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International Review on Modelling and Simulations  Vol. 3 N. 5---- Part A

International Review on Modelling and Simulations  Vol. 3 N. 5---- Part B




go to top    International Review on Modelling and Simulations  - October 2010 - Papers (Part A)




go to top     International Review on Modelling and Simulations  - October 2010 - Papers (Part B)



Special issue;

selected papers from

                1st International Conference on Modelling and Simulations

                VIRTUAL FORUM (ICOMOS-VF 2010)




International Review on Modelling and Simulations - Papers (Part A)



go to top   Stability Study Domain with Parameters Fluctuation of Mamdani Type Fuzzy Control Systems
         by Basma Zahra, Anis Sakly, Mohamed Benrejeb

         Vol. 3. n. 5, pp. 746-752


Abstract - This paper proposes a stability study of particular class of Mamdani fuzzy control systems for elaborating stability domains. The approach presented is based on the convergence of regular vector norms, where the comparison, the overvaluing principle and the Borne and Gentina criterion are used. The system to be controlled, given as an application, is a first order system with variable parameters. The stability study allows getting stability domains with system parameters fluctuation.
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Keywords:  Mamdani fuzzy control systems, Global asymptotic stability, Stability domains, Borne and Gentina Criterion, Parameters fluctuation.



go to top   Neutral Point Balancing for Three Phase Three Level Voltage Source Converter- (Case Study: STATCOM)
         by M. S. Javadi, M. Joorabian, S. Gh. Seifossadat, B. Noshad

         Vol. 3. n. 5, pp. 753-758


Abstract - The neutral point unbalance is a problem which results in three-level inverter when the neutral point is connected to charging current for longer periods than to discharging currents (or vice-versa). Although the dc voltage regulator works properly, the inequality between charging and discharging neutral point current results in an unbalance between the dc voltage across the upper and lower capacitors. This is an undesirable characteristic since even if the converter is properly modulated the resulting output waveform becomes asymmetric about the x-axis and consequently, similar distortion results in the line currents. In this case, the neutral point connection time is controlled since the modified-PWM scheme is easily modified and the concept is relatively straightforward.
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Keywords:  STATCOM, Three level inverter, Voltage Source Converter, Neutral Point Balancing.



go to top   Non Linear Average Model of Switching Loss Using in a Virtual Prototyping
         by R. Benachour, S. Latreche, M. E. H. Latreche, C. Gontrand

         Vol. 3. n. 5, pp. 759-766


Abstract - In power electronic integration design, the virtual prototyping is the most important stage during the design flow. To obtain accurate results from the prototyping, it is necessary to estimate the losses in different operating function modes.
This paper presents a new approach, which consists of a non ideal prototyping constituted by a non linear average model of power loss in switching operating mode. This model was described by VHDL-AMS and applied to three-phase voltage source inverter based on IGBTs. It permits to predict the energy and the power losses of the voltage source inverter and estimate the adequate system parameters for a high operating performance.

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Keywords:  IGBT, Non Linear Average Model, Power Loss, Virtual Prototyping, Voltage Inverter.



go to top   Vector Control of Induction Motor Drive Based on Mixed Multi-cell Cascaded Inverter
         by Ali Ajami, Mehdi Armaghan

         Vol. 3. n. 5, pp. 767-774


Abstract - This paper presents indirect vector control for induction motor drive using 13-level mixed Multi-cell cascaded multilevel inverter. The poor quality of voltage and current of a conventional inverter fed induction machine is due to the presence of harmonics and hence there is significant level of energy losses. The mixed Multi-cell cascaded multilevel inverter is used to reduce the harmonics. This inverter is based on a new cell obtained from the mixture of the two most popular Multi-cell topologies, Flying Capacitor and Cascaded Multi-cell inverter. The new cell provides a high number of output levels, high modularity, low number of components and low losses. It will be shown that the rotor speed and torque ripples are eliminated by using the proposed inverter. The results of simulation carried out by using MATLAB/SIMULINK software confirm the high dynamic performance of the induction motor drive.
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Keywords:  Induction Motor Drive, Speed Control, Mixed Multi-cell Cascaded Inverter.



go to top   Robust Adaptive Observer in the Direct Field Oriented Control of Induction Motor with Stator and Rotor Resistance Estimation
         by M. Chenafa, A. Bouhenna, A. Mansouri, A. Valera

         Vol. 3. n. 5, pp. 775-783


Abstract - This paper deals with the simultaneous estimation of the rotor flux and the stator resistance of induction motor. The proposed observer assumes that only the motor speed and the stator currents are measured. The use of the Lyapunov's theory for the flux observer stability analysis permits to give an adaptive law for the on-line stator resistance estimation. This observer is combined with a direct field oriented control to achieve a robust speed and flux control. Also, to control the speed of the induction motor, we propose a solution with two loops to obtain simultaneous performance in tracking and regulation. Simulation results are presented to evaluate the performances of this control-observer structure scheme.
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Keywords:  Induction motor drive, adaptive observer, stator resistance estimation.



go to top   Harmonic Analysis of Induction Motor by Comsol Multi-Physic Software
         by Hassan Abniki, Mohammad Taghi Nabavi Razavi, Saeed Mohajer Yami

         Vol. 3. n. 5, pp. 784-790


Abstract - Researches show performance of motor controller directly depends on behavior of motor, its features and parameters, so using full or accurate model for induction motor design, brings better and robust motor control. In this paper, after analyzing of the induction motor models and its parameter estimation, it is paid to analyze the induction motor performance under harmonic condition. Moreover, parameter estimation is performed by two dimension (2D) Finite element method.
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Keywords:  Induction motor, harmonic analyzing, parameter estimation, Comsol multi-physics software.



go to top   Study and design of a Hybrid linear actuator for a railway system
         by M. Imed, F. Mourad, R. Habib

         Vol. 3. n. 5, pp. 791-795


Abstract - A Railroad switch is provided to move the points from one position to the other (change the points). Historically, this would require a lever to be moved by a human operator, and some switches are still controlled this way. However, most are now operated by a remotely controlled electric DC motor rotating or by pneumatic or hydraulic actuation. In this paper, we present a hybrid linear actuator for a railway application. Special attention was made to reduce congestion and sources of frequent breakdowns that require periodic maintenance to preventive maintenance and makes the system expensive.
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Keywords:  CAO, finite-element analysis, linear incremental actuator, permanent magnet, Switched Reluctance.



go to top   Influence of Geometric Parameters upon Electromagnetic Performance and Vibratory Behavior of Permanent Magnet Machines
         by N. Ferkha, F. Peyraut, M. R. Mekideche, A Miraoui

         Vol. 3. n. 5, pp. 796-802


Abstract - Permanent magnet synchronous machines (PMSM) have high efficiency and torque density, and have already been employed in hybrid electric vehicles. However, one of their disadvantages is the inherent cogging torque, which is a kind of torque ripple and it would be better to minimize. This torque, sometimes, can be an important source of noise and vibrations. In this paper, the effect of the geometric characteristics of the stator on the vibratory behavior of electrical machines is illustrated. The optimum geometry for obtaining a minimum vibration level has been reached. For this purpose, an approach by using the Artificial Intelligent (AI) and the Finite Element Method (FEM) is proposed to solve the magneto-mechanical problem of geometrical parameters identification in the optimization process. The obtained results by Genetic Algorithm (GA) method and those obtained with Gauss method of second order (BFGS) have been compared.
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Keywords:  Vibration reduction, Permanent magnet synchronous machines, Genetic algorithm, Neural network, Finite element method, Optimal design.



