Low-voltage power distribution network line full-topology identification method and system

Abstract

The invention discloses a low-voltage power distribution network line full-topology identification method and system, and mainly relates to the technical field of low-voltage power distribution network line topology identification. Comprising the following steps: establishing a mathematical model based on a graph theory; an injection method is adopted to determine the incidence relation between the areas, and the configuration of the line topology is realized based on IEC 61850SCL; according to the established mathematical model, carrying out transformer area division on the low-voltage power distribution network; and carrying out topology identification on the line in the unknown area. The method has the advantages that the low-voltage power distribution network line topology structure is recognized, actual low-voltage power distribution network station area user voltage data are selected, and it is further proved that the full-topology recognition method can recognize the line topology in the station area.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage distribution network line topology identification, and in particular to a method and system for identifying the full topology of a low-voltage distribution network line. Background Art

[0002] As the proportion of distributed energy resources (DER) in the distribution network increases, the low-voltage distribution network needs to be effectively monitored. As an important support for low-voltage distribution network monitoring, low-voltage distribution network line topology identification can locate faults and ensure the safety of users' electricity use. Although some scholars currently use orderly power outages and injection methods to identify low-voltage line topology, the following problems still exist:

[0003] 1. There are various wiring methods for low-voltage distribution networks. Using a single wiring method makes it difficult to identify the overall topology of the low-voltage distribution network due to transformer switching, monitoring equipment not installed or missing, unclear ownership or records, etc.;

[0004] 2. The configuration information of low-voltage line topology is the basis for the exchange of advanced application information, but there is no standard to regulate the configuration information of low-voltage line topology. In order to realize the monitoring of medium-voltage distribution network, IEC 61850 standard is applied to medium-voltage distribution network to achieve interconnection and interoperability, and can also realize the identification of medium-voltage line topology. If the low-voltage distribution network also adopts IEC61850 standard, it is conducive to the integration of medium and low voltage data. However, due to the different line structures of low-voltage and medium-voltage distribution networks, the same topology identification method cannot be used;

[0005] 3. The existing low-voltage distribution network line topology identification methods mainly include orderly power outage, injection method, data correlation algorithm based on user power consumption information, etc., but the orderly power outage method can only identify the transformer-line-user information of the substation area, and cannot identify the hierarchical structure of the branch. The injection signal method has a clear principle and good topology identification ability, but it can only identify the connection relationship between regions, and cannot identify the topological structure within the region. At the same time, it cannot identify the regional topology without LTU monitoring. Based on the user's power consumption information (e.g., voltage, power, etc.), a data correlation algorithm (e.g., Pearson correlation coefficient method, Tanimoto similarity, etc.) is used for similarity analysis. The method based on power consumption information does not require additional equipment, but the amount of power consumption information data is large, the algorithm is complex, and low-voltage intelligent terminals may be difficult to implement;

[0006] 4. K-means clustering is widely used in distribution networks to identify transformer-user topology due to its simplicity, fast convergence speed and high efficiency. However, the k-means clustering algorithm is easily affected by the initial cluster center and the number of clusters, resulting in a low recognition rate. Therefore, the use of a single recognition method has not effectively solved the problem of low-voltage topology line recognition;

[0007] 5. Existing low-voltage distribution network line topology identification methods mostly identify the line topology of all lines in the entire substation area. However, there are situations where the topology of some lines in the substation area is known, which easily leads to a waste of computing resources.

[0008] Therefore, there is an urgent need for a method and system for identifying the full topology of low-voltage distribution network lines to solve the above problems. Summary of the invention

[0009] The purpose of the present invention is to provide a method and system for identifying the full topology of a low-voltage distribution network line, so as to realize the identification of the topological structure of the low-voltage distribution network line. Actual low-voltage distribution network lines are selected for experimental analysis, which further proves that the "full topology" identification method can realize the identification of the line topology within the substation.

[0010] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0011] On the one hand, a method for identifying the full topology of a low-voltage distribution network line is provided, comprising the following steps:

[0012] S1: Establish mathematical models based on graph theory;

[0013] S2: The injection method is used to determine the association relationship between regions and the line topology is configured based on IEC 61850SCL;

[0014] S3: Divide the low voltage distribution network into substation areas according to the established mathematical model;

[0015] S4: Perform topological identification on the lines in the unknown area.

