Control system modelling of the Wave Star Energy's hydraulic Power Take-Off System

Wave Energy is an arising renewable energy form that pertains to the Small Hydropower generative sources. The Wave Star Energy A/S device has shown remarkable efforts through various testing in the department laboratories at 1:40 scale during 2000-2008. Completing this fact, it has been tested and grid connected via hydraulic Power Take-Off on a 1:10 scale at the Helligsø pier in the Nissum Bredning fjord since 2006 until now. Further ongoing projects for the 1:2 scale in Denmark are now at design and manufacturing stage.

This thesis initially focuses on the Hydrodynamic modeling and the experimental testing of a single Wave Star Energy floaters motion with an electromechanical Power take-off setup in the laboratory. For both studies, irregular waves serve as main input to compute the characteristic parameters for diffraction and radiation around the floater and in floaters near-field. In the experimental phase a fixed floating position initially delivers the hydrodynamic parameters. In a latter step for both simulation and experiments, the floaters position and displacement will be computed and varied while extracting power through the moving strut arm. In the main study, the control system modeling part links the mentioned subjects. Thereby, a latching strategy is implemented in code and tested for power maximization purposes. The multi-body problem will only be regarded during the equations modeling stage through the Boundary Element Method (BEM). Finally, optimum parameters are fitted out of the results via post-processing. From an electromechanical point of view, these might be such as geometrical corrections or the modification of limiting displacements and applying forces through the control system.

The concluding state of the project is the quantitative demonstration by the introduced methodology of the better efficiency for variable sea-states of the studied and tested Power take-off system. This fact will be checked versus the current hydraulics used at the current wave energy plant. This way, ameliorations for the control system and hydraulics of the ongoing projects will be proposed.