Browse > Article
http://dx.doi.org/10.6113/JPE.2016.16.3.1152

Improved Reactive Power Sharing for Parallel-operated Inverters in Islanded Microgrids  

Issa, Walid (Renewable Energy Research Group, University of Exeter)
Sharkh, Suleiman (Electro-Mechanical Engineering Research Group, University of Southampton)
Mallick, Tapas (Renewable Energy Research Group, University of Exeter)
Abusara, Mohammad (Renewable Energy Research Group, University of Exeter)
Publication Information
Journal of Power Electronics / v.16, no.3, 2016 , pp. 1152-1162 More about this Journal
Abstract
The unequal impedances of the interconnecting cables between paralleled inverters in the island mode of microgrids cause inaccurate reactive power sharing when the traditional droop control is used. Many studies in the literature adopt low speed communications between the inverters and the central control unit to overcome this problem. However, the losses of this communication link can be very detrimental to the performance of the controller. This paper proposes an improved reactive power-sharing control method. It employs infrequent measurements of the voltage at the point of common coupling (PCC) to estimate the output impedance between the inverters and the PCC and then readjust the voltage droop controller gains accordingly. The controller then reverts to being a traditional droop controller using the newly calculated gains. This increases the immunity of the controller against any losses in the communication links between the central control unit and the inverters. The capability of the proposed control method has been demonstrated by simulation and experimental results using a laboratory scale microgrid.
Keywords
Communication loss; Droop control; Islanded inverters; Microgrids; Reactive power sharing;
Citations & Related Records
연도 인용수 순위
  • Reference
1 Y. Pei, G. Jiang, X. Yang, and Z. Wang, "Auto-master-slave control technique of parallel inverters in distributed AC power systems and UPS," in IEEE 35th Annual Conference of Power Electronics Specialists, pp. 2050-2053, 2004.
2 W. C. Lee, T.-K. Lee, S.-H. Lee, K.-H. Kim, D.-S. Hyun, and I.-Y. Suh, "A master and slave control strategy for parallel operation of three-phase UPS systems with different ratings," in the Nineteenth Annual IEEE Applied Power Electronics Conference and Exposition, Vol. 1, pp. 456-462, 2004.
3 Y. J. Cheng and E. K. K. Sng, “A novel communication strategy for decentralized control of paralleled multi-inverter systems,” IEEE Trans. Power Electron., Vol. 21, No. 1, pp. 148-156, Jan 2006.   DOI
4 T. Iwade, S. Komiyama, Y. Tanimura, M. Yamanaka, M. Sakane, and K. Hirachi, "A novel small-scale UPS using a parallel redundant operation system," in The 25th International Telecommunications Energy Conference Japan, pp. 480-484, 2003.
5 J. Tan, H. Lin, J. Zhang, and J. Ying, "A novel load sharing control technique for paralleled inverters," in IEEE 34th Annual Power Electronics Specialist Conference, pp. 1432-1437, 2003.
6 T.-F. Wu, Y.-K. Chen, and Y.-H. Huang, “3C strategy for inverters in parallel operation achieving an equal current distribution,” IEEE Trans. Ind. Electron., Vol. 47, No. 2, pp. 273-281, Apr. 2000.   DOI
7 M. Abusara, J. M. Guerrero, and S. Sharkh, “Line interactive UPS for microgrids,” IEEE Trans. Ind. Electron.,Vol. 61, No. 3, pp. 1-8, Mar. 2013.
8 J. M. Guerrero, L. G. De Vicuna, J. Matas, M. Castilla, and J. Miret, “A wireless controller to enhance dynamic performance of parallel inverters in distributed generation systems,” IEEE Trans. Power Electron., Vol. 19, No. 5, pp. 1205-1213, Sep. 2004.   DOI
9 W. Yao, M. Chen, M. Gao, and Z. Qian, "A wireless load sharing controller to improve the performance of parallel-connected inverters," in Twenty-Third Annual IEEE in Applied Power Electronics Conference and Exposition, pp. 1628-1631, 2008.
