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Results for “BESS control”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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Hierarchical Control of Distributed Battery Energy Storage System in a DC Microgrid

This paper presents a novel hierarchical control approach of a DC microgrid (DCMG) which is supplied by a distributed battery energy storage system (BESS). With this approach, all battery units distributed in the BESS can be controlled to discharge with accurate current sharing and state-of-charge (SoC) balancing. Similar to other hierarchical control approaches used in DCMGs, this approach consists of three levels: (1) primary control, (2) secondary control and (3) tertiary control. This work includes defining a unit control error (UCE) at the secondary control level and evaluating current sharing weights at tertiary control level. A centralized controller at secondary control level is designed to detect the UCEs of each battery unit, and to restore the average voltage of a DCMG and control battery current sharing simultaneously. The distributed battery units share the load current in a DCMG based on weights. These weights are evaluated at the tertiary control level based on battery SoCs. The approach’s effectiveness was confirmed in digital simulation tests with the same simulation model as used in the NASA AMPS Modular Hardware Emulator.

Jing Zhang↗
NASA NTRS1982

Civil (French/US) certification of the Coast Guard's HH-65A Dauphin

Certification programs with particular emphasis on handling qualities requirements are described. A dynamic simulator was designed and constructed to support and verify the dynamic aspects of the avionics system, particularly the Automatic Flight Control System (AFCS). The role of the Dynamic Simulator is discussed.

Hart, J. C.↗
NASA NTRS2013

Shape, Density, and Geology of the Nucleus of Comet 103P/Hartley 2

Data from the Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) mission show Comet 103P/Hartley 2 is a bi-lobed, elongated, nearly axially symmetric comet 2.33 km in length. Surface features are primarily small mounds <40 m across, irregularly-shaped smooth areas on the two lobes, and a smooth but variegated region forming a “waist” between the two lobes. Assuming parts of the comet body approach the shape of an equipotential surface, the mean density of Hartley 2 is modeled to be 200–400 kg /cubic m.. Such a mean density suggests mass loss per orbit of >1%. The shape may be the evolutionary product of insolation, sublimation, and temporary deposition of materials controlled by the object’s complex rotation.

Extrasolar↗
NASA NTRS2021

Atmospheric Blocking Drives Recent Albedo Change Across the Western Greenland Ice Sheet Percolation Zone

Greenland Ice Sheet (GrIS) albedo has decreased over recent decades, contributing to enhanced surface melt and mass loss. However, it remains unclear whether GrIS darkening is due to snow grain size increases, higher concentrations of light-absorbing impurities (LAIs), or a combination. Here, we assess albedo controls in the western GrIS percolation zone using in situ albedo, LAI, and grain size measurements. We find a significant correlation between albedo and snow grain size (p < 0.01), but not with LAIs. Modeling corroborates that LAI concentrations are too low to significantly reduce albedo, but larger grain sizes could reduce albedo by at least ∼3%. Strong atmospheric blocking increases grain sizes and reduces albedo through increased surface temperature, fewer storms, and higher incoming shortwave radiation. These findings clarify the mechanisms by which anomalously strong blocking contributed to recent GrIS albedo decline and mass loss, highlighting the importance of improving projections of future blocking.

Gabriel Lewis↗