A power distribution network branch line type parameter calculation method based on fault recording data

Abstract

This invention discloses a method for calculating parameters of distribution networks with branch lines based on fault recording data. The method includes: installing an electrical quantity acquisition device on each segment of the line under test with branch connections; classifying the line into two types based on the installation location of the electrical quantity acquisition devices; filtering the cycle data after the fault characteristics appear in the fault recording using the full-cycle Fourier algorithm; converting the measured three-phase electrical components on each line segment into sequence components using the symmetrical component method; substituting the electrical quantities at each location into the corresponding line parameter calculation equations according to the line type to generate a nonlinear equation set; and calculating the line parameters using the Levenberg-Marquardt nonlinear problem-solving method. This invention solves the problem of parameter calculation for branch lines with two line types when the number of measurement points in the distribution network is limited. This method is unaffected by fault location and fault distance and has high accuracy.

Description

Technical Field

[0001] This invention belongs to the field of power system protection and control, and specifically relates to a method for calculating parameters of a distribution network including branch lines based on fault recording data. Technical Background

[0002] Transmission lines are a crucial component of power networks, playing a vital role in delivering electricity from power plants to end users. Timely and accurate determination of line parameters helps in describing a more realistic power network model, enabling a series of power system analyses and calculations, such as power system segment location and fault location. In recent years, with the rapid development of power systems and urban scale, and the widespread application of new energy sources, the proportion of distributed generation (DG) in the power grid has been continuously increasing. This has led to increasingly complex layouts of transmission lines in distribution networks, placing higher demands on the feasibility and accuracy of transmission line parameter calculations.

[0003] Traditional line parameter determination mainly relies on theoretical calculations or offline measurements based on given physical property data of power equipment materials. However, with increasing power grid complexity and environmental interference, traditional methods face numerous limitations. In recent years, the widespread installation of Phaser Measurement Units (PMUs) in power grids and the increasingly sophisticated deployment of Wide-Area Measurement Systems (WAMS) have provided a wealth of high-accuracy information essential for power system analysis, creating favorable conditions for research on line parameters. Currently, related research focuses on parameter estimation for branchless lines, typically using dual-end synchronization measurement information as known quantities in calculations. Some literature proposes methods based on asynchronous data alignment to obtain dual-end synchronization information.

[0004] In distribution networks, T-connection refers to branching off from a line supplying power from one location to another, thereby achieving the purpose of supplying power to a third party. Branch connection technology, represented by T-connection, has advantages such as simplicity and short construction cycle, and is therefore widely used in distribution networks. However, there is currently limited literature on parameter calculation for lines with branches. One significant challenge lies in the large number of unknowns to be measured, requiring specific methods to construct equations for solution. Some existing methods increase the number of equations by de-energizing and energizing different lines, adding independent measurement methods. However, in actual power grids, the intermingling of old and new grids leads to complex wiring, and the demands of load requirements make it almost impossible to measure the mutual inductance parameters of lines during power outages. Considering the rich sequence component characteristics of historical fault recording data, steady-state methods can function reliably in most cases, and fault recording devices are more widely distributed in distribution networks than PMU devices. Therefore, researching steady-state methods for parameter calculation based on fault characteristics in fault recording information and the widely used branch connection structures in actual distribution networks has significant theoretical and practical implications. Summary of the Invention

[0005] The purpose of this application is to provide a parameter calculation method for distribution network types including branch lines based on fault recording data, which solves the parameter calculation problem for two line types including branch lines when the number of measurement points in the distribution network is limited, and has high accuracy.

[0006] This invention is achieved through the following technical solution: a method for calculating parameters of a distribution network including branch line types based on fault recording data, comprising:

[0007] S1: Install an electrical quantity acquisition device on each segment of the circuit under test, which includes branch connections;

[0008] S2: Based on the installation location of the electrical quantity acquisition device, there are two types of lines;

[0009] S3: The full-cycle Fourier algorithm is used to filter the cycle data after the fault characteristics appear in the fault recording.

