Comparison of DC/DC Converters in DCM for Reducing Low-Frequency Input Current Ripple of Single-Phase Two-Stage Inverters

ABSTRACT

DC/DC Converters  Single-phase two-stage inverters generally use an intermediate capacitor to buffer the power imbalance between DC input and AC output. However, the resultant low-frequency voltage ripple on this intermediate capacitor may produce low frequency ripple at the source side, especially when the front-end dc/dc converter operates in continuous conduction mode (CCM). Some common solutions to reducing this ripple are feed forward control and power decoupling circuits. Alternatively, this paper analyzes a two-stage inverter where the front-end is a dc/dc converter operating in discontinuous conduction mode (DCM). In general dc/dc converters operating in DCM have inherent natural capability to reduce this low-frequency input current ripple, without needing a sophisticated control or complex circuitry as compared with its CCM operation. Analysis with simulation verification is reported to demonstrate such capability.

KEYWORDS

  1. Dc/ac
  2. Low-frequency ripple
  3. Single-phase
  4. Two stage

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

dc/dc converters

Fig. 1. A simplified power-stage diagram of a single-phase two-stage inverter.

EXPECTED SIMULATION RESULTS

comparison dc dc converters

  • (a) CCM operation: _vin = 3:3V

  • comparison dc dc converters

(b) DCM operation: _vin = 0:88V

Fig. 2. DCM boost front-end converter has lower voltage ripple than CCM.

comparison dc dc converters

Fig. 3. DCM buck-boost front-end converter does not contain low-frequency ripple but only high-frequency ripple.

comparison dc dc converters                                               Fig. 4. SEPIC front-end converter operating in DCM+CCM contains negligible

low-frequency ripple but only high-frequency ripple.

comparison dc dc converters

Fig. 5. High-gain front-end converter operating in DCM does contains

significant low-frequency ripple.

CONCLUSION

This paper analyzes basic and several higher-order front-end dc/dc converters for single-phase two-stage inverter design. Through inspecting the instantaneous average input current of those converters in discontinuous conduction mode (DCM), it has confirmed that buck-boost converter and buck-boost derived converters such as ZETA are free of low-frequency (mainly double ac line frequency) input current ripple due to the lack of direct connection between input and output during switching actions. For boost converter based converters such as SEPIC and C´ uk converters, their input currents contain lower low-frequency content thanks to the cascaded design. For boost converter based high voltage gain converters, its input current may not necessarily reduce the low-frequency content effectively. It depends on how the high-gain sub circuit is constructed and interacts with the input inductor. Further research is necessary to identify suitable converter topologies which have both smooth input current and low frequency content.

REFERENCES

[1] K. Fukushima, I. Norigoe, M. Shoyama, T. Ninomiya, Y. Harada, and K. Tsukakoshi, “Input Current-Ripple Consideration for the Pulse-link DC-AC Converter for Fuel Cells by Small Series LC Circuit,” in 2009 Twenty-Fourth Annual IEEE Applied Power Electronics Conference and Exposition, Feb 2009, pp. 447–451.

[2] L. Jianguo, H. Wenbin, Y. Kai, L. Xiaoyu, W. Fuyun, and W. Junji, “Research on input current ripple reduction of two-stage single-phase PV grid inverter,” in 2014 16th European Conference on Power Electronics and Applications, Aug 2014, pp. 1–8.

[3] B. Ge, Y. Liu, H. Abu-Rub, R. S. Balog, F. Z. Peng, S. McConnell, and X. Li, “Current Ripple Damping Control to Minimize Impedance Network for Single-Phase Quasi-Z Source Inverter System,” IEEE Transactions on Industrial Informatics, vol. 12, no. 3, pp. 1043–1054,

June 2016.

[4] Y. Zhou, H. Li, and H. Li, “A Single-Phase PV Quasi-Z-Source Inverter With Reduced Capacitance Using Modified Modulation and Double- Frequency Ripple Suppression Control,” IEEE Transactions on Power Electronics, vol. 31, no. 3, pp. 2166–2173, March 2016.

[5] D. B. W. Abeywardana, B. Hredzak, and V. G. Agelidis, “An Input Current Feedback Method to Mitigate the DC-Side Low-Frequency Ripple Current in a Single-Phase Boost Inverter,” IEEE Transactions on Power Electronics, vol. 31, no. 6, pp. 4594–4603, June 2016.

