Investigations on Three Phase Five Level Flying Capacitor Multilevel Inverter

摘要

The use of multilevel inverters is widespread in medium voltage applications due to their inherent voltage sharing among the devices. This work proposes three phase five level Flying Capacitor Multilevel Inverter (FCMLI) using various modulating techniques for induction motor load. These Pulse Width Modulating (PWM) techniques include Carrier Overlapping (CO) strategy, Variable Frequency (VF) strategy, Phase Shift (PS) 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. COPWM is also found to perform better since it provides relatively higher fundamental RMS output voltage for Induction Motor (IM) load.