[0016] Preferably, the step S1 is specifically as follows: abstracting the low-voltage distribution network line into a set of low-voltage distribution network edges and nodes, reflecting the association relationship between topological blocks through the connection relationship between nodes and edges, and between nodes in the graph, modeling the low-voltage distribution network line topology as a triplet G=(V, E, S) based on graph theory, and the set of nodes, edges, and switches of the low-voltage distribution network line are respectively represented as V(G)={V1, V2, ...V n}, E(G) = {e1, e2, ...e n}、S k ∈[0, 1];

[0017] By converting the physical model of nodes, edges, and switch states into the mathematical model of transformers, edges, and switches.

[0018] Preferably, in step S2, specifically:

[0019] The method of injecting characteristic current is used to identify the correlation between regions:

[0020] The injection method injects a high-frequency signal at the power point and inserts an inductor in series to prevent the high-frequency signal from propagating upward. The path of the downstream line is determined by detecting the high-frequency signal. At the same time, a disturbance signal is injected at the load, and the load topology relationship is determined by judging the size of the disturbance current.

[0021] The partial line topology in the distribution cabinet of the substation is known, and the known line topology can be configured based on IEC 61850SCL. The monitoring area of ​​the entire LTU is modeled as a substation. The substation name is unique during modeling. An area is taken as an interval, and its corresponding description line and substation are described through the description field. During modeling, they are configured in sequence according to the hierarchical structure of Substation-Voltage-Bay-ConductingEquipment.

[0022] Preferably, in step S3, the low voltage distribution network is divided into substation areas, specifically:

[0023] The low voltage line topology is modeled as an undirected graph G based on the first section, with the transformer node as the root node, the terminal load or DER as the leaf node, and the node where the line intersects as the branch node;

[0024] If the area is set to be monitored by n LTUs, the low-voltage line is divided into n small areas according to the monitoring range of the LTUs, and the undirected graph G is divided into n subgraphs;

[0025] Based on the configuration of known routes and the determination of the association relationship between regions in step S2, and in combination with the user collected information, the known regions and unknown regions are determined.

[0026] Preferably, the unknown area includes:

[0027] The root node area is unknown. It is known that the gateway meter layer of the substation contains two meters, and the identified line topology information only contains one substation transformer. Therefore, this area is judged to be an unknown area.

[0028] The branch node area is unknown. When the injection method is used to identify the inter-region line association relationship, this part of the area is judged as the branch node area unknown;

[0029] The leaf node area is unknown. LTU missing or not installed, and dynamic changes in phase line relationships can all cause the leaf node area to be unknown.

[0030] Multiple regions are unknown, including the root node region and the branch node region are unknown at the same time, or the root node region and the leaf node region are unknown at the same time, or the branch node region and the leaf node region are unknown at the same time;

[0031] The entire area is completely unknown. If the entire substation area does not contain LTU, or the TTU, distribution board and LTU do not store any line topology configuration information related to the substation area, but according to the data information of the metering automation system, the area contains a large number of electricity users, then this area is judged to be completely unknown.

[0032] Preferably, in step S4, topology identification is performed on the lines in the unknown area, specifically:

[0033] Select the user voltage data of the actual low-voltage distribution area, set the unknown area, and determine the actual topological line of the distribution area. When individual sampling points of users fail, use the value at time t-1 to fill in the voltage data. The voltage data of a certain period of time is statistically analyzed by k-means clustering to determine the topological relationship.

[0034] On the other hand, a recognition system based on the above-mentioned low-voltage distribution network line full topology recognition method is provided, comprising:

[0035] Model building module, used to: build mathematical models based on graph theory;

[0036] The model processing and analysis module is used to: configure known lines according to the established mathematical model and determine the correlation between regions; divide the low-voltage distribution network into substation areas;

[0037] The model output module is used to: perform topological identification on the lines in the unknown area.

