Analysis of Cascaded H-Bridge Multilevel Inverter with Phase Shifted PWM on Induction Motor

Multilevel converter technology has emerged as a very important alternative in the area of high-power medium voltage energy control. The voltage source inverters produce a voltage or a current with levels either 0 or ±V dc they are known as two level inverters. To obtain a quality output voltage or a current waveform with a minimum amount of ripple content, they require high switching frequency. In high power and high voltage applications, these two level inverters, however, have some limitations in operating at high frequency. The multi-level inverter is to synthesize a near sinusoidal voltage from several levels of dc voltages. As number of levels increases, the synthesized output waveform has more steps, which provides a staircase wave that approaches a desired wave form. Also, as steps are added to waveform, the harmonic distortion of the output wave decreases, approaching zero as the number of voltage levels increases. Referred to as cascaded-inverters with Separate DC Sources (SDCs) or series connected H-bridge inverters. This paper multilevel converter fed induction motor drive with different voltage levels is considered and simulation results are presented in terms of total harmonic distortion (THD). The PWM signal thus generated is then used as triggering pulses for the multilevel inverters.