Sharif Digital Repository

Designing transactive energy (TE) markets in distribution systems has been a hot topic due to the increased presence of residential prosumers. In the literature, several residential market platforms have been proposed; however, they usually have two main drawbacks: 1) ignoring the effect of single-phase distributed energy resources on the voltage unbalance (VU) in active distribution networks to develop a transactive coordination model that will effectively mitigate the VU and 2) inability in providing a user-friendly strategy for home occupants to adjust the willingness to pay/accept of responsive assets according to their comfort and economic purposes. This article amends the shortcomings... 

Over the past decades, there has been a dramatic increase in the frequency of natural disasters, which are the leading causes of large-scale power outages. This paper, therefore, assesses the significance and role of optimal tie-line construction in improving the service restoration performance of unbalanced power distribution systems in the aftermath of high-impact low-probability incidents. In doing so, a restoration process aware stochastic mixed-integer linear programming model is developed to find the optimal locations for new tie-line construction in unbalanced three-phase distribution systems. In particular, the restoration process of distribution systems, including the fault... 

Distributed energy resources (DERs) play an important role in the future vision of distribution energy networks. This paper with the aim of promoting DERs role in energy markets proposes a new framework for the optimal bidding strategy of a Technical Virtual Power Plant (TVPP) in different markets. In the proposed framework, it is assumed that the TVPP energy power is distributed throughout a multi-carrier energy network (MCEN) which consists of district heat networks (DHNs) and a distributed electricity network (DEN). In the MCEN, CHP units are the linkage between DHNs and DEN. With the goal of maximizing the profit of TVPP in different local and wholesale energy markets, a bi-level... 

With the current focus on energy and the environment, efficient integration of renewable energies, especially solar energy into power systems, is becoming indispensable. Moreover, to fully capture solar potentials and to recognize the unique characteristics associated with solar energy in power systems reliability assessment, a profound investigation is needed. Accordingly, this paper attempts to establish a comprehensive analytical approach for modeling the reliability of a hybrid system (Photovoltaic (PV) system with Energy Storage System (ESS)). To this end, the output of the PV system is modeled by a multi-state model, and the ESS system is modeled as a two-state Markov model. Moreover,... 

Over the past decades, there has been a dramatic increase in the frequency of natural disasters, which are the leading causes of large-scale power outages. This paper, therefore, assesses the significance and role of optimal tie-line construction in improving the service restoration performance of unbalanced power distribution systems in the aftermath of high-impact low-probability incidents. In doing so, a restoration process aware stochastic mixed-integer linear programming model is developed to find the optimal locations for new tie-line construction in unbalanced three-phase distribution systems. In particular, the restoration process of distribution systems, including the fault... 

This paper proposes a novel decentralized control approach for islanded direct-current (DC) microgrids (MGs) based on model predictive control (MPC) to regulate the distributed generation unit (DGU) output voltages, i.e. the voltages of the point of common coupling (PCC). A local controller is designed for each DGU, in the presence of uncertainties, disturbances, and unmodeled dynamics. First, a discrete-time state-space model of an MG is derived. Afterward, an MPC algorithm is designed to perform the PCC voltage control. The proposed MPC scheme ensures that the PCC voltages remain within an acceptable range. Several simulation studies have been conducted to illustrate the effectiveness of... 

In this paper the reliability of distribution network is modeled in joint multistage expansion planning of distribution network assets and distributed generations (DGs). The imposed costs due to network reliability weakness are considerable in the distribution level. Therefore in the proposed model distribution network operator (DNO) considers the costs associated with load interruptions in the planning problem. In this regard, reliability evaluation of the network is modeled in the joint multistage distribution network expansion planning (MDNEP) problem in an integrated manner while the network topology is unknown until the planning problem is not solved. In the proposed joint MDNEP problem... 

The fault-tolerant capability is a prerequisite for electrical safety-critical applications. In this regard, multi-phase induction motors are well-known actuators used to provide this feature. Compared to conventional three-phase machines with distributed windings, induction machines having concentrated windings could be more fault-tolerant because of increasing the number of phases. In addition, concentrated windings have shorter end-winding and less required copper weight which makes it a lower cost solution compared to distributed windings. However, concentrated windings adversely increase the distortion of the air gap flux density which affects motor performances. In this paper, a... 

The aim of this research is to obtain the bending moment and shear live load distribution factors (LLDFs) for interior girders of simply supported slab-girder bridges subjected to continuous loading, such as military tanks. The effective parameters considered in calculating the live load distribution factor were: Girders’ number and spacing, span length, slab thickness and the longitudinal to transverse ratio of deck stiffness. Over fifty 3D finite element models were created based on the existing information of bridges in the USA. An equation was obtained for the distribution factor and its validity was assessed against the numerical results. The proposed equation was compared with the... 

We present a constant-time randomized distributed algorithms in the congested clique model that computes an O(α)-vertex-coloring, with high probability. Here, α denotes the arboricity of the graph, which is, roughly speaking, the edge-density of the densest subgraph. Congested clique is a well-studied model of synchronous message passing for distributed computing with all-to-all communication: per round each node can send one O(log n)-bit message algorithm to each other node. Our O(1)-round algorithm settles the randomized round complexity of the O(α)-coloring problem. We also explain that a similar method can provide a constant-time randomized algorithm for decomposing the graph into O(α)... 

