CN113326476A - Voltage sag type calculation method based on mixed criterion - Google Patents

Voltage sag type calculation method based on mixed criterion Download PDF

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CN113326476A
CN113326476A CN202110780407.0A CN202110780407A CN113326476A CN 113326476 A CN113326476 A CN 113326476A CN 202110780407 A CN202110780407 A CN 202110780407A CN 113326476 A CN113326476 A CN 113326476A
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杜培
林焱
赵耀
林芳
黄霆
张伟骏
方晓玲
汪颖
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Electric Power Research Institute of State Grid Fujian Electric Power Co Ltd
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Abstract

The invention provides a voltage sag type calculation method based on mixed criteria, which comprises the following steps: establishing a voltage sag type mode library according to the type of the voltage sag and the type conversion characteristic of the voltage sag transmitted by the transformer; constructing a voltage sag type mode library in a six-dimensional vector form; establishing a correlation coefficient matrix of each element in the voltage sag type pattern library in the form of the voltage sag to be calculated and a six-dimensional vector by applying a Pearson correlation coefficient, and measuring and calculating the similarity between the voltage to be matched and each characteristic voltage in the voltage sag type pattern library in the form of the six-dimensional vector; calculating a distance matrix of each vector in a voltage sag type mode library in a voltage sag and six-dimensional vector form to be calculated based on the Chebyshev distance; and constructing a voltage sag type correlation matrix, calculating the maximum correlation, and calculating the voltage sag type according to the maximum correlation. The invention can overcome the defect that the traditional method is sensitive to shallow sag and phase jump.

Description

Voltage sag type calculation method based on mixed criterion
Technical Field
The invention relates to the technical field of power quality judgment, in particular to a voltage sag type calculation method based on mixed criteria.
Background
With the rapid development of high and new technologies, high-end manufacturing industries largely adopt precise devices such as programmable controllers, alternating current contactors and the like, and are very sensitive to voltage sag. The precision equipment causes huge economic loss of users due to the phenomena of voltage sag failure, error reporting, jump stopping and the like, the users complain about the serious problems, and the problem of voltage sag treatment becomes a hot point concerned by the industry and academia. The voltage sag type of the specific access point is the key for making the governance decision of the power grid side and the user side.
Currently, various voltage sag type calculation methods are proposed in the industry and academia. However, when the existing algorithm is applied to sag data with large phase jump or high amplitude, the calculation error rate is high, and three-phase voltage vectors are used as input values. The six-phase method (SPA) and the symmetric component method (SCA) are the first proposed algorithms with simple calculation, but the calculation results of the shallow sag and the large phase jump sag are not ideal. The TP-TA method and the TPA method are sensitive to threshold values, and the criterion formula is various. The F-V method is simple in flow, but is sensitive to large phase jump. The RMS method takes a three-phase voltage effective value as an input value, calculates a sag type (A-G type), and the SVA method takes a voltage waveform as an input quantity, and the calculation result adds H and I class sag, so that the classification is more reasonable, but the problem of large phase jump influence is still not solved. In order to improve the type calculation accuracy and improve the adaptability of the classification algorithm, the sensitivity of the calculation method to the sag amplitude and the phase jump is overcome.
Grid faults are the most prominent cause of voltage sag. In the operation process of the power system, the power grid faults can be caused by weather, branch overlapping lines and other reasons. When a fault occurs, the system draws a large current, and according to the line voltage division principle, the voltage near the fault can be greatly reduced to generate voltage sag; after the fault is cleared, the voltage of the nearby area is recovered to be normal. The three-phase short-circuit fault is the most serious short-circuit fault, so that the three-phase voltage amplitude falls to be basically the same; the phase-to-phase short circuit fault can cause the voltage drop of the two phases with the fault, and the amplitude of the voltage of the non-fault phase is basically unchanged; the two-phase grounding short circuit fault causes the fault phase voltage to be reduced, the non-fault phase voltage is unchanged or increased, and the change condition of the non-fault phase voltage mainly depends on the system grounding mode; the fault phase voltage of the single-phase fault is reduced, and the change condition of the non-fault phase voltage is related to factors such as system grounding and the like.
The voltage sag type is defined according to the variation of the three-phase voltage amplitude and phase. Assuming that the power source electromotive force per unit value before the sag is 1p.u., 9 types of voltage sag/sag are shown in fig. 1, in which a dotted line represents a voltage vector before the sag, and a solid line represents a voltage vector during the sag. The ramp-up is a phenomenon that occurs with a ramp-down under system-specific grounding conditions, and is generally described in a unified manner as a-I type.
