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CLC number: TM464

On-line Access: 2013-01-03

Received: 2012-08-08

Revision Accepted: 2012-11-01

Crosschecked: 2012-12-23

Cited: 2

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Journal of Zhejiang University SCIENCE C 2013 Vol.14 No.1 P.50-64


Analysis, design, and experimental evaluation of power calculation in digital droop-controlled parallel microgrid inverters

Author(s):  Ming-zhi Gao, Min Chen, Cheng Jin, Josep M. Guerrero, Zhao-ming Qian

Affiliation(s):  Department of Applied Electronics, Zhejiang University, Hangzhou 310027, China; more

Corresponding email(s):   calim@zju.edu.cn

Key Words:  Distributed generators, Distributed energy storages, Microgrid, Wireless parallel, Droop control, Digital control system, p-q theory

Ming-zhi Gao, Min Chen, Cheng Jin, Josep M. Guerrero, Zhao-ming Qian. Analysis, design, and experimental evaluation of power calculation in digital droop-controlled parallel microgrid inverters[J]. Journal of Zhejiang University Science C, 2013, 14(1): 50-64.

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author="Ming-zhi Gao, Min Chen, Cheng Jin, Josep M. Guerrero, Zhao-ming Qian",
journal="Journal of Zhejiang University Science C",
publisher="Zhejiang University Press & Springer",

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%T Analysis, design, and experimental evaluation of power calculation in digital droop-controlled parallel microgrid inverters
%A Ming-zhi Gao
%A Min Chen
%A Cheng Jin
%A Josep M. Guerrero
%A Zhao-ming Qian
%J Journal of Zhejiang University SCIENCE C
%V 14
%N 1
%P 50-64
%@ 1869-1951
%D 2013
%I Zhejiang University Press & Springer
%DOI 10.1631/jzus.C1200236

T1 - Analysis, design, and experimental evaluation of power calculation in digital droop-controlled parallel microgrid inverters
A1 - Ming-zhi Gao
A1 - Min Chen
A1 - Cheng Jin
A1 - Josep M. Guerrero
A1 - Zhao-ming Qian
J0 - Journal of Zhejiang University Science C
VL - 14
IS - 1
SP - 50
EP - 64
%@ 1869-1951
Y1 - 2013
PB - Zhejiang University Press & Springer
ER -
DOI - 10.1631/jzus.C1200236

Parallel operation of distributed generation is an important topic for microgrids, which can provide a highly reliable electric supply service and good power quality to end customers when the utility is unavailable. However, there is a well-known limitation: the power sharing accuracy between distributed generators in a parallel operation. Frequency and voltage droop is a well-established control method for improving power sharing performance. In this method, the active and reactive power calculations are used to adjust the frequency and amplitude of the output voltage. This paper describes the digital implementation of a droop method, and analyzes the influence of power calculation on droop method performance. According to the analysis, the performance of droop control in a digital control system is limited by the accuracy and speed of the power calculation method. We propose an improved power calculation method based on p-q theory to improve the performance of the droop control method, and we compare our new method with two traditional power calculation methods. Finally, simulation results and experimental results from a three single-phase 1-kW-inverter system are presented, which validate the performance of our proposed method.

Darkslateblue:Affiliate; Royal Blue:Author; Turquoise:Article


[1]Afonso, J.L., Freitas, M.J.S., Martins, J.S., 2003. p-q Theory Power Components Calculations. IEEE Int. Symp. on Industrial Electronics, 1:385-390.

[2]Ahn, S.J., Park, J.W., Chung I.Y., Moon S.I., Kang, S.H., Nam, S.R., 2010. Power-sharing method of multiple distributed generators considering control modes and configurations of a microgrid. IEEE Trans. Power Del., 25(3):2007-2016.

[3]Aredes, M., Akagi, H., Watanabe, E.H., Vergara Salgado, E., Encarnacao, L.F., 2009. Comparisons between the p-q and p-q-r theories in three-phase four-wire systems. IEEE Trans. Power Electr., 24(3-4):924-933.

[4]Barklund, E., Pogaku, N., Prodanovic, M., Hernandez Aramburo, C., Green, T.C., 2008. Energy management in autonomous microgrid using stability constrained droop control of inverters. IEEE Trans. Power Electr., 23(5):2346-2352.

[5]Chiang, S.J., Yen, C.Y., Chang, K.T., 2001. A multimodule parallelable series-connected PWM voltage regulator. IEEE Trans. Ind. Electr., 48(3):506-517.

[6]Chung, I.Y., Liu, W., Cartes, D.A., Collins, E.G., Moon S.I., 2010. Control methods of inverter-interfaced distributed generators in a microgrid system. IEEE Trans. Ind. Appl., 46(3):1078-1088.

[7]de Brabandere, K., Bolsens, B., van den Keybus, J., Woyte, A., Driesen, J., Belmans, R., 2007. A voltage and frequency droop control method for parallel inverters. IEEE Trans. Power Electr., 22(4):1107-1115.

[8]Diaz, G., Gonzalez-Moran, C., Gomez-Aleixandre, J., Diez, A., 2010. Scheduling of droop coefficients for frequency and voltage regulation in isolated microgrids. IEEE Trans. Power Syst., 25(1):489-496.

[9]Golestan, S., Joorabian, M., Rastegar, H., Roshan, A., Guerrero, J.M., 2009. Droop Based Control of Parallel Connected Single-Phase Inverters in d-q Rotating Frame. IEEE Int. Conf. Industrial Technology, p.1-6.

