A method for identifying distribution network line parameters taking into account ground capacitance and line length estimation

Abstract

The present invention discloses a method for identifying the line parameters of a distribution network taking into account the ground capacitance and the line length estimation, comprising the following steps: 1) obtaining basic data of the power grid; 2) constructing a multivariate nonlinear voltage drop equation for a distribution transformer; 3) constructing a multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation; 4) recursively calculating the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation to obtain the line parameters of the distribution network. The present invention adopts a method based on line length estimation, and identifies the specific values ​​of R and X to identify the line length, so that the multi-solution problem is solved. In addition, because the cable rate of the urban power grid is high, the ground capacitance should not be ignored. This method takes into account the ground capacitance and is suitable for parameter estimation of cable lines.

Description

Technical Field

[0001] The present invention relates to the field of distribution network parameter identification, and in particular to a distribution network line parameter identification method taking into account ground capacitance and line length estimation. Background Art

[0002] Distributed power sources, electric vehicles, and user-side energy storage are being connected to the distribution network on a large scale, posing new challenges to the safety and reliability of distribution network planning and operation. In order to cope with the randomness and volatility brought about by the access of distributed power sources and electric vehicles, it is necessary to reconstruct the topology and intelligently dispatch the distribution network in real time to achieve safe operation of the distribution network. It is necessary to carry out more refined reactive power control to ensure the quality of power, which needs to be based on a more accurate judgment of the distribution network topology and line parameters. The operation state estimation and optimization of the distribution network also require accurate judgment of the topology and parameter information. Therefore, refined topology and line parameter information are prerequisites for high-order optimization of the distribution network.

[0003] At present, many studies are unable to identify line parameters and require voltage phase angle information. However, for my country's actual distribution network, the installation of synchronous phase angle measurement units (PMUs) is limited, and the data volume to support the method is insufficient.

[0004] The traditional distribution network line parameter identification method has the following main disadvantages: the traditional parameter identification method often uses nonlinear voltage drop equations to identify the topological relationship and parameters of each node. However, because the solution parameters include two parameters, R and X, it is easy to fall into the problem of multiple solutions, so that the correct R and X values ​​cannot be obtained, and it is difficult to achieve good results. Summary of the invention

[0005] The object of the present invention is to provide a method for identifying line parameters of a distribution network taking into account the ground capacitance and considering the line length estimation, comprising the following steps:

[0006] 1) Obtain basic data of the power grid;

[0007] The basic data of the power grid include the topological structure of the power grid, the number of observable nodes N obs , the active power measurement of the node P i , the reactive power measurement Q of the node i , the voltage amplitude measurement of the node V i .

[0008] 2) Construct the multivariate nonlinear voltage drop equation of distribution transformer;

[0009] The steps of constructing the multivariate nonlinear voltage drop equation of distribution transformer include:

[0010] 2.1) Establish the relationship between the starting voltage V0 and the terminal voltage V1 and the terminal voltage V2, that is:

[0011]

[0012] Wherein, P1 and P2 are the active powers of the terminal nodes 1 and 2 to be determined respectively; Q1 and Q2 are the reactive powers of the terminal nodes 1 and 2 to be determined respectively; R1 and R2 are the equivalent resistances of the terminal nodes 1 and 2 to be determined respectively; X1 and X2 are the equivalent reactances of the terminal nodes 1 and 2 to be determined respectively;

[0013] 2.2) According to formula (1), establish the accurate relationship between the electrical parameters of the parallel node and the terminal node 1 and the terminal node 2 to be determined, that is:

[0014]

[0015] In the formula, the parameters f1(R1, X1) and f2(R1, X1) are as follows:

[0016]

[0017] 2.3) Establish the connection criterion between any branch end node i and branch end node j at N time points, that is:

[0018]

[0019] In the formula, R i , R j are the equivalent resistances of branch end nodes i and j respectively; X i , X j are the equivalent reactances of branch end node i and branch end node j respectively.

