**ABSTRACT:**

This paper presents a new power converter topology to suppress the torque ripple due to the phase current commutation of a brushless DC motor (BLDCM) drive system. A combination of a 3-level diode clamped multilevel inverter (3-level DCMLI), a modified single-ended primary-inductor converter (SEPIC), and a dc-bus voltage selector circuit are employed in the proposed torque ripple suppression circuit. For efficient suppression of torque pulsation, the dc-bus voltage selector circuit is used to apply the regulated dc-bus voltage from the modified SEPIC converter during the commutation interval. In order to further mitigate the torque ripple pulsation, the 3-level DCMLI is used in the proposed circuit. Finally, simulation and experimental results show that the proposed topology is an attractive option to reduce the commutation torque ripple significantly at low and high speed applications.

**KEYWORDS:**

- Brushless direct current motor (BLDCM),
- Dc-bus voltage control
- Modified single-ended primary-inductor converter
- Level diode clamped multilevel inverter (3-level DCMLI)
- Torque ripple

** ****SOFTWARE:** MATLAB/SIMULINK

**CIRCUIT DIAGRAM:**

** **

Fig. 1. Proposed converter topology with a dc-bus voltage selector circuit for BLDCM

** EXPECTED SIMULATION RESULTS:**

** **

Fig. 2. Simulated waveforms of phase current and torque at 1000 rpm and 0.825 Nm with 5 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology.

Fig. 3 Simulated waveforms of phase current and torque at 6000 rpm and 0.825 Nm with 5 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology.

Fig. 4 Simulated waveforms of phase current and torque at 1000 rpm and 0.825 Nm with 20 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and switch a selection circuit. (d) BLDCM fed by proposed topology.

Fig. 5 Simulated waveforms of phase current and torque at 6000 rpm and 0.825 Nm with 20 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology

Fig. 6. Simulated waveforms of phase current and torque at 1000 rpm and 0.825 Nm with 80 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology.

Fig. 7 Simulated waveforms of phase current and torque at 6000 rpm and 0.825 Nm with 80 kHz switching frequency. (a) BLDCM fed by 2-level inverter. (b) BLDCM fed by 3-level DCMLI. (c) BLDCM fed by 2-level inverter with SEPIC converter and a switch selection circuit. (d) BLDCM fed by proposed topology

**CONCLUSION:**

In this paper, a commutation torque ripple reduction circuit has been proposed using 3-level DCMLI with modified SEPIC converter and a dc-bus voltage selector circuit. A laboratory-built drive system has been tested to verify the proposed converter topology. The suggested dc-bus voltage control strategy is more effective in torque ripple reduction in the commutation interval. The proposed topology accomplishes the successful reduction of torque ripple in the commutation period and experimental results are presented to compare the performance of the proposed control technique with the conventional 2-level inverter, 3-level DCMLI, 2-level inverter with SEPIC converter and the switch selection circuit-fed BLDCM. In order to obtain significant torque ripple suppression, quietness and higher efficiency, 3-level DCMLI with modified SEPIC converter and the voltage selector circuit is a most suitable choice to obtain high-performance operation of BLDCM. The proposed topology may be used for the torque ripple suppression of BLDCM with the very low stator winding inductance.

**REFERENCES:**

[1] N. Milivojevic, M. Krishnamurthy, Y. Gurkaynak, A. Sathyan, Y.-J. Lee, and A. Emadi, “Stability analysis of FPGA-based control of brushless DC motors and generators using digital PWM technique,” IEEE Trans. Ind. Electron., vol. 59, no. 1, pp. 343–351, Jan. 2012.

[2] X. Huang, A. Goodman, C. Gerada, Y. Fang, and Q. Lu, “A single sided matrix converter drive for a brushless dc motor in aerospace applications,” IEEE Trans. Ind. Electron., vol. 59, no. 9, pp. 3542–3552, Sep. 2012.

[3] X. Huang, A. Goodman, C. Gerada, Y. Fang, and Q. Lu, “Design of a five-phase brushless DC motor for a safety critical aerospace application,” IEEE Trans. Ind. Electron., vol. 59, no. 9, pp. 3532-3541, Sep. 2012.

[4] J.-G. Lee, C.-S. Park, J.-J. Lee, G. H. Lee, H.-I. Cho, and J.-P. Hong, “Characteristic analysis of brushless motor condering drive type,” KIEE, pp. 589-591, Jul. 2002.

[5] T. H. Kim and M. Ehsani, “Sensorless control of BLDC motors from near-zero to high speeds,” IEEE Trans. Power Electron., vol. 19, no. 6, pp. 1635–1645, Nov. 2004.