Modified Sliding Mode Observer-Based Direct Torque Control of Six-Phase Asymmetric Induction Motor Drive

Abstract

In this study, a six-phase induction asymmetric induction motor (SPAIM) was examined, whose performance surpasses that of its three-phase counterpart, with regard to the torque density, torque pulsation, fault tolerance, power rating per inverter lag, and noise characteristics. Speed-encoder-less direct torque control (DTC) for SPAIM with virtual voltage vectors (VVVs) and a modified sliding mode observer (MSMO) are described. The SPAIM model was developed using a stationary $\alpha-\beta$ frame for DTC. The conventional DTC of the SPAIM drive is a simple extension of DTC for a $3-\varPhi$ motor drive that yields higher distortion in the stator currents. To mitigate the large amount of distortion in the stator current, VVVs were used to significantly reduce the harmonic content in the stator currents. Furthermore, to overcome the large amount of chattering observed in the case of a traditional sliding mode observer, particularly under low-speed operation, the MSMO was employed to reduce chattering even under low-speed operation. The performance of the proposed observer was verified under all the operating conditions suitable for the propulsion mode of an electric vehicle using Matlab/Simulink, and the results were experimentally validated.