Journal of Power Electronics

The Korean Institute of Power Electronics (전력전자학회)
권호 표지
DOI QR코드

DOI QR Code

Analyzing and Designing a Current Controller for Circulating Current Reduction in Parallel Three-Phase Voltage-Source Inverters

  • Kim, Kiryong (Department of Electrical Engineering, Pusan National University) ;
  • Shin, Dongsul (LG Electronics) ;
  • Kim, Hee-Je (Department of Electrical Engineering, Pusan National University) ;
  • Lee, Jong-Pil (Power Conversion Research Center, HVDC Research Division, KERI)
  • Received : 2017.01.05
  • Accepted : 2017.10.12
  • Published : 2018.03.20
Download PDF
⟨ Previous Next ⟩

Abstract

A circulating current is a major problem caused by directly connecting voltage-source inverters (VSIs) in parallel. This circulating current occurs as a zero-sequence current between the inverters by specific switch states. Several studies have presented alternatives using hardware and software methods. When coupled inductors (CIs) are employed for the high-frequency circulating current, a controller is required to prevent the low-frequency circulating current from saturating the CIs. In this study, the zero-sequence circulating current and its alternatives are investigated using hardware and mathematical description. A high-performance circulating current controller is proposed by applying a repetitive controller to the zero-sequence current control loop. The proposed controller can effectively minimize the low-frequency circulating current without any data sharing between the inverters in unfavorable conditions. It can also be applicable to the modular configuration of parallel three-phase VSIs. Experimental results verify the performance of the proposed controller.

Keywords

E1PWAX_2018_v18n2_502_f0001.png 이미지

Fig. 1. Direct parallel three-phase VSIs.

E1PWAX_2018_v18n2_502_f0002.png 이미지

Fig. 2. Path of the circulating current via lower switches ofinverter 1 and lower switches of inverter 2.

E1PWAX_2018_v18n2_502_f0003.png 이미지

Fig. 3. Path of the circulating current via upper switches of inverter1 and lower switches of inverter 2.

E1PWAX_2018_v18n2_502_f0004.png 이미지

Fig. 4. Single phase of directly connected parallel VSIs.

E1PWAX_2018_v18n2_502_f0005.png 이미지

Fig. 5. Methods for removing the path of the circulating current.

E1PWAX_2018_v18n2_502_f0006.png 이미지

Fig. 6. Simplified block diagrams of conventional closed-loopcurrent control in z-domain. (a) d-axis, (b) q-axis, and (c) z-axiscurrent control loops.

E1PWAX_2018_v18n2_502_f0007.png 이미지

Fig. 7. Proposed current controller for parallel three-phase VSIs.

E1PWAX_2018_v18n2_502_f0008.png 이미지

Fig. 8. Nyquist diagram of PI controller.

E1PWAX_2018_v18n2_502_f0009.png 이미지

Fig. 9. Proposed ZSCC control loop.

E1PWAX_2018_v18n2_502_f0010.png 이미지

Fig. 10. Trajectory of Rcl(z).

E1PWAX_2018_v18n2_502_f0011.png 이미지

Fig. 11. Simulated waveforms with conventional ZSCC. (a)Currents of inverters 1. (b) Currents of inverters 2. (c) Inverter 1and 2 currents in phase a. (d) ZSCC.

E1PWAX_2018_v18n2_502_f0012.png 이미지

Fig. 12. Simulated waveforms with the proposed ZSCC. (a)Currents of inverters 1. (b) Currents of inverters 2. (c) Inverter 1and 2 currents in phase a. (d) ZSCC.

E1PWAX_2018_v18n2_502_f0013.png 이미지

Fig. 13. Diagram of parallel three-phase VSIs with L filters.

E1PWAX_2018_v18n2_502_f0014.png 이미지

Fig. 14. Experimental result of the current waveforms. (a)Conventional controller. (b) Proposed controllers with thedifferent current references( * 1,inv di =30 A, 2,inv di =10 A) and filter *inductances(Lf1 = 2 mH and Lf1 = 3 mH).

E1PWAX_2018_v18n2_502_f0015.png 이미지

Fig. 15. Experimented current waveforms. (a) Conventionalcontroller. (b) Proposed controllers with the same current reference( * 1,inv di =30A, 2,inv di =30A) and different filter inductances(Lf1 = 2 *mH and Lf1 = 3 mH).

