Method and system for correcting topological relation between transformer and line in power distribution network area

Abstract

The invention discloses a method and system for correcting the topological relation between a distribution network area transformer and a line, and relates to the technical field of distribution network transformer topology correction, and the method comprises the steps: obtaining a to-be-corrected area transformer in a target area, and injecting a target current signal with a preset frequency and amplitude at a preset side of the area transformer; based on a feeder terminal unit, acquiring first current signals of a plurality of section switches of the target area; extracting a high-frequency component amplitude of the first current signal, and obtaining a first signal amplitude of the section switch based on the high-frequency component amplitude; if the first signal amplitude is greater than a preset threshold value, obtaining a target line of the section switch; and correcting the topological graph of the target area based on the target line, thereby solving the problems of high cost caused by the fact that a monitoring device needs to be additionally arranged on a transformer node in a current correction method for the topological relation between the power distribution network line and the transformer area, and complexity and difficulty in compatibility caused by the fact that different threshold values and parameters need to be set in an online algorithm.

Description

Technical Field

[0001] This invention relates to the field of distribution network transformer topology correction technology, specifically to a method and system for correcting the relationship between distribution network transformers and line topology. Background Technology

[0002] With the advancement of my country's new power system construction and the large-scale integration of new equipment such as distributed power sources, energy storage, and smart power terminals, the distribution network structure is becoming increasingly complex, line planning and renovation are frequent, and the actual connection relationship (i.e., topology relationship) between transformer substations and lines often changes. A correct distribution network topology is an important foundation for ensuring the safety analysis and control decisions of the distribution network.

[0003] Currently, the main techniques for correcting the topology relationship between distribution network lines and transformer substations involve installing intelligent devices and using online algorithms to identify the topology based on stored information. However, these techniques have the following drawbacks:

[0004] 1) Not applicable to the current distribution network: The large number of nodes and branches in the distribution network results in a large number of transformer substations. Due to economic reasons, it is not possible to install voltage or current information acquisition devices at every node and every transformer substation. It is not practical to install monitoring equipment at the node of a transformer substation in order to correct the transformer substation.

[0005] 2) Online algorithms are relatively complex: Different algorithm thresholds and discrimination parameters are usually required for different lines, which is complex and difficult to promote on a large scale. Summary of the Invention

[0006] To address the issues of high costs associated with current methods for correcting the topology relationship between distribution network lines and transformer substations, which require the installation of monitoring equipment at transformer nodes, and the complexity and incompatibility of online algorithms requiring different thresholds and parameters, this invention provides a method for correcting the topology relationship between distribution network transformer substations and lines. The method includes:

[0007] Obtain the transformer to be corrected in the target area, and inject a target current signal with a preset frequency and amplitude into a preset side of the transformer.

[0008] Based on the feeder terminal unit, the first current signal of several segmented switches in the target area is acquired;

[0009] Extract the high-frequency component amplitude of the first current signal, and obtain the first signal amplitude of the segmented switch based on the high-frequency component amplitude;

[0010] If the amplitude of the first signal is greater than a preset threshold, then the target line of the segmented switch is obtained;

[0011] The topology map of the target area is corrected based on the target route.

[0012] This method utilizes the characteristic that high-frequency current propagates primarily along lower impedances in distribution networks to direct the injected signal to the low-voltage side of the transformer. The signal amplitude is extracted by feeder terminal units (FTUs) already deployed at the sectionalizing switches. Combined with precise measurements from the FTUs, and based on signal strength comparison and threshold determination, the actual connected line of the transformer is automatically located. This identifies which main line the transformer at the end of the line belongs to, thus correcting the topological relationship between the distribution network line and the transformer. This method requires no large-scale modifications or additional equipment, utilizing the built-in feeder terminal units, resulting in low cost. Furthermore, it uses the same parameters for signal strength comparison and threshold determination, making the algorithm simple, highly compatible, and more suitable for large-scale distribution network lines.

