An optimization evaluation method for 10kV distribution network line

Abstract

The application provides an optimization evaluation method for a 10kV power distribution network line, comprising: obtaining operation information of the 10kV power distribution network line; performing operation on the operation information of the 10kV power distribution network line through a preset feeder optimization model to obtain corresponding evaluation indexes; wherein the evaluation indexes at least include a maximum load rate, a minimum load rate, a highest voltage value and a lowest voltage value; judging whether there is a problem to be optimized according to the corresponding evaluation indexes, if there is, it is determined that optimization is needed, and if there is not, it is determined that optimization is not needed. The application aims at the built power supply area, takes the feeder group in the power grid as a basic unit, analyzes the typical operation scene after the load point expansion, identifies the 10kV line operation safety hidden danger, eliminates the line operation safety hidden danger, realizes the load balance among lines, and thus guarantees the economy and safety of the power distribution network reconstruction scheme.

Description

Technical Field

[0001] This invention relates to the field of optimization evaluation technology for 10kV distribution network lines, and in particular to an optimization evaluation method for 10kV distribution network lines. Background Technology

[0002] The adoption of a power grid-based approach for distribution network planning and design has become a development trend. According to this approach, a power supply area can be divided into several power grids, each independent of the others and designed separately. Each power grid consists of several feeder groups, each containing 2-4 10kV lines, using typical wiring configurations such as single-ring networks, double-ring networks, and N-power-one-standby. The 10kV lines within each feeder group can be interconnected via tie switches, depending on the load's power supply reliability requirements.

[0003] Due to the wide coverage and large number of 10kV lines and load points, as new power loads are continuously connected to the distribution network, the original distribution network may not be able to meet the requirements of load growth, and may face operational safety hazards such as "unreasonable load distribution, line overload, and voltage non-compliance". Therefore, it is necessary to carry out phased transformation of the distribution network. Summary of the Invention

[0004] The purpose of this invention is to propose an optimized evaluation method for 10kV distribution network lines, and to solve the technical problems of operational safety hazards such as unreasonable load distribution, line overload, and unqualified voltage.

[0005] On the one hand, an optimization evaluation method for 10kV distribution network lines is provided, including:

[0006] Obtain operational information for 10kV distribution network lines;

[0007] The operation information of the 10kV distribution network line is calculated by a preset feeder optimization model to obtain various corresponding evaluation indicators; wherein, the evaluation indicators include at least the maximum load rate, minimum load rate, highest voltage value and lowest voltage value.

[0008] Based on the evaluation indicators corresponding to each item, it is determined whether there are any issues that need to be optimized. If so, optimization is required; otherwise, optimization is not required.

[0009] Preferably, the operating information of the 10kV distribution network line includes at least:

[0010] Location of substations, main transformer models and capacities within the power supply grid;

[0011] The topology, line segment type, cross-sectional information, length information, load point location, load point capacity, and representative daily load curves for all 10kV lines within the power supply grid in spring, summer, autumn, and winter;

[0012] Location information, capacity information, and typical load curves for load point expansion.

[0013] Preferably, the feeder optimization model specifically includes:

[0014] min f=f1+f2=(C INV +C ploss )+αBalan

[0015]

[0016]

[0017] Where f represents the objective function of the feeder optimization model, f1 represents the annual additional cost, f2 represents the load balancing within the grid, and C INV C represents the annual investment cost for newly constructed lines. ploss This represents the annual line loss cost, Balan represents the variance of the load rate of all lines within the grid used for load balancing, and α represents the weight. Lsi C represents the annual cost conversion factor for the line. UL L represents the investment cost per unit length of the line. i Let r represent the length of the i-th newly built line, r0 represent the annual interest rate of the power industry, zm represent the number of newly built lines, and n represent the service life of the line.

[0018] Preferably, the feeder optimization model further includes:

[0019]

[0020] Among them, C ploss D represents the annual cost of line loss. i This represents the number of days in the i-th season. This represents the power loss in the k-th hour of the i-th season. Let $\frac{ ...