[0020] 3) Construct a multivariate nonlinear voltage drop equation that takes into account the ground capacitance and line length estimation;

[0021] The steps to construct the multivariate nonlinear voltage drop equation taking into account the capacitance to ground and considering the line length estimation include:

[0022] 3.1) Establish the voltage drop equation between two nodes after taking into account the capacitance to ground, that is:

[0023]

[0024] In the formula, V0 is the starting voltage, V1 and V2 are the terminal voltages to be determined; Y1 and Y2 are the admittances;

[0025] 3.2) Taking voltage V1, voltage V2, active power P1, active power P2, reactive power Q1, reactive power Q2 as known quantities, and resistance R1, reactance X1, resistance R2, reactance X2, susceptance B1, susceptance B2 as estimated quantities to be determined, substitute the known quantities into formula (1) to obtain:

[0026]

[0027] 3.3) Establish the connection criterion between any branch end node i and branch end node j at N time points, namely:

[0028]

[0029] In the formula, f i (R i ,X i ,Y i ,V i ), f j (R j ,X j ,Y j ,V j ) is the connection criterion parameter;

[0030] 3.4) Substituting resistance, reactance, and susceptance by unit length multiplied by line length, we get:

[0031]

[0032] In the formula, They represent the unit equivalent resistance of branch end node i and branch end node j respectively; They represent the unit equivalent reactance of branch end node i and branch end node j respectively; They represent the unit equivalent susceptance of branch end node i and branch end node j respectively; B i , B j They represent the equivalent susceptance of branch end node i and branch end node j respectively; L i , L j Indicates the line length; R i , R j are the equivalent resistances of branch end nodes i and j respectively; X i , X j are the equivalent reactances of branch end node i and branch end node j respectively;

[0033] 3.5) Substituting formula (11) into formula (10), we get the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation, namely:

[0034]

[0035] 4) Recursively calculate the multivariate nonlinear voltage drop equation taking into account the ground capacitance and line length estimation to obtain the distribution network line parameters.

[0036] The distribution network line parameters include the feeder end branch Z end The state variable U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end , Feeder middle branch Z mid The state variable U mid ,U mid+1 ,P mid+1 ,Q mid+1 . Feeder end branch Y end Active power and reactive power at the head end; P end ,Q end Feeder end branch Y end Active power and reactive power at the end.

[0037] The steps of recursively calculating the multivariate nonlinear voltage drop equation taking into account the capacitance to ground and considering the line length estimation include:

[0038] 4.1) Measure the feeder end branch Z end Power quantity measurement U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end , and the feeder end branch Z is calculated based on the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation. end The resistance R end Reactance X end and electrosusceptor B end Among them, U mid+1 , U end is voltage; P mid+1 , P end is the active power; Q mid+1 , Q end is the reactive power;

[0039] 4.2) Calculate the feeder end branch Z end Active power at the head end and reactive power Right now:

[0040]

[0041] 4.3) Active power and reactive power Replace active power P mid+1 and reactive power Q mid+1 , from the feeder end branch Z end At the beginning, parameter estimation and recursive calculation of loop variables are performed from bottom to top to obtain the topology and branch parameter information of the entire network.

[0042] The technical effect of the present invention is unquestionable. The present invention adopts a linear length estimation method, and identifies the specific values ​​of R and X instead of identifying their line lengths, so that the multiple solution problem is solved. In addition, because the cable rate of urban power grids is high, the ground capacitance should not be ignored. This method takes the ground capacitance into consideration and is suitable for parameter estimation of cable lines. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is the phase diagram of line voltage drop;

[0044] Figure 2 It is the recursive calculation diagram of the multivariate linear regression model of the distribution transformer local variables;

[0045] Figure 3 is a method flow chart;

[0046] Figure 4 It is the IEEE-33 node system diagram;

[0047] Figure 5 This is the 33rds node system diagram;

[0048] Figure 6 This is the system diagram of the 69rd node;

[0049] In the figure, 1-69 represent nodes. DETAILED DESCRIPTION

[0050] The present invention is further described below in conjunction with the embodiments, but it should not be understood that the above subject matter of the present invention is limited to the following embodiments. Without departing from the above technical ideas of the present invention, various substitutions and changes are made according to the common technical knowledge and customary means in the art, which should all be included in the protection scope of the present invention.

[0051] Embodiment 1:

[0052] See also Figures 1 to 3 , a method for identifying line parameters of a distribution network taking into account ground capacitance and line length estimation comprises the following steps:

[0053] 1) Obtain basic data of the power grid;

[0054] The basic data of the power grid include the topological structure of the power grid, the number of observable nodes N obs , the active power measurement of the node Pi , the reactive power measurement Q of the node i , the voltage amplitude measurement of the node V i .

