An Isolation Transformer-less Single DC Source fed Dual 5-leg Inverter Controlled 5-Phase Induction Motor with Modified Direct Torque Control

Abstract

A modified hysteresis torque controller is introduced into the direct torque control scheme of a 5-phase open-end winding induction motor, aimed at enhancing steady-state performance by minimizing torque, flux ripple, and current total harmonic distortion (%THD) with the dual 5-leg inverter configuration. The proposed Direct Torque Control (DTC) strategy utilizes a common DC source for both converters without the need for a bulky isolation transformer, accomplished by nullifying common mode voltage in the dual inverter open-end winding configuration. This proposed technique employs 30 virtual voltage vectors (VVVs) generated from the dual inverter configuration, strategically categorized as small, large, and medium voltage vectors. These 30 VVVs are instrumental in forming a 7-level torque controller and a 3-level torque controller in the proposed DTC scheme. In contrast to the existing DTC method, which uses 20 virtual voltage vectors from a dual 5-leg inverter configuration and grapples with challenges like high current harmonic distortion, torque ripple, and flux ripple, the proposed control scheme introduces a new 7-level torque hysteresis controller. The outcome is reduced torque and flux ripple, along with minimized harmonic content across various speeds and loading conditions without disturbing the dynamics. Experimental hardware results are scrutinized, comparing the classical DTC with the proposed DTC schemes in open-end winding induction motors, aiming to know the superior qualities of the proposed control approach.