Techno-Economic Sizing and Hierarchical Control of a Hybrid Energy Storage System for Renewable Energy Integration: A Case Study of the Apulia Region

The global transition to sustainable energy has accelerated the deployment of renewable energy sources, particularly solar photovoltaic and wind power. However, the inherent variability of these resources introduces significant stability challenges to power systems, including frequency deviations and supply-demand imbalances. This study proposes and analyzes a Hybrid Energy Storage System (HESS) that synergistically combines the high energy density of Lithium-ion batteries with the high-power density of supercapacitors. The proposed architecture is designed to address the specific grid constraints of the Apulia region in Southern Italy, a renewable energy hub where generation frequently exceeds local demand. A techno-economic sizing methodology and simulation framework are employed to dimension a 150 MW/600 MWh battery energy storage system complemented by a 492 MW/1.75 MWh supercapacitor bank for millisecond-level transient power management. A three-layer hierarchical control strategy is developed to resolve conflicting operational objectives, implementing a “Supercapacitor-First” dispatch protocol that prioritizes grid stability, followed by system restoration and economic energy arbitrage. This proposed architecture is validated through deterministic time-domain simulation; results demonstrate that the HESS raises the frequency nadir by 0.21–0.57 Hz in four contingencies, lowers the maximum rate of change of frequency from 1.56 to 0.91 Hz/s, and reduces battery throughput by 9% and micro-cycles by 19% at baseline load. The SC investment is not recovered under current Italian market rules, but it is recovered in 11 years with a European fast-frequency mechanism. Its viability therefore depends on the market remunerating fast frequency response.