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.
Offshore wind turbine near wakes can extend downstream up to 5D due to low atmospheric turbulence intensities. They are characterised by strong velocity deficits, a transitioning Gaussian shape, and strong added turbulence intensities. Classical analytical wake models are still used due to their low computational costs, but they mainly focus on far-wake characteristics. A super-Gaussian wake model valid in near-and far-wake regions has recently been developed at IFP Energies nouvelles. This wake model requires calibration and validation. To this end, large-eddy simulations of the large DTU-10MW reference wind turbine under different neutrally stratified atmospheric flows are carried out with the LES Meso-NH model. A database is generated based on these results and used to calibrate and validate the super-Gaussian model.
An extensive code-to-code comparison among DIEGO, DLW and HAWC2 has been performed on a floating wind turbine (modified version of UMaine floater with IEAWIND 15MW wind turbine). In total, 10 cases are compared, and a few key results of this comparison are reported in this paper. From the comparisons, it is clearly seen that the results predicted by the three codes are generally agreed well despite some differences in specific degrees of freedom like roll, sway and yaw for the extreme load case, which requires additional investigations.
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