Dynamic commutation torque‐ripple reduction for brushless DC motor based on quasi‐Z‐source net

Abstract

The commutation torque ripple in the six-step square-wave driving mode of the brushless DC motor affects the motor performance and generates mechanical vibrations and noise when used for industrial applications. The cause of commutation torque ripple is analysed in this study and a non-linear transient model of the phase current during the commutation interval is developed. According to the transient-current model, the commutation voltage and the time required to produce a constant torque can be calculated without current sampling; this makes the control system easier to realise in industrial applications, and reduces the need for a high performance controller. Based on the pulsewith modulated chopping method and quasi-Z-source net, the proposed control system can adjust the motor speed using a constant-voltage power supply and reduce the commutation torque ripple over the entire speed-adjustable range. A torque transducer is used to measure the dynamic torque ripple in the experiment. The results show that the proposed commutation torque-ripple reduction strategy can reduce the dynamic torque ripple by about 70% in both simulation and experiment compared with the traditional driving methods. Torque ripple in BLDCM driving systemThe torque ripple of the BLDCM is formed by three components: cogging torque, reluctance torque and mutual torque [23]. Cogging torque is a common shortcoming in PM motors, and can be minimised during motor design. PM motors with surface mounted