Proliferation of distributed generations (DGs) and power-electronics-based loads is bringing about more harmonic-polluted power signals. While some failures may occur as a consequence of nonsinusoidal current or voltage waveforms, existing reliability models of protection relays have not taken the harmonic-related failures into consideration. This paper develops a comprehensive Markov reliability model to categorize the possible functional states of a component, say a transmission line, protected by a relay, operating in a harmonic-polluted environment. In order to make the proposed model practically tractable, it is further simplified in two ways, through merging the states of the same... 

A method for the reduction of interactions in linear time invariant (LTI) multivariable uncertain systems is proposed. An H∞-norm metric is proposed for the assessment of interactions in interval uncertain multiple-input multiple-output (MIMO) plants. Based on this, a procedure for the design of fixed-order dynamic decoupling precompensators for MIMO plants with interval uncertainty is outlined which can be solved using efficient solvers such as CVX. The proposed methodology is used to develop a low-order robust multivariable controller for voltage and frequency control of an islanded distributed generation (DG) unit. Copyright © 2017 by ASME  

In this paper, a 3-dimensional mathematical model for one cell of an anode-supported SOFC (solid oxide fuel cells) is presented. The model is derived from the partial differential equations representing the conservation laws of ionic and electronic charges, mass, energy, and momentum. The model is implemented to fully characterize the steady state operation of the cell with countercurrent flow pattern of fuel and air. The model is also used for the comparison of countercurrent with concurrent flow patterns in terms of thermal stress (temperature distribution) and quality of operation (current density). Results reveal that the steady-state cell performance curve and output of simulations... 

Distributed static series compensator (DSSC) is a member of the family of distributed flexible AC transmission system devices that can be attached directly to conductors of transmission lines. DSSCs are able to compensate for and adjust the line reactance; thus, they could be widely used in stability-limited transmission systems. Owing to economic matters, the optimal placement of DSSCs is of a great interest from practical viewpoints. This study presents an approach to find the optimal locations of DSSCs to enhance the system loadability and reliability using the DC load flow model. The optimisation problem is solved using the mixed-integer linear programming. A compromise between improving... 

Smart grids are envisioned to support large penetrations of electrical vehicles driven by economical and environmental signals. Nevertheless, distribution system operators are becoming concerned about distribution congestion that may occur in the network with multiple domestic plug-in hybrid electric vehicles (PHEVs) charging. Therefore, investigating the impacts of high PHEV penetration levels on the performance of distribution networks seems to be essential for system operators and planners. Doing so, in this paper, PHEV characteristics are precisely extracted from valid published reports and surveys. Accordingly, a comprehensive model for investigating the impacts of different PHEV... 

Conventional models of cardiovascular system frequently lack required detail and focus primarily on the overall relationship between pressure, flow and volume. This study proposes a localized and regional model of the cardiovascular system. It utilizes noninvasive blood flow and pressure seed data and temporal cardiac muscle regional activity to predict the operation of the heart under normal and congestive heart failure conditions. The analysis considers specific regions of the heart, namely, base, mid and apex of left ventricle. The proposed method of parameter estimation for hydraulic electric analogy model is recursive least squares algorithm. Based on simulation results and comparison... 

There are unusual nonlinear behaviors in superconducting materials, especially at low temperatures. This paper describes the procedure to reliably predict this nonlinearity in superconducting microstrip transmission lines (SMTLs). An accurate nonlinear distributed circuit model, based on simultaneously considering of both quadratic and modulus nonlinearity dependences, is proposed. All parameters of the equivalent circuit can be calculated analytically using proposed closed-form expressions. A numerical method based on Harmonic Balance approach is used to predict nonlinear phenomena like intermodulation distortions and third harmonic generations. Nonlinear analyses of the SMTLs at the... 

We substitute different types of photonic crystal waveguide components by approximate transmission line circuits. The proposed distributed circuits exploit the analogy of wave propagation in photonic crystal waveguides and transmission lines. They are either cascaded to each other or inserted like stubs to imitate wave propagation within the photonic structure. Notable examples, e.g. coupled waveguide-cavity systems, sharp 90° bends, and T-junctions, are studied in detail. It is shown that analysis of the proposed circuits here can yield accurate enough results and thus substitute the brute-force numerical methods. The privilege of having analytical models is exploited to improve the... 

In this study, a time simulation model for long-term wind capacity investment decisions in the presence of an electricity market and a tradable green certificate (TGC) market is proposed. Decisions related to the investments in the wind capacity are fundamentally based on incentives gained from both of these markets. Fundamental concepts and models of these markets are described. The TGC price trend-following and value-trading strategies for both generation and distribution companies and the regulatory policies for the limitation of TGC holding time and TGC borrowing fraction are included. In this study, a new dynamic model of coupled TGC and electricity markets is considered in order to... 

One of the distributed solutions for scaling Web Search Engines (WSEs) may be peer-to-peer (P2P) structures. P2P structures are successfully being used in many systems with lower cost than ordinary distributed solutions. However, the fact that they can also be beneficial for large-scale WSEs is still a controversial subject. In this paper, we introduce challenges in using P2P structures to design a large-scale WSE. Considering different types of P2P systems, we introduce possible P2P models for this purpose. Using some quantitative evaluation, we compare these models from different aspects to find out which one is the best in order to construct a large-scale WSE. Our studies indicate that...