Unipolar Carrier Based SVPWM For DTC of Open-End Winding Induction Motor Drive

Three-phase Induction Motor (IM) became the workhorse of the industry due to its rigidity. In modern days, induction motor drives are economically viable for variable speed applications. Variable speed drives offer considerable savings in energy. Of various variable speed drives, the Direct Torque Control (DTC) scheme renders superior dynamic response. Despite its merits, this scheme suffers from variable switching frequency, large torque ripples, and flux ripples too. Multi-Level Inverter fed induction motor drives offer low flux and torque ripples, whereas Pulse Width Modulation (PWM) techniques enable constant switching frequency operation. A Uni-polar carrier-based SVPWM with a three-level inverter fed DTC of Open-End Winding Induction Motor (OEWIM) based on slip angle control is proposed in this paper. In contrast to the conventional DTC, the proposed method generates a reference voltage vector without coordinate transformation and is free from look-up table manipulations. In a carrier-based approach, liberty is given to generate the required modulating signal and carrier signal. For an n-level inverter, unipolar carrier PWM requires (n-1)/2 no. of carriers are required rather than (n-1) no. of carriers as in the case of the conventional approach, hence it greatly simplifies the switching logic circuit design. The proposed scheme was tested for various operating conditions using MATLAB/Simulink.