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Low frequency signal frequency measurement method and device

A frequency measurement and low-frequency signal technology, applied in the direction of frequency measurement devices, etc., can solve the problem that the frequency value of the zero-crossing method is not very accurate, and achieve the effects of eliminating and reducing noise interference, high-frequency measurement accuracy and stability

Active Publication Date: 2017-02-01
ELECTRIC POWER RES INST OF GUANGDONG POWER GRID
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Problems solved by technology

However, the research results show that in the case of noise interference, the frequency value measured by the zero-crossing method is not very accurate

Method used

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  • Low frequency signal frequency measurement method and device
  • Low frequency signal frequency measurement method and device
  • Low frequency signal frequency measurement method and device

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Experimental program
Comparison scheme
Effect test

Embodiment approach 1

[0024] like figure 1 Shown, a kind of low-frequency signal frequency measurement method, comprises steps:

[0025] S110. Obtain a frequency measurement signal with a preset data length;

[0026] The time length is expressed as the data length in the discrete domain, and the preset data length measured by different system frequencies is also different. The preset data length can be determined according to the data sampling frequency and signal time length measured by the formula: data sampling frequency × signal time length. Length = data sampling frequency × 0.2s.

[0027] Under the condition of the preset data length, the continuous input signal of the process is converted into a discrete data sequence for storage, and the frequency measurement signal is output according to the sequence of the data sequence.

[0028] S120. Measure the frequency of the frequency measurement signal to obtain an initial frequency measurement value, and use the initial frequency measurement va...

Embodiment approach 2

[0038] The difference between the second embodiment and the first embodiment is that the steps of obtaining the point-frequency filtered signal are further limited.

[0039] like figure 2 As shown, step S130 may include:

[0040] S131, setting the integral constant and the differential constant of the band-pass filter to be equal, the center frequency of the band-pass filter is set to the reciprocal of the integral constant, and the resistance value of the band-pass filter is set to a positive value infinitely tending to 0;

[0041] S132. Use the sine wave frequency measurement signal to excite the bandpass filter, and when the frequency measurement signal frequency is equal to the point frequency, obtain the point frequency filter signal: Y f (t)=Rtsin(ω o t), where R is the resistance, t is the excitation time length, ω o is the point frequency, Y f (t) represents the point-frequency filtered signal.

[0042] The core of the point frequency filter is the point frequenc...

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Abstract

Disclosed are a method and a device for measuring frequency of a low frequency signal. The method for measuring the frequency of the low frequency signal includes steps: obtaining primary frequency measurement value by measuring a frequency measurement signal of the preset data length, and using the primary frequency measurement value as current dot frequency of dot frequency filtering; performing the dot frequency filtering on the frequency measurement signal so as to obtain a dot frequency filtering signal, and casting up the number of times of the dot frequency filtering and 1; measuring frequency of the dot frequency filtering signal so as to obtain output signal frequency value, and confirming frequency measurement value according to difference value between the output signal frequency value and the current dot frequency; if the difference value between the frequency measurement value and the current dot frequency is less than preset error value, or the number of the times of the dot frequency filtering is equal to a preset cycle number, outputting the frequency measurement value; otherwise, using the frequency measurement value as new current dot frequency, and returning to the step of performing the dot frequency filtering on the frequency measurement signal. The method and the device for measuring the frequency of the low frequency signal have high frequency measurement accuracy and stability for the low frequency signal, and have significant practical application value in electricity scientific research, calibration of low frequency range instruments and power grid key parameter measurement.

Description

technical field [0001] The invention relates to the technical field of frequency measurement, in particular to a method and device for measuring the frequency of low-frequency signals. Background technique [0002] Power scientific research, calibration of high-precision power instruments, and the application of a large number of new technologies in power systems have higher and higher requirements for signal frequency, especially low-frequency measurement accuracy. The rated power frequency of power grid operation is 50Hz (Hertz), which is a relatively low frequency. From a control point of view, a frequency measurement accuracy of 10mHz (millihertz) may be sufficient. However, in some new technology applications, a high-precision frequency reference is required, and the frequency measurement accuracy of 10mHz is far from enough. Therefore, high-precision frequency measurement for low-frequency signals is of great significance to power systems. [0003] With the developm...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R23/02
Inventor 李军万文军
Owner ELECTRIC POWER RES INST OF GUANGDONG POWER GRID
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