Due to random variations of wind speed, output power of a wind turbine generator fluctuates continuously. The power and voltage quality of a wind power system consisting of Induction Generator (IG) based wind turbine (IGWT), IGWT with voltage control device and Doubly Fed Induction Generator (DFIG) based wind turbine (DFIGWT) are presented in this work. Blade pitch angle control to limit the output power at turbine’s nominal power is also presented. It is reported that the DFIG-based wind turbine system can smooth the output power and also maintain the terminal voltage at a desired level, as DFIG with two back-to-back voltage source converters that use IGBTs and a capacitor acts as the DC voltage source has real and reactive power control abilities. The comparative results show that DFIGWT-based wind farm (DFIG_WF) has the best response, IGWT-based wind farm (IGWF) with voltage control device has better and IGWF has the worst response. Results indicate that the fluctuation of output power at higher rated rotor speed (near turbine’s base wind speed) and terminal voltage are almost nil for DFIG_WF. All the analysis were carried out using SimPowerSystem tool box in MATLAB.
In this book, Enhancement of power quality by means of LVRT capability of wind farm driven by PMSG is presented. Nowadays the share of power using wind generation is increasing continuously in all over the world; hence penetration of wind power in to grid is also increasing. The grid connection condition of the wind turbine is more important and Cascading effect should be avoided; wind turbine should stay connected to grid during grid disturbances. Connecting wind farm to grid is difficult and challenging task for the system operators as there are many connection requirements as a part of Grid Codes. One of the dynamic requirements mentioned in grid code is Low voltage ride through capability. It also presents control of reactive power to satisfy grid code requirement using STATCOM. Simulation results show the real power, reactive power with STATCOM and without STATCOM.
The first part of the book discusses the online controller coordination requirements in WAN (wide-area network) which gives motivation to the new innovative schemes to predict future system status by a look-ahead approach to maintain system transient stability by introducing proper thyristor controlled series compensation (TCSC) in the post-disturbance scenario. The important feature of this scheme is in giving a general feasible approach by considering various time delays such as the communication channel delays and computation delays which are significant in geographically wide-spread power system network, WAN. The second part of the book develops the strategy for an estimation of the internal state variables, of a synchronous generator, based on available measurements. With the reducing cost of phasor measurement units (PMUs) and wide-area communication network, the research develops a new estimation strategy to investigate the actual values of internal state variables for accurate comment on power system transient stability in any operating conditions (steady state or transient) using available limited sets of measurements.
The fast growth of wind generation has led to concern about the effect of wind power on the transient stability of the electric grid. New studies must be performed in order to evaluate the behaviour of the wind farms after severe faults and improve the design of the wind farms in an efficient and economical way. Under such circumstances, the most demanding requisite for wind farm is the Fault Ride-Through (FRT) capability. Wind farms connected to high voltage transmission system must stay connected when a voltage dip occurs in the grid, otherwise, the sudden disconnection of great amount of wind power may contribute to the voltage dip, with terrible consequences. Therefore, the dynamic and transient analyses of wind generators are necessary. This book proposes some methods with suitable control strategies for wind power application that helps wind farms to be connected during grid disturbances, achieving the grid code provisions in both steady and transient conditions. The results in this book can be significant in understanding the transient stability phenomena of fixed and variable speed wind turbines and also in designing of wind farms based on transient stability requirements.
Electrical power is the most widely used source of energy for our homes, work places and industries. Population and industrial growth have led to significant increases in power consumption over the past three decades. Natural resources like coal, petroleum and gas that have driven our power plants,industries and vehicles for many decades are becoming depleted at a very fast rate. This serious issue has motivated nations across the world to think about alternative forms of energy which utilize inexhaustible natural resources. Renewable energy like solar, wind, and tidal currents of oceans is sustainable, inexhaustible and environmentally friendly clean energy. Due to all these factors, wind power generation has attracted great interest in recent years. Undoubtedly, wind power is today’s most rapidly growing renewable energy source. Many of the new, large turbines being produced are variable speed turbines,which use doubly fed induction generators (DFIG). These are induction generators which have their stator and rotor independently excited. Turbines of this type are becoming increasingly popular, because the converters required to control them are cheap and subject to less losses.
Climate change and growing concern of limited fossil fuel reserves and prices have led to the necessity of creating renewable and sustainable energy sources. Recently, Wind energy is attracting more attention from researchers and even utilities due to its benefits as a clean and abundant source of energy. Moreover, it is worth noting that Power demand has increased substantially while the expansion of power transmission lines has been severely limited due to inadequate resources and environmental restrictions. As a consequence, some transmission lines are heavily loaded and the system stability becomes a serious problem. FACTS controllers have been used for solving various power system control problems, enhancing power system stability in addition to their main function of power flow control. In this book a comprehensive and intensive study of a wind farm connected to the grid has been proposed. The aim of this book is to investigate the system stability of a wind farm connected to medium voltage grid in different operating conditions and to investigate the behavior of the system when using a Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM).
In any power system network, All parameters (Voltages, Current, Real power, Reactive power & Machines oscillation damping) stability improvement is very important. If system parameters could not be stable then some unexpected loss will occur, even machines may loss it’s synchronism. In this book, two types of FACTS devices(SVC & SSSC) has been considered for stability improvement & some external controllers(PI, PD, POD, PID, Generic controllers) has been designed to achieve the better performance of those FACTS devices. Controller parameters has been selected by using different methods i.e. Trail & Error methods ,Ziegler-Nichols close loop tuning method & Proposed Triple Integral Differential(TID) close loop tuning methods. Those FACTS devices with controllers has been applied in the power system network & After simulation it is seen that, Every parameters(V,P,Q,I,d?) becomes stable . Only small ratings of FACTS devices can regain stability in faster way then without controllers. At last, the performance of FACTS devices with TID tuning methods are highly efficient & suitable among them.
