الفهرس 
CHAPTER 1 INTRODUCTION
2.3. Switching StrategyOnly 14 pages are availabe for public view
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Abstract
The importance of the AC-AC converters increases nowadays due to their
sensitive role in industry as they are utilized in many industrial applications, such as induction machine adjustable speed drives, dynamic voltage restorers (DVRs), compensation of voltage sag and swell, lighting control, and electric heaters. Due to their vital role, there is a continuous study and a growing interest in the development of AC-AC converters. In recent years, the pulse width modulation (PWM) AC-AC converters implemented by MOSFETs and/or IGBTs have absorbed much attention for their flexibility and potential ability to achieve high efficiency, reliability, and power quality. The use of limit number of semiconductor switches and passive components limits the converter’s efficiency and even more increases its size and cost. Therefore, there is a growing interest in the development of PWM AC–AC converters to reduce their overall size and cost while increasing their efficiency. This thesis introduces a single-phase direct PWM AC-AC converter. The proposed converter has the possibility to be utilized as a voltage buck or buckboost converter. The proposed converter utilizes a minimum number of semiconductor switches and passive components that decrease the converter’s power losses and offer high efficiency. It can be operated with simple PWM control and doesn’t require soft-commutation strategies. It doesn’t suffer from the input source shoot-through and commutation problems. Moreover, it supplies both continuous input and output currents. The common sharing ground of the input and output gives the proposed converter the feature that it can be utilized for voltage sag and swell compensation. Also, the common sharing ground makes the proposed converter suitable to be modified and utilized as a three phase direct PWM AC-AC converter. A comparison of the proposed converter with similar existing converters is presented. Also, detailed circuit analysis, component design guidelines, and simulation results using the MATLAB/Simulink environment are demonstrated. A laboratory prototype has
been built and tested to validate the converter’s performance and confirm the
results obtained by computer simulation.