A critical comparison of model-predictive and pseudospectral control for wave energy devices

Genest, Romain; Ringwood, John V.

doi:10.1007/s40722-016-0058-2

Cited by 38 publications

(35 citation statements)

References 36 publications

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“…Though results are presented for a particular WEC, the approach provides a platform for the effective control of a wide range of WEC devices. Finally, and to further highlight the value of this strategy when comparing to well-known optimal control methods that have been applied to this energy-maximising problem, such as MPC, we note that there exists a close connection between this momentbased optimal control formulation and the MPC-like methods reported in Faedo et al (2017) (subject of a future paper), which have been shown to outperform MPC in both energy capture and computation time (Genest & Ringwood, 2016).…”

Section: Resultsmentioning

confidence: 82%

“…2) is given. The modelling assumptions considered in this section are consistent across a wide variety of WEC energy-maximising model-based optimal control applications presented in the literature, such as, for example, Bacelli and Ringwood (2015), Genest and Ringwood (2016), Li and Belmont (2014), Li, Weiss, Mueller, Townley, and Belmont (2012) and Richter, Magaña, Sawodny, and Brekken (2014) (the reader is referred to Faedo et al (2017) for a comprehensive list of optimal control strategies that consider similar assumptions).…”

Section: Wec Modelmentioning

confidence: 94%

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Energy-maximising control of wave energy converters using a moment-domain representation

Faedo

Scarciotti

Astolfi

et al. 2018

Control Engineering Practice

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110

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A B S T R A C TWave Energy Converters (WECs) have to be controlled to ensure maximum energy extraction from waves while considering, at the same time, physical constraints on the motion of the real device and actuator characteristics. Since the control objective for WECs deviates significantly from the traditional reference ''tracking'' problem in classical control, the specification of an optimal control law, that optimises energy absorption under different sea-states, is non-trivial. Different approaches based on optimal control methodologies have been proposed for this energy-maximising objective, with considerable diversity on the optimisation formulation. Recently, a novel mathematical tool to compute the steady-state response of a system has been proposed: the moment-based phasor transform. This mathematical framework is inspired by the theory of model reduction by moment-matching and considers both continuous and discontinuous inputs, depicting an efficient and closed-form method to compute such a steady-state behaviour. This study approaches the design of an energy-maximising optimal controller for a single WEC device by employing the moment-based phasor transform, describing a pioneering application of this novel moment-matching mathematical scheme to an optimal control problem. Under this framework, the energy-maximising optimal control formulation is shown to be a strictly concave quadratic program, allowing the application of well-known efficient real-time algorithms. (N. Faedo). minimise the risk of damage, such an optimisation strategy must take into account the physical limitations of the whole conversion chain. Such an optimisation procedure can be achieved by designing an optimal controller that accomplishes such objectives.A considerable number of optimal control formulations and methods have been studied and developed to maximise the energy extraction process from WECs, with extensive reviews available, for example in Ringwood, Bacelli, and Fusco (2014). One particular popular wave energy control strategy is Model Predictive Control (MPC). The success of MPC on the energy-maximising control is mainly due to its ability to handle physical constraints systematically and within a finite horizon optimisation process. While MPC applied to WECs also involves a mathematical model, a typical receding horizon strategy, and can deal with system constraints, the objective function contrasts significantly with the one related to the usual set-point tracking objective. Rather, a converted energy-maximising objective, consistent with the definition https://doi.

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Section: Resultsmentioning

confidence: 82%

Section: Wec Modelmentioning

confidence: 94%

Energy-maximising control of wave energy converters using a moment-domain representation

Faedo

Scarciotti

Astolfi

et al. 2018

Control Engineering Practice

Self Cite

110

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“…From the solution projections, the optimal trajectories can be computed in the time domain and used as a reference trajectory that the WEC needs to follow. For more information about the implementation of the half-range Chebyshev Fourier basis function, the reader may refer to the following article [15].…”

Section: Pseudospectral Optimal Controlmentioning

confidence: 99%

“…For more information about the MPC implementation, the reader may refer to the following articles [12] and [15]. The cost function, representing the energy absorption over a fixed control horizon T is expressed in the discrete-time based on the state-space defined in (16).…”

Section: Mpc Comparisonsmentioning

confidence: 99%

“…the time under which the control algorithm will maximised the energy production, is fixed to 15s for MPC and 20s for the pseudospectral approach. A full convergence study, showing the relative performance of MPS and RHPSC, can be found in [15]. This convergence study was performed to derive a fair comparison between MPC and PS control where both of the algorithms were tuned to give the best trade-off between accuracy and computational time.…”

Section: Mpc Comparisonsmentioning

confidence: 99%

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Receding horizon pseudospectral optimal control for wave energy conversion

Genest

Ringwood

2016

2016 UKACC 11th International Conference on Control (CONTROL)

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Abstract-The present study introduces a real-time control algorithm for applications involving energy maximisation and subject to technological limitations. Development of Wave energy converters constitutes an actual topic of research, in their designs and fluid-interactions, and particularly on their controllability. Immersed WECs are subject to fluid-interaction forces, generating unusual solicitations specific to hydrodynamic equation, such as radiation force or excitation forces.Various control strategies were recently developed and more advance control algorithms are currently applied on WECS, such as Model Predictive Control [1], or Pseudospectral optimal control [2]. Such control strategies, capable of maximizing the energy production while insuring the respect of path constraints, are more realistic and applicable in real conditions involving technological limitation aspects. This paper presents a receding horizon type control, based on pseudospectral approach in the control problem resolution. Dealing with irregular waves on a fixed control horizon, the presented control need to work with nonperiodic functions, implying the change of the basis functions involved in the description of the state and control variables, namely the halfrange Chebyshev Fourier functions.Application of the receding horizon control is presented for a generic WEC, and compared with a standard MPC algorithm.

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A high-fidelity wave-to-wire simulation platform for wave energy converters: Coupled numerical wave tank and power take-off models

et al. 2018

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A critical comparison of model-predictive and pseudospectral control for wave energy devices

Cited by 38 publications

References 36 publications

Energy-maximising control of wave energy converters using a moment-domain representation

Energy-maximising control of wave energy converters using a moment-domain representation

Receding horizon pseudospectral optimal control for wave energy conversion

A high-fidelity wave-to-wire simulation platform for wave energy converters: Coupled numerical wave tank and power take-off models

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