Transmission and distribution network power flow analysis method and device based on graph calculation and graph trace analysis

Abstract

The invention discloses a transmission and distribution network power flow analysis method and device based on graph calculation and graph trace analysis, and the method comprises the steps: constructing a power transmission and distribution network graph model corresponding to a power transmission and distribution network topological relation according to a basic form of a representation graph in a graph database; adding attributes to nodes and edges in the power transmission and distribution network graph model according to collected parameter data of the power transmission and distribution network; importing data information of nodes and branches in the power transmission and distribution network into the power transmission and distribution network graph model; setting a global accumulator and a node accumulator, and assigning values to the global accumulator and the node accumulator; path searching is carried out through a graph node parallel computing strategy, and the number of layers where nodes are located is updated; and carrying out load flow calculation and convergence precision judgment through a graph trace analysis method, ending calculation when an iteration result meets set convergence precision, and outputting a calculation result. According to the method, the load flow calculation speed is increased, the calculation precision is ensured, and meanwhile, the non-convergence problem of a traditional Newton method can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of power flow calculation in power grid transmission and distribution networks, and particularly relates to a method and device for power flow analysis of transmission and distribution networks based on graph calculation and graph trace analysis. Background Art

[0002] With the expansion of urban scale, increase in population, rapid economic growth, and improvement of industrialization level, the scale of regional power grids is constantly expanding, the operation mode is becoming increasingly complex, and the integrated operation mode of transmission and distribution grids has become an inevitable requirement for the future development of power grid dispatching services. In traditional transmission and distribution grid planning, the power flow calculations of the main grid and the distribution grid have always been carried out separately. On the one hand, it is because the hierarchical management mode of the power grid causes the dispatching operation and planning design of the transmission and distribution grids to be carried out separately. On the other hand, it is because the grid frame structures and parameter characteristics of the transmission and distribution grids are different, so different methods are used for the simulation calculations of the transmission and distribution grids. In the context of the development of smart grids, the distributed new energy connected to the distribution grid is gradually increasing, and the access of distributed power sources may change the single-end power flow characteristics of the traditional distribution grid. At this time, the distribution grid cannot be directly equivalent to a virtual fixed load, the power flow of the transmission and distribution grid will be bidirectional, and the coupling relationship is also increasing day by day. Therefore, the independent model algorithm of calculating the distribution grid with the main grid as the generator and the main grid with the distribution grid as the load is no longer applicable, and the assumptions in traditional analysis calculations such as three-phase symmetry of the transmission grid and fluctuations in the distribution grid not affecting the transmission grid no longer hold.

[0003] Regarding the modeling of integrated transmission and distribution networks, the most widely used method currently is the master-slave splitting method. This method is essentially still a hierarchical and approximate model. When the number of feeders under the same distribution root node increases, the convergence of the master-slave splitting method will deteriorate; the ring network and distributed power sources will also deteriorate the convergence of the master-slave splitting algorithm; at the same time, because equivalent processing needs to be carried out for the ring network and distributed power sources, the algorithm will be cumbersome, and the calculation results cannot be accurate. With the development of smart grids, the penetration rate of distributed power sources gradually increases, and the ring network operation mode also gradually increases. Therefore, the applicability of the traditional master-slave splitting method is limited; regarding the power flow calculation of integrated transmission and distribution networks, although the existing improved methods based on the Newton method have made improvements in aspects such as initial value selection and calculation efficiency, based on the calculation principle of the Newton method itself, the establishment and analysis process of the matrix can never be avoided. When applied to large-scale systems, with the growth of the matrix scale, it is still difficult to guarantee the calculation efficiency and accuracy.

[0004] Therefore, how to invent a power flow calculation method that can improve the power flow calculation speed, ensure the calculation accuracy, and avoid the non-convergence problem of the traditional Newton method has become an urgent problem to be solved. Summary of the Invention

[0005] To this end, the present invention provides a power flow analysis method and device for a transmission and distribution network based on graph computing and graph trace analysis. The transmission and distribution network is split into multiple radial networks, and the trees and co-trees in the transmission and distribution networks are identified by means of graph tracing. In each radial part, forward and backward iterative processes are respectively carried out through graph trace analysis to calculate the power flow, and the result is converged by continuously updating the co-tree during the iteration, thereby improving the calculation speed of the power flow and ensuring the calculation accuracy.

[0006] To achieve the above object, the present invention provides the following technical solutions: A power flow analysis method for a transmission and distribution network based on graph computing and graph trace analysis, comprising:

[0007] According to the basic form representing a graph in the graph database, taking generators and loads in the transmission and distribution network as nodes and power lines as edges, a transmission and distribution network graph model corresponding to the topological relationship of the transmission and distribution network is constructed;

[0008] According to the parameter data collected from the transmission and distribution network, attributes are added to the nodes and edges in the transmission and distribution network graph model;

[0009] The data information of the nodes and branches in the transmission and distribution network is imported into the transmission and distribution network graph model;

[0010] A global accumulator and a node accumulator are set, and the global accumulator and the node accumulator are assigned values;

[0011] Path search is carried out through a graph node parallel computing strategy, and the layer number where the node is located is updated;

[0012] Power flow calculation is carried out through graph trace analysis and convergence accuracy judgment is carried out. When the iteration result meets the set convergence accuracy, the calculation is ended and the calculation result is output.

[0013] As a preferred solution of the power flow analysis method for a transmission and distribution network based on graph computing and graph trace analysis, in the process of adding attributes to the nodes and edges in the transmission and distribution network graph model, the node attributes include: node number, real part of voltage, imaginary part of voltage, active power, reactive power, and label; the label includes: slack node, PV node, and PQ node; the edge attributes include: node numbers connected to the edge, resistance, reactance, and edge length.

[0014] As a preferred solution of the power flow analysis method for a transmission and distribution network based on graph computing and graph trace analysis, the functions of the global accumulator include: recording the set of edges, saving voltage values, and saving the number of iterations; the functions of the node accumulator include: storing node voltage and node power information, recording node layer numbers and node voltage changes, and recording node active states.

