Nonlinear Model Predictive Control Using Real-time Iteration Scheme for Wave Energy Converters Using WEC-Sim Platform PDF Download
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Author: Juan Luis Guerrero-Fernández
Publisher:
ISBN:
Category : Electric power production
Languages : en
Pages : 0
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Author: Juan Luis Guerrero-Fernández
Publisher:
ISBN:
Category : Electric power production
Languages : en
Pages : 0
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Author:
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Category :
Languages : en
Pages : 0
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One of several challenges that wave energy technologies face is their inability to generate electricity cost-competitively with other grid-scale energy generation sources. Several studies have identified two approaches to lower the levelised cost of electricity: reduce the cost over the device's lifetime or increase its overall electrical energy production. Several advanced control strategies have been developed to address the latter. However, only a few take into account the overall efficiency of the power take-off (PTO) system, and none of them solve the optimisation problem that arises at each sampling time on real-time. In this paper, a detailed Nonlinear model predictive control (NMPC) approach based on the real-time iteration (RTI) scheme is presented, and the controller performance is evaluated using a time-domain hydrodynamics model (WEC-Sim). The proposed control law incorporates the PTO system's efficiency in a control law to maximise the energy extracted. The study also revealed that RTI-NMPC clearly outperforms a simple resistive controller.
Author: Dominic M. Liao-McPherson
Publisher:
ISBN:
Category : Engineering mathematics
Languages : en
Pages : 131
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This dissertation concerns the theoretical, algorithmic, and practical aspects of solving optimal control problems (OCPs) in real-time. The topic is motivated by Model Predictive Control (MPC), a powerful control technique for constrained, nonlinear systems that computes control actions by solving a parameterized OCP at each sampling instant. To successfully implement MPC, these parameterized OCPs need to be solved in real-time. This is a significant challenge for systems with fast dynamics and/or limited onboard computing power and is often the largest barrier to the deployment of MPC controllers. The contributions of this dissertation are as follows.First, I present a system theoretic analysis of Time-distributed Optimization (TDO) in Model Predictive Control. When implemented using TDO, an MPC controller distributed optimization iterates over time by maintaining a running solution estimate for the optimal control problem and updating it at each sampling instant. The resulting controller can be viewed as a dynamic compensator which is placed in closed-loop with the plant. The resulting coupled plant-optimizer system is analyzed using input-to-state stability concepts and sufficient conditions for stability and constraint satisfaction are derived. When applied to time distributed sequential quadratic programming, the framework significantly extends the existing theoretical analysis for the real-time iteration scheme. Numerical simulations are presented that demonstrate the effectiveness of the scheme.Second, I present the Proximally Stabilized Fischer-Burmeister (FBstab) algorithm for convex quadratic programming. FBstab is a novel algorithm that synergistically combines the proximal point algorithm with a primal-dual semismooth Newton-type method. FBstab is numerically robust, easy to warmstart, handles degenerate primal-dual solutions, detects infeasibility/unboundedness and requires only that the Hessian matrix be positive semidefinite. The chapter outlines the algorithm, provides convergence and convergence rate proofs, and reports some numerical results from model predictive control benchmarks and from the Maros-Meszaros test set. Overall, FBstab shown to be is competitive with state of the art methods and to be especially promising for model predictive control and other parameterized problems.Finally, I present an experimental application of some of the approaches from the first two chapters: Emissions oriented supervisory model predictive control (SMPC) of a diesel engine. The control objective is to reduce engine-out cumulative NOx and total hydrocarbon (THC) emissions. This is accomplished using an MPC controller which minimizes deviation from optimal setpoints, subject to combustion quality constraints, by coordinating the fuel input and the EGR rate target provided to an inner-loop airpath controller. The SMPC controller is implemented using TDO and a variant of FBstab which allows us to achieve sub-millisecond controller execution times. We experimentally demonstrate 10-15% cumulative emissions reductions over the Worldwide Harmonized Light Vehicles Test Cycle (WLTC) drivecycle.
Author: Liang Li
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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This thesis is aimed at proposing an artificial intelligence controller to maximize the energy absorption of wave energy converter (WEC) in practical application. The controller maximizes the energy absorption by locking and releasing the WEC alternately, and such control is known as the latching control. The model predictive control strategy is used to implement real-time control. Since the control inputs are future wave forces, the controller is a non-causal system. An artificial neural network is developed and trained by the machine learning algorithm to predict the short-term wave forces.Firstly, the state-space dynamic model is developed to simulate the kinetic motion of the WEC in sea waves. Compared with traditional convolution dynamic model, the state-space representation extremely enhances the computation efficiency. Moreover, the state-space model is represented by a differential formula so that it is more convenient to implement the control algorithm. The state-space model is acquired based on the so-called system identification, which transforms the frequency-domain hydrodynamic coefficients of the WEC into a set of state vectors. A Rankine source boundary element method code is developed to calculate the hydrodynamic coefficients. By separating the entire fluid boundary into a set of elements and distributing the Rankine source across the elements uniformly, the velocity potential of the fluid is determined.
