Robust tuning of transient droop gains based on Kharitonov's stability theorem in droop-controlled microgrids

Robust tuning of transient droop gains based on Kharitonov's stability theorem in droop-controlled microgrids

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This study addresses the robust stability analysis for an islanded microgrid with droop-controlled inverter-based distributed generators (DGs). Owing to large load changes, microgrid structure reconfiguration, and higher-power demands, the low-frequency (LF) dominant modes of a microgrid stir toward unstable zone and make the system more oscillatory or even unstable. In this study, a robust two-degree-of-freedom (2DOF) decentralised droop controller, which is the combination of the conventional droop with a robust transient droop function, is utilised for each inverter-based DG unit. Unlike conventional tuning of 2DOF droop controllers, a new design procedure is proposed to robustly determine the transient droop gains to effectively damp the LF oscillatory modes of the islanded microgrid irrespective of disturbances, equilibrium point variations, and uncertain parameters of a microgrid. To mitigate the LF power oscillations at different microgrid conditions, inspired by Kharitonov's stability theorem, a robust D-stability analysis is performed to determine the specific ranges of the transient droop gains to provide a robustness margin for the disturbances, equilibrium point variations, and uncertain parameters of the islanded microgrid. Finally, digital time-domain simulation studies are performed in MATLAB/SimPowerSystems software environment to verify the effectiveness of the proposed method.