[0015] As an optimal solution of the power flow analysis method for the transmission and distribution network based on graph calculation and graph trace analysis, the steps of performing power flow calculation and convergence accuracy judgment through the graph trace analysis method are as follows:

[0016] The steps of performing power flow calculation and convergence accuracy judgment through the graph trace analysis method are as follows:

[0017] Decompose the transmission and distribution network graph model into a radial network combination in the form of a distribution network;

[0018] Through forward tracing by the topology iterator, iteratively calculate the injected current of the load node to obtain the iterative current at the beginning of each branch;

[0019] Through backward tracing by the topology iterator, iteratively calculate the voltage drop generated during the transmission of the power flow to obtain the iterative voltage value of each node;

[0020] According to the iterative voltage value of each node, calculate the voltage change amplitude of each node;

[0021] Judge whether the voltage change amplitude meets the set convergence accuracy. If the voltage change amplitude meets the set convergence accuracy, end the calculation and output the calculation result; if the voltage change amplitude does not meet the set convergence accuracy, continue the iterative calculation.

[0022] As an optimal solution of the power flow analysis method for the transmission and distribution network based on graph calculation and graph trace analysis, during the process of forward tracing by the topology iterator, iteratively calculating the injected current of the load node, and obtaining the iterative current at the beginning of each branch, the current calculation formula is:

[0023]

[0024] In the formula, i in is all the currents injected into this node; i out is all the currents flowing out of this node; n is the index of the inflow node, used to traverse all the currents i injected into this node in ; k is the index of the outflow node, used to traverse all the currents i flowing out of this node out ;

[0025] During the process of backward tracing by the topology iterator, iteratively calculating the voltage drop generated during the transmission of the power flow, and obtaining the iterative voltage value of each node, the calculation formula for the node voltage is:

[0026] V i -V j =i ij *(R + jX)

[0027] In the formula, V i, V j is the voltage across both ends of the branch; i ij is the current of the branch; R and X are the resistance and reactance of the branch respectively; i is the current node number; j is the next node number.

[0028] The present invention also provides a power flow analysis device for transmission and distribution network based on graph calculation and graph trace analysis. Based on the above power flow analysis method for transmission and distribution network based on graph calculation and graph trace analysis, it includes:

[0029] A transmission and distribution network graph model construction module, configured to construct a transmission and distribution network graph model corresponding to the topological relationship of the transmission and distribution network, with generators and loads in the transmission and distribution network as nodes and power lines as edges, according to the basic form representing the graph in the graph database.

[0030] A node and edge attribute adding module, configured to add attributes to the nodes and edges in the transmission and distribution network graph model according to the collected parameter data of the transmission and distribution network.

[0031] A node and branch data information importing module, configured to import the data information of nodes and branches in the transmission and distribution network into the transmission and distribution network graph model.

[0032] A global accumulator and node accumulator setting module, configured to set a global accumulator and a node accumulator, and assign values to the global accumulator and the node accumulator.

[0033] A path search and node layer number updating module, configured to perform path search through a graph node parallel computing strategy and update the layer number where the node is located.

[0034] A graph trace analysis method calculation module, configured to perform power flow calculation through the graph trace analysis method and judge the convergence accuracy. When the iteration result meets the set convergence accuracy, end the calculation and output the calculation result.

[0035] As a preferred solution of the power flow analysis device for transmission and distribution network based on graph calculation and graph trace analysis, in the node and edge attribute adding module, during the process of adding attributes to the nodes and edges in the transmission and distribution network graph model, the node attributes include: node number, real part of voltage, imaginary part of voltage, active power, reactive power, and label; the label includes: slack node, PV node, and PQ node; the edge attributes include: node numbers connected to the edge, resistance, reactance, and length of the edge.

[0036] As a preferred solution of the power flow analysis device for transmission and distribution network based on graph calculation and graph trace analysis, in the global accumulator and node accumulator setting module, the functions of the global accumulator include: recording the set of edges, saving voltage values, and saving the number of iterations; the functions of the node accumulator include: storing node voltage and node power information, recording node layer number and node voltage change, and recording node active status.

[0037] As an optimal solution for the power flow analysis device of the transmission and distribution network based on graph calculation and graph trace analysis, in the graph trace analysis calculation module, the power flow calculation sub-module includes:

[0038] A model decomposition sub-module for decomposing the transmission and distribution network graph model into a radial network combination in the form of a distribution network;

[0039] A branch current iterative calculation sub-module for iteratively calculating the injected current of the load node by forward tracing through a topology iterator to obtain the iterative current at the beginning of each branch;

[0040] A node voltage iterative calculation sub-module for iteratively calculating the voltage drop generated during the transmission of the power flow by backward tracing through a topology iterator to obtain the iterative voltage value of each node;

[0041] A voltage change amplitude calculation sub-module for calculating the voltage change amplitude of each node based on the iterative voltage value of each node;

[0042] A convergence accuracy judgment and processing sub-module for judging whether the voltage change amplitude meets the set convergence accuracy. If the voltage change amplitude meets the set convergence accuracy, the calculation is ended and the calculation result is output; if the voltage change amplitude does not meet the set convergence accuracy, the iterative calculation is continued.

[0043] As an optimal solution for the power flow analysis device of the transmission and distribution network based on graph calculation and graph trace analysis, in the branch current iterative calculation sub-module of the graph trace analysis calculation module, during the process of iteratively calculating the injected current of the load node by forward tracing through a topology iterator to obtain the iterative current at the beginning of each branch, the current calculation formula is:

[0044]

[0045] In the formula, i in is all the currents injected into this node; i out is all the currents flowing out of this node; n is the index of the node where the current flows in, used to traverse all the currents i in injected into this node; k is the index of the node where the current flows out, used to traverse all the currents i out flowing out of this node;

[0046] In the node voltage iterative calculation sub-module of the graph trace analysis calculation module, during the process of iteratively calculating the voltage drop generated during the transmission of the power flow by backward tracing through a topology iterator to obtain the iterative voltage value of each node, the calculation formula of the node voltage is:

[0047] V i-V j = i ij *(R + jX)

[0048] where V i , V j are the voltages at both ends of the branch; i ij is the current of this branch; R and X are the resistance and reactance of this branch respectively; i is the current node number; j is the next node number.

