Active power filter with automatic control circuit for neutral current harmonic minimization technique
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Date
2007
Authors
A Bakar, Mohd Izhar
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Abstract
The aim of this thesis is to develop an efficient and reliable active power filter in order
to minimize the excessive neutral current as well as harmonic problem in the neutral
line for three phase four wire system. This neutral current generally consists of triplen
harmonics order such as 3rd, 9th, 15th and etc., which are generated by nonlinear load.
The dominant harmonic is 3rd harmonic current. In response to this problem, this thesis
proposes an active power filter scheme along with star-delta transformer application to
cancel neutral current harmonic in neutral line. The development of active power filter,
consisting of power switcher, which is modulated based on new switching technique by
using dual level triangular waveform and single sinusoidal, is proposed. In order to
further improve the harmonic current reduction, the new automatic control circuit for
output-following signal is introduced. This is to enable the pulse width modulation to be
generated by active power filter that is synchronized with magnitude of neutral current
inconsistency. The research also proposes a new approach for the protection in
operating system that enables the system to be in turn-OFF mode automatically due to
over current or short circuit. The overall performance results showed that the neutral
current reduction by using active power filter with automatic control circuit was 68.4%
as compared to without automatic control circuit, which was 61.9%. The improvement
of neutral current reduction was 6.5%. The results also showed that the average of
harmonic current reduction for 3rd, 9th, and 15th increased from 60.1% to 65.8%, 67.7%
to 74.9%, and 71.1% to 75.9% respectively. A study on the effects of active power
filter on the electrical power line distribution system was also carried out. The overall
result showed that the Total Harmonic Current Distortion decreased from 83.6% to
62.3%. Meanwhile, the Power Factor increased from 0.54 to 0.76. The validity of
results is demonstrated by simulation and experiment.
Description
PhD
Keywords
Science Physic , Active power filter , control circuit , neutral current harmonic , minimization technique