Three Stage Cascaded Multilevel Inverter using Pulse Width Modulation Technique

Abstract

In the last few years, the necessity of increasing the power quality enhancement in industry has sustained the continuous development of multilevel- inverters due to high efficiency with low switching frequency control method. The inverter is a semiconductor device which is used to convert the fixed DC voltage into symmetrical AC voltage without changing the magnitude. To improve the power quality (AC) from the inverter output by performing the power conversion in small voltage steps resulted in lower harmonics. The output voltage on the AC side can take several discrete levels of equal magnitude. The harmonic content of this output voltage waveform is greatly reduced, if compared with a two level voltage wave form (inverter). This method is called as multilevel inverter. Multi-level power inverters employ power semiconductor switches in the inverter to select one or more of multi dc voltage source to create staircase voltage waveform at the inverter output. In the multilevel inverter the output voltage is in the form of stepped waveform, so that the harmonics will be reduced and thereby increase the voltage gain and power quality of the output AC from the MLI.