Positive sequence component-based accurate fault positioning method for multi-source power distribution network
By adopting the fault positioning method of positive sequence components in a multi-source distribution network, and using Davidan equivalent and virtual bus iterative calculations, the problem of low positioning accuracy in traditional methods in complex power grids is solved, and more efficient and accurate fault positioning is achieved.
Patent Information
- Application Number
- CN202510183323.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-19
- Publication Date
- 2025-05-30
AI Technical Summary
Traditional fault positioning methods have large distance measurement dead zones near branch contacts, and it is difficult to achieve accurate fault positioning in complex multi-end lines.
The fault location method of multi-source distribution network based on positive sequence components is adopted, and through iterative calculation of Davidan equivalent and virtual buses, the fault indicators and impedance matrix are constructed, the fault area is identified and the fault location is accurately positioned.
It improves the accuracy and speed of fault positioning, reduces misjudgment and misreport, and is suitable for complex multi-source distribution networks.
Smart Images
Figure CN120068794A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of multi-source distribution network fault location, and more specifically, to an accurate fault location method for multi-source distribution network based on positive sequence components. Background Art
[0002] Whether the distribution network can operate safely and stably directly determines the living standards of the vast number of users. With the large-scale access of distributed power sources, the distribution network has changed from the original single-source and radial structure to a multi-source and two-way power flow grid structure, increasing the difficulty of fault location. The accurate location of the fault position is of great significance for shortening the power outage time, reducing the power outage scope, and providing power supply reliability. With the increasing complexity of the power grid structure and the wide access of distributed power sources, such as the continuous increase in the penetration rate of wind turbines in the power grid and the development of new power grid structures (such as "petal-shaped" distribution networks), the fault location of multi-source distribution networks faces new challenges. Traditional fault location methods often have a large ranging dead zone near the branch connection points, and most methods cannot be well extended to multi-terminal lines with relatively complex topological structures. Therefore, it is necessary to study new fault location methods to meet the accuracy and rapidity requirements for the fault location of complex multi-source distribution networks.
[0003] In the above disclosed technical solutions, there are at least the following technical problems: some methods have a large ranging dead zone near the branch connection points, resulting in low positioning accuracy; there are also some methods that have poor effects when dealing with the fault location of multi-terminal lines containing distributed power sources (such as wind turbines). In view of the above problems, the present invention proposes a solution. Summary of the Invention
[0004] In order to overcome the above-mentioned defects of the prior art, an embodiment of the present invention provides an accurate fault location method for multi-source distribution network based on positive sequence components, which realizes the discrimination of the fault branch by adopting two opposite states of the solvability and unsolvability of the double-terminal equation, so as to solve the problem of large ranging dead zone near the branch connection points proposed in the above background art.
[0005] To achieve the above object, the present invention provides the following technical solutions: An accurate fault location method for multi-source distribution network based on positive sequence components, comprising the following steps: collecting the operation data before and after the fault at the power source detection points of the power grid; performing Thevenin equivalent on the power sources of the power grid, and calculating the positive sequence Thevenin equivalent impedance of the power grid based on the operation data; establishing a positive sequence bus impedance matrix based on the positive sequence Thevenin equivalent impedance; constructing a fault index based on the positive sequence bus impedance matrix and the current and voltage information before and after the fault to identify the fault area; accurately locating the fault position through constructing a virtual bus according to the fault area.
[0006] In a preferred embodiment, the operating data includes current data, voltage data, power data, frequency data, timestamp, and environmental conditions.
[0007] In a preferred embodiment, for the Thevenin equivalent of the grid power supply, the positive-sequence Thevenin equivalent impedance of the grid power supply is calculated based on the operating data, specifically: the current and voltage information before and after the fault at the grid power supply detection point are collected respectively; based on the symmetrical component method, the collected current and voltage data are decomposed into positive-sequence, negative-sequence, and zero-sequence components, and the positive-sequence components are extracted; according to the Thevenin equivalent principle, the positive-sequence Thevenin equivalent impedance of the grid power supply is calculated through the change in the positive-sequence voltage and current of the bus before and after the fault. In a preferred embodiment, for establishing the positive-sequence bus impedance matrix based on the positive-sequence Thevenin equivalent impedance, specifically: all the buses and their corresponding branches in the grid are obtained; the positive-sequence Thevenin equivalent impedance of each bus is collected, including the positive-sequence equivalent impedance of each power source and the positive-sequence impedance of the branch; according to the topological structure of the grid, the positive-sequence impedance with lumped parameters is used as the equivalent model, and the grid power supply is equivalent with the positive-sequence equivalent impedance to establish the positive-sequence bus impedance matrix.
