الفهرس 
Concept of Multilevel InvertersOnly 14 pages are availabe for public view
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Abstract
The concept of multilevel inverter is to build up an ac stair-case output voltage from a dc supply with the advantage of low distortion and low stress on the switches. Multilevel inverters are suitable to be integrated with renewable energy sources such as photovoltaic, and fuel cells.The different conventional multilevel inverters and several recent topologies are reviewed and compared in this thesis. After these comparisons, the most suitable topology has been chosen. The chosen inverter has the advantage of producing high number of levels using less number of switches. It consists of two stages; the level-generation stage that produces a stepped dc voltage, and the polarity-generation stage to convert from dc to ac. Higher number of levels can be achieved throughout the asymmetrical choice of the inverter input unit’s voltage.The different modulation techniques suitable for controlling multilevel inverters are reviewed in this thesis. Techniques based on the fundamental switching frequency modulation such as the staircase with fixed time step and selective harmonic elimination are used to control the inverter. selective harmonic elimination based upon genetic algorithm optimization technique is performed to eliminate the low order harmonics and minimize the total harmonic distortion in the output voltage. A proposed sinusoidal pulse width modulation technique is also presented. This technique has the advantage of reducing the control complexity of the inverter switches since it requires only one modulating signal and a single carrier signal.