An Improved Hierarchical Control Structure for Robust Microgrid Operation and Seamless Mode Transfer under Linear and Nonlinear Loads conditions

Document Type : Original Article


Department of Electrical Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran


This paper proposes the improved hierarchical- based control of Microgrid based on proportional and multi-resonance controllers to compensate for harmonic distortion of nonlinear loads. Moreover, the probable transition of MG, especially from grid-connected to unplanned islanding and unintentional MG resources outage are studied. In current and voltage controllers of three-phase VSIs which are located in the inner level, the proportional and multi-resonant controllers are implemented. To attain proper decoupled (P-Q) power-sharing, a selective harmonic type virtual impedance, and a droop-based control are implemented at the primary level. Next, to reach better restoration and subsequently, seamless transition in accidental islanding, unintentional MG-DG’s outage, and synchronization process, the advanced three-phase SRF-PLL with in-loop MAF along with a simple adaptive lookup table are implemented in the secondary level of control. The MATLAB/Simulink simulation results verified that the proposed method improved the performance of control, effectiveness, and robustness in upstream or local grid variation.


  1. Palizban, O. and Kauhaniemi, K., “Hierarchical control structure in microgrids with distributed generation: Island and grid-connected mode,” Renewable and Sustainable Energy Reviews, 44, 797-813, (2015), DOI: 10.1016/j.rser.2015.01.008.
  2. Li, X., Zhang, H., Shadmand, M.B., and Balog, R. S., “Model predictive control of a voltage-source inverter with seamless transition between islanded and grid-connected operations,” IEEE Transactions on Industrial Electronics, 64, No. 10, 7906-7918, (2017), DOI: 10.1109/TIE.2017.2696459.
  3. Meng, L., Savaghebi, M., Andrade, F., Vasquez, J. C., Guerrero, J. M., and Graells, M., “Microgrid central controller development and hierarchical control implementation in the intelligent microgrid lab of Aalborg University,” 2015 IEEE Applied Power Electronics Conference and Exposition (APEC), 2585-2592, (2015), DOI: 10.1109/APEC.2015.7104716.
  4. Kaur, A., Kaushal, J., and Basak, P., “A review on microgrid central controller,” Renewable and Sustainable Energy Reviews, 55, 338-345, (2016), DOI: 10.1016/j.rser.2015.10.141.
  5. Guerrero, J. M., Chandorkar, M., Lee, T. and Loh, P. C., “Advanced Control Architectures for Intelligent Microgrids—Part I: Decentralized and Hierarchical Control,” IEEE Transactions on Industrial Electronics, 60, No. 4, 1254-1262, (2013), DOI: 10.1109/TIE.2012.2194969.
  6. Farokhian Firuzi, M., Roosta, A., and Gitizadeh, M., “Stability analysis and decentralized control of inverter-based ac microgrid,” Protection and Control of Modern Power Systems, 4, (2019), 10.1186/s41601-019-0120-x.
  7. Rocabert, J., Luna, A., Blaabjerg, F., and Rodriguez, P., “Control of power converters in AC microgrids,” IEEE Transactions on Power Electronics, 27, No. 11, 4734-4749, (2012), DOI: 10.1109/TPEL.2012.2199334.
  8. Norozpour Niazi, A., Vasegh, N., and Motie Birjandi, A. A., “To study unplanned islanding transient response of microgrid by implementing MSOGI and SRF-PLL based hierarchical control in the presence of nonlinear loads,” IET Renewable Power Generation, 14, No. 5, 881-890, (2020), 10.1049/iet-rpg.2019.0506.
  9. Guerrero, J. M., Vasquez, J. C., Matas, J., de Vicuna, L. G. and Castilla, M., “Hierarchical Control of Droop-Controlled AC and DC Microgrids: A General Approach Toward Standardization,” IEEE Transactions on Industrial Electronics, 58, No. 1, 158-172, (2011), DOI: 10.1109/TIE.2010.2066534.
  10. Sedhom, B. E., El‐Saadawi, M. M., Hatata, A. Y., and Abd‐Raboh, E. H. E., “H-infinity versus model predictive control methods for seamless transition between islanded‐ and grid‐connected modes of microgrids,” IET Renewable Power Generation, Vol. 14, No. 5, 856-870, (2020), DOI: 10.1049/iet-rpg.2019.0018
  11. Moradi,M. H., Eskandari, M., and Siano, P., “Safe transition from connection mode to islanding mode in microgrids,” 24th Iranian Conf. on Electrical Engineering (ICEE), 1902-1907, (2016), DOI: 10.1109/IranianCEE.2016.7585832.
  12. Li, Y., Yuan, L., Meng, K., and Dong, Z., “Smooth states transition control strategy for microgrid,” IEEE Int. Conf. on Information and Automation (ICIA), 86-91, (2017), DOI: 10.1109/ICInfA.2017.8078887.
  13. Lavanya, V., and Senthil Kumar, N., "Seamless Transition in Grid-connected Microgrid System using Proportional Resonant Controller." International Journal of Engineering, 33, No. 10, 1951-1958, (2020), DOI: 10.5829/IJE.2020.33.10A.13.
