scholarly journals Experimental Validation of a Nonlinear MPC Strategy for a Wave Energy Converter Prototype

2016 ◽  
Author(s):  
Hoai-Nam Nguyen ◽  
Guillaume Sabiron ◽  
Paolino Tona ◽  
Morten Mejlhede Kramer ◽  
Enrique Vidal Sanchez
Keyword(s):  
Predictive Control ◽  
Wave Energy ◽  
Control Strategies ◽  
Wave Force ◽  
Optimization Criterion ◽  
Force Estimation ◽  
Incoming Wave ◽  
Computational Costs ◽  
Wave Energy Converters ◽  
Machine Performance

One of the major limitations to the development of advanced wave energy converters (WECs) control strategies are the associated computational costs. For instance, model predictive control (MPC) strategies have the potential to obtain almost optimal performance, provided that the imperfect power conversion in the power take-off (PTO) system is correctly taken into account in the optimization criterion and that the incoming wave force can be estimated and forecast. However, demanding computational requirements as well as the unresolved issue of wave force estimation have so far prevented real-time implementation and validation of such MPC strategies. In this paper, we present the successful experimental results obtained on a scaled-down prototype of the well-known Wavestar machine. Performance comparisons are provided for nonlinear MPC versus a reference PI controller.

scholarly journals Control Strategies Applied to Wave Energy Converters: State of the Art

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3115 ◽  
Author(s):  
Aleix Maria-Arenas ◽  
Aitor J. Garrido ◽  
Eugen Rusu ◽  
Izaskun Garrido
Keyword(s):  
Energy Conversion ◽  
Natural Frequency ◽  
Wave Energy ◽  
State Of The Art ◽  
Control Strategies ◽  
Resonance Mode ◽  
Wave Energy Conversion ◽  
Safe Operation ◽  
Incoming Wave ◽  
Wave Energy Converters

Wave energy’s path towards commercialization requires maximizing reliability, survivability, an improvement in energy harvested from the wave and efficiency of the wave to wire conversion. In this sense, control strategies directly impact the survivability and safe operation of the device, as well as the ability to harness the energy from the wave. For example, tuning the device’s natural frequency to the incoming wave allows resonance mode operation and amplifies the velocity, which has a quadratic proportionality to the extracted energy. In this article, a review of the main control strategies applied in wave energy conversion is presented along their corresponding power take-off (PTO) systems.

scholarly journals Model Predictive Control for Wave Energy Converters: A Moving Window Blocking Approach

2020 ◽  
Vol 53 (2) ◽  
pp. 12815-12821
Author(s):  
Juan Guerrero-Fernández ◽  
Oscar J. González-Villarreal ◽  
John Anthony Rossiter ◽  
Bryn Jones
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Wave Energy ◽  
Moving Window ◽  
Wave Energy Converters ◽  
Energy Converters

scholarly journals Hardware-in-the-Loop Validation of Model Predictive Control of a Discrete Fluid Power Power Take-Off System for Wave Energy Converters

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3668
Author(s):  
Anders H. Hansen ◽  
Magnus F. Asmussen ◽  
Michael M. Bech
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Wave Energy ◽  
Fluid Power ◽  
Wave Power ◽  
Reactive Control ◽  
Power Extraction ◽  
Wave Energy Converters ◽  
Extraction Algorithm ◽  
Energy Converters

Model predictive control based wave power extraction algorithms have been developed and found promising for wave energy converters. Although mostly proven by simulation studies, model predictive control based algorithms have shown to outperform classical wave power extraction algorithms such as linear damping and reactive control. Prediction models and objective functions have, however, often been simplified a lot by for example, excluding power take-off system losses. Furthermore, discrete fluid power forces systems has never been validated experimentally in published research. In this paper a model predictive control based wave power extraction algorithm is designed for a discrete fluid power power take-off system. The loss models included in the objective function are based on physical models of the losses associated with discrete force shifts and throttling. The developed wave power extraction algorithm directly includes the quantized force output and the losses models of the discrete fluid power system. The experimental validation of the wave power extraction algorithm developed in the paper shown an increase of 14.6% in yearly harvested energy when compared to a reactive control algorithm.

