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International Review on Modelling and Simulations  Vol. 4 N. 5---- Part A

International Review on Modelling and Simulations  Vol. 4 N. 5---- Part B

International Review on Modelling and Simulations  Vol. 4 N. 5---- Part C

    International Review on Modelling and Simulations (Vol. 4 N. 5)  - October 2011 - Papers (Part A)

T-Connected Autotransformer Based AC-DC Converters for Power Quality Improvement Fault Detection and Reconfiguration of a Modular Multilevel Inverter Using Histogram Analysis and Neural Network Modeling and Control of Five-Level Three-Phase Flying Capacitors Inverter Cost-Effective Resonant Driving Method for High-Voltage CMOS Driver IC Single-Stage High-Power-Factor Electronic Ballast for Fluorescent Lamps Digital ΣΔ/PFM Controller Combined with IVFF Used for Synchronous Buck Converters Impact of Inverter Based Distributed Generation on Network Resonance and Harmonic Distortion Practical Medium Voltage Multi-Level Converter Topologies Comparison of Two EKF Based Observers Optimized Online by Both Simulated Annealing and Big Bang-Big Crunch Methods for Sensorless Estimations in Induction Motor Inter Turn Stator Winding Fault Estimation of Induction Generator by Wavelet Analysis Detection and Localization of Transformer Internal Fault during Impulse Test Rotor Resistance Estimation Methods for Performance Enhancement of Induction Motor Drives – A Survey A New Induction Motor Model for Fault Analysis Adaptive Selective Current Harmonic Cancellation Algorithm for PMBLDC Motor Drive Detection and Localization of Turn-to-turn Short Fault in Power Transformers by Analyzing of Transfer Function using an Artificial Neural Network Modeling of Multi-phase Transformer – Equivalent Circuit Design and Modelling of Multi-Pulse Phase-Shifting Transformers for Medium Voltage Applications A New Method for Stator Winding Turn-Fault Diagnosis of Induction Motor by Space Vector Model Based on Neural Network Modeling and Analysis of Saturated Induction Machines Using Multiple Scales Method and Chaos Theory for Detecting Route to Chaos in Chaotic Oscillations in Voltage Transformer with Nonlinear Core Loss Models Direct Torque Control of Two-Phase Induction Motors Fed by Two- and Three-leg Inverters Analysis of Commutation Torque Ripple of BLDC Motors and Presenting two Methods for its Reduction Furan Analysis on Power Transformers in Malaysia: a Field Investigation Design of Sample Based Filtering Schemes for a Three Phase Induction Motor Model An ANFIS-Based Neuro-Fuzzy Controller with Supervisory Learning for Speed Control of Brushless DC Motor Maximum Power Tracking of Wind Turbine Based on Doubly Fed Induction Generator Transient Finite Element Analysis of a Low Power Composite Solid Rotor Induction Motor An Excellent Technique for Hot Spot Temperature Reduction in 3 Phase Transformers Using Auxiliary Windings Online Energy Efficient Control of Three-Phase Induction Motor Drive Using PIC-Microcontroller Power Measurement for the AUFL Modelling of PEM Fuel Cell Systems using ANN

    International Review on Modelling and Simulations (Vol. 4 N. 5)  - October 2011 - Papers (Part B)

