CN113917384B - Output harmonic parameter estimation method for capacitive voltage transformer - Google Patents
Output harmonic parameter estimation method for capacitive voltage transformer Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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Abstract
A method for estimating output harmonic parameters of a capacitive voltage transformer comprises the following steps: sampling output signals of the capacitive voltage transformer under the excitation of a single frequency signal to obtain a plurality of sampling point data; calculating a periodic spectrum function for estimating a harmonic frequency basic value, and solving an optimization problem with the periodic spectrum function as an optimization target to obtain the harmonic frequency basic value; calculating left and right deviation coefficients at the harmonic frequency basic value, and calculating common mode and differential mode components of the left and right deviation coefficients; calculating a fluctuation value estimation coefficient of the harmonic frequency, and estimating the fluctuation value of the harmonic frequency; estimating complex vectors of harmonic frequencies; and obtaining the harmonic transformation ratio of the capacitive voltage transformer according to the complex vector of the single frequency signal and the complex vector of the harmonic frequency. The method can accurately estimate the harmonic parameter output by the capacitive voltage transformer under the excitation of a single frequency input signal, and improves the calculation precision of the harmonic transformation ratio of the capacitive voltage transformer.
Description
Technical Field
The invention relates to the field of capacitance type voltage transformer output harmonic parameter measurement and calculation, in particular to a capacitance type voltage transformer output harmonic parameter estimation method.
Background
The Capacitive Voltage Transformer (CVT) is widely applied to voltage measurement of a neutral point direct-grounding high-voltage system, is the most main secondary signal source for harmonic measurement of a current high-voltage level system, but cannot be applied to the field of harmonic measurement due to clear regulations of current domestic and foreign standards.
Current research is focused on principle analysis of Capacitive Voltage Transformer (CVT) harmonic measurement errors. By establishing a harmonic equivalent circuit, a calculation method of corresponding parameters is provided, theoretical research is carried out on harmonic measurement precision of the Capacitive Voltage Transformer (CVT), and correctness of theoretical research results is verified through a simulation or experimental method. During verification, output signals of the CVT at different frequency inputs need to be accurately obtained, but due to nonlinearity of the CVT itself, the output signal contains multiple harmonic components when the CVT is input at a single frequency, and the frequency of the component corresponding to the frequency of the input signal in the output signal deviates. The prior researches neglect the influence of harmonic components, and the corresponding components in the output signals are not accurately extracted, so that the accuracy of calculating the voltage transmission ratio is not high, and the accuracy of CVT harmonic measurement characteristic analysis is influenced.
Disclosure of Invention
The invention aims to provide a method for estimating harmonic parameters output by a capacitive voltage transformer, which is used for accurately estimating the harmonic parameters output by the capacitive voltage transformer under the excitation of a single frequency input signal.
The technical scheme of the invention is as follows:
A method for estimating output harmonic parameters of a capacitive voltage transformer comprises the following steps: sampling output signals of the capacitive voltage transformer under the excitation of a single frequency signal to obtain a plurality of sampling point data; calculating a periodic spectrum function for estimating a harmonic frequency basic value, and solving an optimization problem with the periodic spectrum function as an optimization target to obtain the harmonic frequency basic value; calculating left and right deviation coefficients at the harmonic frequency basic value, and calculating common mode and differential mode components of the left and right deviation coefficients; calculating a fluctuation value estimation coefficient of the harmonic frequency, and estimating the fluctuation value of the harmonic frequency; estimating complex vectors of harmonic frequencies; and obtaining the harmonic transformation ratio of the capacitive voltage transformer according to the complex vector of the single frequency signal and the complex vector of the harmonic frequency.
