Document Type : Research Article

Authors

1 Department of Electrical Engineering, Boroujen Branch, Islamic Azad University, Boroujen, Iran.

2 Smart Microgrid Research Center, Najafabad Branch, Islamic Azad University, Najafabad, Iran.

3 Department of Electrical Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran.

Abstract

Conventional droop control method has been widely adopted for power sharing between Distributed Generators (DGs) in microgrids. However, the mismatched feeder impedance of the Voltage-Sourced Inverters (VSI) may generate reactive power sharing error during islanding operation of a microgrid. In this paper, an improved droop control method is suggested to improve the reactive power sharing accuracy. In the proposed method, the slope correction of the droop characteristics is performed in such a way that the reactive power sharing error is reduced. In this method, the errors of reactive power sharing are detected by applying a clear signal to the microgrids and, then, by adding a new term to the P-ω and correcting the slope of Q-E, the reactive power sharing is done. In this way, the proposed method can successfully improve the reactive power sharing accuracy even at different X/R ratios. Another feature of this method is its high operation speed compared to the other methods of droop feature correction. The simulation results for a prototype microgrid point to the efficiency and flexibility of the proposed method.
 

Keywords

Main Subjects

  1. Rahmani, M., Faghihi, F., Moradi-Cheshmeh-Beigi, H. and Hosseini, S., "Frequency control of islanded microgrids based on fuzzy cooperative and influence of STATCOM on frequency of microgrids", Journal of Renewable Energy and Environment (JREE), Vol. 5, (2018), 27-33. (http://dx.doi.org/10.30501/jree.2018.94119).
  2. Mahdavian, M. and Behzadfar, N., "A review of wind energy conversion system and application of various induction generators", Journal of Novel Researches on Electrical Power, Vol. 8, (2020), 55-66. (http://jeps.iaud.ac.ir/article-1-255-fa.html).
  3. Ahmadpour, A., Seyed Shenava, S., Dejamkhooy, A. and Mokaramian, E., "Electromagnetic force analysis of transformer on the ferroresonance due to consecutive 3–phase short–circuit faults using finite element method (FEM)", Journal of Intelligent Procedures in Electrical Technology, Vol. 11, (2020), 47-60. (https://dorl.net/dor/20.1001.1.23223871.1399.11.41.4.3).
  4. Jafari, A. and Shahgholian, Gh., "Analysis and simulation of a sliding mode controller for mechanical part of a doubly-fed induction generator based wind turbine", IET Generation, Transmission and Distribution, Vol. 11, (2017), 2677-2688. (http://dx.doi.org/10.1049/iet-gtd.2016.1969).
  5. Samadinasab, S., Namdari, F. and Bakhshipoor, M., "A novel approach for earthing system design using finite element method", Journal of Intelligent Procedures in Electrical Technology, Vol. 8, (2017), 54-63. (https://dorl.net/dor/20.1001.1.23223871.1396.8.29.6.0).
  6. Shahgholian, Gh., "An overview of hydroelectric power plant: Operation, modeling, and control", Journal of Renewable Energy and Environment (JREE), Vol. 7, (2020), 14-28. (http://dx.doi.org/10.30501/JREE.2020.221567.1087).
  7. Amooshahi, H., Hooshmand, R.A., Khodabakhshian, A. and Moazzami, M., "A new load-shedding approach for microgrids in the presence of wind turbines", Electric Power Components and Systems, Vol. 1, (2016), 726-736. (http://dx.doi.org/10.1080/15325008.2015.1131761).
  8. Hosseini, E. and Shahgholian, Gh., "Partial- or full-power production inWECS: A survey of control and structural strategies", European Power Electronics and Drives, Vol. 27, (2017), 125-142. (http://dx.doi.org/10.1080/09398368.2017.1413161).
  9. Hosseini, E. and Shahgholian, Gh., "Output power levelling for DFIG wind turbine system using intelligent pitch angle control", Automatika, Vol. 58, (2017), 363-374. (http://dx.doi.org/10.1080/00051144.2018.1455017).
