Current transformer error correction method and system, computer equipment and medium

Abstract

The invention discloses a current transformer error correction method and system, computer equipment and a medium, and relates to the technical field of current transformer calibration, a current transformer error relation model considering current periodicity is adopted, the relation between current transformer errors is effectively constructed, and the current transformer errors are corrected based on the line series-parallel connection relation and the power factor angle. Through combination of a constant compensation method ignoring local errors and a particle swarm algorithm, algorithm solving efficiency is improved, the stress of loss current fluctuation on errors is reduced, through a clustering algorithm, the influence of abnormal data on error calculation is reduced, and finally, a weighted correction algorithm is adopted, so that the phase angles of the current transformers are calculated. The time-sharing error result is corrected, online calibration of the current transformer is achieved, the metering accuracy of the current transformer is improved, and technical support is provided for safe operation of an electric power system.

Description

Technical Field

[0001] The present application relates to the technical field of current transformer calibration, and in particular to a current transformer error correction method, system, computer equipment and medium. Background Art

[0002] As an important measuring device, electric energy metering devices are not only related to the commercial operation of power supply, but also closely related to the stability of the power grid and energy management. For this reason, the accuracy of the measurement of the metering device has become a common focus of attention for many parties. As an indispensable auxiliary measuring device for large current measurement, the current transformer ensures the safe operation of the power system and the collection of current data by connecting measuring instruments, relay protection devices or automatic equipment on its secondary side. Therefore, the accuracy of the current transformer has become an important device for the accuracy of electric energy measurement.

[0003] Online calibration of current transformers is different from offline calibration. Online calibration is performed when the equipment is in normal operation. There is no need to remove the current transformer from the system or interrupt the power supply. The error of the current transformer to be tested is calculated by comparing it with an open-type standard current transformer or based on historical power data. For this reason, the online calibration methods of current transformers can be divided into three categories:

[0004] (1) Comparison method based on standard current transformer: This method connects an open-type standard current transformer in series to the substation transmission line, and uses a transformer calibrator to measure the error of the current transformer to be tested by comparing it with the open-type standard current transformer. The principle diagram of online calibration based on standard current transformer is shown in Figure 1. Figure 1 shown.

[0005] (2) Prediction of current transformer error fluctuation based on external factors. The current transformer error changes due to external factors (such as temperature, humidity, current, voltage, etc.). Therefore, the correlation between the external environment and the current transformer error is considered, and the current transformer error is predicted by measuring the external environment.

[0006] (3) Based on the data-driven current transformer error calibration method, Kirchhoff's current law is used as the core. According to the relationship between the transmission line currents, the relationship between the current transformer errors is deduced, and the current transformer error results are calculated.

[0007] In summary, the current online calibration of current transformers is mainly focused on the comparison method based on standard current transformers. This method is similar to the offline calibration principle, but the comparison method based on standard current transformers requires live work, and high-voltage work has certain safety risks. At the same time, it still requires a lot of manpower and material resources in the calibration operation. The prediction of current transformer error fluctuation based on external factors mainly considers the impact of the external environment on the current transformer error, and does not consider the internal changes of the current transformer due to long-term use, such as magnetization, insulation aging, etc., which causes error accumulation, and cannot achieve accurate calculation of the current transformer error. While data-driven current transformer error calibration can achieve calibration safely and efficiently, the following problems still exist: (1) The solution to the current transformer error relationship based on Kirchhoff's current law is affected by current fluctuations and losses. The error solution method based on constant compensation particle swarm has a large error between the calculated result and the actual error value; (2) The particle swarm algorithm is prone to fall into a local optimal solution, and its local optimal solution has a certain impact on the calculated current transformer error; (3) Constant compensation reduces the impact of loss current fluctuations by ignoring local errors, but ignores the situation where the error in the current transformer causes a certain deviation between the solution and the actual result. Summary of the invention

[0008] In order to solve the problem that the solution results of the existing current transformer online calibration technology based on constant compensation deviate from the actual situation, the present application proposes a current transformer error correction method, system, computer equipment and medium.

[0009] In the first aspect, the present application is implemented through the following technical solutions:

[0010] A current transformer error correction method, comprising:

[0011] According to the substation topology diagram and Kirchhoff's current law, the current transformer error relationship model taking into account the current periodicity is constructed by comprehensively considering the ratio difference, angle difference and current fluctuation.

[0012] Based on the series-parallel relationship and power factor angle of the substation lines, the phase angle relationship of the current between the lines is calculated to provide data support for the current transformer error calculation;

[0013] The current transformer error relationship model is simplified by selectively ignoring the local error through the current phase angle relationship, and the simplified current transformer error relationship model is solved by using a particle swarm algorithm to obtain a current transformer time-sharing error;

[0014] The abnormal points in the time-sharing error of the current transformer are removed, and the time-sharing error of the current transformer after the abnormal points are removed is corrected based on a weighted correction algorithm to obtain a current transformer error, thereby realizing online calibration of the current transformer.

