Dynamic Behavior Assessment of Permanent Magnet Synchronous Motors Under Finite Set Model Predictive Controllers and Field-Oriented Control

Abstract

This paper presents an impartial comparison of the dynamic behavior of permanent magnet synchronous motors (PMSM) under three control techniques i.e., model predictive current control (MPCC), model predictive direct speed control (MPDSC) and field-oriented control (FOC). In MPCC, the voltage vectors applied to the inverter are determined by minimizing a cost function comprising the error in currents; whereas, in MPDSC, the voltage vectors applied to the inverter are determined according to minimization of cost function which includes speed and current errors. In MPCC, PI controller is used to regulate the speed, whereas in the MPDSC, there are no PI controllers. When the FOC is applied, modulated voltage vectors are determined according to three PI controllers for speed and current control. Most crucial implementation issues, which affects the dynamic performance of PMSMs, are addressed during the comparison between three control techniques. These issues include delay time, switching frequency and parameters mismatch. The delay time, due to the large number of calculations, is compensated by predicting the state variables two sampling intervals ahead. Switching frequency is included in the objective function to reduce switching losses. The effect of delay time and switching frequency is related to MPCC and MPDSC; meanwhile parameters mismatch is associated with all control methods. The dynamic behaviors are assessed via simulation results at different load conditions. The final evaluation was performed in terms of rising time, settling time, total harmonic distortion and average switching frequency.