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
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