[0015] In some implementations, the process of constructing a current transformer error relationship model taking into account current periodicity specifically includes:

[0016] Based on Kirchhoff's current law and the substation topology diagram, a current relationship between lines is constructed; the current relationship between lines is: the sum of all currents flowing into nodes, all currents flowing out of nodes, and loss current is zero;

[0017] According to the current transformer ratio difference and angle difference, the relationship between the current transformer secondary side measurement data and the primary side actual data is established; wherein the current transformer ratio difference and angle difference together constitute the current transformer error;

[0018] Based on the relationship between the currents between the lines, the relationship between the secondary side measurement data of the current transformer and the actual data on the primary side, and combined with the periodic change of the current, a current transformer error relationship model taking into account the periodicity of the current is constructed; the current transformer error relationship model is expressed as:

[0019]

[0020] Where k represents the total number of lines, N i represents the transformation ratio of the current transformer on the i-th line, i 有效_i represents the effective value of the secondary current of the current transformer on the i-th line, ε i represents the ratio difference of the current transformer on the i-th line, t represents a certain moment, φ i represents the phase angle of the secondary current of the current transformer on the i-th line, Δφ i Represents the angular difference of the current transformer on the i-th line.

[0021] In some implementations, the process of calculating the phase angle relationship of the current between the lines specifically includes:

[0022] According to the collected power data, the current phase angle is calculated, and the calculation formula is:

[0023]

[0024] Among them, P is the active power of the line, V is the effective value of the line voltage, I is the effective value of the line current, φ I is the current phase angle.

[0025] In some implementations, the current transformer error relationship model simplification process specifically includes:

[0026] When simplifying the model, when the current phase angle is 0°, the angle difference of the current transformer is ignored; when the current phase angle is 90°, the ratio difference of the current transformer is ignored;

[0027] A threshold is set, and the relationship between the power factor of the line and the threshold is compared. By ignoring the current transformer error of a single line, the constant term in the current transformer error relationship model is compensated, and the simplified current transformer error relationship model is obtained:

[0028]

[0029] Wherein, j represents the current transformer error of the jth line which is ignored.

[0030] In some embodiments, removing the abnormal point in the time-sharing error of the current transformer, correcting the time-sharing error of the current transformer after removing the abnormal point based on a weighted correction algorithm, obtaining the current transformer error, and then realizing the online calibration of the current transformer specifically includes:

[0031] According to the time-sharing error of the current transformer, an average value is calculated as a reference point for a calculation;

[0032] Taking the reference point as the center, clustering the calculated time-sharing error of the current transformer is performed using a clustering algorithm to remove abnormal points;

[0033] After the abnormal point is removed, a weighted current transformer error correction algorithm is used to correct the current transformer time-sharing error after the abnormal point is removed to obtain a current transformer error value;

[0034] The current transformer error value is compared with the regulation standard to achieve current transformer calibration.

[0035] In some implementations, the current transformer time-sharing error correction process specifically includes:

[0036] According to the current size, a weight value is assigned to each current transformer, and the weight value calculation formula is:

[0037]

[0038] Among them, W j is the weight of the jth line, S j is the arithmetic sum of the currents in the jth line, S max is the maximum value of the arithmetic sum of the current in the line;

[0039] According to the weight value, the current transformer error value is calculated, and the calculation formula is:

[0040]

[0041] Among them, ε i represents the current transformer error of the i-th line, ε j_i It represents the time-sharing error of the current transformer of the i-th line after clustering when the error of the current transformer of the j-th line is ignored.

[0042] In a second aspect, the present application proposes a current transformer error correction system, comprising:

[0043] A model building module, wherein the model building module builds a current transformer error relationship model taking into account current periodicity by comprehensively considering ratio difference, relative difference and current fluctuation according to the substation topology diagram and Kirchhoff's current law;

[0044] A phase angle calculation module, which calculates the phase angle relationship of the current between the lines based on the series and parallel relationship of the lines and the power factor angle, and provides data support for the current transformer error calculation;

[0045] A simplified solution module, wherein the simplified solution module selectively ignores local errors through the current phase angle relationship, simplifies the current transformer error relationship model, and uses a particle swarm algorithm to solve the simplified current transformer error relationship model to obtain a current transformer time-sharing error;

[0046] And, an error correction module, which removes abnormal points in the current ventilation time-sharing error, corrects the current transformer time-sharing error after removing the abnormal points based on a weighted correction algorithm, obtains the current transformer error, and then realizes online calibration of the current transformer.

[0047] In some embodiments, the model building module further comprises:

[0048] A line relationship unit, wherein the line relationship unit is based on Kirchhoff's current law and the substation topology diagram to construct a current relationship between lines; the current relationship between lines is: the sum of all currents flowing into nodes, all currents flowing out of nodes, and loss current is zero;

[0049] A transformer transmission unit, wherein the transformer transmission unit constructs a relationship between the current transformer secondary side measurement data and the primary side actual data according to the current transformer ratio difference and the angle difference; wherein the current transformer ratio difference and the angle difference together constitute the current transformer error;

[0050] And, a model unit, wherein the model unit constructs a current transformer error relationship model taking into account the current periodicity based on the relationship between the line currents, the relationship between the current transformer secondary side measurement data and the primary side actual data, and the current periodicity. The current transformer error relationship model is expressed as:

[0051]

[0052] Where k represents the total number of lines, N i represents the transformation ratio of the current transformer on the i-th line, i 有效_i represents the effective value of the secondary current of the current transformer on the i-th line, ε i represents the ratio difference of the current transformer on the i-th line, t represents a certain moment, φ i represents the phase angle of the secondary current of the current transformer on the i-th line, Δφ i Represents the angular difference of the current transformer on the i-th line.