The transformer has a plurality of connection modes, voltage is spread from a high-voltage side to a low-voltage side, and the sag types can be changed due to different connection modes. According to the effect of the sag type change, the transformers can be classified into three categories: class I (YNyn), class II (Yy, Dd, Dz) and class III (Yd, Dy, Yz). And describing the sag type change characteristics caused by the transformer coupling mode by using a transfer matrix, as shown in formulas (1) to (3).
(1) Class I: the transmission of phase voltage and line voltage is not changed by the transformer, and the transmission matrix is an identity matrix E, as shown in formula (1).
Figure BDA0003157021700000021
(2) Class II: the transformer does not transmit zero sequence voltage, and a transmission matrix is as shown in a formula (2).
Figure BDA0003157021700000022
(3) Class III: the method is equivalent to the conversion of phase voltage to line voltage, the converted voltage does not contain zero sequence component, and phase change can occur, and the transmission matrix is as shown in formula (3).
Figure BDA0003157021700000023
The different types of voltage sags are propagated through different types of transformers, and the change rule of the sag types is shown in fig. 2 and table 1.
TABLE 1 propagation law of voltage sag types
Figure BDA0003157021700000024
Figure BDA0003157021700000031
Disclosure of Invention
In view of this, the present invention provides a voltage sag type calculation method based on a hybrid criterion, which has high accuracy and can overcome the defect that the conventional method is sensitive to shallow sag and phase jump.
The invention is realized by adopting the following scheme: a voltage sag type calculation method based on mixed criteria specifically comprises the following steps:
establishing a voltage sag type mode library according to the type of the voltage sag and the type conversion characteristic of the voltage sag transmitted by the transformer;
extracting the real part and the imaginary part of the three-phase voltage to form a voltage sag type mode library in a six-dimensional vector form;
establishing a correlation coefficient matrix of each element in the voltage sag type pattern library in the form of the voltage sag to be calculated and a six-dimensional vector by applying a Pearson correlation coefficient, and measuring and calculating the similarity between the voltage to be matched and each characteristic voltage in the voltage sag type pattern library in the form of the six-dimensional vector;
calculating a distance matrix of each vector in a voltage sag type mode library in a voltage sag and six-dimensional vector form to be calculated based on the Chebyshev distance;
and constructing a voltage sag type correlation matrix, defining a correlation index, calculating the maximum correlation, and calculating the voltage sag type according to the maximum correlation.
Further, the establishing, by applying the pearson correlation coefficient, a correlation coefficient matrix of each element in the voltage sag pattern library in the form of the voltage sag to be calculated and the six-dimensional vector, and respectively measuring and calculating the similarity between the voltage to be matched and each characteristic voltage in the voltage sag pattern library in the form of the six-dimensional vector is specifically:
representing a certain element in the six-dimensional vector form voltage sag type pattern library as:
Figure BDA0003157021700000041
in the formula, Vs1、Vs3、Vs5Three-phase voltage real part, V, representing any sag data s in the pattern librarys2、Vs4、Vs6Representing the corresponding imaginary three-phase voltage components;
a certain measured voltage sag vector
Figure BDA0003157021700000042
Expressed as:
Figure BDA0003157021700000043
in the formula, Vm1、Vm3、Vm5Three-phase power for representing the measured voltage sag data mCompacted part, Vm2、Vm4、Vm6Representing the corresponding imaginary three-phase voltage components;
the measured voltage sag vector
Figure BDA0003157021700000044
The correlation coefficient with the certain element is:
Figure BDA0003157021700000045
in the formula,
Figure BDA0003157021700000046
and
Figure BDA0003157021700000047
respectively the average values of the two groups of vectors;
the correlation coefficient matrix of the voltage to be measured and the pattern library is obtained by calculation by adopting the method as follows:
Figure BDA0003157021700000048
in which the subscript X of the matrix of correlation coefficients represents the different dip types, pX-i-jRepresenting the correlation between the voltage sag to be calculated and the voltage sag with amplitude and phase jump in the X-type mode library; the larger the correlation coefficient is, the stronger the correlation is, which indicates that the similarity between the corresponding voltage vector to be calculated and the corresponding vector in the pattern library is larger.
Further, the step of calculating the distance matrix of each vector in the voltage sag type pattern library to be calculated based on the chebyshev distance and in the six-dimensional vector form is specifically as follows:
certain vector in voltage sag type pattern library in six-dimensional vector form
Figure BDA0003157021700000051
And a measured voltage
Figure BDA0003157021700000052
Chebyshev distance of
Figure BDA0003157021700000053
Is defined as follows:
Figure BDA0003157021700000054
wherein k represents 1,2,3., ∞;
for the sag type X, the chebyshev distance matrix of the voltage sag to be calculated and each vector of the pattern library is:
Figure BDA0003157021700000055
in the formula, mX-i-jRepresenting the voltage sag to be calculated and the magnitude of | V in the X-type pattern libraryiIn phase of
Figure BDA0003157021700000056
The chebyshev distance of the voltage sag.
