Sharif Digital Repository

Nowadays, due to the indensible role of electrical energy in life of societies, the reliability of service should be provided in an economic form. Researches has shown that, about 80% of faults occur in the distribution network. In a distribution network that is equipped with automation systems, through the acceleration in the determination of the fault location, and also possibility of reacting against transient and steady faults, the electricity interruption time duration is minimized. This thesis aims to determine the number and to locate the auto reclosers and fault indicators in a distribution network optimally. To make it economically feasible, a limited number of these devices and... 

Electric energy distribution system (DS) reliability has a great impact on the quality of service provided to customers. On the other hand, improving the reliability performance in a DS is an expensive task. So, determining an efficient and economical target for the reliability of DSs is imperative. This thesis aims to determine efficient and economical reliability targets for reliability indices of DS based on data envelopment analysis (DEA) considering distribution feeders as the decision-making units (DMUs). For this sake, using the fuzzy c-mean (FCM) method, feeders are clustered and the membership degrees are determined so that the target associated with each feeder gets greater impact... 

Verifiable secret sharing (VSS) is one of the basic problems in the theory of distributed cryptography and has important role in secure multi-party computation. In this case, it is tried to share a confidential data as secret, between multiple nodes in a distributed system, in the presence of an active adversary that can destroy a number of nodes, such that the secret can be reconstructed with the participation of certain size of honest nodes. There are two types of active adversary; Static and dynamic which the latter can change it’s corrupted nodes among the protocol. VSS protocols have different types of algorithmic complexity and one of these definitions, is the use of broadcast channel... 

Nowadays, concerns about the reduction of fossil fuels and environmental issues, have made renewable resources more important. Among these resources, photovoltaic (PV) systems are more popular than others, due to their environmental compatibility and unlimited availability of sunlight. Increasing the penetration level of PV systems in electricity networks presents various technical and control challenges such as voltage and frequency variations; and protection and harmonics issues. In this thesis, voltage rise problem due to reverse power flow in distribution feeders is discussed. This is one of the main obstacles to the expansion of these resources in distribution networks.Various solutions... 

The usage of plugin hybrid electric vehicles has environmental benefits. However, the penetration of these components raises important concerns for grid planning. Thus, it is necessary to model the load change due to their charge to investigate the impact of these vehicles on distribution networks. For this reason, it is necessary to determine the specifications of these vehicles, such as battery charge and energy consumption on daily trips. In addition, the study of some behavioral patterns of these vehicles and some experts are necessary to complete the model.In this thesis, an active distribution network is planned using dynamic programming formulation. In this model, some buses are added... 

In this work, a non-isothermal model of natural gas in pipelines including mass, momentum and energy balance equations are used as model equations for modeling and state estimation in gas pipeline systems. An algorithm is proposed to handle the discontinuities that appear in the dynamic model of a GTN. The states of GTN are estimated using the continuous/discrete form of the extended Kalman filter for two benchmarks and some heuristic rules for sensor placement in a GTN are concluded. Also, a framework for distributed and decentralized state estimation in high-pressure and long-distance gas transmission networks (GTNs) is proposed. Some heuristic rules are suggested for system decomposition... 

In this thesis, the optimal control structure selection and design of sparse multi-variable control systems is addressed. A fundamental challenge which frequently emerges in engineering, social, and economic sciences, is the optimal selection of a subset of elements, in order to maximally fulfil a design objective. In practice, it is required to solve this underlying selection problem in conjunction with a non-linear or non-convex optimization which is designed to ensure desired performance. The requirement to solve these two problems simultaneously is what makes it inherently difficult; one which has thus far eluded efforts to develop a systematic means of determining its solution. In spite... 

The growing usage of nonlinear loads has resulted in increasing voltage and current harmonic levels in distribution systems. Additionally the faults occurring in the distribution system cause voltage sag at the point of customer supply. These two power quality disturbances impose considerable costs on consumers through disrupting the correct performance of sensitive loads, causing unintended outages and decreasing the devices’ useful lifetime. Besides the aforementioned power quality issues, the electric power loss has a determining role in operational costs. In this thesis, based on feeder reconfiguration and shunt passive filters, a strategy is proposed in order to reduce the average... 

The ever-growing prevalence of gas-fired power plants has paved the way for significant changes in the electrical energy network applications in recent years. As a result, the mutual dependency between natural gas distribution systems and electrical energy distribution systems has been intensified. Thus, the integrated gas and electrical distribution system is faced with notable threats from natural disasters that can lead to disruptions in meeting the critical demands of the consumers as well as high monetary costs. The occurrence of unpredicted natural disasters such as floods, earthquakes, and hurricanes affects the performance of energy infrastructures. Given the low possibility of these... 