[0055] 2) Construct the multivariate nonlinear voltage drop equation of distribution transformer;

[0056] The steps of constructing the multivariate nonlinear voltage drop equation of distribution transformer include:

[0057] 2.1) Establish the relationship between the starting voltage V0 and the terminal voltage V1 and the terminal voltage V2, that is:

[0058]

[0059] Wherein, P1 and P2 are the active powers of the terminal nodes 1 and 2 to be determined respectively; Q1 and Q2 are the reactive powers of the terminal nodes 1 and 2 to be determined respectively; R1 and R2 are the equivalent resistances of the terminal nodes 1 and 2 to be determined respectively; X1 and X2 are the equivalent reactances of the terminal nodes 1 and 2 to be determined respectively;

[0060] 2.2) According to formula (1), establish the accurate relationship between the electrical parameters of the parallel node and the terminal node 1 and the terminal node 2 to be determined, that is:

[0061]

[0062] In the formula, the parameters f1(R1, X1) and f2(R1, X1) are as follows:

[0063]

[0064] 2.3) Establish the connection criterion between any branch end node i and branch end node j at N time points, that is:

[0065]

[0066] In the formula, R i , R j are the equivalent resistances of branch end nodes i and j respectively; X i , X j are the equivalent reactances of branch end node i and branch end node j respectively.

[0067] 3) Construct a multivariate nonlinear voltage drop equation that takes into account the ground capacitance and line length estimation;

[0068] The steps to construct the multivariate nonlinear voltage drop equation taking into account the capacitance to ground and considering the line length estimation include:

[0069] 3.1) Establish the voltage drop equation between two nodes after taking into account the capacitance to ground, that is:

[0070]

[0071] In the formula, V0 is the starting voltage, V1 and V2 are the terminal voltages to be determined; Y1 and Y2 are the admittances; because the conductance is very small and can be ignored, the following approximation can be obtained: Y1=-jB1, Y2=-jB2.

[0072] 3.2) Taking voltage V1, voltage V2, active power P1, active power P2, reactive power Q1, reactive power Q2 as known quantities, and resistance R1, reactance X1, resistance R2, reactance X2, susceptance B1, susceptance B2 as estimated quantities to be determined, substitute the known quantities into formula (1) to obtain:

[0073]

[0074]

[0075] 3.3) Establish the connection criterion between any branch end node i and branch end node j at N time points, namely:

[0076]

[0077] In the formula, f i (R i ,X i ,Y i ,V i ), f j (R j ,X j ,Y j ,V j ) is the connection criterion parameter;

[0078] 3.4) Substituting resistance, reactance, and susceptance by unit length multiplied by line length, we get:

[0079]

[0080] In the formula, They represent the unit equivalent resistance of branch end node i and branch end node j respectively; They represent the unit equivalent reactance of branch end node i and branch end node j respectively; They represent the unit equivalent susceptance of branch end node i and branch end node j respectively; B i , B j They represent the equivalent susceptance of branch end node i and branch end node j respectively; L i , L j Indicates the line length; R i, R j are the equivalent resistances of branch end nodes i and j respectively; X i , X j are the equivalent reactances of branch end node i and branch end node j respectively;

[0081] 3.5) Substituting formula (11) into formula (10), we get the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation, namely:

[0082]

[0083] 4) Recursively calculate the multivariate nonlinear voltage drop equation taking into account the ground capacitance and line length estimation to obtain the distribution network line parameters.

[0084] The distribution network line parameters include the feeder end branch Z end The state variable U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end , Feeder middle branch Z mid The state variable U mid ,U mid+1 ,P mid+1 ,Q mid+1 . Feeder end branch Y end Active power and reactive power at the head end; P end ,Q end Feeder end branch Y end Active power and reactive power at the end.

[0085] The steps of recursively calculating the multivariate nonlinear voltage drop equation taking into account the capacitance to ground and considering the line length estimation include:

[0086] 4.1) Measure the feeder end branch Z end Power quantity measurement U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end , and the feeder end branch Z is calculated based on the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation. end The resistance R end Reactance X end and electrosusceptor B end Among them, U mid+1 , U end is voltage; P mid+1 , Pend is the active power; Q mid+1 , Q end is the reactive power;

[0087] 4.2) Calculate the feeder end branch Z end Active power at the head end and reactive power Right now:

[0088]

[0089] 4.3) Active power and reactive power Replace active power P mid+1 and reactive power Q mid+1 , from the feeder end branch Z end At the beginning, parameter estimation and recursive calculation of loop variables are performed from bottom to top to obtain the topology and branch parameter information of the entire network.

