CN106872777B - Harmonic and inter-harmonic separation analysis method - Google Patents

Harmonic and inter-harmonic separation analysis method Download PDF

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Publication number
CN106872777B
CN106872777B CN201710080072.5A CN201710080072A CN106872777B CN 106872777 B CN106872777 B CN 106872777B CN 201710080072 A CN201710080072 A CN 201710080072A CN 106872777 B CN106872777 B CN 106872777B
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harmonic
signal
inter
quasi
analysis
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CN106872777A (en
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惠锦
董晓峰
李冬
乔杰
褚文杰
张逸
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Suzhou Power Supply Co of State Grid Jiangsu Electric Power Co Ltd
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Suzhou Power Supply Co of State Grid Jiangsu Electric Power Co Ltd
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16Spectrum analysis; Fourier analysis
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/02Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01RMEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R25/00Arrangements for measuring phase angle between a voltage and a current or between voltages or currents

Abstract

The invention relates to a method for separating and analyzing harmonic waves and inter-harmonic waves, which comprises the following steps: sampling an original electric energy signal, dividing different analysis windows, performing windowing calculation on the original electric energy signal in each analysis window to obtain a windowed signal, performing time domain averaging on the windowed signal to obtain a quasi-harmonic signal, and performing discrete Fourier transform on the quasi-harmonic signal to obtain a harmonic parameter; and subtracting the quasi-harmonic signal from the original electric energy signal in the analysis window to obtain a quasi-inter-harmonic signal, sequentially carrying out windowing calculation again on the quasi-inter-harmonic signal, carrying out zero filling and discrete Fourier transform at the end of the sequence of the quasi-inter-harmonic signal to obtain an encrypted spectrum signal, and analyzing the encrypted spectrum signal to obtain an inter-harmonic parameter. The invention can accurately separate the harmonic and inter-harmonic components in a certain power quality signal in the time domain, thereby inhibiting the frequency spectrum interference between the harmonic and inter-harmonic components when analyzing the signal in the frequency domain and improving the detection and analysis precision of the harmonic and inter-harmonic components.

