Time Delay Estimation based Discrete-Time Super-Twisting Current Control for a Six-Phase Induction Motor

In this paper, the problem of high-accuracy stator currents tracking of a six-phase induction motor in the presence of perturbations and unmeasurable rotor currents is tackled. Since the good features offered by sliding mode theory motivate the community of researchers on control, a time delay estimation based discrete-time super-twisting controller is proposed. First of all, an outer loop is performed to regulate the speed and to construct the desired stator currents. Then, the inner loop, based on an indirect rotor field-oriented control, is performed based on the proposed method. The proposed structure allows an accurate and simple estimation of uncertainties and rotor currents, a good tracking, a fast convergence of the currents tracking error to a neighbour of zero. The design procedure and the stability analysis are detailed for the current closed-loop system. Experimental work was carried out on a six-phase induction motor to demonstrate the effectiveness of the developed discrete approach. In addition, the performances obtained are compared to the ones obtained using the discrete-time sliding mode with time delay estimation. The results obtained highlighted the satisfactory stator currents tracking performance in steady-state and transient conditions and under different sampling times, parameters mismatch and with load and no-load conditions.