[0053] In a third aspect, the present application proposes a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0054] In a fourth aspect, the present application proposes a computer-readable storage medium having a computer program stored thereon, wherein the computer program implements the steps of the above method when executed by a processor.

[0055] The present application proposes a current transformer error correction method, system, computer device and medium, which solves the current transformer error through power data, and realizes the online calibration of the current transformer through the state distribution presented by the result, avoiding the limitations and safety risks brought by the comparison with the open-type standard current transformer;

[0056] The present application proposes a current transformer error correction method, system, computer equipment and medium. The method uses the time-sharing error result of the current transformer calculated by the constant compensation particle swarm algorithm as the basic data, performs a mean centering operation on the data, and obtains an error result with consistent characteristic dimensions, which is convenient for subsequent distance calculation; a clustering algorithm is used to calculate the deviation between the points in the cluster and the centroid, and the abnormal points with large deviations are removed to obtain the clustering results, which can effectively avoid the influence of the local optimal solution on the error; a data-weighted error correction algorithm is used to avoid the influence of the volatility of the current data on the error result, and a theoretical basis is provided for the calibration of the current transformer by comparing the current transformer error calculation result with the actual allowable current transformer error threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The drawings described herein are used to provide a further understanding of the embodiments of the present application, constitute a part of the present application, and do not constitute a limitation on the embodiments of the present application. In the drawings:

[0058] Figure 1 This is the schematic diagram of online calibration based on standard current transformer;

[0059] Figure 2 A flow chart of the online calibration method provided in an embodiment of the present application;

[0060] Figure 3 A diagram showing the relationship between ratio difference and angle difference at different phase angles provided in the embodiment of the present application;

[0061] Figure 4 A flow chart of a method for solving current transformer errors based on selective constant compensation provided in an embodiment of the present application;

[0062] Figure 5 A DBSCAN clustering flow chart provided for an embodiment of the present application;

[0063] Figure 6 Schematic diagram of the online calibration system provided in the embodiment of the present application;

[0064] Figure 7 A relationship diagram of current, voltage and power factor provided in an embodiment of the present application;

[0065] Figure 8 A bar graph of the current transformer ratio difference results provided in an embodiment of the present application;

[0066] Fig. 9 The absolute error curve of the current transformer ratio provided in the embodiment of the present application;

[0067] Fig.10 A distribution diagram of the time-sharing ratio difference calculation results of the particle swarm algorithm, particle swarm algorithm + weighted correction, and constant compensation + weighted correction provided in the embodiments of the present application;

[0068] Fig.11 A comparison chart of different algorithms provided in the embodiments of this application. DETAILED DESCRIPTION

[0069] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with examples and drawings. The illustrative implementation scheme of the present application and its description are only used to explain the present application and are not intended to limit the present application.

[0070] Example:

[0071] In view of the problem that the solution result of the existing current transformer online calibration method based on constant compensation is different from the actual situation, this embodiment proposes a current transformer error correction method. Figure 2 As shown, the method proposed in this embodiment specifically includes the following steps:

[0072] Step 100, based on the substation topology diagram and Kirchhoff's current law, comprehensively considering the ratio difference, angle difference and current fluctuation, construct a current transformer error relationship model taking into account the current periodicity.

[0073] This step 100 is mainly based on the substation topology diagram, combined with the correlation between line currents and the periodic change characteristics of AC power, and considering the current transformer transmission equation containing errors, to deduce the error relationship between current transformers, specifically including:

[0074] Step 101, based on Kirchhoff's current law (KCL law) and the substation topology diagram, construct the current relationship between the lines.

[0075] Combined with the substation topology diagram, the 220KV line is regarded as a closed surface, and the current flowing into the node Recorded as a positive value, the current flowing out of the node It is recorded as a negative value. At the same time, since the current in the line is affected by the stray capacitance of the equipment in the station to the ground, its loss current is relatively small, so it is regarded as a constant value I 损 , which is always negative. Construct the relationship between line currents:

[0076] Step 102, constructing a relationship between the secondary side measurement data of the current transformer and the primary side actual data according to the current transformer ratio difference and the angle difference.

[0077] Since the 220KV line of the substation has high current and high voltage, it cannot be directly connected to the current acquisition device for data collection. Therefore, the current transformer is connected in series in the line to convert the high current into a small current and measure the current data. The actual current transformer may cause insulation material degradation and core performance degradation due to long-term use, which will affect the measurement of the current transformer. The actual current transformer primary side current I p With the secondary current i s The relationship between can be expressed as:

[0078] I p =N×i s ×(1+ε)×e jΔφ (2)

[0079] Where N is the current transformer ratio, ε is the current transformer ratio difference, Δφ is the current transformer angle difference, and j is the imaginary unit.

