Efficiency Improvement in DTC of Six-Phase Induction Machine by Adaptive Gradient Descent of Flux

In this paper, a flux search controller is proposed to improve the efficiency of direct torque control of a six-phase induction machine. The proposed flux search controller is based on adaptive gradient descent of motor flux value with fast response and easy implementation. A proper loss model of six-phase induction motor in conjunction with the proposed method has been presented. Stator frequency variation with respect to flux reduction is considered as a new aspect of fast flux search control. Reduction of the flux in the search control technique leads to an increase in stator frequency, and an error in core loss calculation occurs if the frequency variation is ignored. The proposed search controller greatly improves efficiency by reducing core loss as well as harmonics loss. The approach not only is easy to implement and adaptive with regard to parameter variations but also requires no additional hardware for practical implementation. The simulation and experimental results presented in this paper verify the effectiveness of the proposed method in improving efficiency of direct torque control of six-phase induction motor drive.