The Effect of Size of DG on Voltage Flicker and Voltage Sag in Closed-Loop Distribution System A Two-Stage Artificial Neural Network Classifier to Discriminate Three-Phase Unbalanced Voltage Sag Types Sinusoidal Voltage Flicker Elimination Using a New Control method for Series Active Filter Designing Passive Filters for Harmonic Reduction Based on Discrete Wavelet Transform Combined with Computational Methods Identification of Harmonic Source Location in Power Networks Using Neural Networks with Minimum Number of Measurement Electric Substation Ancillary Services Power Supply Using Fuel Cell Enhancement of Power Quality by Five Level Cascaded Control of Shunt Active Power Filter A Novel Approach to Power System Controller Design Influence of Automation Introduction to Power Distribution Systems on their Reliability FPGA-Based Real Time Simulation of ANFIS-MPPT Controller for Photovoltaic Systems Coordinated Control of TCSC and SVC for System Stability Enhancement Using ANFIS Method Optimal Placement of PMUs Solved by Mixed Integer Programming Load-Flow Analysis Using Hybrid Power-Current Injection Mismatches Optimal PV and FC Application in a Hybrid Power System with the Aim of Selling Electrical Energy to Distribution Network Bidding Strategy of Generating Companies in Simultaneous Energy and Spinning Reserve Markets Effects of Maximum Loading Ability and Minimum Voltage Source on Voltage Regulation by Using D-STATCOM The Application of a SVPWM STATCOM for Voltage Regulation in Wind Power Integration Using PMSG Based Wind Generation to Improve Inter-area Oscillations Damping in Power System Techno-Economic Evaluation of a Micro-Hydropower Plant for Rural Electrification in South Africa Using Clonal Selection Algorithm to Determine the Optimal Capacity and Place of DGs to Improve the Voltage Profile and Reduce the Loss Modeling and Simulation of Back Propagation Artificial Neural Network Based Smart Controller for Stand-alone Renewable Hybrid Energy System New Approach for LMP Calculation in Large Scale Power System Based on Network Incident Matrix Tuning of Power System Stabilizers in Multi-machine Systems Using Particle Swarm Optimization Fast Optimal Power Flow Using Linear Programming Applicable in Power System Planning Comparison of Voltage Stability by Optimal Location of TCSC and SVC Using Loss Sensitivity Method under Line Outages Application of Matlab/Simulink for the Analysis of Multi-Machine Transient Stability of a Power System Impacts of Reducing Short Circuit Current Level on Circuit Breakers Transient Studies An Intelligent Diagnostic System for Condition Monitoring of Ageing Glass Insulators Simultaneous Effect of Temperature and Site Altitude on Generators Output Simulation-Based Criteria for the Power Sizing of Grid-Connected PV Systems Determination of Resistance to Earth for Rod Grounding by Use of a Finite Element Method – Application to Benin Grounding System

    International Review on Modelling and Simulations (Vol. 4 N. 5)  - October 2011 - Papers (Part C)

Using Fuzzy Method for Tradeoff Management between Exploration and Exploitation in Multi-agent Systems An Energy Cost Minimization Algorithm for Wind Turbine System Design Modeling the Mechanisms of the Processes Optical Pumping in Dyes Lasers Optimal Determination of Financial Transmission Rights for Presenting in Primary Auction with Considering the Energy Market Conditions Modeling and Design of Patient-Electrodes Isolator for Bioimpedance Measurement Modeling Pilgrims Movement using GPS and GSM Notification A Novel Fault Location Algorithm for Multi-Tapped Transmission Lines Using Local Measurement A High-Speed Relay for Integrated Fault-Identification and Zone-Classification in EHV Transmission Lines A New Method for Classification of Different Types of Ferroresonant Oscillations Modes Investigation of Buckling Behaviors of Graphene Sheets via Molecular Mechanics Method A New Procedure for Solving the Shortest Superstring Problem, Using the Memetic Algorithm Evaluation of the Performance Study of Solar Air Collector by Using Bond Graph Approach A Hybrid Method of Memetic Algorithm and Artificial Immune System for Solving RCPSP A System for Adaptive Intelligent Learning (SAIL) The Modelling of Hybrid Surge Protection Circuit with Effect of Adding a Filter Fuzzy-Based Active Force with Computed Torque Control of 3-RRR Parallel Robotic Manipulator Prandtl and Hartmann Numbers Effects on Entropy Generation in Natural Convection A Robust Closed-Form Solution of Nonlinear Heat Transfer Equations A Hybrid Power Series – Artificial Bee Colony to Solve Magnetohydrodynamic Viscous Flow over a Nonlinear Permeable Shrinking Sheet The Variable Porosity Effect on the Natural Convection in a non-Darcy Porous Media New Study of the Propagation of a Quasi-TEM Wave by the Finite Elements Method Hydrodynamic and Thermal Characteristics of Conjugate Heat Transfer in an Annular Finned Duct One Model of Vertical Armature Construction inside Concrete Foundation and Ring Electrodes as Pillar Grounding System A Thermo-Elasto-Plastic Model for Cemented Soils under Unsaturated Condition A Conceptual Framework for Collaborative Design Process 2D-FEM Simulation of the Effects of Welding Current, Sequence and Geometry on Residual Stresses in Dissimilar Joints

