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.
Highlights
The results show an approximately 2 percent increase in benefit/cost for DC-coupling than AC-coupling
The generated PV power, which is common for all the layouts, is shown in the figure
Theefficiency efficiencycomparison comparison three different layouts of power conversion systems can be used in large power plants providing primary frequency reserve and that can be used in large PV+battery energy storage system (BESS) power plants providing primary frequency reserve and energy energyshifting shiftingservice serviceto tothe thegrid gridwas wascarried carriedout
Summary
Grid-connected PV plants are non-dispatchable energy sources that are controlled in order to inject the maximum available power into the grid. Due to their operating characteristics, PV plants cannot usually provide the control and regulation services that conventional sources can do and, can impact the voltage and the stability of the electrical system [1,2,3]. A typical PV+BESS power plant, consists of multiple PV arrays, power electronic converters, and storage units which can contribute to grid stability and reliability through sophisticated gridfriendly controls [6,7], supplementing (or even replacing in the long term) conventional generators [8]. The development of advanced power controls can enable PV to become a provider of a wide range of grid services, including spinning reserves, load following, voltage support, ramping control, frequency response, and variability smoothing
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