[0049] The present invention has the following advantages: According to the basic form representing a graph in the graph database, the present invention constructs a power transmission and distribution network graph model corresponding to the topological relationship of the power transmission and distribution network, with generators and loads in the power transmission and distribution network as nodes and power lines as edges; according to the collected parameter data of the power transmission and distribution network, attributes are added to the nodes and edges in the power transmission and distribution network graph model; the data information of the nodes and branches in the power transmission and distribution network is imported into the power transmission and distribution network graph model; a global accumulator and a node accumulator are set, and the global accumulator and the node accumulator are assigned values; path search is performed through a graph node parallel computing strategy, and the layer where the node is located is updated; power flow calculation is performed through a graph trace analysis method and convergence accuracy judgment is carried out. When the iteration result meets the set convergence accuracy, the calculation ends and the calculation result is output. By combining the graph database with the graph trace analysis calculation, the present invention solves, in a parallel computing manner, the problem that the power flow calculation of a node in a node layer in the traditional power flow calculation method needs to wait for the power flow calculation of the previous node to end before it can be carried out, thereby greatly shortening the time required for the power flow calculation of the power system. The present invention avoids large-scale matrix calculations and effectively solves problems such as serious ill-conditioning of the Newton method Jacobian matrix and poor convergence performance in the traditional integrated calculation of power transmission and distribution networks. In the calculation of each radial network, due to the use of this graph parallel technology, the convergence speed of the power flow calculation of each "tree" can also be increased by about 80%. The present invention proposes a method for calculating the integrated power transmission and distribution network power flow by combining graph calculation and graph trace analysis. The power system data is input into the graph database analysis platform, and the power transmission and distribution network is modeled. Then, using the graph trace analysis method, a topological iterator is used to move between the components in the model and perform calculations to solve the system power flow. The present invention can implement large-scale power transmission and distribution network power flow calculation through parallel computing. The proposed algorithm not only solves the problem of difficult accurate power flow calculation of the power transmission and distribution network, but also avoids large-scale matrix calculations and improves the calculation speed. Description of the Drawings

[0050] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only exemplary. For those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained by extending the provided drawings.

[0051] The structures, proportions, sizes, etc. illustrated in this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have technical substantive significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention.

[0052] Figure 1 Schematic flow diagram of the power flow analysis method for the transmission and distribution network based on graph calculation and graph trace analysis provided in Embodiment 1 of the present invention;

[0053] Figure 2 Schematic demonstration diagram of path search and node layer number update in the power flow analysis method for the transmission and distribution network based on graph calculation and graph trace analysis provided in Embodiment 1 of the present invention;

[0054] Figure 3 Schematic flow diagram of the graph trace analysis method in the power flow analysis method for the transmission and distribution network based on graph calculation and graph trace analysis provided in Embodiment 1 of the present invention;

[0055] Figure 4 Power distribution network performance test results in the power flow analysis method for the transmission and distribution network based on graph calculation and graph trace analysis provided in Embodiment 1 of the present invention;

[0056] Figure 5 Schematic diagram of the Newton - Raphson method in the power flow analysis method for the transmission and distribution network based on graph calculation and graph trace analysis provided in Embodiment 1 of the present invention;

[0057] Figure 6 Schematic architecture diagram of the power flow analysis device for the transmission and distribution network based on graph calculation and graph trace analysis provided in Embodiment 2 of the present invention. Specific embodiments

[0058] The following specific embodiments illustrate the embodiments of the present invention. Those familiar with this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by the present invention.

[0059] Example 1

[0060] Refer to Figure 1 , Example 1 of the present invention provides a power flow analysis method for a power transmission and distribution network based on graph computing and graph trace analysis, including the following steps:

[0061] S1. According to the basic form of the graph represented in the graph database, taking generators and loads in the power transmission and distribution network as nodes and power lines as edges, construct a power transmission and distribution network graph model corresponding to the topological relationship of the power transmission and distribution network;

[0062] S2. According to the collected parameter data of the power transmission and distribution network, add attributes to the nodes and edges in the power transmission and distribution network graph model;

[0063] S3. Import the data information of the nodes and branches in the power transmission and distribution network into the power transmission and distribution network graph model;

[0064] S4. Set a global accumulator and a node accumulator, and assign values to the global accumulator and the node accumulator;

[0065] S5. Perform path search through the graph node parallel computing strategy, and update the layer where the node is located;

[0066] S6. Perform power flow calculation through the graph trace analysis method and judge the convergence accuracy. When the iteration result meets the set convergence accuracy, end the calculation and output the calculation result.

[0067] In this embodiment, in step S1, according to the basic form of the graph represented in the graph database, taking generators and loads in the power transmission and distribution network as nodes and power lines as edges, construct a power transmission and distribution network graph model corresponding to the topological relationship of the power transmission and distribution network;

[0068] Specifically, a graph is a mathematical structure used to represent a set of objects (vertices) and their mutual relationships (edges). In mathematics, a graph can usually be represented as G=(V, E), where V represents a set of vertices, representing the objects in graph G, and the set of edges represents the relationships between the objects, represented by E, expressing how these vertices are associated. Each edge in E can be represented as e=(i, j), and at this time, i and j can be called the head and tail of edge E as nodes in V respectively.

[0069] A graph can be directed or undirected. For an undirected graph, the relationship between two connected vertices is bidirectional, and there is no difference between the two directions. Therefore, graphs are also widely used to simulate complex relationships in the real world.

[0070] A graph database is a database system that stores and queries data in a graph structure. It represents data through vertices, edges, and attributes, supports efficient graph traversal and complex relationship queries, and is suitable for processing highly interconnected data and complex network structures.

[0071] In the power system, various different nodes (generator nodes, load nodes, transformer nodes) are connected by lines between the nodes. Therefore, the nodes and branches in the power system can be corresponding to the vertices and edges in the graph data, and both the nodes and the lines have their own data structures.

[0072] When it is necessary to express the power system structure in the graph database, it is necessary to model it first. In order to construct the power transmission and distribution network graph database model, the power transmission and distribution network needs to be defined as a graphic network G(V, E), where V is the set of nodes, including generator nodes, load nodes, and balance nodes, and E is the set of branches. The power parameters included in the nodes and branches are stored as the attributes of the graph network nodes and edges. The nodes are connected by directed edges, so that the power graph model is converted into a graph model.

[0073] In this embodiment, generators and loads in the power transmission and distribution network are used as nodes, and power lines are used as edges to construct a power transmission and distribution network graph model corresponding to the topological relationship of the power transmission and distribution network.

