PASSIVITY-BASED NUMERICAL MODELING AND GRID INTEGRATION STRATEGIES FOR WAVE ENERGY CONVERTER ARRAYS
PASSIVITY-BASED NUMERICAL MODELING AND GRID INTEGRATION STRATEGIES FOR WAVE ENERGY CONVERTER ARRAYS

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Published: 2022

Total Pages:

ISBN-13:

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Abstract : The body of work presented here develops numerical time-domain models of Wave Energy Converter (WEC) arrays or wave farms. It will be shown here that a cluster of WECs can be more effective in extracting oceanic energy, can facilitate deployment logistics, and help with grid integration. The objectives of this work are: (i) developing a theoretical metric to evaluate the energy extraction potential of a WEC array, (ii) developing an algorithm that ensures the stability of the time-domain models of WEC arrays, and (iii) identifying strategies that facilitate grid integration and power management of a WEC array. In the process of developing the theoretical performance metric, the potential theory was used to develop expressions for wave potentials as the incoming wave reflects by and transmits through the WEC array. Decomposing the wave potential in horizontal and vertical parts enabled the application of boundary conditions based on continuity in terms of velocities and potentials. Incorporation of the hydrodynamic terms showed an increase of up to 28% in the low-frequency range. The knowledge of the wave potentials in and around the WEC array helped the application of robust system identification strategies that accurately described the physical phenomenon and ensured the numerical stability of the numerical models. The dissipative nature of the system enabled the application of the passivity property for system identification. The proposed approach could guarantee the numerical stability of time-domain modeling of WEC arrays while also ensuring high accuracy of the emulated hydrodynamics and the motions of the bodies. For the case studies considered, the identified systems calculated the motion time-histories with > 95% accuracy for WEC array cases and > 99% accuracy for the single isolated body case. Finally, the dissertation addresses the grid integration and power management issues associated with the power generated by WEC arrays. The oscillatory nature of ocean waves introduces variability in the total power produced. This work develops the conditions that exploit the phase offsets in the wave received at individual WECs at any given time. The conditions developed here will result in constant power by imposing polyphase power profiles for the WECs in the array. Continuously constant power is desirable for grid integration and power management. Additionally, the objectives for an ideal power controller are developed that can make the overall produced by the WEC array constant. 95% accuracy for WEC array cases and > 99% accuracy for the single isolated body case. Finally, the dissertation addresses the grid integration and power management issues associated with the power generated by WEC arrays. The oscillatory nature of ocean waves introduces variability in the total power produced. This work develops the conditions that exploit the phase offsets in the wave received at individual WECs at any given time. The conditions developed here will result in constant power by imposing polyphase power profiles for the WECs in the array. Continuously constant power is desirable for grid integration and power management. Additionally, the objectives for an ideal power controller are developed that can make the overall produced by the WEC array constant. 99% accuracy for the single isolated body case. Finally, the dissertation addresses the grid integration and power management issues associated with the power generated by WEC arrays. The oscillatory nature of ocean waves introduces variability in the total power produced. This work develops the conditions that exploit the phase offsets in the wave received at individual WECs at any given time. The conditions developed here will result in constant power by imposing polyphase power profiles for the WECs in the array. Continuously constant power is desirable for grid integration and power management. Additionally, the objectives for an ideal power controller are developed that can make the overall produced by the WEC array constant.

Wave Energy Converter Array Optimization
Wave Energy Converter Array Optimization

Author: Christopher J. Sharp

Publisher:

Published: 2015

Total Pages: 63

ISBN-13:

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With the need to integrate renewable energy sources into the current energy portfolio and the proximity of many population centers to an ocean coastline, it is pressing that marine energy systems, specifically wave energy converters (WECs), are evaluated as potential solutions for meeting energy needs. In order to best understand power development, economics, grid integration requirements, and other aspects prior to installation, the ability to model these systems computationally is vital to their eventual deployment. However, the research area of WEC array optimization is young, and as such, results from previously implemented optimization methods are both few in number and preliminary in nature. The goal of this research is to investigate the economics of implementing WEC arrays, determine viable cost models, create an optimization framework for WEC arrays that will enable developers to - for the first time - understand the tradeoff between power development and cost for potential WEC arrays, and to explore preliminary systems-level issues, such as WEC layout and device spacing. A genetic algorithm approach that utilizes an analytic hydrodynamic model and introduces the use of an array cost model is presented. The resulting optimal layouts for two studies are then discussed. This work is integral in providing an understanding of device layout and spacing and is a foundational starting point for subsequent and more advanced WEC array optimization research.

