Hierarchical Fuzzy Control Applied to Parallel Connected UPS Inverters Using Average Current Sharing Scheme

  • Santosh Kumar Singh
  • Sumit Ghatak ChoudhuriEmail author
Original Contribution


Parallel connection of UPS inverters to enhance power rating is a widely accepted practice. Inter-modular circulating currents appear when multiple inverter modules are connected in parallel to supply variable critical load. Interfacing of modules henceforth requires an intensive design, using proper control strategy. The potentiality of human intuitive Fuzzy Logic (FL) control with imprecise system model is well known and thus can be utilised in parallel-connected UPS systems. Conventional FL controller is computational intensive, especially with higher number of input variables. This paper proposes application of Hierarchical-Fuzzy Logic control for parallel connected Multi-modular inverters system for reduced computational burden on the processor for a given switching frequency. Simulated results in MATLAB environment and experimental verification using Texas TMS320F2812 DSP are included to demonstrate feasibility of the proposed control scheme.


Average Current Sharing (ACS) Hierarchical-Fuzzy Logic (H-FL) Multi-inverter Multi-modular (M-M) Parallel inverter Uninterruptible Power Supply (UPS) 


  1. 1.
    S.B. Bekiarov, A. Emadi, Uninterruptible power supplies: classification, operation, dynamics, and control, in APEC. Seventeenth Annual IEEE Applied Power Electronics Conference and Exposition (Cat. No. 02CH37335), 2002, vol. 0, no. c, pp. 597–604Google Scholar
  2. 2.
    B. Wei, J.M. Guerrero, J.C. Vasquez, X. Guo, A circulating-current suppression method for parallel-connected voltage-source inverters with common DC and AC buses. IEEE Trans. Ind. Appl. 53(4), 3758–3769 (2017)CrossRefGoogle Scholar
  3. 3.
    T. Kawabata, S. Higashino, Parallel operation of voltage source inverters. IEEE Trans. Ind. Appl. 24(2), 281–287 (1988)CrossRefGoogle Scholar
  4. 4.
    J.M. Guerrero, L. Hang, J. Uceda, Control of distributed uninterruptible power supply systems. IEEE Trans. Ind. Electron. 55(8), 2845–2859 (2008)CrossRefGoogle Scholar
  5. 5.
    S.K. Khadem, M. Basu, M.F. Conlon, Parallel operation of inverters and active power filters in distributed generation system—a review. Renew. Sustain. Energy Rev. 15(9), 5155–5168 (2011)CrossRefGoogle Scholar
  6. 6.
    S. Shah, P.S. Sensarma, Three degree of freedom robust voltage controller for instantaneous current sharing among voltage source inverters in parallel. IEEE Trans. Power Electron. 25(12), 3003–3014 (2010)CrossRefGoogle Scholar
  7. 7.
    A.M. Roslan, K.H. Ahmed, S.J. Finney, B.W. Williams, Improved instantaneous average current-sharing control scheme for parallel-connected inverter considering line impedance impact in microgrid networks. IEEE Trans. Power Electron. 26(3), 702–716 (2011)CrossRefGoogle Scholar
  8. 8.
    X. Sun, Y. Lee, D. Xu, Modeling, analysis, and implementation of parallel multi-inverter systems with instantaneous average-current-sharing scheme. IEEE Trans. Power Electron. 18(3), 844–856 (2003)CrossRefGoogle Scholar
  9. 9.
    Y. Zhang, M. Yu, F. Liu, Y. Kang, Instantaneous current-sharing control strategy for parallel operation of UPS modules using virtual impedance. IEEE Trans. Power Electron. 28(1), 432–440 (2013)CrossRefGoogle Scholar
  10. 10.
    G. Zhu, X. Wei, J. Lu, X. Xu, Instantaneous current-sharing control scheme of multi-inverter modules in parallel based on virtual circulating impedance. IET Power Electron. 9(5), 960–968 (2016)CrossRefGoogle Scholar
  11. 11.
    H. Osterholtz, Simple fuzzy control of a PWM inverter for a UPS system, in 17th International Telecommunications Energy Conference Proceedings of INTELEC 95, 1995, pp. 565–570Google Scholar
  12. 12.
    Y.Y. Tzou, L.H. Ho, R.S. Ou, Fuzzy control of a closed-loop regulated PWM inverter under large load variations, in Proceedings of IECON ’9319th Annual Conference of IEEE Industrial Electronics, 1993, pp. 267–272Google Scholar
  13. 13.
    C. Song, R. Zhao, H. Yang, Z. Zeng, J. Wu, Using fuzzy control for parallel-inverter system with nonlinear-load, in International Conference on Electrical Machines and Systems, 2010, pp. 193–197Google Scholar
  14. 14.
    N.N. Ayop, M.A. Roslan, Y.N. Zaiazmin, Z.M. Isa, H. Ahmad, Fuzzy logic based centralized power sharing scheme, in 2016 IEEE International Conference on Power and Energy (PECon), 2016, pp. 697–601Google Scholar
  15. 15.
    C.C. Lee, Fuzzy logic in control systems: fuzzy logic controller. I. IEEE Trans. Syst. Man. Cybern. 20(2), 404–418 (1990)MathSciNetCrossRefzbMATHGoogle Scholar
  16. 16.
    G.V.S. Raju, J. Zhou, R.A. Kisner, Hierarchical fuzzy control. Int. J. Control 54(5), 1201–1216 (1991)MathSciNetCrossRefzbMATHGoogle Scholar
  17. 17.
    L.X. Wang, Analysis and design of hierarchical fuzzy systems. IEEE Trans. Fuzzy Syst. 7(5), 617–624 (1999)CrossRefGoogle Scholar
  18. 18.
    M.J. Ryan, W.E. Brumsickle, R.D. Lorenz, Control topology options for single-phase UPS inverters. IEEE Trans. Ind. Appl. 33(2), 493–501 (1997)CrossRefGoogle Scholar
  19. 19.
    N. Werro, Fuzzy Classification of Online Customers (Springer, Cham, 2015)CrossRefGoogle Scholar
  20. 20.
    D.P. Kothari, J.S. Dhillon, Power System Optimization, 2nd edn. Prentice Hall Of India, 2004, 2011Google Scholar
  21. 21.
    M. Lee, H. Chung, F. Yu, Modeling of hierarchical fuzzy systems. Fuzzy Sets Syst. 138(2), 343–361 (2003)MathSciNetCrossRefGoogle Scholar

Copyright information

© The Institution of Engineers (India) 2018

Authors and Affiliations

  1. 1.Department of Electrical EngineeringIndian Institute of Technology RoorkeeRoorkeeIndia

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