Azah Mohamed — новинки

A comprehensive study is made to compare the harmonic distortion produced by the different types and number of distributed generation (DG) units in a low voltage distribution system. Here, three types of DG units are considered, namely, a mini hydro power, wind turbine doubly fed induction generator and photovoltaic system. To determine the maximum allowable penetration level of inverter based DG, harmonic resonance phenomena and harmonic distortion limits are also considered. To control harmonic propagation in a distribution system with DG units, an appropriate planning of DG units is considered by determining optimal placement, sizing and voltage control of DG units. Thus, an effective heuristic optimisation technique such as improved gravitational search algorithm (IGSA) technique is also developed for determining the optimal placement, sizing and voltage control of DG units in a radial distribution system.

The generation intermittency resultant from a large photovoltaic (PV) system connected to the power network introduces many challenges and impacts in terms of power quality, stability, and reliability of the power network. There is a need to reduce or minimise the PV generation intermittency in order to integrate more PV generators and thus allows larger penetration of PV-based renewable resources to the utility network. In this book, storage technology has been used to provide solutions for the problems related to integrating the intermittent PV generation to the utility grid. The heuristic optimisation approaches of the control system in hybrid photovoltaic with battery energy storage (PV/BES) system are introduced which minimises the output power fluctuation of the PV system connected to the utility grid. While smoothing out the output of PV/BES system, the net power is dispatched to the power network on an hourly basis like a conventional generator.

Currently, many electric utilities in the world are considering approaches to offering premium power to their customers. Premium power park (PPP) has emerged as one of the approaches, designed to compensate for voltage variations and to meet customer power quality needs. To protect sensitive loads, premium grade power should be provided for such loads by using a more-reliable distribution configuration and/or a combination of state-of-the-art custom power devices (CPDs). The objectives of this book are to evaluate and identify premium power options to be offered to customers by developing various configurations of PPP and to determine optimal placement of CPDs.

Reactive power compensation has been widely used to increase the steady state transmittable power by controlling the voltage profile along the transmission lines in power systems. A number of reactive compensation devices such as shunt capacitor, static Var compensator (SVC) and static synchronous compensator (STATCOM) have long been applied by electric power utilities for this purpose. However, the benefits of reactive power compensation depend greatly on the placement and size of the compensators. In this book, heuristic optimization techniques are employed to determine the optimal location and size of Var compensators such as shunt capacitor, SVC and STATCOM in transmission networks to enhance voltage stability and improve voltage profile by minimizing power loss and total cost. A comparative study has also been done to evaluate the effectiveness of the different Var compensators.

This book consists of five chapters, which is the current chapter, briefly introduces the background, problem statement and objectives of book subject. Chapter II describes concepts of power quality monitoring and PQM placement methods are discussed and reviewed. Chapter III presents a new algorithm for optimal PQM placement based on genetic algorithm (GA) and the Mallow’s Cp that, it is named as the GACp method. In the GACp method, the concepts of the multivariable regression (MVR) theory, the Mallow’s Cp, GA, observability and redundancy are applied to determine the appropriate locations for installing the PQMs. Chapter IV presents the results of PQM placement for the IEEE 9, 30 and 69 Bus test systems. In chapter V, the major achievements of the book are summarized.

This book consists of five chapters, which are organized as, chapter I, which briefly introduces the background and objectives of this book. Chapter II describes concepts of voltage sag, voltage sag location method are discussed and reviewed. Chapter III presents a new method for identifying the exact voltage sag source locations in power systems by using the multivariable regression (MVR) model. In this method, are considered the training data for each system bus, estimate all the unmonitored bus voltages, calculated the VD and SD indices for locating the exact voltage sag. Chapter IV presents the results of voltage sag source exact location identification for the IEEE 9 Bus, 30 Bus and modified 69 Bus test systems. In chapter V, the major achievements of the book are summarized.

This book presents optimal design and best placement of power system stabilizers in multi-machine power system. Power system oscillation damping remains as one of the major concerns for secure and reliable operation of large power systems. When power systems are operating under stringent conditions, the inception of poorly damped low-frequency inter-area oscillations may lead to system-wide breakups or considerably reduce the power transfers over critical corridors. To provide fast damping for the system and thus, to improve dynamic performance, a supplementary control signal in the excitation system and/or the governor system of a generating unit can be used. Request of power system stabilizers have become the first measure to increase the system damping. The design problem of power system stabilizers can be formulated as an optimization problem and an effective optimization technique could provide a reliable solution for the problem. In addition, this book proposes an effective optimization algorithm based on particle swarm optimization with the purpose to enhance the feasibility, solution quality and convergence speed of the original algorithm for the solution.

Shunt capacitors are widely used in ?distribution systems to reduce power losses, improve voltage profile and increase system capacity. The benefits of compensation depend greatly on the placement and size of the added capacitors. In this book, the heuristic optimization techniques are used together with the backward/forward sweep ?power flow method and radial harmonic power flow for determining the optimal placement and sizing of capacitors in radial distribution networks for minimizing the power loss and total cost by considering mutual coupling, load unbalancing and harmonics. To implement the developed algorithms, the backward/forward sweep ?power flow and radial harmonic power flow methods in an open source environment, a Matlab based software tool named as Optimal Placement of Shunt Var Compensators has been developed.