go to top   Comparison and Detection of Abnormal Conditions in Induction Motors
         by Mehrdad Heidari, Davar Mirabbasi, S. Ghodrattollah Seifossadat, Reza Kianinezhad

         Vol. 3. n. 5, pp. 803-808


Abstract - Deficiencies like unbalanced voltages or harmonics in the voltage source could result in problems like excessive losses, over-voltages, mechanical oscillations, and interference with control electronics. Detecting these abnormal conditions in the machine is of great importance in the interaction of the electrical machine and the power grid. In this paper the effect of the unbalanced voltages , harmonics and flicker on the motor performance, have been investigated. Then, monitoring these unhealthy condition using electrical machine parameters is carried out. In this case, motor itself can act as the sensor that detects abnormal conditions.
Also this paper investigates the negative effects of unbalanced sinusoidal voltage which always present in the power supply over balanced (inverter supply) non-sinusoidal voltage on the performance of induction motor in terms of line currents, power factor and efficiency. According to the test results and analysis, the negative effects of unbalanced sinusoidal voltage are more than the balanced no sinusoidal voltage on the motor's performance.

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Keywords:  Induction Motor, Unbalance Voltages, Harmonic, Flicker.



go to top   Piecewise Constant Orthogonal Based Estimator in Vector Controlled Drives of Induction Motors
         by Ehsan Ajily, Jalal Nazarzadeh

         Vol. 3. n. 5, pp. 809-816


Abstract - The accurate knowledge of the rotor parameters is critical for a good performance of the Rotor Field Oriented Control (RFOC) drives. This paper presents a new online method to estimate the rotor resistance in vector controlled induction motor drives. The nonlinear differential equations of the electrical machine can be restated in piecewise algebraic equations by using of appropriate Piecewise Constant Orthogonal Functions (PCOF) in company with the measured input-output signals, so the rotor parameters would be estimated by formulation of dynamic system with operational matrices. The application of the method is simple and it needs no extra injected signals. Because the measured signals are integrated in time intervals to calculate the basis function coefficients, the overall destroyer effects of the noise would be reduced, too. The simulation results prove the ease and accuracy of the proposed method.
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Keywords:  Rotor Resistance Estimation, Rotor Field Oriented Control (RFOC), Block Pulse Functions, Piecewise Constant Orthogonal Functions (PCOF).



go to top   Simplified Vector Control Algorithm for Induction Motor Drives Based on Sophisticated Look-up Tables
         by K. Satyanarayana, J. Amarnath, A. Kailasa Rao, T. Bramhananda Reddy

         Vol. 3. n. 5, pp. 817-826


Abstract - This paper presents a simple and novel vector control technique for induction motor drives based on sophisticated look-up tables. Vector control and direct torque control (DTC) are two popular approaches for high-performance drives. Though these algorithms give better dynamic torque response, vector control algorithm uses reference frame transformations and DTC gives large ripple in steady state current, torque and flux. To overcome these drawbacks, the proposed vector control algorithm combines the principles of both vector control and DTC. In the proposed algorithm, the d- and q-axes reference currents are generated as per conventional vector control algorithm and regulated according to a switching table as given in DTC. This paper presents two switching tables. Switching table-I is based on the conventional DTC principle, which gives good performance with increased common mode voltage variations. To reduce the common mode voltage variations, switching table-II is presented. To validate the proposed method numerical simulations have been carried out and compared with the existing algorithms. The simulation results show the effectiveness of the proposed technique.
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Keywords:  DTC, Induction motor, switching table, vector control.



go to top   Applying SVM and RBF Networks for Classifying Disturbances in Synchronous Generators Based on Fuzzy Characteristic Extraction of Time Zone Information
         by A. R. Shafighy, S. M. Hassan Hosseini, H. Chahkandi Nejad, R. Jahani, S. Zarrabian, V. Karimpoor

         Vol. 3. n. 5, pp. 827-832


Abstract - This paper provides a new approach to the application of classifier networks – Support Vector Machine (SVM) & Radial Basis Function (RBF) – for classifying disturbances in the synchronous generators in operational mode through time zone measurements. Optimal components of the patterns have been selected by SHAHYAT clustering algorithm and a fuzzy optimization index among a wide spectrum of the training patterns. Rated values of synchronous machines are also considered as a deviation index. Trained network is simulated by immediate measurements and tested through classifying disturbances in the generator. It is noted that the patterns studied in this paper include generators which have been categorized based on their dynamical parameters. Finally, performance of the SVM and RBF networks for determination of fault zones is compared to each other.
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Keywords:  Disturbances of operational zone; Fuzzy optimization index: Xie-Beni; SHAHYAT clustering algorithm; SVM and RBF networks; Synchronous generator.



go to top   Dual Rotor Structure with Modified Performance for Circumferential Hysteresis Synchronous Motors
         by Mohammad Modarres, Abolfazl Vahedi, Mohammad Reza Ghazanchaei

         Vol. 3. n. 5, pp. 833-839


Abstract - The hysteresis motors have some usage limitations such as low power factor, low efficiency and small torque density. In this study a new topology for conventional hysteresis motors is proposed in order to improve performance characteristics of conventional motors. This structure with unique performance is named ‘dual-rotor hysteresis motor’ (DRHM). In order to simulate the proposed model a 3D finite element model is used that gives us a better insight of motor performance and has high level of accuracy. Optimum thickness for both inner and outer hysteresis ring is searched in data space considering maximum current density constrain. Concept of complex permeability is used for modeling the hysteresis ring in ellipse form and Simulation is based upon Maxwell’s field equations considering the case of a circumferential flux type machine at synchronous speed. Meanwhile, for prototype motor new configuration for winding is presented that leads to reduction in ohmic losses.
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Keywords:  Hysteresis motor – 3D finite element model – complex permeability – Double rotor Motor- Motor winding.



go to top   The Source-Side Inductance Based Adaptive Hysteresis Band Current Control to be Employed in Active Power Filters
         by Hani Vahedi, Abdolreza Sheikholeslami

         Vol. 3. n. 5, pp. 840-845


Abstract - Hysteresis Current control (HCC) is one of the simplest and fastest modulation techniques, but the variable switching frequency caused by fixed-band HCC is the main issue. To remedy this problem, adaptive HCC has been introduced in literature leads to fix the switching frequency and decrease the switching losses consequently. However, these methods have not considered the source-side inductance effect on the calculation of the hysteresis band (HB). Therefore, the calculated HBs have been rough and thereby, the resulted switching frequencies become almost variable. To overcome this situation, a modified adaptive hysteresis band method applied to a three-phase APF based on involving the source-side inductance in HB extraction is proposed. Employing the proposed method to control an APF leads to an accurate modulation performance with the least possible switching frequency required in a filtering procedure. Furthermore, by applying this method, THD of the source-side currents is distinctly decreased in comparison with those which are gained by using the conventional variable-band methods. In addition, the mathematical proves beside analytical assessment of the proposed method as well as other types of hysteresis current control methods are presented. Several simulations are done using MATLAB/Simulink to verify validity of the proposed method.
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Keywords:  Active Power Filter; Hysteresis Current Control; Instantaneous Power Theory; Power System Harmonic; Source Side Inductance; Voltage Source Inverter (VSI).