   T-Connected Autotransformer Based AC-DC Converters for Power Quality Improvement
         by R. Abdollahi, A. Jalilian

          Vol. 4. n. 5, pp. 2047-2056

Abstract - This paper presents the design and analysis of T-Connected autotransformer based ac-dc converters which supplies a direct torque controlled motor drive (DTCIMD) in order to improve power quality conditions at the point of common coupling. The 28-pulse rectified output voltage is accomplished via two paralleled eighteen-pulse ac-dc converters each of them consisting of seven-phase diode bridge rectifiers and the 36-pulse rectified output voltage is accomplished via two paralleled eighteen-pulse ac-dc converters each of them consisting of nine-phase diode bridge rectifiers. A T-connected autotransformer is designed to supply the rectifiers. This autotransformer makes use of only two single-phase transformers, resulting in reduced volume, weight, and the cost of the drive as compared with polygon structure. The design procedure of magnetics is in a way such that makes it suitable for retrofit applications where a six-pulse diode bridge rectifier is being utilized. The aforementioned structure improves power quality criteria at ac mains and makes them consistent with the IEEE-519 standard requirements for varying loads. Furthermore, near unity power factor is obtained for a wide range of DTCIMD load operation. A comparison is made between 6-pulse, 28-pulse, and 36-pulse converters from view point of power quality indices. Results show that the THD of input current is less than 5% for the 28-pulse topology and less than 4% for the 36-pulse topology at variable loads.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: AC–DC Converter, T-Connected Autotransformer, Power Quality, 28-pulse, 36-pulse, Direct Torque Controlled Motor Drives (DTCIMD’s).

   Fault Detection and Reconfiguration of a Modular Multilevel Inverter Using Histogram Analysis and Neural Network
         by S. Sedghi, A. Dastfan, A. Ahmadyfard

         Vol. 4. n. 5, pp. 2057-2065

Abstract - In this paper a fault-tolerant algorithm for operation of a cascade H-bridge multilevel inverter (MLI) under faulty condition is proposed. The MLI has many switches that increase the probability of fault events. The faulty condition may lead to expensive downtime in the operation. Therefore by using the fault tolerant strategy the reliability of the system operation can be increased. In this paper a level-shifted (LS-PWM) method is proposed that uses rotating carrier waveforms to balance switching pattern in all cells, at all modulation indices. This method does not have adverse effect on voltage harmonic distortion. Next a fault detection and reconfiguration method is proposed for a modular MLI by using the output phase voltages. The histogram analysis is used for feature extraction and these features have been used as input to the Neural Networks (NNs). After fault detection by the NNs the faulty cell is bypassed and a reconfiguration method for this modulation strategy is used that guaranty continuous working. Simulation results are given for a cascade 7-level inverter at different modulation indices. These results show that the proposed diagnosis method is accurate for detection of fault types and their locations. This method works correctly under noisy condition and the classification performance for the noise with variance up to 1500 is 100%. The proposed method is faster and less complicated because of using histogram analysis instead of using sophisticated methods such as FFT or wavelet.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Modular Multilevel Inverter (MLI), Multilevel Carrier Based PWM, Fault Detection, Voltage Histogram, Reconfiguration.

