Optimal control, MPC and MPC-like algorithms for wave energy systems: An overview

Faedo, Nicolás; Olaya, Sébastien; Ringwood, John V.

doi:10.1016/j.ifacsc.2017.07.001

Cited by 180 publications

(157 citation statements)

References 110 publications

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“…Moreover, in order to maximise power absorption and of the WEC control problem (see Section 3.3) is employed. In particular, this variation can cause numerical search problems, due to a potential loss of convexity of the performance function involved for this application (Faedo, Olaya, & Ringwood, 2017), compared to the normal quadratic form associated with tracking problems. In addition, the computational burden required for such a strategy can render the controller unsuitable for real-time applications (Faedo et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

“…In particular, this variation can cause numerical search problems, due to a potential loss of convexity of the performance function involved for this application (Faedo, Olaya, & Ringwood, 2017), compared to the normal quadratic form associated with tracking problems. In addition, the computational burden required for such a strategy can render the controller unsuitable for real-time applications (Faedo et al, 2017). Motivated by the appealing characteristics of MPC, several studies utilise ''MPC-like'' strategies, based on spectral and pseudospectral methods (Fahroo & Ross, 2008;Garg, Hager, & Rao, 2011), to try to overcome the (possibly) demanding computational effort of the original MPC optimal control formulation.…”

Section: Introductionmentioning

confidence: 99%

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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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108

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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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Faedo

Scarciotti

Astolfi

et al. 2018

Control Engineering Practice

Self Cite

108

View full text Add to dashboard Cite

show abstract

“…More examples of array optimizations coupled to WEC control algorithms exist (Garcia-Rosa et al, 2015;Sharp et al, 2017). Advanced control methods fall outside the scope of the current paper, and the reader is referred to review papers such as Penalba and Ringwood (2016) and Faedo et al (2017) for further details.…”

Section: Non-linear Programming Optimizationmentioning

confidence: 99%

Advances and Challenges in Wave Energy Park Optimization—A Review

et al. 2020

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A commercial wave energy system will typically consist of many interacting wave energy converters installed in a park. The performance of the park depends on many parameters such as array layout and number of devices, and may be evaluated based on different measures such as energy absorption, electricity quality, or cost of the produced electricity. As wave energy is currently at the stage where several large-scale installations are being planned, optimizing the park performance is an active research area, with many important contributions in the past few years. Here, this research is reviewed, with a focus on identifying the current state of the art, analyzing how realistic, reliable, and relevant the methods and the results are, and outlining directions for future research.

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“…A model predictive control (MPC) can be used as in [5]. Reference [6] utilized the pseudospectral method whereas references [7,8] developed a shape-based approach that needs a fewer number of approximated states compared to the pseudo-spectral method [9]. In the presence of limitations on the control actuation level, a bang-bang suboptimal control was proposed in [10].…”

Section: Introductionmentioning

confidence: 99%

Extending Complex Conjugate Control to Nonlinear Wave Energy Converters

Wilson

Robinett

Bacelli

et al. 2020

JMSE

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This paper extends the concept of Complex Conjugate Control (CCC) of linear wave energy converters (WECs) to nonlinear WECs by designing optimal limit cycles with Hamiltonian Surface Shaping and Power Flow Control (HSSPFC). It will be shown that CCC for a regular wave is equivalent to a power factor of one in electrical power networks, equivalent to mechanical resonance in a mass-spring-damper (MSD) system, and equivalent to a linear limit cycle constrained to a Hamiltonian surface defined in HSSPFC. Specifically, the optimal linear limit cycle is defined as a second-order center in the phase plane projection of the constant energy orbit across the Hamiltonian surface. This concept of CCC described by a linear limit cycle constrained to a Hamiltonian surface will be extended to nonlinear limit cycles constrained to a Hamiltonian surface for maximum energy harvesting by the nonlinear WEC. The case studies presented confirm increased energy harvesting which utilizes nonlinear geometry realization for reactive power generation.

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Optimal control, MPC and MPC-like algorithms for wave energy systems: An overview

Cited by 180 publications

References 110 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

Advances and Challenges in Wave Energy Park Optimization—A Review

Extending Complex Conjugate Control to Nonlinear Wave Energy Converters

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