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

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 and reference current generation 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. To provide a high bandwidth estimate of the uncertainty function with high-noise immunity, a simple adaptation law is derived, in the sense of Lyapunov functions, using the nominal current dynamics. The inclusion of the frequency modes of the disturbances to be eliminated (the flux harmonics and voltage disturbances caused by parameter variation) in the stable closed-loop system introduces very high-attenuation at different frequency modes corresponding to uncertainty modes. Therefore, a robust torque ripple minimization and current regulation performances are yielded. To properly tune the proposed scheme, a stability analysis based on a discrete-time Lyapunov function has been used to determine the stability limits of the adaptation gain. Comparative evaluation results are presented to demonstrate the effectiveness of the proposed control scheme under different operating conditions.