[0021] Preferably, the feeder optimization model further includes:

[0022]

[0023]

[0024] Where BFZ(i,j,t) represents the load rate of the j-th neighboring line of the i-th line at time t, BJFZ(i,t) represents the average load rate of all neighboring lines of the i-th line at time t, k represents the maximum number of neighboring lines, 96 corresponds to the total number of time periods of the day representing the four seasons, m represents the total number of lines, and Balan represents the mean of the variance of the load rates of m lines and their neighboring lines.

[0025] Preferably, the calculation of the operation information of the 10kV distribution network line using a preset feeder optimization model specifically includes:

[0026] The operation information of the 10kV distribution network line is initialized, useless parameter information is filtered out, and the iteration number is set to 0;

[0027] The power parameters of each node are calculated using a feeder optimization model. These power parameters include at least the load value of each node, the corresponding power loss value, the node power consumption value, and the voltage at the end of the branch.

[0028] Determine whether the power parameters of each node meet the preset judgment conditions or whether the number of iterations is greater than the preset iteration threshold. If the preset judgment conditions are not met or the number of iterations is not greater than the preset iteration threshold, recalculate the power parameters of each node and increment the number of iterations by one. If the preset judgment conditions are met or the number of iterations is greater than the preset iteration threshold, output the power of the balancing node as the calculation result.

[0029] Preferably, the evaluation indicators for each item are calculated according to the following formula:

[0030] FZmax(i)=max{p(i,1),p(i,2),…,p(i,k)} / Syx(i)

[0031] FZmin(i)=min{p(i,1),p(i,2),…,p(i,k)} / Syx(i)

[0032] DYmax(i)=max{V(i,1),V(i,2),…,V(i,k)}

[0033] DYmax(i)=min{V(i,1),V(i,2),…,V(i,k)}

[0034] Where FZmax(i) represents the maximum load rate, FZmin(i) represents the minimum load rate, DYmax(i) represents the highest voltage value, DYmax(i) represents the lowest voltage value, p(i,k) represents the first segment power of the i-th line at time k, V(i,k) represents the end voltage of the i-th line at time k, and Syx(i) represents the transmission capacity of the i-th line.

[0035] Preferably, the step of evaluating and determining whether there are problems to be optimized based on the corresponding evaluation indicators specifically includes:

[0036] When the maximum load rate is greater than 80% and less than or equal to 100%, the corresponding line is determined to be overloaded.

[0037] When the minimum load rate is less than 20%, the corresponding line is considered lightly loaded.

[0038] If a line is heavily loaded, it is determined that there is a potential safety hazard in the operation of the 10kV distribution network line.

[0039] If a line is lightly loaded, it is determined that the 10kV distribution network line has been over-invested.

[0040] If both heavy loads and light loads exist within the same power supply grid, it is determined that the load distribution of each line within the 10kV distribution network grid is unreasonable and needs to be re-optimized.

[0041] Preferably, the step of evaluating and determining whether there are problems to be optimized based on the corresponding evaluation indicators further includes:

[0042] Determine whether the corresponding evaluation indicator meets the preset major branch conditions. If it does, determine the corresponding branch type.

[0043] The large branch conditions include,

[0044] When the branch control load reaches the preset load threshold and the upper limit of the number of users reaches the first user threshold, it is determined to be an industrial load branch.

[0045] When the branch control load reaches the preset load threshold and the upper limit of the number of users reaches the second user threshold, it is determined to be a commercial load branch.

[0046] Preferably, the step of evaluating and determining whether there are problems to be optimized based on the corresponding evaluation indicators further includes:

[0047] Calculate the load factor variance of the line using the following formula:

[0048]

[0049]

[0050] Where Fbal represents the load rate variance of k lines, FZ(i,t) represents the load rate of the i-th line at time t, JFZ(t) represents the average load rate of all lines at time t, and 96 corresponds to the total number of time periods per day representing the four seasons.

[0051] When the load factor variance of a line exceeds a preset variance threshold, it is determined that there is an unreasonable load distribution in the line.