[0074] In this embodiment, in step S2, according to the parameter data collected from the power transmission and distribution network, attributes are added to the nodes and edges in the power transmission and distribution network graph model;

[0075] Specifically, in order to enable each node and edge to complete independent calculations subsequently, it is also necessary to add attributes and assign data to them. Node attributes include: node number, real part of voltage, imaginary part of voltage, active power P, reactive power Q, and label; the label type includes: balance node, PV node, and PQ node; edge attributes include: node numbers connected to the edge, resistance R, reactance X, and length L of the edge.

[0076] In this embodiment, in step S3, the data information of the nodes and branches in the power transmission and distribution network is imported into the power transmission and distribution network graph model;

[0077] Specifically, the preprocessed node information is imported into the graph database platform to provide data preparation for subsequent graph calculations. The node data information and line data information are converted into.csv format and then imported into the graph database. The imported data is linked to the node attributes and edge attributes in the graph model one by one. Check whether the data is completely imported into the graph model, and check the integrity and accuracy of the topological structure.

[0078] In this embodiment, in step S4, a global accumulator and a node accumulator are set, and the global accumulator and the node accumulator are assigned values;

[0079] Among them, the functions of the global accumulator include: recording the set of edges, saving voltage values, and saving the number of iterations; the functions of the node accumulator include: storing node voltages and node power information, recording node levels and node voltage changes, and recording node active states.

[0080] In this embodiment, the nodes are initialized, and information such as the active power, reactive power, and real part of the voltage of each node is saved in the corresponding node accumulator. In the subsequent calculation process, the flow of information between nodes is realized through the node accumulator.

[0081] In this embodiment, the settings of the accumulator type and functions are shown in Table 1 as follows:

[0082]

[0083]

[0084] Table 1 Settings of accumulator type and functions

[0085] In this embodiment, in step S5, path search is performed through the graph node parallel computing strategy, and the level of the node is updated;

[0086] Specifically, to solve problems such as the coupling and sparsity of graph data and the frequent data partitioning and recombination, large communication overhead, and limited computing parallelism caused by frequent iterations of graph computing, in this process, the graph node parallel computing method is used to search for paths and update the level of the node.

[0087] Specifically, first, all system nodes are defined as two states: active and inactive. Under the initial conditions, only the node at the start of the calculation is set to the active state, while other nodes are in the inactive state. When a node receives information sent by its adjacent edge, it becomes the active state; while a node that does not receive an update message does not need to perform a recalculation operation and remains in the inactive state. When all nodes in the graph are in the inactive state (excluding the initial moment), or when there is no information transfer, the graph computing operation ends.

[0088] Then, take the power supply node as the initial node, and starting from this node, traverse all accumulators that are connected to the initial node and have an inactive state. A node that meets the conditions can be considered an adjacent edge node of the power supply node. Record the number of this node, record its information in the path, and update the node layer. After traversing all nodes connected to the initial node, change the state of the traversed nodes to active, marking that the current node has been visited to avoid repeated traversal.

[0089] Finally, take each adjacent edge node of the initial node as the initial node for the next query, and search and traverse again in the same way. Repeat the traversal search until all accumulators of all nodes in the graph model are in an active state, and then end the traversal.

[0090] In this embodiment, as Figure 2 shown, a simple topological model is used for demonstration:

[0091] In this model, node 1 is the power supply node, that is, the initial node. Before the first iteration, only the state of node 1 is set to the active state, while the states of other nodes are inactive.

[0092] During the first iteration, by finding nodes adjacent to it and having an inactive state, nodes 2 and 3 can be queried. Record nodes 2 and 3 in the node path and set their states to active.

[0093] In the next iteration, nodes 2 and 3 respectively perform the same search, and the corresponding adjacent nodes can be queried. When the entire graph is traversed in this way, three paths [1-2-4-6], [1-3-5-7], and [1-3-5-8] can be obtained.

[0094] Before performing the backward and forward derivation of the graph trace analysis, by recording the node layer and path, it can effectively avoid calculation result errors caused by the delay of calculation information.

[0095] In this embodiment, in step S6, power flow calculation is performed through the graph trace analysis method and the convergence accuracy is judged. When the iteration result meets the set convergence accuracy, end the calculation and output the calculation result.

[0096] Specifically, the steps of performing power flow calculation through the graph trace analysis method and judging the convergence accuracy are as follows:

[0097] S61. Decompose the power transmission and distribution network graph model into a radial network combination in the form of a distribution network;

[0098] S62. Through forward tracing with a topological iterator, perform iterative calculation on the injected current of the load node to obtain the iterative current at the beginning of each branch.

[0099] Among them, the current calculation formula is:

[0100]

[0101] In the formula, i in is the current injected into all nodes; i out is the current flowing out of all nodes; n is the index of the nodes flowing in, used to traverse all the currents i injected into the node in ; k is the index of the nodes flowing out, used to traverse all the currents i flowing out of the node out ;

[0102] S63. By backward tracing through the topological iterator, iteratively calculate the voltage drop generated during the power flow transmission process to obtain the iterative voltage value of each node;

[0103] Among them, the calculation formula for the node voltage is:

[0104] V i -V j =i ij *(R + jX)

[0105] In the formula, V i , V j are the voltages at both ends of the branch; i ij is the current of this branch; R and X are the resistance and reactance of this branch respectively; i is the current node number; j is the next node number.

[0106] S64. Calculate the voltage change amplitude of each node according to the iterative voltage value of each node;

[0107] S65. Judge whether the voltage change amplitude meets the set convergence accuracy. If the voltage change amplitude meets the set convergence accuracy, end the calculation and output the calculation result; if the voltage change amplitude does not meet the set convergence accuracy, continue the iterative calculation.

[0108] In this embodiment, the process of power flow calculation by the graph tracing method is as Figure 3 shown

[0109] First, disconnect from the key node (such as the load node) to disassemble the loop network into a combination of radial networks. Each disconnected node will generate a virtual node at the same time, which belong to different radial networks respectively. The branches in each radial network are called the tree in the system, and the branches connecting both ends of the disconnected node are called the cotree.

