A comparative study between different modulations techniques used in field oriented control induction motor drive

In industries, where adjustable or variable speed drives are required, induction motor drives are chosen with various control strategies to have fast flux and torque response. In order to overcome sluggish response of induction motor and to have decoupled flux and torque characteristics, field oriented control (FOC) is implemented. These drives consists of voltage source inverters with various modulation schemes like SPWM, THISPWM, SVM etc. in order to minimize the harmonics present in the output voltage or current. Presence of harmonics makes the response non-sinusoidal and generate heating, torque pulsation etc within the machine. But for field oriented control induction motor drives, selection of efficient modulation scheme is important as machine current is controlled and in this current loop presence of ripples may create multiple zero crossing problems in the SPWM. In this paper, different modulation schemes are investigated and their performances are compared for a variable speed three phase FOC Induction motor. This system is modeled in MATLAB and SIMULINK where all the above stated modulation schemes are implemented. It is observed that the FOC based IM drive gives better result when subjected to Space Vector Modulation Scheme.