[0052] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0053] The optimization evaluation method for 10kV distribution network lines provided by this invention takes feeder groups within the power grid as the basic unit for existing power supply areas. It analyzes typical operating scenarios after load point expansion, identifies potential safety hazards in 10kV line operation, and proposes a comprehensive optimization method for 10kV line renovation schemes that simultaneously considers load transfer on the main line and the relocation of large branches. This method eliminates hidden safety risks in line operation, achieves load balancing between lines, and thus ensures the economy and safety of the distribution network renovation scheme. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0055] Figure 1 This is a schematic diagram of the main process of an optimization evaluation method for 10kV distribution network lines in an embodiment of the present invention.

[0056] Figure 2 This is a flowchart illustrating the forward-backward substitution algorithm in an embodiment of the present invention.

[0057] Figure 3 This is a schematic diagram of the load shifting of large branches and the load transfer of the main line in an embodiment of the present invention. Detailed Implementation

[0058] 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 accompanying drawings.

[0059] like Figure 1 The diagram shown is a schematic representation of an embodiment of an optimization evaluation method for 10kV distribution network lines provided by the present invention. In this embodiment, the method includes the following steps:

[0060] Obtain the operational information of 10kV distribution network lines; that is, determine the boundary conditions of the lines based on the operational information.

[0061] In this embodiment, the operational information of the 10kV distribution network lines includes at least: the location, main transformer model, and capacity of substations within the power supply grid; the topology, line segment model, cross-sectional information, length information, load point location, load point capacity, and representative daily load curves for all 10kV lines within the power supply grid in spring, summer, autumn, and winter; and the location, capacity, and typical load curves for load point expansion. Four representative days from each of the four seasons (spring, summer, autumn, and winter) are selected as typical operational scenarios, using 24-hour data. For the 24-hour cross-sections of typical days, a forward-backward load flow algorithm can be used to obtain the power distribution and node voltage distribution of each 10kV line. Statistical analysis is performed based on the line power and node voltage of 24*4=96 time cross-sections to identify operational safety issues of the 10kV lines.

[0062] The operation information of the 10kV distribution network line is calculated by a preset feeder optimization model to obtain various corresponding evaluation indicators. Among them, the evaluation indicators include at least the maximum load rate, minimum load rate, highest voltage value and lowest voltage value. That is, the 10kV distribution network is a closed-loop structure, operates in an open-loop manner, has a high line R / X value, and a large number of node branches. The forward-backward substitution method is more suitable for the power flow algorithm of the distribution network.

[0063] In this embodiment, the objective function f of the optimized mathematical model considers the annual increase in cost f1 caused by the implementation of the renovation measures and the load balancing within the grid f2. The annual increase in cost f1 is the equivalent annual value C of the investment in the new line. INV Annual network loss cost C ploss Load balancing within the grid is represented by the variance of the load rates of all lines within the grid, expressed as Balan. Considering the different dimensions of f1 and f2, the objective function f is a weighted sum of f1 and f2, with α as the weight. The implementers of the line upgrade can determine the weight α based on their emphasis on construction costs and the degree of importance and requirement for load balancing. If the current distribution network load distribution is severely unreasonable, or if both heavy overload and light overload problems are prominent, the value of α should be increased. The feeder optimization model specifically includes:

[0064] min f=f1+f2=(C INV +C ploss )+αBalan

[0065]

[0066]

[0067] Where f represents the objective function of the feeder optimization model, f1 represents the annual additional cost, f2 represents the load balancing within the grid, and C INV C represents the annual investment cost for newly constructed lines. plossThis represents the annual line loss cost, Balan represents the variance of the load rate of all lines within the grid used for load balancing, and α represents the weight. Lsi C represents the annual cost conversion factor for the line. UL L represents the investment cost per unit length of the line. i Let r represent the length of the i-th newly built line, r0 represent the annual interest rate of the power industry, zm represent the number of newly built lines, and n represent the service life of the line.

[0068] Also includes:

[0069]

[0070] Among them, C ploss D represents the annual cost of line loss. i This represents the number of days in the i-th season. This represents the power loss in the k-th hour of the i-th season. Let $\frac{ ...