[0010] S4: The measured electrical three-phase components on each line segment are converted into sequence components using the symmetrical component method;

[0011] S5: Substitute the electrical quantities at each point into the corresponding line parameter calculation equations according to the line type to generate a nonlinear equation set;

[0012] S6: The line parameters are calculated using the Levenberg-Marquardt nonlinear problem-solving method.

[0013] In one possible implementation, the electrical quantity acquisition device installed on each line segment includes the ability to measure phase voltage and phase current, and also has the ability to measure, record waveforms, and transmit data.

[0014] In one possible implementation, the fault conditions include: when there are multiple outgoing lines on the busbar, some lines experience asymmetrical faults, including five types of faults: single-phase short-circuit ground fault, two-phase short-circuit ground fault, two-phase short-circuit fault, two-phase open-circuit fault, and single-phase open-circuit fault; when a short-circuit fault occurs, the fault point and the ground are either metallic grounded or grounded through a transition resistor.

[0015] In one possible implementation, the line type includes: Line type 1 - a line with branches in which the acquisition devices on two sections are installed at a certain distance from the branch node, and the acquisition device on the other section is installed near the branch node exit position; Line type 2 - a line with branches in which the acquisition devices on three sections are installed at a certain distance from the branch node.

[0016] In one possible implementation, the method for calculating parameters of a distribution network including branch line types based on fault recording data is characterized by the following filtering algorithm in S3:

[0017] Let the input signal be a periodic function, expressed as:

[0018]

[0019] In the formula: ω1 represents the fundamental angular frequency; M is the order of the highest harmonic contained in the signal; k is the harmonic order, representing the k-th harmonic; H Rk H represents the real part of the k-th harmonic component; Ik H represents the imaginary part of the k-th harmonic component; m0 This is the DC component, i.e., the zeroth harmonic;

[0020] Formulas for calculating the real and imaginary parts of the fundamental frequency component:

[0021]

[0022] In the formula: N represents the number of samples per fundamental frequency cycle.

[0023] In one possible implementation, the method for calculating parameters of a distribution network including branch lines based on fault recording data is characterized in that the formula for the symmetrical component method in S4 is as follows:

[0024]

[0025] In the formula: α=e i120° Indicates operators;

[0026] F1, F2, and F0 represent the positive sequence, negative sequence, and zero sequence components, with phase A as the reference phase.

[0027] F A F B F C This represents the three-phase components.

[0028] In one possible implementation, the method for calculating parameters of a distribution network including branch line types based on fault recording data is characterized in that the nonlinear equations for each line type are solved in S5 as follows:

[0029] For line type 1, solve for the line parameters per unit length of line 1 and line 2, and divide it into two cases: the line parameters per unit length of line 1 and line 2 are the same and different.

[0030] (1) Line 1 and Line 2 have the same line parameters per unit length. Solve the system of equations f1:

[0031]

[0032] In the formula: the parameter subscript i∈{1,2,3} corresponds to the three segment lines respectively; the subscript s∈{1,2,0} indicates the sequence network type, s=1 indicates positive sequence network, s=2 indicates negative sequence network, and s=0 indicates zero sequence network; This represents the voltage measured at the point furthest from the branch node (P side) on the i-th line in the S-sequence network. This represents the estimated voltage at the branch node (Q side) of the i-th line in an s-sequence network.

[0033] Solving this system of nonlinear complex equations will yield the line impedance Z per unit length. s1 Line impedance per unit length Ys1(Z) s1 =Z s2 Y s1 =Y s2 );

[0034] (2) Line 1 and Line 2 have different parameters per unit length. Solve the system of equations f2:

[0035]