  10. Mohammadjafari, M., Ebrahimi, R. and Parvin Darabad, V., "Optimal economic operation and battery sizing for microgrid energy management systems considering demand response", International Journal of Smart Electrical Engineering, Vol. 8, (2019), 129-136. (https://dorl.net/dor/20.1001.1.22519246.2019.08.04.1.2).
  11. Tayebi, A., Sharifi, R., Salemi, A. and Faghihi, F., "Investigating the effect of different penetration of renewable energy resources on islanded microgrid frequency control using a robust method", Signal Processing and Renewable Energy, Vol. 5, (2021), 15-34. (http://spre.azad.ac.ir/article_678747.html).
  12. Dong, R., Liu, S., Liang, G., An, X. and Xu, Y., "Output control method of microgrid VSI control network based on dynamic matrix control algorithm", IEEE Access, Vol. 7, (2019), 158459-158480. (http://dx.doi.org/10.1109/ACCESS.2019.2949909).
  13. Golpîra, H. and Bevrani, H., "Microgrids impact on power system frequency response", Energy Procedia, Vol. 156, (2019), 417-424. (http://dx.doi.org/10.1016/j.egypro.2018.11.097).
  14. Qi, Y., Lin, P., Wang, Y. and Tang, Y., "Two-dimensional impedance-shaping control with enhanced harmonic power sharing for inverter-based microgrids", IEEE Transactions on Power Electronics, Vol. 34, (2019), 11407-11418. (http://dx.doi.org/10.1109/TPEL.2019.2898670).
  15. Abbaspour, E., Fani, B. and Heydarian-Forushani, E., "A bi-level multi agent based protection scheme for distribution networks with distributed generation", International Journal of Electrical Power and Energy Systems, Vol. 112, (2019), 209-220. (http://dx.doi.org/10.1016/j.ijepes.2019.05.001).
  16. Kumar, J., Agarwal, A. and Agarwal, V., "A review on overall control of DC microgrids", Journal of Energy Storage, Vol. 21, (2019), 113-138. (http://dx.doi.org/10.1016/j.est.2018.11.013).
  17. Bagheri, S. and Moradi Cheshmeh Beigi, H., "DC microgrid voltage stability through inertia enhancement using a bidirectional dc-dc converter", Proceedings of the IEEE/IWEC, Shahrood, Iran, Vol. 1, (2021), 1-5. (http://dx.doi.org/10.1109/IWEC52400.2021.9467032).
  18. Rahbarimagham, H., "Optimal control of micro-grid (MG) to improve voltage profile including combined heat and power system", Journal of Intelligent Procedures in Electrical Technology, Vol. 9, (2019), 43-50. (https://dorl.net/dor/20.1001.1.23223871.1397.9.36.5.0).
  19. Olivares, D.E., Mehrizi-Sani, A., Etemadi, A.H., Cañizares, C.A., Iravani, R., Kazerani, M., Hajimiragha, A.H., Gomis-Bellmunt, O., Saeedifard, M., Palma-Behnke, R., Jiménez-Estévez, G.A. and Hatziargyriou, N.D., "Trends in microgrid control", IEEE Transactions on Smart Grid, Vol. 5, (2014), 1905-1919. (http://dx.doi.org/10.1109/TSG.2013.2295514).
  20. Zandi, F., Fani, B. and Golsorkhi, A., "A visually-driven nonlinear droop control for inverter dominated islanded microgrids", Electrical Engineering, Vol. 102, (2020), 1207-1222. (http://dx.doi.org/10.1007/s00202-020-00942-7).
  21. Zamanian, S., Sadi, S., Ghaffarpour, R. and Mahdavian, A., "Inverter-based microgrid dynamic stability analysis considering inventory of dynamic and static load models", Journal of Intelligent Procedures in Electrical Technology, Vol. 11, (2021), 91-109. (https://dorl.net/dor/20.1001.1.23223871.1399.11.44.6.1).