[0071] Also includes:

[0072]

[0073]

[0074] Where BFZ(i,j,t) represents the load rate of the j-th neighboring line of the i-th line at time t, BJFZ(i,t) represents the average load rate of all neighboring lines of the i-th line at time t, k represents the maximum number of neighboring lines, 96 corresponds to the total number of time periods of the day representing the four seasons, m represents the total number of lines, and Balan represents the mean of the variance of the load rates of m lines and their neighboring lines.

[0075] In specific embodiments, such as Figure 2As shown, the operation information of the 10kV distribution network line is initialized, useless parameter information is filtered out, and the iteration number is set to 0. The power parameters of each node are calculated through the feeder optimization model. The power parameters include at least the load value of each node, the corresponding power loss value, the node power consumption value, and the voltage at the end of the branch. It is determined whether the power parameters of each node meet the preset judgment conditions or whether the iteration number is greater than the preset iteration threshold. If the preset judgment conditions are not met or the iteration number is not greater than the preset iteration threshold, the power parameters of each node are recalculated and the iteration number is incremented by one. If the preset judgment conditions are met or the iteration number is greater than the preset iteration threshold, the power of the balancing node is output as the calculation result. The forward-backward substitution method first sets the initial voltage value of each node, then pushes the power flow distribution forward from the end node to the root node, and then pushes the voltage of each node backward from the root node to the end node. It is not affected by the branch R / X value, converges quickly, and has a short solution time. The forward-backward substitution method is divided into a forward process and a backward process. The forward process is used to solve the current of each branch and the power at the beginning of each branch, and the backward process is used to solve the voltage of each node.

[0076] Specifically, based on the power flow calculation results, the technical specifications of the i-th 10kV line are calculated.

[0077] FZmax(i)=max{p(i,1),p(i,2),…,p(i,k)} / Syx(i)

[0078] FZmin(i)=min{p(i,1),p(i,2),…,p(i,k)} / Syx(i)

[0079] DYmax(i)=max{V(i,1),V(i,2),…,V(i,k)}

[0080] DYmax(i)=min{V(i,1),V(i,2),…,V(i,k)}

[0081] Where FZmax(i) represents the maximum load rate, FZmin(i) represents the minimum load rate, DYmax(i) represents the highest voltage value, DYmax(i) represents the lowest voltage value, p(i,k) represents the first segment power of the i-th line at time k, V(i,k) represents the end voltage of the i-th line at time k, and Syx(i) represents the transmission capacity of the i-th line.

[0082] Based on the corresponding evaluation indicators, it is determined whether there are any issues that need optimization. If so, optimization is required; otherwise, optimization is not required. In other words, issues such as heavy overload, large branches, and unreasonable load distribution on 10kV lines within the power supply grid can be addressed through a comprehensive optimization of two modification measures: "large branch load switching" and "main line heavy overload load transfer."

[0083] In this embodiment, when the maximum load rate is greater than 80% and less than or equal to 100%, the corresponding line is determined to be overloaded.

[0084] When the minimum load rate is less than 20%, the corresponding line is considered lightly loaded.

[0085] If a line is heavily loaded, it is determined that there is a potential safety hazard in the operation of the 10kV distribution network line.

[0086] If a line is lightly loaded, it is determined that the 10kV distribution network line has been over-invested; this indicates that the equipment capacity is not being fully utilized, there is over-investment, and the economy is poor.

[0087] If both heavy loads and light loads exist within the same power supply grid, it is determined that the load distribution of each line within the 10kV distribution network grid is unreasonable and needs to be re-optimized.

[0088] Specifically, it is determined whether the corresponding evaluation indicators meet the preset large branch conditions. If they do, the corresponding branch type is determined. The large branch conditions include: when the branch control load reaches a preset load threshold and the upper limit of the number of users reaches a first user threshold, it is determined to be an industrial load branch; when the branch control load reaches a preset load threshold and the upper limit of the number of users reaches a second user threshold, it is determined to be a commercial load branch. Understandably, if a large branch exists in the power grid, a fault in that branch will significantly impact the reliability of the system's power supply and may cause problems such as branch line overload, long power supply distances, large network losses, and low voltage at the end of the line.