[0013] Furthermore, the preset threshold is obtained as follows:

[0014] The background noise amplitude is obtained based on the first signal amplitude, the mean and standard deviation of the background noise amplitude are obtained, and the preset threshold is obtained based on the mean and the standard deviation.

[0015] To ensure that, in the presence of an injected signal, the probability (i.e., the detection probability) of the detected signal amplitude exceeding a preset threshold is as high as possible.

[0016] Furthermore, the first calculation formula for obtaining the preset threshold is:

[0017] ;

[0018] in, Indicates the preset threshold. This represents the mean value of the background noise amplitude. Represents the empirical coefficient. The standard deviation of the background noise amplitude.

[0019] Furthermore, the method also includes:

[0020] Before the target current signal is injected, the second signal amplitude of the segmented switch is obtained;

[0021] Obtain the probability of misjudgment when the amplitude of the second signal is greater than the preset threshold;

[0022] Determine whether the false positive probability is less than or equal to the maximum probability; otherwise, adjust the frequency and amplitude of the target current signal.

[0023] Based on the Neyman-Pearson decision criterion, a preset threshold is set such that, in the absence of injected signal (only noise), the probability of the detected amplitude exceeding the preset threshold (i.e., the probability of misjudgment) does not exceed the preset maximum probability.

[0024] Furthermore, the second formula for calculating the false positive probability is as follows:

[0025] ;

[0026] in, Indicates the preset threshold. Indicates the probability of misjudgment. Indicates the amplitude of the second signal. This indicates that no target current signal has been injected. Indicates the maximum probability. This indicates the probability that the amplitude of the second signal exceeds a preset threshold when no target current signal is injected.

[0027] Furthermore, the specific steps for adjusting the amplitude of the target current signal include:

[0028] The first current amplitude is obtained based on the first signal amplitude;

[0029] The target current amplitude is obtained based on the first current amplitude, the first signal amplitude, and the minimum signal-to-noise ratio;

[0030] The target current signal is updated based on the target current amplitude.

[0031] If the amplitude of the detected signal is insufficient, the amplitude of the injected current can be increased proportionally to meet the minimum signal-to-noise ratio requirement.

[0032] Furthermore, the third calculation formula for obtaining the amplitude of the first current is:

[0033] ;

[0034] in, Indicates the amplitude of the first signal. This represents the transmission coefficient of the line. This indicates the magnitude of the first current.

[0035] Furthermore, the fourth calculation formula for obtaining the target current amplitude is:

[0036] ;

[0037] ;

[0038] in, Indicates the target current amplitude. Indicates the minimum signal amplitude. This indicates the amplitude of the background noise.

[0039] Furthermore, the specific steps for adjusting the frequency of the target current signal include:

[0040] The spectrum of different frequencies within a preset frequency range is obtained, the minimum background noise is obtained based on the spectrum, and the frequency of the target current signal is updated based on the target frequency corresponding to the minimum background noise.

[0041] The present invention also provides a system for correcting the topology relationship between transformers and lines in a distribution network, the system comprising:

[0042] Injection unit: used to acquire the transformer to be corrected in the target area and inject a target current signal of preset frequency and amplitude into a preset side of the transformer.

[0043] Analysis unit: used to acquire first current signals of several segmented switches in the target area based on the feeder terminal unit; extract the high-frequency component amplitude of the first current signal, and obtain the first signal amplitude of the segmented switch based on the high-frequency component amplitude;

[0044] Correction unit: If the amplitude of the first signal is greater than a preset threshold, it acquires the target line of the segmented switch; and corrects the topology map of the target area based on the target line.

[0045] The principle and effect of this system are similar to those of this method, so no further details will be provided for this system.

