A current control scheme with an adaptive internal model for robust current regulation and torque ripple minimization in PMSM vector drive

This paper addresses the problem of uncertainties in practical permanent magnet synchronous motors (PMSMs), and proposes a simple adaptive internal model within the current feedback structure as a solution. Due to the time varying nature and the high bandwidth property of uncertainties in a practical PMSM drive system, the internal model is simply chosen as the estimated uncertainty function, which adaptively varies with different operating conditions. Subsequently, the frequency modes of the uncertainty function are embedded in the control effort, and a robust current control performance is yielded. Furthermore, the inclusion of the estimated uncertainty function provides an efficient solution for torque ripple minimization in PMSM drives. This is because the frequency modes of the disturbances to be eliminated i.e., the flux harmonics, are included in the stable closed loop system. As a result, the controller can introduce a very high attenuation gains at different frequency modes corresponding to the flux harmonics. To provide a high bandwidth estimate of the uncertainty function, a simple adaptation law is derived, in the sense of Lyapunov functions, using the nominal current dynamics. Comparative evaluation results are presented to demonstrate the effectiveness of the proposed control scheme under different operating conditions.