Sharif Digital Repository

Recently, in many countries, power systems are moving towards creating a competitive structure for trading electrical energy. These changes, along with the numerous advantages of the Distributed Generators (DGs), have created more incentives for distribution companies to use these kinds of generators more than ever before. The Volt/Var control is one of the most important control schemes in distribution networks, which can be affected by DGs. This paper presents a new approach for the Volt/ Var control in distribution networks. The output reactive powers of the DGs, Static Var Compensators (SVCs), Load Tap Changers (LTCs) and the settings of the local controllers are chosen as the control... 

A gossip protocol is a procedure for spreading secrets among a group of agents, using a connection graph. The goal is for all agents to get to know all secrets, in which case we call the execution of the protocol successful. We consider distributed and dynamic gossip protocols. In distributed gossip, the agents themselves instead of a global scheduler determine whom to call. In dynamic gossip, not only secrets are exchanged but also telephone numbers (agent identities). This results in increased graph connectivity. We define six such distributed dynamic gossip protocols, and we characterize them in terms of the topology of the graphs on which they are successful, wherein we distinguish... 

This paper presents a reliability assessment algorithm for distribution systems using a Static Series Voltage Regulator (SSVR). Furthermore, this algorithm considers the effects of Distributed Generation (DG) units, alternative sources, system reconfiguration, load shedding and load adding on distribution system reliability indices. In this algorithm, load points are classified into 8 types and separated restoration times are considered for each class. Comparative studies are conducted to investigate the impacts of DG and alternative source unavailability on the distribution system reliability. For reliability assessment, the customer-oriented reliability indices such as SAIFI, SAIDI, CAIDI... 

This paper focuses on expansion co-planning studies of natural gas and electricity distribution systems. The aim is to develop a mixed-integer linear programming (MILP) model for such problems to guarantee the finite convergence to optimality. To this end, at first the interconnection of electricity and natural gas networks at demand nodes is modelled by the concept of energy hub (EH). Then, mathematical model of expansion studies associated with the natural gas, electricity and EHs are extracted. The optimization models of these three expansion studies incorporate investment and operation costs. Based on these separate planning problems, which are all in the form of mixed-integer nonlinear... 

This paper focuses on expansion co-planning studies of natural gas and electricity distribution systems. The aim is to develop a mixed-integer linear programming (MILP) model for such problems to guarantee the finite convergence to optimality. To this end, at first the interconnection of electricity and natural gas networks at demand nodes is modelled by the concept of energy hub (EH). Then, mathematical model of expansion studies associated with the natural gas, electricity and EHs are extracted. The optimization models of these three expansion studies incorporate investment and operation costs. Based on these separate planning problems, which are all in the form of mixed-integer nonlinear... 

This paper investigates the performance of a smart distribution system comprised of multi-microgrids during emergency conditions. It also proposes a hierarchical scheme for outage management in such a system to enhance the security of supply during contingencies. This goal is achieved through sharing the available generation and storage capacities among different microgrids. In this regard, at first, a well-organized framework is devised in order to introduce the roles and tasks of each player in operation stage of a multi-microgrids system. Based on this framework, the general optimization model that needs to be evaluated in the proposed outage management scheme is formulated. Then, various... 

Nowadays, large-scale power outages induced by ever-growing natural disasters are increasing at a galloping rate. In this regard, this paper aims at improving the resilience of power distribution systems in facing high impact low probability (HILP) events in the planning phase of the system. To this end, optimal switch placement along with the optimal distribution line hardening strategies is proposed to mitigate the repercussions of the natural calamities. So, decreasing the failure probability of the distribution lines alongside the optimal placement of remote-controlled switches (RCSs) to increase the maneuvering capability of the system, the system operator would be able to strengthen... 

Standard mathematical-programming-based models have attracted considerable attention for optimizing distribution system planning and operation due to their salient advantages. More specifically, mixed-integer linear programming (MILP) has proven very effective in modeling such problems. The availability of optimization software for efficiently solving MILP problems with guaranteed convergence to optimality while providing a measure of the distance to the optimal solution has made MILP models more popular. Although a plethora of efficient MILP formulations have been proposed for planning and operating studies of distribution grids, incorporating reliability into such models is still... 

In distribution system planning studies, reliability evaluation is performed during optimization procedure to calculate the interruption cost, DISCO's income and to check the viability of constraints related to reliability indices. In each iteration of the optimization algorithm a special plan is evaluated that is different from other plans. So the configuration and specification of the network which is one of the input information for reliability evaluation is changing continuously that makes difficulties for this evaluation. To solve these difficulties, this paper presents a systematic method for reliability evaluation in distribution planning studies. The proposed approach can be... 

This paper develops a general framework for reliability assessment of multi-microgrid (MMG) distribution systems. It also investigates reliability impacts of coordinated outage man-agement strategies in a MMG distribution network. According to the proposed reliability evaluation framework, which is based on sequential Monte Carlo simulation method, distribution system is divided into smaller sections/microgrids based on protection sys-tem configuration and operating measures are efficiently simulat-ed considering different operation modes. In order to demonstrate the role of outage management strategy in reliability performance of MMG distribution systems, at first, the required features of... 

