Control Strategies for Improving the Performance of Heaving Wave Energy Converters

The main objective of this study is to develop control strategies to enhance the performance of single-body heaving wave energy converters (WECs). Maximizing the energy captured from sea waves while respecting the physical and thermal limitations of the WEC is of a paramount importance for any control strategy to be effective. In addition, it is desirable for the controller to be less vulnerable to model uncertainties and external disturbances. A complete wave-to-wire dynamic model has been derived for the heaving WEC. This includes models that describe the system hydrodynamic forces using the linear wave theory and models that describe the power take-off mechanism, which comprises a permanent magnet linear generator (PMLG) and the associated power converters. The proposed control strategies are stemmed from the principle of maximum power transfer, in which, the motion of the system’s reciprocating parts become in phase with the incoming sea waves. The developed controllers have been broadly classified into: reference-based and reference-less controllers depending on the availability of an optimum reference velocity trajectory to be tracked. In this work, heuristic controllers that are independent of any mathematical models are introduced such as fuzzy logic-based controllers. Moreover, model-based control strategies with low computational cost and inherent robustness capabilities are also examined, such as those strategies based on model predictive controllers. Numerical simulations are carried out to validate the developed controllers using MATLAB/Simulink. Well established control strategies such as resistive loading and compensator-based controllers are deployed to assess the effectiveness of the suggested controllers. The simulation results show that a good balance between optimum energy capturing and system constraints handling can be attained. The dissertation also presents preliminary work on constructing a novel 1.5kW PMLG experimental test bed for emula