Master's Thesis from the year 2013 in the subject Engineering - Power Engineering, grade: none, , course: Electrical engineering (Renewable energy), language: English, abstract: Wind electrical power systems are recently getting lot of attention, because they are cost competitive, environmental clean and safe renewable power source, as compared with fossil fuel and nuclear power generation. A special type of induction generator, called a doubly fed induction generator (DFIG), is used extensively for high-power wind applications. They are used more and more in wind turbine applications due to ease controllability, high energy efficiency and improved power quality. This thesis aims to develop a method of a field orientation scheme for control both the active and reactive powers of a DFIG driven by a wind turbine.The proposed control system consists of a wind turbine that drives a DFIG connected to the utility grid through AC-DC-AC link. The main control objective is to regulate the dc link voltage for operation at maximum available wind power.This is achieved by controlling the and axes components of voltages and currents for both rotor side and line side converters using PI controllers. The complete dynamic model of the proposed system is described in detail. Computer simulations have been carried out in order to validate the effectiveness of the proposed system during the variation of wind speed. The results prove that , better overall performances are achieved, quick recover from wind speed disturbances in addition to good tracking ability. Generally, any abnormalities associated with grid asymmetrical faults are going to affect the system performance considerably. During grid faults, unbalanced currents cause negative effects like overheating problems and mechanical stress due to high torque pulsations that can damage the rotor shaft, gearbox or blade assembly. Therefore, the dynamic model of the DFIG, driven by a wind turbine during grid faults has been analyzed and developed using the method of symmetrical components. The dynamic performance of the DFIG during unbalanced grid conditions is analyzed and described in detail using digital simulations. A novel fault ride-through (FRT) capability is proposed (i.e. the ability of the power system to remain connected to the grid during faults) with suitable control strategy in this thesis. In this scheme, the input mechanical energy of the wind turbine during grid faults is stored and utilized at the moment of fault clearance, instead of being dissipated in the resistors of the crowbar circuit as in the existing FRT schemes. [...]

Recently, wind electrical power systems are getting a lot of attention since they are cost competitive, environmentally clean, and safe renewable power source as compared with the fossil fuel and nuclear power generation. A special type of induction generator, called a doubly fed induction generator (DFIG), is used extensively for high-power wind applications. They are used more and more in wind turbine applications due to the ease of controllability, the high energy efficiency, and the improved power quality.This research aims to develop a method of a field orientation scheme for control both, the active and the reactive powers of a DFIG that are driven by a wind turbine. Also, the dynamic model of the DFIG, driven by a wind turbine during grid faults, is analyzed and developed, using the method of symmetrical components. Finally, this study proposes a novel fault ride-through (FRT) capability with a suitable control strategy (i.e. the ability of the power system to remain connected to the grid during faults).

Covers the fundamental concepts and advanced modelling techniques of Doubly Fed Induction Generators accompanied by analyses and simulation results Filled with illustrations, problems, models, analyses, case studies, selected simulation and experimental results, Advanced Control of Doubly Fed Induction Generator for Wind Power Systems provides the basic concepts for modelling and controlling of Doubly Fed Induction Generator (DFIG) wind power systems and their power converters. It explores both the challenges and concerns of DFIG under a non-ideal grid and introduces the control strategies and effective operations performance options of DFIG under a non-ideal grid. Other topics of this book include thermal analysis of DFIG wind power converters under grid faults; implications of the DFIG test bench; advanced control of DFIG under harmonic distorted grid voltage, including multiple-loop and resonant control; modeling of DFIG and GSC under unbalanced grid voltage; the LFRT of DFIG, including the recurring faults ride through of DFIG; and more. In addition, this resource: Explores the challenges and concerns of Doubly Fed Induction Generators (DFIG) under non-ideal grid Discusses basic concepts of DFIG wind power system and vector control schemes of DFIG Introduces control strategies under a non-ideal grid Includes case studies and simulation and experimental results Advanced Control of Doubly Fed Induction Generator for Wind Power Systems is an ideal book for graduate students studying renewable energy and power electronics as well as for research and development engineers working with wind power converters.

This book presents a modified model reference adaptive system (MRAS) observer for sensorless vector control of a wind driven doubly fed induction generator (DFIG). A mathematical model of the DFIG as influenced by core loss and main flux saturation is developed. The authors describe and evaluate grid synchronization enhancement of a wind driven DFIG using adaptive sliding mode control (SMC). Besides, grid synchronization of a wind driven DFIG under unbalanced grid voltage is also fully covered in this book.

Advanced Controls for Wind Driven Doubly Fed Induction Generators discusses the most advanced control algorithms used for enhancing the dynamics of a doubly fed induction generator (DFIG) operating at fixed and variable speeds, and which are used for different utilization purposes (standalone and grid connection). Extensive generator performance analysis has been introduced using various control topologies. Features: Presents modeling of wind energy conversion systems (WECS), including a wind turbine as a prime mover, a DFIG as a generation unit for electrical energy, and a three-phase induction motor as an isolated load Explores a detailed description for the presented control algorithms in order to visualize the base principle of each method Introduces a comprehensive performance analysis for the DFIG using the formulated predictive voltage control scheme and other control techniques under different operating conditions Examines the formulation of new control approaches which overcome the shortages present in previous DFIG control schemes Presents a detailed comparison between different control topologies for the DFIG to outline the most effective procedure in terms of dynamic response, structure simplicity, ripples, total harmonic distortion, and computational burdens The book is written for researchers and academics working on advanced control systems and those interested in areas such as machine drives, renewable energy systems, 'adaptive control', modeling of WECS, and optimization theory.

Doubly Fed Induction Generators: Control for Wind Energy provides a detailed source of information on the modeling and design of controllers for the doubly fed induction generator (DFIG) used in wind energy applications. Focusing on the use of nonlinear control techniques, this book: Discusses the main features and advantages of the DFIG Describes key theoretical fundamentals and the DFIG mathematical model Develops controllers using inverse optimal control, sliding modes, and neural networks Devises an improvement to add robustness in the presence of parametric variations Details the results of real-time implementations All controllers presented in the book are tested in a laboratory prototype. Comparisons between the controllers are made by analyzing statistical measures applied to the control objectives.

This book will be focused on the modeling and control of the DFIM based wind turbines. In the first part of the book, the mathematical description of different basic dynamic models of the DFIM will be carried out. It will be accompanied by a detailed steady-state analysis of the machine. After that, a more sophisticated model of the machine that considers grid disturbances, such as voltage dips and unbalances will be also studied. The second part of the book surveys the most relevant control strategies used for the DFIM when it operates at the wind energy generation application. The control techniques studied, range from standard solutions used by wind turbine manufacturers, to the last developments oriented to improve the behavior of high power wind turbines, as well as control and hardware based solutions to address different faulty scenarios of the grid. In addition, the standalone DFIM generation system will be also analyzed.