A voltage sag source positioning method and device based on two monitoring point data

Abstract

This invention belongs to the field of power quality technology and provides a method and apparatus for locating voltage sag sources based on data from two monitoring points. It determines two monitoring points where voltage monitoring devices need to be configured and acquires voltage data from these points. The type of voltage sag source is then determined using this data. If the voltage sag source is a normal operation type, it is located by searching the operation record. If the voltage sag source is a transient fault type, it is located using the two-monitoring-point method, combining the distance from the voltage sag source to the beginning of the line and the total length of the transient fault line to obtain the fault distance. This invention does not need to consider the influence of transition resistance on the calculation results, making the calculation simple and the algorithm highly efficient.

Description

Technical Field

[0001] This invention belongs to the field of power quality technology, and in particular relates to a method and device for locating voltage sag sources based on data from two monitoring points. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the development of the power industry and high technology, and the application of various highly automated and intelligent modern industrial equipment, power quality issues have increasingly attracted attention. Among these, voltage sags are considered the most significant power quality problem affecting the normal and safe operation of electrical equipment. Sensitive loads in modern industrial load systems, such as programmable logic controllers, computers, AC contactors, and variable speed motors, are highly sensitive to voltage sags. A failure in a single device or component can render an entire production line unusable, resulting in substantial economic losses. Statistics show that voltage sags cause more than 70% of power quality problems, and in developed countries in Europe and America, each voltage sag incident results in economic losses exceeding one million US dollars.

[0004] The study focuses on two types of voltage sags: "U-shaped sags" and "V-shaped sags." A "U-shaped sag" waveform exhibits a "U" shape, with the voltage dropping rapidly, remaining stable for a period, and then rising rapidly again. A "V-shaped sag" waveform exhibits a "V" shape, with the voltage dropping rapidly and then rising rapidly.

[0005] Existing methods for locating voltage sag sources are greatly affected by fault resistance. Estimating fault resistance is complicated and inaccurate. The complexity leads to a large amount of calculation, and the inaccuracy leads to poor location accuracy. Summary of the Invention

[0006] To address at least one of the technical problems mentioned above, this invention provides a method and apparatus for locating voltage sag sources based on data from two monitoring points. This method eliminates the need to consider the influence of transition resistance on the calculation results, resulting in simple calculations and high algorithm efficiency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of the present invention provides a method for locating voltage sag sources based on data from two monitoring points, comprising the following steps:

[0009] Identify two monitoring points where voltage monitoring devices need to be configured, and acquire voltage data at these monitoring points based on the voltage data of these monitoring points;

[0010] By monitoring voltage data, the type of voltage sag source can be determined. If the voltage sag source is a normal operation type, it can be located by searching the operation records. If the voltage sag source is a transient fault type, it can be located by using the two monitoring points method, combining the distance from the voltage sag source point to the beginning of the line and the total length of the transient fault line to obtain the fault distance.

[0011] A second aspect of the present invention provides a voltage sag source location device based on data from two monitoring points, comprising:

[0012] The voltage sag monitoring point configuration and measurement module is used to determine the two monitoring points where voltage monitoring devices need to be configured, and to acquire the voltage data of the monitoring points based on these monitoring points.

[0013] The voltage sag source type identification module is used to determine the type of voltage sag source by monitoring the voltage data at the monitoring point;

[0014] The voltage sag source location module is used to locate the voltage sag source if it is a normal operation type voltage sag source by searching the operation record. If the voltage sag source is a transient fault type voltage sag source, it is located by using the two monitoring points method, combining the distance from the voltage sag source point to the beginning of the line and the total length of the transient fault line to obtain the fault distance.

[0015] A third aspect of the present invention provides a computer-readable storage medium.

[0016] A computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of a voltage sag source localization method based on two monitoring point data as described in the first aspect.

[0017] A fourth aspect of the present invention provides a computer device.