[0008] In a preferred embodiment, for constructing a fault index based on the positive-sequence bus impedance matrix and the current and voltage information before and after the fault to identify the fault area, specifically: fault indices are defined, including the current change rate and the voltage change rate; the current and voltage data of all buses before and after the fault are collected, and the current change rate and voltage change rate of each bus are calculated; a comprehensive fault index is constructed by combining the change rates of current and voltage; the grid power supply is divided into main lines and branch lines; the positive-sequence component of the fault current and the positive-sequence bus impedance are calculated according to the symmetrical component method; the positive-sequence voltage change at the fault is calculated based on the comprehensive fault index, the positive-sequence component of the fault current, and the positive-sequence bus impedance according to a preset formula; the slope of the voltage profile in different areas is obtained from the positive-sequence voltage change at the fault; the fault area is identified according to the intersection of the actual voltage value during the fault and the slope of the voltage profile in different areas.
[0009] In a preferred embodiment, the precise fault location according to the fault area by constructing a virtual bus is specifically as follows: identifying the fault area through fault indicators and a fault impact matrix; within the fault area, selecting several points as virtual buses according to the layout of the actual buses and the connection conditions of adjacent buses, and setting voltage and current values for each virtual bus; establishing a virtual bus electrical model based on several virtual buses and the positive sequence bus impedance matrix; calculating currents and voltages according to the electrical model using Kirchhoff's current law and Kirchhoff's voltage law to obtain electrical data under fault conditions; solving for the currents and voltages of the virtual buses by minimizing the sum of the squares of the changes in currents and voltages before and after the fault, thereby initially inferring the fault location; further refining the positions of the virtual buses within the fault area according to the initial inference results, and adding more virtual buses at important nodes; accurately determining the fault location in combination with the current and voltage data of the virtual buses.
[0010] The technical effects and advantages of a precise fault location method for a multi-source distribution network based on positive sequence components according to the present invention are as follows: 1. The present invention realizes precise fault location through the method of establishing iterative calculations of virtual buses, with higher positioning accuracy.
[0011] 2. The present invention only uses the current and voltage information at the power source before and after the fault to identify the fault section and locate the fault position, without relying on protection devices, thus avoiding misjudgment caused by malfunction of protection devices on site.
[0012] 3. The bus impedance matrix established by the present invention is only related to the Thevenin equivalent impedance of the grid power source and the inherent parameters of the distribution network. Therefore, the positioning accuracy of this method is not affected by the fault type, fault location, and grounding resistance. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 It is a schematic structural diagram of a precise fault location method for a multi-source distribution network based on positive sequence components according to the present invention.
[0014] Figure 2 It is a schematic diagram of the Thevenin equivalent of the grid power source.
[0015] Figure 3 It is a schematic diagram of the equivalent network structure of a multi-source distribution network during a fault.
[0016] Figure 4 It is the positive sequence voltage curve at T(1) when positive sequence fault currents are injected at different nodes in a multi-source distribution network.
[0017] Figure 5 It is the positive sequence voltage curve at T(K) when positive sequence fault currents are injected at different nodes in a multi-source distribution network.
[0018] Figure 6It is a schematic diagram for fault point location.
[0019] Figure 7 It is a flow chart for fault section identification.