[0089] For a given type of power supply area, it can be determined whether it belongs to a large branch based on the load characteristics, the maximum control load, and the number of connected users. Taking a Class A power supply area as an example: a) The branch control load for industrial loads is 2000kW, and the maximum number of users is 10; b) The branch control load for commercial loads is 2000kW, and the maximum number of users is 10; c) The branch control load for industrial loads is 2000kW, and the maximum number of users is 1000.

[0090] Specifically, unreasonable load distribution mainly refers to the uneven load rates of adjacent lines. Lines with high load rates are prone to safety hazards, while lines with low load rates result in wasted assets. Adjacent lines of a certain 10kV line include lines to the left, right, and opposite sides of the line (with the substation at the beginning of the line in front) with a distance of less than 1000m between nodes, as well as the connecting lines of the line. Assume a certain 10kV line has k-1 adjacent lines, plus the line itself, for a total of k lines. Calculate the load rate variance of the line using the following formula:

[0091]

[0092]

[0093] Where Fbal represents the load rate variance of k lines, FZ(i,t) represents the load rate of the i-th line at time t, JFZ(t) represents the average load rate of all lines at time t, and 96 corresponds to the total number of time periods per day representing the four seasons.

[0094] When the load factor variance of a line exceeds a preset variance threshold, it is determined that there is an unreasonable load distribution in the line. If there are simultaneously heavily overloaded and lightly loaded lines among the k lines, or if the load factor variance Fbal of the k lines exceeds the threshold β, it can be determined that there is an unreasonable load distribution among the k lines.

[0095] It should be noted that the feeder optimization model also has constraints, including: radial line constraints; line capacity control meets requirements; branch node capacity control meets requirements; main line power supply radius meets requirements; voltage at each time section does not exceed limits; branch power at each time section does not exceed limits; construction and renovation funds do not exceed given limits.

[0096] like Figure 3 As shown, after a major branch or main line is disconnected from its original line at a certain node, it is transferred to a nearby line from the end, realizing the load transfer of the major branch and the load transfer of the main line. The purpose of solving the model is to determine two sets of optimization variables: the major branch receiving point, the major branch disconnection point, and the cross-section of the new line after the major branch is disconnected; the main line receiving point, the main line disconnection point, and the cross-section of the new line after the main line transfer. If there are ndf major branches and nzg heavy-load lines, then the number of optimization variables is 3(ndf+nzg).

[0097] In summary, implementing the embodiments of the present invention has the following beneficial effects:

[0098] The optimization evaluation method for 10kV distribution network lines provided by this invention takes feeder groups within the power grid as the basic unit for existing power supply areas. It analyzes typical operating scenarios after load point expansion, identifies potential safety hazards in 10kV line operation, and proposes a comprehensive optimization method for 10kV line renovation schemes that simultaneously considers load transfer on the main line and the relocation of large branches. This method eliminates hidden safety risks in line operation, achieves load balancing between lines, and thus ensures the economy and safety of the distribution network renovation scheme.

[0099] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for optimizing and evaluating 10kV distribution network lines, characterized in that, include: Obtain operational information for 10kV distribution network lines; The operation information of the 10kV distribution network line is calculated by a preset feeder optimization model to obtain various corresponding evaluation indicators; wherein, the evaluation indicators include at least the maximum load rate, minimum load rate, highest voltage value and lowest voltage value. Based on the evaluation indicators corresponding to each item, it is determined whether there are any problems to be optimized. If there are, it is determined that optimization is needed; if not, it is determined that optimization is not needed. The feeder optimization model specifically includes: in, f Let represent the objective function of the feeder optimization model. f 1 represents the annual increase in cost. f 2 indicates load balancing within the grid. C INV This indicates the annual investment cost for newly built lines. This indicates the annual cost of line loss. α Indicates the weight. This represents the annual cost conversion factor for the route. This represents the investment cost per unit length of the line. Indicates the first i The length of the newly built line, This represents the annual interest rate in the power industry. zm Indicates the number of newly built lines. n Indicates the service life of the line; The feeder optimization model also includes: in, This indicates the annual cost of line loss. Indicates the first i The number of days in each season Indicates the first i Season k Hourly power loss Indicates the first i Season k The unit electricity cost per hour; BFZ ( i , j , t ) indicates the first t Time of the first i The first of the lines j Load rate of neighboring lines BJFZ ( i , t )express t Time of the first i The average load rate of all adjacent lines of the line. k This indicates the maximum number of adjacent routes; 96 corresponds to the four seasons and represents the total number of time periods per day. m Indicates the total number of lines. Balan This represents the mean of the variance of the load rates of m lines and their neighboring lines.