Numerical Modeling of the Effects of Wave Energy Converter Characteristics on Nearshore Wave Conditions
Numerical Modeling of the Effects of Wave Energy Converter Characteristics on Nearshore Wave Conditions

Author:

Publisher:

Published: 2015

Total Pages: 13

ISBN-13:

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Modeled nearshore wave propagation was investigated downstream of simulated wave energy converters (WECs) to evaluate overall near- and far-field effects of WEC arrays. Model sensitivity to WEC characteristics and WEC array deployment scenarios was evaluated using a modified version of an industry standard wave model, Simulating WAves Nearshore (SWAN), which allows the incorporation of device-specific WEC characteristics to specify obstacle transmission. The sensitivity study illustrated that WEC device type and subsequently its size directly resulted in wave height variations in the lee of the WEC array. Wave heights decreased up to 30% between modeled scenarios with and without WECs for large arrays (100 devices) of relatively sizable devices (26 m in diameter) with peak power generation near to the modeled incident wave height. Other WEC types resulted in less than 15% differences in modeled wave height with and without WECs, with lesser influence for WECs less than 10 m in diameter. Wave directions and periods were largely insensitive to changes in parameters. Furthermore, additional model parameterization and analysis are required to fully explore the model sensitivity of peak wave period and mean wave direction to the varying of the parameters.

Grid Converters for Photovoltaic and Wind Power Systems
Grid Converters for Photovoltaic and Wind Power Systems

Author: Remus Teodorescu

Publisher: John Wiley & Sons

Published: 2011-07-28

Total Pages: 358

ISBN-13: 1119957206

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Grid converters are the key player in renewable energy integration. The high penetration of renewable energy systems is calling for new more stringent grid requirements. As a consequence, the grid converters should be able to exhibit advanced functions like: dynamic control of active and reactive power, operation within a wide range of voltage and frequency, voltage ride-through capability, reactive current injection during faults, grid services support. This book explains the topologies, modulation and control of grid converters for both photovoltaic and wind power applications. In addition to power electronics, this book focuses on the specific applications in photovoltaic wind power systems where grid condition is an essential factor. With a review of the most recent grid requirements for photovoltaic and wind power systems, the book discusses these other relevant issues: modern grid inverter topologies for photovoltaic and wind turbines islanding detection methods for photovoltaic systems synchronization techniques based on second order generalized integrators (SOGI) advanced synchronization techniques with robust operation under grid unbalance condition grid filter design and active damping techniques power control under grid fault conditions, considering both positive and negative sequences Grid Converters for Photovoltaic and Wind Power Systems is intended as a coursebook for graduated students with a background in electrical engineering and also for professionals in the evolving renewable energy industry. For people from academia interested in adopting the course, a set of slides is available for download from the website. www.wiley.com/go/grid_converters

Control and Nonlinear Dynamics on Energy Conversion Systems
Control and Nonlinear Dynamics on Energy Conversion Systems

