Feeder harmonic observability implementation method and terminal

Abstract

The invention provides a feeder harmonic observability implementation method and a terminal. The method comprises the following steps: sequentially checking harmonic monitoring conditions of each node and a branch line connected with the node from an outlet side of a power distribution network along a main line; counting the number of distribution transformers which are not subjected to harmonic monitoring from each node to the tail end of the feeder line according to the harmonic monitoring condition and recording the number as a first number, and counting the number of distribution transformers which are not subjected to harmonic monitoring in the whole line and recording the number as a second number; the first number and the second number are compared, and if the ratio of the first number to the second number is larger than or equal to a first preset threshold value, a feeder terminal is arranged at the corresponding node; and the feeder terminal is used for monitoring and collecting harmonic current and voltage data of each node branch line. According to the method, the feeder terminals are additionally arranged on the main line of the line, the sub-graphs are divided, correlation calculation of the distribution transformer power and the harmonic waves is carried out in the sub-graphs, then the most possible harmonic source distribution transformer is screened, and the requirement for feeder harmonic wave observability is met.

Description

Technical Field

[0001] The invention relates to the field of power status monitoring, and in particular to a method and a terminal for realizing observability of feeder harmonics. Background Art

[0002] The goal of harmonic state estimation is to obtain the distribution of harmonics in the current system, and then provide support for subsequent governance. The current estimation methods mainly include traditional methods such as least squares method, improved least squares method, Kalman filter model, etc. Among them, the least squares method is to establish a system observation equation that takes into account the measurement error, and then solve the harmonic state of the whole network based on the known network parameters of the system and some measured data. The improved least squares method includes the robust least squares method, etc. The robust least squares method can obtain more accurate estimation results when there are errors in the measurement data; the Kalman filter model is an effective method applied to the time domain. It is a state estimation algorithm that combines prior experience and measurement updates. The basic idea of ​​Kalman filtering is to comprehensively use the previous state and measurement values ​​to predict and estimate the state of physical quantities.

[0003] These methods basically use physical model-based methods to perform modeling and analysis, describe the relationship between nodes, and estimate the unknown node state through the harmonic state of the monitoring point. However, the insufficient number of monitoring devices in the power grid will result in the harmonic state not being observable for the entire network, making it difficult to establish the measurement equation. In addition, in actual measurement, only nodes equipped with PMU can obtain relatively accurate harmonic current and voltage phases. Inaccurate data obtained by other nodes will lead to a decrease in estimation accuracy. In addition, due to the high complexity and strong nonlinear characteristics of modern power systems, the state estimation ability of traditional methods has decreased, making it difficult to meet the high-precision estimation requirements. In addition, traditional methods require parameters such as harmonic impedance, but parameters such as harmonic impedance are difficult to obtain accurately in actual projects, so large errors are prone to occur.

[0004] At present, with the widespread access of distributed renewable energy and the increase in the number of nonlinear loads on the user side, the factors causing harmonics in the power system have further increased, and the types and propagation methods have become more and more complex. The nonlinear correlation between harmonic sources has increased, and the uncertainty and instability have become more significant. Complex coupling relationships will occur between harmonic nodes. In addition, there are currently insufficient harmonic monitoring devices in the distribution network, and the harmonic measurement information is very limited. It is difficult to accurately estimate the harmonic status of the distribution network relying solely on the existing measurement devices, and the requirements for the observability of the harmonics in the distribution network cannot be met. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method and a terminal for realizing observability of feeder harmonics, so as to solve the problem of inaccurate harmonic observation.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for realizing observability of feeder harmonics comprises the steps of: S1. Check the harmonic monitoring status of each node and the branch line connected to the node along the main line from the outlet side of the distribution network; S2. According to the harmonic monitoring situation, the number of distribution transformers from each node to the end of the feeder that are not subjected to harmonic monitoring is counted and recorded as a first number, and the number of distribution transformers that are not subjected to harmonic monitoring in the entire line is counted and recorded as a second number; S3, comparing the first number and the second number, if the ratio of the first number to the second number is greater than or equal to a first preset threshold, setting a feeder terminal at the corresponding node; The feeder terminal is used to monitor and collect harmonic current and voltage data of branch lines at each node.