[0080] Step 103, based on the current relationship between the lines, the current transformer current transmission relationship (i.e., the relationship between the primary side current and the secondary side current), combined with the current periodic change, a current transformer error relationship model taking into account the current periodicity is constructed to provide model support for subsequent error calculations.

[0081] Since the current of the 220KV line is AC, not DC, its current size is periodic and changes in the form of a sine wave, and the current data collected by the collection device is the effective value I 有效 , rather than the instantaneous value and the maximum amplitude, therefore, the current transformer error relationship model taking into account the current periodicity is:

[0082]

[0083] Where k represents the total number of all lines in the 220KV line closure, N i represents the transformation ratio of the current transformer on the i-th line, i 有效_i represents the effective value of the secondary current of the current transformer on the i-th line, ε i represents the ratio difference of the current transformer on the i-th line, t represents a certain moment, φ i represents the phase angle of the secondary current of the current transformer on the i-th line, Δφ i Represents the angular difference of the current transformer on the i-th line.

[0084] It should be noted that based on the above current transformer error relationship model, the current transformer time-sharing error can be obtained by inputting power data for solution. However, due to the limitation of data collection by the electric energy metering device, there is no current phase angle data. Therefore, it is necessary to solve the phase angle data of the line current based on the power data.

[0085] Step 200, based on the series-parallel relationship and power factor angle of the substation lines, the phase angle relationship of the current between the lines is calculated to provide data support for the current transformer error calculation.

[0086] The step 200 specifically includes:

[0087] Step 201: Acquire power data through a metering and collection device.

[0088] Due to the factors of frequency and type of data collected by electric energy metering devices, power data mainly includes current data, voltage data, meter code data, power data, power factor data, and transformation ratio data of current transformer and voltage transformer. The types, accuracy and detailed description of power data are shown in Table 1.

[0089] Table 1 Power data

[0090]

[0091] Step 202, according to the power data, based on the series-parallel relationship of the lines and the power factor angle, calculate the phase angle relationship of the current between the lines.

[0092] According to the current transformer error relationship model, the current transformer cannot measure the current phase angle, so the phase angle needs to be estimated. The active power formula is as follows:

[0093] P=V·I·cos(θ) (4)

[0094] Among them, P is the active power of the line, V is the effective value of the line voltage, I is the effective value of the line current, and cos(θ) is the power factor of the line, which represents the ratio of active power to apparent power, reflecting the efficiency of power use. The power factor angle can also be calculated based on the phase angle. The specific formula is as follows:

[0095] θ=φ V -φ I (5)

[0096] Where θ is the phase difference between line current and voltage, i.e., the power factor angle; φ V is the phase angle of voltage; φ I is the current phase angle. Because in a 220kV transmission system, when multiple lines are connected to the same bus, in an ideal state, the voltage phase angles of these lines are the same, so the voltage phase angle is regarded as 0, -θ is the phase relationship between the line currents, and the current phase angle relationship can be expressed as:

[0097]

[0098] After calculating the current phase angle according to the power data, substitute it into the current transformer error relationship model taking into account the periodicity, input the power data for solution, and the current transformer time-sharing error can be obtained. However, the ratio difference and the angle difference are part of the current transformer error, and the two affect each other, making it difficult to solve. To this end, in order to solve the problem of loss current volatility and difficulty in solving, this embodiment further proposes an error suppression solution algorithm based on selective constant compensation, and realizes the current transformer time-sharing error calculation by simplifying the current transformer error relationship model taking into account the current periodicity.

[0099] Step 300 , selectively ignoring local errors through the current phase angle relationship, simplifying the current transformer error relationship model, and using a particle swarm algorithm to solve the simplified current transformer error relationship model to obtain a current transformer time-sharing error.

[0100] Affected by the volatility of loss current, when the loss current fluctuates to a certain extent, the calculation result will change greatly. Therefore, this embodiment ignores the error of a single current transformer and compensates the constant term in the current transformer error relationship model. Specifically, based on the error suppression solution method of the selective constant compensation particle swarm, on the basis of the distributed particle swarm, by selectively ignoring part of the current transformer error, the constant term is compensated to suppress the influence of the loss current volatility on the error calculation, and the compensated current transformer error relationship model is obtained.

[0101] This embodiment simplifies the current transformer error relationship model taking into account the current periodicity while ensuring the calculation accuracy. On the basis of the distributed particle swarm algorithm, a constant compensation is proposed to reduce the volatility of the loss current. The model simplification process is as follows:

[0102] Since the ratio difference and angle difference have different effects on the secondary side data of the current transformer at different phases, in order to explore the ratio difference and angle difference in the current transformer error, it is assumed that there is a current transformer with a ratio difference of 10%, an angle difference of 0.1, and a transformation ratio of 1. Under different phase angles, by analyzing the relationship between the ratio difference and the angle difference, the current transformer error relationship model taking into account the current periodicity is simplified. The relationship between the ratio difference and the angle difference at different phase angles is as follows: Figure 3 shown.

