Hierarchical Control Strategy for Maximising Power Conversion in Heaving Wave Energy Converters

This paper considers hierarchical control strategy (HCS) for maximising power conversion between mechanical and electrical powers in heaving wave energy converters. The maximisation conversion were obtained by designing the optimum reference for the buoy This reference were found by relating the mechanical and electrical models of the power-takeoff (PTO) device. A simple look-up table of the intrinsic resistance constant was obtained as function of wave's significant height and peak frequency. A Robust PID controller was used to track this reference. The PID controller was tuned using complex polynomial stabilisation method to convert the robust performance specification into a set of linear programming problem. The interesting feature of the method is all (not only one) set of PID parameters, which satisfies the robust performance, were found. Finally, the simulation results were presented to verify the control objectives.