The integration of Battery Energy Storage Systems (BESS) in microgrids or islanded systems provides an enabler for generation decarbonization, through the possibility of maximizing the share of renewable sources and thus the reduction of fossil fuels consumption. Furthermore, the integration of BESS helps providing the stability required to face the challenges of energy transition, the intermittency of distributed renewable resources and electrification, through its capability of improving grid resilience and safety, responding to system outages and preventing blackouts.

The Azores archipelago has nine small independent electrical systems, without any capability of exporting or importing energy, since the electrical interconnections between islands are expensive and not economically viable. EDA - Electricidade dos Açores, the system operator, was willing to assess the technical and economic viability of integrating BESS in their islanded systems. The challenges were to increase the share of renewable generation by reducing their conventional generation dependency, while ensuring the reliability of the electrical system.
Siemens Power Technologies International (PTI) developed a three-application methodology with the objective of assessing the feasibility of this integration, as well as providing the optimal BESS sizing for each use case:

• Spinning reserve replacement: the BESS replaces the spinning reserve of thermal units, whilst ensuring grid stability.
• Primary frequency regulation: unbalance events due to the intermittency of renewable generation must be covered quickly by the BESS.
• Integration of renewables: the BESS allows to store or release the surplus of energy resulting from mismatches between generation and demand.

For complying with the applications mentioned above, some analyzes were made through the usage of planning and simulation software to guarantee the BESS correct sizing and technical requirements:

• Techno-economic analysis: Simulation of different energy balance scenarios using PSS®DE to obtain key technical and economic KPIs.
• Short-circuit analysis: PSS®SINCAL short-circuit analysis considering different scenarios of operation for the electrical system.
• Protection System analysis: Assessment of the protection system in PSS®SINCAL for future scenarios with BESS. Recommendation of new settings, if needed.
• Dynamic analysis: RMS and EMT transient analysis based in PSS®E and PSCAD simulations considering different events and perturbations.

This paper intends to go in detail through each of these applications, outlining the methodology and considerations made through each analysis, as well as the challenges and limitations imposed by software state-of-the-art.