[0103] Based on the relationship diagram of ratio difference and angle difference at different phase angles, it can be seen that when the current phase angle is 0°, the current error is mainly caused by the ratio difference; when the current phase angle is 90°, the current error is mainly caused by the angle difference. Based on this rule, when simplifying the model, when the current phase angle is 0°, the angle difference of the current transformer is ignored; when the current phase angle is 90°, the ratio difference of the current transformer is ignored. Based on this, the current transformer error relationship model can be simplified to:

[0104]

[0105] Based on the simplified model, the online calibration of the current transformer can be achieved by solving the angle difference and ratio difference respectively.

[0106] To this end, taking the solution of the current transformer ratio difference as an example, due to the volatility of the loss current and the small loss current, when the particle swarm algorithm is used to solve the problem based on the power data, it is easy to cause the current transformer error calculation to be inaccurate. Therefore, this embodiment is based on the simplified current transformer error relationship model and adopts the current transformer error solution method with selective constant compensation for solution. Since the power factor between the large current and the large voltage is basically 0, and the phase angle relationship between the two is 90°, therefore, based on the phase angle relationship, a threshold is set to select part of the current transformer error that needs to be ignored. The specific solution process is as follows Figure 4 shown.

[0107] By setting the threshold, comparing the relationship between the threshold and the power factor, and ignoring the ratio difference of different current transformers, the error caused by the loss current fluctuation is reduced, and the ratio difference of other current transformers is calculated. Assume that the current transformer error of the jth line is ignored. When the power factor of the jth line is cos(φ j ) is greater than a threshold value (e.g. 0.01), it indicates that the current phase angle is greatly different and the current value is too small to ignore the error; when the power factor cos(φ j ) is less than the threshold, indicating that the current phase angle is basically 90°, and the current value is large enough to ignore its error. Therefore, when the current transformer ratio difference of the jth line is ignored, its current transformer error relationship model can be simplified as follows:

[0108]

[0109] Selectively ignore the local error, get a simplified current transformer error relationship model, and based on the power data, use the particle swarm algorithm to solve the time-sharing ratio difference results of other current transformers. The current transformer ratio difference result of the i-th line ignoring the current transformer error of the j-th line can be recorded as ε j_i However, the calculated current transformer ratio difference ignores the local ratio difference, resulting in a certain error between the calculated ratio difference and the actual ratio difference. Therefore, this embodiment further performs subsequent correction on the time-sharing ratio difference to obtain the actual ratio difference result.

[0110] Similarly, by setting the threshold, comparing the relationship between the threshold and the power factor, and ignoring the angle difference of different current transformers, the error caused by the fluctuation of loss current is reduced, and the angle difference of other current transformers is calculated. The current transformer error relationship model can be simplified as:

[0111]

[0112] It should be noted that the particle swarm algorithm uses a random generation method to ensure the randomness of the particle position. It is precisely because of the randomness of the initialization position that it takes a lot of time to solve the optimal solution. Therefore, this embodiment adopts a dynamic adjustment method of the inertia weight, which can specifically adopt a linear decreasing inertia weight, and the formula is as follows:

[0113]

[0114] Among them, w(t) is the inertia weight at the tth iteration, w max is the initial value of the inertia weight, w min is the minimum value of the inertia weight, T max is the maximum number of iterations, and t is the current number of iterations.

[0115] Step 400, remove the abnormal points in the current transformer time-sharing error, and correct the current transformer time-sharing error after the abnormal points are removed based on a weighted correction algorithm to obtain the current transformer error, thereby achieving online calibration of the current transformer.

[0116] The step 400 specifically includes:

[0117] Step 401, according to the time-sharing error of the current transformer, the average value thereof is used as a reference point.

[0118] Step 402: clustering the current transformer time-sharing error calculation results using a clustering algorithm with the reference point as the center to remove abnormal points.

[0119] Step 403, after the abnormal points are removed, a weighted current transformer error correction algorithm is used to correct the current transformer time-sharing error calculation result to obtain a current transformer error value.

[0120] Step 404, comparing the current transformer error value with the regulation standard, thereby achieving current transformer calibration.

[0121] This embodiment is described in detail by taking the time-sharing ratio difference of a power transformer as an example.

[0122] First, the average value of the current transformer time-sharing ratio difference is obtained, which is expressed as:

[0123]

[0124] in, In order to ignore the current transformer ratio difference of the j-th line, the average ratio difference of other current transformers is calculated. The average ratio difference is affected by the current transformer ratio difference of the j-th line. Therefore, the ratio difference result is not the actual error result of the current transformer.

[0125] Then, the DBSCAN (Density-Based Spatial Clustering of Applications with Noise) algorithm is used to identify clusters by detecting the local density of data points. It divides data points into core points, boundary points, and noise points. A core point is a point whose number of points in its neighborhood reaches the preset minimum value (MinPts); a boundary point is a point in the neighborhood of a core point but does not meet the minimum point number requirement; a noise point is neither a core point nor a boundary point. By expanding clusters from core points, DBSCAN can discover clusters of any shape and automatically identify and process noise data. The DBSCAN flow chart is shown below. Figure 5 shown.

