Nonlinear Stability Analysis of Fully Controlled Permanent Magnet Synchronous Machines

Permanent magnet synchronous machine (PMSM), fed by power electronic converters has recently received increased attention in many industrial drive applications. The challenging issue of modeling such a system and analyzing its performance and stability with the controllers' fast dynamics taken into account, is extensively addressed in this paper. Based on the accurate nonlinear PMSM/frequency-converter description and adopting the familiar to the industrial engineers simple proportional-integral (PI) controller structure, the commonly used inner-loop current controllers are incorporated into the model and an advanced, Lyapunov-based, nonlinear procedure is developed. Using this procedure, the analysis of the closed-loop system proves input-to-state stability (ISS) and convergence to the equilibrium. Thus, the massive and rigorous theoretical analysis constitutes the main contribution of the present work that effectively solves the open problem of guaranteeing global stability of the entire system when commonly used controllers are applied, regardless of the particular drive strategies, system parameters and operating conditions.