[0046] One or more technical solutions provided by this invention have at least the following technical effects or advantages:

[0047] This method utilizes the characteristic that high-frequency current propagates primarily along lower impedances in distribution networks to direct the injected signal to the low-voltage side of the transformer. The signal amplitude is extracted by feeder terminal units (FTUs) already deployed at the sectionalizing switches. Combined with precise measurements from the FTUs, and based on signal strength comparison and threshold determination, the actual connected line of the transformer is automatically located. This identifies which main line the transformer at the end of the line belongs to, thus correcting the topological relationship between the distribution network line and the transformer. This method requires no large-scale modifications or additional equipment, utilizing the built-in feeder terminal units, resulting in low cost. Furthermore, it uses the same parameters for signal strength comparison and threshold determination, making the algorithm simple, highly compatible, and more suitable for large-scale distribution network lines. Attached Figure Description

[0048] The accompanying drawings, which are provided to further illustrate embodiments of the invention and constitute a part of this invention, are not intended to limit the scope of the invention.

[0049] Figure 1 This is a flowchart illustrating a method for correcting the topology relationship between transformers and lines in a distribution network area according to the present invention.

[0050] Figure 2 This is a partial topology diagram of a power distribution network in a certain section of Shaanxi Province. Detailed Implementation

[0051] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, where there is no conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0052] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0053] Example 1

[0054] refer to Figure 1 This embodiment provides a method for correcting the topology relationship between transformers and lines in a distribution network area. The method includes:

[0055] The transformer to be calibrated in the target area is identified, and a target current signal of a preset frequency and amplitude is injected into a preset side of the transformer. For example, taking a 10kV distribution network line, on the low-voltage side of the transformer (e.g., at a 0.4kV outgoing switch or busbar), a portable low-voltage topology characteristic current injector is used to inject a high-frequency characteristic current signal of a specific frequency and amplitude. The frequency of this high-frequency characteristic current signal is preferably 400Hz to 600Hz (e.g., 600Hz is a typical value, corresponding to the 12th harmonic frequency of the power frequency), and the amplitude is preferably 10A to 50A. This frequency range is chosen because it is far from the power frequency (50Hz) and its main low-order harmonics (such as the 3rd, 5th, and 7th harmonics), resulting in lower background electrical noise and making the injected characteristic signal easier to identify and extract.

[0056] Feeder terminal units are deployed at various sectional switches, tie switches, or important branch nodes of 10kV distribution lines. They are usually the standard configuration of distribution automation systems. They have a built-in harmonic analysis module based on digital signal processing (DSP), which can perform algorithms such as discrete Fourier transform algorithm / fast Fourier transform algorithm on the acquired current signal to accurately extract the frequency of the injected signal.

[0057] Based on feeder terminal units (FTUs), the first current signals of several sectionalizing switches in the target area are acquired; the injected high-frequency characteristic current signal utilizes the frequency characteristics of the line impedance. Specifically, branch lines and their terminal loads (such as other transformers, inductive loads, etc.) in the distribution network typically exhibit high impedance characteristics to high-frequency signals, while the main line impedance is relatively low. Therefore, the injected high-frequency characteristic current signal will mainly propagate along the main line to the system power supply side (10kV side), with very little diversion to other branch lines and load sides. At each sectionalizing switch of the 10kV line, the current signal is acquired using widely deployed feeder terminal units (FTUs).

[0058] The high-frequency component amplitude of the first current signal is extracted, and the first signal amplitude of the segmented switch is obtained based on the high-frequency component amplitude. Each feeder terminal unit uses its built-in harmonic analysis module (usually based on the discrete Fourier transform algorithm / fast Fourier transform algorithm) to process the acquired current signal and extract the amplitude of the high-frequency component corresponding to the injected signal frequency (for example, if a 600Hz signal is injected, the 12th harmonic component is extracted) as the characteristic signal strength of the segmented switch.