[0020] Figure 8 It is a flow chart for precise fault point location. Specific implementation manners
[0021] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0022] Embodiment 1 Figure 1 A precise fault location method for a multi-source distribution network based on positive sequence components according to the present invention is given, including the following steps: Collect the operation data of the power grid power detection point before and after the fault; Perform Thevenin equivalent on the power grid power supply, and calculate the positive sequence Thevenin equivalent impedance of the power grid power supply based on the operation data; Establish a positive sequence bus impedance matrix based on the positive sequence Thevenin equivalent impedance; Based on the positive sequence bus impedance matrix and the current and voltage information before and after the fault, construct a fault index to identify the fault area; Precisely locate the fault location by constructing a virtual bus according to the fault area.
[0023] S1. Collect the operation data of the power grid power detection point before and after the fault; The operation data includes current data, voltage data, power data, frequency data, time stamp and environmental conditions; Current data: The current values at each detection point before and after the fault, including phase current and line current, usually the changes before and after the fault need to be recorded.
[0024] Voltage data: The voltage values at each detection point before and after the fault, including phase voltage and line voltage, so as to analyze the voltage fluctuation of the power grid before and after the fault.
[0025] Power data: Include the measured values of active power and reactive power to help evaluate the impact of the fault on the power transmission of the power grid.
[0026] Frequency data: The change of the power grid frequency when the fault occurs may affect the analysis of fault location.
[0027] Time stamp: Record the time of data collection to facilitate the analysis of the time series of the fault occurrence.
[0028] Environmental conditions, such as temperature and humidity, although having little impact on fault location, may affect the device performance under certain circumstances.
[0029] S2: Perform Thevenin equivalent on the grid power supply and calculate the positive-sequence Thevenin equivalent impedance of the grid power supply based on the operating data. The Thevenin equivalent principle means that a linear two-terminal network N containing independent sources can be equivalent, in terms of its external behavior, to a series combination of an independent voltage source and a relaxed two-terminal network N'. Among them, the independent voltage source is the open-circuit voltage of network N; the relaxed network N' is the network obtained by setting all independent sources and the initial conditions on all dynamic elements in the original network N to zero.
[0030] The Thevenin equivalent principle simplifies a complex circuit network into a combination of a voltage source and an internal resistance. In this problem, we regard the grid power supply as a complex circuit network and simplify it through Thevenin equivalent.
[0031] Performing Thevenin equivalent on the grid power supply and calculating the positive-sequence Thevenin equivalent impedance of the grid power supply based on the operating data specifically includes: Collect the current and voltage information before and after the fault at the grid power supply detection points respectively. Decompose the collected current and voltage data into positive-sequence, negative-sequence, and zero-sequence components based on the symmetrical component method, and extract the positive-sequence components. According to the Thevenin equivalent principle, calculate the positive-sequence Thevenin equivalent impedance of the grid power supply through the change in the positive-sequence voltage and current of the bus before and after the fault. The calculation method for performing Thevenin equivalent on the grid power supply is as follows: (1) (2) In the formula: E is the power supply voltage, V is the bus voltage, I is the bus current, is the positive-sequence Thevenin equivalent impedance, is the bus voltage before the fault, is the bus current before the fault, is the positive-sequence voltage of the bus after the fault, is the positive-sequence current of the bus after the fault.
[0032] According to formulas (1) and (2), it can be known that: (3) The positive-sequence Thevenin equivalent impedance of the grid power supply can be expressed as: (4) Among them, 、 They respectively represent the changes in positive-sequence voltage and current at the power bus due to a fault occurrence, which are respectively denoted as , .
[0033] The current and voltage information collected at the power grid power detection point are respectively denoted as , , and , , . The positive-sequence components of the current and voltage are obtained using the symmetrical component method, and the calculation formulas are as follows: (5) (6) Wherein, , represents the positive-sequence component of the current, represents the positive-sequence component of the voltage.
[0034] The power grid power is subjected to Thevenin equivalent, and the positive-sequence Thevenin equivalent impedance of the power grid power is calculated based on the operation data, which has the following advantages for the accurate fault location of the multi-source distribution network: Improve the accuracy of fault location: The Thevenin equivalent circuit can simplify the complex power grid structure, making the fault location problem more intuitive and easier to solve. By calculating the positive-sequence Thevenin equivalent impedance, the electrical characteristics of the power grid can be more accurately reflected, thereby improving the accuracy of fault location.