Further, the constructing a voltage sag type correlation matrix, defining a correlation index, calculating a maximum correlation, and calculating a voltage sag type according to the maximum correlation specifically includes:
for sag type X, a sag type correlation matrix K is definedX，KXEach element in (1) is equal to the correlation coefficient matrix PXMatrix M of elements and distancesXThe value obtained by dividing the corresponding element in (1) is as follows:
Figure BDA0003157021700000057
wherein,
Figure BDA0003157021700000058
in the formula, kX-i-jRepresenting the sag to be calculated and the amplitude of | V in the X-type mode libraryiI, phase jump to
Figure BDA0003157021700000061
The correlation of voltage sag of; the larger the correlation coefficient rho is, the smaller the Chebyshev distance m is, the larger the correlation degree is, and the higher the matching degree of the sag to be calculated and a certain vector is.
Calculating the sag and K to be calculatedXMaximum correlation of each element in the matrix:
kX-max＝max(KX)；
the maximum correlation degree of each sag type is obtained, and the maximum value k in the maximum correlation degrees of all types is selectedmaxAnd according to kmaxThe associated dip type is matched.
The invention also provides a voltage sag type calculation system based on a hybrid criterion, comprising a memory, a processor and computer program instructions stored on the memory and executable by the processor, which when executed by the processor, are capable of implementing the method steps as described above.
The present invention also provides a computer readable storage medium having stored thereon computer program instructions executable by a processor, the computer program instructions when executed by the processor being capable of performing the method steps as described above.
Compared with the prior art, the invention has the following beneficial effects: according to the invention, through simulation data and actual measurement data verification, for the actual measurement data, the algorithm can accurately calculate the sag type, and a basis is provided for analyzing the influence of sag events on sensitive equipment. Meanwhile, based on the constructed type mode library, the method can realize millisecond-level rapid calculation, is suitable for being applied to a voltage sag monitoring system or a terminal, calculates sag type real-time information, and has a high application value.
Drawings
Fig. 1 shows 9 types of voltage sag/ramp according to an embodiment of the present invention.
Fig. 2 shows a voltage sag pattern transformation law of the transformer according to the embodiment of the present invention.
FIG. 3 is a flow chart of a method according to an embodiment of the present invention.
Fig. 4 is an IEEE14 node test system according to an embodiment of the present invention.
FIG. 5 shows an exemplary simulated voltage sag effective value. Wherein, (a) is a curve of the effective value of the sag 1 changing with time, (b) is a curve of the effective value of the sag 2 changing with time, and (c) is a curve of the effective value of the sag 3 changing with time.
FIG. 6 is a schematic diagram of a simulation data voltage vector according to an embodiment of the present invention.
FIG. 7 is a schematic diagram of a measured data voltage vector according to an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, 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 application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
As shown in fig. 3, the present embodiment provides a voltage sag type calculation method based on a hybrid criterion, which specifically includes the following steps:
establishing a voltage sag type mode library according to the type of the voltage sag and the type conversion characteristic of the voltage sag transmitted by the transformer; the voltage sag type is determined by characteristic voltage V and phase jump values of all phases together, and based on basic definition of all types, a voltage sag database covers 13 ten thousand groups of voltage characteristics.
Extracting the real part and the imaginary part of the three-phase voltage to form a voltage sag type mode library in a six-dimensional vector form;
establishing a correlation coefficient matrix of each element in the voltage sag type pattern library in the form of the voltage sag to be calculated and a six-dimensional vector by applying a Pearson correlation coefficient, and measuring and calculating the similarity between the voltage to be matched and each characteristic voltage in the voltage sag type pattern library in the form of the six-dimensional vector;
calculating a distance matrix of each vector in a voltage sag type mode library in a voltage sag and six-dimensional vector form to be calculated based on the Chebyshev distance;
and constructing a voltage sag type correlation matrix, defining a correlation index, calculating the maximum correlation, and calculating the voltage sag type according to the maximum correlation.
Preferably, in order to accurately identify the voltage sag type, the three-phase amplitude and the phase jump value are respectively calculated to form a 6-dimensional vector. Wherein F, G type is a distorted version of C, D type; most users access the power grid in a triangular connection mode, so the B, E class sag is generally not propagated to the user side. Therefore, A, C, D, H, I type is the target for performing type calculation.
(1) Characteristic voltage V
The characteristic voltage V is a single-time characteristic of voltage sag proposed by IEEE 1564-. Unlike the definition of the residual voltage, the characteristic voltage V is expressed in terms of the lowest value of the six-phase voltage. The six-phase voltage includes a three-phase step-down voltage and a three-phase line voltage. V0And (t) is a curve of the change of the zero sequence voltage along with time, and can be obtained by the formula (4).
