branch current of each wind turbine after the fault, is the initial fault phase current, i0 is the zero-sequence current, and n is the number of wind turbine branches connected to the collector circuit.
9. The system according to claim 8, characterized in that The second determining module is further used for: The collector line connected with n wind turbines is divided into n sections with the wind turbine branch grid connection node as the dividing point; Searching each section respectively, and finding the optimal solution of the fault distance of each section based on the initial fault phase voltage, the initial fault phase current, and the zero-sequence current by using the damped least squares method; The position corresponding to the optimal solution of each fault distance is taken as the position of each suspected fault point.
10. The system according to claim 9, characterized in that The third determination module is further used for: Determine the fault distance corresponding to each group of measuring devices at each suspected fault point according to the multiple fault phase currents and multiple fault phase voltages at each suspected fault point; Determine the difference between the fault distances corresponding to the groups of measuring devices at each suspected fault point; Sorting the difference values of the suspected fault points in order from small to large and from left to right to form a difference value sequence; The fault distance of the suspected fault point corresponding to the first difference value on the left in the difference value sequence is determined as the actual fault position.