Cascaded H-Bridge Seven Level Inverter using Carrier Phase Shifted PWM with Reduced DC sources

Abstract

This paper presents a multi level inverter with seven level voltage generation scheme using cascaded H-bridge MLI topology utilizing reduced number of DC sources. By utilizing switched capacitor methodology the number of DC sources required to generate seven levels is minimized. Three numbers of H-bridges are employed in seven level generations where only one dc source is used and in the remaining bridges only capacitors are used along with a unidirectional switch for capacitor charging. This paper utilizes a multi carrier PWM technique based on phase shifted carrier for generating pulses to get seven level output. This paper also discusses the switching schemes for charging switches used and there is a small dip in efficiency of this inverter due to the existence of power loss which occurs during charging and discharging the capacitors. The advantage of this inverter is it can produce an output voltage higher than the input voltage in the ratio 1:3 and also the output voltage have lesser harmonics than conventional square and quasi square wave inverters due to multilevel output voltage. The proposed multi level inverter using single DC source and three cascaded h bridges using carrier phase shifted sine PWM technique is implemented in MATLAB/Simulink platform and merits of the proposed inverter system is verified through simulations.