Latching control of a floating oscillating-water-column wave energy converter

• An optimal latching control strategy is proposed for an OWC spar-buoy.
• The optimal control is implemented within a receding horizon framework.
• Significant performance improvements are achieved with latching control.
• The practical requirements for the receding horizon time intervals are established.
• The control strategy is validated using real-time hardware-in-the-loop tests.

The OWC spar-buoy is an axisymmetric floating version of an oscillating-water-column (OWC) based device whose power take-off (PTO) system is an air turbine/generator set. Latching has been regarded as one of the most promising techniques to improve the efficiency of wave energy converters. In the case of the OWC spar-buoy, latching control is performed by opening/closing a high-speed stop valve installed in series with the turbine. The present paper has three main objectives. Firstly, to assess the performance improvements that can be achieved with a latching control strategy within a receding horizon framework. Secondly, to establish the practical requirements of this type of control by evaluating the sensitivity of the turbine power output to several receding horizon time intervals. Finally, to test and validate experimentally the proposed algorithms in a small-scale PTO test rig. All the experimental tests were performed considering irregular wave conditions.