A new multicarrier SPWM technique for five level cascaded H-bridge inverter

Many researchers have investigated modulation techniques applied to the cascaded multilevel inverter to improve its harmonics performance. Different methods have been proposed for cascaded multilevel inverter modulation that one of them is level-shifted PWM method (LS-PWM). In this paper, a novel multicarrier SPWM technique which uses a trapezoidal triangular carrier is proposed for a five level cascaded multilevel inverter. This carrier waveform is being implemented with different LS-PWM techniques such as phase disposition (PD), phase opposition disposition (POD) and alternative phase opposition disposition (APOD). The line voltage and total harmonics distortion (THD) obtained in various techniques are compared with the outputs of triangular carrier wave. To validate the improvement, these PWM techniques are simulated for a 1KW, 3φ five level inverter with 2 KHz switching frequency using MATLAB/SIMULINK. The effect of modulation index on the line voltage and harmonics are also analyzed. The proposed switching technique enhances the fundamental component of the output voltage and lowers total harmonic distortion.