Robust Composite Controller for Stability Enhancement in Hybrid AC/DC Microgrids Incorporating Renewable Hydrogen Storage.

Abstract

The growing adoption of renewable energy sources and the development of hybrid AC/DC microgrid architectures have significantly improved the flexibility, reliability, and energy efficiency of modern power systems. These microgrids are particularly valuable in distributed generation environments, where diverse energy sources like solar, wind, battery storage, and hydrogen systems are integrated. However, maintaining stable operation and controlling power flow within these systems remains a key technical challenge due to the intermittent nature of renewable energy and the complex dynamics between AC and DC subsystems. In this thesis, we propose a robust composite control strategy that combines terminal sliding mode controller (TSMC) with backstepping controller (BSC). This approach, known as terminal sliding mode backstepping controller (TSMBC), is designed to enhance system stability, improve dynamic response, and maintain voltage regulation under varying load and generation conditions. To assess its effectiveness, the proposed TSMBC controller is compared with an existing method, the existing double integral sliding mode controller (EDISMC), through detailed simulations carried out in MATLAB/Simulink. The simulation results clearly demonstrate that TSMBC offers superior performance across several important metrics. Specifically, TSMBC achieved up to 100% reduction in overshoot and up to 99% improvement in settling time, resulting in significantly faster stabilization and enhanced transient response in most scenarios. In contrast, the existing EDISMC controller often exhibited delayed response and higher overshoot values. These improvements were consistent across a wide range of components, including photovoltaic (PV) units, permanent magnet synchronous generators (PMSGs), battery energy storage systems (BESS), DC/AC loads, electrolyzer, PEM fuel cell and hydrogen storage systems. Overall, the proposed control strategy proves to be more effective, adaptive, and resilient, supporting stable operation even under fluctuating power conditions.