Figure BDA0003157021700000081
Wherein Va(t)、Vb(t)、VcRespectively, the curves of the three-phase voltage change along with the time. Defining the voltage reduction as the phase voltage minus the zero sequence voltage, and obtaining three-phase voltage reduction as follows:
Figure BDA0003157021700000082
in order to keep the magnitude of the three-phase line voltage consistent with the three-phase drop voltage, the three-phase line voltage is made as follows:
Figure BDA0003157021700000083
in (5) and (6), six-phase voltages are shared, wherein the lowest one-phase voltage is the characteristic voltage V (t), and the characteristic voltage V of the event is represented in a vector form. Defining positive and negative sequence factors F, V and F can delineate the voltage sag type. With C in FIG. 1aFor example, the type sag is expressed as:
Figure BDA0003157021700000084
in various short circuit conditions, the positive and negative sequence factors F are almost close to 1; a sag caused by motor start-up may result in F as low as 0.7. Considering the sag type calculation problem caused by different short-circuit faults, the value of F in all types of expressions is set to be 1.
To fully describe all possible voltage sags, a characteristic voltage V is constructed. The sag amplitudes ranged from 0.01 to 1, with 100 different amplitudes set at equal intervals. The phase jump range does not have to take into account the full range of-180 deg. to +180 deg.. When the system X/R impedance ratio is 10 and the feeder impedance ratio X/R is 0.5, the impedance angle has a maximum negative value, approximately-60 °. If the X/R of the system and the feeder are nearly equal, then the impedance angle has a minimum positive value of about 10. Thus, in most cases, the actual impedance angle is between-60 ° and +10 °. For the above reasons, 100 different phases are set, and considering a phase margin of 20 °, ranging from-80 ° to +30 °, step interval is 110 °/100, and the amplitudes and phases are combined one by one to obtain 100 × 100 characteristic voltages of different amplitudes and phases, and a composition model of V is shown below.
Figure BDA0003157021700000091
Figure BDA0003157021700000092
Figure BDA0003157021700000093
Where i and j are numbers of the respective groups, and equations (9) and (10) represent the amplitude and phase of the characteristic voltage.
(2) Type schema library
Type voltage sag data is generated A, C, D, H, I to build a library of type patterns. Wherein the class A sag is a three-phase sag; the last four types are asymmetric dip, and each type of dip can generate data by taking phases a, b and c as characteristic phases respectively. And substituting the characteristic voltage into an A, C, D, H, I type voltage sag expression in the graph 1 based on the characteristic voltage constructed in the previous step to generate voltage sag data and construct a type pattern library. Wherein, type A is a class dip, C, D, H, I can construct 12 classes of dip by respectively using a, b and c three phases as characteristic phases, and 13 x 10000 groups of voltage dip data are formed. As shown in equation (11), the real part and imaginary part of each dip data are extracted to form a set of 6-dimensional vectors.
Figure BDA0003157021700000094
In the formula Vs1、Vs3、Vs5Representing the real part, Vs2、Vs4、Vs6Representing the imaginary part. For each type of dip, 100 x 100 sets of 6-dimensional vectors may be formed. In type DaFor example, each element in equation (12) represents a 6-dimensional vector of sag data, such as VDa-1-2That is, the characteristic voltage V formed at an amplitude of 0.01p.u. and a phase of-78.89 DEG is substituted into D in FIG. 1aAnd (4) obtaining a 6-dimensional vector formed by the real part and the imaginary part of each phase voltage of the three-phase voltage by using a quasi-sag formula.
Figure BDA0003157021700000101
The 13 types of voltage sag data form 13 ten thousand groups of 6-dimensional vectors to form a voltage sag type mode library.
In this embodiment, the type of a certain voltage sag data is identified, a 6-dimensional feature of the certain voltage sag data can be extracted to form a 6-dimensional vector as shown in formula (11), and the similarity between the 6-dimensional vector of the certain voltage sag data and each vector in the pattern library is compared to determine the type of the certain voltage sag data. The invention provides a double criterion based on a Pearson correlation coefficient and a Chebyshev distance, measures the similarity between voltage sag data to be identified and each sag data in a mode library, defines a maximum correlation index and calculates the voltage sag type.
The Pearson correlation coefficient is used for measuring the degree of correlation between two variables, and the larger the correlation coefficient is, the stronger the correlation between the two variables is, otherwise, the weaker the correlation is. The Pearson correlation coefficient is used for measuring the degree of correlation between two variables, and the larger the correlation coefficient is, the stronger the correlation between the two variables is, and otherwise, the weaker the correlation is.