[0007] In order to solve the above technical problems, another technical solution adopted by the present invention is: A feeder harmonic observability realization terminal includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor completes the following steps when executing the computer program: S1. Check the harmonic monitoring status of each node and the branch line connected to the node along the main line from the outlet side of the distribution network; S2. According to the harmonic monitoring situation, the number of distribution transformers from each node to the end of the feeder that are not subjected to harmonic monitoring is counted and recorded as a first number, and the number of distribution transformers that are not subjected to harmonic monitoring in the entire line is counted and recorded as a second number; S3, comparing the first number and the second number, if the ratio of the first number to the second number is greater than or equal to a first preset threshold, setting a feeder terminal at the corresponding node; The feeder terminal is used to monitor and collect harmonic current and voltage data of branch lines at each node.

[0008] The beneficial effects of the present invention are as follows: a method and a terminal for realizing the observability of feeder harmonics are provided, by statistically analyzing the harmonic monitoring conditions of each node of the distribution network trunk line and its branch lines, and comparing the number of transformers from each node to the end of the feeder line that have not been subjected to harmonic monitoring with the number of transformers that have not been subjected to harmonic monitoring in the entire line, and setting feeder terminals at corresponding positions according to the comparison results, that is, installing feeder terminals on the line trunk line and dividing the lines into sub-graphs, calculating the correlation between distribution transformer power and harmonics in the sub-graphs, and then screening the most likely harmonic source distribution transformer, thereby meeting the requirements for realizing the observability of feeder harmonics. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematic diagram of a flow chart of a method for realizing observability of feeder harmonics in an embodiment of the present invention; Figure 2 A schematic diagram of feeder terminal settings for a method for implementing observability of feeder harmonics in an embodiment of the present invention; Figure 3 is a specific flow chart of a method for realizing observability of feeder harmonics in an embodiment of the present invention; Figure 4 A flowchart of harmonic source calculation of a method for realizing observability of feeder harmonics in an embodiment of the present invention; Figure 5 A schematic diagram of a feeder harmonic observability implementation terminal in an embodiment of the present invention; Description of labels: 1. A feeder harmonic observability realization terminal; 2. A memory; 3. A processor. DETAILED DESCRIPTION In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in combination with the implementation modes and the accompanying drawings.

[0010] Please refer to Figure 1 as well as Figure 2 , a method for realizing observability of feeder harmonics, comprising the steps of: S1. Check the harmonic monitoring status of each node and the branch line connected to the node along the main line from the outlet side of the distribution network; S2. According to the harmonic monitoring situation, the number of distribution transformers from each node to the end of the feeder that are not subjected to harmonic monitoring is counted and recorded as a first number, and the number of distribution transformers that are not subjected to harmonic monitoring in the entire line is counted and recorded as a second number; S3, comparing the first number and the second number, if the ratio of the first number to the second number is greater than or equal to a first preset threshold, setting a feeder terminal at the corresponding node; The feeder terminal is used to monitor and collect harmonic current and voltage data of branch lines at each node.

[0011] It can be understood that a feeder refers to a cable or line used to transmit and distribute electric energy in an electric power system. In an embodiment of the present invention, the substation bus is used as the root node to lead out the feeder below it, that is, the feeders other than the substation bus can be divided into trunk lines and branch lines, and the line as a whole constitutes a radial feeder. The trunk line is led out from the bus, and branch lines are led out at each node by setting up poles and towers. Among them, if a harmonic measurement device is installed at the node, the node is observable; if the harmonic voltage of a node is known, the branch harmonic current can be measured when the harmonic impedance is known, so that the harmonic voltage of the node at the other end of the branch is observable. Similarly, if the harmonic voltages of the nodes at both ends of the branch are known, the branch harmonic current is considered to be observable.

[0012] From the above description, it can be seen that the beneficial effects of the present invention are: by statistically analyzing the harmonic monitoring conditions of each node of the distribution network trunk line and its branch lines, and comparing the number of transformers from each node to the end of the feeder that have not been harmonically monitored with the number of transformers that have not been harmonically monitored in the entire line, and setting feeder terminals at corresponding positions according to the comparison results, that is, installing feeder terminals on the main line and dividing the line into sub-graphs, calculating the correlation between distribution transformer power and harmonics in the sub-graphs, and then screening the most likely harmonic source distribution transformer, thereby meeting the requirements for the observability of feeder harmonics.

