A method for evaluating power quality line loss in a substation based on incomplete measurement data

Abstract

The present invention belongs to the technical field of line loss assessment, and relates to a method for assessing line loss of power quality in a substation with incomplete measurement data. The method includes: decoupling unbalanced power; determining reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor, and determining the expression of the fundamental positive sequence active line loss power factor of each branch; determining the substation topology matrix corresponding to the substation that needs to perform unbalanced line loss assessment; calculating the current vectors of all branches according to the substation topology matrix; based on the measurement and decomposition of the current vectors of the branches in the substation, solving the fundamental positive sequence active line loss power factor of each branch in the substation and calculating the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor. Based on electrical network analysis and Kirchhoff's current law, the present invention uses the measurement data of some branches to realize the calculation and evaluation of the power quality line loss power factor of all branches in the substation.

Description

Technical Field

[0001] The present invention belongs to the technical field of line loss assessment, and in particular, relates to a method for assessing power quality line loss in a substation using incomplete measurement data. Background Art

[0002] Existing research on distribution network line loss mainly focuses on the theoretical line loss calculation under the influence of a single power quality problem, but it has certain limitations under actual working conditions. There are few studies on statistical line loss considering power quality issues, and existing studies are mainly based on qualitative analysis, and few consider quantitative calculation and evaluation of statistical line loss of composite power quality. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a method for evaluating power quality line loss in a substation using incomplete measurement data, comprising:

[0004] To decouple the unbalanced power, the total line loss is divided into fundamental positive sequence active line loss, fundamental positive sequence reactive additional line loss, unbalanced additional line loss and harmonic additional line loss;

[0005] Determine the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor, and determine the expression of the fundamental positive sequence active line loss power factor of each branch based on the fundamental positive sequence active power, fundamental positive sequence reactive power, fundamental unbalanced power and harmonic current distortion power;

[0006] Determine the substation topology matrix corresponding to the substation that needs to perform unbalanced line loss assessment;

[0007] Calculate the current vectors of all branches according to the substation topology matrix;

[0008] Based on the measurement and decomposition of the current vector of the branch in the substation, the expression of the fundamental positive sequence active line loss power factor is transformed, the fundamental positive sequence active line loss power factor of each branch in the substation is solved, and the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor are calculated.

[0009] Based on the above technical solution, the present invention can also be improved as follows.

[0010] Furthermore, the unbalanced power is decoupled and the total line loss is divided into fundamental positive sequence active line loss, fundamental positive sequence reactive additional line loss, unbalanced additional line loss and harmonic additional line loss, including:

[0011] Let ΔP eLoss Indicates the total line loss, ΔP ePmin Indicates the fundamental positive sequence active line loss, ΔP eQ Indicates the additional line loss of fundamental positive sequence reactive power, ΔP eUIndicates the unbalanced additional line loss, ΔP eH represents the additional line loss of harmonics, then:

[0012] ΔP eLoss =ΔP eP-min +ΔP eQ +ΔP eU +ΔP eH .

[0013] Furthermore, the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor are determined, and the expression of the fundamental positive sequence active line loss power factor of each branch is determined according to the fundamental positive sequence active power, fundamental positive sequence reactive power, fundamental unbalanced power and harmonic current distortion power, including:

[0014] Assume that the fundamental positive sequence active line loss power factor of each branch is PF eP , P1 + Indicates the fundamental positive sequence active power, Q1 + Indicates the fundamental positive sequence reactive power, S U1 Indicates the fundamental wave unbalanced power, D eI Represents the harmonic current distortion power, then:

[0015]

[0016] Assume the reactive line loss power factor is PF eQ , the unbalanced line loss power factor is PF eU , the harmonic line loss power factor is PF eH ,but:

[0017]

[0018] In practical applications, the branch current is simplified to obtain:

[0019]

[0020] Furthermore, the substation topology matrix corresponding to the substation that needs to be evaluated for unbalanced line loss is determined, including:

[0021] Sort out the directed graph of the substation topology to complete node identification, line identification and current direction identification;

[0022] Draw the area topology directed connectivity graph based on the area topology directed graph;

[0023] Identify the tree branches and connected branches of the directed connected graph of the substation topology. The branches except the tree branches in the directed connected graph of the substation topology constitute connected branches. The connected branches are close to the user side where the electric meter is placed.

