The Effect of Viscosity on the Maximisation of Electrical Power from a Wave Energy Converter under Predictive Control

Abstract

In this paper, the non-linear effects of viscosity on the performance of a Wave Energy Converter (WEC) system are analysed. A standard linear Model Predictive Control (MPC) is used to show the negative effects that the unaccounted non-linear viscosity force in the hydrodynamic system has on the power absorption. A non-linear MPC (NLMPC) is then implemented, where the non-linear viscosity effects are included in the optimisation. A linear drag coefficient estimate of the non-linear viscosity is then included in the linear MPC; creating a Linear Viscous Model Predictive Control. When constraints are incorporated, it is shown that a single choice of the linear viscous drag coefficient for use within the linear MPC can provide comparable results to the non-linear MPC approach, over a wide range of sea states.

An Analytical and Numerical Sensitivity and Robustness Analysis of Wave Energy Control Systems

“…2) Considered over a wider range of error values, the sensitivity function in (47) is not symmetric with respect to the sign of the error. More precisely, overestimation of the radiation damping terms has a relatively small impact on power production, compared to underestimation of the same magnitude, also confirmed by the simulation results in [29]. For example, overestimating the damping coefficient by 40% results in a power loss of less than 10%.…”