Reza Eslami

Installing distributed generation units and capacitors simultaneously in a distribution system considering economic issues

Daily increasing demand of electrical energy and also recent developments in technology of distributed generations (DGs) have created special interest in using these units. On the other hand, capacitor insertion in the distribution feeders has been implemented by distribution companies for several years to reduce power loss and improve the voltage profile. Hence, according to the joint role of distributed generation units and capacitors, their optimal allocation will be influenced by each other. Therefore, in order to achieve the maximum benefits, this paper has discussed the optimal siting and sizing of DG resources and capacitors. One of the characteristics of the proposed method is that all technical and economical factors associated with installation of DGs and capacitors will be priced. For this purpose, all effective factors in optimal allocation and sizing of DG resources and capacitors are extracted and priced. For example, for the first time, the factor of voltage profile has been priced by the n...

Thermal Stresses in Plates

In this chapter the thermal stresses and the deflection in thin rectangular plates subjected to the temperature change in the thickness direction only are recalled. The basic equations are developed with the Kirchhoff-Love hypothesis. Next, the basic equations for the thermal bending of circular plates with various boundary conditions are summarized. A number of problems for rectangular and circular plates are presented

A Decision-Tree Scheme for Responding to Uncertainties in Microgrid Protection Coordination

Abstract In addition to the dynamic nature of microgrids, uncertainty in the proper operation of protection system and communication links are other challenges affecting the protection coordination of these networks. Therefore, in this paper, a new protection coordination plan based on decision tree for considering uncertainties in the topology of microgrid, protection system, and communication links is presented. The proposed method allows the adaptive protection to make global decisions and adopt the best strategy to clear faults depending on considered uncertainties. Since circuit breakers are the most prone to failure equipment in the protection system due to fault-caused stress, this paper models uncertainty in the protection system with uncertainty in the performance of circuit breakers. In order to consider uncertainty in circuit breakers and communication links, their probability of correct operation are not considered fixed but variable, respectively, proportional to the fault current flowing through the circuit breakers and the latency of communication links. The proposed plan was tested on a sample microgrid in DIgSILENT Power Factory. Results prove that using the proposed method, adaptive protection can establish an optimal sequence of strategies so that with the failure of each strategy, the best backup strategy is replaced given the uncertainties.

A Novel Method for Fault Detection in Future Renewable Electric Energy Delivery and Management Microgrids, Considering Uncertainties in Network Topology

Abstract The use of solid state transformers (SSTs) in microgrids has created a new kind of network called Future Renewable Electric Energy Delivery and Management (FREEDM) microgrid. The FREEDM microgrid provides an appropriate means for enhanced energy management, loss reduction, and network flexibility by reducing the number of converters used for a variety of AC-DC links. In this work, we propose a novel method for fault detection in FREEDM microgrids when considering uncertainties in network topology. The proposed method makes use of the Clarke and S-transforms to characterize the transients in three-phase current and voltage waveforms in the event of a fault. The extracted features of the waveforms will be used to form appropriate indices for detection, location, and characterization of the fault. The main feature of the proposed method is its capability to operate in a dynamic microgrid with varying topology. The performance of the proposed method is investigated by applying it to a sample FREEDM microgrid with ring and radial structures. It is shown that the proposed method is well capable of fault detection and diagnosis while being able to differentiate between short-circuit faults and switching transients due to variations in the network topology.

Variational Formulation of Elastostatics

In this chapter the variational characterizations of a solution to a boundary value problem of elastostatics are recalled. They include the principle of minimum potential energy, the principle of minimum complementary energy, the Hu-Washizu principle, and the compatibility related principle for a traction problem. The variational principles are then used to solve typical problems of elastostatics.

Thermally Induced Instability

In this chapter the thermoelastic buckling of beam-columns subjected to both in-plane and lateral loads is recalled for a built-in edge, a simply supported edge and a free edge. Furthermore, the thermoelastic buckling of rectangular and circular plates is also recalled. The problems and solutions for the buckling behavior of beam-columns with various boundary conditions are given. The stress-displacement relations, the relations between the resultant forces and the stress function are treated in illustrative problems.

Thermal Stresses in Bars

In this chapter the concept of thermal stresses in bars is introduced for the simple case of a perfectly clamped bar subjected to arbitrary temperature change. The problems and solutions related to thermal stresses in bars are: a perfectly clamped bar, a clamped bar with a small gap, a clamped circular frustum, a bar with variable cross-sectional area, two bars attached to each other, three bars fastened to each other, truss of three bars, and three bars hanging from a rigid plate.

Complete Solutions of Elasticity

In this chapter general solutions of the homogeneous isotropic elastostatics and elastodynamics are discussed. The general solutions are related to both the displacement and stress governing equations, and emphasis is made on completeness of the solutions [See also Chap. 16.]

Formulation of Problems of Elasticity

In this chapter both the basic boundary value problems of elastostatics and initial-boundary value problems of elastodynamics are recalled; in particular, the mixed boundary value problems of isothermal and nonisothermal elastostatics, as well as the pure displacement and the pure stress problems of classical elastodynamics are discussed. The Betti reciprocal theorem of elastostatics and Graffi’s reciprocal theorem of elastodynamics together with the uniqueness theorems are also presented. An emphasis is made on a pure stress initial-boundary value problem of incompatible elastodynamics in which a body possesses initially distributed defects.

One-Dimensional Solutions of Elastodynamics

In this chapter a number of typical one-dimensional initial-boundary value problems of homogeneous isotropic isothermal and nonisothermal elastodynamics are solved in a closed-form using the Laplace transform technique. The isothermal solutions include: (a) one-dimensional displacement waves in a semispace subject to a uniform dynamic boundary pressure, (b) one-dimensional displacement waves in a semispace subject to the initial disturbances, and (c) one-dimensional stress waves in an infinite space composed of two homogeneous isotropic elastic semispaces of different material properties. The nonisothermal solutions include: (i) one-dimensional dynamic thermal stresses produced by a plane source of heat that varies harmonically with time in an infinite elastic solid, (ii) one-dimensional dynamic thermal stresses produced by a plane nucleus of thermoelastic strain in an infinite elastic solid, and (iii) one-dimensional dynamic thermal stresses in a semispace due to the action of a plane internal nucleus of thermoelastic strain.