[0036] In the formula: R si L si C si This represents the resistance, inductance, and capacitance parameters per unit length of the i-th line in an S-sequence network; ω represents the angular frequency, and B... si =ωC si X is the susceptance per unit length of the i-th line in an S-sequence network; si =ωL si Z represents the reactance per unit length of the i-th line in an S-sequence network. si =R si +jX siY represents the line impedance per unit length of the i-th line in an S-sequence network; si =jB si This represents the line impedance per unit length of the i-th line in an S-sequence network; l hi This represents the electrical length of the i-th line and serves as the line's name; This represents the voltage measured at the point furthest from the branch node (P side) on the i-th line in the S-sequence network. This represents the estimated voltage at the branch node (Q side) of the i-th line in an s-sequence network. This represents the current flowing through the measuring point at the location furthest from the branch node (P side) in the s-sequence network. Let represent the current estimate of the i-th line at the injection branch node (Q side) under the s-sequence network; Re(*) represents taking the real part of the complex number within the parentheses, and Im(*) represents taking the imaginary part of the complex number within the parentheses; matrix β si Determined by the voltage and current vectors obtained from measuring point P, Matrix V si

[0037]

[0038] Solving this system of six nonlinear equations using nonlinear methods will yield the desired line parameters R. s1 R s2 L s1 L s2 C s1 C s2 ;

[0039] For line type 2, assuming the line parameters per unit length are the same for all three lines (line 1, line 2, and line 3), calculate the line parameter Z per unit length. s Y s According to KCL and KVL, there are six ways to write a system of equations:

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046] The solutions to equation systems ①, ③, and ⑤ are the same, as are the solutions to equation systems ②, ④, and ⑥. The solution to equation system ① is as follows:

[0047] ① Taking the equality of branch node voltages derived from section line 1 and section line 2 as the first equation, and the equality of branch node voltages derived from section line 1 and section line 3 as the second equation, the resulting system of equations f3 is shown below:

[0048]

[0049] Solve the nonhomogeneous nonlinear equation system:

[0050]

[0051] make

[0052]

[0053] Solving this system of nonlinear equations using a nonlinear solution method yields Z. s Y s The solutions to equations ③ and ⑤ can be deduced similarly.

[0054] The solution to system of equations ② is as follows:

[0055] ② Taking the equality of the branch node voltages derived from section line 1 and section line 2 as the first equation, and the sum of the currents flowing to the branch nodes as zero as the second equation, the resulting system of equations f4 is shown below:

[0056]

[0057] Rearranging the terms, we obtain the nonlinear equation system:

[0058]

[0059] make

[0060]

[0061] Substituting into the system of equations, we get:

[0062]

[0063] in:

[0064]

[0065]

[0066]

[0067] Solving this quadratic equation using a nonlinear method, and discarding solutions whose real and imaginary parts are less than or equal to zero, yields Z. s Substitute these equations back into the system of equations to obtain Y. s The solutions to equations ④ and ⑥ follow the same principle.

[0068] In one possible implementation, the Levenberg-Marquardt nonlinear problem solving method is implemented as follows:

[0069] Step 1: Determine the nonlinear problem model F, F∈{f1,f2,f3,f4}. Let k=0, choose an initial point x0, and select parameters ε, μ0, γ1, γ2, λ1, λ2 such that...

[0070] 0<ε<1,μ0>0,0<γ1<1<γ2,0<λ1≤λ2≤1

[0071] Step 2: Calculate x = x k The function value F(x) at time k ) and Jacobian matrix J(x k );

[0072] Step 3: Determine ||J(x) k ) T F(x k If ε ≤ ε is true, the process ends; otherwise, proceed to the next step.

[0073] Step 4: Calculation

[0074] d k (μ k )=-[J(x k ) T J(x k )+μ k I] -1 J(x k ) T F(x k )

[0075] Step 5: Calculation

[0076]

[0077] Step 6: Determine ρ k (d k (μ k ),μ k If η < 1, then take μ. k+1 =γ2μ k If λ1≤ρ k (d k (μ k ),μ k If ) < λ2 holds, then take μ. k+1 =μ k If η2≤ρ k (d k (μ k),μ k If ) holds true, then take μ. k+1 =γ1μ k ;

[0078] Step 7: Take x k+1 =x k +d k (μ k Increment the count of k by one and return to step one;

[0079] When J(x) is Lipschitz continuous and J(x) * When the expression is non-singular, the algorithm converges quadratically.