TABLE I SI BASE UNITS

E1PWAX_2018_v18n2_502_t0001.png 이미지

References

  1. R. Li and D. Xu, "Parallel operation of full power converters in permanent-magnet direct-drive wind power generation system," IEEE Trans. Ind. Electron., Vol. 60, No. 4, pp. 1619-1629, Apr. 2013. https://doi.org/10.1109/TIE.2011.2148684
  2. Z. Xu, R. Li, H. Zhu, D. Xu, and C. H. Zhang, "Control of parallel multiple converters for direct-drive permanentmagnet wind power generation systems," IEEE Trans. Power Electron., Vol. 27, No. 3, pp. 1259-1270, Mar. 2012. https://doi.org/10.1109/TPEL.2011.2165224
  3. C.-T. Pan and Y.-H. Liao, "Modeling and coordinate control of circulating currents in parallel three-phase boost rectifiers," IEEE Trans. Ind. Electron., Vol. 54, No. 2, pp. 825-838, Apr. 2007. https://doi.org/10.1109/TIE.2007.891776
  4. S. Ogasawara, J. Takagaki, H. Akagi, and A. Nabae, "A novel control scheme of a parallel current-controlled pwm inverter," IEEE Trans. Ind. Appl., Vol. 28, No. 5, pp. 1023-1030, Sep./Oct. 1992. https://doi.org/10.1109/28.158825
  5. T. Yoshikawa, H. Inaba, and T. Mine, "Analysis of parallel operation methods of pwm inverter sets for an ultra-high speed elevator," in Proc. IEEE 15th Annu. Appl. Power Electron. Conf. Expo., Vol. 2, pp. 944-950, 2000.
  6. Z. Ye, D. Boroyevich, J.-Y. Choi, and F. C. Lee, "Control of circulating current in two parallel three-phase boost rectifiers," IEEE Trans. Power Electron., Vol. 17, No. 5, pp. 609-615, Sep. 2002.
  7. T.P. Chen, "Dual-modulator compensation technique for parallel inverters using space-vector modulation," IEEE Trans. Ind. Electron., Vol. 56, No. 8, pp. 3004-3012, Aug. 2009. https://doi.org/10.1109/TIE.2009.2022515
  8. Z. Xueguang, C. Jiaming, M. Yan, W. Yijie, and X. Dianguo, "Bandwidth expansion method for circulating current control in parallel three-phase pwm converter connection system," IEEE Trans. Power Electron., Vol. 29, No. 12, pp. 6847-6856, Dec. 2014. https://doi.org/10.1109/TPEL.2014.2311046
  9. Z. Xueguang, Z. Wenjie, C. Jiaming, and X. Dianguo, "Deadbeat control strategy of circulating currents in parallel connection system of three-phase pwm converter," IEEE Trans. Energy Convers., Vol. 29, No. 2, pp. 406-417, Jun. 2014. https://doi.org/10.1109/TEC.2014.2297994
  10. L. Maharjan, T. Yamagishi, and H. Akagi, "Active-power control of individual converter cells for a battery energy storage system based on a multilevel cascade pwm converter," IEEE Trans. Power Electron., Vol. 27, No. 3, pp. 1099-1107, Mar. 2012. https://doi.org/10.1109/TPEL.2010.2059045
  11. J. P. Lee, B. D. Min, T. J. Kim, D. W. Yoo, and J. Y. Yoo, "A novel topology for photovoltaic DC/DC full-bridge converter with flat efficiency under wide PV module voltage and load range," IEEE Trans. Ind. Electron., Vol. 55, No. 7, pp. 2655-2663, Jul. 2008. https://doi.org/10.1109/TIE.2008.924165
  12. B. D. Min, J. P. Lee, J. H. Kim, T. J. Kim, D. W. Yoo, and E. H. Song, "A new topology with high efficiency throughout all load range for photovoltaic PCS," IEEE Trans. Ind. Electron., Vol. 56, No. 11, pp. 4427-4435, Nov. 2009 https://doi.org/10.1109/TIE.2008.928098
  13. J. P. Lee, B. D. Min, and D. W. Yoo, "Implementation of a high efficiency grid-tied multi-level photovoltaic power conditioning system using phase shifted H-bridge modules," J. Power Electron., Vol. 13, No. 2, pp. 296-303, Mar. 2013. https://doi.org/10.6113/JPE.2013.13.2.296
  14. M. Borrega, L. Marroyo, R. Gonzalez, J. Balda, and J. L. Agorreta, "Modeling and control of a master-slave pv inverter with n-paralleled inverters and three-phase three limb inductors," IEEE Trans. Power Electron., Vol. 28, No. 6, pp. 2842-2855, Jun. 2013. https://doi.org/10.1109/TPEL.2012.2220859
  15. K. Xing, F. C. Lee, D. Borojevic, Z. Ye, and S. K. Mazumder, "Interleaved PWM with discontinuous spacevector modulation," IEEE Trans. Power Electron., Vol. 14, No. 5, pp. 906-917, Sep. 1999. https://doi.org/10.1109/63.788496
  16. T.-P. Chen, "Common-mode ripple current estimator for parallel three-phase inverters," IEEE Trans. Power Electron., Vol. 24, No. 5, pp. 1330-1339, May 2009. https://doi.org/10.1109/TPEL.2009.2012712
  17. S. G. Parker, B. P. McGrath, and D. G. Holmes, "Regions of active damping control for lcl filters," IEEE Trans. Ind. Appl., Vol. 50, No. 1, pp. 424-432, Jan./Feb. 2014. https://doi.org/10.1109/TIA.2013.2266892
  18. D. G. Holmes, T. A. Lipo, B. P. McGrath, and W. Y. Kong, "Optimized design of stationary frame three phase ac current regulators," IEEE Trans. Power Electron., Vol. 24, No. 11, pp. 2417-2426, Nov. 2009. https://doi.org/10.1109/TPEL.2009.2029548
  19. M. Zhang, L. Huang,W. Yao, and Z. Lu, "Circulating harmonic current elimination of a cps-pwm-based modular multilevel converter with a plug-in repetitive controller," IEEE Trans. Power Electron., Vol. 29, No. 4, pp. 2083- 2097, Apr. 2014. https://doi.org/10.1109/TPEL.2013.2269140
  20. R. Costa-Castello, R. Grino, and E. Fossas, "Odd-harmonic digital repetitive control of a single-phase current active filter," IEEE Trans. Power Electron., Vol. 19, No. 4, pp. 1060-1068, Jul. 2004. https://doi.org/10.1109/TPEL.2004.830045