Proceedings of the 2007 International Conference on Wavelet Analysis and Pattern Recognition, Beijing, China, 2-4 Nov. 2007
MEASUREMENT OF VOLTAGE FLUCTUATION AND FLICKER IN
ELECTRIC POWER SYSTEM BASED ON WAVELET TRANSFORM
XIN-LING WEN
1
, YU CHEN
1, 2
1
ZhengZhou Institute of Aeronautical Industry Management, Zhengzhou 450015, China
2
College of Electronic and Information, Northwestern Polytechnical University, Xi’an 710072, China
E-MAIL: wenxinling@zzia.edu.cn, chenyu3440@gmail.com
Abstract
Large impact and disturbance of electric network will
occur when the power equipment in a larger load runs. This
paper introduces voltage fluctuation and flicker analysis by
using better character of time-frequency localization based
on the methods of synchronous square detection and multi
resolution wavelet transform. The amplitude and frequency
of voltage fluctuation and flicker signal are measured
through demodulation and decomposition. Abrupt-changing
time and singularity degree of signals are also presented.
The results of simulation experiment show that this method
has better capability in measurement and time-frequency
analysis, which can be applied to measure abrupt-changing,
unstable voltage fluctuation and flicker signal.
Keywords: Wavelet transform; multi-resolution analysis;
Mallat arithmetic; synchronous determination
1. Introduction
The load of concussion power arouses voltage
fluctuation and flicker of electric system. [1] Such as smelt
EAF (E
lectric Arc Furnace), rolling mill, electric
locomotive, electric arc welding machine, etc. Their active
power and reactive power fluctuates widely when they are
working. With the development of large-scale industry, t
he
power of concussion load will increase ceaselessly. So, it
will bring enormous influence to the electric energy quality,
and affect electric power consumer to use electricity
normally, which institute electric social effects of pollution.
On the other hand, because of the development of science
technology, new techniques adoption, computer and electric
instrument using abroad, the quality of electric energy is
demanded higher and higher.
“Voltage fluctuation and flicker permission in electric
energy quality” (GB12326-90) was formally approved as the
national standard in 1990 by NTSA (National Technology
Supervision Administration). It is playing a very important
role in controlling electric net voltage fluctuation and flicker.
To restrain and father the voltage fluctuation and flicker, we
should provide its demodulation
envelope tracking by rule
and line from electric net signal. So we can carry out
comprehensive treatment of flicker pollution. [2]
2. Method of voltage flicker monitor
Now, voltage flicker measurement methods include
square demodulation, full wave commutation, and wavelet
transform, etc. Square demodulation method and full wave
commutation method need to design low-pass or band-pass
filter with strict frequency band in order that DC, power
frequency, and
harmonic will be filter felicitously, which is
complex measurement work. So they are all unsuitable to
measure time-changing voltage flicker signal and analyze
time-frequency.
Many scholars began to use wavelet transform method
to research electric energy quality at home and abroad.
Wavelet transform can measure the time of disturbance
appearance precisely to unstable signal. At first, we use
wavelet transform to locate flicker accurately, then we use
FFT (Fast Fourier Transform) to analyze the time period of
appearing flicker. So we can get amplitude and frequency of
flicker signal. We need filter signal after squaring when we
use squaring measurement arithmetic to measure transient
signal. Wavelet transform arithmetic has not function in
contrast to filter, which has signal attenuation. It has not
middle-process attenuation, which real course is filter’s
process course. So it will not increase complication degree
of operation. Otherwise, squaring monitoring arithmetic
cannot record the start time of wave signal availably, while
signal measurement method in wavelet transform can do it
well.
This paper uses method of voltage flicker signal
measurement based on the multi-resolution of wavelet
decomposition and synchronous demodulation. This method
uses multi-resolution of wavelet decomposition filter instead
of low-pass filter, which can precisely detect voltage flicker
envelope signal, and detect high frequency of voltage flicker.
So the abrupt change time is detected. In addition, the
method is used to decompose the envelope signal of
demodulation any more based on the multi-resolution of
wavelet decomposition and sub-band filter method in order
that the amplitude and frequency sub-component of each
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