Author: Giuseppe Giorgi
Publisher: Mdpi AG
ISBN: 9783036528243
Category : Technology & Engineering
Languages : en
Pages : 266
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The book, "Optimization and Energy Maximizing Control Systems for Wave Energy Converters", presents eleven contributions on the latest scientific advancements of 2020-2021 in wave energy technology optimization and control, including holistic techno-economic optimization, inclusion of nonlinear effects, and real-time implementations of estimation and control algorithms.
Author: Sooyong Jung
Publisher:
ISBN:
Category :
Languages : en
Pages : 145
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Author: Oscar Julian Gonzalez Villarreal
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Hesam E. Shoori J.
Publisher:
ISBN:
Category : Distributed parameter systems
Languages : en
Pages : 74
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Wave energy holds great promise to be part of the alternative energy portfolio that will provide independence from fossil fuels. As wave energy converter (WEC) technologies mature, designing effective control strategies to extract maximum energy, extend device life, coordinate WEC operation within an array, or mitigate negative impacts of a WEC becomes an increasingly important area of research. However, developing tractable models for the real-time computation of WEC control signals is challenging. This thesis is concerned with developing a model reduction approach for control design that is suitable for application to high fidelity computational fluid-structure interaction. There are many approaches to model reduction; in the last two decades, much attention has been focused on the proper orthogonal decomposition and other singular value decomposition (SVD) type methods. In the control literature, the balanced truncation is an established approach to model reduction. Balanced POD is a computational approach related to the proper orthogonal decomposition in order to compute balanced truncation of a control system. The work presented in this thesis is the investigation into the applicability of a recently developed model reduction technique, Balanced POD, applied to a WEC fluid-structure interaction problem. We first model a one-dimensional fluid-structure interaction model arising in WEC dynamics heuristically, then design two control strategies for the tracking control of the WEC. Finally, we address the problem of estimating the type of information that can be available to the WEC controller and developing estimates of wave heights and forces that are suitable for control design. The work presented here paves the way for further research regarding the suitability of model reduction techniques applied to WEC problem. The simulation results clearly demonstrate that the reduced order models can successfully capture the fundamental nature of WEC dynamics and can be readily used for control design.
Author: Juan Luis Guerrero Fernández
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Matt Folley
Publisher: Academic Press
ISBN: 9780128032107
Category :
Languages : en
Pages : 304
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Numerical Modelling of Wave Energy Converters: State-of-the Art Techniques for Single WEC and Converter Arrays presents all the information and techniques required for the numerical modelling of a wave energy converter together with a comparative review of the different available techniques. The authors provide clear details on the subject and guidance on its use for WEC design, covering topics such as boundary element methods, frequency domain models, spectral domain models, time domain models, non linear potential flow models, CFD models, semi analytical models, phase resolving wave propagation models, phase averaging wave propagation models, parametric design and control optimization, mean annual energy yield, hydrodynamic loads assessment, and environmental impact assessment. Each chapter starts by defining the fundamental principles underlying the numerical modelling technique and finishes with a discussion of the technique's limitations and a summary of the main points in the chapter. The contents of the chapters are not limited to a description of the mathematics, but also include details and discussion of the current available tools, examples available in the literature, and verification, validation, and computational requirements. In this way, the key points of each modelling technique can be identified without having to get deeply involved in the mathematical representation that is at the core of each chapter. The book is separated into four parts. The first two parts deal with modelling single wave energy converters; the third part considers the modelling of arrays; and the final part looks at the application of the different modelling techniques to the four most common uses of numerical models. It is ideal for graduate engineers and scientists interested in numerical modelling of wave energy converters, and decision-makers who must review different modelling techniques and assess their suitability and output. Consolidates in one volume information and techniques for the numerical modelling of wave energy converters and converter arrays, which has, up until now, been spread around multiple academic journals and conference proceedings making it difficult to access Presents a comparative review of the different numerical modelling techniques applied to wave energy converters, discussing their limitations, current available tools, examples, and verification, validation, and computational requirements Includes practical examples and simulations available for download at the book's companion website Identifies key points of each modelling technique without getting deeply involved in the mathematical representation
