CN101196541A - Flicker demodulation method - Google Patents

Abstract

A voltage flicker demodulation method is provided, which relates to a method for demodulating voltage flicker modulation wave. The invention can solve the problems that: the existing demodulation method is easily affected by fundamental voltage and fundamental frequency, additional filter needs to be designed, the arithmetic is complex and is not suitable to use in digital measurement device. The steps of the method in the invention are that: step 101 is to set the number of points sampled N and sampling frequency fs; step 102 is to get voltage sampling value serial u(n) through voltage sample circuit; step 103 is to get voltage successive value Z(k) by discrete Fourier transform of u(n); step 104 is to calculate U(k) according to voltage successive value; step 105 is to get analytic signal z(n) of u(n) by discrete Fourier transform of Z(k); step 106 is to calculate Hilbert of u(n) and transform u(n); step 107 is to calculate the module sequence |z(n)| of z(n) with the formula of |z(n)|=u< 2 >(n)+u< 2 >(n); step 108 is to have discrete Fourier transform to |z(n)|, filter direct-current component and get voltage flicker modulation signal a(n) and the amplitude and frequency.

Description

A kind of flicker demodulation method

Technical field:

The present invention relates to a kind of voltage flicker modulating wave detection method, belong to the detection technical field of voltage flicker signal.

Background technology:

The voltage flicker signal be a kind of be the modulated wave of carrier wave with the power-frequency voltage, the demodulation method of flickering modulating wave commonly used has three kinds: half-wave effective value method, square demodulation method and full-wave rectification method.The effect of half-wave effective value method is general, and is subjected to the influence of fundamental voltage and fundamental frequency easily; Square demodulation method and full-wave rectification method all need to design low-pass filter or the bandpass filter that frequency band is had strict demand, with rightly with direct current, power frequency and industrial frequency harmonic filtering, also more complicated of filtering algorithm simultaneously.Therefore, these three kinds of methods are not suitable for using in digital measuring device.

Summary of the invention:

The present invention is in order to overcome the influence that existing demodulation method is subjected to fundamental voltage and fundamental frequency easily, and the problem that needs design low-pass filter or bandpass filter, algorithm more complicated, is not suitable in digital measuring device, using, and then a kind of flicker demodulation method has been proposed, the step of the inventive method is:

Step 101, sampling number N and sample frequency f in a measuring period are set _s, wherein N is a natural number;

Step 102, by voltage sampling circuit, obtain measured signal voltage sample value sequence u (n) (n=0,1,2 ..., N-1);

Step 103, voltage sample value sequence u (n) is carried out discrete Fourier transformation, obtain contact potential series value after the conversion $\stackrel{\&CenterDot;}{U}\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}u\left(n\right)\&CenterDot;e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="S2007101447722E00011.png,S2007101447722E00021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{N}\&CenterDot;k\&CenterDot;n}(k=\mathrm{0,1,2},...,N-1),$ Wherein

Be plural number, the k time component of voltage after the discrete Fourier transformation of expression voltage sample value sequence u (n);

Step 104, according to the contact potential series value after step 103 conversion Utilize formula $\stackrel{\&CenterDot;}{Z}\left(k\right)=\left\{\begin{array}{cc}\stackrel{\&CenterDot;}{U}\left(k\right)& k=0\\ 2\stackrel{\&CenterDot;}{U}\left(k\right)& k=\mathrm{1,2},...,\frac{N}{2}-1,\\ 0& k=\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="S2007101447722E00011.png,S2007101447722E00021.png"\; state="\{\{state\}\}">N</figure-callout>}}{2},...,N-1\end{array}\right.$ Obtain

Step 105, right

Carry out inverse discrete Fourier transform, obtain the analytic signal z (n) of u (n);

Step 106, utilize formula $\hat{u}\left(n\right)=-j[z\left(n\right)-u\left(n\right)],$ Obtain the Hilbert conversion of u (n)

Step 107, utilize formula $\left|z\left(n\right)\right|=\sqrt{u^2\left(n\right)+{\hat{u}}^2\left(n\right)}$ Calculate the mode sequence of z (n) | z (n) |;

Step 108, right | z (n) | carry out discrete Fourier transformation, and the DC component in the signal after the filtering conversion, obtain voltage flicker modulation signal a (n) and amplitude and frequency.

The invention effect: the present invention is by the Hilbert conversion, the envelope that not only can rapid extraction goes out voltage flicker, and can also calculate the amplitude and the modulating frequency of voltage flicker modulation signal more exactly, have the influence that is not vulnerable to fundamental voltage and fundamental frequency, the characteristics that measurement is accurate, calculated amount is little, be adapted at using in the digital measuring device.

