DTC control schemes for induction motor fed by three-level NPC-VSI using Space Vector Modulation

Switching Table based Direct Torque Control (ST-DTC) appears as a promising control technique to be applied to power converters in the industry. However, the ST-DTC presents some drawbacks as non constant switching frequency and high torque ripples. This work proposes a DTC schemes for an induction motor fed by three-level voltage source inverter (VSI), neutral point clamped topology (NPC), with constant switching frequency and reduced torque ripples applying a Space Vector Modulation (SVM) technique. In these methods, the reference voltage vector of the converter is generated by different manner and synthesized each sampling period using the three nearest vectors in stationary plane. Simulation results are presented, showing that using the proposed techniques the switching frequency is fixed and the sampling frequency can be lowered without reducing the quality of the converter behavior and improving the drive performance.