Preferably, the method for obtaining the output signal sampling point data is as follows: let the output signal v out (t) of the capacitive voltage transformer under the excitation of the single frequency signal be:
Wherein V n is the amplitude of the nth harmonic in the output signal, f n is the frequency of the nth harmonic in the output signal, θ n is the phase angle of the nth harmonic in the output signal, and N is the maximum harmonic number to be considered; ψ (t) -N (0, σ 2) are measured Gaussian white noise, σ 2 are noise variance;
sampling the output signal at a sampling frequency f w to obtain M pieces of sampling point data, wherein the sampling point data are as follows:
wherein,
Preferably, the harmonic frequency f 1 can be decomposed into:
f1＝ξ1+ζ1 (4)
wherein ζ 1 is the basic value of the harmonic frequency f 1, ζ 1 is the fluctuation value of the harmonic frequency f 1;
the periodic spectrum function used to estimate ζ 1 is calculated as:
Maximum optimization solution periodic spectrum function, obtain ζ 1:
ξ1＝arg max A(x)x＝0,1,...,M-1 (6)
calculating a left-right deviation coefficient:
wherein λ is a constant, adjustable within a range of (0, 1);
The common mode component Q com and the differential mode component Q diff of the left-right deviation coefficient are calculated:
Qdiff＝Qleft-Qright (9)
Qcom＝Qleft+Qright (10)
Calculating a fluctuation value estimation coefficient of the harmonic frequency:
estimating a fluctuation value of the harmonic frequency:
complex vector of estimated harmonic frequency f 1:
calculating the harmonic transformation ratio of the capacitive voltage transformer:
In the method, in the process of the invention, Is a complex vector for inputting a single frequency signal.
The beneficial effects of the invention are as follows:
1. The method can effectively avoid the output signal frequency fluctuation caused by the nonlinearity of the capacitive voltage transformer, effectively avoid the influence of other harmonic components, effectively cope with measurement noise, improve the precision of CVT harmonic transformation ratio calculation, and has simple calculation and good practical application value.
Drawings
Fig. 1 is a flowchart of a method for estimating output harmonic parameters of a capacitive voltage transformer according to the present invention.
Detailed Description
The present invention is described in the following embodiments in conjunction with the accompanying drawings to assist those skilled in the art in understanding and implementing the invention. The following examples and technical terms therein should not be construed to depart from the technical knowledge of the art unless otherwise indicated.
Let the output signal v out (t) of the capacitive voltage transformer under the excitation of the single frequency signal be:
Wherein V n is the amplitude of the nth harmonic in the output signal, f n is the frequency of the nth harmonic in the output signal, θ n is the phase angle of the nth harmonic in the output signal, and N is the maximum harmonic number to be considered; ψ (t) -N (0, σ 2) are measured Gaussian white noise, σ 2 are noise variances.
Sampling the output signal at a sampling frequency f w to obtain M pieces of sampling point data, wherein the sampling point data are as follows:
further, it is possible to obtain:
Wherein: j is the imaginary sign of the complex number;
the harmonic frequency f 1 can be decomposed into:
f1＝ξ1+ζ1 (4)
where ζ 1 and ζ 1 are the fundamental value and the ripple value of the harmonic frequency f 1, respectively.
Step (1): the periodic spectrum function used to estimate ζ 1 is calculated as:
Step (2): solving the following optimization problem by adopting a mature optimization method to obtain xi 1:
ξ1＝arg max A(x)x＝0,1,...,M-1 (6)
step (3): calculating a left-right deviation coefficient:
wherein λ is a constant, adjustable within a range of (0, 1);
Step (4): calculating a common mode component and a differential mode component of the deviation coefficient:
Qdiff＝Qleft-Qright (9)
Qcom＝Qleft+Qright (10)
step (5): calculating a fluctuation value estimation coefficient of the harmonic frequency:
Step (6): estimating a fluctuation value of the harmonic frequency:
step (7): complex vector of estimated harmonic frequency f 1:
step (8): calculating the harmonic transformation ratio of the capacitive voltage transformer:
In the method, in the process of the invention, Is a complex vector for inputting a single frequency signal.
It can be seen that the method can effectively avoid output signal frequency fluctuation caused by nonlinearity of the capacitive voltage transformer, effectively avoid the influence of other harmonic components, effectively cope with measurement noise, improve the accuracy of harmonic transformation ratio calculation of the capacitive voltage transformer, and has simple calculation and good practical application value.