[0024] Determine the association matrix according to the relationship between nodes and branches in the directed connected graph of the substation topology, and determine the basic loop matrix according to the relationship between basic loops and branches in the directed connected graph of the substation topology;

[0025] The substation topology matrix is ​​obtained based on the association matrix and the basic loop matrix.

[0026] Furthermore, the tree branch of the area topology directed connected graph includes all vertices, and the tree branch does not have any loop; among any two vertices of the tree branch, there is only one path connecting the two vertices.

[0027] Further, the current vectors of all branches are calculated according to the substation topology matrix, including: assuming that the association matrix is ​​A and the basic loop matrix is ​​B; if the directed connected graph has n vertices and m branches, then the association matrix A is a (n-1)×m matrix, the nodes of the directed connected graph correspond to the rows of the association matrix, and the branches correspond to the columns of the association matrix; the basic loop matrix B represents the relationship between the basic loop and the branch in the directed connected graph; if the directed connected graph has n vertices and m branches, then the basic loop matrix B is a (m-n+1)×m matrix;

[0028] Let i be the number of loops, j be the number of branches, A = [a ij ],B=[b ij ],but:

[0029]

[0030] Arrange the columns of the incident matrix A and the basic circuit matrix B of the directed connected graph in the same branch order, then:

[0031] AB T =0; BA T =0;

[0032] Arrange the columns of the association matrix A and the basic loop matrix B in the order of tree branches first and then link branches. Let A t is the branch association matrix, A1 is the link branch association matrix, then:

[0033]

[0034] A t If it is not singular, then:

[0035]

[0036] The reference direction of each branch in the directed connected graph is marked, and a node in the directed connected graph is selected as the reference node. Let I represent the branch current vector. According to Kirchhoff's current law, we can get:

[0037] AI = 0;

[0038] Assume i t is the tree branch current vector matrix, i1 is the connecting branch current vector matrix, and the tree branches are numbered in the order of first tree branch and then connecting branch, then:

[0039]

[0040] The current vector of the branch is:

[0041]

[0042] Furthermore, based on the measurement and decomposition of the current vector of the branch in the substation, the expression of the fundamental positive sequence active line loss power factor is transformed to solve the fundamental positive sequence active line loss power factor of each branch in the substation, including:

[0043] Assume that the fundamental positive sequence active power factor is PF eP , is the fundamental positive sequence voltage, is the fundamental positive sequence active current, is the fundamental positive sequence current, is the fundamental negative sequence current, is the zero sequence current, I U1 is the fundamental unbalanced current, I U1 The value of is the harmonic current, then the expression of the fundamental positive sequence active line loss power factor of each branch is converted into:

[0044]

[0045] Further, I AH ,I BH and I CH is the three-phase harmonic current, I NH is the neutral line harmonic current, I eH is the harmonic current The corresponding equivalent harmonic current is:

[0046]

[0047] Let I A0 is the A-phase DC component, I Ah is the harmonic component of phase A, I B0 is the B-phase DC component, I Bh is the B-phase harmonic component, I C0 is the C phase DC component, I Ch is the C-phase harmonic component, then:

[0048]

[0049] The beneficial effect of the present invention is that the present invention is based on electrical network analysis and Kirchhoff's current law, and utilizes the measurement data of some branches to realize the calculation and evaluation of the power quality line loss power factor of all branches in the substation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 A schematic diagram of a method for evaluating power quality line loss in a substation using incomplete measurement data provided in Example 1 of the present invention;

[0051] Figure 2 It is the actual topological map of the area;

[0052] Figure 3 for Figure 2 The corresponding area topology directed connected graph;

[0053] Figure 4 It is a diagram of topological nodes, branches and user identification in the substation area. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0055] As an example, Figure 1 As shown, in order to solve the above technical problems, this embodiment provides a method for evaluating power quality line loss in a substation using incomplete measurement data, including:

[0056] To decouple the unbalanced power, the total line loss is divided into fundamental positive sequence active line loss, fundamental positive sequence reactive additional line loss, unbalanced additional line loss and harmonic additional line loss;

