Optimal controller tuning for a nonlinear moored wave energy converter via non-parametric frequency-domain techniques

Wave energy production is a challenging problem, mainly due to the intrinsic complex nature of wave energy conversion (WEC) devices and their development environment. Although mooring systems are generally considered an essential part of a WECs, being able to solve the station-keeping problem, their influence in power-related problems can not be neglected. This study analyses the energy-maximizing control design procedure of a pendulum-based WEC, explicitly taking into account the influence of the mooring system. To achieve such an objective, a representative non-parametric model of the moored WEC is obtained via system identification procedures, and the PTO control parameter synthesis is achieved by exploiting the principle of impedance-matching. Simulations and computation of control parameters have been conducted with and without the mooring system, in order to quantify the importance of the mooring inclusion when addressing power generation problems.