Latching Control Strategies for a Heaving Buoy Wave Energy Generator in a Random Sea

Abstract : This paper addresses the latching control of wave energy converters. The principle of this control approach is to bring the wave energy generator into resonance with the incident wave using a clamping mechanism. Maximum energy extraction is the control objective. The main challenge in any latching control scheme is to calculate the precise time when to release the device after it has been locked at zero velocity. At the example of a generic heaving buoy device and using real wave data, three latching strategies are compared to a PI velocity control. The simplest considered latching strategy releases the device as soon as the wave force reaches a certain threshold. The other strategies use a short-term wave prediction in order to calculate the latching timing. Imperfect wave predictions based on AR models and imperfect mechanical to electrical and electrical to mechanical power conversions are taken into account. While the imperfect wave predictions impact the achievable performance with the predictive latching strategies, the imperfect power conversions have a high impact on the PI velocity control due to its reactive power flow.