[0080] Compared with the prior art, the present invention has the following beneficial effects:

[0081] This application utilizes voltage and current information from a single measuring point on each segment of a distribution network containing branch lines after a fault occurs, solving the parameter calculation problem for two types of line lines with branch lines when the number of measuring points in the distribution network is limited. This method is unaffected by fault location or distance and has high accuracy. Attached Figure Description

[0082] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0083] Figure 1 This is a flowchart illustrating a method for calculating parameters of a distribution network, including branch line types, based on fault recording data, as provided in an embodiment of this application.

[0084] Figure 2 A circuit model diagram with branch wiring provided for an embodiment of this application.

[0085] Figure 3 A model diagram of a branch connection line (line type 1) with measuring point locations provided in the embodiments of this application.

[0086] Figure 4 A model diagram of a branch connection line (line type 2) with measuring point locations provided in the embodiments of this application.

[0087] Figure 5 A flowchart of the method for solving LM nonlinear problems provided in this application embodiment. Detailed Implementation

[0088] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0089] like Figure 1 As shown, this application provides a method for calculating parameters of a distribution network with branch lines based on fault recording data, utilizing voltage and current information from a measuring point on each segment of the distribution network after a fault occurs. The method includes:

[0090] A method for calculating parameters of a distribution network including branch lines based on fault recording data includes the following steps:

[0091] S1: Install an electrical quantity acquisition device on each segment of the circuit under test, which includes branch connections;

[0092] S2: Based on the installation location of the electrical quantity acquisition device, there are two types of lines;

[0093] S3: The full-cycle Fourier algorithm is used to filter the cycle data after the fault characteristics appear in the fault recording.

[0094] S4: The measured electrical three-phase components on each line segment are converted into sequence components using the symmetrical component method;

[0095] S5: Substitute the electrical quantities at each point into the corresponding line parameter calculation equations according to the line type to generate a nonlinear equation set;

[0096] S6: The line parameters are calculated using the Levenberg-Marquardt nonlinear problem-solving method.

[0097] This application utilizes voltage and current information from a single measuring point on each segment of a distribution network containing branch lines after a fault occurs, solving the parameter calculation problem for two types of line lines with branch lines when the number of measuring points in the distribution network is limited. This method is unaffected by fault location or distance and has high accuracy.

[0098] In one possible implementation, the electrical quantity acquisition device installed on each section of the line containing branch lines includes the ability to measure phase voltage and phase current, and also has the ability to measure waveforms and transmit data.

[0099] like Figure 2 The diagram shown is a circuit model diagram with branch connections provided in this application embodiment. The diagram contains a branch node connecting three π-shaped circuit lumped parameter models of unequal lengths.

[0100] In one possible implementation, the fault conditions include: when there are multiple outgoing lines on the busbar, some lines experience asymmetrical faults, including five types of faults: single-phase short-circuit ground fault, two-phase short-circuit ground fault, two-phase short-circuit fault, two-phase open-circuit fault, and single-phase open-circuit fault; when a short-circuit fault occurs, the fault point and the ground are either metallic grounded or grounded through a transition resistor.

[0101] In one possible implementation, the line type includes: Line type 1 - a line with branches in which the acquisition devices on two sections are installed at a certain distance from the branch node, and the acquisition device on the other section is installed near the branch node exit position; Line type 2 - a line with branches in which the acquisition devices on three sections are installed at a certain distance from the branch node.

[0102] like Figure 3 The diagram shows a model of a branch connection line (line type 1) with measurement point locations provided in this application embodiment. In the diagram, the parameter subscripts i∈{1,2,3} correspond to the three line segments respectively; the subscripts s∈{1,2,0} indicate the sequence network type, s=1 indicates a positive sequence network, s=2 indicates a negative sequence network, and s=0 indicates a zero sequence network. This represents the voltage measured at the point furthest from the branch node (P side) on the i-th line in the S-sequence network. This represents the current flowing through the measuring point at the point furthest from the branch node (P side) of the i-th line in the s-sequence network; This represents the estimated voltage at the branch node for the i-th line in an s-sequence network. This represents the current estimate of the i-th line at the injected branch node in an s-sequence network; l hi The electrical length of the i-th line is indicated and used as the line's name; a measuring point is set on each line, and the location of the measuring point is marked on the diagram in the form of a meter; line branches l h3 For load branch; R si L si C si Z represents the resistance, inductance, and capacitance per unit length of the i-th line in an s-sequence network. si =R si +jωL si Y represents the line impedance per unit length of the i-th line in an s-sequence network; si =jωC si This represents the line admittance per unit length of the i-th line in an s-type sequence network.