10 E. A. A. Coelho, P. C. Cortizo, and P. F. D. Garcia, “Small-signal stability for parallel-connected inverters in stand-alone AC supply systems,” IEEE Trans. Ind. Appl., Vol. 38, No. 2, pp. 533-542, Apr. 2002.   DOI
11 J. C. Vasquez, J. M. Guerrero, A. Luna, P. Rodríguez, and R. Teodorescu, “Adaptive droop control applied to voltage-source inverters operating in grid-connected and islanded modes,” IEEE Trans. Ind. Electron., Vol. 56, No. 10, pp. 4088-4096, Oct. 2009.   DOI
12 H. J. Avelar, W. A. Parreira, J. B. Vieira, L. C. G. de Freitas, and E. A. A. Coelho, “a state equation model of a single-phase grid-connected inverter using a droop control scheme with extra phase shift control action,” IEEE Trans. Ind. Electron., Vol. 59, No. 3, pp. 1527-1537, Mar. 2012.   DOI
13 A. Tuladhar, H. Jin, T. Unger, and K. Mauch, “Control of parallel inverters in distributed AC power systems with consideration of line impedance effect,” IEEE Trans. Ind. Appl., Vol. 36, No. 1, pp. 131-138, Feb. 2000.   DOI
14 C.-T. Lee, C. C. Chu, and P.-T. Cheng, "A new droop control method for the autonomous operation of distributed energy resource interface converters," in Proc. of the 2010 IEEE Energy Conversion Congress and Exposition (ECCE), pp. 702-709, 2010.
15 A. Micallef, M. Apap, C. S. Staines, and J. M. Guerrero Zapata, "Secondary control for reactive power sharing and voltage amplitude restoration in droop-controlled islanded microgrids," in 3rd IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), pp. 492-498, 2012.
16 J. He, Y. W. Li, J. M. Guerrero, J. C. Vasquez, and F. Blaabjerg, "An islanding microgrid reactive power sharing scheme enhanced by programmed virtual impedances," in 3rd IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), pp. 229-235, 2012.
17 Y. W. Li and C. N. Kao, “An accurate power control strategy for power-electronics-interfaced distributed generation units operating in a low-voltage multibus microgrid,” IEEE Trans. Power Electron., Vol. 24, No. 12, pp. 2977-2988, Dec. 2009.   DOI
18 Q.-C. Zhong, “Robust droop controller for accurate proportional load sharing among inverters operated in parallel,” IEEE Trans. Ind. Electron., Vol. 60, No. 4, pp. 1281-1290, Apr. 2013.   DOI
19 J. He and Y. W. Li, “An enhanced microgrid load demand sharing strategy,” IEEE Trans. Power Electron., Vol. 27, No. 9, pp. 3984-3995, Sep. 2012.   DOI
20 J. He, Y. W. Li, J. M. Guerrero, F. Blaabjerg, and J. C. Vasquez, “An islanding microgrid power sharing approach using enhanced virtual impedance control scheme,” IEEE Trans. Power Electron., Vol. 28, No. 11, pp. 5272-5282, Nov. 2013.   DOI
21 W. Issa, M. Abusara, and S. Sharkh, “Control of transient power during unintentional islanding of microgrids,” IEEE Trans. Power Electron., Vol. 30, No. 8, pp. 4573-4584, Aug. 2014.   DOI
22 B. M. Eid, N. A. Rahim, J. Selvaraj, and A. H. El Khateb, “Control methods and objectives for electronically coupled distributed energy resources in microgrids: A review,” IEEE Systems Journal, Jan. 2014.
23 J. M. Guerrero, L. G. de Vicuna, J. Matas, M. Castilla, and J. Miret, “Output impedance design of parallel-connected UPS inverters with wireless load-sharing control,” IEEE Trans. Ind. Electron., Vol. 52, No. 4, pp. 1126-1135, Aug. 2005.   DOI