Commutation Torque Ripple Reduction for Direct DC-link Current Control by Applying Multilevel Hysteresis Controller and Proper Voltage Vectors

To achieve high-performance control of the brushless direct current (BLDC) motors, a direct DC-link current control (DDLCC) is introduced and compared with the direct torque control (DTC) method. Similar to the DTC method, the proposed DDLCC method has a fast transient response; nonetheless, it comes with higher reliability, cost-effectiveness, and lower torque ripple. Although this method provides average torque ripples lower than those of the DTC method, the commutation torque ripple is higher. A four-level hysteresis controller is utilized to distinguish the commutations, and then, the commutation torque ripple is suppressed by applying appropriate voltage vectors. These vectors provide similar fall time and rise time for both commutated currents and suppress commutation torque ripple. The results verify these appropriate voltage vectors guarantee the stable performance of the BLDC motor as well as commutation torque ripple reduction compared to the conventional DTC method.