Coordinated PI-Sliding Mode Control and Real-Time Hardware-in-the-Loop Validation of a Battery-Less Solar PV-Hydrogen DC Microgrid

Battery-less hydrogen-based DC microgrids have emerged as a promising solution for improving the operational flexibility of renewable energy systems by complementing intermittent photovoltaic (PV) generation with long-duration hydrogen energy storage. This paper presents a coordinated energy management framework for a standalone DC microgrid integrating a solar PV array, a Proton Exchange Membrane (PEM) electrolyser, and a PEM fuel cell. Unlike conventional battery-assisted architectures, the proposed system coordinates hydrogen production and power recovery without electrochemical battery storage, thereby simplifying the energy storage structure for long-duration applications. Maximum PV power extraction is achieved using a Perturb and Observe (P&O) maximum power point tracking algorithm implemented through a boost converter. A cascade PI-Sliding Mode Control (PI-SMC) strategy regulates the fuel cell boost converter, where the outer PI voltage loop generates the reference current and the inner sliding mode controller ensures robust current tracking and DC-link voltage regulation under irradiance variations. An SMC-based buck converter regulates the electrolyser input to enable stable hydrogen production during surplus PV generation, while a PI-controlled buck converter maintains the load voltage. The proposed coordinated control strategy is validated through detailed MATLAB/Simulink simulations and real-time execution on an OPAL-RT OP4610XG Hardware-in-the-Loop platform. The results demonstrate improved transient performance, reduced DC-link voltage deviation, and reliable power management during rapid irradiance changes. These findings demonstrate the feasibility of integrating coordinated PI-SMC control with a battery-less PV-hydrogen DC microgrid and provide realtime validation of its stable operation for renewable energy applications.