   Modeling and Control of Five-Level Three-Phase Flying Capacitors Inverter
         by O. Bouhali, N. Rizoug, A. Talha

         Vol. 4. n. 5, pp. 2066-2073

Abstract - In this paper, a simple direct modulation strategy that enables to copy directly modulated waveforms onto output voltages of a five-level three-phase flying capacitor inverter is presented. The obtained modelling shows that the modulated multilevel voltage is obtained by combination of eight different three-level functions, which are called modulation functions. Therefore, a space vector modulation without using a Park’s transform is explained. Based on this algorithm, the location of the reference voltage vector can be easily determined. Then, the voltage vectors are selected to generate corresponding levels and simultaneously their durations are calculated. Simulation results for a five-level three-phase flying capacitors inverter are presented to verify the performance of the proposed space vector modulation.
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Keywords: Converter control, Direct modulation strategies, Vector control, Five level inverters, Flying Capacitors Inverters.

   Cost-Effective Resonant Driving Method for High-Voltage CMOS Driver IC
         by Hyun-Lark Do

         Vol. 4. n. 5, pp. 2074-2080

Abstract - panel (PDP) is proposed. It utilizes a cost-effective resonant circuit to reduce the voltage across the data drive IC when its output stages change their status. The resonant circuit reduces the power consumption and relieves the thermal problems of the drive ICs. Moreover, it has load adaptive characteristic (LAC). Then, low efficiency problem at light load does not exist. Compared to the conventional LC resonant driving method, the component count is significantly reduced. Experimental results obtained on a 42 inch HD PDP with the resolution of 1024 X 768 are discussed. 
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Energy Recovery, CMOS IC, LC Resonance.

   Single-Stage High-Power-Factor Electronic Ballast for Fluorescent Lamps
         by Hyun-Lark Do

         Vol. 4. n. 5, pp. 2081-2087

Abstract - A Single-stage high-power-factor electronic ballast for fluorescent lamps is proposed. The ballast offers a high power factor and a high-frequency voltage to the lamp. It is obtained by combining a power factor correction stage and an inverter stage based on the half-bridge topology. A saturable transformer constituting the self-oscillating drive limits the lamp current and dominates the switching frequency of the ballast. The proposed ballast has high energy efficiency, low cost, and high reliability compared to the conventional electronic ballasts. Experimental results obtained on a 30W fluorescent lamp are discussed.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Single-Stage, Power Factor, Electronic Ballast.

   Digital ΣΔ/PFM Controller Combined with IVFF Used for Synchronous Buck Converters
         by H. Pakniat, B. Abdi, J. S. Moghani

         Vol. 4. n. 5, pp. 2088-2094

Abstract - A digital sigma-delta/ pulse frequency modulation (ΣΔ/PFM) controller is presented to control a synchronous buck dc-dc converter over wide range of load currents and input voltages. Input voltage feed forward (IVFF) is also used to improve the dynamic response of converter. For light loads, the controller automatically switches to PFM mode and reduces effective switching to increase overall efficiency. In PFM controller, synchronous operation was done without the need of inductor current sensing. For moderate and high loads, controller selects the ΣΔ mode which prepares an excellent output voltage regulation with a spur-free output voltage spectrum. The mode transition criterion is programmable and makes more flexibility for efficiency improvement. Simulation results of MATLAB and SIMULINK confirm the validity of proposed controller for synchronous buck DC-DC convertor with 1.3 V output, 0-10A load current and 5-12 V input. The simulation results also predict that ΣΔC significantly improves the efficiency of converter in contrast to a PWM controller over a wide range of load current.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  ΣΔ, PFM, Feed forward, Synchronous Buck.

  Impact of Inverter Based Distributed Generation on Network Resonance and Harmonic Distortion
           by A. F. A. Kadir, A. Mohamed, H. Shareef, M. Z. C. Wanik

