Efficiency Comparison of DC and AC Coupling Solutions for Large-Scale PV+BESS Power Plants

Francesco Lo Franco, Antonio Morandi, Pietro Raboni and Gabriele Grandi
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Francesco Lo Franco: Department of Electrical, Electronic and Information Engineering, University of Bologna, 40136 Bologna, Italy
Antonio Morandi: Department of Electrical, Electronic and Information Engineering, University of Bologna, 40136 Bologna, Italy
Pietro Raboni: NHOA, 20158 Milano, Italy
Gabriele Grandi: Department of Electrical, Electronic and Information Engineering, University of Bologna, 40136 Bologna, Italy

Energies, 2021, vol. 14, issue 16, 1-22

Abstract: In large-scale photovoltaic (PV) power plants, the integration of a battery energy storage system (BESS) permits a more flexible operation, allowing the plant to support grid stability. In hybrid PV+BESS plants, the storage system can be integrated by using different power conversion system (PCS) layouts and different charge–discharge strategies. In the AC-coupling layout, the BESS is connected to the ac-side of the system through an additional inverter. In the DC-coupling layout, the BESS is connected to the dc-side, with or without a dedicated dc–dc converter, and no additional inverter is needed. Referring to a 288 MWp PV plant with a 275 MWh BESS, this paper compares the PCS efficiency between AC- and DC-coupling solutions. The power injected into the grid is obtained considering providing primary power-frequency regulation services. A charging and discharging strategy of the BESS is proposed to ensure cyclic battery energy shifting. The power flows in the different components of the system that are obtained under realistic operating conditions, and total energy losses and annual average efficiency are calculated accordingly. Finally, results show a higher efficiency of DC-coupling compared to the AC-coupling layout.

Keywords: battery energy storage system (BESS); photovoltaic; power conversion system (PCS); renewable energy sources (RES); solar plus storage sizing; grid-connected PV plant (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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