Application of the Latching Control System on the Power Performance of a Wave Energy Converter Characterized by Gearbox, Flywheel, and Electrical Generator

Abstract

The latching control represents an attractive alternative to increase the power absorption of wave energy converters (WECs) by tuning the phase of oscillator velocity to the wave excitation phase. However, increasing the amplitude of motion of the floating body is not the only challenge to obtain a good performance of the WEC. It also depends on the efficiency of the power take-off system (PTO). This study aims to address the actual power performance and operation of a heaving point absorber with a direct mechanical drive PTO system controlled by latching. The PTO characteristics, such as the gear ratio, the flywheel inertia, and the electric generator, are analyzed in the WEC performance. Three cylindrical point absorbers are also considered in the present study. A wave-to-wire model is developed to simulate the coupled hydro-electro-mechanical system in regular waves. The wave energy converter (WEC) performance is analyzed using the potential linear theory but considering the viscous damping effect according to the Morison equation to avoid the overestimated responses of the linear theory near resonance when the latching control system is applied. The latching control system increases the mean power. However, the increase is not significant if the parameters that characterize the WEC provide a considerable mean power. The performance of the proposed mechanical power take-off depends on the gear ratio and flywheel. However, the gear ratio shows a more significant influence than the flywheel inertia. The operating range of the generator and the diameter/draft ratio of the buoy also influence the PTO performance.

Keywords

Wave energy converter / Point absorber / Mechanical power take-off / Flywheel / Gear ratio / Latching control