Comparison of Optimal Control Approximations by Mechanical Impedance Adjustment for a Wave Energy Converter

Resumen: This work compares three methods for efficiency improvement of a point absorber wave energy converter (WEC) with approximated optimal control by adjusting the mechanical impedance of the floater dynamics. The case study is a WEC based on an Archimedes wave swing prototype. The well-established phase and amplitude conditions for floaters in the frequency domain are considered as guidelines for the efficiency improvement objective for a floater with nonlinear damping. The phase condition is considered to be fulfilled by matching the natural frequency of oscillation with the dominant frequency of the incident waves. This is a feature of the mechanical structure of the WEC under study. Thus, the three methods considered aim to satisfy the amplitude condition for the WEC under study. These methods seek to correct the total damping by shaping the force produced by the electrical generator. The first method considers a linear approximation of the nonlinear damping produced by the brakes in the WEC structure. The second method imposes a linear dynamic by compensating the nonlinear damping. Finally, the third method is proposed following a variation for nonlinear resistive networks of the maximum power transfer theorem. From numerical simulations with both regular and irregular sea waves, including a sensitivity analysis of the corrected damping, the third option shows a better performance regarding energy conversion followed by the first option.

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Alejandro Gonzalez-Esculpi, Cristina Verde & Paul Maya-Ortiz. Comparison of Optimal Control Approximations by Mechanical Impedance Adjustment for a Wave Energy Converter. Memorias del Congreso Nacional de Control Automático, pp. 189-195, 2021.

Palabras clave

Wave energy, renewable energy sources, electromechanical systems, maximum power transfer

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