  22. Eberlein, S. and Rudion, K., "Small-signal stability modelling, sensitivity analysis and optimization of droop controlled inverters in LV microgrids", International Journal of Electrical Power and Energy Systems, Vol. 125, (2021), 106404. (http://dx.doi.org/10.1016/j.ijepes.2020.106404).
  23. Hsu, C.T., Cheng, T.J., Huang, H.M., Lee, Y.D., Chang, Y.R. and Jiang, J.L., "Over frequency control of photovoltaic inverters in an island microgrid", Microelectronics Reliability, Vol. 92, (2019), 42-54. (http://dx.doi.org/10.1016/j.microrel.2018.11.011).
  24. Karimi, H., Shahgholian, Gh., Fani, B., Sadeghkhani, I. and Moazzami, M., "A protection strategy for inverter interfaced islanded microgrids with looped configuration", Electrical Engineering, Vol. 101, (2019), 1059-1073. (http://dx.doi.org/10.1007/s00202-019-00841-6).
  25. Lo, K.Y. and Chen, Y.M., "Design of a seamless grid-connected inverter for microgrid applications", IEEE Transactions on Smart Grid, Vol. 11, (2020), 194-202. (http://dx.doi.org/10.1109/TSG.2019.2919905).
  26. Rezkallah, M., Singh, S., Singh, B., Chandra, A., Ibrahim, H. and Ghandour, M., "Implementation of two-level coordinated control for seamless transfer in standalone microgrid", IEEE Transactions on Industry Applications, Vol. 57, (2021), 1057-1068. (http://dx.doi.org/10.1109/TIA.2020.3037269).
  27. Saim, A., Mellah, R., Houari, A., Machmoum, M. and Djerioui, A., "Adaptive resonant based multi-loop control strategy for parallel distributed generation units in standalone microgrid application", Electric Power Systems Research, Vol. 143, (2017), 262-271. (http://dx.doi.org/10.1016/j.epsr.2016.10.010).
  28. Agrawal, R., Changan, D.D. and Bodhe, A., "Small signal stability analysis of stand-alone microgrid with composite load", Journal of Electrical Systems and Information Technology, Vol. 7, (2020), 12. (http://dx.doi.org/10.1186/s43067-020-00020-9).
  29. Kaur, A., Kaushal, J. and Basak, P., "A review on microgrid central controller", Renewable and Sustainable Energy Reviews, Vol. 55, (2016), 338-345. (http://dx.doi.org/10.1016/j.rser.2015.10.141).
  30. Gorji, S., Zamanian, S. and Moazzami, M., "Techno-economic and environmental base approach for optimal energy management of microgrids using crow search algorithm", Journal of Intelligent Procedures in Electrical Technology, Vol. 11, (2020), 49-68. (https://dorl.net/dor/20.1001.1.23223871.1399.11.43.4.7).
  31. Xu, Z., Yang, P., Zheng, C., Zhang, Y., Peng, J. and Zeng, Z., "Analysis on the organization and development of multi-microgrids", Renewable and Sustainable Energy Reviews, Vol. 81, (2018), 2204-2216. (http://dx.doi.org/10.1016/j.rser.2017.06.032).
  32. Li, Y., Meng, K., Dong, Z.Y. and Zhang, W., "Sliding framework for inverter-based microgrid control", IEEE Transactions on Power Systems, Vol. 35, (2020), 1657-1660. (http://dx.doi.org/10.1109/TPWRS.2020.2965762).
  33. Silva, G.F., Donaire, A., Seron, M.M., McFadyen, A. and Ford, J., "String stability in microgrids using frequency controlled inverter chains", IEEE Control Systems Letters, Vol. 6, (2022), 1484-1489. (http://dx.doi.org/10.1109/LCSYS.2021.3114143).
