Frequency- and time-domain analysis of a multi-degree-of-freedom point absorber wave energy converter:

This study proposes a multi-degree-of-freedom wave energy converter and introduces a 6-PSS (prismatic pair–spherical pair–spherical pair) power take-off mechanism. The frequency- and time-domain dynamic models of a 3-degree of freedom wave energy converter are established. The time-domain model based on frequency-domain data is usually built upon the Cummins equation. The convolution terms in the Cummins equation are substituted by a state-space system by the frequency-domain identification method in this work. The power absorption of the wave energy converter is studied in both regular and irregular waves. It is shown that the advantages with the converter in resonance with waves are evident in regular waves and not so obvious in irregular waves. The appropriate value of power take-off damping terms has relative border range in irregular waves, which can be chosen according to the trends. Through optimization, the total power absorption in the three directions is close to 126 kW. The results indicate tha...