[0103] like Figure 4 The diagram shown is a model of a branch connection line (line type 2) with measuring point locations provided in this application embodiment. Figure 1 hiRepresents the electrical length of the i-th line and serves as the line's name; one measuring point is set on each line, and the location of the measuring point is marked on the diagram in the form of a meter; R si L si C si Z represents the resistance, inductance, and capacitance per unit length of the i-th line in an s-sequence network. si =R si +jωL si Y represents the line impedance per unit length of the i-th line in an s-sequence network; si =jωC si This represents the line admittance per unit length of the i-th line in an s-type sequence network.

[0104] In one possible implementation, the method for calculating parameters of a distribution network including branch line types based on fault recording data is characterized by the following filtering algorithm in S3:

[0105] Let the input signal be a periodic function, expressed as:

[0106]

[0107] In the formula: ω1 represents the fundamental angular frequency; M is the order of the highest harmonic contained in the signal; k is the harmonic order, representing the k-th harmonic; H Rk H represents the real part of the k-th harmonic component; Ik H represents the imaginary part of the k-th harmonic component; m0 This is the DC component, i.e., the zeroth harmonic;

[0108] Formulas for calculating the real and imaginary parts of the fundamental frequency component:

[0109]

[0110] In the formula: N represents the number of samples per fundamental frequency cycle.

[0111] In one possible implementation, the method for calculating parameters of a distribution network including branch lines based on fault recording data is characterized in that the formula for the symmetrical component method in S4 is as follows:

[0112]

[0113] In the formula: α=e i120° Indicates operators;

[0114] F1, F2, and F0 represent the positive sequence, negative sequence, and zero sequence components, with phase A as the reference phase.

[0115] F A F B F CThis represents the three-phase components.

[0116] In one possible implementation, the method for calculating parameters of a distribution network including branch line types based on fault recording data is characterized in that the nonlinear equations for each line type are solved in S5 as follows:

[0117] For line type 1, solve for the line parameters per unit length of line 1 and line 2, and divide it into two cases: the line parameters per unit length of line 1 and line 2 are the same and different.

[0118] (1) Line 1 and Line 2 have the same line parameters per unit length. Solve the system of equations f1:

[0119]

[0120] In the formula: the parameter subscript i∈{1,2,3} corresponds to the three segment lines respectively; the subscript s∈{1,2,0} indicates the sequence network type, s=1 indicates positive sequence network, s=2 indicates negative sequence network, and s=0 indicates zero sequence network; This represents the voltage measured at the point furthest from the branch node (P side) on the i-th line in the S-sequence network. This represents the estimated voltage at the branch node (Q side) of the i-th line in an s-sequence network.

[0121] Solving this system of nonlinear complex equations will yield the line impedance Z per unit length. s1 Line impedance per unit length Ys1(Z) s1 =Z s2 Y s1 =Y s2 );

[0122] (2) Line 1 and Line 2 have different parameters per unit length. Solve the system of equations f2:

[0123]