    1. 1)
      • 1. Abdelaziz, M.M.A., Farag, H.E., El-Saadany, E.F.: ‘Optimum droop parameter settings of islanded microgrids with renewable energy resources’, IEEE Trans. Sustain. Energy, 2014, 5, (2), pp. 434445.
    2. 2)
      • 2. Mumtaz, F., Syed, M.H., Hosani, M.A., et al: ‘A novel approach to solve power flow for islanded microgrids using modified Newton–Raphson with droop control of DG’, IEEE Trans. Sustain. Energy, 2016, 7, (2), pp. 493503.
    3. 3)
      • 3. Pasha, A.M., Zeineldin, H.H., Al-Sumaiti, A.S., et al: ‘Conservation voltage reduction for autonomous microgrids based on V–I droop characteristics’, IEEE Trans. Sustain. Energy, 2017, 8, (3), pp. 10761085.
    4. 4)
      • 4. Augustine, S., Mishra, M.K., Lakshminarasamma, N.: ‘Adaptive droop control strategy for load sharing and circulating current minimization in low-voltage standalone DC microgrid’, IEEE Trans. Sustain. Energy, 2015, 6, (1), pp. 132141.
    5. 5)
      • 5. Syed, M.H., Zeineldin, H.H., Moursi, M.S.E.: ‘Hybrid micro-grid operation characterisation based on stability and adherence to grid codes’, IET Gener. Transm. Distrib., 2014, 8, (3), pp. 563572.
    6. 6)
      • 6. Guerrero, J.M., Vasquez, J.C., Matas, J., et al: ‘Hierarchical control of droop-controlled AC and DC microgrids – a general approach toward standardization’, IEEE Trans. Ind. Electron., 2011, 58, (1), pp. 158172.
    7. 7)
      • 7. Ashabani, S.M., Mohamed, Y.A.R.I.: ‘General interface for power management of micro-grids using nonlinear cooperative droop control’, IEEE Trans. Power Syst., 2013, 28, (3), pp. 29292941.
    8. 8)
      • 8. Guerrero, J.M., Chandorkar, M., Lee, T.L., et al: ‘Advanced control architectures for intelligent microgrids – part I: decentralized and hierarchical control’, IEEE Trans. Ind. Electron., 2013, 60, (4), pp. 12541262.
    9. 9)
      • 9. Zhong, Q.C.: ‘Robust droop controller for accurate proportional load sharing among inverters operated in parallel’, IEEE Trans. Ind. Electron., 2013, 60, (4), pp. 12811290.
    10. 10)
      • 10. Mohamed, Y.A.R.I., El-Saadany, E.F.: ‘Adaptive decentralized droop controller to preserve power sharing stability of paralleled inverters in distributed generation microgrids’, IEEE Trans. Power Electron., 2008, 23, (6), pp. 28062816.
    11. 11)
      • 11. Majumder, R., Chaudhuri, B., Ghosh, A., et al: ‘Improvement of stability and load sharing in an autonomous microgrid using supplementary droop control loop’, IEEE Trans. Power Syst., 2010, 25, (2), pp. 796808.
    12. 12)
      • 12. Bollen, M.H.J., Das, R., Djokic, S., et al: ‘Power quality concerns in implementing smart distribution-grid applications’, IEEE Trans. Smart Grid, 2017, 8, (1), pp. 391399.
    13. 13)
      • 13. Kallamadi, M., Sarkar, V.: ‘Enhanced real-time power balancing of an ac microgrid through transiently coupled droop control’, IET Gener. Transm. Distrib., 2017, 11, (8), pp. 19331942.
    14. 14)
      • 14. Kahrobaeian, A., Mohamed, Y.A.R.I.: ‘Analysis and mitigation of low-frequency instabilities in autonomous medium-voltage converter-based microgrids with dynamic loads’, IEEE Trans. Ind. Electron., 2014, 61, (4), pp. 16431658.
    15. 15)
      • 15. Bottrell, N., Prodanovic, M., Green, T.C.: ‘Dynamic stability of a microgrid with an active load’, IEEE Trans. Power Electron., 2013, 28, (11), pp. 51075119.
    16. 16)
      • 16. Borup, U., Blaabjerg, F., Enjeti, P.N.: ‘Sharing of nonlinear load in parallel-connected three-phase converters’, IEEE Trans. Ind. Appl., 2001, 37, (6), pp. 18171823.
    17. 17)
      • 17. Yao, W., Chen, M., Matas, J., et al: ‘Design and analysis of the droop control method for parallel inverters considering the impact of the complex impedance on the power sharing’, IEEE Trans. Ind. Electron., 2011, 58, (2), pp. 576588.
    18. 18)
      • 18. Guerrero, J.M., Matas, J., de Vicuna, L.G., et al: ‘Decentralized control for parallel operation of distributed generation inverters using resistive output impedance’, IEEE Trans. Ind. Electron., 2007, 54, (2), pp. 9941004.
    19. 19)
      • 19. Savaghebi, M., Jalilian, A., Vasquez, J.C., et al: ‘Autonomous voltage unbalance compensation in an islanded droop-controlled microgrid’, IEEE Trans. Ind. Electron., .2013, 60, (4), pp. 13901402.
    20. 20)
      • 20. Savaghebi, M., Jalilian, A., Vasquez, J.C., et al: ‘Secondary control scheme for voltage unbalance compensation in an islanded droop-controlled microgrid’, IEEE Trans. Smart Grid, 2012, 3, (2), pp. 797807.
    21. 21)
      • 21. De, D., Ramanarayanan, V.: ‘Decentralized parallel operation of inverters sharing unbalanced and nonlinear loads’, IEEE Trans. Power Electron., 2010, 25, (12), pp. 30153025.
    22. 22)
      • 22. Pogaku, N., Prodanovic, M., Green, T.C.: ‘Modeling, analysis and testing of autonomous operation of an inverter-based microgrid’, IEEE Trans. Power Electron., 2007, 22, (2), pp. 613625.
    23. 23)
      • 23. Guo, X., Lu, Z., Wang, B., et al: ‘Dynamic phasors-based modeling and stability analysis of droop-controlled inverters for microgrid applications’, IEEE Trans. Smart Grid, 2014, 5, (6), pp. 29802987.
    24. 24)
      • 24. Yu, K., Ai, Q., Wang, S., et al: ‘Analysis and optimization of droop controller for microgrid system based on small-signal dynamic model’, IEEE Trans. Smart Grid, 2016, 7, (2), pp. 695705.
    25. 25)
      • 25. Schiffer, J., Ortega, R., Astolfi, A., et al: ‘Conditions for stability of droop-controlled inverter-based microgrids’, Automatica, 2014, 50, (10), pp. 24572469.
    26. 26)
      • 26. Coelho, E.A.A., Cortizo, P.C., Garcia, P.F.D.: ‘Small signal stability for single phase inverter connected to stiff AC system’, Proc. IEEE IAS Annu. Meet., 1999, 4, (1), pp. 21802187.
    27. 27)
      • 27. John, T., Lam, S.P.: ‘Voltage and frequency control during microgrid islanding in a multi-area multi-microgrid system’, IET Gener. Transm. Distrib., 2017, 11, (6), pp. 15021512.
    28. 28)
      • 28. Alaboudy, A.H.K., Zeineldin, H.H., Kirtley, J.: ‘Simple control strategy for inverter-based distributed generator to enhance microgrid stability in the presence of induction motor loads’, IET Gener. Transm. Distrib., 2013, 7, (10), pp. 11551162.
    29. 29)
      • 29. Majumder, R., Ghosh, A., Ledwich, G., et al: ‘Power sharing and stability enhancement of an autonomous microgrid with inertial and non-inertial DGs with DSTATCOM’. Proc. Int. Conf. Power Systems, December 2009, pp. 16.
    30. 30)
      • 30. Majumder, R., Ghosh, A., Ledwich, G., et al: ‘Operation and control of hybrid microgrid with angle droop controller’. Proc. TENCON, November 2010, pp. 509515.
    31. 31)
      • 31. Vandoorn, T., Kooning, J.D., Meersman, B., et al: ‘Review of primary control strategies for islanded microgrids with power-electronic interfaces’, Renew. Sustain. Energy Rev., 2013, 19, pp. 613628.
    32. 32)
      • 32. Barmish, B.R.: ‘New tools for robustness of linear systems’ (Macmillan, New York, NY, USA, 1994).
    33. 33)
      • 33. Skogestad, S., Postlethwaite, I.: ‘Multivariable feedback control: analysis and design’ (Wiley, Hoboken, NJ, USA, 2001, 3rd edn.).
    34. 34)
      • 34. Habibi, B.H.F., Naghshbandy, A: ‘Robust voltage controller design for an isolated microgrid using Kharitonov's theorem and D-stability concept’, Int. J. Electr. Power Energy Syst., 2013, 44, (1), pp. 656665.
    35. 35)
      • 35. Yang, X., Yuan, Y., Long, Z., et al: ‘Robust stability analysis of active voltage control for high-power IGBT switching by Kharitonov's theorem’, IEEE Trans. Power Electron., 2016, 31, (3), pp. 25842595.
    36. 36)
      • 36. Hote, Y.V., Choudhury, D.R., Gupta, J.R.P.: ‘Robust stability analysis of the PWM push-pull DC–DC converter’, IEEE Trans. Power Electron., 2009, 24, (10), pp. 23532356.
    37. 37)
      • 37. Dehkordi, N.M., Sadati, N., Hamzeh, M.: ‘Distributed robust finite-time secondary voltage and frequency control of islanded microgrids’, IEEE Trans. Power Syst., 2017, 32, (5), pp. 36483659.

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