           Vol. 4. n. 5, pp. 2095-2101

Abstract - Most of the distributed generation (DG) systems utilise power electronic converters for interfacing with the grid. Increasing the number of power electronic devices, including DG with electronic converters, in the network has contributed to a harmonic problem. Although the integration of a passive filter within inverter based DG units can reduce the harmonic distortion, they also have a negative effect due to the resonance phenomenon. Thus, this paper aims to analyse the impact of inverter based DG on resonance and harmonic distortion. The analysis was performed for an inverter based DG system connected to the IEEE 13 bus distribution test system. To investigate resonance phenomenon, frequency scan was conducted while the fast Fourier transform analysis was carried out to measure the voltage and current distortion at the point of the common coupling and the DG connected bus. The test system was simulated using MATLAB/SimPowerSystems, and the results show that there can be resonance phenomenon and harmonic distortion due to the interaction of the inverter based DG and grid impedance. Moreover, the results also indicate that the maximum permissible penetration level of inverter based DG in the tested distribution system is 40% of total load. This study might be useful for utilities to plan the integration of DG units in the distribution system to avoid the resonance phenomenon and harmonic distortion.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Distributed Generation, Harmonic, Resonance, Inverter, Passive Filter.

  Practical Medium Voltage Multi-Level Converter Topologies
           by Fazel Seyed Saeed

           Vol. 4. n. 5, pp. 2102-2110

Abstract - Multi-Level Voltage Source Converters (ML VSCs) have been introduced and studied extensively for high-power applications in the recent literature. Due to their higher output voltage levels with a limited maximum device rating, better harmonic spectrum and less motor winding insulation stresses, these converters are considered as the best choice in medium voltage (MV) applications. Recent improvments in power semiconductor technology indicate a trade-off in the selection of these devices in terms of their switching frequency and voltage sustaining capability. Standard drives have become available since the mid-1980s for medium voltage industrial applications. This paper gives an overview about available medium voltage multi-level converter topologies based on state-of-the-art IGBTs and IGCTs. Furthermore, recent technological advances and their applications in industry are discussed.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  medium voltage, power semiconductor device, multi-level voltage source converter.

  Comparison of Two EKF Based Observers Optimized Online by Both Simulated Annealing and Big Bang-Big Crunch Methods for Sensorless Estimations in Induction Motor
           by M. Aydin, M. Gokasan, S. Bogosyan

           Vol. 4. n. 5, pp. 2111-2121

Abstract - In this study, it is discussed whether fast converged optimization methods should optimize online the covariance matrices of the Extended Kalman Filter (EKF) based algorithm used in estimating the stator current components, the rotor flux linkage components, the rotor speed and the load torque of Induction Motors(IM) for the sensorless vector control applications. If this scheme is possible, it will provide a solution approach for the sensitivity problem on parameter variations encountered while in estimation process; because the covariance matrices of system noises that are related with these variations will have been tuned online. At this point, speediness becomes restrictive feature on the choice of an appropriate optimization method because of the possible increase on computational load in each estimation sample. For this reason, the Big Bang – Big Crunch, to be the fastest heuristic optimization method, has been employed in determining the covariance matrices in the filter algorithm. Consequently, results from the simulation studies where BB-BC is compared with another heuristic optimization method, so called Simulated Annealing, distinguished that BB-BC is better with respect to convergence speed; however, in terms of reaching optimum solution while under parameter variations, none could perform promising estimation results.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Big Bang-Big Crunch, Induction Motor, Online Optimized Extended Kalman Filter, Simulated Annealing, Determination Of Noise Covariance Matrices.

   Inter Turn Stator Winding Fault Estimation of Induction Generator by Wavelet Analysis
         by E. Gharibreza, S. GH. Seifossadat, M. Joorabian, M. Heidari Orejloo

         Vol. 4. n. 5, pp. 2122-2128

Abstract - The most probable fault in induction generator is stator winding inter-turn fault. In the proposed method, Extended Park’s vector approach with the variance of the wavelet coefficients are used for detect of inter-turn fault. Also in this article Adaptive Neuro Fuzzy Inference System is used for estimation of the percentage of shorted turns in the phase under fault. Simulation studies are carried out for a induction generator to validate the proposed method. Results show high accuracy of proposed method in detection and estimation of number of shorted turns of stator winding under fault. the simulation results will show that the proposed method is very accurate.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Adaptive Neuro Fuzzy Inference System, Extended Park’s Vector Approach, Induction Generator, Inter-Turn Fault.

