Simplified Implementation of Synthetic Vectors for DTC of Asymmetric Six-Phase Induction Motor Drives

This paper presents a simplified implementation technique for direct torque control (DTC) of asymmetric six-phase induction motor drive. Current harmonics of fifth and seventh order are observed in the phase currents if conventional DTC scheme is extended for the asymmetric six-phase machine. These harmonic components are not responsible for torque production, thus causing losses in the motor winding. Synthetic vectors are generally used for reduction of current harmonics. Average voltage in <inline-formula><tex-math notation="LaTeX">$xy$</tex-math></inline-formula> subspace is maintained to zero by synthetic vectors leading to reduction of currents in <inline-formula><tex-math notation="LaTeX"> $xy$</tex-math></inline-formula> subspace. A simplified method of implementation of synthetic vectors is proposed in this paper, which eliminates the need for designing of switching sequence and requirement of field-programmable gate array. Also, the number of synthetic vectors that can be possibly produced is increased compared with the ones developed by techniques available in the literature. The experimentation is carried out on a laboratory-developed prototype and the experimental results are presented in this paper to verify the proposed scheme.