An Efficient Convex Formulation for Model-Predictive Control on Wave-Energy Converters

2017 ◽  
Author(s):  
Qian Zhong ◽  
Ronald W. Yeung
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Wave Energy ◽  
Optimization Problem ◽  
Reactive Power ◽  
Tuning Parameter ◽  
Primary Concern ◽  
Penalty Term ◽  
Wave Energy Converters ◽  
Energy Converters

Model-Predictive Control (MPC) has shown its strong potential in maximizing energy extraction for Wave-Energy Converters (WECs) while handling hard constraints. As MPC can solve the optimization problem on-line, it can better account for state changes and reject disturbances from the harsh sea environment. Interests have arisen in applying MPC to an array of WECs, since researchers found that multiple small-size WECs are more economically viable than a single large-size WEC. However, the computational demand is known to be a primary concern for applying MPC in real-time, which can determine the feasibility of such a controller, particularly when it comes to controlling an array of absorbers. In this paper, we construct a cost function and cast the problem into a Quadratic Programming (QP) with the machinery force being the “optimizer,” for which the convexity can be guaranteed by introducing a penalty term on the slew rate of the machinery force. The optimization problem can then be solved efficiently, and a feasible solution will be assured as the global optima. Constraints on the motion of the WEC and the machinery force will be taken into account. The current MPC will be compared to others existing in literature, including a nonlinear MPC [1] which has been applied in wave-tank tests. The effects of constraints on the control law and the absorbed power are investigated. Performances of the WEC are shown for both regular and irregular wave conditions. The current MPC is found to have good energy-capture capability and is able to broaden the band-width for capturing wave energy. The reactive power required by the PTO system is presented. The additional penalty term provides a tuning parameter, of which the effects on the MPC performance and the reactive power requirement are discussed.

scholarly journals Balancing Power Output and Structural Fatigue of Wave Energy Converters by Means of Control Strategies

Energies ◽  
2014 ◽  
Vol 7 (4) ◽  
pp. 2246-2273 ◽  
Author(s):  
Francesco Ferri ◽  
Simon Ambühl ◽  
Boris Fischer ◽  
Jens Kofoed
Keyword(s):  
Wave Energy ◽  
Power Output ◽  
Control Strategies ◽  
Structural Fatigue ◽  
Wave Energy Converters ◽  
Energy Converters

An Efficient Convex Formulation for Model-Predictive Control on Wave-Energy Converters1

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Qian Zhong ◽  
Ronald W. Yeung
Keyword(s):  
Model Predictive Control ◽  
Cost Function ◽  
Predictive Control ◽  
Wave Energy ◽  
Reactive Power ◽  
Primary Concern ◽  
Penalty Term ◽  
Irregular Wave ◽  
Wave Energy Converters ◽  
Hard Constraints

Model-predictive control (MPC) has shown its strong potential in maximizing energy extraction for wave-energy converters (WECs) while handling hard constraints. However, the computational demand is known to be a primary concern for applying MPC in real time. In this work, we develop a cost function in which a penalty term on the slew rate of the machinery force is introduced and used to ensure the convexity of the cost function. Constraints on states and the input are incorporated. Such a constrained optimization problem is cast into a Quadratic Programming (QP) form and efficiently solved by a standard QP solver. The current MPC is found to have good energy-capture capability in both regular and irregular wave conditions, and is able to broaden favorably the bandwidth for capturing wave energy compared to other controllers in the literature. Reactive power required by the power-take-off (PTO) system is presented. The effects of the additional penalty term are discussed.

The Fair Evaluation of Wave Energy Converters

2020 ◽  
Author(s):  
Jian Tan ◽  
Henk Polinder ◽  
Peter Wellens ◽  
Sape Miedema
Keyword(s):  
Wave Energy ◽  
Evaluation Method ◽  
Control Strategies ◽  
Optimization Methods ◽  
Size Optimization ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Cost Of Energy ◽  
The Cost ◽  
Energy Converters

Abstract In this paper, a fair evaluation method of WECs (Wave Energy Converters) is established based on frequency domain simulation. In this fair evaluation, size optimization and downsizing of PTO (Power Take-Off) capacity are included to minimize the Cost of Energy for the concerned wave location. Based on this fair evaluation, a techno-economic evaluation of a generic point absorber is conducted for a specific wave location, and two different control strategies of PTO are considered. The results show that this fair evaluation method can contribute to the improvement of techno-economic performance of WECs. Furthermore, a comparison among three different size optimization methods of WECs is performed.

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