Saturation controller-based ripple reduction for direct torque controlled permanent-magnet synchronous machines

This paper proposes a novel direct torque control (DTC) scheme to reduce the torque and stator flux ripples for permanent-magnet synchronous motor (PMSM) drives using a relatively low sampling frequency. Unlike the conventional DTC in which the voltage vectors are determined by hysteresis controllers, the proposed DTC uses nonlinear saturation comparators and a duty ratio modulation scheme for switch selection and switching duration determination. Compared to the conventional DTC, the proposed DTC scheme significantly reduces the steady-state torque and flux ripples of PMSMs while preserving most of the intrinsic properties of the conventional DTC, e.g. fast dynamic, robust to disturbances, no coordinate transformation, etc. The effectiveness of the proposed DTC scheme is verified by simulation and experimental results on a 200W PMSM drive system.