Figure BDA0003157021700000102
Wherein,
Figure BDA0003157021700000103
and
Figure BDA0003157021700000104
respectively, the mean of the variable X, Y.
In this embodiment, the establishing, by using the pearson correlation coefficient, a correlation coefficient matrix of each element in the voltage sag pattern library to be calculated and in the six-dimensional vector form, and respectively measuring and calculating the similarity between the voltage to be matched and each feature voltage in the voltage sag pattern library in the six-dimensional vector form specifically includes:
representing a certain element in the six-dimensional vector form voltage sag type pattern library as:
Figure BDA0003157021700000105
in the formula, Vs1、Vs3、Vs5Three-phase voltage real part, V, representing any sag data s in the pattern librarys2、Vs4、Vs6Representing the corresponding imaginary three-phase voltage components;
a certain measured voltage sag vector
Figure BDA0003157021700000106
Expressed as:
Figure BDA0003157021700000111
in the formula, Vm1、Vm3、Vm5Three-phase voltage real part, V, representing the measured voltage sag data mm2、Vm4、Vm6Representing the corresponding imaginary three-phase voltage components;
the measured voltage sag vector
Figure BDA0003157021700000112
The correlation coefficient with the certain element is:
Figure BDA0003157021700000113
in the formula,
Figure BDA0003157021700000114
and
Figure BDA0003157021700000115
respectively the average values of the two groups of vectors;
the correlation coefficient matrix of the voltage to be measured and the pattern library is obtained by calculation by adopting the method as follows:
Figure BDA0003157021700000116
in the formula, the subscript X of the matrix of correlation coefficients represents a different sag type, i.e., A, Ca、Cb、Cc、Da、Db、Dc、Ha、Hb、Hc、Ia、Ib、IcType (b). RhoX-i-jRepresenting the voltage sag to be calculated and the magnitude of | V in the X-type pattern libraryiI, phase jump to
Figure BDA0003157021700000117
The voltage sag dependency of; the larger the correlation coefficient is, the greater the similarity between the corresponding voltage vector to be calculated and the corresponding vector in the pattern library is.
In addition, the Chebyshev distance is used for measuring the similarity degree of the two samples, and the larger the measurement result is, the more dissimilar the two samples are; the smaller the distance, the opposite is true. In this embodiment, the calculating a distance matrix of each vector in the voltage sag type pattern library to be calculated based on the chebyshev distance and in the six-dimensional vector form specifically includes:
certain vector in voltage sag type pattern library in six-dimensional vector form
Figure BDA0003157021700000118
And a measured voltage
Figure BDA0003157021700000119
Chebyshev distance of
Figure BDA00031570217000001110
Is defined as follows:
Figure BDA0003157021700000121
wherein k represents 1,2,3., ∞;
for the sag type X, the chebyshev distance matrix of the voltage sag to be calculated and each vector of the pattern library is:
Figure BDA0003157021700000122
in the formula, mX-i-jRepresenting the voltage sag to be calculated and the magnitude of | V in the X-type pattern libraryiIn phase of
Figure BDA0003157021700000123
The chebyshev distance of the voltage sag; e.g. mX-100-3The chebyshev distance representing the voltage sag to be calculated versus the voltage sag of amplitude 1 and phase-78 deg. in the X-type pattern library.
The larger the Chebyshev distance is, the smaller the similarity between the corresponding voltage vector to be calculated and the corresponding vector in the pattern library is.
Using the correlation coefficient matrix P obtained aboveXAnd Chebyshev distance matrix MXThe correlation index can be defined as the correlation coefficient divided by the corresponding Chebyshev distance, and has the advantages of reducing the uncertainty caused by a single criterion and improving the calculation accuracy. In this embodiment, the constructing a voltage sag type correlation matrix, defining a correlation index, calculating a maximum correlation, and calculating a voltage sag type according to the maximum correlation specifically includes:
for sag type X, a sag type correlation matrix K is definedX，KXEach element in (1) is equal to the correlation coefficient matrix PXMatrix M of elements and distancesXThe value obtained by dividing the corresponding element in (1) is as follows:
Figure BDA0003157021700000124
wherein,
Figure BDA0003157021700000131
in the formula, kX-i-jRepresenting the sag to be calculated and the amplitude of | V in the X-type mode libraryiI, phase jump to
Figure BDA0003157021700000132
The correlation of voltage sag of; e.g. kX-100-3Representing the correlation of the sag to be calculated with the voltage sag of amplitude 1 and phase jump to-78 deg. in the X-type pattern library. The larger the correlation coefficient rho is, the smaller the Chebyshev distance m is, the larger the correlation degree is, and the higher the matching degree of the sag to be calculated and a certain vector is.