  34. Shahedi, R., Sabahi, K., Tayana, M. and Hajizadeh, A., "Self-tuning fuzzy PID controller for load frequency control in ac micro-grid with considering of input delay", Journal of Intelligent Procedures in Electrical Technology, Vol. 9, (2019), 19-26. (https://dorl.net/dor/20.1001.1.23223871.1397.9.35.3.6).
  35. Fayazi, H., Moazzami, M., Fani, B. and Shahgholian, Gh., "A first swing stability improvement approach in microgrids with synchronous distributed generators", International Transactions on Electrical Energy Systems, Vol. 31, (2021), e12816. (http://dx.doi.org/10.1002/2050-7038.12816).
  36. Bidram, A. and Davoudi, A., "Hierarchical structure of microgrids control system", IEEE Transactions on Smart Grid, Vol. 3, (2012), 1963-1976. (http://dx.doi.org/ 10.1109/TSG.2012.2197425).
  37. Saleh, M., Esa, Y. and Mohamed, A.A., "Communication-based control for dc microgrids", IEEE Transactions on Smart Grid, Vol. 10, (2019), 2180-2195. (http://dx.doi.org/10.1109/TSG.2018.2791361).
  38. Li, L., Sun, Y., Liu, Z., Hou, X., Shi, G. and Su, M., "A decentralized control with unique equilibrium point for cascaded-type microgrid", IEEE Transactions on Sustainable Energy, Vol. 10, (2019), 324-326. (http://dx.doi.org/10.1109/TSTE.2018.2871641).
  39. Hoang, T.V. and Lee, H.H., "Distributed control scheme for accurate reactive power sharing with enhanced voltage quality for islanded microgrids", Journal of Power Electronics, Vol. 20, (2020), 601-613. (http://dx.doi.org/10.1007/s43236-020-00047-1).
  40. Qi, Y., Fang, J. and Tang, Y., "Utilizing the dead-time effect to achieve decentralized reactive power sharing in islanded ac microgrids", IEEE Journal of Emerging and Selected Topics in Power Electronics, Vol. 8, (2020), 2350-2361. (http://dx.doi.org/10.1109/JESTPE.2019.2904077).
  41. Schiffer, J., Seel, T., Raisch, J. and Sezi, T., "Voltage stability and reactive power sharing in inverter-based microgrids with consensus-based distributed voltage control", IEEE Transactions on Control Systems Technology, Vol. 24, (2016), 96-109. (http://dx.doi.org/10.1109/TCST.2015.2420622).
  42. Chen, F., Chen, M., Li, Q., Meng, K., Guerrero, J.M. and Abbott, D., "Multiagent-based reactive power sharing and control model for islanded microgrids", IEEE Transactions on Sustainable Energy, Vol. 7, (2016), 1232-1244. (http://dx.doi.org/10.1109/TSTE.2016.2539213).
  43. Paspatis, A.G., Konstantopoulos, G.C. and Dedeoglu, S., "Control design and small-Signal stability analysis of inverter-based microgrids with inherent current limitation under extreme load conditions", Electric Power Systems Research, Vol. 193, (2021), 106929. (http://dx.doi.org/10.1016/j.epsr.2020.106929).
  44. Moon, H., Kim, Y. and Moon, S., "Frequency-based decentralized conservation voltage reduction incorporated into voltage-current droop control for an inverter-based islanded microgrid", IEEE Access, Vol. 7, (2019), 140542-140552. (http://dx.doi.org/10.1109/ACCESS.2019.2943538).
  45. Fani, B., Zandi, F. and Karami-Horestani, A., "An enhanced decentralized reactive power sharing strategy for inverter-basedmicrogrid", International Journal of Electrical Power and Energy Systems, Vol. 98, (2018), 531-542. (http://dx.doi.org/10.1016/j.ijepes.2017.12.023).
  46. Raju, E.S.N. and Jain, T., "A two-level hierarchical controller to enhance stability and dynamic performance of islanded inverter-based microgrids with static and dynamic loads", IEEE Transactions on Industrial Informatics, Vol. 15, (2019), 2786-2797. (http://dx.doi.org/10.1109/TII.2018.2869983).
