Direct current optimal power flow calculation method and system based on power grid ring characteristic

Abstract

The application discloses a DC optimal power flow calculation method based on grid ring characteristics, comprising the following steps: obtaining data information of a target grid; merging all double-circuit lines in the target grid into single-circuit lines and defining basic ring networks in the target grid; calculating the number of the basic ring networks; calculating a basic ring network set; generating a basic ring network factor matrix and constructing corresponding ring network characteristic constraints; establishing a fast DC optimal power flow model and solving the model to complete the DC optimal power flow calculation based on the grid ring characteristics. The application further discloses a system for realizing the DC optimal power flow calculation based on the grid ring characteristics. The application realizes the improvement of the solving efficiency of the model when processing large-scale complex grids, greatly reduces the number of variables and constraints in the DC optimal power flow model, significantly reduces the calculation complexity of the model, realizes the accurate depiction of the grid topology structure, and has high reliability, good accuracy and wide application range.

Description

Technical Field

[0001] This invention belongs to the field of electrical automation, and specifically relates to a method and system for calculating optimal DC power flow based on the ring characteristics of the power grid. Background Technology

[0002] With economic and technological development and the improvement of people's living standards, electricity has become an indispensable secondary energy source in people's production and daily life, bringing endless convenience. Therefore, ensuring a stable and reliable supply of electricity has become one of the most important tasks of the power system.

[0003] Currently, the scale and complexity of power systems are increasing dramatically. The efficient operation of power systems is described as a nonlinear optimization problem, namely the optimal power flow modeling problem. Its objective is to optimize the output power of each generator to maximize the efficiency of the entire power system, while simultaneously ensuring system security in areas such as line power flow through a series of grid constraints. Optimal power flow models provide efficient solutions for power system security constraints, dispatch analysis, Nk-cascading failure analysis, and stability analysis.

[0004] The DC optimal power flow calculation scheme is a reasonably simplified method for calculating power flow. This scheme transforms a nonlinear problem into a linear one, allowing the model to be solved quickly using some commercial solvers. However, as a fundamental scheme for power system analysis and calculation, it still suffers from low computational efficiency when dealing with the more complex and larger-scale power grids of today. Furthermore, current DC optimal power flow calculation schemes still cannot meet the requirements for online security analysis of large-scale power grids, such as Nk cascading fault analysis. Summary of the Invention

[0005] One of the objectives of this invention is to provide a highly reliable, accurate, and widely applicable method for calculating optimal DC power flow based on the loop characteristics of the power grid.

[0006] The second objective of this invention is to provide a system for implementing the DC optimal power flow calculation method based on the loop characteristics of the power grid.

[0007] The DC optimal power flow calculation method based on the loop characteristics of the power grid provided by this invention includes the following steps:

[0008] S1. Obtain data information from the target power grid;

[0009] S2. Merge all double-circuit lines in the target power grid into single-circuit lines, and define the basic ring network in the target power grid;

[0010] S3. Based on the number of nodes and the total number of lines in the target power grid obtained in step S2, calculate the number of basic ring networks using topological principles;

[0011] S4. Based on the target power grid obtained in step S2 and the number of basic ring networks obtained in step S3, calculate the set of basic ring networks;

[0012] S5. Based on the set of basic ring networks obtained in step S4, generate the basic ring network factor matrix and construct the corresponding ring network characteristic constraints;

[0013] S6. Based on the basic ring network factor matrix and corresponding ring network characteristic constraints obtained in step S5, establish and solve the fast DC optimal power flow model to complete the DC optimal power flow calculation based on the ring characteristics of the power grid.

[0014] Step S2, which involves merging all double-circuit lines in the target power grid into single-circuit lines and defining the basic ring network in the target power grid, specifically includes the following steps:

[0015] The power flow limits of all double-circuit lines in the target power grid are added together, and the remaining information is kept unchanged, thereby merging all double-circuit lines in the target power grid into a single-circuit line.

[0016] The structure of the target power grid consisting of only a single ring network is defined as the basic ring network P. i .

[0017] Step S3, which involves calculating the number of basic ring networks based on the number of nodes and the total number of lines in the target power grid obtained in step S2, using topological principles, specifically includes the following steps:

[0018] Based on the number of nodes N in the target power grid obtained in step S2 B Total number of lines N L The number N of basic ring networks was calculated using topological principles. P For N P =N L -N B +1.