[0126] For a given data point p, the ε-neighborhood refers to all points within a circle (or a hypersphere in multidimensional space) with a radius of ε and centered at p. The formula is:

[0127] N ε (p)={q∈D|dist(p,q)≤ε} (13)

[0128] Among them, N ε (p) is the ε-neighborhood of point p; dist(p,q) is the distance between point p and point q.

[0129] Then, according to the time-sharing error data under different current transformer error conditions after removing the abnormal points, the weighted correction current transformer error solution algorithm is adopted. According to the current size, a weight value is assigned to each current transformer, and the actual ignored current transformer error value is calculated according to the weight relationship. The weight relationship is as follows:

[0130]

[0131] Among them, W j is the weight of the jth line, S j is the arithmetic sum of the currents in the jth line, S max is the maximum value of the arithmetic sum of the current in the line. Its calculation formula can be used to calculate the current I on line j. j It is expressed as:

[0132]

[0133] Based on this, the current transformer error calculation formula is:

[0134]

[0135] In the formula, ε i represents the calculated current transformer error of the i-th line, ε j It represents the time-sharing error (ratio difference) of the current transformer of the i-th line after clustering when the current transformer error of the j-th line is ignored. The above formula shows that when different current transformer errors are ignored, other current transformer errors will be obtained. According to the error and the current size, the actual current transformer error can be calculated.

[0136] Similarly, for the angle difference, the current transformer error calculation formula is:

[0137]

[0138] In the formula, φ i represents the calculated current transformer error of the i-th line, φ j_iIt represents the time-sharing error (angle difference) of the current transformer of the i-th line after clustering when the error of the current transformer of the j-th line is ignored.

[0139] It should be noted that the execution order of step 100 and step 200 in the above method proposed in this embodiment is not limited. Step 100 can be executed first and then step 200, or step 200 can be executed first and then step 100, or step 100 and step 200 can be executed simultaneously.

[0140] The current transformer online calibration method proposed in this embodiment solves the current transformer error through power data, and realizes the online calibration of the current transformer through the state distribution presented by the result, avoiding the limitations and safety risks brought by the comparison with the open-type standard current transformer. The current transformer error relationship model taking into account the current periodicity is adopted to effectively construct the relationship between the current transformer errors; based on the series-parallel relationship of the lines and the power factor angle, the relationship between the current transformer phase angles is obtained; by combining the constant compensation method that ignores local errors with the particle swarm algorithm, the efficiency of the solution algorithm is improved and the influence of the loss current volatility on the error is reduced; through the clustering algorithm, the influence of abnormal data on the error calculation is reduced, and finally the weighted correction algorithm is adopted to correct the time-sharing error results, so as to realize the online calibration of the current transformer, improve the measurement accuracy of the current transformer, and provide technical support for the safe operation of the power system.

[0141] Based on the same technical concept as above, this embodiment also proposes a current transformer error correction system, such as Figure 6 As shown, the system includes:

[0142] The model building module constructs a current transformer error relationship model taking into account the current periodicity by comprehensively considering the ratio difference, angle difference and current fluctuation according to the substation topology diagram and Kirchhoff's current law.

[0143] The phase angle calculation module calculates the phase angle relationship of the current between lines based on the series and parallel relationship of the lines and the power factor angle, providing data support for the current transformer error calculation.

[0144] The simplified solution module selectively ignores local errors through the current phase angle relationship, simplifies the current transformer error relationship model, and uses a particle swarm algorithm to solve the simplified current transformer error relationship model to obtain the current transformer time-sharing error.

[0145] And, an error correction module, which removes abnormal points in the current transformer time-sharing error, corrects the current transformer time-sharing error after the abnormal points are removed based on a weighted correction algorithm, obtains the current transformer error, and then realizes the online calibration of the current transformer.

[0146] Furthermore, the model building module also includes:

[0147] The line relationship unit, based on Kirchhoff's current law (KCL law) and the substation topology diagram, constructs the current relationship between lines. The details are as described in the above step 101, which will not be repeated here.

[0148] The transformer transmission unit, which constructs the relationship between the current transformer secondary side measurement data and the primary side actual data according to the current transformer ratio difference and angle difference, is as described in the above step 102 and will not be described in detail here.

[0149] And, a model unit, which constructs a current transformer error relationship model taking into account the current periodicity based on the relationship between the currents between the lines, the relationship between the secondary side measurement data of the current transformer and the actual data on the primary side, and the periodic change of the current, to provide a model support for the subsequent error calculation. The details are as described in the above step 103, and will not be repeated here.

[0150] Furthermore, the phase angle solution module also includes:

[0151] The data acquisition unit acquires power data through the metering and acquisition device. The specific data types acquired are as described in the above step 201, and will not be described in detail here.

[0152] And, a calculation unit, which calculates the phase angle relationship of the current between the lines based on the power data, the series-parallel relationship of the lines and the power factor angle. The specific calculation process is as described in the above step 202, and will not be repeated here.