  47. Khaledian, A. and Golkar, M.A., "Analysis of droop control method in an autonomous microgrid", Journal of Applied Research and Technology, Vol. 15, (2017), 371-377 (http://dx.doi.org/10.1016/j.jart.2017.03.004).
  48. Khaledian, A. and Golkar, M.A., "A new power sharing control method for an autonomous microgrid with regard to the system stability", Automatika, Vol. 59, (2018), 87-93. (http://dx.doi.org/10.1080/00051144.2018.1501462).
  49. Lai, J., Lu, X., Li, X. and Tang, R., "Distributed multiagent-oriented average control for voltage restoration and reactive power sharing of autonomous microgrids", IEEE Access, Vol. 6, (2018), 25551-25561. (http://dx.doi.org/10.1109/ACCESS.2018.2829881).
  50. Han, H., Liu, Y., Sun, Y., Su, M. and Guerrero, J.M., "An improved droop control strategy for reactive power sharing in islanded microgrid", IEEE Transactions on Power Electronics, Vol. 30, (2015), 3133-3141. (https://doi.org/10.1109/TPEL.2014.2332181).
  51. Yu, H., Qian, A. and Wang, S., "Analysis and optimization of droop controller for microgrid system based on small-signal dynamic mode", IEEE Transactions on Smart Grid, Vol. 7, (2016), 695-705. (http://dx.doi.org/10.1109/TSG.2015.2501316).
  52. Agundis-Tinajero, G., Segundo-Ramírez, J., Visairo-Cruz, N., Savaghebi, M., Guerrero, J.M. and Barocio, E., "Power flow modeling of islanded AC microgrids with hierarchical control", International Journal of Electrical Power and Energy Systems, Vol. 105, (2019), 28-36. (https://doi.org/10.1016/j.ijepes.2018.08.002).
  53. Guerrero, J.M., Vicuna, L.G., Matas, J., Castilla, M. and Miret, J., "Output impedance design of parallel-connected ups inverters with wireless load sharing control", IEEE Transactions on Industrial Electron., Vol. 52, (2005), 1126-1135. (https://doi.org/10.1109/TIE.2005.851634).
  54. Dou, C., Zhang, Z., Yue, D. and Song, M., "Improved droop control based on virtual impedance and virtual power source in low-voltage microgrid", IET Generation, Transmission and Distribution, Vol. 11, (2017), 1046-1054. (http://dx.doi.org/10.1049/iet-gtd.2016.1492).
  55. Zhu, Y., Zhuo, F., Wang, F., Liu, B., Gou, R. and Zhao, Y., "A virtual impedance optimization method for reactive power sharing in networked microgrid", IEEE Transactions on Power Electronics, Vol. 31, (2016), 2890-2904. (http://dx.doi.org/10.1109/TPEL.2015.2450360).
  56. Yao, W., Chen, M., Matas, J., Guerrero, J.M. and Qian, Z.M., "Design and analysis of the droop control method for parallel inverters considering the impact of the complex impedance on the power sharing", IEEE Transactions on Industrial Electronic, Vol. 58, (2011), 576-588. (http://doi.org/10.1109/TIE.2010.2046001).
  57. Zhong, Q., "Robust droop controller for accurate proportional load sharing among inverters operated in parallel", IEEE Transactions on Industrial Electronics, Vol. 60, (2013), 1281-1290. (http://dx.doi.org/10.1109/TIE.2011.2146221).
  58. Zandi, F., Fani, B., Sadeghkhani, I. and Orakzadeh, A., "Adaptive complex virtual impedance control scheme for accurate reactive power sharing of inverter interfaced autonomous microgrids", IET Generation, Transmission and Distribution, Vol. 12, (2018), 6021-6032. (http://dx.doi.org/10.1049/iet-gtd.2018.5123).
