Optimized Planning of Battery Storage for Substation Auxiliary Power

Traditionally, these systems are based on a combination of AC supply sources, rectifiers, leadacid or NiCd batteries, uninterruptible power supplies, and diesel generators. While robust and proven, such solutions face increasing challenges related to maintenance costs, environmental impact, space requirements, and limited flexibility. Recent advances in lithium-ion battery energy storage systems (BESS) offer a promising alternative that can enhance reliability while enabling additional functions such as electricity cost optimization and integration with renewable generation. The goal of this paper is to develop a comprehensive planning methodology for integrating battery storage systems into substation self-consumption systems.

The proposed approach focuses on ensuring uninterrupted AC and DC auxiliary supply while extending the role of BESS to support optimized electricity procurement in substations that also include photovoltaic (PV) generation and electric vehicle (EV) charging infrastructure. The paper first reviews conventional auxiliary power supply architectures used in Slovenian substations and identifies their limitations. It then presents a step-by-step methodology for

BESS planning, covering technology selection, system integration, definition of operating scenarios, capacity sizing, and assessment of impacts on substation operation. A detailed comparison of battery technologies (lead-acid, NiCd, redox flow, and lithium-ion variants) is carried out using weighted criteria emphasizing safety, cycle life, energy density, specific power, and cost. Based on this analysis, lithium-ion technologies—particularly lithium iron phosphate (LFP) and lithium titanate (LTO)—are identified as the most suitable for substation applications, with LTO highlighted as the preferred option where safety, durability, and intensive cycling are critical. The methodology is demonstrated on a real Slovenian substation case study. Overall, the study concludes that LTO-based BESS represents a safe, reliable, and economically sound solution for modern substation self-consumption systems, particularly in the context of increasing electrification and renewable integration.