Traditional high-frequency pulse width modulation (PWM) inverters for motor drives
have several problems associated with their high switching frequency which produces
high voltage change (dv/dt) rates. Multilevel inverters solve these problems because their
devices switch at the fundamental frequency. The concept of multilevel voltage source
inverter is explained. In this paper the cascade inverter is a natural fit for induction motor
drives because of the high VA ratings possible and it uses several levels of separate equal
dc voltage sources which would be available from batteries or fuel cells. The switching
angles of switch devices are determined by optimized harmonic stepped waveform
(OHSW) technique to reduce the output harmonics of cascade multilevel inverter (CMLI)
for induction motor is proposed, as a result the efficiency of system has improved.
Simulation results show the superiority of this inverter over 2-level inverter and were
carried out using ORCAD package.