The rate of Iraqi power demand has been increased significantly faster than the infrastructure's development and it becomes very difficult to keep the system stable especially with the current acts of vandalism against the country, so it's very important to improve the power system stability. The object of this work is to improve the stability of the Iraqi National Super Grid System (INSGS) by installing Unified Power Flow Controller (UPFC) devices in different optimal locations under fault condition and comparing the results with those of without UPFC devices under the same condition. The optimal location of the UPFC device was specified based on Genetic Algorithm (GA) optimization method, it was utilized to search for optimum UPFC parameters setting and location based objective function that depends on the power and voltage as a fitness constraints. The results obtained showed that the installation of Unified Power Flow Controller (UPFC) devices at the optimal locations of the Iraqi grid gives an improvement in the stability by damping the voltage and rotor angle oscillations after subjected to the three phase fault to ground at different locations and different cases.
ABSTRACT The demand for electric energy is increasing day by day that has resulted in exploration of more and more alternate energy sources. Among the available alternate energy sources, wind energy, solar energy and fuel cells have drawn considerable attention. Further, all of these alternate energy sources are also of renewable nature. Among the mentioned alternate energy sources, wind power generation systems have been the most cost competitive alternative among all the environmentally clean and safe renewable energy sources in the world. Both fixed-speed squirrel-cage induction generator and variable speed double fed induction generator have been proposed in the literature for wind turbine generation technology. Since the direction and speed of winds may vary from location to location and time to time, the variable speed wind turbine technology offers inherent advantages over the fixed-speed one. The doubly fed induction-generator (DFIG) is used in tandem with the wind turbine to produce electric energy. The DFIG with the help of the two back to back converters: rotor side and grid side converters, is able to deal with wide variation of wind speed.
Due to the environmental and economical concerns, it is expected that a huge number of wind farms are going to be connected with the existing networks in the near future. However, the wind being intermittent sources of power, cannot meet the load demand all of the time. Wherever intermittent power sources reach high levels of grid penetration, energy storage becomes one option to provide reliable energy supplies. Therefore, this book deals with different approaches to stabilize a grid-connected wind farm.Among the various energy storage devices SMES is one of the options to provide reliable and fast response energy to the grid. These devices can help to make renewable energy more smooth and reliable, though the power output cannot be controlled by the grid operators. They can also balance micro grids to achieve a good match between generation and load demand. Also, it can significantly improve the load availability, a key requirement for any power system. The energy storage, therefore, is a desired feature to incorporate with renewable power systems, particularly in stand alone power plants. Thus this book investigates different methods to use SMES for stabilizing windfarm.
Generally there are two different methods in calculating short-circuit currents in power system networks in terms of considering arc resistance in calculations, the first method is based on considering the value of the arc resistance as a constant value (usually 0.5?) or neglecting this value. By introducing some formulae for the arc resistance like the Warrington formula which is one of the most well-known formulae, second method could be applied. Second method is based on considering the value of the arc resistance in short-circuit calculation. To calculate the short-circuit current in power system networks our model should be accurate enough, to have an accurate model in theses studies the value of the arc resistance should be considered. The problem here is the non-linear relationship between fault current and arc resistance. In this study by using ETAP software for fault analysis, Microsoft visual studio 2010 (C++) for the related iteration, short-circuit studies based on symmetrical components has been investigated on two different IEEE networks. Results show the efficiency of the arc resistance formula which has been used in this study in special range of fault currents.
Demand for electrical energy continues to grow steadily, and is particularly strong in those countries on the threshold of industrialization. Electricity grid upgrades can not keep pace with the growing energy demand due to economical and environmental considerations that electric utilities are facing today to extend their power systems. Due to this situation, operators are looking for ways to utilize the existing power systems more efficiently. Consequently, most of power systems, nowadays, are working with heavy loading conditions. These new highly stressed operating conditions of these power systems arises different forms of power system instability. This book looks at stressed modern power system together with integrated wind resources and the role of FACTS devices in enhancing voltage stability.
In this book use of TCSC and SVC to maximize Available Transfer Capability (ATC) generally defined as the maximum power transfer transaction between a specific power-seller and a power-buyer in a network during normal and contingency cases. ATC is computed using Continuous Power Flow (CPF) method considering both line thermal limit as well as bus voltage limits. Real-code Genetic Algorithm is used as the optimization tool to determine the location as well as the controlling parameter of TCSC or Simultaneously. The performance of the Real-code Genetic Algorithm has been tested on IEEE 14-Bus System and IEEE 24-Bus Reliability Test System.
In recent years the use of renewable energy including wind energy has risen dramatically. Because of the increasing development of wind power production, improvement of the control of wind turbines using classical or intelligent methods is necessary. In this book, in order to control the power of wind turbine equipped with DFIG, a novel intelligent controller based on the human mind's emotional learning is designed. The performance of proposed controller is confirmed by simulation results.
Power systems security assessment and enhancement is of utmost importance as a result of power systems expansions and operation near their security limits. In this book, the assessment of power system static and transient securities is presented. Different IEEE test systems are subjected to static and transient security classification when prone to different contingencies using novel artificial intelligence techniques based on artificial neural networks and gene expression programming. Results show the superiority of the gene expression programming based algorithm as well as the probabilistic neural network based classifier algorithm in comparison with back-propagation and radial basis function neural network based classifiers. The system static security is enhanced using thyristor controlled series capacitors (TCSC’s) installed in series with the lines. A developed approach for placement and sizing of TCSC’s is presented based on ranking method together with the simulated annealing optimization technique. The book provides extensive survey of security assessment and enhancement techniques as well as a step by step application guide to assessing and enhancing system security.