[0057] Determine the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor, and determine the expression of the fundamental positive sequence active line loss power factor of each branch according to the fundamental positive sequence active power, fundamental positive sequence reactive power, fundamental unbalanced power and harmonic current distortion power; the reactive line loss power factor is used to evaluate the contribution of the fundamental positive sequence reactive power to the reactive additional line loss; the unbalanced line loss power factor is used to evaluate the contribution of the unbalanced apparent power to the unbalanced additional line loss; the harmonic line loss power factor is used to evaluate the impact of the current distortion power on the harmonic additional line loss;

[0058] Determine the substation topology matrix corresponding to the substation that needs to perform unbalanced line loss assessment;

[0059] Calculate the current vectors of all branches according to the substation topology matrix;

[0060] Based on the measurement and decomposition of the current vector of the branch in the substation, the expression of the fundamental positive sequence active line loss power factor is transformed, the fundamental positive sequence active line loss power factor of each branch in the substation is solved, and the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor are calculated.

[0061] The present invention proposes power quality line loss power decoupling and fundamental positive sequence active line loss power factor, sorts out the substation topology, obtains all branch currents in the substation by connecting branches, and solves the line loss power factor of the substation branch by the branch current.

[0062] Optionally, the unbalanced power is decoupled and the total line loss is divided into fundamental positive sequence active line loss, fundamental positive sequence reactive additional line loss, unbalanced additional line loss and harmonic additional line loss, including:

[0063] Let ΔP eLoss Indicates the total line loss, ΔP ePmin Indicates the fundamental positive sequence active line loss, ΔP eQ Indicates the additional line loss of fundamental positive sequence reactive power, ΔP eU Indicates the unbalanced additional line loss, ΔP eH represents the additional line loss of harmonics, then:

[0064] ΔP eLoss =ΔP eP-min +ΔP eQ +ΔP eU +ΔP eH .

[0065] Optionally, the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor are determined, and the expression of the fundamental positive sequence active line loss power factor of each branch is determined according to the fundamental positive sequence active power, the fundamental positive sequence reactive power, the fundamental unbalanced power and the harmonic current distortion power, including:

[0066] Assume that the fundamental positive sequence active line loss power factor of each branch is PF eP , P1 + Indicates the fundamental positive sequence active power, Indicates the fundamental positive sequence reactive power, S U1 Indicates the fundamental wave unbalanced power, D eI Represents the harmonic current distortion power, then:

[0067]

[0068] Assume the reactive line loss power factor is PF eQ , the unbalanced line loss power factor is PFeU , the harmonic line loss power factor is PF eH ,but:

[0069]

[0070] In practical applications, the branch current is simplified to obtain:

[0071]

[0072] Optionally, determining a substation topology matrix corresponding to a substation that needs to perform unbalanced line loss assessment includes:

[0073] Sort out the directed graph of the substation topology to complete node identification, line identification and current direction identification;

[0074] Draw the area topology directed connectivity graph based on the area topology directed graph;

[0075] Identify the tree branches and connected branches of the directed connected graph of the substation topology. The branches except the tree branches in the directed connected graph of the substation topology constitute connected branches. The connected branches are close to the user side where the electric meter is placed.

[0076] Determine the association matrix according to the relationship between nodes and branches in the directed connected graph of the substation topology, and determine the basic loop matrix according to the relationship between basic loops and branches in the directed connected graph of the substation topology;

[0077] The substation topology matrix is ​​obtained based on the association matrix and the basic loop matrix.

[0078] Optionally, a tree branch of the directed connected graph of the station area topology includes all vertices, and the tree branch does not have any loop; among any two vertices of the tree branch, there is one and only one path connecting the two vertices.