2. The method as described in claim 1, characterized in that, The operational information of the 10kV distribution network lines includes at least the following: Location of substations, main transformer models and capacities within the power supply grid; The topology, line segment type, cross-sectional information, length information, load point location, load point capacity, and representative daily load curves for all 10kV lines within the power supply grid in spring, summer, autumn, and winter; Location information, capacity information, and typical load curves for load point expansion.

3. The method as described in claim 1, characterized in that, The calculation of the operation information of the 10kV distribution network line using a preset feeder optimization model specifically includes: The operation information of the 10kV distribution network line is initialized, useless parameter information is filtered out, and the iteration number is set to 0; The power parameters of each node are calculated using a feeder optimization model. These power parameters include at least the load value of each node, the corresponding power loss value, the node power consumption value, and the voltage at the end of the branch. Determine whether the power parameters of each node meet the preset judgment conditions or whether the number of iterations is greater than the preset iteration threshold. If the preset judgment conditions are not met or the number of iterations is not greater than the preset iteration threshold, recalculate the power parameters of each node and increment the number of iterations by one. If the preset judgment conditions are met or the number of iterations is greater than the preset iteration threshold, output the power of the balancing node as the calculation result.

4. The method as described in claim 3, characterized in that, Calculate the corresponding evaluation indicators for each item using the following formula: in, Indicates the maximum load rate. Indicates the minimum load rate. This indicates the highest voltage value. Indicates the minimum voltage value. This represents the power at the beginning of the i-th line at time k. This represents the terminal voltage of the i-th line at time k. This represents the transmission capacity of the i-th line.

5. The method as described in claim 4, characterized in that, The process of evaluating and determining whether there are problems to be optimized based on the corresponding evaluation indicators of each item specifically includes: When the maximum load rate is greater than 80% and less than or equal to 100%, the corresponding line is determined to be overloaded. When the minimum load rate is less than 20%, the corresponding line is considered lightly loaded. If a line is heavily loaded, it is determined that there is a potential safety hazard in the operation of the 10kV distribution network line. If a line is lightly loaded, it is determined that the 10kV distribution network line has been over-invested. If both heavy loads and light loads exist within the same power supply grid, it is determined that the load distribution of each line within the 10kV distribution network grid is unreasonable and needs to be re-optimized.

6. The method as described in claim 5, characterized in that, The process of evaluating and determining whether there are problems to be optimized based on the corresponding evaluation indicators also includes: Determine whether the corresponding evaluation indicator meets the preset major branch conditions. If it does, determine the corresponding branch type. The large branch conditions include, When the branch control load reaches the preset load threshold and the upper limit of the number of users reaches the first user threshold, it is determined to be an industrial load branch. When the branch control load reaches the preset load threshold and the upper limit of the number of users reaches the second user threshold, it is determined to be a commercial load branch.

7. The method as described in claim 6, characterized in that, The process of evaluating and determining whether there are problems to be optimized based on the corresponding evaluation indicators also includes: Calculate the load factor variance of the line using the following formula: in, Fbal This represents the variance of the load factor of the k lines. FZ ( i , t ) indicates the first i Line t Load rate at any given time JFZ ( t )express t The average load rate of all lines at any given time; 96 corresponds to the total number of time periods per day in each of the four seasons. When the load factor variance of a line exceeds a preset variance threshold, it is determined that there is an unreasonable load distribution in the line.

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