A Robust Faster Joint Control of a Direct-Drive Wave Energy Converter Combined With Supercapacitor and Battery Energy Storage

Undersea direct-drive wave energy converters (UDDWEC) have the advantages of high-energy absorption and good resistance to wind and waves. This article proposes a robust faster joint control for the hybrid energy storage system (HESS) in the application of islanded microgrid with UDDWEC. Wave power systems capture maximum power under different conditions, considering regular and irregular waves. The interconnection damping assessment-passivity-based controller (IDA-PBC) used as an outer voltage controller regulates the dc link voltage to the desired value by generating reference values for the supercapacitor current and the battery current. The model predictive control (MPC) used as an inner controller tracks the reference state variables generated by the outer voltage controller. HESS is employed to mitigate the discrepancy in average and instantaneous power between the wave generation system and the dc load. The output of the wave power system is investigated under frequency and magnitude variations in wave elevation. It was verified that the system can maintain stability quickly when the load varies. The proposed control structure is verified through simulation and experimental results.