[0079] Optionally, the current vectors of all branches are calculated according to the substation topology matrix, including: assuming that the association matrix is ​​A and the basic loop matrix is ​​B; if the directed connected graph has n vertices and m branches, then the association matrix A is a (n-1)×m matrix, the nodes of the directed connected graph correspond to the rows of the association matrix, and the branches correspond to the columns of the association matrix; the basic loop matrix B represents the relationship between the basic loops and the branches in the directed connected graph; if the directed connected graph has n vertices and m branches, then the basic loop matrix B is a (m-n+1)×m matrix;

[0080] Let i be the number of loops, j be the number of branches, A = [a ij ],B=[b ij ],but:

[0081]

[0082] Arrange the columns of the incident matrix A and the basic circuit matrix B of the directed connected graph in the same branch order, then:

[0083] AB T =0; BA T =0;

[0084] Arrange the columns of the association matrix A and the basic loop matrix B in the order of tree branches first and then link branches. Let A t is the branch association matrix, A1 is the link branch association matrix, then:

[0085]

[0086] A t If it is not singular, then:

[0087]

[0088] The reference direction of each branch in the directed connected graph is marked, and a node in the directed connected graph is selected as the reference node. Let I represent the branch current vector. According to Kirchhoff's current law, we can get:

[0089] AI = 0;

[0090] Assume i t is the tree branch current vector matrix, i1 is the connecting branch current vector matrix, and the tree branches are numbered in the order of first tree branch and then connecting branch, then:

[0091]

[0092] The current vector of the branch is:

[0093]

[0094] Therefore, the current vectors of all branches are calculated through the association matrix A or the basic loop B of the substation topology and the branch current vector.

[0095] Optionally, based on the measurement and decomposition of the current vector of the branch in the substation area, the expression of the fundamental positive sequence active line loss power factor is transformed to solve the fundamental positive sequence active line loss power factor of each branch in the substation area, including:

[0096] Assume that the fundamental positive sequence active power factor is PF eP , is the fundamental positive sequence voltage, is the fundamental positive sequence active current, is the fundamental positive sequence current, is the fundamental negative sequence current, is the zero sequence current, I U1 is the fundamental unbalanced current, I U1 The value of is the harmonic current, then the expression of the fundamental positive sequence active line loss power factor of each branch is converted into:

[0097]

[0098] Optional, I AH ,I BH and I CH is the three-phase harmonic current, I NH is the neutral line harmonic current, I eH is the harmonic current The corresponding equivalent harmonic current is:

[0099]

[0100] Let I A0 is the A-phase DC component, I Ah is the harmonic component of phase A, I B0 is the B-phase DC component, I Bh is the B-phase harmonic component, I C0 is the C phase DC component, I Ch is the C-phase harmonic component, then:

[0101]

[0102] Fundamental positive sequence active power factor PF eP , reactive line loss power factor PF eQ , unbalanced line loss power factor PF eU And harmonic line loss power factor PF eH The value range is between 0 and 1. The smaller the value, the more obvious the abnormal line loss is. eQ , unbalanced line loss power factor PF eU And harmonic line loss power factor PF eH The values ​​of reflect the degree of reactive line loss, unbalanced line loss and harmonic line loss respectively, and can provide direction for the treatment of corresponding power quality issues.

[0103] Through verification on the actual area simulation model, the actual area topology diagram is as shown in the attached figure. Figure 2 As shown, 1-6 are user numbers, b1-b11 are branches, Figure 3 is a directed connected graph of the substation topology. In the simulation of this substation, the rated frequency of the system's three-phase AC power supply is set to 50Hz, the effective value of the voltage is 220V, and the impedance of each branch and the neutral point impedance are set to 0.2Ω. The topological nodes, branches and user identification diagrams of this substation are shown in the attached figure. Figure 4 Table 1 shows the line loss power factor of the tree branch in the substation area.

[0104] Table 1. Power factor of line loss in tree branches in the substation area.

[0105]

[0106] In terms of user settings, user 1 is a pure resistive load that is balanced and does not contain harmonics; user 2 is a resistive-inductive load that is balanced and does not contain harmonics; user 3 is an unbalanced pure resistive load that does not contain harmonics; user 4 is a balanced harmonic load that does not contain reactive power; users 5 and 6 have complex power quality issues.

[0107] The specific load settings of the simulation model of this substation are shown in Table 2, and the power quality decoupling current data of the branch line of the simulation model are shown in Table 1.

