A Single-Phase Unified Power Quality Conditioner with a Frequency-Adaptive Repetitive Controller

  • Phan, Dang-Minh ;
  • Lee, Hong-Hee
  • Received : 2017.07.25
  • Accepted : 2017.11.15
  • Published : 2018.03.01


This paper proposes a single-phase unified power quality conditioner (S-UPQC) for maintaining power quality issues in a microgrid. The S-UPQC can compensate the voltage and current harmonics, voltage sag, and swell as a dynamic voltage restorer (DVR), regardless of variations in the grid frequency. Odd harmonics are treated as even-order harmonics in a rotating frame to implement the harmonic compensators with only one repetitive controller (RC) without any harmonic extractor. The dynamic performance is improved and the delay time is reduced in the RC. The S-UPQC control scheme is designed to maintain accurate and stable operation under deviations of the grid frequency by using the Lagrange interpolation-based finite-impulse-response (LIFIR) filter approximation method. The proposed control schemes were validated through a simulation and experiment.


Power quality;Unified power quality conditioner (UPQC);Harmonic compensation;Repetitive controller (RC);Single-phase system


  1. H. Akagi, "New trends in active filters for power conditioning," in IEEE Transactions on Industry Applications, vol. 32, no. 6, pp. 1312-1322, Nov/Dec 1996.
  2. H. Fujita and H. Akagi, "The unified power quality conditioner: the integration of series and shunt-active filters," in IEEE Transactions on Power Electronics, vol. 13, no. 2, pp. 315-322, Mar 1998.
  3. Hirofumi Akagi; Edson Hirokazu Watanabe; Mauricio Aredes, "The Instantaneous Power Theory," in Instantaneous Power Theory and Applications to Power Conditioning, 1, Wiley-IEEE Press, 2007, pp. 41-107
  4. B. Han, B. Bae, H. Kim and S. Baek, "Combined operation of unified power-quality conditioner with distributed generation," in IEEE Transactions on Power Delivery, vol. 21, no. 1, pp. 330-338, Jan. 2006.
  5. M. Basu, S. P. Das and G. K. Dubey, "Investigation on the performance of UPQC-Q for voltage sag mitigation and power quality improvement at a critical load point," in IET Generation, Transmission & Distribution, vol. 2, no. 3, pp. 414-423, May 2008.
  6. R. A. Modesto, S. A. Oliveira da Silva and A. A. de Oliveira Junior, "Power quality improvement using a dual unified power quality conditioner/uninterruptible power supply in three-phase four-wire systems," in IET Power Electronics, vol. 8, no. 9, pp. 1595-1605, 2015.
  7. V. Khadkikar, "Enhancing Electric Power Quality Using UPQC: A Comprehensive Overview," in IEEE Transactions on Power Electronics, vol. 27, no. 5, pp. 2284-2297, May 2012.
  8. V. Khadkikar, A. Chandra, A. O. Barry and T. D. Nguyen, "Power quality enhancement utilising singlephase unified power quality conditioner: digital signal processor-based experimental validation," in IET Power Electronics, vol. 4, no. 3, pp. 323-331, March 2011.
  9. B. N. Singh, B. Singh, A. Chandra, P. Rastgoufard and K. Al-Haddad, "An Improved Control Algorithm for Active Filters," in IEEE Transactions on Power Delivery, vol. 22, no. 2, pp. 1009-1020, April 2007.
  10. V. Khadkikar and A. Chandra, "A Novel Structure for Three-Phase Four-Wire Distribution System Utilizing Unified Power Quality Conditioner (UPQC)," in IEEE Transactions on Industry Applications, vol. 45, no. 5, pp. 1897-1902, Sept.-oct. 2009.
  11. M. Liserre, R. Teodorescu and F. Blaabjerg, "Multiple harmonics control for three-phase grid converter systems with the use of PI-RES current controller in a rotating frame," in IEEE Transactions on Power Electronics, vol. 21, no. 3, pp. 836-841, May 2006.
  12. Q. N. Trinh and H. H. Lee, "An Enhanced Grid Current Compensator for Grid-Connected Distributed Generation Under Nonlinear Loads and Grid Voltage Distortions," in IEEE Transactions on Industrial Electronics, vol. 61, no. 12, pp. 6528-6537, Dec. 2014.
  13. A. Garcia-Cerrada, O. Pinzon-Ardila, V. Feliu-Batlle, P. Roncero-Sanchez and P. Garcia-Gonzalez, "Application of a Repetitive Controller for a Three-Phase Active Power Filter," in IEEE Transactions on Power Electronics, vol. 22, no. 1, pp. 237-246, Jan. 2007.
  14. Kai Zhang, Yong Kang, Jian Xiong and Jian Chen, "Direct repetitive control of SPWM inverter for UPS purpose," in IEEE Transactions on Power Electronics, vol. 18, no. 3, pp. 784-792, May 2003.
  15. J. M. Olm, G. A. Ramos and R. Costa-Castello, "Stability analysis of digital repetitive control systems under time-varying sampling period," in IET Control Theory & Applications, vol. 5, no. 1, pp. 29-37, January 6 2011.
  16. T. I. Laakso, V. Valimaki, M. Karjalainen and U. K. Laine, "Splitting the unit delay [FIR/all pass filters 13, no. 1, pp. 30-60, Jan 1996.
  17. D. Chen, J. Zhang and Z. Qian, "An Improved Repetitive Control Scheme for Grid-Connected Inverter With Frequency-Adaptive Capability," in IEEE Transactions on Industrial Electronics, vol. 60, no. 2, pp. 814-823, Feb. 2013.
  18. Q. N. Trinh and H. H. Lee, "Versatile UPQC Control System with a Modified Repetitive Controller under Nonlinear and Unbalanced Loads," Journal of Power Electronics, vol. 4, no. 4, Jul 2015.
  19. R. Nazir, K. Zhou, N. R. Watson and A. Wood, "Frequency adaptive repetitive control of gridconnected inverters," 2014 International Conference on Control, Decision and Information Technologies (CoDIT), Metz, 2014, pp. 584-588.
  20. Z. X. Zou, K. Zhou, Z. Wang and M. Cheng, "Frequency-Adaptive Fractional-Order Repetitive Control of Shunt Active Power Filters," in IEEE Transactions on Industrial Electronics, vol. 62, no. 3, pp. 1659-1668, March 2015.
  21. S. Chen, Y. M. Lai, S. C. Tan and C. K. Tse, "Analysis and design of repetitive controller for harmonic elimination in PWM voltage source inverter systems," in IET Power Electronics, vol. 1, no. 4, pp. 497-506, December 2008.
  22. B. Zhang, D. Wang, K. Zhou and Y. Wang, "Linear Phase Lead Compensation Repetitive Control of a CVCF PWM Inverter," in IEEE Transactions on Industrial Electronics, vol. 55, no. 4, pp. 1595-1602, April 2008.
  23. IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power Systems," in IEEE Std 519-1992, vol., no., pp. 1-112, April 9 1993.


Supported by : Korea Institute of Energy Technology Evaluation and Planning(KETEP), National Research Foundation of Korea