Hybrid Multilevel Inverter Control for Harmonic Mitigation

Multilevel inverters are superior to conventional two level inverters in high and medium power industrial applications. A hybrid multilevel inverter control is proposed to mitigate the harmonic distortions in the output phase voltage waveforms of induction motor drives. An open-ended induction motor fed with a neutral point clamped three level main inverter on one side and a two level inverter with a floating capacitor on the other side is proposed. The two level inverter is switched to act as a series active filter with null active power supply to the motor, while the three level inverter is pulsed using space vector modulation technique. Thus, the two level inverter will cancel out the voltage distortions in the motor phase voltages. With this configuration, the motor phase voltage harmonic distortions are within the IEEE 519 standards, thereby improving the drive efficiency and motor life-span. The proposed system is simulated and collated with three level neutral point clamped inverter and dual inverter fed open-ended induction motor drive and found to have better harmonic performance.