[0018] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of a voltage sag source localization method based on two monitoring point data as described in the first aspect.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This invention determines the type of voltage sag source by monitoring voltage data at monitoring points. If the voltage sag source is a normal operation type, it is located by searching the operation record. If the voltage sag source is a transient fault type, it is located using a two-monitoring-point method, combining the distance from the voltage sag source point to the beginning and end of the line with the total length of the transient fault line to obtain the fault distance. This invention uses data from two monitoring points for location, eliminating the need for fault resistance estimation in the calculation and avoiding the problem of poor location accuracy caused by inaccurate fault resistance. Furthermore, the calculation only uses voltage data, requiring less data.

[0021] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This embodiment provides a flowchart for locating voltage sag sources based on data from two monitoring points;

[0024] Figure 2 This embodiment provides a schematic diagram of the power system voltage location research principle;

[0025] Figure 3 The optimal embodiment provided in this example uses an IEEE 9-node system diagram. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0028] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] Example 1

[0030] like Figure 1As shown, this embodiment provides a method for locating voltage sag sources based on data from two monitoring points, including the following steps:

[0031] Step 1: Determine the two monitoring points where voltage monitoring devices need to be configured and perform voltage measurements to obtain voltage data at the monitoring points.

[0032] In step 1, the combined optimization method is used to determine the two monitoring points where voltage monitoring devices need to be configured, including:

[0033] Establish a set of points where monitoring devices can be installed. Combine two monitoring points to create a voltage sag source location matrix. With voltage sag source location as a constraint and cost optimization as the objective, optimize the configuration of voltage sag monitoring points and determine the two monitoring points for the system configuration.

[0034] Specifically, it includes:

[0035] First, feasible nodes in the power grid are statistically analyzed, including nodes where voltage sag monitoring devices can be installed and the installation cost of each node. This establishes a set of feasible nodes and a corresponding set of installation costs.

[0036] By combining the set of installable nodes in pairs, a set of feasible combinations of two monitoring points, X = {X_{2}}, can be formed. i}, where X i Let i be the i-th element of set X, that is, the feasible combination of two monitoring points labeled i.

[0037] Based on the principle of optimal economic allocation, the following objective function is established:

[0038]

[0039] In the formula, i is the combination number containing two voltage sag monitoring points; C i The installation cost of the voltage sag monitoring device at the two-node combination i.

[0040] The constraints are:

[0041]

[0042] Where M represents the transient fault observability matrix, and the subscripts LLL, LG, LL and LLG represent four short-circuit fault types: three-phase short circuit, single-phase short circuit to ground, two-phase short circuit, and two-phase short circuit to ground, respectively.

[0043] The specific method for calculating the transient fault observability matrix is ​​as follows:

[0044]

[0045]

[0046]

[0047]

[0048] By solving the optimization model, the two monitoring points configured in the system are determined, and the combination of these two monitoring points is denoted as (k, l).

[0049] Step 2: Preprocess the voltage data at the monitoring points.

[0050] Data was collected according to national standards, and then Fourier decomposition (FFT) was performed to extract the three-phase fundamental frequency signals and remove noise. The extracted fundamental frequency signals were then subjected to phase sequence transformation using the symmetrical component method to calculate the zero-sequence, positive sequence, and negative sequence of the system. Finally, the effective value was calculated based on the positive sequence data.

[0051] In step 2, the phase sequence transformation using the symmetric component method is as follows:

[0052]

[0053] in: These are the phase voltages of phases a, b, and c, respectively, at the voltage sag monitoring points. The positive-sequence, negative-sequence, and zero-sequence voltages of phase a are obtained by transforming the voltage sag monitoring point.

[0054] Step 3: Determine the type of voltage sag source by monitoring the voltage data at the monitoring points.

[0055] First, determine whether it is a voltage sag source under normal operation or a voltage sag source caused by a transient fault;

[0056] Further analysis is needed for voltage sag sources in normal operation to determine whether they are caused by the commissioning of a large transformer or a large nonlinear load.

[0057] For transient voltage sag sources, they can be further classified into single-phase ground faults, two-phase ground faults, two-phase short-circuit faults, and three-phase short-circuit faults.

