Estimation of wave excitation force for wave energy converters

Abdelrahman, Mustafa; Patton, Ron J.; Guo, Bingyong; Lan, Jianglin

doi:10.1109/systol.2016.7739823

Cited by 18 publications

(16 citation statements)

References 14 publications

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“…In the case study presented in this paper, it is assumed that the wave excitation torque, rather than the wave elevation itself, is predicted, assuming that the torque can be measured or estimated in real-time [19], [20]. Therefore, in the above analysis, the wave elevation SDF S η (ω) is simply replaced with the wave excitation torque SDF, obtained as S e (ω) = S η (ω)|H ηe (ω)| 2 , where H ηe (ω) is the linear wave-to-torque transfer function for the flap-type WEC, computed with the hydrodynamic software WAMIT 1 .…”

Section: Wave Excitation Forecastingmentioning

confidence: 99%

Receding-Horizon Pseudo-spectral Control of Wave Energy Converters Using Periodic Basis Functions

Auger¹,

Mérigaud²,

Ringwood³

2019

IEEE Trans. Sustain. Energy

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Power-maximising control of wave energy converters (WECs) can be implemented within a receding-horizon (RH) framework, whereby the reference force or velocity trajectory is updated in real-time by a feed-forward control (FFC) algorithm. For the computation of optimal WEC trajectories and control forces, Fourier pseudo-spectral (PS) control, using periodic basis functions, is simple and computationally attractive, for both linear and non-linear WEC dynamics. However, the finite-length wave excitation signal, as seen by the FFC, is in general nonperiodic. In this paper, it is shown that, despite the nonperiodicity of the input wave signal, a simple Fourier PS method can be successfully used as a FFC algorithm, by applying suitable windowing functions to the input signal when necessary. Furthermore, a simple wave forecasting algorithm is introduced, solely based on past values of the wave excitation, and the impact of wave forecast errors on the controller performance is investigated. Overall, with or without forecast errors, the proposed approach allows for power absorption above 99% of the optimum, for a forecasting horizon of less than 30 seconds for a linear WEC model, and less than 15 seconds for a non-linear WEC model including a quadratic viscous drag term. Index Terms-Wave energy converters, optimal control, power maximisation, receding-horizon control, Fourier pseudo-spectral methods, wave forecasting John Ringwood received the Diploma in Electrical Engineering from Dublin Institute of Technology and the PhD (in Control Systems) from Strathclyde University, Scotland in 1981 and 1985 respectively. He is currently Professor of Electronic Engineering at Maynooth University Ireland and Director of the Centre for Ocean Energy Research there. He was Head of the Electronic Engineering Department at NUI Maynooth from 2000 until 2005, developing the Department from a greenfield site. John's research interests cover time series modelling, wave energy, control of plasma processes and biomedical engineering. He is a Chartered Engineer and a Fellow of the Institution of Engineers of Ireland.

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Section: Wave Excitation Forecastingmentioning

confidence: 99%

Receding-Horizon Pseudo-spectral Control of Wave Energy Converters Using Periodic Basis Functions

Auger¹,

Mérigaud²,

Ringwood³

2019

IEEE Trans. Sustain. Energy

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“…In the work of [6] two approaches are presented: the first approach is based on a KF coupled with a random-walk model of the WEF; the second performs a receding horizon-unknown input estimation. In [7] a modified form of the well-known Fast Adaptive actuator Fault Estimation called Fast Adaptive Unknown Input Estimation (FAUIE) is applied to a non-linear PA. In [8] is studied a direct approach by measuring the pressures at discrete points on the buoy surface, in addition to the buoy heave position, to obtain the estimation of the WEF by an Extended Kalman Filter (EKF).…”

Section: Introductionmentioning

confidence: 99%

Real-Time Wave Excitation Forces Estimation: An Application on the ISWEC Device

Bonfanti

Hillis

Sirigu

et al. 2020

JMSE

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Optimal control strategies represent a widespread solution to increase the extracted energy of a Wave Energy Converter (WEC). The aim is to bring the WEC into resonance enhancing the produced power without compromising its reliability and durability. Most of the control algorithms proposed in literature require for the knowledge of the Wave Excitation Force (WEF) generated from the incoming wave field. In practice, WEFs are unknown, and an estimate must be used. This paper investigates the WEF estimation of a non-linear WEC. A model-based and a model-free approach are proposed. First, a Kalman Filter (KF) is implemented considering the WEC linear model and the WEF modelled as an unknown state to be estimated. Second, a feedforward Neural Network (NN) is applied to map the WEC dynamics to the WEF by training the network through a supervised learning algorithm. Both methods are tested for a wide range of irregular sea-states showing promising results in terms of estimation accuracy. Sensitivity and robustness analyses are performed to investigate the estimation error in presence of un-modelled phenomena, model errors and measurement noise.

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“…The design of an estimator for F ex , based on position and velocity measurements of a single WEC is not new [12]. Regarding prediction, a number of studies have focussed on the prediction of future wave elevation, rather than on the prediction of future F ex [7].…”

Section: Introductionmentioning

confidence: 99%

Estimation and Forecasting of Excitation Force for Arrays of Wave Energy Devices

Peña-Sanchez

Garcia-Abril

Paparella

et al. 2018

IEEE Trans. Sustain. Energy

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To maximise energy conversion, real-time control of a Wave Energy Converter (WEC) requires knowledge of the present and future excitation force (Fex) acting on the device, which is a non-measurable quantity. The problem of estimation and forecasting of Fex becomes more challenging when arrays of WECs are considered, due to the hydrodynamic interactions in the array. In this paper, a global Fex estimator for a complete WEC array is developed and compared to a set of independent estimators which utilise information local only to each device. A significant question is whether the array of measurements is sufficient to compensate for the greater complexity of the wave field, compared to the isolated body case. The paper shows that the global estimator is always more accurate than the independent estimator, improving up to 45% the estimation accuracy of the independent estimator. Regarding prediction, two different Fex forecasters for a WEC array are compared: a global forecaster, utilising Fex estimates from the full set of array devices, and an independent forecaster, utilising only a local Fex estimate. We demonstrate that the global forecaster achieves more accurate results, not only compared to the independent forecaster, but also compared to the isolated body case.

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Estimation of wave excitation force for wave energy converters

Cited by 18 publications

References 14 publications

Receding-Horizon Pseudo-spectral Control of Wave Energy Converters Using Periodic Basis Functions

Receding-Horizon Pseudo-spectral Control of Wave Energy Converters Using Periodic Basis Functions

Real-Time Wave Excitation Forces Estimation: An Application on the ISWEC Device

Estimation and Forecasting of Excitation Force for Arrays of Wave Energy Devices

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