Description of drawings:

Fig. 1 is the process flow diagram of the inventive method; Fig. 2 is the electrical block diagram of voltage sampling circuit in the step 102 of embodiment one.

Embodiment:

Embodiment one: in conjunction with Fig. 1 present embodiment is described, the method step of present embodiment is:

Step 101, sampling number N and sample frequency f in a measuring period are set _s, wherein N is a natural number;

Step 102, by voltage sampling circuit, obtain measured signal voltage sample value sequence u (n) (n=0,1,2 ..., N-1);

Step 103, voltage sample value sequence u (n) is carried out discrete Fourier transformation, obtain contact potential series value after the conversion $\stackrel{\&CenterDot;}{U}\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}u\left(n\right)\&CenterDot;e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="S2007101447722E00011.png,S2007101447722E00021.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{N}\&CenterDot;k\&CenterDot;n}(k=\mathrm{0,1,2},...,N-1),$ Wherein

Be plural number, the k time component of voltage after the discrete Fourier transformation of expression voltage sample value sequence u (n);

Step 104, according to the contact potential series value after step 103 conversion Utilize formula $\stackrel{\&CenterDot;}{Z}\left(k\right)=\left\{\begin{array}{cc}\stackrel{\&CenterDot;}{U}\left(k\right)& k=0\\ 2\stackrel{\&CenterDot;}{U}\left(k\right)& k=\mathrm{1,2},...,\frac{N}{2}-1,\\ 0& k=\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="S2007101447722E00011.png,S2007101447722E00021.png"\; state="\{\{state\}\}">N</figure-callout>}}{2},...,N-1\end{array}\right.$ Obtain

Step 105, right

Carry out inverse discrete Fourier transform, obtain the analytic signal z (n) of u (n);

Step 106, utilize formula $\hat{u}\left(n\right)=-j[z\left(n\right)-u\left(n\right)],$ Obtain the Hilbert conversion of u (n)

Step 107, utilize formula $\left|z\left(n\right)\right|=\sqrt{u^2\left(n\right)+{\hat{u}}^2\left(n\right)}$ Calculate the mode sequence of z (n) | z (n) |;

Step 108, right | z (n) | carry out discrete Fourier transformation, and the DC component in the signal after the filtering conversion, obtain voltage flicker modulation signal a (n) and amplitude and frequency.

Claims (1)

1. flicker demodulation method is characterized in that steps of the method are:

Step 101, sampling number N and sample frequency f in a measuring period are set _s, wherein N is a natural number;

Step 102, by voltage sampling circuit, obtain measured signal voltage sample value sequence u (n) (n=0,1,2 ..., N-1);

Step 103, voltage sample value sequence u (n) is carried out discrete Fourier transformation, obtain contact potential series value after the conversion $\stackrel{\&CenterDot;}{U}\left(k\right)=\underset{n=0}{\overset{N-1}{\mathrm{\&Sigma;}}}u\left(n\right)\&CenterDot;e^{-j\frac{2\mathrm{\&pi;}}{N}\&CenterDot;k\&CenterDot;n}(k=\mathrm{0,1,2},...,N-1),$ Wherein

Be plural number, the k time component of voltage after the discrete Fourier transformation of expression voltage sample value sequence u (n);

Step 104, according to the contact potential series value after step 103 conversion Utilize formula $\stackrel{\&CenterDot;}{Z}\left(k\right)=\left\{\begin{array}{cc}\stackrel{\&CenterDot;}{U}\left(k\right)& k=0\\ 2\stackrel{\&CenterDot;}{U}\left(k\right)& k=\mathrm{1,2},...,\frac{N}{2}-1,\\ 0& k=\frac{N}{2},...,N-1\end{array}\right.$ Obtain

Step 105, right

Carry out inverse discrete Fourier transform, obtain the analytic signal z (n) of u (n);

Step 106, utilize formula $\hat{u}\left(n\right)=-j[z\left(n\right)-u\left(n\right)],$ Obtain the Hilbert conversion of u (n)

Step 107, utilize formula $\left|z\left(n\right)\right|=\sqrt{u^2\left(n\right)+{\hat{u}}^2\left(n\right)}$ Calculate the mode sequence of z (n) | z (n) |;

Step 108, right | z (n) | carry out discrete Fourier transformation, and the DC component in the signal after the filtering conversion, obtain voltage flicker modulation signal a (n) and amplitude and frequency.

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