[0058] Step 4: For voltage sag sources that are normal in operation, locate them by checking the operation records. For voltage sag sources that are transient faults, locate them by using the two monitoring points method.

[0059] In step 4, the voltage sag source localization method based on two monitoring points includes:

[0060] like Figure 2 As shown, a transient fault occurs on a power system line pq, where pq are the start and end labels of the line, and its total impedance is z. (i)Let r be the voltage sag source on the line, and m be the distance from the voltage sag source r to the line's starting point p, defined as follows:

[0061]

[0062] In the formula, L pr L is the distance from the voltage sag source point r to the line start point p. pq Let pq be the total length of the line. The impedance parameter matrix of this power system under different phase sequences is obtained by the following formula:

[0063]

[0064] Where k represents one of the two monitoring systems configured in the system, and the superscript 1 indicates ascending order. Coefficient All are constants, specifically:

[0065]

[0066] in, These are the mutual impedances between nodes pq and qk in the impedance matrix before the fault, respectively. These are the self-impedances of the positive nodes p and q of the impedance matrix during the fault, respectively; z (i) Let be the total self-impedance between nodes p and q.

[0067] The optimized configuration of the two monitoring points in the system is (k, l). The data of the voltage at the two monitoring points k and l before and after the voltage dip are synchronized. The voltage at l can be obtained as follows:

[0068]

[0069]

[0070] in: and These are the positive sequence voltage values ​​at voltage sag monitoring points l and k during the voltage sag period; and These are the positive sequence voltage values ​​at voltage sag monitoring points l and k before the voltage sag. The positive sequence mutual impedance between monitoring point l and voltage sag source point r; It is divided into the positive sequence mutual impedance between monitoring point k and voltage sag source point r; Positive sequence fault current at the voltage sag source.

[0071] From equations (11) and (12), we can obtain:

[0072]

[0073] Define d as the ratio of the voltage change at the monitoring point before and after the voltage sag. kl :

[0074]

[0075] in: It is the voltage change of the positive sequence superimposed voltage component at the voltage sag monitoring point k caused by the fault; It is the voltage change at voltage sag monitoring point l caused by the positive sequence superimposed voltage component due to the fault.

[0076] The fault distance m is calculated from equations (11) and (12) as follows:

[0077]

[0078] This is a set constant.

[0079] The fault distance can then be calculated. Due to errors in calculation and measurement, the result of equation (15) may be a complex number. From an engineering perspective, the above equation should be modified as follows:

[0080]

[0081] like Figure 3 As shown, this invention utilizes an IEEE 9-node system to demonstrate the optimal embodiment. It is known that a transient fault occurs on line (5,4).

[0082] The following parameters should be calculated in advance using power system parameters:

[0083]

[0084] By establishing an optimal configuration model:

[0085]

[0086]

[0087] The feasible combinations of two monitoring points are: (5,6), (5,7)(5,9), (6,7), (6,9), (7,9).

[0088] By installing voltage sag monitoring devices at nodes 5 and 6, and performing FFT transformation on the voltages at nodes 5 and 6, the fundamental frequency components before and after the sag are obtained as follows: V 5a V 5b V 5c and V 6a V 6b V 6cThe fundamental frequency component is used to calculate the positive sequence voltages of each phase at the two nodes using the symmetrical component method. and

[0089] Via: V 5a V 5b V 5c The system is judged to have a transient single-phase short-circuit fault, and the faulty phase is phase a.

[0090] The difference is obtained by taking the voltage difference of item a in the positive sequence before and after the fault. and

[0091] Based on the above voltage change calculation:

[0092]

[0093] d 56 Substitute the values ​​to estimate the location of the voltage sag source:

[0094]

[0095] Similarly, by combining monitoring points (5,7), (5,9), (6,7), (6,9), and (7,9), the estimated values ​​of the voltage sag sources can be calculated as follows: 0.32; 0.34; 0.39; 1.36; 0.35.

[0096] 1.36 is excluded because it is not within the range of (0,1).

