ISSN: 1999-8716

Keywords : PWM


FROM A HORIZONTAL CYLINDER EMBEDDED IN A POROUS MEDIA

Ahmed Hassen Ahmed; Eklas Edan Kader; Hatam Abd Hassan; Abdulrakib Abdulwahab Masad Al-Wahbi; Omer Hazem Karofa; Manar Salih Mahdi; Safa Hussain Abid Awn; Osama Y. AL-Rawi; Ali H. Aziz; Saad Qassim Fleh; Ali Laftah Abbas

DIYALA JOURNAL OF ENGINEERING SCIENCES, 2011, Volume 4, Issue 1, Pages 1-19

ABSTRACT:- Theoretical and experimental study of heat transfer steady natural convection from the cylinder embedded in a saturated porous media was cared out. the theoretical part of the work includes the derivation of the governing momentum and energy equation by using Darcy flow model. The two equations are solved by finite difference method with constant cylinder surface temperature, with a Peclet number under steady condition and Rayleigh number ranged between (10

Keywords

natural convection
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porous media
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horizontal cylinder
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الحمل الطبيعي
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الوسط المسامي
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اسطوانة أفقية.

SWITCHING ANGLE OPTIMIZATION BASED GENETIC ALGORITHMS FOR HARMONIC REDUCTION IN THREE-PHASE PWM STRATEGY

Osama Y. AL-Rawi

DIYALA JOURNAL OF ENGINEERING SCIENCES, 2011, Volume 4, Issue 1, Pages 83-94

ABSTRACT :- In variable speed drive (VSD), it is desirable to reduce the harmonic effects, which causes current distortion and torque pulsation, besides, the harmonic power losses is an additional power losses that is introduced in the motor due to the presence of harmonic voltages.
However, the problem of the high total harmonic current distortion (THD) still exists specially at low and medium speeds by using sub-optimal pulse width modulation (PWM) strategy. In the past to generate optimized PWM, is done by defining a general PWM in terms of a set of switching angles. Which result in a set of nonlinear equations in terms of the unknown switching angles. These equations are nonlinear as well as transcendental in nature. There is no efficient method that can be applied to solve such equations. The practical method of solving these equations is a trial and error process. Taking all the factors into account, a numerical technique can be applied to solve these set of nonlinear equations, but with some limitations.
To overcome these limitations, Genetic algorithms (GAs) serves to search for optimal switching angles setting. In addition, the (THD) will be reduced, this lead to obtain the optimal PWM waveform and to simplify the practical implementation, and then improving the performance of the system output.
GAs were employed as a search and optimization engine. Normally the tuning of the switching angles is a trail and error problem.
In this paper, GAs provides a much simpler approach to off-line tuning of PWM switching angles than the rather complicated non-genetic optimization algorithms.
Keywords:- Optimization, Genetic algorithm, PWM.