go to top   Power Oscillation Index – A Tool for Investigation into Unbalance Phenomena in the Distribution Networks
         by Rade M. Ciric, Dalgerti L. Milanez

         Vol. 3. n. 5, pp. 846-851


Abstract - Unbalance and harmonics are two major distortions in the three-phase distribution systems. In this paper an investigation into unbalance phenomena in the distribution networks using instantaneous space vector theory, is presented. Power oscillation index (POI) and effective power factor (PFe) are calculated in the network nodes for several unbalance loading conditions. For system analysis a general power flow algorithm for three-phase four-wire radial distribution networks, based on backward-forward technique, is applied. Results obtained from several case studies using medium and low voltage test feeder with unbalanced load, are presented and discussed.
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Keywords:  Distribution networks, load unbalance, instantaneous space vector theory, power oscillation, losses.



go to top   Multiobjective Optimisation Problem of Regional Power Electric Networks Development
         by S. Filipiak

         Vol. 3. n. 5, pp. 852-856

Abstract - The paper is concerned to the problems of the distribution network systems optimisation, development and operation. An optimisation method of the regional distribution network reliability level, using the evolutionary approach, has been presented in the paper.
In the elaborated method the decisive variables, essential from the network operation reliability point of view, described with the use of fuzzy sets theory, have been taken into account in the formulated objective function. The proposed method enables to determine best – from the assumed criterion point of view - modernisation variants of distribution network systems.

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Keywords:  Optimisation, Evolutionary Algorithms, Regional Power Distribution Networks.



go to top   Bifurcation Analysis of Equilibrium and Limit Cycles in Three Node Power System
         by R. Ben Neji, F. Bacha, M. Gasmi

         Vol. 3. n. 5, pp. 857-863

Abstract - Stability of power systems becomes one of the major precautions with electricity suppliers. These systems must maintain a steady state in the neighborhood of the operating points so as a result of severe disturbances. In this paper we study the dynamic stability of the three node power system by the bifurcation theory and the stability of limit cycles emerging from a subcritical or supercritical Hopf bifurcation by computing the first Lyapunov coefficient. In the other hand we compute the continuation of the Saddle Node bifurcation with liberating two parameters the gain of the regulator AVR and the mechanical input power of the generator.
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Keywords:  Power system, Bifuractions, First Lyapunov Coeifficient, Limit cycle.



go to top   Lyapunov Based Self-tuning Control of Wind Energy Conversion System
         by S. V. Heidari, M. Sedighizadeh, A. Rezazadeh, M. Ahmadzadeh

         Vol. 3. n. 5, pp. 864-869


Abstract - Nonlinear characteristics of wind turbines and electric generators necessitate complicated and nonlinear control of grid connected Wind Energy Conversion Systems (WECS). This paper proposes a Lyapunov based self-tuning Proportional-Integral- Derivative (PID) control approach for WECS control. This self-tuning PID control is founded on the combination of two controllers, i.e. a self-tuning PID controller, which drives the tracking error to zero with user specified dynamics, and a supervisory controller, based on crude bounds of the system’s nonlinearities. The supervisory controller guarantees the stability of closed-loop nonlinear PID control system. The form of the supervisory control and the adaptation law are derived from a Lyapunov based stability analysis. The results are applied to a typical WECS, presenting the ability of the proposed method.
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Keywords:  Adaptive, Control, Wind Turbine, Lyapunov, Supervisory Control.



go to top   A New Approach for Optimal Unit Commitment of Large Scale Power System
         by A. R. Shafighi, R. Jahani, M. Fazli, H. A. Shayanfar, S. M. T. Bathaee

         Vol. 3. n. 5, pp. 870-875


Abstract - The solution of the unit commitment problem (UCP) is a complex optimization problem. The exact solution of the UCP can he obtained by a complete enumeration of all feasible combinations of generating units, which could be a huge number. The objective is to find the generation scheduling such that the total operating cost can be minimized, when subjected to a variety of constraints. This also means that it is desirable to find the optimal generating unit commitment in the power system for the next hours. Fast Messy Genetic Algorithm (FMGA) is applied to the calculation of optimal unit commitment problem. The test results demonstrate that not only the FMGA procedure consider is the constraints very well, but also has some advantages, such as good convergence, fast calculating speed and high precision. The FMGA is applied to the widely used ten-unit test system and its multiples (10-100). Comparing our results with those of many UC solving methods demonstrate that not only the FMGA procedure consider is the constraints very well, but also has some advantages, such as good convergence, fast calculating speed and high precision.
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Keywords:  Fast Messy Genetic Algorithm, Power System (FMGA), Unit Commitment, System Constraints.



go to top   Voltage Stability Analysis and Contingency Ranking in Power Systems Using Neural Network
         by M. Hosseini

         Vol. 3. n. 5, pp. 876-881


Abstract - In this paper Voltage stability and contingency ranking in the steady-state condition have been studied. Three indices are proposed which reveals the effect of line outage contingency on power system. These indices indicate also the severity degree of voltage instability in whole of power system and used for ranking of contingencies. In this study both of single line outage and double lines outage contingency are investigated. The off-line complete AC load flow calculations are considered to calculate indices for evaluation of voltage stability and contingency screening. Limits of active and reactive power in PV buses in test system are considered. A Multi Layered Perceptron (MLP) neural network is used for estimating the severity indices. Utilization of Neural network, causes this technique be useful for speed up in on-line application. The study has been carried out on the IEEE 14 bus test system and comparing the results demonstrated that all of indices almost have same result in contingencies ranking list and therefore makes this technique more reliable for estimation of voltage instability in whole of power system in on-line application.
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Keywords:  Neural Network, Voltage Stability, Contingency Ranking.



go to top   Contingency Studies of a Real Power System and Violation Mitigation Measures
         by Ning Kang, Yuan Liao

         Vol. 3. n. 5, pp. 882-887


Abstract - This paper presents the contingency studies of a large utility system based on North American Electric Reliability Corporation (NERC) requirements. We have identified the problem contingencies that cause either low voltage level or branch overloading. In general, two measures have been adopted to mitigate violation, which are reducing system load and reducing local load. The critical load level (CLL) to eliminate either voltage or flow violations has been obtained.
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Keywords:  Power System, Contingency Analysis, Double Contingency Analysis, Critical Load Level, Power System Simulator for Engineering.



go to top   Fault Location in Overhead Power Lines Using the IEC61850 International Protocol
         by Blagojce Stojcevski, Akhtar Kalam

         Vol. 3. n. 5, pp. 888-899


Abstract - Power utilities over the past decade have been fortunate enough to perfect their operations and business process automation due to advances in communication protocols, network technologies and substation equipment. The majority of utilities have already implemented the IEC61850 protocol into their existing framework, but it is anticipated that within the next 10 to 15 years all substations worldwide will eventually undergo the transformation. This will ultimately lead to low level stockpiling of auxiliary equipment, ample use of Ethernet technologies, increased interoperability between vendor specific IEDs and the ability to analyse various real-life fault scenarios via the use of SCADA. However, more prospects are still available in order to meet engineering requirements, especially in the field of algorithm derivation. The authors of this paper aim to overview a number of Substation Automation aspects with the intent of evaluating the pros and cons of the IEC61850 protocol. The authors provide an original configuration flow of the processes required to achieve interoperability, before giving insight into different types of IED operating characteristics and fault locator algorithms. The derivation of an unsymmetrical single phase-to-ground fault is also exposed using a differential equation algorithm. The targeted audience of this paper includes researchers, automation engineers and protection engineers either with underlying knowledge of the IEC61850 protocol or higher.
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Keywords:  Generic Object Oriented Substation Event (GOOSE), Intelligent Electronic Device (IED), Substation Automation System (SAS), Substation Configuration Language (SCL), Supervisory Control and Data Acquisition (SCADA), Unsymmetrical Fault.