[0035] Enhance the accuracy of the model: In a multi-source distribution network, due to the existence of multiple power sources and complex network structures, traditional fault location methods may be affected by interference and errors. The Thevenin equivalent circuit provides a method to simplify the complex network into an equivalent model, thereby enhancing the accuracy of the model and reducing errors.
[0036] Overcome data uncertainty and measurement errors: In actual power grid operation, data uncertainty and measurement errors are inevitable. The Thevenin equivalent circuit and the calculation method of the positive-sequence Thevenin equivalent impedance can effectively overcome these errors and improve the reliability of fault location.
[0037] Adapt to multi-source networks: In a multi-source distribution network, due to the existence of multiple distributed power sources and complex network structures, traditional fault location methods may encounter difficulties. The Thevenin equivalent circuit provides a fault location method applicable to multi-source networks, enabling accurate fault location in a multi-source distribution network.
[0038] In summary, performing Thevenin equivalent on the grid power supply and calculating the positive-sequence Thevenin equivalent impedance of the grid power supply based on the operating data have significant benefits for the accurate fault location of multi-source distribution networks. This method not only improves the accuracy of fault location and the accuracy of the model, but also overcomes the influence of data uncertainty and measurement errors, and adapts to the complexity of multi-source networks.
[0039] S3. Establish a positive-sequence bus impedance matrix based on the positive-sequence Thevenin equivalent impedance; The establishment of the positive-sequence bus impedance matrix based on the positive-sequence Thevenin equivalent impedance is specifically as follows: Obtain all buses and their corresponding branches in the power grid; Collect the positive-sequence Thevenin equivalent impedance of each bus, including the positive-sequence equivalent impedance of each power source and the positive-sequence impedance of the branch; According to the topological structure of the power grid, use the positive-sequence impedance of lumped parameters as the equivalent model, and use the positive-sequence equivalent impedance for the equivalent of the grid power supply and establish a positive-sequence bus impedance matrix.
[0040] The specific calculation formula of the positive-sequence bus impedance matrix is as follows: (7) Among them, is the positive-sequence bus impedance matrix, n is the total number of grid power supplies, Zjj and Zij are the self-impedance and mutual impedance respectively. Their values are that when a unit current is injected into bus j and the injection currents of other buses are zero, the voltage on bus j is the self-impedance Zjj, and the voltage on bus i (i = 1, 2,..., n, i ≠ j) is the mutual impedance Zij between bus i and bus j. Ik is the injection current at bus k, and k is an integer from 1 to n that is not equal to j. (8) (9) Establishing a positive-sequence bus impedance matrix based on the positive-sequence Thevenin equivalent impedance has the following benefits in power system analysis, especially in aspects such as fault location, power flow calculation, and stability analysis of multi-source distribution networks: Simplify the calculation process: The positive-sequence Thevenin equivalent impedance simplifies the complex grid structure into a series circuit of an equivalent voltage source and impedance, thus greatly simplifying the calculation process. The positive-sequence bus impedance matrix established based on this can more intuitively reflect the electrical connection and impedance relationship between each bus in the power grid.
[0041] Improve the calculation accuracy: By accurately calculating the positive-sequence Thevenin equivalent impedance, the accuracy of the positive-sequence bus impedance matrix can be ensured. This helps to obtain more accurate results in subsequent power system analyses, such as power flow calculation and short-circuit current calculation.
[0042] Quick fault location: The positive-sequence bus impedance matrix can reflect the impedance relationship between each bus in the power grid. When a fault occurs in the power grid, by measuring the voltage and current at the fault point, the impedance relationship between the fault point and the bus can be calculated. Combining with the positive-sequence Thevenin equivalent impedance can quickly locate the fault point and improve the accuracy and speed of fault location.
[0043] Reduce false alarms and missed alarms: Traditional fault location methods may be affected by factors such as complex power grid structure and inaccurate data, resulting in false alarms or missed alarms. The positive-sequence bus impedance matrix established based on the positive-sequence Thevenin equivalent impedance can more accurately reflect the actual operation of the power grid, thus reducing the occurrence of false alarms and missed alarms.