[0059] If the amplitude of the first signal is greater than a preset threshold, the target line of the segmented switch is obtained. Since the signal mainly propagates along the main line, the signal amplitude detected by the feeder terminal unit on the line correctly connected to the transformer substation will be significantly higher than that of the unconnected line. The line to which the switch with the signal amplitude exceeding the preset threshold belongs is determined as the actual access line of the transformer substation and recorded as a strong signal point, thereby realizing automatic correction of the topology.

[0060] The topology map of the target area is corrected based on the target line. According to pre-stored basic power grid topology information (including the association between each feeder terminal unit and its monitored sectionalizing switches and corresponding line sections), the line section monitored by the feeder terminal unit at the strong signal point is determined to be part of the 10kV main line actually connected to the transformer in the measured area. Then, by tracing the strong signal path from the power source to the transformer in the area, the complete power supply line to which the transformer belongs can be determined, and the correction or confirmation of the topology relationship in the background database is automatically completed.

[0061] The preset threshold is obtained as follows:

[0062] The background noise amplitude is obtained based on the first signal amplitude, the mean and standard deviation of the background noise amplitude are obtained, and the preset threshold is obtained based on the mean and the standard deviation.

[0063] The first calculation formula for obtaining the preset threshold is:

[0064] ;

[0065] in, Indicates the preset threshold. This represents the mean value of the background noise amplitude. Represents the empirical coefficient. This represents the standard deviation of the background noise amplitude. In this embodiment, the background noise amplitude can be obtained through multiple on-site measurements and statistical analysis.

[0066] A distribution transformer is a type of transformer mainly used in power transmission and distribution. It is usually installed on the medium-voltage side and is mainly used to convert medium-voltage electrical energy into low-voltage electrical energy for users.

[0067] Example 2

[0068] Based on Example 1, in this example, the amplitude of the second signal detected before the injection of the target current signal is A, the amplitude of the background noise is N, and the amplitude of the first signal on the target line after the injection is S. To ensure the accuracy of the judgment, the amplitude of the target current signal needs to be adjusted so that its signal strength at the detection point is higher than the background noise (according to engineering experience, it should be more than three times the background noise). The Neyman-Pearson decision criterion can be used, setting a preset threshold so that the probability of the detected amplitude exceeding the preset threshold (i.e., the probability of misjudgment) does not exceed the preset maximum probability when there is no injected signal (only noise).

[0069] The method further includes:

[0070] Before the target current signal is injected, the second signal amplitude of the segmented switch is obtained;

[0071] Obtain the probability of misjudgment when the amplitude of the second signal is greater than the preset threshold;

[0072] Determine whether the false positive probability is less than or equal to the maximum probability; otherwise, adjust the frequency and amplitude of the target current signal.

[0073] The second formula for obtaining the false positive probability is as follows:

[0074] ;

[0075] in, Indicates the preset threshold. Indicates the probability of misjudgment. Indicates the amplitude of the second signal. This indicates that no target current signal has been injected. Indicates the maximum probability. This indicates the probability that the amplitude of the second signal exceeds a preset threshold when no target current signal is injected.

[0076] In this embodiment, to further improve the recognition accuracy and system robustness, the frequency and amplitude of the injected signal can be adaptively adjusted according to the actual on-site working conditions and the probability of misjudgment (such as background noise level, line length, load conditions, etc.). For example, if the signal strength detected under the initial injection parameters is insufficient (below the preset signal-to-noise ratio requirement or difficult to distinguish from background noise), the signal injector can be instructed to automatically increase the amplitude of the injection current, appropriately adjust the injection frequency (select a frequency with less interference within the preferred range), or extend the signal injection time to ensure that the signal strength detected on the 10kV side is always significantly higher than the background noise.

[0077] If the detected signal amplitude is lower than the preset minimum signal-to-noise ratio requirement (i.e.) It can automatically adjust the injection parameters based on the test results. Specific adjustment methods include:

[0078] The specific steps for adjusting the amplitude of the target current signal include:

[0079] The first current amplitude is obtained based on the first signal amplitude;

[0080] The target current amplitude is obtained based on the first current amplitude, the first signal amplitude, and the minimum signal-to-noise ratio;

[0081] The target current signal is updated based on the target current amplitude.