[0124] In the formula: R si L si C si This represents the resistance, inductance, and capacitance parameters per unit length of the i-th line in an S-sequence network; ω represents the angular frequency, and B... si =ωC si X is the susceptance per unit length of the i-th line in an S-sequence network; si =ωL si Z represents the reactance per unit length of the i-th line in an S-sequence network. si =R si +jX si Y represents the line impedance per unit length of the i-th line in an S-sequence network; si =jB siThis represents the line impedance per unit length of the i-th line in an S-sequence network; l hi This represents the electrical length of the i-th line and serves as the line's name; This represents the voltage measured at the point furthest from the branch node (P side) on the i-th line in the S-sequence network. This represents the estimated voltage at the branch node (Q side) of the i-th line in an s-sequence network. This represents the current flowing through the measuring point at the location furthest from the branch node (P side) in the s-sequence network. Let represent the current estimate of the i-th line at the injection branch node (Q side) under the s-sequence network; Re(*) represents taking the real part of the complex number within the parentheses, and Im(*) represents taking the imaginary part of the complex number within the parentheses; matrix β si Determined by the voltage and current vectors obtained from measuring point P, Matrix V si

[0125]

[0126] Solving this system of six nonlinear equations using nonlinear methods will yield the desired line parameters R. s1 R s2 L s1 L s2 C s1 C s2 ;

[0127] For line type 2, assuming the line parameters per unit length are the same for all three lines (line 1, line 2, and line 3), calculate the line parameter Z per unit length. s Y s According to KCL and KVL, there are six ways to write a system of equations:

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134] The solutions to equation systems ①, ③, and ⑤ are the same, as are the solutions to equation systems ②, ④, and ⑥. The solutions to combinations ① and ② will be explained in detail below. The solutions to the other four equation systems are similar to these two combinations and will not be elaborated on further.

[0135] The solution to system of equations ① is as follows:

[0136] ① Taking the equality of branch node voltages derived from section line 1 and section line 2 as the first equation, and the equality of branch node voltages derived from section line 1 and section line 3 as the second equation, the resulting system of equations f3 is shown below:

[0137]

[0138] Solve the nonhomogeneous nonlinear equation system:

[0139]

[0140] make

[0141]

[0142] Solving this system of nonlinear equations using a nonlinear solution method yields Z. s Y s The solutions to equations ③ and ⑤ can be deduced similarly.

[0143] The solution to system of equations ② is as follows:

[0144] ② Taking the equality of the branch node voltages derived from section line 1 and section line 2 as the first equation, and the sum of the currents flowing to the branch nodes as zero as the second equation, the resulting system of equations f4 is shown below:

[0145]

[0146] Rearranging the terms, we obtain the nonlinear equation system:

[0147]

[0148] make

[0149]

[0150] Substituting into the system of equations, we get:

[0151]

[0152] in:

[0153]

[0154]

[0155]

[0156] Solving this quadratic equation using a nonlinear method, and discarding solutions whose real and imaginary parts are less than or equal to zero, yields Z. s Substitute these equations back into the system of equations to obtain Y. sThe solutions to equations ④ and ⑥ follow the same principle.

[0157] like Figure 5 The flowchart shown is a method for solving Levenberg-Marquardt nonlinear problems provided in this application. The method for solving Levenberg-Marquardt nonlinear problems can be mainly divided into three parts: the first part is initial assignment, the second part is iterative calculation, and the third part is iterative adjustment.

[0158] In one possible implementation, the specific steps of the Levenberg-Marquardt nonlinear problem solving method are as follows:

[0159] Step 1: Determine the nonlinear problem model F, F∈{f1,f2,f3,f4}. Let k=0, choose an initial point x0, and select parameters ε, μ0, γ1, γ2, λ1, λ2 such that...

[0160] 0<ε<1,μ0>0,0<γ1<1<γ2,0<λ1≤λ2≤1

[0161] Step 2: Calculate x = x k The function value F(x) at time k ) and Jacobian matrix J(x k );

[0162] Step 3: Determine ||J(x) k ) T F(x k If ε ≤ ε is true, the process ends; otherwise, proceed to the next step.

[0163] Step 4: Calculation

[0164] d k (μ k )=-[J(x k ) T J(x k )+μ k I] -1 J(x k ) T F(x k )

[0165] Step 5: Calculation

[0166]

[0167] Step 6: Determine ρ k (d k (μ k ),μ k If η < 1, then take μ. k+1 =γ2μ kIf λ1≤ρ k (d k (μ k ),μ k If ) < λ2 holds, then take μ. k+1 =μ k If η2≤ρ k (d k (μ k ),μ k If ) holds true, then take μ. k+1 =γ1μ k ;

[0168] Step 7: Take x k+1 =x k +d k (μ k Increment the count of k by one and return to step one;

[0169] When J(x) is Lipschitz continuous and J(x) * When the expression is non-singular, the algorithm converges quadratically.

