Date of Award

6-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical Engineering

First Advisor

Prof. Hassan Noura

Second Advisor

Dr. Addy Wahyudie

Third Advisor

Prof. Ali Assi

Abstract

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 emulating heaving WEC. The test bed is part of a hardware-in-the-loop system, where the developed controllers will be tested under different operating scenarios. At this stage, the machine is tested in the absence of any control strategy, instead resistive loading at various sea state conditions are applied. The results of the electrical and thermal performance of the test bed has proven successful.

Acknowledgments

First, I would like to thank my parents for their unconditional and unlimited support during this long journey. I am especially grateful to my PhD supervisor Prof. Hassan Noura who has been such a great teacher, inspiration, and mentor. Also my thanks are extended to the advisory committee, namely Dr. Addy Wahyudie and Prof. Ali Assi for their continuous and relentless guidance.

I would also like to thank the PhD examination committee for accepting to review the thesis and providing me with their valuable comments. Many thanks go out to all faculty members of the Electrical Engineering Department for their direct or indirect contribution to this work. Also, I would like to thank all lab specialists who were very helpful in providing what is needed to conduct experiments successfully. Finally, I would like to thank UAE University in general, College of Engineering in particular, for giving me this valuable opportunity to pursue my PhD.

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