This study investigates the torque ripple performance of brushless DC (BLDC) motor drive system by integrating both modified single-ended primary inductor converter (SEPIC) and silicon carbide metal–oxide–semiconductor field-effect transistor based three-level neutral-point-clamped (NPC) inverter. In BLDC motor, the high commutation torque ripple is an important origin of vibration, speed ripple and prevents the use of the BLDC motor drive system in high-performance and high-precision applications. For torque ripple reduction, the modified SEPIC converter is employed at the entrance of the three-level NPC inverter, which regulates the DC-link voltage according to the motor speed. Moreover, the three-level NPC inverter is employed as a second-stage converter to suppress current ripple for further torque ripple reduction. Finally, the performance of the proposed hybrid converter topology is verified by simulation and laboratory experimental results.
(a) Proposed converter topology
EXPECTED SIMULATION RESULTS
Fig. 2 Phase current and torque waveforms
(a) Phase current and torque waveforms from simulation at 2500 rpm and 0.825 N m, (b) Phase current and torque waveforms from simulation at 2500 rpm and 0.825 N m, (c) Phase current and torque waveforms from simulation at 6000 rpm and 0.825 N m, (d) Phase current and torque waveforms from simulation at 6000 rpm and 0.825 N m
A novel hybrid circuit topology has been proposed in this paperwhich is built by a modified SEPIC converter and a SiC-MOSFETbasedthree-level NPC converter for minimising torque ripple in aBLDC motor drive system. For efficient reduction of torque ripple,the first stage is the modified SEPIC converter that lifts the DClinkvoltage to the desired value based on the motor speedmeasurement. For further torque ripple reduction, the three-levelNPC inverter is employed as the second-stage converter tosuppress current ripple. Experimental results show that theproposed hybrid converter topology can suppress the torque rippleto 14.6% at the speed of 6000 rpm, commutation torque ripple isreduced substantially and produce smooth torque waveform thanthe BLDC motor driven by the two-level, three-level NPC, twolevelinverter with DC-link voltage control, and two-level inverterwith SEPIC converter and switch selection circuit topologies.
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