An Enhanced Passivity-Based Control of Hybrid Energy Storage Applied to Wave Energy Conversion System

The output power of a direct-drive wave energy converter (DDWEC) is inherently influenced by the real sea state, resulting in significant intermittency. This variability poses challenges for maintaining a stable power supply to the load, thereby complicating control strategies. This paper presents the interconnection damping assessment-passivity based controller (IDA-PBC) for island microgrid applications with DDWEC and hybrid energy storage system (HESS). Unlike other control methods, IDA-PBC does not separate the control strategy into outer and inner loops. This allows for a more efficient control strategy to ensure system stability. In conjunction with passivity-based control, a nonlinear disturbance observer (NDO) is proposed to enhance the robustness of the system against parameter mismatches and variations in load conditions. This controller maintains the DC link voltage at the desired level by generating reference values for the current of the supercapacitor and the battery. HESS is utilized to address the difference in average and instantaneous power between the wave generation system and the DC load. To validate its rapid transient response and anti-disturbance performance, both simulation and experimental results are presented.