An Improved Sliding-Mode Current Control of Induction Machine in Presence of Voltage Constraints

Abstract

This article proposes a novel approach to design sliding-mode control (SMC) for an induction motor (IM) in the presence of operational constraints. Different from the traditional techniques in SMC, the proposed method assumes the existence of a constant input disturbance and incorporates it in the switching current control law. Effectively, this leads to integral action through disturbance estimation together with an antiwindup mechanism naturally occurring when the control signal reaches its operational limits. The finite-time convergence of the SMC law is established through a Lyapunov analysis. Experimental evaluations are performed on an industrial-sized IM, where the current dynamics of the motor are controlled using SMC, and a velocity proportional–integral (PI) controller is used for the outer-loop control system. Experimental results reveal that the proposed sliding-mode current control systems provide much improved closed-loop control performance over the traditional SMC system. Further comparative experimental studies with well-designed PI current controllers provide insight into the characteristics of the proposed current control systems.