Investigations on Three Phase Five Level Diode Clamped Multilevel Inverter

Multilevel inverters have become more popular over the years in high power electric applications without use of a transformer and with promise of less disturbance and reduced harmonic distortion. This work proposes three phase five level Diode Clamped Multilevel Inverter (DCMLI) to simulate various modulating techniques for induction motor load. These Pulse Width Modulation (PWM) techniques include Carrier Overlapping (CO) strategy, Variable Frequency (VF) strategy, Phase Shift (PSPWM) strategy and Sub-Harmonic Pulse Width Modulation (SHPWM) i.e. Phase Disposition (PD) strategy, Phase Opposition Disposition (POD) strategy and Alternate Phase Opposition Disposition (APOD) strategy. The Total Harmonic Distortion (THD), VRMS (fundamental), crest factor, form factor and distortion factor are evaluated for various modulation indices. Simulation is performed using MATLAB-SIMULINK. It is observed that PODPWM method provides output with relatively low distortion and COPWM is found to perform better since it provides relatively higher fundamental RMS output voltage for Induction Motor (IM) load.