[0153] Furthermore, the error correction module also includes:

[0154] The average value unit uses the time-sharing error of the current transformer as a reference point.

[0155] The abnormality removal unit uses a reference point as a center and adopts a clustering algorithm to cluster the calculated time-sharing errors of the current transformer to remove abnormal points.

[0156] The weighted correction unit adopts a weighted current transformer error correction algorithm to correct the time-sharing error of the current transformer after the abnormal point is removed, so as to obtain a current transformer error value.

[0157] And, a comparison and calibration unit, which compares the error value of the current transformer with the regulation standard, thereby realizing the current transformer calibration.

[0158] In order to verify the effects of the above method and system proposed in this embodiment, the above method and system proposed in this embodiment are described through experimental data.

[0159] The experimental results of the current phase angle calculation based on the power factor angle are as follows: Figure 7 As shown, according to the power data collected by the metering and collection device, based on the line parallel relationship and the power factor angle, the phase angle relationship of the current between the lines is calculated. Figure 7 It can be seen that the power factor of large current and small current is quite different. The power factor of small current is larger, that is, the phase angle between small current and voltage is larger, while the phase angle between large current and voltage is smaller and does not change much. At the same time, it can be seen from the figure that the phase angle between the small current and voltage of the line is [-22.65°, 22.65°], while the phase angle between the large current and voltage of the line is approximately 90°.

[0160] The experimental results of the current transformer error solution algorithm based on selective constant compensation are as follows: Figure 8 As shown, from Figure 8 It can be seen that the actual ratio difference of the current transformer is within 0.1%, while most of the calculated results are within 0.1%, and the ratio difference range is within the specification range.

[0161] The experimental results of the current transformer online calibration method are as follows Fig. 9 As shown in the figure, in order to evaluate the effectiveness of each module and analyze the contribution of different modules to the model, each module is added separately on the basis of the particle swarm algorithm. By comparing the mean absolute error of the current transformer ratio difference, the smaller the mean absolute error, the more accurate the model calculation. Fig. 9 It can be seen that the average absolute error of the particle swarm algorithm with constant compensation is smaller than that of the particle swarm algorithm in the first 15 iterations, but due to the neglect of some errors, its average absolute error is greater than that of the particle swarm algorithm in subsequent iterations. The average absolute error of the particle swarm algorithm with weighted correction is lower than that of the particle swarm algorithm, but the effect is not obvious. The error of the particle swarm algorithm with constant compensation and weighted correction (i.e., the above method proposed in this embodiment) is significantly reduced, which shows from the side that constant compensation can effectively reduce the volatility of errors during calculation.

[0162] In order to explore the effects of constant compensation and weighted correction on the calculation results, the distribution of experimental calculation results of particle swarm algorithm, particle swarm algorithm + weighted correction algorithm and constant compensation + weighted correction algorithm was statistically analyzed, and the following results were obtained: Fig.10 The results are shown. Fig.10 It can be seen that the distribution of the calculation results of the particle swarm + weighted correction algorithm does not change much, which means that the error volatility of the calculation results of the particle swarm algorithm without constant compensation is strong, and the loss current volatility is strong.

[0163] In order to verify the advantages of the method proposed in this embodiment, four mainstream solution algorithms are selected for comparison. Under the same current data set and current transformer error relationship, the current transformer error is solved. The absolute errors of different algorithms are as follows: Fig.11 As shown in the figure, it can be seen that the absolute error of the current transformer calculated by the method proposed in this embodiment is the smallest, and the current transformer error can be effectively calculated with an accuracy within 0.2%, thereby improving the calibration accuracy and providing technical support for the safe operation of the power system.

[0164] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0165] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0166] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0167] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1The steps for the functions specified in one or more boxes.

[0168] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only the specific implementation method of the present application and is not intended to limit the scope of protection of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A current transformer error correction method, characterized in that: include: According to the substation topology diagram and Kirchhoff's current law, the current transformer error relationship model taking into account the current periodicity is constructed by comprehensively considering the ratio difference, angle difference and current fluctuation. Based on the series-parallel relationship and power factor angle of the substation lines, the phase angle relationship of the current between the lines is calculated to provide data support for the current transformer error calculation; The current transformer error relationship model is simplified by selectively ignoring the local error through the current phase angle relationship, and the simplified current transformer error relationship model is solved by using a particle swarm algorithm to obtain a current transformer time-sharing error; The abnormal points in the time-sharing error of the current transformer are removed, and the time-sharing error of the current transformer after the abnormal points are removed is corrected based on a weighted correction algorithm to obtain a current transformer error, thereby realizing online calibration of the current transformer.

