© The Institution of Engineering and Technology
In this study, a microgrid with two voltage source inverters (VSIs), operating in islanded or grid-connected mode is analysed. The active power control by droop coefficients and reference frequencies is demonstrated. In addition, the inductive and resistive droop strategies are compared by considering the complex line impedance. By measuring the line impedance in the prototype, it was found that, even for the low-voltage microgrid, the line impedance was not predominantly resistive, but complex. For this line impedance condition, an investigation to determine the best droop control law considering the partial derivatives. Observing the partial derivatives and the experimental results obtained it is demonstrated that inductive droop control is better to control the active power for complex line impedance. For a scenario with resistive unbalanced loads and different power sharing between the inverters, the proposed control, implemented in the a–b–c reference frame, was validated. A novel absolute damping factor is developed to improve the transient response and reduce the reactive power flow. The VSIs are connected to the grid without transformers to reduce the connection costs. Simulation and experimental results are presented to confirm the improvements achieved using the implemented control method.
References
-
-
1)
-
21. Li, Y.W., Vilathgamuwa, D., Loh, P.C.: ‘A grid-interfacing power quality compensator for three-phase three-wire microgrid applications’, IEEE Trans. Power Electron., 2006, 21, (4), pp. 1021–1031 (doi: 10.1109/TPEL.2006.876844).
-
2)
-
9. Katiraei, F., Iravani, M.R.: ‘Power management strategies for a microgrid with multiple distributed generation units’, IEEE Trans. Power Syst., 2006, 21, (4), pp. 1821–1831 (doi: 10.1109/TPWRS.2006.879260).
-
3)
-
19. Huber, L., Kumar, M., Jovanovic, M.: ‘Performance comparison of PI and P compensation in DSP based average-current-controlled three-phase six-switch boost PFC rectifier’, IEEE Trans. Power Electron., 2015, PP, (99), pp. 1–1 (doi: 10.1109/TPEL.2015.2389654).
-
4)
-
8. Ninad, N., Lopes, L.: ‘Unbalanced operation of per-phase vector controlled four-leg grid forming inverter for stand-alone hybrid systems’. Thirty-Eighth Annual Conf. on IEEE Industrial Electronics Society, IECON, October 2012, pp. 3500–3505.
-
5)
-
20. Souza, W., Severo-Mendes, M.: ‘Análise e verificação de funcionamento de uma microgrid conectada comparando os métodos de controle com o controlador proporcional + multirressonante’, XIX Brazilian Autom. Conf. (CBA), September 2012, pp. 3966–3973.
-
6)
-
16. Delghavi, M., Yazdani, A.: ‘Islanded-mode control of electronically coupled distributed-resource units under unbalanced and nonlinear load conditions’, IEEE Trans. Power Deliv., 2011, 26, (2), pp. 661–673 (doi: 10.1109/TPWRD.2010.2042081).
-
7)
-
9. Guerrero, J., 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. 994–1004 (doi: 10.1109/TIE.2007.892621).
-
8)
-
3. 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. 796–808 (doi: 10.1109/TPWRS.2009.2032049).
-
9)
-
24. Bierk, H., Albakkar, A., Nowicki, E.: ‘Harmonic reduction in the parallel arrangements of grid connected voltage source inverters’. Second Int. Conf. on Electric Power and Energy Conversion Systems (EPECS), 2011, 2011, pp. 1–6.
-
10)
-
6. De, D., Ramanarayanan, V.: ‘Decentralized parallel operation of inverters sharing unbalanced and nonlinear loads’, IEEE Trans. Power Electron., 2010, 25, (12), pp. 3015–3025 (doi: 10.1109/TPEL.2010.2068313).
-
11)
-
15. Chandorkar, M., Divan, D., Adapa, R.: ‘Control of parallel connected inverters in standalone AC supply systems’, IEEE Trans. Ind. Appl., 1993, 29, (1), pp. 136–143 (doi: 10.1109/28.195899).
-
12)
-
23. Guerrero, J., Matas, J., de Vicuña, L., et al: ‘Wireless-control strategy for parallel operation of distributed-generation inverters’, IEEE Trans. Ind. Electron., 2006, 53, (5), pp. 1461–1470 (doi: 10.1109/TIE.2006.882015).