[6] H. Hu, S. Harb, N. Kutkut, I. Batarseh, and Z. J. Shen, “A Review of Power Decoupling Techniques for Microinverters With Three Different Decoupling Capacitor Locations in PV Systems,” IEEE Transactions on Power Electronics, vol. 28, no. 6, pp. 2711–2726, June 2013.
[7] M. A. Vitorino, L. F. S. Alves, R. Wang, and M. B. de Rossiter Corrła, “Low-Frequency Power Decoupling in Single-Phase Applications: A Comprehensive Overview,” IEEE Transactions on Power Electronics, vol. 32, no. 4, pp. 2892–2912, April 2017.
[8] Z. Chao, H. Xiangning, and Z. Dean, “Design and control of a novel module integrated converter with power pulsation decoupling for photovoltaic system,” in 2008 International Conference on Electrical Machines and Systems, Oct 2008, pp. 2637–2639.
[9] D. Debnath and K. Chatterjee, “A buck-boost integrated full bridge inverter for solar photovoltaic based standalone system,” in 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), June 2013, pp. 2867– 2872.
[10] J. Kan, S. Xie, Y. Wu, Y. Tang, Z. Yao, and R. Chen, “Single-Stage and Boost-Voltage Grid-Connected Inverter for Fuel-Cell Generation System,” IEEE Transactions on Industrial Electronics, vol. 62, no. 9, pp. 5480–5490, Sept 2015.
[11] D. Zhou, “Synthesis of PWM dc-to-dc power converters,” Ph.D. dissertation, California Institute of Technology, Pasadena, California, 1996.

 

Reducing Torque Ripple of Brushless DC Motor by Varying Input Voltage

 

ABSTRACT

This paper presents the method of reducing torque ripple of brushless direct current (BLDC) motor. In the BLDC motor, the torque ripple is decided by the back-electromotive force (EMF) and current waveform. If the back-EMF is constant in the conduction region of current, the torque ripple depends on the current ripple. The period of freewheeling region in the conduction region can be acquired by circuit analysis using the Laplace transformation and the torque ripple can be also reduced by varying input voltage to reduce the current ripple. The suggested method to reduce the torque ripple is confirmed by the dynamic simulation with the parameters of 500W BLDC motor.

KEYWORDS

  1. BLDC motor
  2. Current ripple
  3. Torque ripple
  4. Varying input voltage

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. PWM inverter and equivalent circuit of BLDC motor

EXPECTED SIMULATION RESULTS

Fig. 2. Back-EMF of 500 W BLDC motor at 6660 rpm.

Fig. 3. Current waveform of 500 W BLDC motor at 6660 rpm. (a) Experimental data. (b) Simulation data.

Fig. 4. Current and torque waveform in simulation. (a) Constant input voltage.

(b) Various input voltage..

 

CONCLUSION

This paper presents the method of reducing torque ripple of the BLDC motor by varying the input voltage after circuit analysis using the Laplace transformation. In the simulation confirmed by experiment, the torque ripple is reduced to 10%. The 500WBLDC motor used for simulation and experiment dose not have a trapezoidal back-EMF waveform but a sinusoidal back-EMF waveform. So the torque ripple is not reduced conspicuously, although the current ripple is reduced conspicuously, and produced torque ripple waveform is similar to the back-EMF waveform of 500 W BLDC motor.

REFERENCES

[1] 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.

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

[3] J. R. Hendershot Jr. and T. Miller, “Design of brushless permanent magnet motor,” in Oxford Magna Physics, 1st ed., 1994.

[4] P. Pillay and R. Krishnan, “Modeling, simulation, and analysis a permanent magnet brushless dc motor drive,” in Conf. Rec. 1987 IEEE IAS Annu. Meeting, San Diego, CA, Oct. 1–5, 1989, pp. 7–14.

[5] R. Carlson, M. Lajoie-Mazenc, and J. C. dos Fagundes, “Analsys of torque ripple due to phase commutation in brushless dc machines,” IEEE Trans. Ind. Appl., vol. 28, no. 3, pp. 632–638.