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. The medium voltage distribution network widely uses the IEC 61850 standard to realize the monitoring of medium voltage, and the low voltage distribution network adopts the IEC 61850 standard, which is conducive to the information integration and sharing of medium and low voltage distribution networks, and is more conducive to the monitoring of low voltage distribution networks;

[0040] 2. Based on the known area line topology information configured in IEC 61850SCL, the injection method is used to determine the correlation between regions. The low-voltage distribution network line topology is divided into two categories: known areas and unknown areas through regional division. Only the line relationship in the unknown area is identified, which greatly reduces the amount of data to be identified. At the same time, the branch nodes with closer electrical distance are used as clustering centers, and phase line clustering is performed to improve the accuracy of similarity judgment;

[0041] 3. The full topology identification strategy proposed in the present invention adopts different topology identification strategies in a targeted manner according to the specific conditions of the line topology of the substation, thereby improving the accuracy of line topology identification, facilitating the use of other advanced applications of the distribution network, and having important significance for improving the monitoring of the low-voltage distribution network and ensuring the safety of users' electricity use. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of the method of the present invention;

[0043] Figure 2 It is a simplified model of the low voltage distribution network topology of the present invention;

[0044] Figure 3 It is a topology identification flow chart based on IEC 61850SCL of the present invention;

[0045] Figure 4 It is a topological region segmentation sub-model diagram of the present invention;

[0046] Figure 5 It is a voltage variation curve of users in the missing area after clustering of the substation area of ​​the present invention;

[0047] Figure 6 It is a schematic diagram of the system structure of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the application equally.

[0049] In the present invention, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present invention, and do not specifically refer to any part or element in the present invention and should not be understood as limitations on the present invention.

[0050] In the present invention, terms such as "fixed connection", "connected", "connection", etc. should be understood in a broad sense, indicating that it can be fixedly connected, integrally connected or detachably connected; it can be directly connected or indirectly connected through an intermediate medium. Relevant scientific research or technical personnel in this field can determine the specific meanings of the above terms in the present invention according to specific circumstances, and they should not be understood as limiting the present invention.

[0051] Example:

[0052] like Figure 1 As shown, this embodiment provides a method for identifying the full topology of a low-voltage distribution network line, comprising the following steps:

[0053] S1: Establish mathematical models based on graph theory;

[0054] S2: The injection method is used to determine the association relationship between regions and the line topology is configured based on IEC 61850SCL;

[0055] S3: Divide the low voltage distribution network into substation areas according to the established mathematical model;

[0056] S4: Perform topological identification on the lines in the unknown area.

[0057] Among them, step S1 is specifically: abstracting the low-voltage distribution network line into a set of low-voltage distribution network edges and nodes, reflecting the association relationship between topological blocks through the connection relationship between nodes and edges, and between nodes in the graph, and modeling the low-voltage distribution network line topology as a triplet G=(V, E, S) based on graph theory, and the set of nodes, edges, and switches of the low-voltage distribution network line are respectively expressed as V(G)={V1, V2, ... V n}, E(G) = {e1, e2, ...e n}、S k ∈[0,1](S k =0 means the switch is off, S k =1 means switch on and off);

[0058] The line topology of low-voltage distribution network mainly includes static topology and dynamic topology. Static topology represents the connection relationship between electrical components. Dynamic topology includes the state change of switches on the basis of static topology. The physical model of node, edge, switch state and phase line change is converted into a mathematical model describing transformer, edge and switch, so as to realize the analysis of low-voltage line topology. Figure 2 shown.

[0059] Step S2 is specifically:

[0060] The method of injecting characteristic current can be used to identify the correlation between regions. The injection method injects high-frequency signals at the power point and inserts inductors in series to prevent the high-frequency signals from propagating upward. The path of the downstream line is determined by detecting the high-frequency signals. At the same time, a disturbance signal is injected at the load. The load topology relationship is determined by judging the size of the disturbance current. Based on this, it can only be determined whether the topology between regions is on the same line. The search algorithm can be used to identify the upstream and downstream connection relationship between different regions in the substation, but the topological information within the region cannot be identified.

[0061] The internal line topology of the distribution cabinet in the substation area is known, and the configuration of the known line topology can be realized based on IEC 61850SCL. The monitoring area of ​​the entire LTU is modeled as a substation. The substation name should be unique during modeling. An area is regarded as an interval (Bay), and its corresponding description lines, substations, etc. are described through the description field. When modeling, it is configured in sequence according to the hierarchical structure of Substation-Voltage-Bay-ConductingEquipment. Because the area is modeled as a Bay, the switches, lines, and connection nodes in the area should be unique in the area. Figure 3 Taking the A branch box as an example, the configuration based on IEC 61850SCL will generate an S1.cid file to facilitate the identification of the topology within the area.