[0090] Embodiment 2:

[0091] See also Figures 1 to 3 , a method for identifying line parameters of a distribution network taking into account ground capacitance and line length estimation comprises the following steps:

[0092] 1) Obtain basic data of the power grid.

[0093] The basic data of the power grid include the topological structure of the power grid, the number of all observable nodes N obs , active power measurement P of all nodes i , the reactive power measurement Q of the node i , the voltage amplitude measurement of the node V i .

[0094] 2) Constructing the multivariate nonlinear voltage drop equation for distribution transformer

[0095] V0 is the starting voltage, and V1 and V2 are the terminal voltages to be determined. Figure 1 The line voltage drop phase diagram is shown, and the voltage amplitude relationship between nodes 0 and 1 is obtained as follows:

[0096]

[0097] Subtracting the above two equations, we can get the accurate relationship between the electrical parameters of the parallel node pair (1,2):

[0098]

[0099] According to the above relationship, the connection criterion of any line end node i, j at N time points is:

[0100]

[0101] 3) Construct a multivariate nonlinear voltage drop equation that takes into account the ground capacitance and line length estimation.

[0102] After taking into account the capacitance to ground Figure 1 The voltage drop equation between two nodes can be expressed as:

[0103]

[0104] V0 is the starting voltage, V1 and V2 are the terminal voltages to be determined. Y1 and Y2 are the admittances; since the conductance is very small and can be ignored, we can have the following approximation Y1 = -jB1, Y2 = -jB2.

[0105] Known quantities: V1, V2, P1, P2, Q1, Q2; estimated quantities: R1, X1, R2, X2, B1, B2; Substituting into (0.1) we get:

[0106]

[0107]

[0108] According to the above relationship, the connection criterion of any line end node i, j at N time points is:

[0109]

[0110] Resistance, reactance, and susceptance are replaced by unit length multiplied by line length, that is:

[0111]

[0112] Substituting into (10) we can obtain:

[0113]

[0114] In the actual operation of the distribution network, the line parameters R i ,X i ,R j ,X j ,B i ,B j Constant, line voltage amplitude and active and reactive power U i ,P i ,Q i ,U j ,P j ,Q j The local state variables of the distribution transformer fluctuate with the load. The normal measurement data U of multiple historical normal sections of the observable nodes of the distribution network can be used to i ,P i ,Q i ,Uj ,P j ,Q j For the distribution network line parameters R i ,X i ,R j ,X j ,B i ,B j Make an estimate.

[0115] 4) Recursive calculation of multivariate nonlinear voltage drop equation

[0116] like Figure 2 As shown in the figure, in the process of estimating the parameters of the multivariate nonlinear voltage drop equation, for the feeder end line parameter Z end , variable U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end It can be known from the measurements of distribution transformer mid+1 and distribution transformer end, and substituted into formula (12). The end line Z can be estimated end However, for the line parameter Z in the middle section of the feeder mid U mid ,U mid+1 It can be obtained from the measurement of distribution transformer mid and distribution transformer mid+1, and the feeder middle section line Z mid End measurement P mid+1 ,Q mid+1 Feeder end line Z needs to be superimposed end The power loss of the line cannot be directly related to Z mid To do this, we first need to estimate the parameters of the feeder end line Z end The power loss is calculated.

[0117] Due to the voltage of the two distribution transformers at the end of the line, the power measurement U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end First, perform the feeder end line Z end Parameter estimates of R end ,X end ,Z end Then calculate the feeder end line Z end Power at the head end As shown in the following formula, replace the original power P mid+1 ,Q mid+1 Then, the parameter estimation of each pair of lines described in step 4 is performed.

[0118]

[0119] Therefore, only the feeder end line Z end Starting from the bottom up, the topology and line parameter information of the whole network can be obtained by performing parameter estimation and recursive calculation step by step. The overall method flow is shown in Figure 3 shown.

