A Critical Comparison of Excitation Force Estimators for Wave-Energy Devices

Peña-Sanchez, Yerai; Windt, Christian; Davidson, Josh; Ringwood, John V.

doi:10.1109/tcst.2019.2939092

Cited by 60 publications

(66 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…3(b)), the wave-to-excitation-force process is non-causal. Approximation approaches of the non-causal wave-toexcitation-force process were investigated numerically and experimentally in [30], [31], and a critical comparison of excitation force estimations is given in [32]. Hence, this paper only gives a brief overview of the excitation force approximation.…”

Section: Excitation Force Approximationmentioning

confidence: 99%

Non-Linear Modeling of a Vibro-Impact Wave Energy Converter

Guo

Ringwood

2021

IEEE Trans. Sustain. Energy

Self Cite

View full text Add to dashboard Cite

This paper proposes a non-linear vibro-impact mechanism, integrated inside a semi-submerged cylindrical buoy to form a self-contained and self-referenced vibro-impact wave energy converter (VIWEC), for performance enhancement. A non-linear mathematical model of the VIWEC is derived, considering linear wave-buoy interaction and non-linear vibro-impact mechanics. Numerical simulations are conducted to investigate the influence of the vibro-impact mechanism on the VIWEC's dynamics and performance. Numerical results conclude that the VIWEC is characterised by a band-pass frequency response and inherently decoupled from ocean waves of low frequencies, indicating high survivability under extreme sea states. The vibroimpact mechanism can also broaden the VIWEC's power capture bandwidth and limit the VIWEC's motion within its physical constraint. On the other hand, the VIWEC's dynamics are sensitive to design parameters, and an improper design may lead to rich and complex non-linear dynamics of the VIWEC, e.g. chaos and multi-stability. The proposed non-linear model can provide a platform for design optimisation and control development of the VIWEC.

show abstract

Section: Excitation Force Approximationmentioning

confidence: 99%

Non-Linear Modeling of a Vibro-Impact Wave Energy Converter

Guo

Ringwood

2021

IEEE Trans. Sustain. Energy

Self Cite

View full text Add to dashboard Cite

show abstract

“…Recursive least squares is employed in [51] to identify the roll dynamics of a ship and has also been used for online identification of the model parameters for the WEC dynamics in an adaptive controller [58,59]. The recursive least squares algorithm in [58,59] assumes that the excitation force is known a priori, which requires the use of a robust estimation algorithm to be used in conjunction with the adaptive controller (see Pena et al [60] for a critical comparison of excitation force estimators for WECs). However, the approach used in [51], which is followed in the present study, makes the assumption that the external forcing parameters in Equation (1), u 1 and u 2 , are independent, zero-mean, Gaussian white noise processes.…”

Section: Real-time Parameter Identificationmentioning

confidence: 99%

A Real-Time Detection System for the Onset of Parametric Resonance in Wave Energy Converters

Davidson

Kalmár‐Nagy

2020

JMSE

Self Cite

View full text Add to dashboard Cite

Parametric resonance is a dynamic instability due to the internal transfer of energy between degrees of freedom. Parametric resonance is known to cause large unstable pitch and/or roll motions in floating bodies, and has been observed in wave energy converters (WECs). The occurrence of parametric resonance can be highly detrimental to the performance of a WEC, since the energy in the primary mode of motion is parasitically transferred into other modes, reducing the available energy for conversion. In addition, the large unstable oscillations produce increased loading on the WEC structure and mooring system, accelerating fatigue and damage to the system. To remedy the negative effects of parametric resonance on WECs, control systems can be designed to mitigate the onset of parametric resonance. A key element of such a control system is a real-time detection system, which can provide an early warning of the likely occurrence of parametric resonance, enabling the control system sufficient time to respond and take action to avert the impending exponential increase in oscillation amplitude. This paper presents the first application of a real-time detection system for the onset of parametric resonance in WECs. The method is based on periodically assessing the stability of a mathematical model for the WEC dynamics, whose parameters are adapted online, via a recursive least squares algorithm, based on online measurements of the WEC motion. The performance of the detection system is demonstrated through a case study, considering a generic cylinder type spar-buoy, a representative of a heaving point absorber WEC, in both monochromatic and polychromatic sea states. The detection system achieved 95% accuracy across nearly 7000 sea states, producing 0.4% false negatives and 4.6% false positives. For the monochromatic waves more than 99% of the detections occurred while the pitch amplitude was less than 1/6 of its maximum amplitude, whereas for the polychromatic waves 63% of the detections occurred while the pitch amplitude was less than 1/6 of its maximum amplitude and 91% while it was less than 1/3 of its maximum amplitude.

show abstract

“…In literature, several approaches have been proposed to address the problem of the WEF estimation with promising results. An exhaustive classification and comparison of several estimation techniques is presented in the work of [2]. Some examples are cited hereafter.…”

Section: Introductionmentioning

confidence: 99%

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

Bonfanti

Hillis

Sirigu

et al. 2020

JMSE

View full text Add to dashboard Cite

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.

show abstract

A Critical Comparison of Excitation Force Estimators for Wave-Energy Devices

Cited by 60 publications

References 32 publications

Non-Linear Modeling of a Vibro-Impact Wave Energy Converter

Non-Linear Modeling of a Vibro-Impact Wave Energy Converter

A Real-Time Detection System for the Onset of Parametric Resonance in Wave Energy Converters

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

Contact Info

Product

Resources

About