[0062] Step S3 is specifically:

[0063] The low-voltage line topology is modeled as an undirected graph G based on the first section, with transformer nodes as root nodes (such as V1 and V2), terminal loads or DERs as leaf nodes (such as V8 and V11), and line intersection nodes as branch nodes (such as V3 and V4). Assuming that the area is monitored by n LTUs, the low-voltage line is divided into n small areas according to the monitoring range of the LTUs. For graph G, it is divided into n subgraphs, such as Figure 4 As shown in the figure, when the identification area is equipped with LTU, the area can be divided by the field segmentation shown in the figure (the black area in the figure). Due to the limitations of equipment cost, later operation and maintenance cost, human resources, etc., the LTU coverage rate of most low-voltage distribution networks is not 100%. There are cases where LTU is damaged or not installed (the blue area in the figure), so there are unknown areas. Based on the configuration of the known lines in the second section and the determination of the correlation relationship between regions, combined with the user collection information, the known areas and unknown areas are judged. The unknown areas are mainly divided into the following situations:

[0064] 1) The root node area is unknown (the outgoing line section of the transformer in the substation is unknown, such as Figure 4 The area where LTU2 is located is known to contain two meters of information at the gateway meter layer of the substation, and the identified line topology information contains only one substation transformer, so this area is determined to be an unknown area;

[0065] 2) The branch node area is unknown (e.g. Figure 4In the area where LTU3 is located, when the injection method is used to identify the line association relationship between regions, if S3 is disconnected, it can be identified that LTU1, LTU5 and LTU6 can all receive signals. The line topology inside the area can be obtained based on the SCL configuration information of IEC 61850. Combined with the signal identification area association information, it can be seen that there is no line connection between the line topologies of LTU1, LTU5 and LTU6, so it is judged that this part of the area is an unknown branch node area;

[0066] 3) The leaf node area is unknown (e.g. Figure 4 The area where LTU6 is located), the lack or non-installation of LTU, and the dynamic change of phase line relationship can cause the leaf node area to be unknown. Based on the SCL configuration information of IEC 61850, it can be known that the branch node area contains outgoing line information, but no leaf node area contains incoming line information. Therefore, it is judged that the leaf node area downstream of the branch node area is unknown;

[0067] 4) Multiple areas are unknown, including the root node area and the branch node area are unknown at the same time, or the root node area and the leaf node area are unknown at the same time, or the branch node area and the leaf node area are unknown at the same time. For example, LTU3 and LTU6 are unknown at the same time. From the configuration information of LTU1, it can be seen that it contains two outgoing line information, but no branch node area contains the same incoming line information, so it is judged that the branch node area and the leaf node area are all unknown;

[0068] 5) The entire area is completely unknown. If the entire substation area does not contain LTU, or the TTU (distribution transformer supervisory terminal unit, TTU), switchboard and LTU do not store any line topology configuration information related to the substation area, but according to the data information of the metering automation system, the area contains a large number of electricity users, then this area is judged to be completely unknown.

[0069] Step S4 is specifically:

[0070] Select the user voltage data of the actual low-voltage distribution area, set the unknown area, and determine the actual topological line of the distribution area. When individual sampling points of users fail, use the value at time t-1 to fill in the voltage data to complete the voltage data. By analyzing a large number of voltage data samples, the correlation is judged only by the voltage data of a certain day, and the accuracy is low. It is necessary to perform k-means cluster analysis on the voltage data for a period of time to determine the topological relationship. Figure 5 The voltage change curve of users in the unknown area clustered in area A.

[0071] In order to facilitate data observation and verify the accuracy of data clustering, the voltage data numbers of the clustered clusters can be divided and compared with the user numbers of the original lines to determine the accuracy of clustering. After comparison, the clustering accuracy of the A station area is 95.42%. Compared with the traditional k-means clustering, the recognition accuracy is greatly improved because the influence of the initial cluster center and the number of clusters is avoided and the amount of data to be recognized is reduced.

[0072] like Figure 6 As shown, this embodiment also provides an identification system based on the above-mentioned low-voltage distribution network line full topology identification method, including:

[0073] Model building module, used to: build mathematical models based on graph theory;

[0074] The model processing and analysis module is used to: configure known lines according to the established mathematical model and determine the correlation between regions; divide the low-voltage distribution network into substation areas;

[0075] The model output module is used to: perform topological identification on the lines in the unknown area.

