Latching control using optimal control method for a raft-type wave energy converter

The method of efficient wave energy harvesting is a significant research field. As a kind of phase control strategy, latching control has been widely applied to point-absorption wave energy converters (WECs). However, the determination of latching duration is a difficult problem especially when the WEC is a multi-degree-of-freedom (DOF) system or includes multiple oscillators. This paper relates to latching control for a raft-type WEC with multiple DOFs and including two oscillators. The control law between latching and unlatching is decided by using the optimal control method, which avoids computing the latching duration directly. Simulations are performed to evaluate how large the benefit that latching control can bring to the raft-type WEC is. Results show that the benefit in terms of ratio between average captured power with latching control and that without control can reach 10.54 in regular waves, whereas it achieves 5.23 in random seas. Furthermore, the influence of wave parameters on the benefit is investigated.