go to top   Power Systems Stabilization Using SVC and STATCOM
         by A. M. Hemeida, Y. A. Mobarak, M. R. Mousa

         Vol. 3. n. 5, pp. 900-910


Abstract - This paper presents an in-depth investigation of the effect of the Static Var Compensator SVC and the Static Synchronous Compensator STATCOM on the power system dynamic performance theoretically and by exact digital simulation. A 48-pulse Gate Turn-off GTO dc-ac converter model is designed to represent the operation of the STATCOM within a power transmission system. The major factors of the SVC and STATCOM instability analyzed and a new Automatic Gain Controller AGC proposed to ensure the stable operation of the SVC and STATCOM for different types of load. The effect of SVC and STATCOM on the power system dynamic performance is clear when applied to a real power system. In addition, all details of the models implementation, the controls used, and the data for studied system are providing. The digital simulations prove the effect of inserting both SVC and STATCOM in improving the power system dynamic performance, and damping the power systems oscillations very fast with low overshoot and undershoot with better control quality. The Matlab/Simulink toolbox is used for the time simulations.
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Keywords:  Power System stability, Static VAR Compensator, STATCOM. Automatic Gain Controller.



go to top   Fault Duration for Voltage Instability and Voltage Collapse Initiation as Influenced by Load Window
         by Ashraf Mohamed Hemeida, Y. A. Mobarak, M. M. Hussein

         Vol. 3. n. 5, pp. 911-917


Abstract - Load window is defined as the participation percentage of different loads at any load bus, which has more than one kind of loads. This paper, study the effect of excitation control system parameters on the fault duration which causes initiation of voltage instability and or voltage collapses of power systems. The effect of the excitation control system parameters within its limits are considered constant on the fault duration, which cause voltage instability initiation when a three phase short-circuit occurs at certain node in the studied system or opening the transmission line between two nodes in A three machine nine bus power system. The fault durations necessary for voltage instabilities initiation in power systems during a wide range of the system operating conditions is studied and obtained. A clear discrimination between voltage instability which occurs in the form of oscillations or fluctuations and voltage collapse occurs as rapid voltage fall to a certain level, is made. The effect of the load window on the fault duration which cause initiation of voltage instability has been investigated based on load window which consists of constant impedance load with (constant current load, or constant power load) at all load buses, and induction motors load is obtained. The Matlab software is used to model and solve the studied power system equations.
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Keywords:  Voltage stability - Voltage instability – Voltage Collapse – Load Window.



go to top   Protection of Three phase Power Transformers feeding a Load by using Current Limiting Technologies Devices in Power Grids
         by T. Madiba, M. W. Siti, A. A. Jimoh

         Vol. 3. n. 5, pp. 918-925


Abstract - In this paper, the performance analysis of the use of the Thyristor Controlled Fault Current Limiter (TCFCL) are made compared to the Circuit Breakers (CBs) used to protect the power transformers while different types of faults occur. The simulations are performed with PSCAD/EDMT and the results are discussed based on the effects such as time-response, post fault current level, etc.
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Keywords:  Fault Current Limiter, Circuit Breakers, PSCAD/EDMT, Power Transformers, Post fault conditions.



go to top   Wind Farm Surge Arresters Energy Capability and Risk of Failure Analysis
         by Petar Sarajčev

         Vol. 3. n. 5, pp. 926-937


Abstract - This paper presents the analysis of the wind farm surge arresters energy capability in respect to lightning overvoltages. Furthermore, the wind farm surge arresters risk of failure analysis is presented in this paper. These two above mentioned aspects form a vital part of the surge arrester selection procedure for the wind farms. It should be emphasized that the wind farm surge arrester energy capability is, apart from the switching overvoltages, based on the lightning overvoltages as well, to which the wind farm is particularly exposed. Hence, a detailed computational procedure, utilizing the electromagnetic transients program (EMTP), and combined with sophisticated high-frequency wind farm components models, is needed to accomplish this task. This procedure, accompanied with a brief EMTP wind farm model description, will be provided in this paper. The wind farm surge arresters risk of failure analysis is based on the statistical approach, which combines statistical description of the arrester energy absorption failure with the statistical nature of lightning surge occurrences.
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Keywords:  Energy absorption, Lightning, Surge Arrester, Risk of Failure, Wind Farm.



go to top   An Application of Elitist-Based Genetic Algorithm for SVC Placement Considering Voltage Stability
         by M. Rezaie Estabragh, M. Mohammadian, M. Rashidinejad

         Vol. 3. n. 5, pp. 938-947


Abstract - The problem of improving the voltage stability in electrical networks is a major task that must be solved in an optimal manner. In this study, the mentioned optimality can be achieved by efficient usage of existing facilities alongside with installing FACTS devices. This paper deals a new strategy developed for optimizing Static VAR Compensator (SVC) placement to improve power system voltage stability margin, reducing power losses, voltage deviations and also SVC installing cost regarding to load increasing and generation scheduling patterns. This Method uses Elitist Genetic Algorithm (EGA) to reach the best performance, acceptable operation and identify the optimal location and best size of SVC. To demonstrate the validity and the convenience of EGA approach, it has been examined on IEEE-14 bus test system with promising results.
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Keywords:  Static voltage stability, Load ability limit, Power losses, SVC optimal placement, Elitist Genetic algorithm.



go to top   A new approach for modeling the Photovoltaic Cell using Orcad comparing with the Model done in Matlab
         by A. Blorfan, D. Flieller, P. Wira, G. Sturtzer, J. Merckle

         Vol. 3. n. 5, pp. 948-954


Abstract - This paper represents two model of photovoltaic, the first uses the Matlab, it explains the Photovoltaic Cell I-V Characterization and how we can get the Maximum peak power tracking(MPPT), the other is done in Orcad(new version of Pspice), in Orcad we propose an electronic circuit to be realize easily, a newer technique will be discussed in the last one, it is a new geometric approach, it depends on the characteristic of the photovoltaic diode, this approach give an approximation reasonable to this model, more than the classical one.
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Keywords:  Solar cell, photovoltaic, MPPT, Simulink, Orcad.



go to top   A Powertrain Vehicle Model for Look-ahead Control
         by Behnam Ganji, Abbas Z. Kouzani

         Vol. 3. n. 5, pp. 955-962


Abstract - This paper presents a powertrain model for a vehicle taking into account the impact of trajectory specifications. The model enjoys a quasi-static approach with a backward facing method. The key feature of the model is its presentation of the dynamic of the vehicle based on the road information. This ability makes the method suitable for use in look-ahead energy management and fuel economy optimal control problems. In order to maintain the operation of the combustion engine near its efficient region, a fuzzy control system with a continuous variable transmission is applied. Simulations are carried out using real road data. The results are presented and discussed.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Powetrain vehicle modeling, quasi-static backward facing, fuzzy logic, simulation.



go to top   Electromagnetic Modelling of Planar Microwave Structures with Dielectric Resonators, Microwave Filtering Application
         by S. Mekerta