[0044] Improve power grid stability: By analyzing the positive-sequence bus impedance matrix, the electrical connection and impedance relationship between each bus in the power grid can be understood, thus judging the stability of the power grid. This helps to take reasonable measures to improve the stability of the power grid in power grid planning and operation.
[0045] Guide power grid maintenance and repair: The positive-sequence bus impedance matrix can reflect the impedance relationship between each bus in the power grid. When a fault occurs in a certain bus or line, the cause and scope of the fault can be judged by analyzing the impedance matrix. This provides strong guidance for the maintenance and repair of the power grid, helping to detect problems in time and take corresponding measures for treatment.
[0046] S4. Based on the positive-sequence bus impedance matrix and the current and voltage information before and after the fault, construct a fault index to identify the fault area; The constructing a fault index to identify the fault area based on the positive-sequence bus impedance matrix and the current and voltage information before and after the fault is specifically as follows: Define fault indexes, including current change rate and voltage change rate; Collect the current and voltage data of all buses before and after the fault, and calculate the current change rate and voltage change rate of each bus; Combine the change rates of current and voltage to construct a comprehensive fault index; Divide the power grid power supply into main lines and branch lines; Calculate the positive-sequence component of the fault current and the positive-sequence bus impedance according to the symmetrical component method; Based on the comprehensive fault index, the positive-sequence component of the fault current and the positive-sequence bus impedance, calculate the positive-sequence voltage change at the fault point according to a preset formula; Obtain the slope of the voltage profile of different regions according to the positive-sequence voltage change at the fault point; Identify the fault area according to the intersection of the actual fault voltage value and the slope of the voltage profile of different regions.
[0047] Assume that the total number of grid power supplies is N, and the buses at the power supply are denoted as T(1), T(2), …… T(N); the branch nodes are denoted as B(2), B(3), … B(N - 1).
[0048] When a fault occurs at J, the change in the positive - sequence voltage at I is denoted as , and the calculation formula is as follows: (10) In the formula, is the change value of the positive - sequence voltage at I caused by injecting a fault current at J ; is the positive - sequence bus impedance when a unit current is injected at J and other current injections are zero, and the calculation formula is as follows: (11) is the positive - sequence component of the fault current injected at J. The positive - sequence component of the fault current is obtained by using the symmetrical component method, and the calculation formula is as follows: (12) Among them, .
[0049] According to Figure 3 the circuit topology shown, B(1)-B(2) to B(N - 1)-B(N) are the main lines, and B(2)-T(2) to B(N - 1)-T(N - 1) are the branch lines, represents the change in the positive - sequence voltage at T(1) when the fault current IF is injected at B(K); represents the change in the positive - sequence voltage at T(1) when the fault current IF is injected at B(K + 1).
[0050] According to Figure 3 the circuit topology, assuming that the fault current IF moves from B(K) to B(K + 1), the current distribution on the main line will change: less current will flow to T(1). When the same fault current IF is injected, the absolute value of will be less than the absolute value of
[0051] Generally speaking: (13) Similarly, by the same logic: (14) According to formulas 8 to 11, we can obtain the following relationships: (15) (16) The voltage profiles described by formulas 13 and 14 are as Figure 4 ,Figure 5 As shown. Starting from Figure 4 , Figure 5 It can be seen that the slope of the voltage profile in different regions depends on the bus impedance of that region, and this bus impedance is only related to the nature of the line itself.
[0052] represents the voltage value at T(1) during an actual fault, and is represented by a dashed line in Figure 4 . It can be clearly seen from Figure 4 that the dashed line represented has only one intersection with the main line B(K)-B(K + 1). Therefore, when a fault occurs on the main line, it can be accurately identified.
[0053] represents the voltage value at T(K) during an actual fault, and is represented by a dashed line in Figure 5 . It can be clearly seen from Figure 5 that the dashed line represented has only one intersection with the branch line B(K)-T(K), and this dashed line will not have any intersections with other branch lines and the main line. Therefore, when a fault occurs on the branch line, it can be accurately identified.