[0013] In an embodiment of the present invention, the feeder terminal is installed on the main line of the power distribution network, and the feeder terminal divides the feeder into a plurality of sub-graphs according to the installation position and monitors the harmonics of different sub-graphs.

[0014] From the above description, it can be seen that by installing the feeder terminal on the main line of the distribution network, harmonic monitoring of the entire main line and its branches can be achieved. The feeder terminal divides the entire feeder into multiple sub-graphs according to the installation location, making harmonic monitoring more refined and regionalized. Through this sub-graph separation method, the harmonic conditions in different areas can be more clearly evaluated, blind spots and repeated monitoring can be avoided, and it is helpful to locate and diagnose the harmonic sources in each area. This regional monitoring method enables power operation and maintenance personnel to perform power quality analysis more accurately, improving the efficiency and accuracy of harmonic monitoring.

[0015] In an embodiment of the present invention, the step S3 further includes a step S4: Statistics are set for harmonic monitoring from the node where the feeder terminal is set to the end of the feeder. If: N T +N L +N X ≥N H ; Where N T 、N L 、N X 、N HThey are the number of fusion terminals, feeder terminals, short-time test points, and possible harmonic source points; It is considered that the harmonic state of the node is considerable; Otherwise, return to step S2.

[0016] From the above description, it can be seen that a specific judgment standard for the observability of the harmonic state has been added, that is, the monitoring coverage of the sub-graph is evaluated by a formula. This method ensures that the harmonic state after setting the feeder terminal is observable, that is, it ensures that a sufficient number and a reasonable layout of monitoring equipment are used to cover all possible harmonic source points. Through the judgment formula, monitoring blind spots can be effectively avoided, so as to better locate and evaluate the harmonic sources in the power grid, and improve the reliability and accuracy of the power grid harmonic analysis. If the observability condition is not met, the method will return to the previous step for reconfiguration, ensuring the comprehensiveness and coverage of harmonic monitoring.

[0017] In an embodiment of the present invention, the step S1 comprises the following specific steps: From the outlet side of the distribution network, check the harmonic monitoring status of each node and the branch line connected to the node along the main line in turn. If the distribution transformer in the branch line of the node is equipped with a harmonic measurement device or the branch line of the node has undergone a short-term power quality test, the harmonic state of the node is considered to be acceptable; otherwise, it is considered that no harmonic monitoring is performed on the node.

[0018] From the above description, it can be seen that clear rules are used to determine whether the harmonic status of the node is acceptable. By judging whether the distribution transformer on the branch line is equipped with harmonic monitoring equipment or whether a short-term test of power quality has been performed during the inspection process, the efficiency of the inspection can be effectively improved. This refined judgment standard can quickly identify nodes that are not harmonic monitored, which helps to adjust the monitoring strategy in time, supplement monitoring equipment, and improve the coverage of harmonic monitoring in the distribution network.

[0019] In an embodiment of the present invention, the step S2 further comprises the steps of: Statistics are collected on the harmonic monitoring status of the distribution transformers in the branch lines of each of the nodes. If the number of the distribution transformers in the nodes that are not subjected to harmonic monitoring is greater than or equal to a second preset threshold, a feeder terminal is set at the corresponding node.

[0020] From the above description, it can be seen that the need to install a feeder terminal at a specific node is determined by setting a second preset threshold. By performing detailed harmonic monitoring statistics on the distribution transformers in each node and its branch lines, the monitoring layout can be adjusted more flexibly. This method avoids the limitations brought by fixed rules by dynamically judging the monitoring needs of different nodes, making the setting of feeder terminals more scientific and reasonable. Through this method, the layout of monitoring equipment can be better optimized, the system monitoring cost can be reduced, and the accuracy and observability of harmonic monitoring in the distribution network can be guaranteed, effectively improving the level of power quality management.