         Vol. 3. n. 5, pp. 963-971


Abstract - The needs for equipment using microwaves and microwave technology have been
increasing in the last ten years. At the beginning of the 21st century relating to the field of telecommunications and aerospace, the microwave devices were miniaturised. The devices used in wireless communications tend to have smaller dimensions and larger capacity. Therefore the operating frequency shifts to higher range, notably the GHz domain.
We proceed to study completely a microwave Tchebyscheff band-stop filter with localized elements then with distributed elements associated with two dielectric cylindrical resonators on TE01δmode, coupled to a microstrip line. A first theoretical part which need a great number of calculations by a numerical method of finite elements is followed by a simulation which uses electromagnetic and circuit software which validates the results of the theoretical analyses. Experimental results are presented and demonstrate excellent agreement with the simulation.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Modelling , band-stop filter, dielectric resonator, microstrip, finite element method, coupling.



go to top   Determination of Electric Field and Thermal Distribution In power Cable With Cavity
         by S. Lachini, A. Gholami, M. Mirzaie

         Vol. 3. n. 5, pp. 972-982


Abstract - Power cables as one of main components of power networks, play an important role in electric power transmission. Because of probable incidence of water treeing phenomena and also air cavity and humidity in electric insulators electric field increases locally and can lead to breakdown in insulation.
The temperature rise in cable is mainly due to Joule’s loss in conductor and also eddy loss in sheath. Using the simplified cable model, the thermal distribution in single phase is calculated.
The main subject of the paper is effect of the temperature on the electric field distribution in high voltage cable. Therefore cable is considered inform a composite insulation and is modeled by finite Element method. The cable has been simulated in present humidity, air cavity and also considering of environment temperature and then electric field and thermal distribution have been determined by using Finite Element Method.
In this work, electric field distribution inside water and also air cavities existing in polyethylene insulation of one 10Kv cable has been simulated and calculated by Comsol and Maxwell softwares. Since electric field intensity in cable depends on various factors such as shape of cavity, cavity permittivity coefficient and its position with respect to cable center, therefore by considering these parameters, FEM simulation has been done and the results are discussed. Finally relation between local field congestion in water drops corners and insulation failure possibility which can lead to insulator complete breakdown, is studied.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Power cable, Void, Moisture, Finite Element Method (FEM) , Electric Field, Thermal Distribution.



go to top   A Multilayer Model of Loaded Solder Joints
         by Walter Gschohsmann, Robert Scheiber

         Vol. 3. n. 5, pp. 983-987


Abstract - A multilayer model of a solder joint is presented in this paper capable to simulate the stress/strain distribution in such connections after deformations. Finite Element methods are applied to obtain more expressive results compared to approximate calculations in elasticity/plasticity. The proposed layer structure, including intermetalic layers, is justified by relevant examples on lead-free material in the recent research work. Simulated deformations after displacement steps are compared to the behavior of loaded joints in shear tests. Statements on stability are supported by various strain plots in critical regions. Especially the solder volume at the ends of the joints close to the metallization shows a disadvantageous stress concentration that indicates centers of possible structural failures. An important extension of the model is the inclusion of different sized pores in the solder joint. Modeling, visualization and the properties of pores are discussed sufficiently. The multilayer model contributes to increase the quality of solder joints and moreover its flexibility enables an easy adaptation to future tasks in research and electronic engineering.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Modeling solder joints, FE simulation of loaded solder joints.



go to top   Controlling Ferroresonance in Voltage Transformer by Considering Circuit Breaker Shunt Resistance Including Transformer Nonlinear Core Losses Effect
         by Hamid Radmanesh

         Vol. 3. n. 5, pp. 988-996


Abstract - Ferroresonance or nonlinear resonance is a complex electrical phenomenon, which may cause over voltages and over currents in the electrical power system which endangers the system reliability and continuous safe operating. The ability to predict or confirm ferroresonance depends primarily on the accuracy of the transformer model used by the computer simulation. An overview of available literature and contributors to this area is provided. This paper studies the effect of circuit breaker shunt resistance on the controlling chaotic ferroresonance in a voltage transformer while the core losses of the voltage transformer core are highly nonlinear. It is expected that this resistance generally can cause ferroresonance ‘dropout'. For confirmation this aspect Simulation has been done on a one phase voltage transformer rated 100VA, 275kV. The magnetization characteristic of the transformer is modeled by a single-value two-term polynomial with q=7. The simulation results reveal that considering the shunt resistance on the circuit breaker in the case of nonlinear core losses, exhibits a great mitigating effect on ferroresonance over voltages. Significant effect on the onset of chaos, the range of parameter values that may lead to chaos along with ferroresonance over voltages has been obtained and presented.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Circuit breakers Shunt Resistance, Nonlinear Core Losses Effect, Chaos, Bifurcation, Ferroresonance, Voltage Transformers.



go to top   Clustering Based World Modelling in Highways
         by Reza Rasoolinezhad, Reza Ebrahimpour, Mohammad Bagher Menhaj

         Vol. 3. n. 5, pp. 997-1001


Abstract - Autonomous mapping and modelling of the environment is a primary challenge for researchers working on intelligent navigation platforms. The resulted maps and models are very useful to correct control parameters and increase the safety of travelling process. Vision is finding more and more importance in this field. In this paper, we present a new and simple procedure to model the pass of navigation in highways without using any a priori information. We developed a novel algorithm based on Hough transform and K-means clustering technique to find heading direction and draw a map of environment in the same time. Heading correction using the same technique has been addressed in a separate paper previously. We focus on mapping here.
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Keywords:  World Modeling, Map Generation, Hough Transform, K-Means Clustering.



go to top   PV System Matlab Simulation Model for Two MPPT Methods
         by Yuncong Jiang, Jaber A. Abu Qahouq

         Vol. 3. n. 5, pp. 1002-1009


Abstract - Maximum power point tracking (MPPT) techniques are used in photovoltaic systems to maximize solar array output power under variable conditions. This paper presents a complete simulation model of a standalone PV system using PLECS® and Matlab/Simulink, including the simulation of Solar Photovoltaic (PV) cells, realization of MPPT algorithm and power stage control. Two MPPT methods are simulated and compared. The first is the power method which senses the solar array power and voltage to track the maximum power point (MPP) and the second is the output current method which tracks the MPP by sensing only the load current.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Model, Simulation, Maximum Power Point Tracking, Perturb and Observe Algorithm, Solar Energy.



go to top   Oscillation Amplitude Analysis of Colpitts Oscillators Using FDTD Technique
         by S. R. Ardali, G. Ardeshir, H. M. Naimi

         Vol. 3. n. 5, pp. 1010-1016


Abstract - In this paper, a new numerical method for analysis of amplitude of Colpitts oscillator is presented. The equations from large signal analysis are obtained by considering three operating regions of MOS transistor; cutoff, linear and saturation. The analysis is based on finite difference time domain (FDTD) method that is a numerical method to estimate the output waveform. Using this method the amplitude of steady state and transient behavior of output waveform has been found. The amplitude calculated from this approach has a very good agreement with simulation for a large range of circuit parameters. The simulation results show high validity of the proposed equations for analysis of the oscillator amplitude.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Oscillator, MOS Colpitts oscillator, oscillation amplitude, finite difference time domain (FDTD).



