Discrete sliding mode control based on exponential reaching law and time delay estimation for an asymmetrical six‐phase induction machine drive

Abstract

This study deals with the problem of controlling rotor speed and stator currents of an asymmetrical six-phase induction machine with uncertain dynamics, disturbances, and unmeasurable rotor currents and proposes a robust non-linear variable structure controller. First of all, an outer control loop based on a proportional-integral regulator is performed to control the rotor speed and to construct the desired stator current references. Then, the inner loop is performed based on the proposed method that combines the time delay estimation method and discrete sliding mode control based on exponential reaching law. This structure allows an accurate and simple estimation of uncertainties and rotor currents, a high-tracking precision, a convergence of the stator currents to their known desired references in finite-time and chattering reduction. The design procedure is detailed step by step and the stability analysis and the convergence time are established for the current closedloop system. Experimental work was carried out on an asymmetrical six-phase induction motor drive to show the effectiveness and performance of the proposed robust non-linear discrete method. The results obtained highlighted the good tracking performance of the stator currents.

Discrete Terminal Super-Twisting Current Control of a Six-Phase Induction Motor

“…Consider the mathematical model of the asymmetrical six-phase IM powered by six-leg VSC [17,18] represented in Figure 1:…”

“…In the literature, earlier works considered similar methods applied to three-phase motors and proposed the extended version of the Proportional-Integral (PI) regulator [8], direct torque control [9], model predictive control [10,11], and others. Recently, advanced digital platforms encouraged the researchers to apply advanced intelligent and nonlinear control techniques such as fuzzy logic [12,13], nonlinear backstepping [14,15], Sliding Mode (SM) control [16][17][18], and others. Among the abovementioned methods, SM control is simply designed and is considered the most effective due to its good features that can be resumed by the following points [19]:…”

“…To enhance the DQSM performance and to reduce the Quasi Sliding Mode Band (QSMB), a combination of the Time-Delay Estimation (TDE) method with DQSM based on exponential reaching law has been proposed for an asymmetrical six-phase Induction Motor (IM) [18]. This method aims to reproduce approximated signals to unmeasurable rotor currents and matched uncertainties and perturbations based on time-delayed computed voltages and measured states to minimize the choice of switching gains.…”

“…However, a dilemma arose: small switching gains reduce chattering but deteriorate the tracking performance while large switching gains increase simultaneously the chattering level and the tracking accuracy but degrade the quality of electric energy (i.e., total harmonic distortion becomes high). This dilemma has been revealed through experimental works on a real six-phase IM using Gao's reaching law and exponential reaching law [17,18].…”

Discrete Sliding Mode Control Design for Bilateral Teleoperation System via Adaptive Extended State Observer

“…Therefore, the design of discrete sliding mode control (DSMC) has attracted a lot of attention in recent years. There are also some contributions in the area of DSMC such as [ 19 ]. Better performance could be guaranteed by considering a sampling period in the design phase, even if the sampling period was quite long [ 20 ].…”