ABSTRACT
In this, a novel strategy for optimumdesign of flux and torque controller for carrier space vector pulsewidth modulation based vector control of induction motor (1M) drive has been proposed. Twopositive and one negative torque slope levels per half theswitching period has been predicted for 1Mdrive based on which a new optimal control strategy is proposedfor the design of flux and torque controllers where, a P controlleris used in the flux loop and a PI controller is used in the torqueloop. Performance investigation shows that optimally tunedcontrollers used in vector control technique are helpful inreducing torque ripple.The proposed systemis simulated in MATLAB/Simulink software.
INTRODUCTION
Conventional Direct torque control (DTC) basedinduction motor drive has features like fast torque response,simple and robust design, which have made the drive popularin numerous industrial applications. However, its use isrestricted to the applications where precise and smooth torquecontrol is not required. Two major problems associated withsuch drives are (a) variable switching frequency of the inverterpower devices and (b) presence of large electromagnetictorque ripple. In the past various modifications have beensuggested by the researchers to overcome the above problemsassociated with conventional DTC drive. As themagnitude of torque ripple in an inverter-fed 1M is inverselyproportional to the inverter switching frequency, anappreciable torque ripple reduction can be achieved byincreasing the inverter switching frequency. However, it isnot possible to increase switching frequency beyond certainlevel, without using extra hardware. Hence in aconventional DTC higher torque ripple is expected. Toovercome the above problems, SVPWM DTC technique hasbeen suggested. SVPWM DTC based 1M drive hasinherent advantage of inserting null voltage vector aroundactive voltage vectors which may not always be present inconventional DTC. Three PI controllers one each for speed,flux and torque feedback loops has been used in SVPWM DTC based 1M drive. Sensor less SVPWM DTC drivedriven by matrix converter is discussed to reduce thetorque ripple. The major issue related with SVPWM DTCbased 1M drive is proper selection of controller parameters inspeed, flux and torque control loops.

Block Diagram