-
13)
-
10. Guerrero, J.M., Vasquez, J.C., Matas, J., Castilla, M., de Vicuna, L.G.: ‘Control strategy for flexible microgrid based on parallel line-interactive UPS systems’, IEEE Trans. Ind. Electron., 2009, 56, (3), pp. 726–736 (doi: 10.1109/TIE.2008.2009274).
-
14)
-
18. Planas, E., Gil-de Muro, A., Andreu, J., et al: ‘Design and implementation of a droop control in d-q frame for islanded microgrids’, IET Renew. Power Gener., 2013, 7, (5), pp. 458–474 (doi: 10.1049/iet-rpg.2012.0319).
-
15)
-
22. Schonardie, M., Martins, D.: ‘Application of the dq0 transformation in the three-phase grid-connected PV systems with active and reactive power control’, IEEE Intern. Conf. on Sustain. Energy Technol. (ICSET), November 2008, pp. 18–23.
-
16)
-
1. ANEEL: ‘Procedures for distribution of electricity in the national electricity system – prodist, mod. 3 – access to the distribution system’, Electrical Energy National Agency – Aneel, 2011, .
-
17)
-
11. Li, Y.W., Kao, C.N.: ‘An accurate power control strategy for power electronics-interfaced distributed generation units operating in a low-voltage multibus microgrid’, IEEE Trans. Power Electron., 2009, 24, (12), pp. 2977–2988 (doi: 10.1109/TPEL.2009.2022828).
-
18)
-
13. Coelho, E., Cortizo, P., Garcia, P.: ‘Small-signal stability for parallel-connected inverters in stand-alone AC supply systems’, IEEE Trans. Ind. Appl., 2002, 38, (2), pp. 533–542 (doi: 10.1109/28.993176).
-
19)
-
12. Kim, J., Guerrero, J.M., Rodriguez, P., et al: ‘Mode adaptive droop control with virtual output impedances for an inverter-based flexible AC microgrid’, IEEE Trans. Power Electron., 2011, 26, (3), pp. 689–701 (doi: 10.1109/TPEL.2010.2091685).
-
20)
-
10. De Brabandere, K., Bolsens, B., Van den Keybus, J., et al: ‘A voltage and frequency droop control method for parallel inverters’, IEEE Trans. Power Electron., 2007, 22, (4), pp. 1107–1115 (doi: 10.1109/TPEL.2007.900456).
-
21)
-
7. Vechiu, I., Curea, O., Camblong, H.: ‘Transient operation of a four-leg inverter for autonomous applications with unbalanced load’, IEEE Trans. Power Electron., 2010, 25, (2), pp. 399–407 (doi: 10.1109/TPEL.2009.2025275).
-
22)
-
2. Savaghebi, M., Jalilian, A., Vasquez, J.C., Guerrero, J.M.: ‘Autonomous voltage unbalance compensation in an islanded droop-controlled microgrid’, IEEE Trans. Ind. Electron., 2013, 60, (4), pp. 1390–1402 (doi: 10.1109/TIE.2012.2185914).
-
23)
-
4. Avelar, H.J., Parreira, W.A., Vieira, J.B., Gomes de Freitas, L.C., Coelho, E.A.: ‘A state equation model of a single-phase grid-connected inverter using droop control scheme with extra phase shift control action’, IEEE Trans. Ind. Electron., 2012, 59, (3), pp. 1527–1537 (doi: 10.1109/TIE.2011.2163372).
-
24)
-
17. Souza, W., Severo-Mendes, M., Lopes, L.: ‘Microgrid units in the islanded operation mode implemented in the dSPACE DS1103’. Power Electron. Conf. (COBEP), 2013, Brazilian, October 2013, pp. 1016–1021.
http://iet.metastore.ingenta.com/content/journals/10.1049/iet-rpg.2014.0250
Related content
content/journals/10.1049/iet-rpg.2014.0250
pub_keyword,iet_inspecKeyword,pub_concept
6
6