   Detection and Localization of Transformer Internal Fault during Impulse Test
         by J. Beiza, Mehdi Salaynaderi, N. Taghizadegan, A. A. Dadjouyan, J. Rabbaani

         Vol. 4. n. 5, pp. 2129-2137

Abstract - Incipient faults are low magnitude decaying transients lasting only for a few microseconds during impulse testing of transformers. They are very difficult faults to detect, even for experts, and they thus represent a problem because they can develop into major faults at later times. Thus detection and location of incipient faults are important. In this paper a methodology enabling detection and localization of such internal incipient faults is presented. Using wavelet transform analysis and the method developed, it is shown that the neutral current of the transformer winding resulting from impulse voltage tests provides important information for the detection and localization of an arc discharge as such an internal incipient fault.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Transformer, Impulse Test, Arc, Incipient Faults, Wavelet Transform Analysis.

   Rotor Resistance Estimation Methods for Performance Enhancement of Induction Motor Drives – A Survey
         by M. Nandhini Gayathri, S. Himavathi, R. Sankaran

         Vol. 4. n. 5, pp. 2138-2144

Abstract - While the 3-phase Induction Motor has been the conventional choice for drive applications over the years. It has presented certain problems from the control point of view. These are mainly lack of variable speed over wide range and lack of independent control of torque and speed. The advent of field oriented control along with advances in power electronics and online computational hardware has removed this disadvantage. Accordingly, high performance drives using plain cage induction motor have been successfully put into operation for many applications. One popular implementation of field oriented control is the indirect field orientation which depends on a sufficiently accurate mathematical model of the machine including parameter values. In this context, the variation of rotor resistance during the operational and environmental causes is an issue since maintaining the field orientation against detuning effects of rotor resistance variation is important. In view of this, estimation of rotor resistance has been a live area of research during the last decades. This review paper attempt to present important research outcomes in this topic for the benefit of researchers and professionals.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  High Performance Drives, Induction Motor, Scalar Control, Vector Control, Rotor Resistance, Rotor Flux, Reactive Power, Intelligent Methods.

   A New Induction Motor Model for Fault Analysis
         by F. J. Villalobos-Piña, R. Alvarez-Salas, N. Visairo, V. Cardenas

         Vol. 4. n. 5, pp. 2145-2152

Abstract - This paper presents a new three-phase induction motor model that allows to simulate four kinds of failures even simultaneously. The cases considered are rotor, stator, static eccentricity and bearing faults. The electric faults are modeled by means of parametric variations; the bearing failure is simulated through a friction function and the eccentricity fault is modeled using a function of mutual inductance. In spite of its simplicity, the model provides useful information for fault analysis. A validation procedure of the model is presented.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Induction Motor, Fault Analysis, ISP, Frequency Analysis, Simultaneous Faults.

   Adaptive Selective Current Harmonic Cancellation Algorithm for PMBLDC Motor Drive
         by V. M.Varatharaju, B. L.Mathur, K.Udhyakumar

         Vol. 4. n. 5, pp. 2153-2158

Abstract - An adaptive selective current harmonic cancellation (ASCHC) scheme for the permanent magnet brushless dc (PMBLDC) motor drive is presented in this paper. The proposed least mean square (LMS) adaptive filtering algorithm to eliminate selective line current harmonics is one among the methods of adaptive noise canceling in digital signal processing. The harmonic cancellation task is accomplished by generating reference signal with frequency that should be eliminated from the motor line current. The weights of adaptive filter are adjusted to totally eliminate the component with undesired frequency. In consequence, the proposed methodology also reduces the input current total harmonic distortion (THD). The triumph of the algorithm is validated by MATLAB/SIMULINK toolbox for simultaneous elimination of fifth and seventh harmonics in the drive line current.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Adaptive Selective Current Harmonic Cancellation (ASCHC), Current harmonics, LMS algorithm, BLDC Drive.