[0082] Among them, the detected signal amplitude With the amplitude of the injected current The third formula for calculating the amplitude of the first current is approximately proportional to the first current amplitude:

[0083] ;

[0084] in, Indicates the amplitude of the first signal. This represents the transmission coefficient of the line. This indicates the magnitude of the first current.

[0085] The fourth calculation formula for obtaining the target current amplitude is as follows:

[0086] ;

[0087] ;

[0088] in, Indicates the target current amplitude. Indicates the minimum signal amplitude. This indicates the amplitude of the background noise.

[0089] Within a preferred frequency range (e.g., 400Hz~600Hz), the frequency with the least background noise can be selected for injection through spectrum scanning to further improve the signal-to-noise ratio.

[0090] The specific steps for adjusting the frequency of the target current signal include:

[0091] The spectrum of different frequencies within a preset frequency range is obtained, the minimum background noise is obtained based on the spectrum, and the frequency of the target current signal is updated based on the target frequency corresponding to the minimum background noise.

[0092] In this embodiment, the adjustment method may further include:

[0093] Duration adjustment: Extending the signal injection duration by 30 seconds each time helps to improve the average signal-to-noise ratio of the detection signal and reduce the impact of instantaneous noise.

[0094] Example 3

[0095] Based on the above embodiments, this embodiment illustrates the following example:

[0096] refer to Figure 2 This is a partial topology diagram of a power distribution network in a certain section of Shaanxi Province. T1 to T7 represent different transformer substations, load1 to load7 represent different equivalent system loads, and D1 to D10 represent different feeder terminal units. The positive sequence parameters of the feeders are: R1 (resistance) = 0.032Ω / km, L1 (inductance) = 0.101mH / km, C1 (capacitance) = 0.034µF / km. The zero sequence parameters are: R0 (resistance) = 0.233Ω / km, L0 (inductance) = 0.349mH / km, C0 (capacitance) = 0.259µF / km. The lengths and loads of each feeder are shown in Table 1.

[0097] Table 1 Feeder Length and Load Parameters

[0098]

[0099] The first step was to select an initial injection frequency of 600Hz and a current amplitude of 20A based on the characteristics of the power grid in the area to be corrected. Seven operators carried these to the transformers in the T1-T7 areas and connected them.

[0100] The second step involves signal injection for 4 minutes to ensure stable sampling, analysis, and data uploading by the feeder terminal units D1-D10. The collected data is shown in Table 2.

[0101] Table 2 Data collected by feeder terminal units D1-D10

[0102]

[0103] The third step involves the feeder terminal units at D1 to D10 uploading the extracted characteristic signal amplitude data, along with their own identifiers, timestamps, and other information, to the main station system (usually deployed in the power dispatch center or distribution monitoring backend) via the communication network.

[0104] The fourth step involves the main station system performing topology discrimination and correction, with the output results shown in Table 3.

[0105] Table 3 Judgment Results Table

[0106]

[0107] Example 4

[0108] Based on the above embodiments, this embodiment also provides a distribution network transformer and line topology relationship correction system, the system comprising:

[0109] Injection unit: used to acquire the transformer to be corrected in the target area and inject a target current signal of preset frequency and amplitude into a preset side of the transformer.

[0110] Analysis unit: used to acquire first current signals of several segmented switches in the target area based on the feeder terminal unit; extract the high-frequency component amplitude of the first current signal, and obtain the first signal amplitude of the segmented switch based on the high-frequency component amplitude;

[0111] Correction unit: If the amplitude of the first signal is greater than a preset threshold, it acquires the target line of the segmented switch; and corrects the topology map of the target area based on the target line.