[0120] Embodiment 3:

[0121] See also Figure 4 , the verification test of the distribution network line parameter identification method taking into account the ground capacitance and considering the line length estimation includes the following contents:

[0122] In order to verify the correctness and effectiveness of the distribution network line parameter identification proposed in Example 1-2 that takes into account the ground capacitance and considers the line length estimation, a simulation analysis is performed on the IEEE 33-node system. The rated voltage of the system is 12.66kV, and all the lines are cable lines. There are 31 load endpoints in total, with node 0 being the power supply point and node 5 being the unmeasured collection node. Among them, the load data uses the actual user data of a distribution network, which is normalized to the load level of the standard example of the 33-node system, retaining its load fluctuation characteristics. Then, the distribution network line parameter identification method that takes into account the ground capacitance and considers the line length estimation is used to identify the line parameters of the IEEE 33-node system.

[0123] 1) Construct the multivariate nonlinear voltage drop equation of distribution transformer:

[0124]

[0125] 2) Construct a local variable multivariate nonlinear voltage drop equation taking into account the ground capacitance and line length estimation:

[0126]

[0127] Resistance, reactance, and susceptance are replaced by unit length multiplied by line length, that is:

[0128]

[0129] 3) Recursive calculation of multivariate nonlinear voltage drop equation:

[0130]

[0131] Table 1 Parameter identification results of 33-node rd distribution network line

[0132]

[0133]

[0134] It can be seen that due to the small admittance to the ground, the model is given to make it have a value, which is more in line with the physical model. And the R, X multi-solution problem is converted into a single solution problem for the line length, which greatly improves the identification accuracy.

[0135] Embodiment 4:

[0136] See also Figure 5 , the verification test of the distribution network line parameter identification method taking into account the ground capacitance and considering the line length estimation includes the following contents:

[0137] The difference between the 33rd network and the 33rds network is that the 26 nodes are unloaded series nodes and therefore do not appear in the results, and the impedance of each branch is different from that of the 33rds network.

[0138] 1) Construct the multivariate nonlinear voltage drop equation of distribution transformer:

[0139]

[0140] 2) Construct a local variable multivariate nonlinear voltage drop equation taking into account the ground capacitance and line length estimation:

[0141]

[0142] Resistance, reactance, and susceptance are replaced by unit length multiplied by line length, that is:

[0143]

[0144] 3) Recursive calculation of multivariate nonlinear voltage drop equation:

[0145]

[0146] Table 2 Line parameter identification results of 33-node RDS distribution network

[0147]

[0148]

[0149] It can be seen that the 33-node RDS network, with the line impedance value changed and the series no-load node included, has an error within the allowable range.

[0150] Embodiment 5:

[0151] See also Figure 6 , the verification test of the distribution network line parameter identification method taking into account the ground capacitance and considering the line length estimation includes the following contents:

[0152] The difference between the 69rd system and the 33rd and 33rds networks is that the 69rd system has more nodes, including 24, 22, 18, 14 unloaded series nodes and 2, 3 unloaded parallel nodes, which are the most difficult to identify. Because unloaded nodes are unmeasured points, the information of these nodes needs to be inferred from other nodes.

[0153] 1) Construct the multivariate nonlinear voltage drop equation of distribution transformer:

[0154]

[0155] 2) Construct a local variable multivariate nonlinear voltage drop equation taking into account the ground capacitance and line length estimation:

[0156]

[0157] Resistance, reactance, and susceptance are replaced by unit length multiplied by line length, that is:

[0158]

[0159] 3) Recursive calculation of multivariate nonlinear voltage drop equation:

[0160]

[0161] Table 3 Parameter identification results of 69-node rd distribution network line

[0162]

[0163]

[0164] It can be seen that the 69-node rd network increases the number of nodes, changes the line impedance value, and includes series and parallel no-load nodes. The identification error of some lines increases compared with the 33-node system, but the error is still within the allowable range.