[0110] Next, forward-backward substitution calculations can be carried out separately in different radial networks. Before performing the forward-backward substitution calculation, initial value conditions need to be given first. Assume that all node voltages are the standard voltage V base, where the generator voltage is a known constant value and the initial value of the cotree current is 0.

[0111] Among them, when the current is pushed forward, calculate the current of the branch connected to the load:

[0112] S = P + jQ = U * I *

[0113] In the formula, P is the active power; Q is the reactive power; U is the load voltage; I * is the branch current.

[0114] According to KCL, the node injection current is equal to the node outflow current.

[0115]

[0116] In the formula, i in is all the currents injected into this node; i out is all the currents flowing out of this node; n is the index of the currents flowing into the node, used to traverse all the currents i injected into this node in ; k is the index of the currents flowing out of the node, used to traverse all the currents i flowing out of this node out ;

[0117] Calculate the currents of each branch during the current forward-pushing process according to this formula. The forward-pushing process ends at the branch connected to the generator node to obtain the currents of each branch.

[0118] When the voltage is back-substituted, recursively calculate the voltage of the next node according to the following formula:

[0119] V i - V j = i ij * (R + jX)

[0120] In the formula, V i and V j are the voltages at both ends of the branch; i ij is the current of this branch; R and X are the resistance and reactance of this branch respectively; i is the current node number; j is the next node number. During the back-substitution process, calculate until the load position to obtain the voltages of each node. Among them, except for the generator node voltage remaining unchanged, the voltages of other nodes will be updated.

[0121] After completing the forward-pushing and back-substitution process, it is necessary to update the reactive power of the PV node.

[0122] P G = |V G ||I G |cosθ (1) → θ (1)

[0123] Q G(1) = |VG ||I G |sinθ (1)

[0124] Wherein, P G is the active power of the PV node, and this value is known and does not change during the whole calculation; Q G(1) is the reactive power after the update of the PV node, and the change of its value will also change the phase angle value of the PV node voltage; V G and I G represent the current value flowing through the PV node at this time and its unchanged voltage amplitude after a forward-backward substitution calculation; θ (1) represents the new phase angle value of the node voltage after this update.

[0125] After the forward-backward substitution process, the cotree current I cotree needs to be updated:

[0126]

[0127] Wherein, is the change amount of the cotree current after each iteration, which is used to update the cotree current participating in the next calculation; is the cotree current of the previous iteration; is the cotree current of the next iteration; ∑Z is the impedance sum of the voltage difference between the two ends of the cotree and the loop between the trees. is the voltage value at one end of the cotree;

[0128] is the voltage value at the other end of the cotree.

[0129] In this embodiment, combined with the example of Figure 2 , the specific steps to complete the graph calculation using the graph trace analysis method are as follows:

[0130] T1. According to the attributes of the nodes and edges of the established radial network model, find the nodes with only one adjacent edge and not being the balanced node (such nodes generally exist at the end of the radial network), and select this node as the starting node for forward-tracing current calculation.

[0131] T2. The process of node query, data transfer and node update can continue to use the method of updating the node active state in sequence. However, due to the directionality of forward-tracing current calculation and backward-tracing voltage calculation, in order to ensure the accuracy of data transfer, two active state judgment accumulators @active1 and @active2 are set for each node.

[0132] T3. In the initial state, the active state judgment accumulators @active1 of all nodes in the model,

[0133] Both @active2 are set to the inactive state, and then the accumulator @active1 of the starting node is set to active, that is Figure 2 Nodes 6, 7, and 8 in Figure 2 . Starting from the starting node, the data information imported in step 2 is assigned to the accumulator of this node, and node - to - node communication is carried out through the node accumulator.

[0134] T4. Traverse all nodes that simultaneously meet the following three conditions: ① connected to the starting node, ② the node layer (distance from the power supply node 1 path) is less than that of the starting node, and ③ the accumulator @active2 is false, that is, nodes 4 and 5, and regard them as the upper - level nodes.

[0135] T5. Set the accumulator @active1 of all the upper - level nodes traversed in T4 to be the same as the accumulator @active2 of the starting node, that is, the inactive state; set the accumulator @active2 to be the same as the accumulator @active1 of the starting node, that is, the active state.

[0136] T6. According to the data information of the starting node and its adjacent edges, use formula (1) in graph trace analysis to calculate the current transfer on the line between the starting node and the upper - level nodes.

[0137] T7. Set the accumulator @active1 of the upper - level nodes after the calculation is completed to be the same as the accumulator @active2 of this node, that is, the active state; set the accumulator @active2 to the inactive state. At this time, the accumulators @active1 and @active2 of the upper - level nodes after the calculation are active and inactive respectively, which is consistent with the active state of the starting node.

[0138] T8. After the update, nodes 4 and 5 will be used as the starting nodes for the next iteration. In this way, the node traversal, data transfer, and node update for forward - tracking current calculation are repeatedly completed until the accumulator @active1 of all nodes in the graph model is in the active state and @active2 is in the inactive state, indicating that a forward - tracking current calculation process has been completed.

[0139] T9. When a forward - tracking current calculation process is completed, backward - tracking voltage calculation needs to be carried out. To distinguish the accumulators for forward - tracking current calculation, an accumulator @visited for judging whether a node has been visited can be set in this process. Since it is traced from the power supply node to the end nodes of the radial network, the accumulator @visited of the power supply node 1 is set to the active state as the starting node, and the @visited of other nodes are all set to the inactive state.

[0140] T10. Traverse all the nodes connected to the starting node and with the accumulator @visited being inactive, i.e., nodes 2 and 3, and regard them as the next-level nodes. Calculate the voltage drop ΔUij between the starting node and the next-level nodes using the formula for node voltage in graph trace analysis, and then flow the voltage drop information into the next-level nodes.

[0141] T11. After the calculation is completed, set the accumulators @visited of nodes 2 and 3 to the active state and use them as the new starting nodes.

[0142] T12. Repeat the above process to complete the node traversal, data transfer, and node update for backward tracing voltage calculation until the accumulators @visited of all nodes in the graph model are in the active state, indicating that a backward tracing voltage calculation process has been completed.