[10]Guerrero, J.M., de Vicuna, L.G., Matas, J., Castilla, M., Miret, J., 2004. A wireless controller to enhance dynamic performance of parallel inverters in distributed generation systems. IEEE Trans. Power Electr., 19(5):1205-1213.

[11]Guerrero, J.M., Garciade Vicuna, L., Matas, J., Castilla, M., Miret, J., 2005. Output impedance design of parallel connected UPS inverters with wireless load-sharing control. IEEE Trans. Ind. Electr., 52(4):1126-1136.

[12]Guerrero, J.M., Matas, J., de Vicuna, L.G., Castilla, M., Miret, J., 2006. Wireless-control strategy for parallel operation of distributed generation inverters. IEEE Trans. Ind. Electr., 53(5):1461-1470.

[13]Guerrero, J.M., Hang, L., Uceda, J., 2008. Control of distributed uninterruptible power supply systems. IEEE Trans. Ind. Electr., 55(8):2845-2860.

[14]Guerrero, J.M., Vasquez, J.C., Matas, J., Castilla, M., de Vicuna, L.G., 2009. Control strategy for flexible microgrid based on parallel line-interactive UPS systems. IEEE Trans. Ind. Electr., 36(3):726-736.

[15]Guerrero, J.M., Blaabjerg, F., Zhelev, T., Hemmes, K., Monmasson, E., Jemei, S., Comech, M.P., Granadino, R., Frau, J.I., 2010. Distributed generation: toward a new energy paradigm. IEEE Ind. Electr. Mag., 4(1):52-64.

[16]Hasanzadeh, A., Onar, O.C., Mokhtari, H., Khaligh, A., 2010. A proportional-resonant controller-based wireless control strategy with a reduced number of sensors for parallel operated UPSs. IEEE Trans. Power Del., 25(1):468-478.

[17]Hatziargyriou, N., Asano, H., Iravani, R., Marnay, C., 2007. Microgrids. IEEE Power Energy Mag., 5(4):78-94.

[18]He, J., Li, Y.W., 2011. Analysis, design, and implementation of virtual impedance for power electronics interfaced distributed generation. IEEE Trans. Ind. Appl., 47(6):2525-2539.

[19]Kroposki, B., Lasseter, R., Ise, T., Morozumi, S., Papatlianassiou, S., Hatziargyriou, N., 2008. Making microgrids work. IEEE Power Energy Mag., 6(3):40-53.

[20]Li, Y.W., Kao, C.N., 2009. An accurate power control strategy for power-electronics-interfaced distributed generation units operating in a low-voltage multi-bus microgrid. IEEE Trans. Power Electr., 24(12):2977-2988.

[21]Majumder, R., Chaudhuri, B., Ghosh, A., Majumder, R., Ledwich, G., Zare, F., 2010. Improvement of stability and load sharing in an autonomous microgrid using supplementary droop control loop. IEEE Trans. Power Syst., 25(2):796-808.

[22]Marwali, M.N., Jung, J.W., Keyhani, A., 2004. Control of distributed generation systems-part II: load sharing control. IEEE Trans. Power Electr., 19(6):1551-1561.

[23]Matas, J., Castilla, M., de Vicuña, L.G., Miret, J., Vasquez, J.C., 2010. Virtual impedance loop for droop-controlled single-phase parallel inverters using a second-order general integrator scheme. IEEE Trans. Power Electr., 25(12):2993-3003.

[24]Mohamed, Y., El-Saadany, E.F., 2008. Adaptive decentralized droop controller to preserve power sharing stability of paralleled inverters in distributed generation microgrids. IEEE Trans. Power Electr., 23(6):2806-2816.

[25]Oliveira da Silva, S.A., Novochadlo, R., Modesto, R.A., 2008. Single-Phase PLL Structure Using Modified p-q Theory for Utility Connected Systems. IEEE Power Electronics Specialists Conf., p.4706-4711.

[26]Ren, Z., Gao, M., Mo, Q., Liu, K., Yao, W., Chen, M., Qian, Z., 2010. Power Calculation Method Used in Wireless Parallel Inverters under Nonlinear Load Conditions. 25th Annual IEEE Conf. and Expo. on Applied Power Electronics, p.1674-1677.

[27]Rokrok, E., Golshan, M.E.H., 2010. Adaptive voltage droop scheme for voltage source converters in an islanded multibus microgrid. IET Gener. Transm. Distr., 4(5):562-578.

[28]Roslan, A.M., Ahmed, K.H., Finney, S.J., Williams, B.W., 2011. Improved instantaneous average current-sharing control scheme for parallel-connected inverter considering line impedance impact in microgrid networks. IEEE Trans. Power Electr., 26(3):702-716.

[29]Sun, X., Lee, Y.S., Xu, D., 2003. Modeling, analysis, and implementation of parallel multi-inverter systems with instantaneous average current sharing scheme. IEEE Trans. Power Electr., 18(3):844-856.

[30]Yang, S.Y., Zhang, C.W., Zhang, X., Cao, R.X., Shen, W.X., 2006. Study on the Control Strategy for Parallel Operation of Inverters Based on Adaptive Droop Method. IEEE Conf. on Industrial Electronics and Applications, p.1-5.

[31]Yao, W., Gao, M., Ren, Z., Chen, M., Qian, Z., 2010. Study on the Impact of the Complex Impedance on the Droop Control Method for the Parallel Inverters. Applied Power Electronics Conf. and Expo., p.1204-1208.

[32]Yao, W., Chen, M., Matas, J., Guerrero, J.M., Qian, Z., 2011. 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. Electr., 58(2):576-588.

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