A feedback latching controller for two-body wave energy converters under irregular wave conditions

Latching control is considered to be an effective way to improve the energy absorption of a wave energy converter (WEC). Recently, a latching control method was realized in a hydraulic power take-off (PTO) system and was demonstrated to be effective in one-body WECs. However, the effectiveness of latching control for two-body WECs still needs to be tested. In this paper, a feedback latching controller is proposed for a conceptual two-body WEC. In this conceptual design, a permanent-magnet linear generator (PMLG) is adopted as the PTO system, and a pure water hydraulic cylinder system is designed for performing the latching control. A feedback control strategy based on the measurement of latching force is established, formulated and tested numerically under realistic irregular wave conditions. The effects of the wave peak period and the PTO damping coefficient on the effectiveness of the latching control is also investigated. The results indicate that the proposed feedback latching control is effective for improving the annual power absorption of the two-body WEC. Furthermore, compared to another latching control, the proposed control is more practical because it does not require any knowledge of the wave conditions or the dynamics of the whole WEC system.