An Energy-Maximising MPC Solution to the WEC Control Competition

2019 ◽  
Author(s):  
Paolino Tona ◽  
Guillaume Sabiron ◽  
Hoai-Nam Nguyen
Keyword(s):  
Real Time ◽  
Electric Energy ◽  
Estimation Algorithm ◽  
Wave Force ◽  
Irregular Waves ◽  
Wave Excitation ◽  
Force Prediction ◽  
Force Moment ◽  
Excitation Force ◽  
Wave Excitation Force

Abstract The WEC Control Competition is a benchmark devised to compare energy-maximising controllers for wave energy converters, first in simulation, then in real time, using a scale device in a tank test situation. For the first round of the competition, the evaluators have provided a model of a leg of a Wavestar-like device, in the WEC-Sim simulation environment. The evaluation is based on an energy-related criterion computed on six irregular waves. IFPEN’s solution is an energy-maximising model predictive control (MPC), composed of an estimation algorithm for wave excitation force moment, using measurements (or estimations) of float displacement and velocity and PTO moment; an algorithm for short-term wave force prediction from present and past wave excitation force estimates, where no information about wave elevation is used; a real-time compatible MPC algorithm using wave force prediction, which maximises the average produced electric energy, taking into account the nonlinear PTO efficiency law.

Wave-Energy Conversion Through Relative Motion Between Two Single-Mode Oscillating Bodies

1999 ◽  
Vol 121 (1) ◽  
pp. 32-38 ◽  
Author(s):  
J. Falnes
Keyword(s):  
Energy Conversion ◽  
Relative Motion ◽  
Wave Energy ◽  
Load Force ◽  
Wave Forces ◽  
Equivalent System ◽  
Wave Excitation ◽  
Excitation Force ◽  
Two Bodies ◽  
Wave Excitation Force

Wave-energy converters (WECs) need a reaction source against which the wave forces can react. As with shore-based WECs, sometimes also floating WECs react against a fixed point on the seabed. Alternatively, for a floating WEC, force reaction may be obtained by utilizing the relative motion between two bodies. A load force for energy conversion is assumed to be applied only to this relative motion. It is assumed that either body oscillates in one mode only (mostly, the heave mode is considered here). The system, if assumed to be linear, is proved to be phenomenologically equivalent to a one-mode, one-body system, for which the wave excitation force equals the force which is necessary to apply between the two bodies in order to ensure that they are oscillating with zero relative motion. It is discussed how this equivalent excitation force and also the intrinsic mechanical impedance of the equivalent system depend on the mechanical impedances for the two separate bodies, including the radiation impedance matrix (which combines radiation resistances and added masses). The equivalent system is applied for discussing optimum performance for maximizing the absorbed wave energy. It is shown that, for an axisymmetric system utilizing heave modes, it is possible to absorb an energy amounting to the incident wave power on a crest length which equals the wavelength divided by 2π, even though the power take-off is applied to the relative motion only. Moreover, it is shown that it is possible to obtain an equivalent excitation force which exceeds the wave excitation force on either body.

Wave Excitation Force Estimation for a Multi-DoF WEC via a Cubature Kalman Filter: Design and Preliminary Results

2021 ◽  
Author(s):  
Hoai-Nam Nguyen ◽  
Paolino Tona ◽  
Alexis Mérigaud ◽  
Mathieu Cocho ◽  
Alexandre Pichard
Keyword(s):  
Kalman Filter ◽  
Filter Design ◽  
Order System ◽  
Wave Excitation ◽  
Force Estimation ◽  
Energy Converter ◽  
Preliminary Results ◽  
Cubature Kalman Filter ◽  
Excitation Force ◽  
Wave Excitation Force

Abstract This paper presents the design and implementation of a wave excitation force estimator based on the cubature Kalman filter (CKF) for a CETO 6, a submersed wave energy converter controlled using three power take-off systems attached to the tether lines. Wave excitation force estimation is required by many advanced wav energy converter (WEC) control approaches. However, contrary to the single degree-of-freedom (1-DoF) case, the literature on the design of wave estimators is quite scarce for devices with multiple degrees-of-freedom. The advantages of CKF wave estimator described in the paper are its performance and ease of tuning when working with a high-order system, as it is the case for the 6-DoF linear model used for the design. Preliminary results for all the 6 directions are presented in nominal conditions and also in mismatch conditions, where the estimator is applied to a full nonlinear model of the system, under the action of long-crested and short-crested waves.

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