Modelling and Control Tank Testing Validation for Attenuator Type Wave Energy Converter - Part I: Experiment Setup and Control-Oriented Modelling

Abstract

Advanced non-causal optimal control strategies have been demonstrated to significantly improve the energy output of a scale physical model of an attenuator type wave energy converter (WEC) by tank testing experiments using FloWave tank facilities in Edinburgh supported by Wave Energy Scotland's control project. The results are reported in a series of three papers, summarizing the tank testing setup, dynamic modelling, and validation of both linear non-causal optimal control (LNOC) and model predictive control (MPC) in regular and irregular waves. Compared with an optimally tuned passive damping control, both LNOC and MPC can significantly improve the energy output, by between 10% to 460%, using irregular waves with low to medium magnitude and peak periods ranging from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.7~\mathrm{s}$</tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2.8~\mathrm{s}$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1/20^{th}$</tex-math></inline-formula> scale, as shown in Part II and Part III papers. These controllers also show robust performance in spread waves and side waves which are normally encountered in real sea conditions. Furthermore, the control technologies can be transferred to other types of WECs. The results pave the way for the sea trial testing and full control system validation involving the electricity generation stage and power conditioning stage. This Part I paper will focus on the tank testing setup, the passive damping control experimental results, and the control-oriented models for the WEC. Two state-space models derived respectively from the hydrodynamic model and system identification of experimental data, are validated and compared for use on the controller designs to be presented in Part II and Part III.