[0143] T13. Repeatedly complete the forward tracing current and backward tracing voltage calculations using graph trace analysis, obtain the changes in the voltage amplitudes of each node, and determine whether the convergence accuracy is met. When the voltage difference of the node itself is less than the set accuracy value, it is determined that the node voltage calculation of this node has converged, and this node no longer participates in the forward-backward substitution calculation process until the voltage differences of all nodes are less than the set maximum iterative convergence accuracy, then end the calculation and output the calculation results.

[0144] To prove the effect of the method combining the above-mentioned graph trace analysis and graph parallel computing on improving the calculation speed and efficiency, the present invention tested the IEEE69-node distribution network system, and the test results are as Figure 4 shown. Among them, the comparison of the calculation speeds of the present invention, the Newton-Raphson method in Matpower, and the forward-backward substitution method in Python is shown in Table 2:

[0145]

[0146]

[0147] Table 2 Comparison of calculation speeds

[0148] The results prove that the method combining graph trace analysis and graph parallel computing improves the calculation efficiency by more than 90% compared with the traditional Newton-Raphson method, and improves the calculation efficiency by more than 50% compared with the forward-backward substitution method on the traditional computing platform (Python), and can further demonstrate the potential of this method for solving transmission and distribution networks.

[0149] In this embodiment, the traditional Newton-Raphson method is as Figure 5As shown, the Newton-Raphson (NR) method is an iterative method for solving non-linear equations and is widely used in power flow calculations of power systems. Existing technologies such as the master-slave splitting method and the improved algorithm of the Newton-Raphson method are all based on the following algorithm theory. Due to the repeated matrix establishment and decomposition when applied to large systems, it is always difficult to ensure the calculation efficiency and accuracy.

[0150] The present invention combines a graph database with graph trace analysis and calculation, and solves, in a parallel calculation manner, the problem that the power flow calculation of a node in a node layer in the traditional power flow calculation method needs to wait for the power flow calculation of the previous node to end before it can be carried out, thereby being able to greatly shorten the time required for power flow calculation of the power system. The present invention avoids large-scale matrix calculations and effectively solves problems such as serious ill-conditioning of the Jacobian matrix and poor convergence performance in the traditional integrated calculation of transmission and distribution networks. In the calculation of each radial network, due to the use of this graph parallel technology, the convergence speed of the power flow calculation of each "tree" can also be increased by about 80% in terms of efficiency.

[0151] In summary, according to the basic form representing a graph in the graph database, the present invention constructs a power transmission and distribution network graph model corresponding to the topological relationship of the power transmission and distribution network, with generators and loads in the power transmission and distribution network as nodes and power lines as edges; according to the collected parameter data of the power transmission and distribution network, attributes are added to the nodes and edges in the power transmission and distribution network graph model; the data information of the nodes and branches in the power transmission and distribution network is imported into the power transmission and distribution network graph model; a global accumulator and a node accumulator are set, and the global accumulator and the node accumulator are assigned values; path search is performed through a graph node parallel computing strategy, and the layer number where the node is located is updated; power flow calculation is performed through the graph trace analysis method and convergence accuracy judgment is carried out. When the iteration result meets the set convergence accuracy, the calculation is ended and the calculation result is output. By combining the graph database with the graph trace analysis calculation, the present invention solves, in a parallel computing manner, the problem that the power flow calculation of a node in a node layer in the traditional power flow calculation method needs to wait for the power flow calculation of the previous node to end before it can be carried out, thereby greatly shortening the time required for power system power flow calculation. The present invention avoids large-scale matrix calculations and effectively solves problems such as serious ill-conditioning of the Newton method Jacobian matrix and poor convergence performance in traditional integrated power transmission and distribution network calculations. In the calculation of each radial network, due to the use of this graph parallel technology, the convergence speed of the power flow calculation of each "tree" can also be increased by about 80%. The present invention proposes a method for integrated power transmission and distribution network power flow calculation combining graph calculation and graph trace analysis. The power system data is input into the graph database analysis platform, and the power transmission and distribution network is modeled. Then, using the graph trace analysis method, a topological iterator is used to move between components in the model and perform calculations to solve the system power flow. The present invention can implement large-scale power transmission and distribution network power flow calculation through parallel computing. The proposed algorithm not only solves the problem of difficult accurate power flow calculation in the power transmission and distribution network, but also avoids large-scale matrix calculations and improves the calculation speed.

[0152] It should be noted that the method of the embodiments of the present disclosure can be executed by a single device, such as a computer or a server. The method of this embodiment can also be applied to a distributed scenario and completed by the cooperation of multiple devices. In this case of a distributed scenario, one of the multiple devices can only execute one or more steps of the method of the embodiments of the present disclosure, and these multiple devices will interact with each other to complete the described method.

[0153] It should be noted that some embodiments of the present disclosure have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims may be performed in a different order than in the above embodiments and still achieve the desired results. Additionally, the processes depicted in the drawings do not necessarily require the particular order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0154] Embodiment 2

[0155] Refer to Figure 6 , Embodiment 2 of the present invention further provides a power flow analysis device for a transmission and distribution network based on graph computing and graph trace analysis, including:

[0156] A transmission and distribution network graph model construction module 001, configured to construct a transmission and distribution network graph model corresponding to the topological relationship of the transmission and distribution network by using the basic form representing the graph in the graph database, with generators and loads in the transmission and distribution network as nodes and power lines as edges;

[0157] A node and edge attribute adding module 002, configured to add attributes to the nodes and edges in the transmission and distribution network graph model according to the collected parameter data of the transmission and distribution network;

[0158] A node and branch data information importing module 003, configured to import the data information of nodes and branches in the transmission and distribution network into the transmission and distribution network graph model;

[0159] A global accumulator and node accumulator setting module 004, configured to set a global accumulator and a node accumulator, and assign values to the global accumulator and the node accumulator;

[0160] A path search and node layer number updating module 005, configured to perform path search through a graph node parallel computing strategy and update the layer number where the node is located;

[0161] A graph trace analysis method calculation module 006, configured to perform power flow calculation through the graph trace analysis method and judge the convergence accuracy. When the iteration result meets the set convergence accuracy, end the calculation and output the calculation result.

[0162] In this embodiment, in the node and edge attribute adding module 002, during the process of adding attributes to the nodes and edges in the transmission and distribution network graph model, the node attributes include: node number, real part of voltage, imaginary part of voltage, active power, reactive power, and label; the label includes: balanced node, PV node, and PQ node; the edge attributes include: node numbers connected to the edge, resistance, reactance, and edge length.