2. A current transformer error correction method according to claim 1, characterized in that: The process of constructing the current transformer error relationship model taking into account the current periodicity specifically includes: Based on Kirchhoff's current law and the substation topology diagram, a current relationship between lines is constructed; the current relationship between lines is: the sum of all currents flowing into nodes, all currents flowing out of nodes, and loss current is zero; According to the current transformer ratio difference and angle difference, the relationship between the current transformer secondary side measurement data and the primary side actual data is established; wherein the current transformer ratio difference and angle difference together constitute the current transformer error; Based on the relationship between the currents between the lines, the relationship between the secondary side measurement data of the current transformer and the actual data on the primary side, and combined with the periodic change of the current, a current transformer error relationship model taking into account the periodicity of the current is constructed; the current transformer error relationship model is expressed as: Where k represents the total number of lines, N i represents the transformation ratio of the current transformer on the i-th line, i 有效_i represents the effective value of the secondary current of the current transformer on the i-th line, ε i represents the ratio difference of the current transformer on the i-th line, t represents a certain moment, φ i represents the phase angle of the secondary current of the current transformer on the i-th line, Δφ i Represents the angular difference of the current transformer on the i-th line.

3. A current transformer error correction method according to claim 1 or 2, characterized in that: The calculation process of the phase angle relationship between the line currents specifically includes: According to the collected power data, the current phase angle is calculated, and the calculation formula is: Among them, P is the active power of the line, V is the effective value of the line voltage, I is the effective value of the line current, φ I is the current phase angle.

4. A current transformer error correction method according to claim 2, characterized in that: The current transformer error relationship model simplification process specifically includes: When simplifying the model, when the current phase angle is 0°, the angle difference of the current transformer is ignored; when the current phase angle is 90°, the ratio difference of the current transformer is ignored; A threshold is set, and the relationship between the power factor of the line and the threshold is compared. By ignoring the current transformer error of a single line, the constant term in the current transformer error relationship model is compensated, and the simplified current transformer error relationship model is obtained: Wherein, j represents the current transformer error of the jth line which is ignored.

5. A current transformer error correction method according to claim 1 or 2, characterized in that: The removing of abnormal points in the time-sharing error of the current transformer, correcting the time-sharing error of the current transformer after the abnormal points are removed based on a weighted correction algorithm to obtain the current transformer error, and then realizing the online calibration of the current transformer specifically includes: According to the time-sharing error of the current transformer, an average value is calculated as a reference point for a calculation; Taking the reference point as the center, clustering the calculated time-sharing error of the current transformer is performed using a clustering algorithm to remove abnormal points; After the abnormal point is removed, a weighted current transformer error correction algorithm is used to correct the current transformer time-sharing error after the abnormal point is removed to obtain a current transformer error value; The current transformer error value is compared with the regulation standard to achieve current transformer calibration.

6. A current transformer error correction method according to claim 5, characterized in that: The current transformer time-sharing error correction process specifically includes: According to the current size, a weight value is assigned to each current transformer, and the weight value calculation formula is: Among them, W j is the weight of the jth line, S j is the arithmetic sum of the currents in the jth line, S max is the maximum value of the arithmetic sum of the current in the line; According to the weight value, the current transformer error value is calculated, and the calculation formula is: Among them, ε i represents the current transformer error of the i-th line, ε j_i It represents the time-sharing error of the current transformer of the i-th line after clustering when the error of the current transformer of the j-th line is ignored.

7. A current transformer error correction system, characterized in that: include: A model building module, wherein the model building module builds a current transformer error relationship model taking into account current periodicity by comprehensively considering ratio difference, relative difference and current fluctuation according to the substation topology diagram and Kirchhoff's current law; A phase angle calculation module, which calculates the phase angle relationship of the current between the lines based on the series and parallel relationship of the lines and the power factor angle, and provides data support for the current transformer error calculation; A simplified solution module, wherein the simplified solution module selectively ignores local errors through the current phase angle relationship, simplifies the current transformer error relationship model, and uses a particle swarm algorithm to solve the simplified current transformer error relationship model to obtain a current transformer time-sharing error; And, an error correction module, which removes abnormal points in the current ventilation time-sharing error, corrects the current transformer time-sharing error after removing the abnormal points based on a weighted correction algorithm, obtains the current transformer error, and then realizes online calibration of the current transformer.

8. A current transformer error correction system according to claim 7, characterized in that: The model building module also includes: A line relationship unit, wherein the line relationship unit is based on Kirchhoff's current law and the substation topology diagram to construct a current relationship between lines; the current relationship between lines is: the sum of all currents flowing into nodes, all currents flowing out of nodes, and loss current is zero; A transformer transmission unit, wherein the transformer transmission unit constructs a relationship between the current transformer secondary side measurement data and the primary side actual data according to the current transformer ratio difference and the angle difference; wherein the current transformer ratio difference and the angle difference together constitute the current transformer error; And, a model unit, wherein the model unit constructs a current transformer error relationship model taking into account the current periodicity based on the relationship between the line currents, the relationship between the current transformer secondary side measurement data and the primary side actual data, and the current periodicity. The current transformer error relationship model is expressed as: Where k represents the total number of lines, N i represents the transformation ratio of the current transformer on the i-th line, i 有效_i represents the effective value of the secondary current of the current transformer on the i-th line, ε i represents the ratio difference of the current transformer on the i-th line, t represents a certain moment, φ i represents the phase angle of the secondary current of the current transformer on the i-th line, Δφ i Represents the angular difference of the current transformer on the i-th line.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 6 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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