   Detection and Localization of Turn-to-turn Short Fault in Power Transformers by Analyzing of Transfer Function using an Artificial Neural Network
         by Vahid Rashtchi, Ebrahim Rahimpour

         Vol. 4. n. 5, pp. 2159-2163

Abstract - A new artificial neural network (ANN) technique is described in this paper to detect and localize turn-to-turn short fault in power transformers by analyzing of transfer function (TF). The ANN is trained by using back propagation learning algorithm. Frequency and amplitude of TF in resonance points are used as ANN inputs and fault location is used as an output. An especially designed double-disk transformer winding with power rating 1.2 MVA is used as a test object to verify the proposed method. All disks of this winding were accessible via a tap in order to form a variety of turn-to-turn short faults.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Transformer, Turn-to-Turn Short Fault, Fault Detection and Localization, Transfer Function (TF), Artificial Neural Network (ANN).

   Modeling of Multi-phase Transformer – Equivalent Circuit
         by Subhash Kumar Joshi, Hari Om Gupta, Pramod Agarwal

         Vol. 4. n. 5, pp. 2164-2171

Abstract - Single phase equivalent circuit of transformer has been identified as inadequate to analyze loading and operational behavior in multiphase transformer. Limitation of the single phase model to analyze effect of changes in parameters, caused by any deformity, has been brought out Equivalent circuit of most commonly used three phase delta-star topology, assuming linear loss free core, has been built and tested for validity for four different combinations. This concept has been used to analyze three phase Zig-Zag transformer, three phase to six phase topology proposed by April and differential fork, three phase to nine phase transformer proposed by Paice. Behaviour of Zig-Zag transformer in presence of unsymmetrical loading vis-a-vis harmonics has been analyzed to make a clear distinction between the two. The model of multiphase and multi-winding transformers, developed in this paper, enables determination of electrical quantities inside the transformer to facilitate diagnostics of transformer using operational data.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Transformer, Equivalent Circuit, Topology, Diagnostics, Physical Deformity.

   Design and Modelling of Multi-Pulse Phase-Shifting Transformers for Medium Voltage Applications
         by Fazel Seyed Saeed

         Vol. 4. n. 5, pp. 2172-2181

Abstract - The dc power supplies are generally made of rectifiers which inject harmonics into the utility grid. Increasing the pulse number of the rectifiers is attractive, since the ac input line current harmonics, and also the dc output voltage ripple decrease. This requires phase-shifting transformers with multi-windings as an interface between the rectifier and the utility supply. This paper introduces the detailed modelling methodology of the multi-pulse phase-shifting transformer. The presented procedure and concepts are applied for 24-pulse transformer. An elaborate simulation study is used to verify the proposed design.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Line current harmonics multi-pulse-rectifiers, phase-shifting-transformers, medium voltage.

   A New Method for Stator Winding Turn-Fault Diagnosis of Induction Motor by Space Vector Model Based on Neural Network        

          by Mehdi Samiei Sarkhanloo, Davar Ghalledar, Akbar Danandeh, Mohsen Ghorbani

          Vol. 4. n. 5, pp. 2182-2189
 

 Abstract - In this paper, first the space vector model of symmetric induction motor for the asymmetric mode due to the stator turn to turn fault will be developed and then a new scheme to diagnose this fault is introduced in which the neural network with pattern of space vector is used.. In this scheme, new indices will be defined by using properties of voltage and current space vectors of stator. the voltage and current unbalance make the oscillation in these indices. By appropriate training of the neural network, this scheme is able to properly diagnose the short circuit fault of the stator regardless of existence of the allowable unbalance in the input voltage, three-phase symmetrical voltage drop or overvoltage and the allowable variations in the load torque. Simulations are performed in Matlab/Simulink environment to validate the effectiveness of the proposed method.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Induction Motor, Inter-Turn Fault, Space Vector, Fault Diagnosis, Neural Network.