go to top   Techniques of Transmitting Beamforming with a Fixed Total Number of Feedback Bits
         by Imen Sfaihi, Noureddine Hamdi, Ammar Bouallegue

         Vol. 3. n. 5, pp. 1017-1022


Abstract - In limited feedback Transmit Beamforming for MISO systems, the most goals is to respect the constraints of the resources of the feedback channel (bandwidth and power). In the prior work systems, each user quantizes her channel state information (CSI) and fed back the corresponding number of bits to the base station every channel coherence time. Then, for a large number of users and a fixed number of feedback bits per user, the total number of feedback bits is large and the goal is not respected. In this paper, we show that the preference is to fix the total number of feedback bits. Accordingly, the number of users and the number of the feedback per user will be variable. And the number of active users is selected arbitrary from a large number of users. To analyze and validate the performance of this proposed idea, we are applying it to some techniques of transmitting Beamforming such as "the opportunistic Beamformnig (OBF)" and "the switched Sub Codebook (SSC)". Moreover, we study these two techniques with introducing the Schmidt algorithm (SA) to control the generated weights.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  MISO, Transmit Beamforming, limited feedback, CSI, fix, variable, OBF, SSC, SA.



go to top   Computation of a Passive Scalar in a Flow Field by Using Unstructured Grid Method
         by Slimani Abdelkader, Belkacem Abdellah, Rebhi Mebrouk

         Vol. 3. n. 5, pp. 1023-1028


Abstract - A finite volume method for quadrilaterals unstructured mesh is developed to predict the two dimensional steady-state solutions of advection-diffusion equation. In this scheme, based on the integration around the polygonal control volume, the derivatives of the advection-diffusion equation must be converted into closed line integrals using same formulation of the Stokes theorem. To valid the accuracy of the method two numerical experiments with known analytical solutions are used: Advection-Diffusion in rotating annular region and advection-diffusion in an annulus (cases with curved boundaries).The numerical results show good agreement with analytical results. To demonstrate the order of accuracy, the average absolute percentage error versus the grid size is examined quantitatively.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Unstructured meshes, advection-diffusion equation, order of accuracy.



go to top   Temperature Profile Simulation Model Development for Demand Side Management
         by Venkateswara Sarma Mallela, Parmal Singh Solanki, Malcolm Allan, Chengke Zhou

         Vol. 3. n. 5, pp. 1029-1034


Abstract - Demand Side Management techniques facilitate in obtaining cost effective solutions to handle peak load scenarios by deferring installation of additional power generation. The hourly temperature profiles, particularly for temperature sensitive devices of residential load become important to estimate the load demand. In this paper, a mathematical model is developed to generate the hourly temperature profiles considering data based on maximum average, minimum average and average temperatures for all months in a year. Simulation code is developed using MATLAB and the results are in close agreement with the measured data of Oman. The model developed is a generic in nature and may be used for any location. The role of temperature sensitive devices becomes implicit when correlation between temperature and load are plotted. The viable demand side management strategies are discussed in paper to reduce the electricity demand.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Air-conditioners, Correlation coefficient, DSM, Temperature profiles, Simulation.




International Review on Modelling and Simulations - Papers (Part B)


Special issue;

selected papers from

                1st International Conference on Modelling and Simulations

                VIRTUAL FORUM (ICOMOS-VF 2010)


go to top   Libjit Linear Scan: a Model for Fast and Efficient Compilation
         by K. Kononenko

         Vol. 3. n. 5, pp. 1035-1044


Abstract - We present a software package for advanced just-in-time compilation. We solve this task using a new model. The efficiency of the model has been demonstrated in an experiment where a problem has been solved using three different algorithms. All three algorithms have shown that only this model significantly increases the quality of results. We propose a model of register allocation, which presents this task as a problem of analysis of a stream of real-time demands in a certain area. As a practical instance of this problem, we give an example of the following objects which appear in the field of radio-location; on a primary level, this requires the detection of a target and the tracking of that object (with a certain level of security and stability) takes place on a secondary level. The model has been implemented in a platform-independent open source package for advanced just-in-time compilation. The package has been created for embedded systems based on POSIX-compatible operating systems. Results are presented of research on a method of solving the problem of register allocation by applying a linear scan to ECMA-335 standard in the GNU Portable.NET just-in-time compiler. A few heuristic algorithms of register allocation were implemented and compared with each other. To demonstrate the benefits of the proposed model, we have used three algorithms recommended by various sources for fast dynamic compilation: the frequency of usage of variables, the method of simple linear scan with one live range, and its more advanced implementation with an aggressive splitting of live ranges. The results have been compared with various versions of Novell Mono, Microsoft .NET 2.0 and with several variants of implementation of Common Language Runtime, in which direct interpretations have been implemented with the usage of pointers to handlers, simple unrolling of interpreter loops, and an interpretation mode without control of register allocation.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Fast Compilation, Embedded Systems, CLI.



go to top   Computational Environment for Simulation and Optimization Process Decision-Making Systems Cogeneration from the Perspective of Sustainability for the Sugar Biofuel Industry
         by Jéferson M. Ortega, Jonathan A. A. de Oliveira, Sibelis A. T. F. Rocha

         Vol. 3. n. 5, pp. 1045-1054


Abstract - The upgrading of production systems and practice of sustainable development, with respect to the energy sector require changes in three segments: the generation, distribution and use of energy, pointing to the increased use of renewable resources, particularly biomass to reduce CO2 emissions, instead of fossil fuels which are the world's energy matrix. In this context, this paper presents a methodology and a computing environment that allows you to simulate and optimize the process of decision making in cogeneration systems from the perspective of economic, social and environmental. It was taken as a case study of the sugar industry in the state of Mato Grosso do Sul in Brazil, contextualizing the various features of the mechanisms of insertion encouraged to alternative sources of renewable energy currently in progress. After identifying and modeling the governing conditions (variables of interest) of a cogeneration system are presented Causal Loop Diagrams representing different causal relationships of events associated with the cogeneration of electricity by sugar and alcohol plants. By applying the technique of System Dynamics was able to assess the dynamics of business and interactive processes that influence their development. The application of a meta-heuristic (quantitative analysis) together with the simulation model to identify and consider the various influences of regulatory issues in decision making related to investment and hence manage the risks and opportunities that enable investment in cogeneration systems for the sugar industry that are currently being installed in the region. The creation of a new paradigm of efficiency in assessing the viability of cogeneration systems allows a qualitative analysis from the perspective of sustainable development.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Biomass, Cogeneration System, Sugar Industry, System Dynamic.



go to top   Dependability Distribution Substation 60/10 kV
         by H. Benaicha, A. Chaker, H. Kateb, R. Rahli

         Vol. 3. n. 5, pp. 1055-1062


Abstract - Ensuring the dependability techniques of electrical systems is a serious problem for the Algerian power distribution company. Choosing the network components is usually based on a practical approach. To address this lack, we propose in the present article to use methods dependability hat would efficiently enable to investigate the safety of electrical systems in terms of components choice, hence resulting in time and cost optimization. The method is based on functional analysis followed by modeling of system operation in the regime of normal power flow. On the basis of this model, the probabilistic characterization of system RAM is performed. Introducing the factors of importance enables to identify the most critical components of the system and to determine its RAM performances that should be improved for achieving a better global performance of the whole system. In order to demonstrate the advantage of such optimization methods, this work will be illustrated by a real case based on a 60/10 kV electrical distribution station.
Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Dependability, Electrical Network, Maintenance, RAM, Substation HV/LV.



