Duty ratio control technique with torque ripple minimization for induction motor-based electric vehicle applications

DTC drives are utilized in modern electrical vehicles. This paper proposed a blend of the conventional direct torque control (DTC) and a duty ratio control technique known as the modified duty ratio control for torque ripple reduction. In this modified technique, voltage vector selection is based on the conventional DTC technique, which utilizes six entire voltage vectors and two zero vectors. The torque error modifies the duty ratio of the voltage vector. In the presented technique, the magnitude of the torque error is the controlling variable for the modification of the duty ratio of the voltage vectors. Depending on the magnitude of the torque error, a duty ratio-modulating factor is generated from a lookup table, which is then multiplied by the duty ratio for any of the selected voltage vectors. Thus, improved performance in terms of low torque and current ripples is achieved from a DTC drive by a control strategy with less complexity, which preserves the simplicity of switching to table-based traditional DTC drives. Simulation and experimental results validate the proposed switching strategy.