[0163] In this embodiment, in the global accumulator and node accumulator setting module 004, the functions of the global accumulator include: recording the set of edges, saving voltage values, and saving the number of iterations; the functions of the node accumulator include: storing node voltages and node power information, recording node levels and node voltage changes, and recording node active states.

[0164] In this embodiment, in the trace analysis method calculation module 006, the power flow calculation sub-module includes:

[0165] A model decomposition sub-module 061, configured to decompose the transmission and distribution network diagram model into a radial network combination in the form of a distribution network;

[0166] A branch current iterative calculation sub-module 062, configured to perform iterative calculation on the injected current of a load node by forward tracing through a topology iterator to obtain the iterative current at the start end of each branch;

[0167] A node voltage iterative calculation sub-module 063, configured to perform iterative calculation on the voltage drop generated during the transmission of the power flow by backward tracing through a topology iterator to obtain the iterative voltage value of each node;

[0168] A voltage change amplitude calculation sub-module 064, configured to calculate the voltage change amplitude of each node according to the iterative voltage value of each node;

[0169] A convergence accuracy judgment and processing sub-module 065, configured to judge whether the voltage change amplitude meets the set convergence accuracy. If the voltage change amplitude meets the set convergence accuracy, the calculation is ended and the calculation result is output; if the voltage change amplitude does not meet the set convergence accuracy, iterative calculation is continued.

[0170] In this embodiment, in the branch current iterative calculation sub-module 062 of the trace analysis method calculation module 006, during the process of performing iterative calculation on the injected current of a load node by forward tracing through a topology iterator to obtain the iterative current at the start end of each branch, the current calculation formula is:

[0171]

[0172] where i in is all the currents injected into this node; i out is all the currents flowing out of this node; n is the index of the nodes flowing in, used to traverse all the currents i in injected into this node; k is the index of the nodes flowing out, used to traverse all the currents i out flowing out of this node;

[0173] In the node voltage iterative calculation sub-module 063 of the graph trace analysis calculation module 006, during the process of iteratively calculating the voltage drop generated during the power flow transmission by backward tracing through the topology iterator to obtain the iterative voltage value of each node, the calculation formula for the node voltage is:

[0174] V i -V j =i ij *(R + jX)

[0175] In the formula, V i and V j are the voltages at both ends of the branch; i ij is the current of this branch; R and X are the resistance and reactance of this branch respectively; i is the current node number; j is the next node number.

[0176] It should be noted that the information interaction, execution process, etc. between the above-mentioned system modules, due to being based on the same concept as the method embodiment in Embodiment 1 of the present application, have the same technical effects as the method embodiment of the present application. For specific content, reference can be made to the description in the method embodiment shown above in the present application, and details will not be repeated here.

[0177] Embodiment 3

[0178] Embodiment 3 of the present invention provides a non-transitory computer-readable storage medium, in which program codes for the power flow analysis method of the power transmission and distribution network based on graph calculation and graph trace analysis are stored, and the program codes include instructions for executing the power flow analysis method of the power transmission and distribution network based on graph calculation and graph trace analysis in Embodiment 1 or any possible implementation manner thereof.

[0179] The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or a data center integrating one or more available media. The available medium can be a magnetic medium (for example, a floppy disk, a hard disk, a magnetic tape), an optical medium (for example, a DVD), or a semiconductor medium (for example, a solid-state drive (SolidState Disk, SSD)), etc.

[0180] Embodiment 4

[0181] Embodiment 4 of the present invention provides an electronic device, including: a memory and a processor;

[0182] The processor and the memory communicate with each other through a bus; the memory stores program instructions executable by the processor, and the processor can execute the power flow analysis method of the power transmission and distribution network based on graph calculation and graph trace analysis in Embodiment 1 or any possible implementation manner thereof by calling the program instructions.

[0183] Specifically, the processor can be implemented by hardware or software. When implemented by hardware, the processor can be a logic circuit, an integrated circuit, etc.; when implemented by software, the processor can be a general-purpose processor that realizes its functions by reading software code stored in a memory. The memory can be integrated in the processor or exist independently outside the processor.

[0184] In the above embodiments, they can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present invention are generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable systems. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wirelessly (such as infrared, wireless, microwave, etc.).

[0185] Obviously, those skilled in the art should understand that the above-mentioned modules or steps of the present invention can be implemented by a general computing system. They can be concentrated on a single computing system or distributed on a network composed of multiple computing systems. Optionally, they can be implemented by program code executable by the computing system. Thus, they can be stored in a storage system and executed by the computing system. And in some cases, the steps shown or described can be executed in a sequence different from here, or they can be made into individual integrated circuit modules respectively, or multiple modules or steps among them can be made into a single integrated circuit module for implementation. In this way, the present invention is not limited to any specific combination of hardware and software.

[0186] Although the present invention has been described in detail above with general descriptions and specific embodiments, based on the present invention, some modifications or improvements can be made, which are obvious to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A power flow analysis method for a transmission and distribution network based on graph calculation and graph trace analysis, characterized in that: include: According to the basic form of graph representation in the graph database, the generators and loads in the power transmission and distribution network are taken as nodes, and the power lines are taken as edges to construct a power transmission and distribution network graph model corresponding to the topological relationship of the power transmission and distribution network; According to the collected parameter data of the power transmission and distribution network, adding attributes to the nodes and edges in the power transmission and distribution network graph model; Importing data information of nodes and branches in the power transmission and distribution network into the power transmission and distribution network graph model; Setting a global accumulator and a node accumulator, and assigning values ​​to the global accumulator and the node accumulator; Perform path search through graph node parallel computing strategy and update the number of layers where the nodes are located; The flow calculation is performed through the trace analysis method and the convergence accuracy is judged. When the iterative result meets the set convergence accuracy, the calculation is terminated and the calculation result is output.

2. The method for power flow analysis of a transmission and distribution network based on graph calculation and graph trace analysis according to claim 1 is characterized in that: In the process of adding attributes to the nodes and edges in the power transmission and distribution network graph model, the node attributes include: node number, real part of voltage, imaginary part of voltage, active power, reactive power and label; the labels include: balancing node, PV node and PQ node; the attributes of the edge include: node number connected to the edge, resistance, reactance and length of the edge.