[0170] This application provides a parameter calculation method for distribution networks including branch lines based on fault recording data. It employs the LM algorithm and the full-cycle Fourier algorithm, using fault recording data to construct a system of nonlinear equations, and solves for the line parameters of some lines and the positive-sequence and zero-sequence parameters of all lines. Simulation results show that the relative errors of parameter calculations using recording data from different faults meet the measurement accuracy requirements of engineering projects.

[0171] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for calculating parameters of a distribution network including branch line types based on fault recording data, comprising the following steps: S1: An electrical quantity acquisition device is installed on each segment of the line under test, which includes branch connections. The electrical quantity acquisition device has the ability to measure phase voltage and phase current, as well as the ability to measure waveforms and transmit data. S2: Based on the installation location of the electrical quantity acquisition device, there are two types of lines: Line Type 1: Includes branch lines, where the data acquisition devices on two sections of the line are installed at a certain distance from the branch nodes, and the data acquisition device on the other section of the line is installed near the branch node outlet. Line Type 2: The data acquisition devices on the three-segment line containing branch lines are installed at a certain distance from the branch nodes; S3: The full-cycle Fourier algorithm is used to filter the cycle data after the fault characteristics appear in the fault recording, and the fundamental phasors of the three-phase voltage and three-phase current at each measuring point are extracted. S4: The fundamental phasors of the three-phase voltage and three-phase current on each line segment are converted into sequence components using the symmetrical component method. S5: Based on the alignment type, substitute the sequence components at each location into the corresponding line parameter calculation equations to generate a system of nonlinear equations, where: For line type 1, if the parameters per unit length of the branch lines are the same, then the equation system is written based on the voltage consistency condition of the branch nodes; if the parameters per unit length of the branch lines are different, then the six-variable nonlinear equation system is written based on the voltage-current propagation relationship and the node current continuity condition. For line type 2, under the condition that the parameters of the three line segments are the same, the conditions that the branch node voltages are equal and / or the sum of the currents is zero are written based on the KVL and KCL laws, which are reduced to a set of two nonlinear equations of impedance per unit length and admittance per unit length. S6: Solve the nonlinear equations using the Levenberg-Marquardt method to obtain the line parameters, which include resistance per unit length, inductance per unit length, and capacitance per unit length.

2. The parameter calculation method for distribution networks including branch line types based on fault recording data according to claim 1, characterized in that, The fault conditions include: when there are multiple outgoing lines on the busbar, some lines experience asymmetrical faults, including five types of faults: single-phase short-circuit ground fault, two-phase short-circuit ground fault, two-phase short-circuit fault, two-phase open circuit fault, and single-phase open circuit fault; when a short-circuit fault occurs, the fault point and the ground are either metallic grounded or grounded through a transition resistor.

3. The parameter calculation method for distribution networks including branch line types based on fault recording data according to claim 1, characterized in that, The filtering algorithm in S3 is as follows: Let the input signal be a periodic function, expressed as: In the formula: Indicates the fundamental angular frequency; The order of the highest harmonic contained in the signal; Let be the harmonic order, representing the th harmonic. Second harmonics; For the first The real part of the second harmonic component; For the first The imaginary part of the second harmonic component; This is the DC component, i.e., the zeroth harmonic; Formulas for calculating the real and imaginary parts of the fundamental frequency component: In the formula: This represents the number of samples per fundamental frequency cycle.

4. The parameter calculation method for distribution networks including branch line types based on fault recording data according to claim 1, characterized in that, The formula for calculating the symmetric component method in S4 is as follows: In the formula: Indicates operators; ; Represents the positive sequence, negative sequence, and zero sequence components, with phase A as the reference phase; This represents the three-phase components.