Implementing distribution automation system (DAS) in distribution networks needs a huge investment which usually cannot be funded entirely in a short period of time. So distribution companies (DISCOs) should develop long term plans to equip their network with automation technologies as far as economically justifiable. Similarly, DISCOs have network capacity expansion (NCX) plans which specify the scheme of construction of feeders and substations. Since considering DAS may lead to more efficient NCX plans, the planner should revise the NCX plan through the DAS planning. On the other hand, for DAS planning it is necessary to consider a NCX plan as a platform to determine the time and location... 

The process of deregulation that has involved electricity many markets has introduced several new interesting research topics in power system area. This thesis addresses one of the most fascinating issues among them: the study of distributed generation both renewable and conventional integration in distribution networks. From the distribution network operator (DNO)'s point of view, it is of interest to develop a comprehensive methodology which considers various distributed generation technologies as an option for supplying the demand in distribution networks. In this thesis, the planning problem has been multi-objectively modeled. This will help the planner in decision making while knowing... 

Occurrence of natural disasters such as flood, windstorms, tsunamis and earthquakes has caused striking effects on critical infrastructures like power systems in recent decades. There are some examples of high-impact low-possibility (HILP) events which causes catastrophic effects on power systems. Traditionally, planning and operational studies of power system have been run taking into account some reliability metrics. Although, the reliability indices can represent the ability of a system in confronting with possible failures of components, they are unable to efficiently consider the effects of severe events such as earthquake and other HILP events. Moreover, traditional power systems were... 

Electricity distribution systems are dynamically expanded in anticipation of new demands. Cost and reliability are the most important factors in finding the optimal plans for network expansion. Recently, implementation of incentive reliability regulations has accentuated the role of reliability considerations in distribution systems studies. This is because such incentive schemes create a direct link between distribution companies' revenues and their service reliability. Thus, these schemes have changed the role of reliability from a technical constraint to an economic factor. In this occasion, distribution companies require new techniques to incorporate the effects of incentive reliability... 

Restructuring in the electrical industry, is one of the most important change in this industry which cause profit based decision making in all parts of the electrical network, especially in the generation part. In a real incomplete market environment, uncertainties associated with input parameters of the GenCos’ self-scheduling problem such as market price and accessible renewable generation would be one of the most important factors that affects the profits of GenCos and energy resources. Nowadays, increased use of distributed energy resources (DERs) such as distributed generations (DGs), energy storage units, and demand response, has led to a paradigm shift within the electric power... 

Planning of distribution networks is usually accomplished using a cost-based conventional model that minimizes the total cost of construction and reinforcement of substations and feeders. The resulted expansion plan designed by this cost-based model is not necessarily the best choice for an electrical distribution company in the nowadays deregulated structure. This happening is mainly due to the fact that the utility seeks to maximize its profit in this competitive environment. On the other hand, this model does not consider the upcoming new challenges ahead of distribution systems, such as smart grid and automation. This thesis presents a novel profit-based model for multi-stage... 

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... 

Sensor Networks are set of devices which are distributed throughout an environment and are connected to each other, usually wirelessly, to collect environmental information including temperature, aire pressure, moist, pollution and physiological functions of the human body. Each device consists of a microprocessor, converter and power supply, transmitter and a receiver. In this study we intend to investigate such setup and the measured signals assuming they are sparse. A sparse signal is a discrete time signal most of indices of which are equal to zero. With this assumption at hand, we will be able to reduce the sampling rate and take advantage of sparse signal processing techniques. This... 

Current trend of energy consumption and aging infrastructure of electricity grids mandates high amounts of investment in transmission and distribution networks. On the other hand, with increased awareness about environmental issues, share of renewable energy resources in power generation portfolio has risen in recent years. Microgrids, as one of the most promising solutions to tackle these issues, are able to accommodate high penetration levels of renewable energy sources and distributed generation in distribution systems. However, microgrids sizes are limited due to some operational considerations and as a result, efficient management of distribution systems with high penetration of... 

The fundamental goal of communication networks is to transfer messages across the network between the nodes. Often, maximizing the information flow which is limited by connectivity of the network could be interesting. The concept of connectivity is divided into edge and vertex connectivity. If our focus were on the vertex-connectivity, connected dominating sets (CDS) could be a valuable tool. Obtaining (fractionally) vertex-disjoint connected dominating sets which are called fractional CDS packing presents a backbone to get an information flow matching the size of connectivity. In this thesis, we will present a distributed algorithm that is given a communication network with n nodes and... 

Optimizing multi-period modern distribution system is a challenging task due to high costs of constructions in urban areas and importance of fast and cheap goods delivery to customers. Various logistic techniques have been proposed to solve this issue. In this study, a new method is suggested to convert the strategic problem of finding depot location into a tactical problem. In addition, a vehicle routing method for multi-period distribution systems in high demand periods have been developed. For modeling this location-routing problem two objective functions have been considered as fallows minimizing the total time in the system to satisfy customer demand and operating costs. To solve this...