Optimized Modulation Technique for Cascaded H-Bridge Multilevel Inverter

Number of modulation methods has been presented for multi-level inverter operation. In this paper, the troubles faced by general modulation schemes are analyzed, and an optimized modulation method is proposed for 7-level Cascaded H-bridge Multi-level Inverter (CHB-MLI). Switching devices of CHB-MLI has to undergo high frequency operation and that is reduced by adopting the single-pole frequency doubling modulation method in which the equivalent switching rate of inverter remain constant. Another problem for switching devices is related to unequal switching stress of each H-bridge, which is balanced by adopting a modified LSPWM method by the alternation in the switching of H-bridges in every cycle. The control scheme is simple and the Total Harmonic Distortion (THD) of line voltage is superior to the carrier phase shift technique. The stress of the switching devices of each H-bridge is the same, uniform distribution of heat dissipation, considerable reduction in switching loss, and improved reliability of the system as well as service life is enhanced. The outcomes are supported by simulation outcome obtained using MATLAB/Simulink that justifies the feasibility of the projected optimized modulation method.