Hierarchical control combined with higher order sliding mode control for integrating wind/tidal/battery/hydrogen powered DC offshore microgrid

Abstract

Due to the intermittent nature of renewable energy sources, energy storage devices play a key role in achieving power balance for microgrid. To reduce the overall carbon footprint, this paper considers fuel cells and batteries as auxiliary sources with wind and tidal energy as primary sources. A two-stage control system has been designed, which has been subdivided into system-level and local-level control systems. The system-level control includes an energy management system that optimizes load distribution, minimizes system cost, and meets battery state of charge and hydrogen level constraints. To make the microgrid independent and minimize transportation costs, on-site hydrogen production has been deployed using an electrolyzer system. At the local level, a fast reaching law-based terminal sliding mode controller has been implemented for accurate and robust tracking of the references provided by the system-level control. The stability of the proposed framework has been validated using the Lyapunov stability criteria. The proposed 600 V and 400 kW microgrid structure has been realized using MATLAB/Simulink simulations. Furthermore, the effectiveness of the proposed control scheme has been compared with PID and ITSMC in terms of accuracy and robustness under both power deficit and surplus modes. Finally, the real-life efficacy has been validated by utilizing controller hardware-in-loop experiments.