This paper presents an improved switching selection method for direct torque control (DTC) of five-phase induction machine. A five-phase inverter has 32 voltage vectors, including 30 nonzero and 2 zero voltage vectors. The effective voltage vector is represented as a large, medium, or small voltage vector according to its magnitude. The voltage vector magnitude is related to the torque response and torque ripple. When the large voltage magnitude value is selected, the torque response time decreases with increased torque ripple. However, when the voltage magnitude is small, the torque response time and torque ripple increase. As a result, this paper proposes an selection method of optimal voltage vector for improved DTC of a five-phase induction motor. In addition, this paper shows a torque ripple reduction method of DTC using fuzzy controller in five-phase induction machine. The conventional DTC method has some drawback. First, switching frequency changes according to the hysteresis bands gap and motor’s speed. Second, in short control period, the torque ripple is rapidly increased. To overcome this problem, the proposed method is changing the voltage vector insertion time by using the designed fuzzy controller by torque error. The proposed methods are simulated and experimentally verified on a tow-level inverter-fed five-phase induction motor drive.
