Garcia Rosa, Paula B. and Ringwood, John and Fosso, Olav B. and Molinas, Marta (2019) The Impact of Time–Frequency Estimation Methods on the Performance of Wave Energy Converters Under Passive and Reactive Control. IEEE Transactions on Sustainable Energy, 10 (4). pp. 1784-1792. ISSN 1949-3029

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Abstract

A number of wave energy controllers tune the power take-off (PTO) system to the frequency of incident waves. Since real ocean waves are non-stationary by nature and not defined by a single frequency component, the PTO can be either tuned at a constant frequency characterized by the local spectrum or continuously tuned to a representative wave frequency. In either case, a time-frequency representation of the waves is expected since the wave profile changes over time. This paper discusses about the PTO tuning problem for passive and reactive controllers, in real waves, by comparing different methods for time-varying frequency estimation: the extended Kalman filter (EKF), frequency-locked loop (FLL), and Hilbert-Huang transform (HHT). The aim is to verify the impact of such methods on the absorbed and reactive powers, and the PTO rating. It is shown that the mean estimated frequency of the EKF and FLL, converges, respectively, to the mean centroid frequency and energy frequency, of the excitation force spectrum. Moreover, the HHT mean frequency has no correlation with the spectral statistical properties. A comparison of the energy absorbed shows that up to 37% more energy is obtained with the HHT over the other estimation methods. Numerical simulations are performed with sea elevation data from the Irish coast.

Item Type:	Article
Additional Information:	This is the postprint version of the published article. Content may have changed prior to final publication. Citation information: DOI 10.1109/TSTE.2018.2870966, IEEE Transactions on Sustainable Energy
Keywords:	Energy harvesting, wave power, frequency estimation, control systems
Academic Unit:	Faculty of Science and Engineering > Electronic Engineering Faculty of Science and Engineering > Research Institutes > Centre for Ocean Energy Research
Item ID:	12414
Identification Number:	https://doi.org/10.1109/TSTE.2018.2870966
Depositing User:	Professor John Ringwood
Date Deposited:	10 Feb 2020 15:23
Journal or Publication Title:	IEEE Transactions on Sustainable Energy
Publisher:	Institute of Electrical and Electronics Engineers (IEEE)
Refereed:	Yes
URI:	Publisher
Use Licence:	This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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