[0019] Step S4, which involves calculating the basic ring network set based on the target power grid obtained in step S2 and the number of basic ring networks obtained in step S3, specifically includes the following steps:

[0020] A. Initialize the basic ring network set T as an empty set and the line number k as 0; K is the set of topology information for all lines in the target power grid;

[0021] B. Increase the value of line number k by 1;

[0022] C. Disconnect nodes a and b connected by line k, and determine whether nodes a and b in the target power grid are connected:

[0023] If there is no connecting path between node a and node b, return to step B;

[0024] If there is a connected path between node a and node b, then determine the shortest path between node a and node b, extract the set of lines p contained in the determined shortest path, and proceed with subsequent steps.

[0025] D. Record the basic ring network P of line k. k For P k = (p,k); The basic ring network P k Add to the basic ring network set T;

[0026] E. Determine the value of k:

[0027] If k = N L Then the basic ring network set T is output;

[0028] If k < N L If so, remove the information of line k from the topology information set K of all lines in the current target power grid, use the updated power grid as the new target power grid, and return to step B.

[0029] Step C, determining the shortest path between node a and node b, specifically involves using a directed graph function pathfinding algorithm to determine the shortest path and the corresponding set of paths, where the weight of each path is set to 1.

[0030] Step S5, which involves generating a basic ring network factor matrix based on the basic ring network set obtained in step S4 and constructing corresponding ring network characteristic constraints, specifically includes the following steps:

[0031] Using the basic ring network set T, generate the basic ring network factor matrix A. S : Basic ring network P of line k k For P k = (p,k), then the basic ring network factor matrix A S The element in the k-th row and l-th column for in For line l in the basic ring network P k In the state of the basic ring network P k If line l is not included If the basic ring network P k According to the forward route l If the basic ring network P k According to the reverse route l The term "forward" is defined as the direction of the ring network path from the starting point to the ending point of the line; the term "reverse" is defined as the direction of the ring network path from the ending point to the starting point of the line.

[0032] Using the basic ring network factor matrix A S Constructing ring network characteristic constraints:

[0033]

[0034] In the formula δ l x is the phase angle of line l; l f is the impedance of line l; l Here is the power flow value for line l;

[0035] Finally, the constructed ring network characteristic constraints are expressed as A. S • F = 0; F is the line power flow matrix.

[0036] Step S6, which involves establishing and solving a fast DC optimal power flow model based on the basic ring network factor matrix and corresponding ring network characteristic constraints obtained in step S5, to complete the DC optimal power flow calculation based on the ring characteristics of the power grid, specifically includes the following steps:

[0037] The following formula is used to construct a fast DC optimal power flow model:

[0038] Objective function:

[0039] Constraints:

[0040]

[0041] A S ·F=0

[0042] W·F=U·PV·D

[0043] In the formula |N G | represents the number of generating units in the target power grid; C g The operating cost of unit g; P g Let g be the generator output power of unit g; Let g be the minimum output power of the generator in unit g. N is the maximum output power of the generator of unit g; G For the set of generating units in the target power grid; f l f is the power flow value of line l; l max N represents the maximum power flow limit value for line l; L Let W be the set of lines in the target power grid; W be the line-node connection matrix of the target power grid; U be the generator-node connection matrix of the target power grid; P be the generator output power vector of the target power grid; V be the load-node connection matrix of the target power grid; and D be the load vector of the target power grid.

[0044] Solving the model constructed above yields the optimal operating parameters of the target power grid, completing the DC optimal power flow calculation based on the grid loop characteristics; among which, the optimal operating parameters include generator output power information and line power flow matrix.

[0045] This invention also provides a system for implementing the DC optimal power flow calculation method based on the ring characteristics of the power grid, comprising a data acquisition module, a power grid processing module, a ring network quantity calculation module, a ring network ensemble calculation module, a ring network constraint construction module, and a power flow calculation module; the data acquisition module, power grid processing module, ring network quantity calculation module, ring network ensemble calculation module, ring network constraint construction module, and power flow calculation module are connected in series; the data acquisition module is used to acquire data information of the target power grid and upload the data to the power grid processing module; the power grid processing module is used to merge all double-circuit lines in the target power grid into single-circuit lines according to the received data, and define the basic ring network in the target power grid. The data is then uploaded to the ring network quantity calculation module. This module calculates the number of basic ring networks based on the received data using topological principles and uploads the data to the ring network set calculation module. The ring network set calculation module calculates the basic ring network set based on the received data and uploads the data to the ring network constraint construction module. The ring network constraint construction module generates a basic ring network factor matrix based on the received data, constructs corresponding ring network characteristic constraints, and uploads the data to the power flow calculation module. The power flow calculation module establishes and solves a fast DC optimal power flow model based on the received data, completing the DC optimal power flow calculation based on the ring characteristics of the power grid.

