Micro-grid harmonic wave detection method

A harmonic detection and micro-grid technology, applied in the field of pattern recognition, can solve the problems of too strict wavelet base selection, long calculation time, and low practicability, and achieve improved modal aliasing, accurate detection, and improved spectrum aliasing Effect

Inactive Publication Date: 2019-01-15
NANJING UNIV OF SCI & TECH
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Problems solved by technology

In this way, not only the frequency can be obtained, but also the time can be located, that is, the time and scale of the signal can be analyzed at the same time, and the time and frequency of the signal can be represented at the same time

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Embodiment Construction

[0021] In conjunction with the accompanying drawings, a microgrid harmonic detection method of the present invention includes the following steps:

[0022] Step 1. Collect the voltage and current harmonic signals at the common point of the micro power grid-connected place;

[0023] Step 2. Use the tower method in wavelet transform to decompose and reconstruct the collected voltage and current signals to obtain high-frequency signals and low-frequency sub-signals; the decomposition formula is:

[0024]

[0025] Where t=1,2,...,N is the discrete time series number, f(t) is the original signal; j=1,2,...,J,J=log 2 N is the number of layers; H and G are wavelet decomposition filter coefficients in the time domain; A j is the wavelet coefficient of the approximate part of the signal f(t) at the jth layer, that is, the low frequency part; D j is the wavelet coefficient of the detail part of the signal f(t) at the jth layer, that is, the high frequency part.

[0026] Step 3. De...

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Abstract

The invention discloses a micro-grid harmonic wave detection method. The micro-grid harmonic wave detection method includes the following steps: 1) a micro-grid harmonic wave signal acquisition systemacquires a voltage and current harmonic wave signal of a common point of micro-power source connection; 2) the acquired voltage and current harmonic wave signal is decomposed and reconstructed according to an idea of multiresolution analysis in wavelet transformation by using a tower method in the wavelet transformation to acquire a series of high frequency signals and low frequency sub-signals;3) the acquired low frequency sub-signals are decomposed into a series of intrinsic mode function components by using an empirical mode decomposition method, and fundamental components and high-orderharmonic components are extracted from the intrinsic mode function components; and 4) Hilbert-Huang transform is performed on the extracted fundamental components and high-order harmonic components toacquire information of amplitudes, frequencies and phases of harmonic waves. The micro-grid harmonic wave detection method overcomes the problem of dependency of the wavelet transformation on selection of basic wavelets and improves frequency spectrum aliasing of the wavelet transformation, thus harmonic waves of currents in micro-power source connection can be detected in a more real-time and accurate manner.

Description

technical field [0001] The invention belongs to the field of pattern recognition, in particular to a method for detecting harmonics of a micro-grid based on wavelet transform and Hibbert-Huang transform. Background technique [0002] The power system has always been developing in the direction of high voltage, ultra-high voltage, large power grid, and large-capacity units. However, with environmental pollution and the serious energy crisis, the use of clean energy and small-capacity power generation technology has attracted people's attention. Power grid has become an important factor affecting power system reform. [0003] During the operation of the microgrid, it is precisely because of the existence of a large number of power electronic devices that nonlinear devices such as rectifiers and inverters produce a series of high-order waveforms in addition to normal power frequency harmonics (50HZ)—— Harmonics, causing harmonic pollution, affects the normal use of plant equip...

Claims

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Application Information

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IPC IPC(8): G01R23/165
CPCG01R23/165
Inventor 江晓燕熊玉倩杨烨沈岳峰程青青
Owner NANJING UNIV OF SCI & TECH
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