[0076] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art may make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A method for identifying the full topology of a low-voltage distribution network line, characterized in that: The following steps are involved: S1: Establish mathematical models based on graph theory; S2: The injection method is used to determine the association relationship between regions and the line topology is configured based on IEC 61850SCL; S3: Divide the low voltage distribution network into substation areas according to the established mathematical model; S4: Perform topological identification on the lines in the unknown area.

2. According to claim 1, a method for identifying the full topology of a low-voltage distribution network line, characterized in that: The step S1 is specifically as follows: abstracting the low-voltage distribution network line into a set of low-voltage distribution network edges and nodes, reflecting the association relationship between topological blocks through the connection relationship between nodes and edges, and between nodes in the graph, modeling the low-voltage distribution network line topology as a triplet G=(V, E, S) based on graph theory, and the set of nodes, edges, and switches of the low-voltage distribution network line are respectively represented as V(G)={V1, V2, ... V n }, E(G) = {e1, e2, ...e n }、S k ∈[0, 1]; By converting the physical model of nodes, edges, and switch states into the mathematical model of transformers, edges, and switches.

3. According to claim 2, a method for identifying the full topology of a low-voltage distribution network line, characterized in that: The step S2 is specifically: The method of injecting characteristic current is used to identify the correlation between regions: The injection method injects a high-frequency signal at the power point and inserts an inductor in series to prevent the high-frequency signal from propagating upward. The path of the downstream line is determined by detecting the high-frequency signal. At the same time, a disturbance signal is injected at the load, and the load topology relationship is determined by judging the size of the disturbance current. The partial line topology in the distribution cabinet of the substation is known, and the known line topology can be configured based on IEC 61850 SCL. The monitoring area of ​​the entire LTU is modeled as a substation. The substation name is unique during modeling. An area is taken as an interval, and its corresponding description line and substation are described through the description field. During modeling, they are configured in sequence according to the hierarchical structure of Substation-Voltage-Bay-ConductingEquipment.

4. According to claim 3, a method for identifying the full topology of a low-voltage distribution network line, characterized in that: In step S3, the low voltage distribution network is divided into substation areas, specifically: The low voltage line topology is modeled as an undirected graph G based on the first section, with the transformer node as the root node, the terminal load or DER as the leaf node, and the node where the line intersects as the branch node; If the area is set to be monitored by n LTUs, the low-voltage line is divided into n small areas according to the monitoring range of the LTUs, and the undirected graph G is divided into n subgraphs; Based on the configuration of known routes and the determination of the association relationship between regions in step S2, and in combination with the user collected information, the known regions and unknown regions are determined.

5. A method for identifying the full topology of a low-voltage distribution network according to claim 4, characterized in that: The unknown areas include: The root node area is unknown. It is known that the gateway meter layer of the substation contains two meters, and the identified line topology information only contains one substation transformer. Therefore, this area is judged to be an unknown area. The branch node area is unknown. When the injection method is used to identify the inter-region line association relationship, this part of the area is judged as the branch node area unknown; The leaf node area is unknown. LTU missing or not installed, and dynamic changes in phase line relationships can all cause the leaf node area to be unknown. Multiple regions are unknown, including the root node region and the branch node region are unknown at the same time, or the root node region and the leaf node region are unknown at the same time, or the branch node region and the leaf node region are unknown at the same time; The entire area is completely unknown. If the entire substation area does not contain LTU, or the TTU, distribution board and LTU do not store any line topology configuration information related to the substation area, but according to the data information of the metering automation system, the area contains a large number of electricity users, then this area is judged to be completely unknown.

6. A method for identifying the full topology of a low-voltage distribution network line according to claim 5, characterized in that: In step S4, topology identification is performed on the lines in the unknown area, specifically: Select the user voltage data of the actual low-voltage distribution area, set the unknown area, and determine the actual topological line of the distribution area. When individual sampling points of users fail, use the value at time t-1 to fill in the voltage data. The voltage data of a certain period of time is statistically analyzed by k-means clustering to determine the topological relationship.

7. An identification system based on the low-voltage distribution network line full topology identification method according to claim 6, characterized in that: include: Model building module, used to: build mathematical models based on graph theory; The model processing and analysis module is used to: configure known lines according to the established mathematical model and determine the correlation between regions; divide the low-voltage distribution network into substation areas; The model output module is used to: perform topological identification on the lines in the unknown area.

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