Claims

1. A method for identifying line parameters of a distribution network taking into account ground capacitance and line length estimation, characterized in that: The following steps are involved: 1) Obtain basic data of the power grid; 2) Construct the multivariate nonlinear voltage drop equation of distribution transformer; 3) Construct a multivariate nonlinear voltage drop equation that takes into account the ground capacitance and line length estimation; 4) Recursively calculate the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation to obtain the distribution network line parameters; The steps of constructing the multivariate nonlinear voltage drop equation of distribution transformer include: 2.1) Establish the relationship between the starting voltage V0 and the terminal voltage V1 and the terminal voltage V2, that is: Wherein, P1 and P2 are the active powers of the terminal nodes 1 and 2 to be determined respectively; Q1 and Q2 are the reactive powers of the terminal nodes 1 and 2 to be determined respectively; R1 and R2 are the equivalent resistances of the terminal nodes 1 and 2 to be determined respectively; X1 and X2 are the equivalent reactances of the terminal nodes 1 and 2 to be determined respectively; 2.2) According to formula (1), establish the accurate relationship between the electrical parameters of the parallel node and the terminal node 1 and the terminal node 2 to be determined, that is: In the formula, the parameters f1(R1, X1) and f2(R1, X1) are as follows: 2.3) Establish the connection criterion between any branch end node i and branch end node j at N time points, that is: In the formula, R i , R j are the equivalent resistances of branch end nodes i and j respectively; X i , X j are the equivalent reactances of branch end node i and branch end node j respectively; The steps to construct the multivariate nonlinear voltage drop equation taking into account the capacitance to ground and considering the line length estimation include: 3.1) Establish the voltage drop equation between two nodes after taking into account the capacitance to ground, that is: In the formula, V0 is the starting voltage, V1 and V2 are the terminal voltages to be determined; Y1 and Y2 are the admittances; 3.2) Taking voltage V1, voltage V2, active power P1, active power P2, reactive power Q1, reactive power Q2 as known quantities, and resistance R1, reactance X1, resistance R2, reactance X2, susceptance B1, susceptance B2 as estimated quantities to be determined, substitute the known quantities into formula (1) to obtain: 3.3) Establish the connection criterion between any branch end node i and branch end node j at N time points, namely: In the formula, f i (R i ,X i ,Y i ,V i ), f j (R j ,X j ,Y j ,V j ) is the connection criterion parameter; 3.4) Substituting resistance, reactance, and susceptance by unit length multiplied by line length, we get: In the formula, They represent the unit equivalent resistance of branch end node i and branch end node j respectively; They represent the unit equivalent reactance of branch end node i and branch end node j respectively; They represent the unit equivalent susceptance of branch end node i and branch end node j respectively; B i , B j They represent the equivalent susceptance of branch end node i and branch end node j respectively; L i , L j Indicates the line length; R i , R j are the equivalent resistances of branch end nodes i and j respectively; X i , X j are the equivalent reactances of branch end node i and branch end node j respectively; 3.5) Substituting formula (11) into formula (10), we get the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation, namely:

2. The method for identifying distribution network line parameters taking into account ground capacitance and line length estimation according to claim 1, characterized in that: The basic data of the power grid include the topological structure of the power grid, the number of observable nodes N obs , the active power measurement of the node P i , reactive power measurement Q of the node i , the voltage amplitude measurement of the node V i .

3. The method for identifying line parameters of a distribution network taking into account ground capacitance and line length estimation according to claim 1, characterized in that: The distribution network line parameters include the feeder end branch Z end The state variable U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end , Feeder middle branch Z mid The state variable U mid ,U mid+1 ,P mid+1 ,Q mid+1 ; Feeder end branch Y end Active power and reactive power at the head end; P end ,Q end Feeder end branch Y end Active power and reactive power at the end.

4. The method for identifying line parameters of a distribution network taking into account ground capacitance and line length estimation according to claim 1, characterized in that: The steps of recursively calculating the multivariate nonlinear voltage drop equation taking into account the capacitance to ground and considering the line length estimation include: 1) Measure the feeder end branch Z end Power quantity measurement U mid+1 ,P mid+1 ,Q mid+1 ,U end ,P end ,Q end , and the feeder end branch Z is calculated based on the multivariate nonlinear voltage drop equation taking into account the ground capacitance and the line length estimation. end The resistance R end Reactance X end and electrosusceptor B end Among them, U mid+1 , U end is voltage; P mid+1 , P end is the active power; Q mid+1 , Q end is the reactive power; 2) Calculate the feeder end branch Z end Active power at the head end and reactive power Right now: 3) Active power and reactive power Replace active power P mid+1 and reactive power Q mid+1 , from the feeder end branch Z end At the beginning, parameter estimation and recursive calculation of loop variables are performed from bottom to top to obtain the topology and branch parameter information of the entire network.

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