Commutation Torque Ripple Suppression Strategy for Brushless DC Motors With a Novel Non-inductive Boost Front End
Abstract
This paper firstly presents a novel boost front end simply with a diode, a MOSFET and a DC-link capacitor. Without extra inductors or other power components, the boost font end could boost the capacitor voltage with the motor stator inductances, thus reducing the influence of the limited DC-link voltage on commutation torque ripple reduction to a large extent. A unified commutation torque ripple suppression strategy is further proposed with the front end adopted based on the analysis about the effects of four switching vectors on motor speed regulation and DC-link capacitor voltage regulation. The proposed strategy can boost the DC-link capacitor voltage via properly selection of switching vectors under the premise of guaranteeing normal speed regulation in non-commutation period, and reduce both the commutation torque ripple and commutation time by two consistent switching vectors with the boosted DC-link capacitor voltage in commutation period. Finally, the proposed method is theoretically analyzed with respect to the capacitance selection and the boot capacity of NIBFE. The correctness of the analysis and the effectiveness of the presented method are validated by the experimental results.
EXISTING SYSTEM:
The commutation torque ripple suppression has been intensively studied in recent years. The pulse width modulation (PWM) on the non-commutation phase is employed to keep the average terminal voltage constant during the commutation process via voltage disturbance compensation. As this method is not suitable for the motor operation in the high-speed region below the rated speed, many scholars pay their attention to the commutation torque ripple suppression over the full speed range. A method with a single DC current sensor is proposed in which the full speed range below the rated speed is divided into the high-speed region and the low-speed region, and different modulation strategies are used accordingly during the commutation process to keep the current slope of the in-coming phase equal to that of the out-going phase with the voltage compensation method three-segment modulation strategy is presented to reduce the commutation torque ripple, which divides each PWM period into three segments and analyzes the duration of each segment according to both minimum commutation time and constant non-commutation phase current. Based on the analysis results, the modulation on non-commutation phase in the low-speed region and out-going phase in the high-speed region are selected respectively. Two-phase and three-phase switching modes are employed in the low-speed region and the high-speed region respectively, and the integral variable structure controller is used to enhance the robustness of the commutation torque ripple supersession. However, different modulation strategies need to be switched between the low-speed and the high-speed regions in the above papers. When the motor operates near the switching condition, the frequent switching caused by the speed fluctuation may reduce the stability of the system. In order to reduce the commutation torque ripple in the full speed range with a unified control strategy, direct torque control method is employed, which can adaptively select the switching mode required in the commutation period based on the torque error.
PROPOSED SYSTEM:
In this paper, unified commutation torque ripple suppression is proposed with a designed non-inductive boost front end. Section II firstly analyze the effects of different switching vectors on the motor input voltage and NIBFE’s capacitor voltage. The commutation torque ripple can also be reduced by regulating the DC-link voltage, where the circuit with the Laplace transformation is analyzed in and the DC-DC converters are added to solve the restriction of limited DC-link voltage on the rapid change of the phase currents during the commutation process in. The SEPIC converter is employed to adjust the voltage required in the commutation period, where the DC source and the SEPIC converter are selected to supply the motor during the non-commutation and the commutation periods respectively. A novel topology is proposed in with SEPIC converter to adjust the commutation voltage to suppress the commutation torque ripple and a three-level neutral-point-clamped (NPC) inverter to generate lower harmonics to reduce the converter loss. A Cuk converter is presented to reduce the commutation torque ripple in, where two operation modes are employed to regulate the voltage during the non-commutation and the commutation period respectively. Z-source converter is added , where the shoot-through vector is introduced to boost the DC-link voltage so that a unified modulation strategy can be used to suppress the commutation torque ripple over the entire speed range. However, lots of power switches and additional inductors are required in these DC-DC converters, which greatly increases both the size and cost of the motor drive system.
CONCLUSION
In this paper, a unified commutation torque ripple suppression strategy is proposed with the designed non-inductive boost front end. The proposed control strategy has the following advantages: a) The structure of the proposed NIBFE is simple, saving the drive system size and cost. With fewer components and no additional inductors, the voltage boost capacity is achieved by the use of the motor stator inductance. b) The proposed boost topology solves the influence of the limited DC-link voltage on the commutation torque ripple suppression. Under the combined action of the boosted voltage and the selected switching vectors, it is possible to suppress the commutation torque ripple and shorten the commutation process at the same time, thus improves the system stability. c) A unified commutation torque ripple suppression strategy is employed, saving the need to switch the different control strategies according to the motor speed. In addition, the proposed control strategy with NIBFE can also be applied to the bidirectional DC source by replacing the DC-link diode with a MOSFET, which will be further studied in the future.
REFERENCES
[1] Z. Q. Zhu and D. Howe, “Electrical machines and drives for electric, hybrid, and fuel cell vehicles,” Proc. IEEE, vol. 95, no. 4, pp. 746–765, Apr. 2007.
[2] H. Li, S. Zheng and H. Ren, “Self-Correction of Commutation Point for High-Speed Sensorless BLDC Motor With Low Inductance and Nonideal Back EMF,” IEEE Trans. Power Electron., vol. 32, no. 1, pp. 642-651, Jan. 2017.
[3] C. L. Xia, G. K. Jiang, W. Chen, and T. N. Shi, “Switching-Gain Adaption Current Control for Brushless DC Motors,” IEEE Trans. Ind. Electron., vol. 63, no. 4, pp. 2044-2052, Apr. 2016
[4] A. C. Lee, S. Wang and C. J. Fan, “A Current Index Approach to Compensate Commutation Phase Error for Sensorless Brushless DC Mot ors Wi t h Noni deal Back EMF, ” IEEE Trans. Power Electron., vol. 31, no. 6, pp. 4389-4399, June 2016.
[5] R. Carlson, M. Lajoie-Mazenc and J. C. d. S. Fagundes, “Analysis of torque ripple due to phase commutation in brushless DC machines,” IEEE Trans. Ind. Appl., vol. 28, no. 3, pp. 632-638, May/Jun. 1992.
[6] Z. Zhu and J. H. Leong, “Analysis and mitigation of torsional vibration of PM brushless ac/DC drives with direct torque controller,” IEEE Trans. Ind. Appl., vol. 48, no. 4, pp. 1296–1306, Jul./Aug. 2012.
[7] D. Kim, K. Lee and B. Kwon, “Commutation torque ripple reduction in a position sensorless brushless DC motor drive,” IEEE Trans. Power Electron., vol. 21, no. 6, pp. 1762-1768, Nov. 2006.
[8] J. H. Song and I. Choy, “Commutation torque ripple reduction in brushless DC motor drives using a single DC current sensor,” IEEE Trans. Power Electron., vol. 19, no. 2, pp. 312–319, Mar. 2004.
[9] J. Shi and T. Li, “New method to eliminate commutation torque ripple of brushless DC motor with minimum commutation time,” IEEE Trans. Ind. Electron., vol. 60, no. 6, pp. 2139–2146, Jun. 2013.
[10] C. L. Xia, Y. Xiao, W. Chen, and T. Shi, “Torque ripple reduction in brushless DC drives based on reference current optimization using integral variable structure control,” IEEE Trans. Ind. Electron., vol. 61, no. 2, pp. 738–752, Feb. 2014.