Method and apparatus for measuring interhamonics of power grid

A power grid and harmonic technology, applied in the field of power system inter-harmonic measurement instrument and inter-harmonic measurement, can solve the problem of difficult and accurate measurement of inter-harmonic, reduce harmonic measurement errors, reduce synchronization errors, and save computing time Effect

Inactive Publication Date: 2012-01-18
NANJING UNIV OF INFORMATION SCI & TECH
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Problems solved by technology

[0015] The technical problem to be solved by the present invention is to propose a method for measuring inter-harmonics of a power grid and a measuring instrument for inter-harmonics

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  • Method and apparatus for measuring interhamonics of power grid
  • Method and apparatus for measuring interhamonics of power grid
  • Method and apparatus for measuring interhamonics of power grid

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Embodiment Construction

[0038] The technical scheme of the invention will be described in detail below in conjunction with the drawings:

[0039] Such as figure 1 As shown, the interharmonic measuring instrument of the present invention includes two special units:

[0040] (1) Approximate synchronization unit: the grid frequency tracking is realized by the phase-locked loop circuit (PLL), and the zero-crossing detector cooperates with the DSP to accurately measure the frequency: with a constant sampling frequency f S The grid voltage (current) waveform is sampled, and the PLL circuit tracks the grid frequency, and the output of the PLL circuit is used as the sampling clock of the ADC, so that the sampling is as close to synchronous sampling as possible.

[0041] (2) HHT-FFT calculation unit: Use HHT to extract the envelope of the signal, perform FFT analysis on the envelope signal, and then calculate the harmonic and interharmonic information of the power grid.

[0042] Such as figure 2 As shown, the approx...

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Abstract

The invention discloses a method and apparatus for measuring interhamonics of a power grid. The method comprises the following steps of: tracking the power grid by a PLL (Phase Locked Loop), accurately measuring frequency by a zero crossing detector matched with a DSP (Digital Signal Processor): sampling a power grid voltage (current) waveform at a constant sampling frequency, tracking the power grid frequency by the PLL, wherein the output of the PLL is used as a sampling clock of an ADC (Analog to Digital Converter); and then enveloping an extraction signal by adopting an HHT (Hilbert Huang Transform) method, carrying out FFT (Fast Fourier Transform) analysis on the enveloped signal, and finally figuring out information of harmonics and interhamonics of the power grid. The apparatus comprises three voltage transformers, three current transformers, an approximate synchronous sampling unit and an HHT-FFT computing unit. According to the invention, the HHT method is combined with the FFT method, power frequency carriers and envelopes are separated by using HHT and are respectively subjected to frequency spectrum analysis by using the FFT; and when the method and the apparatus are used in an actual power grid, measured harmonics and interhamonics precision and instantaneity meet the requirements of IEC (International Electrotechnical Commission).

Description

Technical field [0001] The invention relates to a power system inter-harmonic measuring instrument and an inter-harmonic measuring method, and belongs to the technical field of power quality monitoring. Background technique [0002] Harmonic monitors have been used in power systems for a long time, but there are not many harmonic monitors that can measure interharmonics, and there are not many harmonic monitors that can monitor harmonics and interharmonics online in real time. With the improvement of power quality requirements, the measurement of power system interharmonics is one of the important contents of power system power quality monitoring. The IEC61000-4-7 standard and most harmonic measuring instruments still use the FFT (Fast Fourier Transform) method for inter-harmonic measurement. The FFT method to measure the entire harmonics of the power grid is more reasonable and accurate when the synchronization error is small. However, the traditional FFT method to measure the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R23/16
Inventor 梅永王柏林熊杰锋
Owner NANJING UNIV OF INFORMATION SCI & TECH
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