[0046] This invention provides a method and system for calculating optimal DC power flow based on the ring characteristics of a power grid. It proposes a fast method for calculating optimal DC power flow based on the ring characteristics of the power grid, improving the solution efficiency of the model when dealing with large-scale complex power grids. Simultaneously, based on the ring characteristics of the power grid, this invention establishes ring network characteristic constraints, greatly reducing the number of variables and constraints in the optimal DC power flow model, significantly reducing the computational complexity of the model, and breaking away from the fixed thinking of traditional optimal DC power flow calculation methods. It fully utilizes the power grid topology and ring characteristics to improve the model's solution efficiency. Furthermore, this invention proposes an innovative algorithm to find all basic ring networks in the power grid, providing a method for determining the set of basic ring networks and the constituent elements of the basic ring network factor matrix, achieving an accurate characterization of the power grid topology. Therefore, this invention has high reliability, good accuracy, and a wide range of applications. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the method flow of the present invention.

[0048] Figure 2 This is a schematic diagram of the functional modules of the system of the present invention. Detailed Implementation

[0049] like Figure 1 The diagram shown is a flowchart of the method of the present invention: The DC optimal power flow calculation method based on the ring characteristics of the power grid provided by the present invention includes the following steps:

[0050] S1. Obtain data information from the target power grid;

[0051] S2. Merge all double-circuit lines in the target power grid into single-circuit lines, and define the basic ring network in the target power grid; specifically including the following steps:

[0052] The power flow limits of all double-circuit lines in the target power grid are added together, and the remaining information is kept unchanged, thereby merging all double-circuit lines in the target power grid into a single-circuit line.

[0053] The structure in the target power grid that includes only a single ring network is defined as the basic ring network P. i Basic ring network P i No other basic ring network will appear in it, that is, it does not contain any other loops inside;

[0054] S3. Based on the number of nodes and the total number of lines in the target power grid obtained in step S2, calculate the number of basic ring networks using topological principles; specifically, this includes the following steps:

[0055] Based on the number of nodes N in the target power grid obtained in step S2 B Total number of lines N L The number N of basic ring networks was calculated using topological principles. P For N P =N L -N B +1;

[0056] S4. Based on the target power grid obtained in step S2 and the number of basic ring networks obtained in step S3, calculate the set of basic ring networks; specifically including the following steps:

[0057] A. Initialize the basic ring network set T as an empty set and the line number k as 0; K is the set of topology information for all lines in the target power grid;

[0058] B. Increase the value of line number k by 1;

[0059] C. Disconnect nodes a and b connected by line k, and determine whether nodes a and b in the target power grid are connected:

[0060] If there is no connecting path between node a and node b, return to step B;

[0061] If there is a connected path between node a and node b, then determine the shortest path between node a and node b (i.e. the path with the fewest number of lines), extract the set p of lines contained in the determined shortest path, and proceed with the subsequent steps.

[0062] In practice, a pathfinding algorithm with directed graph functions is used to determine the shortest path and the corresponding set of paths, where the weight of each path is set to 1.

[0063] D. Record the basic ring network P of line k. k For P k = (p,k); The basic ring network P k Add to the basic ring network set T;

[0064] E. Determine the value of k:

[0065] If k = N L Then the basic ring network set T is output;

[0066] If k < N L If so, remove the information of line k from the topology information set K of all lines in the current target power grid, use the updated power grid as the new target power grid, and return to step B.