5. The parameter calculation method for distribution networks including branch line types based on fault recording data according to claim 1, characterized in that, The specific process of solving the nonlinear equations for each line type in S5 is as follows: For line type 1, solve for the line parameters per unit length of line 1 and line 2, dividing the problem into two cases: whether the line parameters per unit length of line 1 and line 2 are the same or different. (1) Line 1 and Line 2 have the same line parameters per unit length. Solve the system of equations. : Where: parameter subscript These correspond to three different line sections; subscript Indicates the sequence net type, Indicates the orthogonal sequence network. Represents the negative order network. Represents a zero-order network; express Type sequence network under the first An estimate of the voltage at a branch node of a line; Solving this system of nonlinear complex equations will yield the line impedance per unit length. Line admittance per unit length ; (2) The line parameters per unit length are different for Line 1 and Line 2. Solve the system of equations. : In the formula: express Type sequence network under the first The resistance, inductance, and capacitance parameters per unit length of the line; Represents angular frequency. for Type sequence network under the first Susceptivity per unit length of the line; for Type sequence network under the first Reactance per unit length of the line; express Type sequence network under the first Line impedance per unit length; express Type sequence network under the first Line admittance per unit length of line; Indicates the first The electrical length of each line is used as the name of the line; express Type sequence network under the first Voltage measured at points far from branch nodes on the line; express Type sequence network under the first An estimate of the voltage at a branch node of a line; express Type sequence network under the first The current flowing through the measuring point at a point on the line far from the branch node. express Type sequence network under the first The current estimate at the injection branch node of the line; This indicates taking the real part of the complex number inside the parentheses. This indicates taking the imaginary part of the complex number within the parentheses; matrix Determined by the voltage and current vectors obtained from measuring point P, ;matrix Solving this system of six nonlinear equations using nonlinear methods will yield the parameters of the line to be determined. , , ; For line type 2, assuming the line parameters per unit length are the same for all three lines (line 1, line 2, and line 3), calculate the line parameters per unit length. , According to KCL and KVL, there are six ways to write a system of equations: ① ② ③ ④ ⑤ ⑥ The solutions to equation systems ①, ③, and ⑤ are the same, as are the solutions to equation systems ②, ④, and ⑥. The solution to equation system ① is as follows: ①The system of equations formed by taking the equality of branch node voltages derived from section line 1 and section line 2 as the first equation, and the equality of branch node voltages derived from section line 1 and section line 3 as the second equation. As shown below: Solve the nonhomogeneous nonlinear equation system: In the formula: express Type sequence network under the first Voltage measured at points far from branch nodes on the line; make Solving this system of nonlinear equations using nonlinear solution methods yields... , The solutions to equations ③ and ⑤ can be deduced similarly. The solution to system of equations ② is as follows: ②The system of equations formed by taking the equality of the branch node voltages derived from section line 1 and section line 2 as the first equation and the sum of the currents flowing to the branch nodes as zero as the second equation. As shown below: Rearranging the terms, we obtain a system of nonlinear equations: make Substituting into the system of equations, we get: in: Solving this quadratic equation using a nonlinear method, and discarding solutions whose real and imaginary parts are less than or equal to zero, yields the solution. Substituting back into the system of equations, we get... The solutions to equations ④ and ⑥ follow the same principle.

6. The parameter calculation method for distribution networks including branch line types based on fault recording data according to claim 1, characterized in that, The implementation steps of the Levenberg-Marquardt nonlinear problem-solving method in S6 are as follows: Step 1: Identify the nonlinear problem model , ;make Select initial point , get parameters , , , , , Make Step 2: Calculation function value at time and Jacobian matrix ; Step 3: Judgment Check if it is true; if true, end; otherwise, proceed to the next step. Step 4: Calculation Step 5: Calculation Step 6: Judgment If it is true, then take it. ;like If it is true, then take ;like If it is true, then take ; Step 7: Take ,make Increment the counter by one and return to step one; when Lipschitz continuous and When the expression is non-singular, the algorithm converges quadratically.

Images