The invention is described in detail above with reference to the drawings and examples. It should be understood that the description of all possible embodiments is not intended to be exhaustive or to limit the inventive concepts disclosed herein to the precise form disclosed. The technical characteristics of the above embodiments are selected and combined, specific parameters are experimentally changed by those skilled in the art, or the technical means disclosed in the present invention are conventionally replaced by the prior art in the technical field, which is not paid with creative work, and all the specific embodiments are implicitly disclosed in the present invention.
Claims (1)
1. The method for estimating the output harmonic parameters of the capacitive voltage transformer is characterized by comprising the following steps of: sampling output signals of the capacitive voltage transformer under the excitation of a single frequency signal to obtain a plurality of sampling point data; calculating a periodic spectrum function for estimating a harmonic frequency basic value, and solving an optimization problem with the periodic spectrum function as an optimization target to obtain the harmonic frequency basic value; calculating left and right deviation coefficients at the harmonic frequency basic value, and calculating common mode and differential mode components of the left and right deviation coefficients; calculating a fluctuation value estimation coefficient of the harmonic frequency, and estimating the fluctuation value of the harmonic frequency; estimating complex vectors of harmonic frequencies; obtaining the harmonic transformation ratio of the capacitive voltage transformer according to the complex vector of the single frequency signal and the complex vector of the harmonic frequency;
The method for obtaining the output signal sampling point data comprises the following steps: let the output signal v out (t) of the capacitive voltage transformer under the excitation of the single frequency signal be:
Wherein V n is the amplitude of the nth harmonic in the output signal, f n is the frequency of the nth harmonic in the output signal, θ n is the phase angle of the nth harmonic in the output signal, and N is the maximum harmonic number to be considered; ψ (t) -N (0, σ 2) are measured Gaussian white noise, σ 2 are noise variance;
sampling the output signal at a sampling frequency f w to obtain M pieces of sampling point data, wherein the sampling point data are as follows:
wherein,
The harmonic frequency f 1 can be decomposed into:
f1＝ξ1+ζ1
wherein ζ 1 is the basic value of the harmonic frequency f 1, ζ 1 is the fluctuation value of the harmonic frequency f 1;
the periodic spectrum function used to estimate ζ 1 is calculated as:
Maximum optimization solution periodic spectrum function, obtain ζ 1:
ξ1＝arg max A(x)x＝0,1,...,M-1
calculating a left-right deviation coefficient:
wherein λ is a constant, adjustable within a range of (0, 1);
The common mode component Q com and the differential mode component Q diff of the left-right deviation coefficient are calculated:
Qdiff＝Qleft-Qright
Qcom＝Qleft+Qright
Calculating a fluctuation value estimation coefficient of the harmonic frequency:
estimating a fluctuation value of the harmonic frequency:
complex vector of estimated harmonic frequency f 1:
calculating the harmonic transformation ratio of the capacitive voltage transformer:
In the method, in the process of the invention, Is a complex vector for inputting a single frequency signal.
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Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109239638A (en) * | 2018-08-17 | 2019-01-18 | 国网江苏省电力有限公司盐城供电分公司 | Capacitance type potential transformer harmonic error measures correcting device |
| CN109470920A (en) * | 2018-12-19 | 2019-03-15 | 广东工业大学 | A kind of measurement method, system and the device of CVT harmonic voltage |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JPH10246740A (en) * | 1997-03-04 | 1998-09-14 | Shikoku Electric Power Co Inc | Method and device for measuring harmonic by capacitor type potential transformer |
| GB0010720D0 (en) * | 2000-05-03 | 2000-06-28 | Ghassemi Foroozan | Power quality sensors for conventional capacitor coupled voltage transformers |
| CN112305485B (en) * | 2020-09-16 | 2022-07-19 | 国网河北省电力有限公司电力科学研究院 | Method and device for correcting harmonic voltage measurement error of capacitor voltage transformer |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN109239638A (en) * | 2018-08-17 | 2019-01-18 | 国网江苏省电力有限公司盐城供电分公司 | Capacitance type potential transformer harmonic error measures correcting device |
| CN109470920A (en) * | 2018-12-19 | 2019-03-15 | 广东工业大学 | A kind of measurement method, system and the device of CVT harmonic voltage |
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