[0067] S5. Based on the basic ring network set obtained in step S4, generate the basic ring network factor matrix and construct the corresponding ring network characteristic constraints; specifically including the following steps:

[0068] Using the basic ring network set T, generate the basic ring network factor matrix A. S : Basic ring network P of line k k For P k = (p,k), then the basic ring network factor matrix A S The element in the k-th row and l-th column for in For line l in the basic ring network P k In the state of the basic ring network P k If line l is not included If the basic ring network P k According to the forward route l If the basic ring network P k According to the reverse route l The term "forward" is defined as the ring network path direction from the start point to the end point of the line; the term "reverse" is defined as the ring network path direction from the end point to the start point of the line; the basic ring network factor matrix A S The dimension is N P ×N L ;

[0069] Using the basic ring network factor matrix A S Constructing ring network characteristic constraints:

[0070]

[0071] In the formula δ l x is the phase angle of line l; l f is the impedance of line l; l The power flow value for line l; because the basic ring network P k All lines in the circuit can be connected end to end to form a loop, therefore the sum of the phase angles of all lines must be 0;

[0072] Finally, the constructed ring network characteristic constraints are expressed as A. S • F = 0; F is the line power flow matrix;

[0073] S6. Based on the basic ring network factor matrix and corresponding ring network characteristic constraints obtained in step S5, establish and solve the fast DC optimal power flow model to complete the DC optimal power flow calculation based on the ring characteristics of the power grid; specifically including the following steps:

[0074] The following formula is used to construct a fast DC optimal power flow model:

[0075] Objective function:

[0076] Constraints:

[0077]

[0078] A S ·F=0

[0079] W·F=U·PV·D

[0080] In the formula |N G | represents the number of generating units in the target power grid; C g The operating cost of unit g; P g Let g be the generator output power of unit g; Let g be the minimum output power of the generator in unit g. N is the maximum output power of the generator of unit g; G For the set of generating units in the target power grid; f l f is the power flow value of line l; l max N represents the maximum power flow limit value for line l; LLet W be the set of lines in the target power grid; W be the line-node connection matrix of the target power grid; U be the generator-node connection matrix of the target power grid; P be the generator output power vector of the target power grid; V be the load-node connection matrix of the target power grid; and D be the load vector of the target power grid.

[0081] Solving the model constructed above yields the optimal operating parameters of the target power grid, completing the DC optimal power flow calculation based on the grid loop characteristics; among which, the optimal operating parameters include generator output power information and line power flow matrix.

[0082] like Figure 2 The diagram shows the functional modules of the system of this invention: The system disclosed in this invention, which implements the DC optimal power flow calculation method based on the ring characteristics of the power grid, includes a data acquisition module, a power grid processing module, a ring network quantity calculation module, a ring network ensemble calculation module, a ring network constraint construction module, and a power flow calculation module; these modules are connected in series. The data acquisition module acquires data information of the target power grid and uploads the data to the power grid processing module. The power grid processing module, based on the received data, merges all double-circuit lines in the target power grid into single-circuit lines and defines the target... The system first calculates the number of basic ring networks in the power grid and uploads the data to the ring network quantity calculation module. The ring network quantity calculation module calculates the number of basic ring networks using topological principles based on the received data and uploads the data to the ring network set calculation module. The ring network set calculation module calculates the set of basic ring networks based on the received data and uploads the data to the ring network constraint construction module. The ring network constraint construction module generates a basic ring network factor matrix based on the received data, constructs corresponding ring network characteristic constraints, and uploads the data to the power flow calculation module. The power flow calculation module establishes and solves a fast DC optimal power flow model based on the received data, completing the DC optimal power flow calculation based on the ring characteristics of the power grid.