[0108] Table 2 Specific load setting table of the simulation model of the substation

[0109]

[0110]

[0111] Table 3 gives the calculation results of the decoupling component of the branch current and the line loss power factor. Table 4 calculates the actual and calculated values ​​of the decoupling component of the tree branch current and the line loss power factor, and gives the errors. It can be seen from Table 4 that compared with the actual values, the errors of the four line loss power factors of the tree branch calculated by the method of the present invention are all less than 0.6%. From the above analysis, it can be seen that when the collection data and collection equipment are limited, it is feasible to use electrical network analysis and Kirchhoff's current law to substitute the current data of the branch current in the substation to calculate the power quality line loss power factor of each branch in the substation.

[0112] Table 3 Calculation results of branch current decoupling component and line loss power factor

[0113]

[0114] Table 4 Current data, line loss power factor and comparison table of tree branches

[0115]

[0116] By comparing the critical values ​​of unbalanced power factor and harmonic power factor, it can be seen that the branches with abnormal unbalanced line loss in this area are b1-b11, and the branches with abnormal harmonic line loss are b2-b11. Although user 1 is set as a perfect load with no power quality problems, the unbalanced line loss power factor of branch 1 is still below the limit, which means that the unbalanced problems of users 3, 5 and 6 can cause the unbalance of user 1 to exceed the limit through branches b2, b4, b6 and b8. Therefore, the perfect load may also have unbalanced problems due to other users in the area. In addition, the unbalanced and harmonic power factors increase with the increase of the distance from the source of the power quality problem, which is in line with the law that harmonic and unbalanced problems weaken with the line.

[0117] In addition, the active line loss power factors of branches b3, b5, b6, b8, b9 and b10 are all lower than 0.9, among which b10 is the lowest, only 0.562. b3, b5, b6 and b10 are connected branches. By comparing the load settings of the substation area, it can be seen that the active line loss power factors of these branches are greatly affected by the load. User 6 has the smallest power factor and has serious unbalance and harmonic problems, resulting in the lowest active line loss power factor of branch b10.

[0118] The present invention is based on electrical network analysis and Kirchhoff's current law, and utilizes measurement data of some branches to calculate and evaluate the power factor of the power quality line loss of all branches in the substation.

[0119] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for evaluating power quality line loss in a substation using incomplete measurement data, characterized in that: include: To decouple the unbalanced power, the total line loss is divided into fundamental positive sequence active line loss, fundamental positive sequence reactive additional line loss, unbalanced additional line loss and harmonic additional line loss; Determine the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor, and determine the expression of the fundamental positive sequence active line loss power factor of each branch based on the fundamental positive sequence active power, fundamental positive sequence reactive power, fundamental unbalanced power and harmonic current distortion power; Determine the substation topology matrix corresponding to the substation that needs to perform unbalanced line loss assessment; Calculate the current vectors of all branches according to the substation topology matrix; Based on the measurement and decomposition of the current vector of the branch in the substation, the expression of the fundamental positive sequence active line loss power factor is transformed, the fundamental positive sequence active line loss power factor of each branch in the substation is solved, and the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor are calculated.

2. According to the method for evaluating power quality line loss in a substation based on incomplete measurement data of claim 1, it is characterized in that: To decouple the unbalanced power, the total line loss is divided into fundamental positive sequence active line loss, fundamental positive sequence reactive additional line loss, unbalanced additional line loss and harmonic additional line loss, including: set up ΔP eLoss Indicates the line bus loss, ΔP ePmin Indicates the fundamental positive sequence active line loss, ΔP eQ Indicates the fundamental positive sequence reactive additional line loss, ΔP eU represents the unbalanced additional line loss, ΔP eH represents the additional line loss of harmonics, then: ΔP eLoss =ΔP eP-min +ΔP eQ +ΔP eU +ΔP eH 。 3. According to the method for evaluating power quality line loss in a substation area based on incomplete measurement data of claim 1, it is characterized in that: Determine the reactive line loss power factor, unbalanced line loss power factor and harmonic line loss power factor, and determine the expression of the fundamental positive sequence active line loss power factor of each branch according to the fundamental positive sequence active power, fundamental positive sequence reactive power, fundamental unbalanced power and harmonic current distortion power, including: Assume that the fundamental positive sequence active line loss power factor of each branch is PFeP , P 1 + Indicates the fundamental positive sequence active power, Q 1 + Indicates the fundamental positive sequence reactive power, S U1 Indicates the fundamental wave unbalanced power, D eI Represents the harmonic current distortion power, then: Assume the reactive line loss power factor is PF eQ , the unbalanced line loss power factor is PF eU , the harmonic line loss power factor is PF eH ,but: In practical applications, the branch current is simplified to obtain:

4. According to the method for evaluating power quality line loss in a substation based on incomplete measurement data of claim 1, it is characterized in that: Determine the area topology matrix corresponding to the area where unbalanced line loss assessment is required, including: Sort out the directed graph of the substation topology to complete node identification, line identification and current direction identification; Draw the area topology directed connectivity graph based on the area topology directed graph; Identify the tree branches and connected branches of the directed connected graph of the substation topology. The branches except the tree branches in the directed connected graph of the substation topology constitute connected branches. The connected branches are close to the user side where the electric meter is placed. Determine the association matrix according to the relationship between nodes and branches in the directed connected graph of the substation topology, and determine the basic loop matrix according to the relationship between basic loops and branches in the directed connected graph of the substation topology; The substation topology matrix is ​​obtained based on the association matrix and the basic loop matrix.

5. According to the method for evaluating power quality line loss in a substation area based on incomplete measurement data of claim 4, it is characterized in that: The tree branch of the area topology directed connected graph contains all vertices, and the tree branch does not have any loop; among any two vertices in the tree branch, there is only one path connecting the two vertices.

6. According to the method for evaluating power quality line loss in a substation area based on incomplete measurement data as described in claim 1, it is characterized in that: According to the area topology matrix, the current vectors of all branches are calculated, including: Assume that the correlation matrix is A , the basic loop matrix is B ; If a directed connected graph has n vertices and m branches, then the incidence matrix A is a (n-1)×m matrix. The nodes of the directed connected graph correspond to the rows of the incidence matrix, and the branches correspond to the columns of the incidence matrix. The basic circuit matrix B Characterizes the relationship between basic loops and branches in a directed connected graph; if a directed connected graph has n vertices and m branches, then the basic loop matrix B is a (m-n+1)×m matrix; Let i be the number of loops and j be the number of branches. A＝[a ij ], B＝[b ij ],but: Incidence matrix of a directed connected graph arranged in the same branch order A With the basic loop matrix B Columns, then: AB T =0; BAT =0; The incidence matrix A With the basic loop matrix B The order of the columns is first tree branch and then link branch. A t is the branch association matrix, A1 is the link branch association matrix, then: A t If it is not singular, then: Determine the reference direction of each branch in the directed connected graph, and select a node in the directed connected graph as the reference node. I represents the branch current vector, according to Kirchhoff's current law: AI = 0; set up i t is the tree branch current vector matrix, i1 is the connecting branch current vector matrix, and the tree branches are numbered in the order of first tree branch and then connecting branch, then: The current vector of the branch is:

7. According to the method for evaluating power quality line loss in a substation area based on incomplete measurement data as described in claim 1, it is characterized in that: Based on the measurement and decomposition of the current vector of the branch in the substation area, the expression of the fundamental positive sequence active line loss power factor is transformed to solve the fundamental positive sequence active line loss power factor of each branch in the substation area, including: Assume that the fundamental positive sequence active power factor is PF eP , is the fundamental positive sequence voltage, is the fundamental positive sequence active current, is the fundamental positive sequence current, is the fundamental negative sequence current, is the zero sequence current, I U1 is the fundamental unbalanced current, I U1 The value of is the harmonic current, then the expression of the fundamental positive sequence active line loss power factor of each branch is converted into:

8. The method for evaluating power quality line loss in a substation based on incomplete measurement data according to claim 7, characterized in that: I AH , I BH and I CH is the three-phase harmonic current, I NH is the neutral line harmonic current, I eH is the harmonic current The corresponding equivalent harmonic current is: set up I A0 is the A-phase DC component, I Ah is the harmonic component of phase A, I B0 is the B-phase DC component, I Bh is the B-phase harmonic component, I C0 is the C phase DC component, I Ch is the C-phase harmonic component, then:

Images