  14. Ahmadi, M., Sharafi, P., Mousavi, M. H., and Veysi, F., "Power Quality Improvement in Microgrids using STATCOM under Unbalanced Voltage Conditions." International Journal of Engineering, Transactions C: Aspects, 34, No. 6, 1455-1467, (2021), DOI: 10.5829/IJE.2021.34.06C.09.
  15. Imran, R. M., Wang, S., Flaih, F. M. S, and Salih, H. W., “Smooth mode transition control for micro-grid with hybrid battery/diesel combination,” 4th International Confernce on Information Science and Control Engineering (ICISCE), 1237-1242, (2017), DOI: 10.1109/ICISCE.2017.257.
  16. Golestan, S., Monfared, M., and Freijedo, F. D., “Design-oriented study of advanced synchronous reference frame phase-locked loops,” IEEE Transactions on Power Electronics, 28, No. 2, 765-778, (2013), DOI: 10.1109/TPEL.2012.2204276.
  17. Golestan, S., Guerrero, J. M., and Vasquez, J. C., “A PLL-based controller for three-phase grid-connected power converters,” IEEE Transactions on Power Electronics, 33, No. 2, 911-916, (2018), DOI: 10.1109/TPEL.2017.2719285.
  18. Golestan, S., Guerrero, J. M., Vidal, A., Yepes, A. G., and Doval-Gandoy, J., “PLL with MAF-based prefiltering stage: small-signal modeling and performance enhancement,” IEEE Transactions on Power Electronics, 31, No. 6, 4013-4019, (2016), DOI: 10.1109/TPEL.2015.2508882.
  19. Golestan, S., Guerrero, J. M., Vasquez, J. C., Abusorrah, A. M., and Al-Turki, Y., “A study on three-phase FLLs,” IEEE Transactions on Power Electronics, 34, No.1, 213-224, (2019), DOI: 10.1109/TPEL.2018.2826068.
  20. Vasquez, J. C., Guerrero, J. M., Savaghebi, M., Eloy-Garcia, J. and Teodorescu, R., “Modeling, Analysis, and Design of Stationary-Reference-Frame Droop-Controlled Parallel Three-Phase Voltage Source Inverters,” IEEE Transactions on Industrial Electronics, 60, No. 4, 1271-1280, (2013), DOI: 10.1109/TIE.2012.2194951.
  21. He, J., Li, Y. W., and Blaabjerg, F., “Flexible Microgrid Power Quality Enhancement Using Adaptive Hybrid Voltage and Current Controller,” IEEE Transactions on Industrial Electronics, 61, No. 6, 2784-2794, (2014), DOI: 10.1109/TIE.2013.2276774.
  22. Han, Y., Shen, P., Zhao, X., and Guerrero, J. M., “An enhanced power-sharing scheme for voltage unbalance and harmonics compensation in an islanded AC microgrid,” IEEE Transactions on Energy Conversion, 31, No. 3, 1037–1050, (2016), DOI: 10.1109/TEC.2016.2552497.
  23. Savaghebi, M., Jalilian, A., Vasquez, J. C., and Guerrero, J. M., “Secondary control for voltage quality enhancement in microgrids,” IEEE Transactions on Smart Grid, 3, No.4, 1893-1902, (2012), DOI: 10.1109/TSG.2012.2205281.
  24. Yazdani, A., Iravani, R., “Voltage-Sourced Converters in Power Systems: Modeling, Control, and Applications,” Wiley-IEEE Press,
  25. Rocabert, J., Luna, A., Blaabjerg, F., and Rodríguez, P., “Control of Power Converters in AC Microgrids,” IEEE Transactions on Power Electronics, 27, No. 11, 4734–4749, (2012), DOI: 10.1109/TPEL.2012.2199334.
  26. Zamora, R. and Srivastava, A. K., “Controls for microgrids with storage: review, challenges, and research needs,” Renewable and Sustainable Energy Reviews., 14, No. 7, 2009–2018, (2018), DOI: 10.1016/j.rser.2010.03.019.
  27. Golsorkhi, M. S. and Savaghebi, M., “A Decentralized Control Strategy Based on V-I Droop for Enhancing Dynamics of Autonomous Hybrid AC/DC Microgrids,” IEEE Transactions on Power Electronics, 36, No. 8, 9430-9440, (2021), DOI: 10.1109/TPEL.2021.3049813.
  28. Mousazadeh Mousavi, S. Y., Jalilian, A., Savaghebi, M., and Guerrero, J. M., “Coordinated control of multifunctional inverters for voltage support and harmonic compensation in a grid-connected microgrid,” Electric Power Systems Research, 155, 254-264, (2018), DOI: 10.1016/j.epsr.2017.10.016.
  29. Golestan, S., Guerrero, J. M., Vasquez, J. C., Abusorrah, A. M., and Al-Turki, Y., “Modeling, Tuning, and Performance Comparison of Second-Order-Generalized-Integrator-Based FLLs,” IEEE Transactions on Power Electronics, 33, No. 12, 10229-10239, (2018), DOI: 10.1109/TPEL.2018.2808246.
  30. Rodriguez, P., Luna, A., Candela, I., Mujal, R., Teodorescu, R., and Blaabjerg, F., “Multiresonant Frequency-Locked Loop for Grid Synchronization of Power Converters Under Distorted Grid Conditions,” IEEE Transactions on Industrial Electronics, 58, No. 1, 127-138, (2011), DOI: 10.1109/TIE.2010.2042420.
  31. Heydari, R., Khayat, Y., Naderi, M., Anvari-Moghaddam, A., Dragicevic, T. and Blaabjerg, F., “A Decentralized Adaptive Control Method for Frequency Regulation and Power Sharing in Autonomous Microgrids,” 2019 IEEE 28th International Symposium on Industrial Electronics (ISIE), 2427-2432, (2019), DOI: 10.1109/ISIE.2019.8781102.
  32. Li, M., Gui, Y., Guan, Y., Matas, J., Guerrero, J. M. and Vasquez, J. C., “Inverter Parallelization for an Islanded Microgrid Using the Hopf Oscillator Controller Approach with Self-synchronization Capabilities,” IEEE Transactions on Industrial Electronics, (2020), DOI: 10.1109/TIE.2020.3031520.