Calculating the sag and K to be calculatedXMaximum correlation of each element in the matrix:
kX-max＝max(KX)；
the maximum correlation degree of each sag type is obtained, and the maximum value k in the maximum correlation degrees of all types is selectedmaxAnd according to kmaxThe associated dip type is matched. Applying the obtained k of each sag type to the rest sag typesX-maxIs denoted by kA，kCa,...,kIcA total of 13, the maximum of these 13 correlations is extracted.
kmax＝max(kA,kBa,kBb,...,kIc) (23)
The correlation dip type is matched according to the maximum value among the 13 correlation degrees, and the matching result is as shown in table 2 below.
TABLE 2 Voltage sag type matching results
Figure BDA0003157021700000133
The present embodiment also provides a voltage sag type calculation system based on a hybrid criterion, comprising a memory, a processor and computer program instructions stored on the memory and executable by the processor, which when executed by the processor, are capable of implementing the method steps as described above.
The present embodiments also provide a computer readable storage medium having stored thereon computer program instructions executable by a processor, the computer program instructions, when executed by the processor, being capable of performing the method steps as described above.
Next, the present embodiment performs a simulation experiment to further illustrate the effectiveness of the proposed method.
First, the experimental data are described in this example as follows:
(1) the simulation data 1.
According to the simulation of the voltage sag of the known type, a plurality of sag data are constructed, in order to avoid the simulation data from being repeated with the pattern library data, the amplitude and the phase of the characteristic voltage are adjusted to [0.1,0.9] and [ -40,10], the sample number is 50 × 50, 2500 groups of simulation data are formed, and meanwhile, the conditions that F is 1, F is 0.9 and F is 0.8 are respectively taken to be considered in consideration of the change of the standard voltage, and the verification is carried out. The result shows that the algorithm has higher accuracy.
Table 3 simulation data 1 voltage sag type calculation results
Figure BDA0003157021700000141
In order to verify the effect of the proposed mixing criterion, the voltage sag type calculation is performed under a single criterion that only the pearson correlation coefficient is considered and only the chebyshev distance is considered. For the former, in the correlation coefficient matrix, the correlation coefficient of the measured voltage sag data and a certain sag type is the largest, and the voltage sag is the corresponding type. For the latter, in the chebyshev distance matrix, the measured voltage sag data has the smallest chebyshev distance with a certain sag type, and the voltage sag is the corresponding type.
The calculation results are shown in table 3, and when the positive and negative sequence factor F is the standard voltage 1, the accuracy of the proposed method is 100% for all simulation data. When the positive and negative sequence factors F are not 0.9 and 0.8 of the standard voltage, the method still has higher identification accuracy rate, and the accuracy rate is higher than 95%. Considering F ═ 1 and 0.9, the accuracy of the voltage sag type calculation results is about 75% or 80% with only pearson correlation coefficients or chebyshev distances as criteria, far below the calculation effect of the mixing criteria.
(2) The simulation data 2.
An IEEE14 node network (as shown in figure 4) is built on a PSCAD/EMTDC platform, two different types of voltage sag are set, a two-phase fault and a three-phase fault are set between a No. 4 bus and a No. 9 bus, the fault 1 is an A, B two-phase grounding short-circuit fault which occurs between lines 4-9, the starting moment of the fault is 1s, and the clearing moment of the fault is 4 s; the fault 2 is a three-phase grounding short circuit fault occurring between lines 4-9, the starting time is 5.6s, and the fault clearing time is 6.8 s; fault 3 is an A, C two-phase ground fault occurring between lines 4-9, with a start time of 8.6s and an end time of 10 s. The three dip waveform effective values are shown in fig. 5. Knowing the specific type of fault, it can be inferred that the type of sag monitored is CcClass, class A and class IbAnd (4) class.
The three-phase amplitude and phase are shown in fig. 6:
the monitoring data of fig. 5 were classified using the proposed method and the maximum correlation was calculated, and the results are listed in table 4. According to the calculation results, the most relevant dip types of the dip 1, the dip 2 and the dip 3 are respectively CcClass A, class IbAnd (4) class. The calculation result is consistent with the actual result, and the effectiveness of the method is proved.
TABLE 4 simulation data maximum correlation calculation results
Figure BDA0003157021700000151
Next, the present embodiment verifies the measured data.
4 sag events in 2019 years in the Fuzhou commercial power quality monitoring system are selected for analysis, and the method is verified. And (4) performing calculation on a MATLAB/Simulink platform, wherein the calculation time of each time is not more than 1 s. The amplitude and phase jump values of each phase for 4 dips are calculated, and the vector diagram is shown in fig. 7. By applying the method, the similarity between the 4 groups of actually measured voltage sag data and various sag data of the pattern library is calculated, and the result is shown in table 5.
