Modelling and Control of Parallel-Connected Transformerless Inverters for Large Photovoltaic Farms

Abstract

[EN] This paper presents a control structure for transformerless photovoltaic inverters connected in parallel to manage photovoltaic fields in the MW range. Large photovoltaic farms are usually divided into several photovoltaic fields, each one of them managed by a centralized high power inverter. The current tendency to build up centralized inverters in the MW range is the use of several transformerless inverters connected in parallel, a topology that provokes the appearance of significant zero-sequence circulating currents among inverters. To eliminate this inconvenience, this paper proposes a control structure that avoids the appearance of circulating currents by controlling the zero-sequence component of the inverters. A second contribution of the paper is the development of a model of n parallel-connected inverters. To validate the concept, the proposed control structure has been applied to a photovoltaic field of 2 MW managed by four 500 kW photovoltaic inverters connected in parallel.This work is supported by the Spanish Ministry of Economy and Competitiveness (MINECO), the European Regional Development Fund (ERDF) under Grant ENE2015-64087-C2-2-R and the Spanish Ministry of Education (FPU15/01274).Liberos-Mascarell, MA.; González-Medina, R.; Garcerá, G.; Figueres Amorós, E. (2017). Modelling and Control of Parallel-Connected Transformerless Inverters for Large Photovoltaic Farms. Energies. 10(8):1-25. https://doi.org/10.3390/en10081242S125108Pazheri, F. R., Othman, M. F., & Malik, N. H. (2014). A review on global renewable electricity scenario. Renewable and Sustainable Energy Reviews, 31, 835-845. doi:10.1016/j.rser.2013.12.020Subudhi, B., & Pradhan, R. (2013). A Comparative Study on Maximum Power Point Tracking Techniques for Photovoltaic Power Systems. IEEE Transactions on Sustainable Energy, 4(1), 89-98. doi:10.1109/tste.2012.2202294Borrega, M., Marroyo, L., Gonzalez, R., Balda, J., & Agorreta, J. L. (2013). Modeling and Control of a Master–Slave PV Inverter With N-Paralleled Inverters and Three-Phase Three-Limb Inductors. IEEE Transactions on Power Electronics, 28(6), 2842-2855. doi:10.1109/tpel.2012.2220859Araujo, S. V., Zacharias, P., & Mallwitz, R. (2010). Highly Efficient Single-Phase Transformerless Inverters for Grid-Connected Photovoltaic Systems. IEEE Transactions on Industrial Electronics, 57(9), 3118-3128. doi:10.1109/tie.2009.2037654PowerGate Plus 500 kWhttp://www.satcon.comAgorreta, J. L., Borrega, M., López, J., & Marroyo, L. (2011). Modeling and Control of $N$ -Paralleled Grid-Connected Inverters With LCL Filter Coupled Due to Grid Impedance in PV Plants. IEEE Transactions on Power Electronics, 26(3), 770-785. doi:10.1109/tpel.2010.2095429Power Electronicshttp://www.power-electronics.comPVS980—1818 to 2091 kVAhttp://new.abb.comInfineon, Central Inverter Solutionshttps://www.infineon.com/cms/en/applications/solar-energy-systems/central-inverter-solutions/Xiao, H., Xie, S., Chen, Y., & Huang, R. (2011). An Optimized Transformerless Photovoltaic Grid-Connected Inverter. IEEE Transactions on Industrial Electronics, 58(5), 1887-1895. doi:10.1109/tie.2010.2054056Mazumder, S. K. (2003). A novel discrete control strategy for independent stabilization of parallel three-phase boost converters by combining space-vector modulation with variable-structure control. IEEE Transactions on Power Electronics, 18(4), 1070-1083. doi:10.1109/tpel.2003.813770Ching-Tsai Pan, & Yi-Hung Liao. (2008). Modeling and Control of Circulating Currents for Parallel Three-Phase Boost Rectifiers With Different Load Sharing. IEEE Transactions on Industrial Electronics, 55(7), 2776-2785. doi:10.1109/tie.2008.925647Ogasawara, S., Takagaki, J., Akagi, H., & Nabae, A. (1992). A novel control scheme of a parallel current-controlled PWM inverter. IEEE Transactions on Industry Applications, 28(5), 1023-1030. doi:10.1109/28.158825Figueres, E., Garcera, G., Sandia, J., Gonzalez-Espin, F., & Rubio, J. C. (2009). Sensitivity Study of the Dynamics of Three-Phase Photovoltaic Inverters With an LCL Grid Filter. IEEE Transactions on Industrial Electronics, 56(3), 706-717. doi:10.1109/tie.2008.2010175Mohd, A., Ortjohann, E., Hamsic, N., Sinsukthavorn, W., Lingemann, M., Schmelter, A., & Morton, D. (2010). Control strategy and space vector modulation for three-leg four-wire voltage source inverters under unbalanced load conditions. IET Power Electronics, 3(3), 323. doi:10.1049/iet-pel.2008.0281Albatran, S., Fu, Y., Albanna, A., Schrader, R., & Mazzola, M. (2013). Hybrid 2D-3D Space Vector Modulation Voltage Control Algorithm for Three Phase Inverters. IEEE Transactions on Sustainable Energy, 4(3), 734-744. doi:10.1109/tste.2013.224568