Direct torque control of brushless DC motor drives with improved reliability

Currently, road vehicles are more and more equipped by PM synchronous motors. Of particular interest are brushless DC (BLDC) motors with their low resolution encoder make it feasible their integration in a large scale industry such as the automotive one. Within this trend, the paper deals with the synthesis and implementation of a new DTC strategy dedicated to the control of BLDC motor drives. Compared to the most recent and high-performance DTC strategy, the proposed one offers an improved reliability thanks to the achievement of a balanced switching frequencies of the inverter upper and lower IGBTs, on one hand, and the reduction of the average value of the motor common mode voltage, on the other hand. Furthermore, the torque ripple is significantly damped during sequence-to-sequence commutations using a three-level hysteresis torque controller. An experimentally-based comparative study between the most recent and high-performance DTC strategy and the introduced one clearly highlights the potentialities exhibited by the latter.