TABLE 5 maximum correlation calculation of measured data
Data 1 Data 2 Data 3 Data 4
kA 0.937 1.535 2.032 9.788
kCa 0.910 1.928 9.107 3.628
kCb 1.192 1.805 1.355 6.639
kCc 0.916 1.086 1.538 4.283
kDa 1.142 1.203 1.238 6.176
kDb 0.886 1.267 2.952 3.546
kDc 1.006 2.868 2.234 4.589
kHa 0.933 1.115 1.230 3.292
kHb 0.982 1.119 1.299 3.178
kHc 1.463 1.585 1.281 3.229
kIa 1.025 1.214 1.434 3.178
kIb 1.129 1.228 1.486 3.191
kIc 0.879 1.100 1.341 3.268
And finding out the maximum correlation degree of each column according to the calculation result, wherein the corresponding sag type is the calculation result.
For actually measured data, no standard algorithm is available for calculation in a monitoring series at present, and only visual judgment is available for estimating the actual type of the actually measured data and comparing the actual type with a calculation result. Taking data 2 as an example, phase b does not drop below the sag threshold specified by the standard, phase a is almost equal to the threshold, phase a and phase b are considered not to drop, phase c significantly drops to 0.274p.u., and waveform 2 is judged as typical D by visual inspectioncThe calculation result of the method is correct when the voltage is similar to sag. And the data 3 can be similarly judged, the phase a is almost free from falling, the phases b and C fall to 0.682p.u. and 0.513p.u. respectively, the phase b has larger phase jump, and the phase b is judged to be C by visual inspectionaClass sag, the calculation result accords with the visual judgmentAnd (7) breaking.
In order to verify the advancement of the method, the calculation result of the method is compared with the calculation results of several international mainstream classification algorithms. The sag types of data 1 to data 4 were calculated by using the SCA method, SPA method, SVA method and TP-TA method, and the comparison results are shown in Table 6.
TABLE 6 type of voltage sag for measured data
Type of sag Data 1 Data 2 Data 3 Data 4
Visual observation results Hc Dc Ca A
The method mentioned Hc Dc Ca A
SCA method - Dc Ca -
SPA method - Cb Dc -
SVA method Iac Cb Dc A
TP-TA method - Dc Cc -
Since the SCA method, the SPA method, and the TP-TA method do not take into account the voltage sag and the symmetrical-type sag, the actual types of data 1 and 4 are H, respectivelycType-dip and type-a symmetric dip, so the dip type of data 1 and 4 cannot be calculated using these three methods. The sag types of the data 2 are calculated by using the SPA method and the SVA method, and the results are CbType, obvious error; calculate the dip type of data 3, only the SCA method results correctly. The phase jump of data 2 and data 3 is the main cause of errors in the existing method. As can be seen from comparison, the method provided by the patent can effectively overcome misjudgment caused by phase jump and has a good application prospect.
In summary, the present embodiment provides a voltage sag type calculation method based on pearson correlation coefficient and chebyshev distance, which is suitable for rectangular sag caused by power grid fault, for the problems that voltage sag caused by large motor starting and transformer excitation is slow recovery type sag, voltage amplitude is always changed in the sag process, and it is difficult to define the sag by ABC classification. The three-phase voltage containing amplitude and phase information is converted into a six-dimensional vector which is easy to calculate, a 6-dimensional vector mode library is established, the maximum vector correlation degree is calculated, and the voltage sag type is identified. According to the method, simulation data and actual measurement data are verified, and for the actual measurement data, the algorithm can accurately calculate the sag type, so that a basis is provided for analyzing the influence of sag events on sensitive equipment. When the positive and negative sequence factors F are standard voltages, the accuracy of the method is 100% for all simulation data. When the positive and negative sequence factors F are not standard voltages, the method still has high identification accuracy rate, and the accuracy rate is higher than 95%. The method has high accuracy and can overcome the defect that the traditional method is sensitive to shallow sag and phase jump.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may 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, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims (6)

1. A voltage sag type calculation method based on a mixed criterion is characterized by comprising the following steps:
establishing a voltage sag type mode library according to the type of the voltage sag and the type conversion characteristic of the voltage sag transmitted by the transformer;
extracting the real part and the imaginary part of the three-phase voltage to form a voltage sag type mode library in a six-dimensional vector form;
establishing a correlation coefficient matrix of each element in the voltage sag type pattern library in the form of the voltage sag to be calculated and a six-dimensional vector by applying a Pearson correlation coefficient, and measuring and calculating the similarity between the voltage to be matched and each characteristic voltage in the voltage sag type pattern library in the form of the six-dimensional vector;
calculating a distance matrix of each vector in a voltage sag type mode library in a voltage sag and six-dimensional vector form to be calculated based on the Chebyshev distance;
and constructing a voltage sag type correlation matrix, defining a correlation index, calculating the maximum correlation, and calculating the voltage sag type according to the maximum correlation.
