Direct torque and flux control (DTC) of induction motor (IM) is one of the most effective methods in control of this electric machine. Using DTC the restrictions and complexities of vector control can be avoided. In this paper, the algorithm of DTC of an asymmetrical six-phase induction motor (SPIM) with a two-level voltage source inverter (VSI) is improved. SPIM can be used in high power applications or fault tolerant systems such as traction systems with reduced torque pulsations. The machine is modeled based on vector space decomposition (VSD) theory. Selecting suitable switching vectors the torque and flux of the motor are controlled properly. Using the proposed algorithm, the zero sequence current components are almost zero which is very important in SPIM control; since without them, the harmonics of phase currents are reduced and efficiency is improved considerably. The validity and effectiveness of the proposed method are confirmed by experimental results.

Keywords: Asymmetrical six-phase induction motor, Zero sequence, Direct torque control (DTC)