Article

Short-Term Wave Forecasting for Real-Time Control of Wave Energy Converters

Dept. of Electron. Eng., Nat. Univ. of Ireland Maynooth, Maynooth, Ireland
IEEE Transactions on Sustainable Energy (Impact Factor: 3.84). 08/2010; DOI: 10.1109/TSTE.2010.2047414
Source: IEEE Xplore

ABSTRACT Real-time control of wave energy converters requires knowledge of future incident wave elevation in order to approach optimal efficiency of wave energy extraction. We present an approach where the wave elevation is treated as a time series and it is predicted only from its past history. A comparison of a range of forecasting methodologies on real wave observations from two different locations shows how the relatively simple linear autoregressive model, which implicitly models the cyclical behavior of waves, can offer very accurate predictions of swell waves for up to two wave periods into the future.

2 Followers
 · 
135 Views
  • Source
    • "Under conditions (8) or (9), the average absorbed power is maximum and it is half the average excitation power , the other half being lost in radiation [4]. It has been shown [6], [17] that the noncausality can be addressed with simple regressive predictors of excitation force. However, there are two more characteristics of reactive control that make its practical implementation difficult (if not impossible ) in some situations: • The optimal velocity, position, and PTO force can have very large amplitudes, well beyond physical constraints, particularly in large waves and for small systems. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A novel strategy for the real-time control of oscillating wave energy converters (WECs) is proposed. The controller tunes the oscillation of the system such that it is always in phase with the wave excitation force and the amplitude of the oscillation is within given constraints. Based on a nonstationary, harmonic approximation of the wave excitation force, the controller is easily tuned in real-time for performance and constraints handling, through one single parameter of direct physical meaning. The effectiveness of the proposed solution is assessed for a heaving system in one degree of freedom, in a variety of irregular (simulated and real) wave conditions. A performance close to reactive control and to model predictive control is achieved. Additional benefits in terms of simplicity and robustness are obtained.
    IEEE Transactions on Sustainable Energy 01/2013; 4(1):21-30. DOI:10.1109/TSTE.2012.2196717 · 3.84 Impact Factor
  • Source
    • "The above control strategies do not use prediction of the forces acting on the WEC and thus inevitably lead to sub-optimal energy extraction. Since the early work [5] [9] [11] there have been a number of authors who have recognized the importance of DSWP in the control of a variety of floating body applications [7] [8] [17] [37] [38], but these have, as yet, not been incorporated into actual control schemes. The point absorber model used is shown in Fig. 1 and roughly corresponds to the Power Buoy device PB150 developed by OPT Inc, see [39]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate that deterministic sea wave prediction (DSWP) combined with constrained optimal control can dramatically improve the efficiency of sea wave energy converters (WECs), while maintaining their safe operation. We focus on a point absorber WEC employing a hydraulic/electric power take-off system. Maximizing energy take-off while minimizing the risk of damage is formulated as an optimal control problem with a disturbance input (the sea elevation) and with both state and input constraints. This optimal control problem is non-convex, which prevents us from using quadratic programming algorithms for the optimal solution. We demonstrate that the optimum can be achieved by bang–bang control. This paves the way to adopt a dynamic programming (DP) algorithm to resolve the on-line optimization problem efficiently. Simulation results show that this approach is very effective, yielding at least a two-fold increase in energy output as compared with control schemes which do not exploit DSWP. This level of improvement is possible even using relatively low precision DSWP over short time horizons. A key finding is that only about 1 second of prediction horizon is required, however, the technical difficulties involved in obtaining good estimates necessitate a DSWP system capable of prediction over tens of seconds.
    Renewable Energy 12/2012; 48:392-403. DOI:10.1016/j.renene.2012.05.003 · 3.36 Impact Factor
  • Source
    • "The above control strategies do not use prediction of the forces acting on the WEC and thus inevitably lead to sub-optimal energy extraction. Since the early work [2] [6] [8] there have been a number of authors who have recognized the importance of DSWP in the control of a variety of floating body applications [4] [5] [14] [34] [35], but these have, as yet, not been incorporated into actual control schemes. "
    Fuelling the Future: Advances in Science and Technologies for Energy Generation, Transmission and Storage, Edited by A. Mendez-Vilas, 01/2012: pages 396-400; Brown-Walker Press.
Show more

Preview

Download
2 Downloads
Available from