Reduction of Stator Flux Ripple and Current Harmonic Distortion using Constant Switching Flux Controller-based DTC of Five-Phase Induction Motor

A five-phase induction motor's classical hysteresis-based DTC exhibits excellent dynamics and suffers from higher torque and flux ripple, higher current %THD, and variable switching frequencies that vary with speed. In this article, a triangular-based constant switching flux (CSF) controller is introduced in place of the standard hysteresis-based flux controller without altering the hysteresis-based torque controller for implementing the lookup table-based direct torque control of a five-phase induction motor. The proposed DTC scheme improves the average flux ripple and current harmonic distortion for all operating speeds without altering the superior speed and torque dynamic characteristics as that of the classical DTC scheme. The proposed carrier-based CSF controller smoothens the flux pattern and in turn, improves the current profile with suitable duty variations. The proposed DTC forces flux status change at regular intervals which eliminates the drooping of stator flux under very low speeds and light load cases. The hardware and simulation experimental results are analyzed to know the effectiveness of the proposed constant switching flux controller-hysteresis torque controller-based DTC (CSFHTC-DTC) control scheme over the classical hysteresis flux and hysteresis torque controller-based DTC (HFT-DTC) control scheme with the same lookup table.