  59. Liu, B., Liu, Z., Liu, J., An, R., Zheng, H. and Shi, Y., "An adaptive virtual impedance control scheme based on small-ac-signal injection for unbalanced and harmonic power sharing in islanded microgrids", IEEE Transactions on Power Electronics, Vol. 34, (2019), 12333-12355 (http://dx.doi.org/10.1109/TPEL.2019.2905588).
  60. Rokrok, E. and Golshan, M., "Adaptive voltage droop scheme for voltage source converters in an islanded multibusmicrogrid", IET Generation, Transmission and Distribution, Vol. 4, (2010), 562-578. (http://dx.doi.org/10.1049/iet-gtd.2009.0146).
  61. Cao, W., Su, H., Cao, J., Sun, J. and Yang, D., "Improved droop control method in microgrid and its small signal stability analysis", Proceedings of the IEEE/ICRERA, Milwaukee, WI, Vol. 1, (2014), 197-202. (http://dx.doi.org/10.1109/ICRERA.2014.7016556).
  62. Gayatri, M.T.L., Parimi, A.M. and Kumar, A.V.P., "A review of reactive power compensation techniques in microgrids", Renewable and Sustainable Energy Reviews, Vol. 81, (2018), 1030-1036. (http://dx.doi.org/10.1016/j.rser.2017.08.006).
  63. Tayab, U.B., Roslan, M.A.B. and Hwai, L.J., Kashif, M., "A review of droop control techniques for microgrid", Renewable and Sustainable Energy Reviews, Vol. 76, (2017), 717-727. (http://dx.doi.org/10.1016/j.rser.2017.03.028).
  64. Deng, W., Dai, N., Lao, K.W. and Guerrero, J.M., "A virtual-impedance droop control for accurate active power control and reactive power sharing using capacitive-coupling inverters", IEEE Transactions on Industry Applications, Vol. 56, (2020), 6722-6733. (http://dx.doi.org/10.1109/TIA.2020.3012934).
  65. Kerdphol, T., Rahman,  F.S., Watanabe,  M. and Mitani, Y., "Robust virtual inertia control of a low inertia microgrid considering frequency measurement effects", IEEE Access, Vol. 7, (2019), 57550-57560. (https://doi.org/10.1109/ACCESS.2019.2913042).
  66. Shahgholian, Gh., "A brief review on microgrids: Operation, applications, modeling, and control", International Transactions on Electrical Energy Systems, Vol. 31, (2021), e12885. (https://doi.org/10.1002/2050-7038.12885).
  67. Arefifar, S., ABde-Rady, Y. and Mohamed, I., "Probabilistic optimal reactive power planning in distribution systems with renewable resources in grid-connected and islanded modes", IEEE Transactions on Industrial Electronics, Vol. 61, (2014), 5830-5839. (https://doi.org/10.1109/TIE.2014.2308144).
  68. Mohamed, Y. and El-Saadany, E.F., "Adaptive decentralized droop controller to preserve power sharing stability of paralleled inverters in distributed generation microgrids", IEEE Transactions on Power Electronics, Vol. 23, (2008), 2806-2816. (http://dx.doi.org/10.1109/TPEL.2008.2005100).
  69. Li, Y. and Nan-Kao, C., "An accurate power control strategy for power-electronics-interfaced distributed generation units operating in a low-voltage multi bus microgrid", IEEE Transactions on Power Electronics, Vol. 24, (2009), 2977-2988. (https://doi.org/10.1109/TPEL.2009.2022828).
  70. Tummuru, N.R., Mishra, M.K. and Srinivas, S., "An improved current controller for grid connected voltage source converter in microgrid applications", IEEE Transactions on Sustainable Energy, Vol. 6, (2015), 595-605. (http://doi.org/10.1109/TSTE.2015.2399496).
  71. Mahood, H., Michaleson, D. and Jiang, J., "Accurate reactive power sharing in an islanded microgrid using adaptive virtual impedances", IEEE Transactions on Power Electronics, Vol. 30, (2015), 1606-1617. (http://dx.doi.org/10.1109/TPEL.2014.2314721).