Claims

1. A method for calculating optimal DC power flow based on the loop characteristics of a power grid, comprising the following steps: S1. Obtain data information from the target power grid; S2. Merge all double-circuit lines in the target power grid into single-circuit lines, and define the basic ring network in the target power grid; S3. Based on the number of nodes and the total number of lines in the target power grid obtained in step S2, calculate the number of basic ring networks using topological principles; S4. Based on the target power grid obtained in step S2 and the number of basic ring networks obtained in step S3, calculate the set of basic ring networks; specifically including the following steps: A. Initialize the basic ring network set Empty set, line number =0; This is the set of topology information for all lines in the target power grid; B. Line number The value increases by 1; C. The line The two connected nodes a and b are disconnected, and it is determined whether nodes a and b in the target power grid are connected: If there is no connecting path between node a and node b, return to step B; If there is a connected path between node a and node b, then determine the shortest path between node a and node b, extract the set of lines p contained in the determined shortest path, and proceed with subsequent steps. D. Record the route Basic ring network for ; the basic ring network Add to basic ring network set middle; E. Determine the value: like Then the basic ring network set will be output. ; like Then, in the current target power grid, the topology information set of all lines... Remove line The updated power grid is used as the new target power grid, and the process returns to step B. S5. Based on the basic ring network set obtained in step S4, generate the basic ring network factor matrix and construct the corresponding ring network characteristic constraints; specifically including the following steps: Using basic ring network set Generate the basic ring network factor matrix :line Basic ring network for Then the basic ring network factor matrix The Middle Line number Column elements for ,in For the line In the basic ring network In the state of the basic ring network The middle does not include the line but If the basic ring network Following the route in the forward direction but If the basic ring network According to the reverse route but The term "forward" is defined as the direction of the ring network path from the starting point to the ending point of the line; the term "reverse" is defined as the direction of the ring network path from the ending point to the starting point of the line. Using the basic ring network factor matrix Constructing ring network characteristic constraints: In the formula For the line The phase angle; For the line impedance; For the line Trend value; Finally, the constructed ring network characteristic constraints are expressed as follows: ; For line power flow matrix; S6. Based on the basic ring network factor matrix and corresponding ring network characteristic constraints obtained in step S5, establish and solve the fast DC optimal power flow model to complete the DC optimal power flow calculation based on the ring characteristics of the power grid; specifically including the following steps: The following formula is used to construct a fast DC optimal power flow model: Objective function: Constraints: In the formula The number of generating units in the target power grid; For the unit Operating costs; For the unit The generator output power; For the unit The minimum output power of the generator; For the unit The maximum output power of the generator; The set of generating units in the target power grid; For the line Trend value; For the line Maximum tidal current limit value; The set of lines in the target power grid; The line-node connection matrix of the target power grid; The generator-node connection matrix of the target power grid; The generator output power vector of the target power grid; The load-node connection matrix of the target power grid; The load vector of the target power grid; Solving the model constructed above yields the optimal operating parameters of the target power grid, completing the DC optimal power flow calculation based on the grid loop characteristics; among which, the optimal operating parameters include generator output power information and line power flow matrix.

2. The DC optimal power flow calculation method based on the loop characteristics of the power grid according to claim 1, characterized in that... Step S2, which involves merging all double-circuit lines in the target power grid into single-circuit lines and defining the basic ring network in the target power grid, specifically includes the following steps: The power flow limits of all double-circuit lines in the target power grid are added together, and the remaining information is kept unchanged, thereby merging all double-circuit lines in the target power grid into a single-circuit line. A basic ring network is defined as a structure in the target power grid that consists of only a single ring network. .

3. The DC optimal power flow calculation method based on the loop characteristics of the power grid according to claim 2, characterized in that... Step S3, which involves calculating the number of basic ring networks based on the number of nodes and the total number of lines in the target power grid obtained in step S2, using topological principles, specifically includes the following steps: Based on the number of nodes in the target power grid obtained in step S2 Total number of lines The number of basic ring networks was calculated using topological principles. for .

4. The DC optimal power flow calculation method based on the loop characteristics of the power grid according to claim 3, characterized in that... Step C, determining the shortest path between node a and node b, specifically involves using a directed graph function pathfinding algorithm to determine the shortest path and the corresponding set of paths, where the weight of each path is set to 1.

5. A system for implementing the DC optimal power flow calculation method based on the loop characteristics of the power grid as described in any one of claims 1 to 4, characterized in that... It includes a data acquisition module, a power grid processing module, a ring network quantity calculation module, a ring network ensemble calculation module, a ring network constraint construction module, and a power flow calculation module; these modules are connected in series. The data acquisition module acquires data information from the target power grid and uploads it to the power grid processing module. The power grid processing module, based on the received data, merges all double-circuit lines in the target power grid into single-circuit lines, defines the basic ring network in the target power grid, and uploads the data to the ring network quantity calculation module. The ring network quantity calculation module calculates the number of basic ring networks based on the received data using topological principles and uploads the data to the ring network set calculation module. The ring network set calculation module calculates the basic ring network set based on the received data and uploads the data to the ring network constraint construction module. The ring network constraint construction module generates the basic ring network factor matrix based on the received data, constructs the corresponding ring network characteristic constraints, and uploads the data to the power flow calculation module. The power flow calculation module is used to establish and solve a fast DC optimal power flow model based on the received data, and complete the DC optimal power flow calculation based on the ring characteristics of the power grid.

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