2. The voltage sag type calculation method based on the mixing criterion according to claim 1, wherein the Pearson correlation coefficient is applied to establish a correlation coefficient matrix of each element in the voltage sag to be calculated and the voltage sag type pattern library in a six-dimensional vector form, and the similarity between the voltage to be matched and each characteristic voltage in the voltage sag type pattern library in the six-dimensional vector form is measured and calculated respectively as follows:
representing a certain element in the six-dimensional vector form voltage sag type pattern library as:
Figure FDA0003157021690000011
in the formula, Vs1、Vs3、Vs5Three-phase voltage real part, V, representing any sag data s in the pattern librarys2、Vs4、Vs6Representing the corresponding imaginary three-phase voltage components;
a certain measured voltage sag vector
Figure FDA0003157021690000012
Expressed as:
Figure FDA0003157021690000013
in the formula, Vm1、Vm3、Vm5Three-phase voltage real part, V, representing the measured voltage sag data mm2、Vm4、Vm6Representing the corresponding imaginary three-phase voltage components;
the measured voltage sag vector
Figure FDA0003157021690000021
The correlation coefficient with the certain element is:
Figure FDA0003157021690000022
in the formula,
Figure FDA0003157021690000023
and
Figure FDA0003157021690000024
respectively the average values of the two groups of vectors;
the correlation coefficient matrix of the voltage to be measured and the pattern library is obtained by calculation by adopting the method as follows:
Figure FDA0003157021690000025
in which the subscript X of the matrix of correlation coefficients represents the different dip types, pX-i-jRepresenting the voltage sag to be calculated and the magnitude of | V in the X-type pattern libraryiI, phase jump to
Figure FDA0003157021690000026
The voltage sag dependency of; the larger the correlation coefficient is, the stronger the correlation is, which indicates that the similarity between the corresponding voltage vector to be calculated and the corresponding vector in the pattern library is larger.
3. The voltage sag type calculation method based on the mixing criterion according to claim 1, wherein the distance matrix of each vector in the voltage sag type pattern library to be calculated based on the Chebyshev distance calculation and the six-dimensional vector form is specifically:
certain vector in voltage sag type pattern library in six-dimensional vector form
Figure FDA0003157021690000027
And a measured voltage
Figure FDA0003157021690000028
Chebyshev distance of
Figure FDA0003157021690000029
Is defined as follows:
Figure FDA00031570216900000210
wherein k represents 1,2,3., ∞;
for the sag type X, the chebyshev distance matrix of the voltage sag to be calculated and each vector of the pattern library is:
Figure FDA0003157021690000031
in the formula, mX-i-jThe representation represents the voltage sag to be calculated and the magnitude of | V in the X-type pattern libraryiIn phase of
Figure FDA0003157021690000032
The chebyshev distance of the voltage sag.
4. The voltage sag type calculation method based on the mixing criterion according to claim 1, wherein the step of constructing a voltage sag type correlation matrix, defining a correlation index, and calculating the maximum correlation comprises the following steps of:
for sag type X, a sag type correlation matrix K is definedX，KXEach element in (1) is equal to the moment of the correlation coefficientArray PXMatrix M of elements and distancesXThe value obtained by dividing the corresponding element in (1) is as follows:
Figure FDA0003157021690000033
wherein,
Figure FDA0003157021690000034
in the formula, kX-i-jRepresenting the sag to be calculated and the amplitude of | V in the X-type mode libraryiI, phase jump to
Figure FDA0003157021690000035
The correlation of voltage sag of; the larger the correlation coefficient rho is, the smaller the Chebyshev distance m is, the larger the correlation degree is, and the higher the matching degree of the sag to be calculated and a certain vector is;
calculating the sag and K to be calculatedXMaximum correlation of each element in the matrix:
kX-max＝max(KX)；
the maximum correlation degree of each sag type is obtained, and the maximum value k in the maximum correlation degrees of all types is selectedmaxAnd according to kmaxThe associated dip type is matched.
5. A voltage sag type calculation system based on a mixing criterion, comprising a memory, a processor and computer program instructions stored on the memory and executable by the processor, the computer program instructions, when executed by the processor, being capable of implementing the method steps of any one of claims 1 to 4.
6. A computer-readable storage medium, having stored thereon computer program instructions executable by a processor, the computer program instructions, when executed by the processor, being capable of carrying out the method steps according to any one of claims 1 to 4.
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