[0054] Through the above analysis, whether the fault occurs on the main line or the branch line, it can be accurately identified.
[0055] S5. Precise fault location is achieved by constructing virtual buses according to the fault area.
[0056] The precise fault location by constructing virtual buses according to the fault area is specifically as follows: Identify the fault area through fault indicators and the fault impact matrix; Within the fault area, select several points as virtual buses according to the layout of the actual buses and the connection conditions of adjacent buses, and set voltage and current values for each virtual bus; Establish a virtual bus electrical model based on several virtual buses and the positive sequence bus impedance matrix; According to the electrical model, use Kirchhoff's current law and Kirchhoff's voltage law to calculate current and voltage, and obtain electrical data under fault conditions; By minimizing the sum of the squares of the changes in current and voltage before and after the fault, solve for the current and voltage of the virtual buses, thereby initially inferring the fault location; According to the initial inference result, further refine the positions of the virtual buses within the fault area, and add more virtual buses at important nodes; Combine the current and voltage data of the virtual buses to accurately determine the location where the fault occurs.
[0057] The specific process of constructing a virtual bus to locate the fault location includes the following steps, and the flowchart is as shown in Figure 8 the following: Assume that the fault area is B(1)-B(2). Add a virtual bus at a short distance from B(1), denoted as B(New_Bus). It can be determined according to actual needs. Obviously, the smaller it is, the higher the positioning accuracy, but the more iteration times; the larger it is, the lower the positioning accuracy, but the fewer iteration times; It can be obtained by calculating with formula (8).
[0058] (17) In the formula: L is the line length of B(1)-B(2), and k is an integer.
[0059] Assume that the actual fault point is F. It can be seen from Figure 6 that when the virtual bus is at F(1), ; when the virtual bus is at F(2), ; only when the virtual bus is at F, .
[0060] Use the iterative method to repeat the process of S41. Add virtual buses at a short distance 2 from B(1) in turn, 3 ... k and calculate successively through formula (8), until , then this virtual bus is the accurate fault point.
[0061] Furthermore, in order to improve the positioning accuracy of this algorithm, when the fault area is B(K)-B(K + 1) or B(K)-T(K) (K = 2, 3... N - 1), select the power grid power supply T(K) closer to the fault area as the reference point, calculate , until .
[0062] The above formulas are all dimensionless and take their numerical values for calculation. The formula is obtained by collecting a large amount of data for software simulation to get a formula closest to the actual situation. The preset parameters in the formula are set by those skilled in the art according to the actual situation.
[0063] The above embodiments can be implemented in whole or in part by software, hardware, firmware or any other combination. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product.
[0064] Those of ordinary skill in the art will realize that the modules and algorithm steps of each example described in combination with the embodiments disclosed herein can be implemented in electronic hardware, or in a combination of computer software and electronic hardware. Whether these functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Skilled professionals can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of this application.
[0065] In addition, the functional modules in each embodiment of this application can be integrated into one processing module, or each module can exist physically alone, or two or more modules can be integrated into one module.
[0066] As described above, the above are only specific embodiments of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.
[0067] Finally: The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should all be included within the protection scope of the present invention.
Claims
1. A method for accurately locating faults in a multi-source distribution network based on positive sequence components, characterized in that: The following steps are involved: Collect the operation data before and after the failure of the power supply detection point of the power grid; Perform Thevenin equivalent on the power grid, and calculate the positive sequence Thevenin equivalent impedance of the power grid based on the operating data; Establish the positive-sequence bus impedance matrix based on the positive-sequence Thevenin equivalent impedance; Based on the positive-sequence bus impedance matrix and the current and voltage information before and after the fault, a fault index is constructed to identify the fault area; The fault location is accurately located by constructing a virtual bus according to the fault area.
2. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 1 is characterized in that: The operating data includes current data, voltage data, power data, frequency data, time stamps and environmental conditions.
3. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 2 is characterized in that: The grid power supply is subjected to Thevenin equivalence, and the positive sequence Thevenin equivalent impedance of the grid power supply is calculated based on the operation data, specifically: Collect the current and voltage information before and after the power grid power detection point fails respectively; Based on the symmetrical component method, the collected current and voltage data are decomposed into positive sequence, negative sequence and zero sequence components, and the positive sequence component is extracted; According to the Thevenin equivalent principle, the positive-sequence Thevenin equivalent impedance of the power grid is calculated by the changes in the positive-sequence voltage and current of the bus before and after the fault.
4. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 3 is characterized in that: The positive-sequence bus impedance matrix is established based on the positive-sequence Thevenin equivalent impedance, specifically: Get all the buses and their corresponding branches in the power grid; Collect the positive-sequence Thevenin equivalent impedance of each bus, including the positive-sequence equivalent impedance of each power source and the positive-sequence impedance of the branch; According to the topological structure of the power grid, the positive-sequence impedance with concentrated parameters is used as the equivalent model, the power grid power source adopts the positive-sequence equivalent impedance for equivalent value and establishes the positive-sequence bus impedance matrix.
5. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 4 is characterized in that: The fault index is constructed based on the positive sequence bus impedance matrix and the current and voltage information before and after the fault to identify the fault area, specifically: Define fault indicators, including current change rate and voltage change rate; Collect the current and voltage data of all buses before and after the fault, and calculate the current change rate and voltage change rate of each bus; Combine the rate of change of current and voltage to construct a comprehensive fault index; Divide the grid power supply into main lines and branch lines; Calculate the positive sequence component of fault current and positive sequence bus impedance according to the symmetrical component method; Based on the comprehensive fault index, the positive sequence component of the fault current and the positive sequence bus impedance, the positive sequence voltage change at the fault location is calculated according to a preset formula; The slope of the voltage profile in different areas is obtained according to the change of positive sequence voltage at the fault location; The fault area is identified based on the intersection of the voltage value at the actual fault and the slope of the voltage profiles in different areas.
6. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 5, characterized in that: The method of accurately locating the fault location by constructing a virtual bus according to the fault area is specifically as follows: Identify fault areas through fault indicators and fault impact matrix; In the fault area, several points are selected as virtual buses according to the layout of the actual bus and the connection of adjacent buses, and the voltage and current values are set for each virtual bus; According to several virtual buses combined with the positive sequence bus impedance matrix, a virtual bus electrical model is established; According to the electrical model, Kirchhoff's current law and Kirchhoff's voltage law are used to calculate the current and voltage to obtain the electrical data under fault conditions; By minimizing the sum of squares of current and voltage changes before and after the fault, the current and voltage of the virtual bus are solved, so as to preliminarily infer the fault location; Based on the preliminary inference results, the location of the virtual busbar is further refined within the fault area, and more virtual busbars are added at important nodes; Combined with the current and voltage data of the virtual bus, the location of the fault can be accurately determined.
7. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 6, characterized in that: The positive sequence Thevenin equivalent impedance calculation formula is specifically: in, , They represent the changes of positive sequence voltage and current at the power bus due to the fault, respectively. , .
8. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 7, characterized in that: The symmetrical component method is used to decompose the collected current and voltage data into positive sequence, negative sequence and zero sequence components, and extract the positive sequence component. The specific calculation formula is: in, , represents the positive sequence component of current, Represents the voltage positive sequence component.
9. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 8, characterized in that: The specific calculation formula of the positive sequence bus impedance matrix is as follows: in, is the positive-sequence bus impedance matrix, n is the total number of grid power sources, Zjj and Zij are self-impedance and mutual impedance respectively. When unit current is injected into bus j and the injected current of other buses is zero, the voltage on bus j is the self-impedance Zjj, and the voltage on bus i (i=1,2,…,n,i≠j) is the mutual impedance Zij between bus i and bus j.
10. The method for accurately locating faults in a multi-source distribution network based on positive sequence components according to claim 9, characterized in that: The positive sequence voltage change at the fault location is calculated based on the comprehensive fault index, the positive sequence component of the fault current and the positive sequence bus impedance according to a preset formula, and the calculation formula is as follows: in, .