This book presents coordinated design of PSS and FACTS damping controllers in multi-machine power system. When power systems are operating under stringent conditions, the inception of poorly damped low-frequency inter-area oscillations may lead to system-wide breakups or considerably reduce the power transfers over critical corridors. Request of PSSs have become the first measure to increase the system damping. However, during some operating conditions, PSS may not produce enough damping, particularly to inter-area modes. Recently, FACTS technology is emerging as an interesting approach to help in alleviating several power system operating difficulties. FACTS devices and PSS are all fast acting power system devices, and they have the potential to interact with each other and deteriorate the performance of overall system, if they are not coordinated properly. The coordinated design problem of PSS and FACTS controllers can be formulated as an optimization problem and an effective optimization technique could provide a reliable solution for the problem. In addition, this book proposes an effective optimization algorithm based on particle swarm optimization for the solution.

Due to the growing demand for electrical energy and environmental impact such as global warming and pollution, photovoltaic (PV) energy generation system has been considered as a technological option for generating clean energy. The advantage of PV system is that it is pollution free, but it still has relatively low conversion efficiency from solar irradiation to electric power. Power delivered by the PV system depends on several environmental factors such as lighting conditions, temperature and shading. The nonlinear characteristic of PV array, the fluctuating output power which varies with temperature and irradiation and losses in power conditioner devices are among the drawbacks of PV systems. An important consideration in increasing the efficiency of PV systems is to operate the system approximate to the maximum power point (MPP). This book discussed a new high performance maximum power point tracking (MPPT) controller by using a new boost converter and a new intelligent MPPT algorithm.

In this book, adaptive protection schemes for power systems with DG units are proposed by integrating fault diagnosis with protection relay coordination strategies. An automated fault diagnosis method is developed using three staged radial basis function neural network (RBFNN) in which the first RBFNN determines the fault distance from each source, the second RBFNN identifies the exact faulty line and the third RBFNN determines the circuit breakers that must be open or close for isolating the faulty zone. After identifying the exact faulty line, then protection relay coordination is implemented. A new protection coordination strategy using the backtracking algorithm is proposed in which it considers the main protection algorithm to coordinate the open/close states of relays so as to isolate the faulty line. Then a backup protection algorithm is considered to complete the protection coordination scheme for isolating the malfunction relays of the main protection system. The fault diagnosis based on RBFNN and protection coordination using the backtracking algorithm were developed in MATLAB and the fault simulations on the test systems were carried out using the DIgSILENT software.

In this book, harmonic source localization methods have been developed by considering two methods. The first method considers a single point measurement strategy for locating dominant harmonic source by determining the harmonic contributions of utility and customer at a single point called as the point of common coupling. This approach is based on a Norton equivalent circuit for simplifying the system under study, and modelling the customer load with parallel RLC components using the measured harmonic voltage and current at the PCC. While, the second method considers a multiple point measurement strategy for locating multiple harmonic sources in a distribution system using independent component analysis (ICA) and mutual information theory (MI). In this method, ICA is used for reconstructing the magnitude of the injected harmonic currents caused by harmonic sources while MI is applied for determining the exact locations of harmonic sources based on the reconstructed harmonic currents.

Protective relay maloperation due to overload and power swing is believed to be one of the contributing factors in major blackouts in the world. Most of the problems are associated with relays tripping too many healthy lines which are due to inadequate real time diagnostic support for verifying the correctness of relay operation. Therefore, there is a need for real-time monitoring tools equipped with new adaptive distance protection algorithms to help prevent relay maloperation during voltage collapse and power swings. This book discussed about the new techniques for preventing undesirable distance relay maloperation during voltage collapse and power swings in transmission grids.

In recent years, sensitive industrial and critical commercial loads have been increasing amount of focus on power quality due to various types of power quality (PQ) problems. To overcome such problems, utility companies have made efforts to improve the quality and reliability of their electric power to the consumers. Traditionally for problems originated on the utility side, the approach has been to work on the customer side to desensitize critical loads while cleaning up the circuit on the utility side. However, with the development of high power semiconductor devices, it has become possible to design various custom power devices which can provide credible solutions to power quality problems on the distribution networks. This book explained the modelling and simulations of custom power devices, namely, the distribution static compensator (D-STATCOM), dynamic voltage restorer (DVR), solid-state transfer switch (SSTS) and solid-state fault current limiter (SSFCL). New control schemes have been implemented to evaluate the performance of these custom power devices in mitigating PQ problems. The developed simulation models will be useful for further PQ studies in a distribution system.

This book proposes an efficient stand alone PV system by considering two approaches. The first approach is by developing an efficient maximum power point tracking (MPPT) controller of the PV system while the second approach is by developing an accurate model of an active sun tracker. To achieve an efficient MPPT controller, a new boost converter design and an improved MPPT algorithm are incorporated. In the proposed boost converter design, a passive regenerative snubber circuit is included to absorb the energy of stray inductance so as to reduce the IGBT switching losses. As for the improved MPPT algorithm, it is based on the curve fitting method which attempts to predict the power-voltage characteristic curve by a polynomial function of the fourth order. In the second approach for the development of an efficient PV system, a new open loop tracking algorithm is introduced to calculate the optimum tilt angle at which the installed collector should be slanted to collect the maximum solar radiation