go to top   On Load Tap Changing Transformer: Modeling, Simulation and Application to the Voltage Control of a CEB Substation
         by Sossou Houndedako, Sèmiyou Adedjouma, Gaston Houeto, Jean-Marie Kauffmann

            Vol. 3. n. 5, pp. 1063-1069


Abstract - In a distribution system, it is essential to maintain the voltage variation within a specified limit for satisfactory operation of connected customer equipments. Normally, this goal is achieved by controlling the operation of compensating devices, such as capacitors, shunt reactors, rotating or static VAr compensators and On Load Tap Changer (OLTC) on transformers. OLTC is a motor driven on-load tap changer controlled by an Automatic Voltage Regulator. It is one of the major contributing factors to power instability for a distribution network so the control scheme needs to be upgraded to have improved power stability. This paper deals with an upgrading of OLTC control scheme based on a line drop compensation with an inverse time temporization. It proposes also a simulating model with SimPowerSystems of Matlab in order to test and approve any regulating algorithm. A study case deals with the OLTC regulating transformer T5 of Vêdoko substation of CEB which provides with 63kV SBEE power plant of Akpakpa.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Automatic Control, Voltage, OLTC, Transformer.



go to top   Thermal Transient Regime Analysis for Fuses and Power Semiconductors
         by Adrian Plesca

          Vol. 3. n. 5, pp. 1070-1076


Abstract - The protection against overcurrents for power semiconductors are made usually with ultrafast fuses in series with semiconductor devices. To know the fuse’s heating during transient conditions is very important in order to calculate the pre-arcing times and to check the fuse’s temperatures at transient currents when they don’t have to work. The paper, based on specific thermal modelling and simulation software, shows a new fuse thermal quantity typical to transient operating conditions, the normalised thermal transient impedance and it results a new criteria to protect the power semiconductors using ultrafast fuses.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Fuses, Power Semiconductors, Transient Regime.



go to top   Thermal Analysis of Fuses and Busbar Connections at Different Type of Load Variations
         by Adrian Plesca

          Vol. 3. n. 5, pp. 1077-1086


Abstract - The paper, based on three-dimensional finite element method for modelling and simulation software, makes a comparison between the fast fuse geometry without busbar terminals and the one with these busbars mounted on it. The maximum temperature is lower in the second case when the thermal model had taken into consideration the busbar connections. Also, a thermal analysis for different type of load variations has been done in both cases of the fast fuse geometry with and without busbar terminals.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Fuses, Busbars, Thermal Modelling and Simulations.



go to top   A Study of Surplus Regenerative Energy at DC Electric Railway Substations Using Overhead Line Voltage and Feeder Current
         by Chang Han Bae

        Vol. 3. n. 5, pp. 1087-1092


Abstract - Regenerative inverter of DC electric railway system transfers the surplus regenerative energy caused by electric braking of Electric Multiple Units (EMUs) into the electric supply grid for reuse. In order to install the regenerative inverter with the most suitable power capacity, it is necessary to investigate the consumed and regenerative energy of the electric railway substations in advance. This paper presents an effective means of calculating the amount of the surplus regenerative energy at a DC electric railway substation using overhead line voltage and feeder current measured for a day. Using these measured data, the amount of the total and exchanged regenerative energy consumed in four feeders are calculated approximately and the cost reduction effect at a DC electric railway substation due to the reuse of regenerative energy is presented.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Regenerative Energy, Regenerative Inverter, DC Electric Railway System.



go to top   Near Field UHF RFID Tag Antenna Backed by a Conducting Loop Reflector
         by Jun-Jiat Tiang, Tien-Sze Lim, Fabian Kung

       Vol. 3. n. 5, pp. 1093-1096


Abstract - A novel UHF printed loop antenna backed by a conducting loop reflector is proposed for near field RFID tag antenna application. The backed conducting loop reflector is adopted to achieve stronger magnetic field distribution along the loop tag antenna in order to work properly in proximity to the water and metallic object. The proposed antenna is constructed on FR4 substrate with the dimension of 30 mm × 30 mm × 3.2 mm. The simulated results exhibit constant
current and uniform magnetic distribution to operate frequency at 915 MHz. The near field performance of the proposed antenna is practically verified by the read range measurement and compared with the commercially-available near field tag antenna to offer a promising solution of above-mentioned problems.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Near Field, UHF, Loop Antenna, RFID.



go to top   Current Harmonic and Environment Temperature Impacts on Transformers
         by S. B. Sadati, M. Yazdani-Asrami, M. Taghipour

       Vol. 3. n. 5, pp. 1097-1102


Abstract - Transformers are the main components in distribution systems that failure of them has many disadvantages for the system. The reason of most of these failures is increase of transformer's loss due to increase of harmonics particularly, current harmonics and environment or Ambient temperature. These losses cause increase of temperature in different parts of transformer especially; its hot spot and increase of this temperature can reduce useful life of transformer’s insulations. Therefore, be aware of harmonics values and contents, reduction of loading capacity of transformer and also, calculation of transformer's hot spot led to approximate remained life time of transformer seems essential. In this paper, additional to evaluation of equations related to loss and estimation of life time of transformer, measuring and sampling of a 400 kVA transformer's current and voltage has been done. Then, losses, remained life and load ability of that have been estimated under these situations according to equations and by using MATLAB/SIMULINK software.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Harmonic Currents, Load Ability, Life Time, MATLAB/SIMULINK Software Package, Measurement, Transformer, Useful Life.



go to top   Modeling and Simulation of Transformer Winding Fault Using MATLAB/SIMULINK
         by M. Yazdani-Asrami, E. Samadaei, S. Darvishi, M. Taghipour

        Vol. 3. n. 5, pp. 1103-1109


Abstract - For each transformer, windings and insulations are the most important elements economically and technically, so highly protection should be considered for them. The main fault that occurs in a transformer is internal short circuit through the winding, which may lead to serious damage in winding on transformer including winding deformation, interruption or even the explosion of the transformer because of oil's overheating. Consequently, winding need to be frequently checked to avoid major damages. In this paper, a new method for modeling and simulation of transformer’s winding fault has been presented. According to happened variation in line current and evaluation of its symmetrical component (positive, negative and zero sequences), easy and precise algorithm has been obtained that can be used for simulation of internal fault of transformer’s winding. The algorithm has been implemented for winding faults and has been simulated by MATLAB/SIMULINK software.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: MATLAB/SIMULINK Software, Modeling, Short Circuit, Simulation, Symmetrical Component, Transformer, Winding Fault.



go to top   Stability of the Flexible Pavements
         by Meziani Faroudja, Kahil Amar, Gabi Smail

           Vol. 3. n. 5, pp. 1110-1115


Abstract - The flexible pavements can call upon the techniques of treatment with a hydraulic binder or hydrocarbon whose advantages are far from being negligible, opposite increasingly heavy loads. The present study aims at, to confer on various materials used in the underlays of a flexible pavement density and cohesion, by addition of various percentages out of binders (cement and clay), and thus the realization of the concrete wearing courses bituminous, stable and impermeable, by aggregate addition of rubber, obtained by crushing of worn tires.
The mechanical properties of the various studied mixtures, are illustrated starting from the mechanical tests of laboratory, mainly: tests of compaction with Proctor modified and the tests of Marshall stability. The results obtained showed the influence of various materials added on the evolution of the bearing pressure of the studied mixtures.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Design and Construction of the Roadways, Treatment of Materials, Mechanical Resistance of the Roadways, Tests Static on Hydrocarbon Mixtures, Aggregates of Rubber.



