Energy flow optimization for a hybrid DC-microgrid integrating hydrogen production via a PEM electrolyzer and fuel cell backup

This paper proposes an advanced nonlinear control strategy coupled with energy flow optimization ( E F O ) for a hybrid D C -microgrid integrating a photovoltaic ( P V ) generator, a lithium-ion battery energy storage system ( B E S S ), a proton exchange membrane ( P E M ) electrolyzer for hydrogen production, and a P E M fuel cell for backup power. All subsystems are interconnected, via power electronic converters, to a common D C -bus supplying diverse loads. The proposed control strategy ensures five key objectives: tight D C -bus voltage regulation, optimal power extraction from P V ( M P P T / A P P T ), intelligent battery operation in constant current/voltage ( C C / C V ) modes, and specified hydrogen production tracking, and secure fuel cell activation under power deficit. An integrated energy-management algorithm dynamically manages power sharing among sources and storage based on renewable availability and battery state-of-charge ( S o C ). Nonlinear backstepping controllers are designed for all converters ( P V -side DC/DC boost, bidirectional B E S S D C / D C buck-boost, electrolyzer D C / D C buck, and fuel-cell D C / D C buck) to guarantee stability and fast dynamics. Simulation results across multiple operating scenarios show smooth mode transitions, reduced battery charge/discharge cycling, accurate hydrogen-production tracking, tight D C -bus regulation, and reliable continuity of supply, confirming the effectiveness and robustness of the proposed control and E F O framework.