3. The method for power flow analysis of a transmission and distribution network based on graph calculation and graph trace analysis according to claim 2 is characterized in that: The functions of the global accumulator include: recording the set of edges, saving voltage values ​​and saving the number of iterations; the functions of the node accumulator include: storing node voltage and node power information, recording the number of node layers and node voltage changes, and recording the node active status.

4. The method for power flow analysis of a transmission and distribution network based on graph calculation and graph trace analysis according to claim 3 is characterized in that: The steps of calculating power flow and judging convergence accuracy by the trace analysis method are as follows: Decomposing the power transmission and distribution network graph model into a radial network combination in the form of a distribution network; Through the forward tracking of the topology iterator, the injected current of the load node is iteratively calculated to obtain the iterative current at the beginning of each branch; Through the topology iterator, the voltage drop generated by the power flow during the transmission process is iteratively calculated to obtain the iterative voltage value of each node; According to the iterative voltage value of each node, the voltage change amplitude of each node is calculated; It is judged whether the voltage change amplitude satisfies the set convergence precision. If the voltage change amplitude satisfies the set convergence precision, the calculation is terminated and the calculation result is output; if the voltage change amplitude does not satisfy the set convergence precision, the iterative calculation is continued.

5. The method for power flow analysis of a transmission and distribution network based on graph calculation and graph trace analysis according to claim 4 is characterized in that: In the process of tracing forward through the topology iterator, iteratively calculating the injected current of the load node and obtaining the iterative current at the beginning of each branch, the current calculation formula is: In the formula, i in For all currents injected into this node; i out is all the currents flowing out of the node; n is the index of the node flowing into, which is used to traverse all the currents i injected into the node. in ; k is the index of the outflow node, which is used to traverse all currents i flowing out of the node out ; In the process of tracing back through the topology iterator, the voltage drop generated by the power flow during the transmission process is iteratively calculated to obtain the iterative voltage value of each node. The calculation formula of the node voltage is: V i -V j =i ij *(R+jX) Where V i 、V j is the voltage across the branch; i ij is the branch current; R and X are the branch resistance and reactance respectively; i is the current node number; j is the next node number.

6. A power flow analysis device for a distribution network based on graph calculation and graph trace analysis, adopting a power flow analysis method for a distribution network based on graph calculation and graph trace analysis as claimed in any one of claims 1 to 5, characterized in that: include: A power transmission and distribution network graph model construction module is used to construct a power transmission and distribution network graph model corresponding to the topological relationship of the power transmission and distribution network based on the basic form of representing the graph in the graph database, with the generators and loads in the power transmission and distribution network as nodes and the power lines as edges; A node and edge attribute adding module, used for adding attributes to nodes and edges in the power transmission and distribution network graph model according to the collected parameter data of the power transmission and distribution network; A node and branch data information import module, used to import the data information of nodes and branches in the power transmission and distribution network into the power transmission and distribution network graph model; A global accumulator and node accumulator setting module, used to set the global accumulator and the node accumulator, and assign values ​​to the global accumulator and the node accumulator; The path search and node layer number update module is used to perform path search through the graph node parallel computing strategy and update the node layer number; The trace analysis method calculation module is used to perform power flow calculation and convergence accuracy judgment through the trace analysis method. When the iteration result meets the set convergence accuracy, the calculation is terminated and the calculation result is output.

7. The transmission and distribution network power flow analysis device based on graph calculation and graph trace analysis according to claim 6, characterized in that: In the node and edge attribute adding module, in the process of adding attributes to the nodes and edges in the power transmission and distribution network graph model, the node attributes include: node number, real part of voltage, imaginary part of voltage, active power, reactive power and label; the labels include: balancing node, PV node and PQ node; the edge attributes include: node number connected to the edge, resistance, reactance and length of the edge.

8. The transmission and distribution network power flow analysis device based on graph calculation and graph trace analysis according to claim 7 is characterized in that: In the global accumulator and node accumulator setting module, the functions of the global accumulator include: recording the set of edges, saving voltage values ​​and saving the number of iterations; the functions of the node accumulator include: storing node voltage and node power information, recording the number of node layers and node voltage changes, and recording the node activity status.

9. The transmission and distribution network power flow analysis device based on graph calculation and graph trace analysis according to claim 8, characterized in that: In the trace analysis calculation module, the power flow calculation submodule includes: A model decomposition submodule, used for decomposing the power transmission and distribution network graph model into a radial network combination in the form of a distribution network; The branch current iterative calculation submodule is used to iteratively calculate the injected current of the load node by tracing forward through the topology iterator to obtain the iterative current at the beginning of each branch; The node voltage iterative calculation submodule is used to trace back through the topology iterator, iteratively calculate the voltage drop generated during the power flow transmission process, and obtain the iterative voltage value of each node; A voltage variation amplitude calculation submodule is used to calculate the voltage variation amplitude of each node according to the iterative voltage value of each node; The convergence accuracy judgment and processing submodule is used to judge whether the voltage change amplitude meets the set convergence accuracy. If the voltage change amplitude meets the set convergence accuracy, the calculation is terminated and the calculation result is output; if the voltage change amplitude does not meet the set convergence accuracy, the iterative calculation is continued.

10. The transmission and distribution network power flow analysis device based on graph calculation and graph trace analysis according to claim 9, characterized in that: In the branch current iterative calculation submodule of the trace analysis calculation module, in the process of forward tracing through the topology iterator, iteratively calculating the injected current of the load node, and obtaining the iterative current at the beginning of each branch, the current calculation formula is: In the formula, i in For all currents injected into this node; i out is all the currents flowing out of the node; n is the index of the node flowing into, which is used to traverse all the currents i injected into the node. in ; k is the index of the outflow node, which is used to traverse all currents i flowing out of the node out ; In the node voltage iterative calculation submodule of the trace analysis calculation module, in the process of iteratively calculating the voltage drop generated by the power flow during the transmission process by tracing back through the topology iterator, and obtaining the iterative voltage value of each node, the calculation formula of the node voltage is: V i -V j =i ij *(R+jX) Where V i 、V j is the voltage across the branch; i ij is the branch current; R and X are the branch resistance and reactance respectively; i is the current node number; j is the next node number.

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