Optimal placement of switches can play a key role in providing resilience to power distribution systems against major faults caused by natural disasters. This study presents a resilience-based framework for optimal switch placement in distribution systems being consistent with the expansion plans of distributed generation units. At first, the impact of hurricanes on distribution system components is modelled using the geographic information system of distribution grid and the strength of components against extreme weather-related events. Then, a new resiliency index is proposed to assess the resilience of distribution grids. This index is involved in a mathematical model of the switch... 

Hardening and operational measures in electrical distribution systems (EDSs) aim at improving the resilience of EDS in case of natural disasters. This paper proposes a novel two-stage framework for establishing optimal restoration paths for supplying critical loads (CLs) in the aftermath of a natural disaster that will improve the resilience of EDSs. To this end, in the first stage, an algorithm is introduced to find all possible candidate paths between available distributed energy resources (DERs) and CLs, the output of which is applied to the second stage, as the inputs. Subsequently, in the second stage, the problem of finding the optimal restoration paths is modeled as a mixed integer... 

Both frequency and intensity of natural disasters have intensified in recent years. It is, therefore, essential to design effective strategies to minimize their catastrophic consequences. Optimizing recovery tasks, including distribution system reconfiguration (DSR) and repair sequence optimization (RSO), are the key to enhance the agility of disaster recovery. This article aims to develop a resilience-oriented DSR and RSO optimization model and a mechanism to quantify the recovery agility. In doing so, a new metric is developed to quantify the recovery agility and to identify the optimal resilience enhancement strategies. The metric is defined as 'the number of recovered customers divided... 

In many popular applications like peer-to-peer systems, large amounts of data are distributed among multiple sources. Analysis of this data and identifying clusters is challenging due to processing, storage, and transmission costs. In this paper, we propose GDCluster, a general fully decentralized clustering method, which is capable of clustering dynamic and distributed data sets. Nodes continuously cooperate through decentralized gossip-based communication to maintain summarized views of the data set. We customize GDCluster for execution of the partition-based and density-based clustering methods on the summarized views, and also offer enhancements to the basic algorithm. Coping with... 

This paper investigates the operation of a smart distribution system comprised of multiple microgrids during emergency conditions. It proposes a two-stage hierarchical scheme for outage management in such a system to enhance the security of supply during contingencies. This goal is achieved through sharing the available generation and storage capacities among different microgrids. In doing so, a well-organized framework is devised in order to introduce the roles and tasks of each player in operation stage of a multi-microgrids system. Based on this framework, the general optimization model that needs to be evaluated at each stage of the proposed outage management scheme is formulated. In... 

A dynamical hybrid observer is proposed for online reconstruction of the active mode and continuous states of Pressure Swing Adsorption (PSA) processes as an integral part of a hybrid control system. A mode observer is designed for estimation of the active mode, and the continuous spatial profiles are estimated by a Distributed and Decentralized Switching Kalman Filter. The proposed hybrid observer has been applied, in silico, for a two-bed, six-step PSA process. The active mode of the process along with the continuous spatial profiles of its adsorption beds have been estimated quite accurately based on very limited number of noise corrupted temperature and pressure measurements. © 2017  

The main goal of this paper is to obtain the optimal Distributed Generation (DG) investments as well as purchase additional power from Transmission Companies (TRANSCOs). To do this, a new mathematical modeling and a new software package interfacing between the two powerful softwares MATLAB and GAMS are used. The proposed model optimizes total system planning costs and consequently costumers' bills, reduces total system losses, guaranties system voltage profiles and prevents feeders' congestion. This new model and software package have been executed in two different cases depending if system voltage profiles are in their permissible margin or not; in each case, three different scenarios are... 

This paper introduces the modeling of Static Series Voltage Regulator (SSVR) in the load flow calculations for steady-state voltage compensation and loss reduction. For this approach, an accurate model for SSVR is derived to use in load flow calculations. The rating of this device as well as direction of required reactive power injection to compensate voltage to the desired value (1p.u.) is derived, discussed analytically, and mathematically using phasor diagram method. Since performance of SSVR varies when it reaches to its maximum capacity, modeling of SSVR in its maximum rating of reactive power injection is derived. The validity of the proposed model is examined using two standard... 

A distributed dynamic vibration absorber with adaptive capability is presented to improve vibration suppression characteristics of harmonically excited structures. A double-ended cantilever beam carrying intermediate lumped masses forms the absorber subsection. The adaptive capability is achieved through concurrent adjustment of the positions of the moving masses, along the beam, to comply with the desired optimal performance. The necessary and sufficient conditions for the existence of periodic oscillatory behaviour, along with some physical bounds placed on the absorber parameters, form a constrained optimization problem for the optimum tuning strategy. Through numerical simulations it is...