This study proposes a novel topology for reducing commutation torque ripple in a brushless DC motor (BLDCM) drive system using a three-level neutral-point-clamped (NPC) inverter combined with single-ended primary-inductor converter (SEPIC) converters. In the BLDCM, current ripples arise because of the influence of stator winding inductance, which generates torque ripples. The torque ripple that is generated in the commutation period prevents the use of BLDCM in high-precision servo drive systems. In this study, two-stage converters are proposed to reduce the torque ripple. The first stage consists of two SEPIC converters to obtain the desired commutation voltage according to motor speed. A dc-link voltage selection circuit is combined with the SEPIC converters to apply the optimised voltage during the commutation interval. To reduce the torque ripple further, a three-level NPC inverter is used to apply a half dc-link voltage across the motor winding and this effectively reduces the torque ripple. Experimental results show that the proposed topology is able to reduce commutation torque ripple significantly under both low-speed and high-speed operation.
Fig. 1 Simulation block diagram of the proposed topology with the BLDCM
EXPECTED SIMULATION RESULTS:
Fig. 2 Simulation results of phase current and torque a Phase current waveform of the conventional control at 3000 rpm and 0.825 Nm b Torque waveform of the conventional control at 3000 rpm and 0.825 Nm c Phase current waveform of the proposed topology at 3000 rpm and 0.825 Nm d Torque waveform of the proposed topology at 3000 rpm and 0.825 Nm
Fig. 3 Simulation results of phase current and torque a Phase current waveform of the conventional control at 6000 rpm and 0.825 Nm b Torque waveform of the conventional control at 6000 rpm and 0.825 Nm c Phase current waveform of the proposed topology at 6000 rpm and 0.825 Nm d Torque waveform of the proposed topology at 6000 rpm and 0.825 Nm
In this paper, a novel topology has been proposed to suppress the commutation torque ripple of a BLDCM using two SEPIC converters and a MOSFET-based three-level NPC inverter. The SEPIC converters are used to adjust the dc-link voltage and thus to suppress the torque ripple during the commutation period. To verify the feasibility of the proposed topology, simulation and experiments were conducted using low and high speeds. The results of this paper have demonstrated that the proposed topology can effectively reduce the commutation torque ripple. Therefore, the proposed solution has high potential for vehicular and aerospace applications in which torque ripple minimization is of great importance.
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