Lithium-based energy storage management for DC distributed renewable energy system

Making electricity grids “smarter” and facilitating them with integration of renewable energy sources (RES) are fairly accepted as the necessary steps to achieve a sustainable power industry. However, serious concerns over reliability and performance require integration of energy storage as a critical part to buffer energy or provide arbitrage. Lithium-based battery offers high specific power/energy density, and gains popularities in many applications, such as (Plug-in) hybrid electric vehicle ((P)HEV) and renewable energy system. This paper discusses two issues: (a) integrating lithium-based battery into a multi-renewable-energy-source-feeding DC-distributed renewable energy system (DRES); (b) floating charge safety for a high voltage series-connected Li-ion battery pack. Based on the analysis of this two issues, this paper then proposes an integration strategy for lithium-based energy storage management, and the maximum cell voltage V_{Cell_max} controlled floating charge profile for long string series connected lithium-ion cells pack. An 8.4kW bi-directional multi-phase dc-dc converter is designed to validate above mentioned concepts