Sharif Digital Repository

The purpose of this thesis is the presentation of an outage management scheme in a multi-microgrids system with a decentralized structure. The proposed method is designed in a two-step method to prevent damage to all microgrids and network components due to blackouts. In the first stage of this scheme, each microgrid alone provides its required power or curtails load due to the power deficiency. In the second stage, microgrids exchange power in a transactive energy environment, which is one of the new changes in active distribution systems with participation in market and price bidding, and all players of this market earn profit from their exchanges. In this case, the curtailed load will be... 

In recent years, the penetration of renewable energy sources (RESs) in the distribution networks has faced their operation with new problems. Therefore, many studies have been conducted in this field to effectively operate distribution networks by introducing multi-microgrid (MG) structures, decentralized management methods, and the concept of transactive energy. In this regard, in this thesis, a decentralized structure based on the transactive energy is presented for optimal management of the distribution network using the alternating direction method of multipliers (ADMM) with taking the technical limitations into account. As a result, MGs will be able to exchange energy directly with... 

In majority of the (standalone or grid-connected) PV Systems, predefined rule-based algorithms are utilized in order to manage and control the flow of power. The function of these algorithms is to send the generated energy from solar panels either to load for consumption, or to battery for storage, or to the grid for sale. Their performance is based on predefined instructions and regardless of load change and consumption patterns. Therefore the total efficiency of these systems depend greately upon individual user’s load type and consumption pattern. In current research, an optimum and dynamic energy management algorithm is proposed using dynamic programming (DP) method, in order to increase... 

The necessity of electrical energy, high cost of big power plants and high voltage transmission lines and also progressing of restructuring science has lead to the increasing of tendency to use the distributed generation in electrical industry. Among of different types of distributed generations, fuel cell power plants because of many advantages such as high efficiency, low emission, modular structure and ect., have a high potential to be used in power systems. The fuel cells produce electrical energy by chemical reactions. Due to the necessity of having the knowledge related to the chemical reaction which are effective on fuel cell, to study the fuel cell performance, this type of... 

With the increasing penetration of renewable energies as distributed generation (DG) in power systems, technical problems arise in both distribution and transmission system level. Voltage rise is the main barrier for connection of DGs in rural areas, while excessive reactive power demand from transmission system is the major concern for Transmission System Operators (TSO). Here, a centralized control scheme based on the Smart Grid is proposed to reduce the impact on the transmission system voltages and improve its stability, while mitigating the voltage rise issue in the distribution network. Reactive power output of DGs, substation capacitors and tap setting of transmission transformer are... 

Based on codification and implementation of regulations of supporting from development of distributed generation sources, it is expected that in future years, investment in distributed generation scheme will be welcomed by private investors impressively. Under this circumstances, distribution Company will be faced with new chances for improving quality level of their services and optimal management of penalty-reward schemes. Penalty-reward schemes is set by legislator for distribution Company in order to improve their network. One of the pioneer ways is using distributed generators. So first, distribution Companies have to find optimum places for using these generators and in the second step... 

The integration of renewable energy sources introduces several issues including islanding operation. Therefore, Islanding phenomenon should be detected by a fast and reliable islanding detection method. In this thesis an intelligent-based approach is proposed to detect islanding state for Photovoltaic (PV) and Doubly Fed Induction Generator (DFIG) units. Decision tree classification algorithm is chosen as weak classifier and by Adaptive Boosting (AdaBoost), detection accuracy is improved. 16 features are employed to construct feature vectors. Because of intermittency of renewable electricity generation, different states for PV and DFIG generation are assumed. Probable events are simulated... 

Because of advantages of using new sources of energy in the country, especially for generating green energy, the use of wind energy for power generating in wind Fields is of great interest of current communities. For developing a wind power plant the first step is to locate and confirm the areas which possess enough potential for installing the wind turbines. For this purpose in the first chapter of this thesis an introduction to the basic principles of wind energy is noted then in the next chapter the physical relations to calculate the estimated reachable energy in the area is mentioned and in the third chapter the empirical methods for selection of the suitable sites are exhibited .in the... 

Research for renewable energy has grown considerably over the last years. Osmotic energy is a form of renewable energy which is not yet used at commercial scale, but have a large potential to used at commercial scale soon. Osmotic power is a technique that converts the difference of molar free energy between fresh water and salt water into electricity. Pressure retarded osmosis (PRO) is the most frequently studied process of osmotic energy. In PRO two solutions of different salinities are brought into contact by a semipermeable membrane that only allows the transport of water and retain the solute. Positive developments in recent years initiated new studies to the exploitation of osmotic... 

One of the challenges which increasing penetration of renewable energy sources with variable generation brings is the need for more flexibility in the power system. A promising way to overcome the challenge is to have local sources of the flexibility in distribution level. To this end, we present a new model for multi-stage distribution system expansion planning which jointly considers expanding the network assets and increasing the flexibility at local level by installing conventional dispatchable distributed generator units and energy storage systems. Demand response is also considered as another source of the flexibility which can be utilized by the system operator. Since deviating from... 

