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Towards realistic non-linear receding-horizon spectral control of wave energy converters
Mérigaud, Alexis; Ringwood, John
Non-linear, power-maximising control of wave energy converters (WECs) can be achieved within a receding-horizon control framework, whereby an upper loop calculates a reference trajectory in real-time, ensuring maximal power absorption under operational constraints, while a tracking loop drives the device along the generated trajectory. This paper articulates the four fundamental components of such a control strategy: reference generation calculations, tracking loop, and wave excitation estimation and forecasting. The upper-loop optimisation problem is efficiently solved through a Fourier spectral method, taking into account non-linear dynamics and constraints. Tracking is achieved through a linear state feedback, combined with a non-linear feed-forward term. An extended Kalman filter is used for excitation force estimation, based on noisy WEC position and acceleration measurements. Finally, wave excitation forecasts are based on a linear predictor, whose coefficients are derived from the wave spectrum (on a sea-state-by-sea-state basis). The practical issues and trade-offs, which arise when the four components listed above are combined within a practical implementation, are investigated by means of realistic numerical simulations, using a WEC model comprising a combination of static and velocity-dependent non-linear forces.
Keyword(s): Wave energy converters; Power maximisation; Optimal control; Receding-horizon control; Fourier spectral control; Constraints; Non-linear systems; Trajectory tracking; Extended Kalman filter; Measurement noise; Gaussian process
Publication Date:
2018
Type: Journal article
Peer-Reviewed: Yes
Institution: Maynooth University
Citation(s): Mérigaud, Alexis and Ringwood, John (2018) Towards realistic non-linear receding-horizon spectral control of wave energy converters. Control Engineering Practice, 81. pp. 145-161. ISSN 0967-0661
Publisher(s): Elsevier
File Format(s): other
Related Link(s): http://mural.maynoothuniversity.ie/12545/1/JR-Realistic-2018.pdf
First Indexed: 2020-04-02 06:00:45 Last Updated: 2020-04-02 06:00:45