[0112] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0113] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for correcting the topology relationship between transformers and lines in a distribution network, characterized in that, The method includes: Obtain the transformer to be corrected in the target area, and inject a target current signal with a preset frequency and amplitude into a preset side of the transformer. Based on the feeder terminal unit, the first current signal of several segmented switches in the target area is acquired; Extract the high-frequency component amplitude of the first current signal, and obtain the first signal amplitude of the segmented switch based on the high-frequency component amplitude; If the amplitude of the first signal is greater than a preset threshold, then the target line of the segmented switch is obtained; The topology map of the target area is corrected based on the target route.

2. The method for correcting the topology relationship between transformers and lines in a distribution network according to claim 1, characterized in that, The preset threshold is obtained as follows: The background noise amplitude is obtained based on the first signal amplitude, the mean and standard deviation of the background noise amplitude are obtained, and the preset threshold is obtained based on the mean and the standard deviation.

3. The method for correcting the topology relationship between transformers and lines in a distribution network area according to claim 2, characterized in that, The first calculation formula for obtaining the preset threshold is: ； in, Indicates the preset threshold. This represents the mean value of the background noise amplitude. Represents the empirical coefficient. The standard deviation of the background noise amplitude.

4. The method for correcting the topology relationship between transformers and lines in a distribution network according to claim 2, characterized in that, The method further includes: Before the target current signal is injected, the second signal amplitude of the segmented switch is obtained; Obtain the probability of misjudgment when the amplitude of the second signal is greater than the preset threshold; Determine whether the false positive probability is less than or equal to the maximum probability; otherwise, adjust the frequency and amplitude of the target current signal.

5. The method for correcting the topology relationship between transformers and lines in a distribution network area according to claim 4, characterized in that, The second formula for obtaining the false positive probability is: ； in, Indicates the preset threshold. Indicates the probability of misjudgment. Indicates the amplitude of the second signal. This indicates that no target current signal has been injected. Indicates the maximum probability. This indicates the probability that the amplitude of the second signal exceeds a preset threshold when no target current signal is injected.

6. The method for correcting the topology relationship between transformers and lines in a distribution network according to claim 5, characterized in that, The specific steps for adjusting the amplitude of the target current signal include: The first current amplitude is obtained based on the first signal amplitude; The target current amplitude is obtained based on the first current amplitude, the first signal amplitude, and the minimum signal-to-noise ratio; The target current signal is updated based on the target current amplitude.

7. The method for correcting the topology relationship between transformers and lines in a distribution network according to claim 6, characterized in that, The third calculation formula for obtaining the amplitude of the first current is: ； in, Indicates the amplitude of the first signal. This represents the transmission coefficient of the line. This indicates the magnitude of the first current.

8. The method for correcting the topology relationship between transformers and lines in a distribution network area according to claim 7, characterized in that, The fourth calculation formula for obtaining the target current amplitude is: ； ； in, Indicates the target current amplitude. Indicates the minimum signal amplitude. This indicates the amplitude of the background noise.

9. The method for correcting the topology relationship between transformers and lines in a distribution network according to claim 4, characterized in that, The specific steps for adjusting the frequency of the target current signal include: The spectrum of different frequencies within a preset frequency range is obtained, the minimum background noise is obtained based on the spectrum, and the frequency of the target current signal is updated based on the target frequency corresponding to the minimum background noise.

10. A system for correcting the topology relationship between transformers and lines in a distribution network, characterized in that, The system includes: Injection unit: used to acquire the transformer to be corrected in the target area and inject a target current signal of preset frequency and amplitude into a preset side of the transformer. Analysis unit: used to acquire first current signals of several segmented switches in the target area based on the feeder terminal unit; extract the high-frequency component amplitude of the first current signal, and obtain the first signal amplitude of the segmented switch based on the high-frequency component amplitude; Correction unit: If the amplitude of the first signal is greater than a preset threshold, it acquires the target line of the segmented switch; and corrects the topology map of the target area based on the target line.

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