Sharif Digital Repository

Nowadays, improvement in operational condition of distribution networks considering daily growth in electrical energy usage with financial limits appears as a huge challenge for network operators. Under these kind of circumstances, operators need to have efficient and inexpensive plans more than ever. Considering high share of power losses in overall pro-duced power, utilities always tried to minimize losses in Iran and other points of world. In addition, numerous equipment in distribution networks compared with the transmission level, impose high costs to reliability plans. Therefore, reliability improvement plans have been paid low attention by distribution network operators. This lower... 

This thesis presents a stochastic framework to properly involve the uncertainties associated with demand in distribution system restoration (DSR) problem. The restoration process returns the system back to normal operation after any combination of system components have been lost due to an outage. During restoration, the system operator executes a set of actions that progressively mitigate the outage. These actions aim at minimizing the impact of the outage on the final user without compromising the security and operability of the system. In this framework, dynamic programming (DP) is used to solve DSR problem for a distribution system that accommodates various technologies of DG units and... 

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... 

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... 

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... 

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... 

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... 

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... 

Residential demand response is an appropriate control tool for improving system reliability. This project intends to establish a model to activate residential demand response to improve distribution network reliability. Two centralized and decentralized models are proposed. The models aim at minimizing the damage cost imposed by load curtailments following unexpected events. In the models, it is supposed that distribution system operator (DSO) and responsive customers already signed a contract authorizing the DSO alters the operation of responsive appliances whenever system reliability is jeopardized. In centralized framework, Responsive customers deliver the technical data of their... 

In recent years, the pace of increment in electrical energy consumption is getting faster. Establishing new power-plants to keep a balance between generation and consumption not only has a high investment cost but also is a time consuming procedure. Thus, several studies have focused on the demand side management. Residential consumers possess remarkable portion of total electricity consumption. Accordingly, at first, the appropriate residential demand response program is selected based on presented experimental criteria. In the next step, since the network reliability is an important issue to the operators, the impact of implementation of the demand response program is studied on the... 

Power distribution systems have been traditionally operated as passive networks which consume electric power supplied by the transmission grid. Increasing utilization of wind energy in distribution systems, notably wind energy, is changing the way distribution sys-tems are operated. The distribution system operators (DSO) would operate the available wind power for reducing the power purchased from the wholesale market. However, high penetration of wind energy in distribution systems would require advanced operation mod-els and additional flexibility in system to offset the variability and uncertainty associated with wind energy. In addition, wind availability often does not positively... 

Nowadays, development of renewable electricity generation technologies, the advent of small efficient generators and increasing number of grid-connected consumers, have caused increasing interest in energy production next to the consumers locations. Distributed generation (DG) is often defined as small-scale generators that produce several kilowatts to tens of megawatts of electricity. One primary reason for using DG is its potential to reduce power losses in transmission and distribution networks. Several loss reduction methods such as capacitor placement, network reconfiguration and load management are used in distribution systems. Employing DG results in the highest loss reduction and... 

In recent years, there have been many efforts for distributing a big and complex duty among some agents in order to do it more simply. Large number of these methods are in area called distributed systems, where several different agents start to work together to do a difficult or complex duty which each of them cannot do it lonely. Combination of distributed systems and artificial intelligence is known as distributed artificial intelligence.
One of the theories that has received attention recently, is called Embodiment. According this theory, in cooperation of a set of agents for performing particular task, expertise might not be integrated in a centralized controller, rather it gradually... 

The major goal of the power industry is to serve the demand of electricity consumers as reliable as possible but at an affordable cost. Towards the goal, however, the industry faces substantial barriers such as aging infrastructures, growing demand, and limited budgets for reinforcements. A great portion of infrastructures which were built decades ago need to be retired. The growing demand needs system reinforcement and expansion. These, in turn, require considerable amounts of investment which is in contradiction with highly limited budget of the power industry. This critical situation forces the industry to utilize the existing system more efficiently and wisely. To this end, the concept... 

Network coding, as a promising method for data exchange in wireless communication network, is investigated by many researchers. However, the random nature of packet generation and transmission as well as the collision among transmitted packets have not been fully addressed in network codingrelated literature. In this dissertation, we analyze the network coding-based wireless network from this point of view. In order to achieve this goal, we apply mathematical tools such as probability theory and queuing theory. In the first part of this dissertation, we address the interaction between MAC and network coding. In this respect, we consider a multihop tandem wireless network, where each node is... 

One of the topics that has been given great consideration after restructuring and smart grid emergence, is loss management. This subject is specifically important in distribution systems, which have been reported to have 70% of the total loss in power systems. In this thesis, distribution loss is studied and its affecting factors are analyzed. Then loss optimization and loss cost allocation to distribution consumers are studeid. In order to acheive these two goals, it is neccessary for the distribution system to have the capabilities of a smart grid. The subjectof distribution reconfiguration is duiscussed as one of the loss reduction methods. Traditional reconfiguration problem trend... 

There is an increasing trend nowadays toward Distributed Generation (DGs). DG poses positive and negative side effects for both utility and customers. Reduction of system expansion costs, decreasing power loss and reliability enhancement are some benefits of DGs. Connecting DGs to the distribution system can lead to some troublesome issues. Anti-islanding protection is one of these issues. Islanding is the situation in which a distribution system becomes electrically isolated from the remainder of the power system, yet continues to be energized by DG connected to it. Traditionally, a distribution system doesn’t have any active power generating source in it and it doesn’t get power in case... 

This paper proposes a novel real-time pricing tariff design aiming at reducing the operation cost of distribution system. A customer base-line load (CBL) is established for each participant. It let the customer to have less exposure with RTP volatile prices.The tariff charges the consumption above the CBL an hourly varying price. It credits the consumption below the CBL another hourly varying price.The proposed tariff provides the participant with more incentive and discount prices to encourage it to consume more efficient. The optimal prices are determined and announced a day in advance but can change in the next day with a short notice.The response of customers to the tariff prices is... 

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... 

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...