[0097] Based on the above, the voltage sag source is estimated to be located on line (5,4) at a distance of 32% to 37% from node 5. This section of the line should be given special attention during subsequent inspections.

[0098] Example 2

[0099] This embodiment provides a voltage sag source location device based on data from two monitoring points, including:

[0100] The voltage sag monitoring point configuration and measurement module is used to determine the two monitoring points where voltage monitoring devices need to be configured, and to acquire the voltage data of the monitoring points based on these monitoring points.

[0101] The voltage sag source type identification module is used to determine the type of voltage sag source by monitoring the voltage data at the monitoring point;

[0102] The voltage sag source location module is used to locate the voltage sag source if it is a normal operation type voltage sag source by searching the operation record. If the voltage sag source is a transient fault type voltage sag source, it is located by using the two monitoring points method, combining the distance from the voltage sag source point to the beginning of the line and the total length of the transient fault line to obtain the fault distance.

[0103] Example 3

[0104] This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps in the voltage sag source location method based on two monitoring point data as described in Embodiment 1.

[0105] Example 4

[0106] This embodiment provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps in the voltage sag source localization method based on two monitoring point data as described in Embodiment 1.

[0107] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of hardware embodiments, software embodiments, or embodiments combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage and optical storage) containing computer-usable program code.

[0108] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0109] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0110] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0111] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0112] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A voltage sag source locating method based on two monitoring point data, characterized in that, Includes the following steps: Identify two monitoring points where voltage monitoring devices need to be configured, and acquire voltage data at these monitoring points based on the voltage data of these monitoring points; By monitoring voltage data at monitoring points, the type of voltage sag source can be determined; If the voltage sag source is a normal operation voltage sag source, it is located by checking the operation records. If the voltage sag source is a transient fault voltage sag source, it is located using the two monitoring points method, combining the distance from the voltage sag source point to the beginning and end of the line with the total length of the transient fault line to obtain the fault distance. Specifically, this includes: The impedance parameter matrix of the power system under different phase sequences is obtained based on the formula for the distance from the voltage sag source to the beginning and end points of the line. Specifically: A certain transient fault line pq in a power system, pq are the first and last end labels of the line, and the total impedance of the line is , r is the voltage sag source point on the line, m is the ratio of the distance between the voltage sag source point r and the first end point p of the line to the total length of the line pq, which is defined as follows: In the formula, Let r be the distance from the voltage sag source point r to the beginning of the line, p. Let pq be the total length of the line; the impedance parameter matrix of this power system under different phase sequences is obtained by the following formula: Where k is one of the two monitoring systems configured in the system, and the superscript 1 indicates positive order; coefficient , , , , All are constants; Under the condition of data synchronization at the monitoring points, acquire the data before and after the voltage dip at two monitoring points k and l in the system; Based on the data from two monitoring points k and l in the system before and after the voltage dip, the positive sequence voltage values ​​of the two monitoring points l and k during the voltage dip are as follows: in: and Voltage sag monitoring points during voltage sag l and k The positive sequence voltage value; and Voltage sag monitoring point before voltage sag l and k The positive sequence voltage value; For monitoring points l and voltage sag source r Positive-sequence mutual impedance between; Divided into monitoring points k and voltage sag source r Positive-sequence mutual impedance between; Positive-sequence fault current at the voltage sag source; The fault distance is obtained by comparing the positive-sequence voltage values ​​at two monitoring points l and k during the voltage sag with the ratio of the voltage changes at each monitoring point before and after the voltage sag. Specifically: Define the ratio of voltage changes at the monitoring point before and after a voltage sag. : The formula for the fault distance is: In the formula, the coefficients , , , All are constants.

2. The voltage sag source localization method based on two monitoring point data as described in claim 1, characterized in that, The two monitoring points requiring voltage monitoring devices were determined using a combined optimization method, including: Establish a set of points where monitoring devices can be installed. Combine two monitoring points to create a voltage sag source location matrix. With voltage sag source location as a constraint and cost optimization as the objective, optimize the configuration of voltage sag monitoring points and determine the two monitoring points for the system configuration.

