Analysis And Design Of Multilevel Inverter Using Spwm For Closed Loop Induction Motor Drive

Abstract

The power loss, the electromagnetic stress dv/dt and Total Harmonics Distortion becomes the issue of industrial electrical drives today. Induction motors are most widely used machine in both industrial and domestic sector. However, they require variable-frequency power-electronic drive for their optimal speed control. Out of the various methods, the cascaded multilevel inverter based speed control has proven to be the most versatile. The SPWM techniques are used at this thesis work that providing better sinusoidal wave form of both voltage and current. In this thesis work, using MATLAB R2013a/SIMULINK software, a five and seven cascaded multilevel inverter topologies are analyzed, designed and simulated to eliminate the fifth and seventh harmonics that are dominant in closed loop induction motor drive. The THD values of five level and seven level CMLI inverter is compared. The THD value measured from chemical industry corporation mugher cement factory are 49% and 7. 10% for current and voltage respectively is compared with designed cascaded multilevel inverter are 4.06% and 5.06% for current and voltage respectively. Hence the cascaded multilevel inverter is proven and result with lower THD value. Moreover, the PI controller is designed and cascaded with multilevel inverter to obtain smooth speed control of IM as per settled reference speed. The smooth speed control IM is compared for the two CMLI for the same settling time and settled reference speed.