go to top   Reciprocal Correlations in Fluid Flows
         by J. Wydrych, N. Szmolke

           Vol. 3. n. 5, pp. 1116-1128


Abstract - While fuel combustion in fluidized boilers, especially those of low power, underburnt fuel forms lumps and, in a consequence, the combustion process decays. Precise analysis of movement of the air-fuel mixture in the tested area should provide full information about fluidized burning. The paper presents assessment of aerodynamics in the space between tubes of the fluidized boiler. The assessment was done for different geometries and service conditions. The mixture movement was described with the VOF method and using the FLUENT program. The program allows to solve a system of equations of transport of mass and momentum completed with the equations of turbulence models. Numerical calculations were realized for different types of particles and different mass streams at the inlet to the system. The first stage of numerical tests included two-dimensional calculations. Analysis of the results allowed to determine higher resistances of flow at the bottom part of the tube insert in the tested velocity interval for all the tested materials. The results of numerical calculations were compared with the test results and cross correlations between the results obtained with both methods were determined. The paper presents methods of comparisons of both applied methods. From analysis of numerical and experimental results it appears that satisfactory conformity between them is not always obtained. Using the previously presented methods, the authors performed three-dimensional calculations for the same systems. Next, correlation was tested in a chosen section of the fluidized chamber and compared with the experimental results. A better correlation between the results was found for some parameters.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Small Fluid Boilers, PIV and CFD Correlation.



go to top   Modeling of Microstructural Evolution During the Hot Rolling of Aluminum Alloy
         by H. R. Rezaei Ashtiani, H. Bisadi, M. Adabjou

           Vol. 3. n. 5, pp. 1129-1136


Abstract - In this work, a numerical-based model has been proposed to calculate distributions of temperature, strain and inhomogeneity of effective strain through the strip thickness during hot rolling as well as the subsequent microstructural changes after hot rolling of an aluminum alloy. This study presents the application of the finite element method to simulation of microstructural mapping. To assess the hot rolling behavior of materials, finite element program DEFORMTM has been employed, here. These models include the effects of deformation temperature, applied strain (reduction), interface friction and cooling time on gradient of effective strain and inhomogeneity of static recrystallisation volume fraction. Results of simulation show that recrystalization will be increased by increasing of reduction (i.e. strain), temperature, and maintenance time duration after rolling. An important problem in modeling of microstructure is Microstructural gradient during thickness of rolled strip. Ingredient of this inhomogeneity has been investigated here, so that, simulation shows that strain and temperature inhomogeneity more effective rather than other impressive elements, on microstructural inhomogeneity.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Hot Rolling, Simulation, Microstructure, Effective Strain, Recrystalization, Temperature Distribution, Finite Element Method.



go to top   Simulation of Temperature Distribution Inhomogeneity in Aluminum Alloy During Hot Rolling
         by H. Bisadi, H. R. Rezaei Ashtiani, M. Bagheripoor, M. Alimardani

          Vol. 3. n. 5, pp. 1137-1144


Abstract - In hot rolling, a metal is given its final shape by thermo-plastically deforming the original stock. The formation of the temperature profile therefore has a complex history.
In this process, it is essential to know the temperature distribution within the strip along the thickness and length of the rolling part because temperature is the dominant parameter controlling the kinetics of metallurgical transformations and the flow stress of the rolled metal.
In other words, the microstructural changes and therefore the mechanical changes through thickness of strip during hot rolling depend on the temperature inhomogeneity within the metal being rolled. In this paper, a model for the study of hot rolling of aluminum alloys strip is proposed. To assess the rolling behavior of materials, finite element program Abaqus/Explicit has been employed and the hot rolling process was modeled in three dimensions. The temperature variation and the temperature inhomogeneity through thickness of strip during hot rolling process are predicted. The effects of various process parameters such as rolling speed, amount of thickness reduction, interface heat transfer coefficient and initial thickness of the strip is considered.

Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Hot Rolling, Temperature Inhomogeneity, Temperature Distribution, Finite Element Method.



go to top   A New Paradigm in Kinetic Modeling of Complex Reaction Systems
         by Vishal Hanumant Bhusare, Periyasamy Balasubramanian

          Vol. 3. n. 5, pp. 1145-1152


Abstract - We present a general kinetic model for first order irreversible elementary reactions sustaining in an ideal plug flow reactor/batch reactor. The time evolution of mole fraction of the products in a reactor is governed by a set of ordinary differential equations. A general analytical solution is derived using flow graph theory approach for the governing mole balance equations. The proposed kinetic model for the first order irreversible elementary reaction systems is demonstrated with illustrative examples.

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Keywords: Irreversible Reactions, Mass Action Kinetics, Flow Graph Theory.



go to top   NMR and Computational Study of Purine Nucleoside Phosphorylase Deficiency Markers
         by Hanna Krawczyk

          Vol. 3. n. 5, pp. 1153-1161


Abstract - The results of calculation of molecular structures of selected nucleoside in polar environment using Polarized Continuum Model of solvent combined with Density Functional Theory with a RB3LYP 6-311++g(2d,p) basis set is presented. The chemical schifts 13C NMR,  15N NMR and coupling constant J N-H of inosine, guanosine, deoxyinosine, deoxyguanosine and 2’,3’,5’-tri-O-acetyl -1-(2,4-dinitrophenyl)inosine  have been determined using  spectra and theoretical GIAO - DFT calculations (Gaussian 03W). 13C NMR and complementary 15N NMR spectroscopy are potentially powerful and convenient tools for diagnosing PNP.

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Keywords: PNP Markers, NMR, GIAO - DFT Calculations, PCM.



go to top   TUTORIAL: Three Dimensional Modelling and Simulation Aspects Related to Fuses for Power Semiconductors Protection
         by Adrian Plesca

          Vol. 3. n. 5, pp. 1162-1166


Abstract - Fuses incorporate one or more current-carrying elements, depending on their current ratings, and melting of these, followed by arcing, occurs when excessive overcurrents flow through them. They can be designed to safely interrupt the very highest fault currents that may be encountered in service, and, because of the rapidity of their operation in these circumstances, they limit the energy dissipated during fault periods. From power semiconductor devices’ overcurrent protection point of view special fuses were made, so called fast fuses. These kind of fuses have a distinct construction of the fuselinks because of their specific geometry. Taking into account the thermal phenomena complexity for a fuse it is very difficult to study the heating processes both in steady-state or transitory operating conditions, using the traditional analytical equations. During former work, because of limited computer capabilities, the authors had to concentrate on partial problems or on parts of the fuse geometry. The progress in computer technology enables the modelling and simulation of more and more complex structures in less time. It has therefore been the aim of this work to develop a 3D model of a complete fast fuse. The new thermal model has been included all the necessary components for a fast fuse such as outer caps, end tags, rivets, inner caps, ceramic body, fuselink elements and granular quartz. From the transient simulations results that for a good protection to overcurrents for power semiconductors, the normalised transient thermal impedance of the power semiconductor should be upper respect to the fuse one which has to protect it. Actually, there is a new criterion to select the fast fuses in order to protect the power semiconductors. Finally, using the 3D simulation software there is the possibility to get new solutions for a better protection of power semiconductor devices.

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