Comparison of Performance of Brushless DC Drives under Direct Torque Control and PWM Current Control

Direct torque control (DTC) was originally successfully developed for induction machine drives, and, more recently, to permanent magnet brushless AC (BLAC) drives. In this paper, the performance of DTC controlled brushless DC (BLDC) drives is compared with that of PWM current controlled BLDC drives with and without current shaping. The paper reports the simulation and experimental investigation, as well as the analysis of torque waveforms and torque ripples. It shows that, in addition to well-known fast torque response, the DTC controlled BLDC drive exhibits significantly less low-frequency torque ripples than the PWM current controlled BLDC drive without current shaping, while it is easier to implement than the PWM current controlled BLDC drive with current shaping