In recent decades, attention to renewable energy sources has been increased, and these resources will be an integral part of power systems in the future. Meeting the equilibrium point between power consumption and power generation at the power grid is of paramount importance. However, the equilibrium point is not solely dependent on the decisions of consumers and generation units and is influenced by other parameters as well. In this regard, penetration of renewable energies into the power system can affect this equilibrium point. These sources have random behavior, which will determine the future structure of the electricity grid. These sources can also change the shape of the network net... 

With the increase of renewable energy generation in power systems, the flexibility of power systems has been challenged and the high potential of resources in active distribution systems for providing flexibility has been noticed by system operators and planners to help system flexibility. In this regard, these resources can participate in the Flexible Ramp Product market which is a new product that is defined for this purpose. In this work, the management of these resources has been modeled in an active distribution system for participating in this market by considering the network constraints, the uncertainty of renewable generation and forecasted prices of products in DA and RT markets,... 

It is possible to unload a transmission line for a while. In line restoration voltage and current of the line will have some dynamic changes. So the apparent impedance of distance relay will have dynamic changes. These changes may cause some bad results including entrance of apparent impedance to the operational zones of distance relay and even relay tripping. Consequently if relay trips, the line restoration process will stop and may not be possible.
So we want an algorithm to distinguish line restoration from short circuit condition and block the relay. This algorithm must be able to stop blocking if there is any fault in the operational zones of the relay.
In this thesis an... 

The leads with heavy current passing through the covering plates, and the winding in a transformer, are sources of eddy current losses. Due to this loss some regions of tank wall are subject to serious local overheating. It affects the safety and reliability of this expensive bject and power delivery.Heavy current in large power transformers and special type transformers give rise to a concentrated passage of eddy currents which in turn cause high local losses and overheating in the metallic parts especially in the steel tank walls of transformer.This local overheating is dangerous for transformer oil and the solid insulations. Therefore the calculation of losses and proper design of... 

Because of advantages of using new sources of energy in the country, especially for generating green energy, the use of wind energy for power generating in wind Fields is of great interest of current communities. For developing a wind power plant the first step is to locate and confirm the areas which possess enough potential for installing the wind turbines. For this purpose in the first and second chapters of this thesis an introduction to the basic principles of wind energy is noted then in the third chaptermethods of grid connection, conversion systems and turnover problems in windfarm is evaluated.in the fourth chapter with the use of Windographer software and empirical data of standard... 

In recent years, climate change due to greenhouse gases caused an increase in frequency and intensity of the natural disasters such as hurricanes, blizzards and floods. Moreover, it is anticipated that such events will increase in the future. As a result, power system decision makers are looking for methods to improve power system resiliency against such natural disasters with low occurrence probability and high impact. In this report, the distribution system resiliency has improved via placing remote control sectionalizing switches and micro grids formation during natural disasters. In this regard, the concept of resiliency and its characteristics along with the effect of remote control... 

Proliferation of distributed energy resources and the developing of smart grid concepts are of a great importance. This, however, influences the future of power systems and necessitates more studies in order to cope with the changes. In this regard, uncontrollability issues are arised by introducing the renewable energy resources in the power systems. To address this issue, energy storage systems are used to mitigate negative consequences of using renewable energy resources. Accordingly, in this thesis, a new framework for determining the capacity and location of the energy storage systems is proposed. In addition, reconfiguration of distribution network is also concerned in order to... 

Issues related to the environmental pollution, greenhouse gas emissions, as well as the limited supply of fossil fuels and their rising prices have led to the deployment of distributed energy technologies in power systems. With the increasing penetration of distributed energy sources in distribution systems, smart grids, and in particular, microgrids have emerged as a suitable and widely accepted solution for controlling and utilizing these resources. Microgrids can enhance energy efficiency in a sustainable power grid as well as the reliability of the distribution system, through supporting high penetration of renewable energy sources and providing island performance.In view of growing... 

In the recent years, there is a worldwide wave of considerable changes in power industries, including the operation of distribution networks. Deregulation, open market, alternative and local energy sources, new energy conversion technologies and other future development of electrical power systems must pursue different goals. Also growth in the demand and change in load patterns may create major bottlenecks in the delivery of electric energy. This would cause distribution system stress.Furthermore, in competitive electricity markets, operators determine the electricity price for specific intervals during a day, taking into account various economical and operational factors. Traditionally, a... 

Power generation stations, which are commonly called power plants, are treated as the core module of power systems and are in charge of producing power to be transmitted and distributed to the end consumers. As the beating heart of power industry, power plants need to be available and reliable all the time and so do their constituent components since the need for reliable electricity, nowadays, is ever increasingly highlighted. The reason lies in the rapid jump of population growth in one hand and the incredible amount of damages as a consequence to the power interruptions due to the power plant component outages, if happened, on the other one. So, power plants have to be kept within a...