3. The voltage sag source localization method based on two monitoring point data as described in claim 2, characterized in that, The objective function is: In the formula, The numbering for a combination containing two voltage sag monitoring points; To enable voltage sag monitoring devices to be combined at two nodes Installation costs at the location; The elements of a set are used to combine two installable nodes in pairs to form feasible combinations of two monitoring points; The constraints are: Where M represents the transient fault observability matrix, and the subscripts LLL, LG, LL and LLG represent four types of short circuit faults: three-phase short circuit, single-phase short circuit to ground, two-phase short circuit, and two-phase short circuit to ground, respectively.

4. The voltage sag source localization method based on two monitoring point data as described in claim 1, characterized in that, After acquiring the voltage data at the monitoring points, the process further includes preprocessing the voltage data, specifically including: Fourier decomposition was performed on the voltage data at the monitoring points to extract the three-phase fundamental frequency signals and remove noise. The phase sequence transformation of the extracted three-phase fundamental frequency signal is performed using the symmetrical component method, and the zero-sequence positive sequence and negative sequence of the system are calculated. The effective value is calculated based on the ascending order data.

5. The voltage sag source localization method based on two monitoring point data as described in claim 1, characterized in that, The voltage sag sources for normal operation include the connection of large transformers and the connection of large nonlinear loads. The transient fault types include voltage sag sources such as single-phase ground faults, two-phase ground faults, two-phase short-circuit faults, and three-phase short-circuit faults.

6. A voltage sag source location device based on data from two monitoring points, characterized in that, include: The voltage sag monitoring point configuration and measurement module is used to determine the two monitoring points where voltage monitoring devices need to be configured, and to acquire the voltage data of the monitoring points based on these monitoring points. The voltage sag source type identification module is used to determine the type of voltage sag source by monitoring the voltage data at the monitoring point; The voltage sag source location module is used to locate the voltage sag source by searching the operation record if the voltage sag source is a normal operation type. If the voltage sag source is a transient fault type, it is located using a two-monitoring-point method, combining the distance from the voltage sag source point to the beginning and end of the line with the total length of the transient fault line to obtain the fault distance. Specifically, it includes: The impedance parameter matrix of the power system under different phase sequences is obtained based on the formula for the distance from the voltage sag source to the beginning and end points of the line. Specifically: A transient fault occurs on a power system line pq, where pq are the start and end labels of the line, and its total impedance is... Let r be the voltage sag source on the line, and m be the ratio of the distance from the voltage sag source r to the line's starting point p to the total length of the line pq, defined as follows: In the formula, Let r be the distance from the voltage sag source point r to the beginning of the line, p. Let pq be the total length of the line; the impedance parameter matrix of this power system under different phase sequences is obtained by the following formula: Where k is one of the two monitoring systems configured in the system, and the superscript 1 indicates positive order; coefficient , , , , All are constants; Under the condition of data synchronization at the monitoring points, acquire the data before and after the voltage dip at two monitoring points k and l in the system; Based on the data from two monitoring points k and l in the system before and after the voltage dip, the positive sequence voltage values ​​of the two monitoring points l and k during the voltage dip are as follows: in: and Voltage sag monitoring points during voltage sag l and k The positive sequence voltage value; and Voltage sag monitoring point before voltage sag l and k The positive sequence voltage value; For monitoring points l and voltage sag source r Positive-sequence mutual impedance between; Divided into monitoring points k and voltage sag source r Positive-sequence mutual impedance between; Positive-sequence fault current at the voltage sag source; The fault distance is obtained by comparing the positive-sequence voltage values ​​at two monitoring points l and k during the voltage sag with the ratio of the voltage changes at each monitoring point before and after the voltage sag. Specifically: Define the ratio of voltage changes at the monitoring point before and after a voltage sag. : The formula for the fault distance is: In the formula, the coefficients , , , All are constants.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the voltage sag source localization method based on two monitoring point data as described in any one of claims 1-5.

8. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the voltage sag source localization method based on two monitoring point data as described in any one of claims 1-5.

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