[0021] A feeder harmonic observability realization terminal 1 includes a memory 2, a processor 3, and a computer program stored in the memory 2 and executable on the processor 3. When the processor 3 executes the computer program, the steps in the feeder harmonic observability realization method are completed. Through the execution carrier of the above method, in the process of executing the above method, a feeder terminal is installed on the line trunk line and a sub-graph is divided. The correlation between the distribution transformer power and the harmonic is calculated in the sub-graph, and then the most likely harmonic source distribution transformer is selected, so as to meet the requirements for the observability of the feeder harmonics.

[0022] The present invention provides a method and a terminal for realizing observability of harmonics on a feeder line, which are mainly used to realize observability of harmonics on a trunk line, and are specifically described below in conjunction with embodiments.

[0023] Please refer to Figures 1 to 3 , Embodiment 1 of the present invention is: A method for realizing observability of feeder harmonics comprises the steps of: S1. Check the harmonic monitoring status of each node and the branch line connected to the node along the main line from the outlet side of the distribution network; S2. According to the harmonic monitoring situation, the number of distribution transformers from each node to the end of the feeder that are not subjected to harmonic monitoring is counted and recorded as the first number, and the number of distribution transformers that are not subjected to harmonic monitoring in the entire line is counted and recorded as the second number; S3. Compare the first number and the second number. If the ratio of the first number to the second number is greater than or equal to a first preset threshold, set a feeder terminal at the corresponding node; wherein the value range of the first preset threshold is between 1 / 4 and 1 / 3, preferably 1 / 3.

[0024] The feeder terminal is used to monitor and collect the harmonic current and voltage data of the branch lines of each node, and the feeder terminal is installed on the main line of the distribution network. The feeder terminal divides the feeder into multiple sub-graphs according to the installation location and monitors the harmonics of different sub-graphs.

[0025] That is, feeder terminals are installed on the main line of the line and sub-graphs are divided. The correlation between distribution transformer power and harmonics is calculated in the sub-graphs, and then the most likely harmonic source distribution transformer is screened, so as to meet the requirements for the observability of feeder harmonics. Through this sub-graph separation method, the harmonic conditions in different areas can be evaluated more clearly, blind spots and repeated monitoring can be avoided, and it is helpful to locate and diagnose the harmonic sources in each area. This regional monitoring method enables power operation and maintenance personnel to perform power quality analysis more accurately, improving the efficiency and accuracy of harmonic monitoring. Specifically, branch lines are led out at each node by setting up poles and towers.

[0026] Please refer to Figure 3 , Embodiment 2 of the present invention is: Based on the first embodiment, step S1 includes the following specific steps: From the outlet side of the distribution network, check the harmonic monitoring of each node and the branch line connected to the node along the main line in turn. If the distribution transformer in the branch line of the node is equipped with a harmonic measurement device or the branch line of the node has undergone a short-term power quality test, the harmonic state of the node is considered to be considerable; otherwise, the node is considered to have not undergone harmonic monitoring. Determine whether the harmonic state of the node is considerable through clear rules. By judging whether the distribution transformer on the branch line is equipped with harmonic monitoring equipment or whether a short-term power quality test has been performed during the inspection process, the efficiency of the inspection can be effectively improved. This refined judgment standard can quickly identify nodes that have not undergone harmonic monitoring, which helps to adjust the monitoring strategy in a timely manner, supplement monitoring equipment, and improve the coverage of harmonic monitoring in the distribution network.

[0027] At the same time, considering the sparseness of harmonic sources in the distribution network, some managers will also regularly conduct temporary short-term measurements on some areas where power quality problems may occur, and will also configure fusion terminals in some distribution transformers. Therefore, this method study sets a prerequisite: there is no more than one possible harmonic source area in a branch line that is not monitored and short-term tested.

[0028] Step S2 also includes the steps of: Statistics are taken on the harmonic monitoring of the distribution transformers in the branch lines of each node. If the number of distribution transformers in the node that are not subjected to harmonic monitoring is greater than or equal to the second preset threshold, a feeder terminal is set at the corresponding node. The value range of the second preset threshold is 4-6, preferably 5. By performing detailed statistics on the harmonic monitoring of the distribution transformers in each node and its branch lines, the monitoring layout can be adjusted more flexibly. This method avoids the limitations brought by fixed rules by dynamically judging the monitoring needs of different nodes, making the setting of the feeder terminal more scientific and reasonable. Through this method, the layout of the monitoring equipment can be better optimized, the system monitoring cost can be reduced, and at the same time, the accuracy and observability of harmonic monitoring in the distribution network can be guaranteed, effectively improving the level of power quality management.

