PERFORMANCE EVALUATION ON MULTI-LEVEL INVERTER FED INDUCTION MOTOR DRIVE

Abstract

All the matter in the universe, the general trend to minimize harmonics in conventional 2-level voltage source inverter (VSI) is towards various PWM techniques. However, this trend invited problems, like the increase of switching frequency increased the switching losses, generating a common mode voltage which becomes significant at high power levels. Multilevel power converters have gained much attention in recent years due to the proven mitigation of various problems sited above. The general structure of the multilevel inverter is such as to synthesize a sinusoidal voltage from several levels of DC voltage. Increasing the number of level produces a fine staircase waveform approaching close to a sinusoidal wave with minimum harmonic distortion. In this thesis simulation of various inverters (from 2-level to 5-level) is carried and the performance of the inverter is investigated under various operating conditions by changing the load and output frequency. The digital implementation of Space Vector Pulse Width Modulation (SVPWM) technique for both Three phase inverter and Neutral Point Clamped Inverter using `80486 Processor Based PC with Data Acquisition Cards' is described in detail. The work mainly focuses on the improvement in THD of both voltage and current waveforms from normal three-phase inverter to Neutral Point Clamped Inverter. The performance of open loop V/f control of three-phase Induction Motor drive fed from both conventional Three-Phase Inverter and Neutral Point Clamped Inverter is investigated in open loop. Finally the vector control scheme with for three-level inverter using SVPWM is implemented to drive an induction motor for variable speed applications.