Torque ripple minimization in direct torque control of six-phase induction machines using fuzzy inference systems

In this work, a duty ratio control scheme for inverter fed six-phase induction machines using the direct torque control method based on a fuzzy inference system is presented. A six-phase induction machine has six windings spatially phase shifted by sixty electrical degrees. An improved steady state torque response has been achieved by using the duty ratio control and it has shown less torque ripple compared to the conventional direct torque control. A fuzzy inference system has been used to implement the duty ratio during each switching cycle using the torque and flux errors as inputs. The main advantage of the proposed algorithm is the improvement of torque and flux ripple characteristics in the low speed mode. This feature provides an opportunity for motor operation under minimum switching loss and low noise.