Optimal Design and Modeling of a Hybrid Energy Storage System Including Battery and Hydrogen in DC Microgrids

This paper presents a hybrid Energy Storage System (ESS) for DC microgrids, highlighting its potential for supporting future grid functions with high Renewable Energy Sources (RESs) penetration. While hydrogen ESS provides long-term energy stability, it typically has slower response times than batteries. Integrating hydrogen and battery storage can deliver sustained energy and effectively manage microgrid demand and surplus. Key challenges include integrating power electronics with fuel cell technology for efficient renewable energy conversion. This paper presents a hybrid ESS with 1 kV DC bus voltage. The hydrogen and battery ESSs, along with their converters and control are modeled using MATLAB Simulink. The optimization technique using Mixed Integer Linear Programming (MILP) in CVX-MATLAB aims to minimize operational and maintenance costs while maximizing profit from energy sales during periods of low generation and high demand. The system is validated through Typhoon Hardware-In-the-Loop (HiL) testing, showing high converter efficiencies of > 95%. Analyses with RESs and the grid (including Monte Carlo sensitivity analysis), using commercial and community scale load profiles, demonstrate annual returns of 17.72% and 16.54% for hydrogen ESS, and 17.13% and 18.54% for the hybrid system, including battery ESS, with full recovery of initial investment costs within 6 years.