Torque Ripple Suppression Based on a New Multi-level DTC Strategy

Under the traditional hysteresis control, three-level direct torque control (DTC), one voltage vector can be selected from only three voltage vectors in a direct torque control cycle of brushless DC motor (BLDCM), resulting in a large torque ripple. Therefore, this paper proposes a new inverter topology that can provide more levels. By analyzing all sorts of the equivalent circuits at different times, this new multi-level DTC strategy makes corresponding switching state selection tables during commutation and non-commutation, and adopts respectively four-level hysteresis and six-level hysteresis control. At the same time, the additional capacitors are adopted to supply power according to different switching states, and their voltages are equalized by selecting different switch states. The more levels due to capacitors can reduce the torque ripple of traditional scheme greatly, the new multi-level DTC strategy has good advantages of simple structure and easy implementation. The proposed control strategy is verified practicability and effectiveness by experiment and simulation.