[0029] Step S3 further includes step S4: Statistics are set for harmonic monitoring from the node where the feeder terminal is set to the end of the feeder. If: N T +N L +N X ≥N H ; Where N T 、N L 、N X 、N H They are the number of fusion terminals, feeder terminals, short-time test points, and possible harmonic source points; Then the harmonic state of the node is considered considerable; Otherwise, return to step S2.

[0030] Please refer to Figure 4 , Embodiment 3 of the present invention is: Based on the second embodiment, step S3 further includes the following steps: Calculate the correlation coefficient between the power data of the distribution transformer at the possible harmonic source location and the 3rd, 5th, 7th, and 9th harmonic data obtained by the main line feeder terminal measurement or the main line temporary measurement, obtain the distribution transformer correlation coefficient ranking related to the harmonic level emission, and perform harmonic source screening according to the ranking to determine the harmonic source location; The specific formula is as follows: ; In the formula, represents the correlation coefficient, represents the covariance, represents the sample standard deviation of X, Represents the sample standard deviation of Y. The correlation coefficient is a statistical indicator of the closeness of the relationship between the response variables. The value range of the correlation coefficient is between 1 and -1. 1 means that the two variables are completely linearly correlated, -1 means that the two variables are completely negatively correlated, and 0 means that the two variables are uncorrelated. The closer the data is to 0, the weaker the correlation. The following is the calculation formula of the correlation coefficient.

[0031] ; ; ; As the harmonic propagation distance becomes longer, the mutual coupling of harmonics will also intensify. In this embodiment, the harmonic source position is calculated using the correlation coefficient, and feeder terminals can be set for nearby nodes based on the harmonic source position, thereby performing high-precision detection of the harmonic state.

[0032] Please refer to Figure 5 , Embodiment 4 of the present invention is: A feeder harmonic observability realization terminal 1 includes a memory 2, a processor 3, and a computer program stored in the memory 2 and executable on the processor 3. When the processor 3 executes the computer program, the steps in the feeder harmonic observability realization method are completed.

[0033] In summary, the present invention provides a method and terminal for realizing the observability of feeder harmonics. First, based on the trunk line, the harmonic monitoring conditions of each node and its branches are gradually checked along the trunk line from the outlet side, which can fully cover the potential harmonic problem areas in the distribution network. By setting a threshold and comparing the proportion of unmonitored areas, the location for installing the feeder terminal can be accurately selected when necessary, thereby effectively avoiding blind or excessive installation of monitoring equipment. This reasonable monitoring layout makes the harmonic monitoring of the power grid more accurate and economical, and can find the best balance between cost and monitoring effect.

[0034] Secondly, by dividing the feeder trunk into multiple sub-graphs according to the installation location, different sub-graphs can be monitored to achieve more detailed regional monitoring. This sub-graph separation method can not only help locate the harmonic sources in different areas, but also avoid monitoring blind spots caused by uneven coverage.

[0035] In addition, detailed inspection and monitoring of the distribution transformers on each node and its branch lines, and the installation of the feeder terminal is determined by the second preset threshold, which not only improves the flexibility of monitoring, but also dynamically adjusts the layout of monitoring equipment according to the specific conditions of the power grid. This flexible configuration solution helps power grid managers better optimize the distribution of harmonic monitoring equipment, ensure that key areas can be fully monitored, and avoid waste of resources and unnecessary costs.

[0036] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention's specification and drawings, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for realizing observability of feeder harmonics, characterized in that: Includes steps: S1. Check the harmonic monitoring status of each node and the branch line connected to the node along the main line from the outlet side of the distribution network; S2. According to the harmonic monitoring situation, the number of distribution transformers from each node to the end of the feeder that are not subjected to harmonic monitoring is counted and recorded as a first number, and the number of distribution transformers that are not subjected to harmonic monitoring in the entire line is counted and recorded as a second number; S3, comparing the first number and the second number, if the ratio of the first number to the second number is greater than or equal to a first preset threshold, setting a feeder terminal at the corresponding node; The feeder terminal is used to monitor and collect harmonic current and voltage data of branch lines at each node.