Description

Harmonic and inter-harmonic separation analysis method
Technical Field
The invention belongs to the power industry, and particularly relates to a method for analyzing harmonic and inter-harmonic components in a power signal to obtain parameters such as frequency, amplitude, phase and the like of each harmonic and inter-harmonic component.
Background
Discrete Fourier Transform (DFT) is currently the most common method for analyzing harmonics and inter-harmonics for power quality monitoring devices. However, when the analyzed power quality signal contains inter-harmonic components in addition to harmonics, even if the sampling is synchronous with the fundamental frequency (i.e. the sampling frequency is an integral multiple of the fundamental frequency), the harmonic and inter-harmonic parameters obtained by the analysis still have large errors. The reason is that mutual interference between frequency spectrums exists between harmonics and inter-harmonics, when the content of a certain inter-harmonic component is small, the inter-harmonic component is easily submerged by a leakage component (false component) of the harmonics, so that the inter-harmonic component cannot be detected, and even if the inter-harmonic component can be detected, the calculation error of the parameter is influenced by the leakage of the harmonics and becomes large; similarly, the inter-harmonics may generate leakage at the harmonic frequency points, which affects the analysis accuracy of the harmonics.
Disclosure of Invention
The invention aims to provide a harmonic and inter-harmonic separation analysis method which can accurately separate harmonic and inter-harmonic components in an electric energy signal, thereby inhibiting interference between the harmonic and inter-harmonic components during frequency spectrum analysis and further improving analysis precision.
In order to achieve the purpose, the invention adopts the technical scheme that:
a harmonic and inter-harmonic separation analysis method is used for analyzing an original electric energy signal to obtain harmonic and inter-harmonic parameters, and comprises the following steps: sampling the original electric energy signal to obtain a sampling signal, dividing different analysis windows, performing windowing calculation on the sampling signal in each analysis window to obtain a windowed signal, performing time domain averaging on the windowed signal to obtain a quasi-harmonic signal, and performing discrete Fourier transform on the quasi-harmonic signal to obtain a harmonic parameter of the sampling signal in the analysis window; and subtracting the quasi-harmonic signal from the sampling signal in the analysis window to obtain a quasi-inter-harmonic signal, sequentially carrying out windowing calculation again on the quasi-inter-harmonic signal, carrying out zero filling and discrete Fourier transform at the end of the sequence of the quasi-inter-harmonic signal to obtain an encrypted spectrum signal, and analyzing the encrypted spectrum signal to obtain the inter-harmonic parameter of the sampling signal in the analysis window.
Preferably, ten cycles are taken as one analysis window for the sampling signal.
Preferably, the type of windowing used in the windowing calculation is a hanning window, a Blackman window, or a Blackman-Harris window.
Preferably, the windowing calculation method includes: multiplying the sampled signal within the analysis window by a window signal to obtain the windowed signal.
Preferably, the quasi-harmonic signal is obtained by performing time-domain averaging on the windowed signal according to a cycle scale.
Preferably, the sampling frequency of sampling the original power signal is greater than or equal to 12.8 kHz.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the method can accurately separate the harmonic wave and the inter-harmonic wave in a certain power quality (power) signal in the time domain, thereby inhibiting the frequency spectrum interference between the harmonic wave and the inter-harmonic wave when analyzing the signal in the frequency domain, improving the detection and analysis precision of the harmonic wave and the inter-harmonic wave, and providing more accurate signal component parameters for problem diagnosis, power quality measurement and evaluation and the like of a power system.
Drawings
FIG. 1 is a schematic flow diagram of a harmonic and inter-harmonic separation analysis method of the present invention.
Detailed Description
The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.
The first embodiment is as follows: as shown in fig. 1, a method for analyzing the original electrical energy signal to obtain the harmonic and inter-harmonic parameters by separating the harmonic and inter-harmonic parameters is as follows:
1. synchronously sampling an original electric energy signal, wherein the sampling frequency is required to be greater than or equal to 12.8kHz, so as to obtain a sampling signal;
2. the sampled signal is divided into different analysis windows. According to the national standard, ten cycles are taken as an analysis window (for example, the fundamental frequency of the original electric energy signal is 50Hz, the analysis window is 200 ms);
3. and carrying out windowing calculation on the sampling signals in each analysis window to obtain a windowed signal. The type of windowing used in the windowing calculation may be selected as desired, for example a hanning window, a Blackman window or a Blackman-Harris window may be used. The windowing calculation method comprises the following steps: multiplying the sampling signal in the analysis window by the window signal to obtain a windowed signal;
4. carrying out time domain averaging on the windowed signal according to the scale of one cycle to obtain a quasi-harmonic signal;
5. carrying out discrete Fourier transform on the quasi-harmonic signal to obtain harmonic parameters of the sampling signal in an analysis window;
6. subtracting the quasi-harmonic signal from the sampling signal in the analysis window to obtain a differential signal, namely a quasi-inter-harmonic signal;
7. sequentially carrying out windowing calculation again on the quasi-inter-harmonic signals, carrying out zero filling at the tail of the quasi-inter-harmonic signals and carrying out discrete Fourier transform to obtain encrypted spectrum signals;
8. the encrypted spectral signal is analyzed to obtain inter-harmonic parameters of the sampled signal within the analysis window.
Compared with the existing DFT method, the method of the invention can accurately separate harmonic and inter-harmonic signals in the time domain by windowing the signal time domain and averaging the time domain, effectively inhibits the frequency spectrum interference between the harmonic and the inter-harmonic in the frequency domain, thereby obtaining more accurate harmonic and inter-harmonic analysis parameters, providing more accurate parameters for the problem diagnosis of the power system and the analysis of the power quality signal, and being applied to a power quality measuring device to obtain a high-precision analysis result.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims (4)

1. A harmonic and inter-harmonic separation analysis method for analyzing an original electric energy signal to obtain harmonic and inter-harmonic parameters, characterized by: the harmonic and inter-harmonic separation analysis method comprises the following steps: sampling the original electric energy signal to obtain a sampling signal, dividing different analysis windows, performing windowing calculation on the sampling signal in each analysis window to obtain a windowed signal, performing time domain averaging on the windowed signal to obtain a quasi-harmonic signal, and performing discrete Fourier transform on the quasi-harmonic signal to obtain a harmonic parameter of the sampling signal in the analysis window; subtracting the quasi-harmonic signal from the sampling signal in the analysis window to obtain a quasi-inter-harmonic signal, sequentially performing windowing calculation again on the quasi-inter-harmonic signal, zero padding at the end of the sequence of the quasi-inter-harmonic signal and discrete Fourier transform to obtain an encrypted spectrum signal, and analyzing the encrypted spectrum signal to obtain inter-harmonic parameters of the sampling signal in the analysis window;
the windowing calculation method comprises the following steps: and multiplying the sampling signal in the analysis window by a window signal to obtain the windowed signal, wherein the windowing type adopted by the windowing calculation is a hanning window, a Blackman window or a Blackman-Harris window.
2. A method of harmonic and inter-harmonic separation analysis in accordance with claim 1, wherein: taking ten cycles of the sampling signal as one analysis window.
3. A method of harmonic and inter-harmonic separation analysis in accordance with claim 1, wherein: and carrying out time domain averaging on the windowed signal according to the scale of one cycle to obtain the quasi-harmonic signal.
4. A method of harmonic and inter-harmonic separation analysis in accordance with claim 1, wherein: and the sampling frequency for sampling the original electric energy signal is greater than or equal to 12.8 kHz.
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