Modified Scalar Controlled PWM Inverter Fed Induction Motor Drive with Output Filter

LC filter at the output of inverter is used in PWM-VSI fed induction motor drive to reduce the voltage surges at the motor input terminals, losses inside the motor, and thus improve the efficiency as well as the life of the motor. The performance of such drive in conventional scalar control is lower as compared to the same in field-oriented control (FOC) in-terms of its dynamic and on-load starting performance. Therefore, the conventional scalar control technique with motor speed feedback has been modified for its performance improvement and three-phase inverter-voltage references have been generated for PWM-VSI by only considering the steady-state equations of motor and filter in rotor-flux reference frame. Thus, the motor can be started with various loading conditions keeping the magnetizing current constant without violating the basic essence (constant v/f ratio) of scalar control of VSI-fed induction motor drive with output LC filter. The resonant frequency oscillation because of inverter output LC filter has been damped out by suitable active damping technique.