2. A method for realizing observability of feeder harmonics according to claim 1, characterized in that: The feeder terminal is installed on the main line of the distribution network. The feeder terminal divides the feeder into multiple sub-graphs according to the installation position and monitors the harmonics of different sub-graphs.

3. The method for realizing observability of feeder harmonics according to claim 2, characterized in that: The step S3 further includes a step S4: Statistics are set for harmonic monitoring from the node of the feeder terminal to the end of the feeder. If: N T +N L +N X ≥N H ; Where N T 、N L 、N X 、N H They are the number of fusion terminals, feeder terminals, short-time test points, and possible harmonic source points; It is considered that the harmonic state of the node is considerable; Otherwise, return to step S2.

4. The method for realizing observability of feeder harmonics according to claim 1, characterized in that: The specific steps of step S1 are as follows: From the outlet side of the distribution network, check the harmonic monitoring status of each node and the branch line connected to the node along the main line in turn. If the distribution transformer in the branch line of the node is equipped with a harmonic measurement device or the branch line of the node has undergone a short-term power quality test, the harmonic state of the node is considered to be acceptable; otherwise, it is considered that no harmonic monitoring is performed on the node.

5. The method for realizing observability of feeder harmonics according to claim 1, characterized in that: The step S2 further comprises the steps of: Statistics are collected on the harmonic monitoring status of the distribution transformers in the branch lines of each of the nodes. If the number of the distribution transformers in the nodes that are not subjected to harmonic monitoring is greater than or equal to a second preset threshold, a feeder terminal is set at the corresponding node.

6. A feeder harmonic observability realization terminal, characterized in that: The invention comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the following steps are performed: S1. Check the harmonic monitoring status of each node and the branch line connected to the node along the main line from the outlet side of the distribution network; S2. According to the harmonic monitoring situation, the number of distribution transformers from each node to the end of the feeder that are not subjected to harmonic monitoring is counted and recorded as a first number, and the number of distribution transformers that are not subjected to harmonic monitoring in the entire line is counted and recorded as a second number; S3, comparing the first number and the second number, if the ratio of the first number to the second number is greater than or equal to a first preset threshold, setting a feeder terminal at the corresponding node; The feeder terminal is used to monitor and collect harmonic current and voltage data of branch lines at each node.

7. The feeder harmonic observability realization terminal according to claim 6, characterized in that: The feeder terminal is installed on the main line of the distribution network. The feeder terminal divides the feeder into multiple sub-graphs according to the installation position and monitors the harmonics of different sub-graphs.

8. The feeder harmonic observability realization terminal according to claim 7, characterized in that: The step S3 further includes a step S4: Statistics are set for harmonic monitoring from the node of the feeder terminal to the end of the feeder. If: N T +N L +N X ≥N H ; Where N T 、N L 、N X 、N H They are the number of fusion terminals, feeder terminals, short-time test points, and possible harmonic source points; It is considered that the harmonic state of the node is considerable; Otherwise, return to step S2.

9. The feeder harmonic observability realization terminal according to claim 6, characterized in that: The specific steps of step S1 are as follows: From the outlet side of the distribution network, check the harmonic monitoring status of each node and the branch line connected to the node along the main line in turn. If the distribution transformer in the branch line of the node is equipped with a harmonic measurement device or the branch line of the node has undergone a short-term power quality test, the harmonic state of the node is considered to be acceptable; otherwise, it is considered that no harmonic monitoring is performed on the node.

10. The feeder harmonic observability realization terminal according to claim 6, characterized in that: The step S2 further comprises the steps of: Statistics are collected on the harmonic monitoring status of the distribution transformers in the branch lines of each of the nodes. If the number of the distribution transformers in the nodes that are not subjected to harmonic monitoring is greater than or equal to a second preset threshold, a feeder terminal is set at the corresponding node.

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