Author: Herbert Ho-Ching Iu

Publisher: MDPI

Published: 2019-07-01

Total Pages: 435

ISBN-13: 3039211102

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The ever-increasing need for higher efficiency, smaller size, and lower cost make the analysis, understanding, and design of energy conversion systems extremely important, interesting, and even imperative. One of the most neglected features in the study of such systems is the effect of the inherent nonlinearities on the stability of the system. Due to these nonlinearities, these devices may exhibit undesirable and complex dynamics, which are the focus of many researchers. Even though a lot of research has taken place in this area during the last 20 years, it is still an active research topic for mainstream power engineers. This research has demonstrated that these systems can become unstable with a direct result in increased losses, extra subharmonics, and even uncontrollability/unobservability. The detailed study of these systems can help in the design of smaller, lighter, and less expensive converters that are particularly important in emerging areas of research like electric vehicles, smart grids, renewable energy sources, and others. The aim of this Special Issue is to cover control and nonlinear aspects of instabilities in different energy conversion systems: theoretical, analysis modelling, and practical solutions for such emerging applications. In this Special Issue, we present novel research works in different areas of the control and nonlinear dynamics of energy conversion systems.

Feedback Systems
Feedback Systems

Author: Karl Johan Åström

Publisher: Princeton University Press

Published: 2021-02-02

Total Pages:

ISBN-13: 069121347X

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The essential introduction to the principles and applications of feedback systems—now fully revised and expanded This textbook covers the mathematics needed to model, analyze, and design feedback systems. Now more user-friendly than ever, this revised and expanded edition of Feedback Systems is a one-volume resource for students and researchers in mathematics and engineering. It has applications across a range of disciplines that utilize feedback in physical, biological, information, and economic systems. Karl Åström and Richard Murray use techniques from physics, computer science, and operations research to introduce control-oriented modeling. They begin with state space tools for analysis and design, including stability of solutions, Lyapunov functions, reachability, state feedback observability, and estimators. The matrix exponential plays a central role in the analysis of linear control systems, allowing a concise development of many of the key concepts for this class of models. Åström and Murray then develop and explain tools in the frequency domain, including transfer functions, Nyquist analysis, PID control, frequency domain design, and robustness. Features a new chapter on design principles and tools, illustrating the types of problems that can be solved using feedback Includes a new chapter on fundamental limits and new material on the Routh-Hurwitz criterion and root locus plots Provides exercises at the end of every chapter Comes with an electronic solutions manual An ideal textbook for undergraduate and graduate students Indispensable for researchers seeking a self-contained resource on control theory

Subspace Identification for Linear Systems
Subspace Identification for Linear Systems

Author: Peter van Overschee

Publisher: Springer Science & Business Media

Published: 2012-12-06

Total Pages: 263

ISBN-13: 1461304652

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Subspace Identification for Linear Systems focuses on the theory, implementation and applications of subspace identification algorithms for linear time-invariant finite- dimensional dynamical systems. These algorithms allow for a fast, straightforward and accurate determination of linear multivariable models from measured input-output data. The theory of subspace identification algorithms is presented in detail. Several chapters are devoted to deterministic, stochastic and combined deterministic-stochastic subspace identification algorithms. For each case, the geometric properties are stated in a main 'subspace' Theorem. Relations to existing algorithms and literature are explored, as are the interconnections between different subspace algorithms. The subspace identification theory is linked to the theory of frequency weighted model reduction, which leads to new interpretations and insights. The implementation of subspace identification algorithms is discussed in terms of the robust and computationally efficient RQ and singular value decompositions, which are well-established algorithms from numerical linear algebra. The algorithms are implemented in combination with a whole set of classical identification algorithms, processing and validation tools in Xmath's ISID, a commercially available graphical user interface toolbox. The basic subspace algorithms in the book are also implemented in a set of Matlab files accompanying the book. An application of ISID to an industrial glass tube manufacturing process is presented in detail, illustrating the power and user-friendliness of the subspace identification algorithms and of their implementation in ISID. The identified model allows for an optimal control of the process, leading to a significant enhancement of the production quality. The applicability of subspace identification algorithms in industry is further illustrated with the application of the Matlab files to ten practical problems. Since all necessary data and Matlab files are included, the reader can easily step through these applications, and thus get more insight in the algorithms. Subspace Identification for Linear Systems is an important reference for all researchers in system theory, control theory, signal processing, automization, mechatronics, chemical, electrical, mechanical and aeronautical engineering.