   Modeling and Analysis of Saturated Induction Machines
         by Ezzine Walid, Khlaifi Mohamed Larbi , Habib Rehaoulia

         Vol. 4. n. 5, pp. 2190-2194

Abstract - This paper presents a detailed analysis of saturated induction machine. Performance equations for this machine are given with utilize the main flux saturation. A new method to take into account magnetic saturation for asynchronous machine has been presented. The method avoids the cross-saturation between the direct and quadrature axis. Utilizing this procedure, a couple of mixed models are derived and presented. An application of a self- excited induction generator to prove the validity of the method.
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Keywords:  Induction Machines, Modeling, Cross Saturation.

   Using Multiple Scales Method and Chaos Theory for Detecting Route to Chaos in Chaotic Oscillations in Voltage Transformer with Nonlinear Core Loss Models
         by H. R. Abbasi, A. Gholami, S. H. Fathi, A. Abbasi

         Vol. 4. n. 5, pp. 2195-2210

Abstract - In this paper using multiple scales method chaotic behavior and types of fixed points in occurrence of ferroresonance in voltage transformer with considering a linear and two nonlinear core loss models is analyzed and investigated. It is proved that ferroresonance phenomenon in voltage transformers can be classified in chaotic dynamics systems. In this contribution chaos occurs in system from a sequence of period doubling bifurcation (PDB). This phenomenon includes different types of bifurcations such as period doubling bifurcation (PDB), saddle node bifurcation (SNB), hopf bifurcation (HB) and chaos. Analysis of dynamics of ferroresonant circuit is carried out using bifurcation theory. For this work bifurcation diagrams and phase plane diagrams are drawn using a continuation method for linear and nonlinear core loss models, lyapunov exponents are gained using multiple scales method and feigenbaum number are used. Bifurcation diagrams show with changing parameter of control and its increasing chaos occur in system. Border collision is shown in bifurcation diagrams.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Ferroresonance, Multiple Scales Method, Chaos Theory, Bifurcation, Lyapunov Exponents, Period Doubling, Feigenbaum Number.

   Direct Torque Control of Two-Phase Induction Motors Fed by Two- and Three-leg Inverters
         by S. Ziaeinejad, Y. Sangsefidi, A. Shoulaie

         Vol. 4. n. 5, pp. 2211-2218

Abstract - In this paper, direct torque control of two-phase induction motors fed by two- and three-leg inverters is analyzed. Essential equations for controlling electromagnetic torque and stator flux are presented and switching tables are derived. It’s demonstrated that basic method is unable to control the electromagnetic torque properly. The way of changing the switching table for improving torque control is presented. Simulation results, confirm the effectiveness of modified direct torque control of two-phase induction motors.
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Keywords:  Direct Torque Control, Modified Switching Table, Three-Leg Inverter, Two-Leg Inverter, Two-Phase Induction Motor.

   Analysis of Commutation Torque Ripple of BLDC Motors and Presenting two Methods for its Reduction
         by Y. Sangsefidi, S. Ziaeinejad, A. Shoulaie

      Vol. 4. n. 5, pp. 2219-2226

Abstract - This paper presents methods for analyzing and reducing commutation torque ripple of brushless DC (BLDC) motors in 120° elec. conduction mode. Due to voltage vector changes in every 60° elec. in BLDC drives, the current is commutated from one phase to another which results in electromagnetic torque fluctuations called commutation torque ripple. In this paper, commutation torque ripple in BLDC drives is analyzed and precise equations for calculating torque ripple are presented. Then, two methods based on modifying non-commutating and decaying phase voltages during commutation intervals for reducing commutation torque ripple are proposed. Two proposed methods are compared in terms of simplicity of implementation and value of torque ripple reduction. The presented torque ripple analysis and the proposed methods are validated by dynamic simulation of a 600W BLDC motor.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Brushless DC Motor (BLDCM), Commutation Torque Ripple Analysis, Commutation Torque Ripple Reduction, Current Ripple.

   Furan Analysis on Power Transformers in Malaysia: a Field Investigation
         by Zulkurnain Abdul-Malek, Nouruddeen Bashir, Hasree Ismail

         Vol. 4. n. 5, pp. 2227-2233

Abstract - The insulating materials (oil and cellulose paper) of power transformers undergo ageing during service. Thus condition monitoring of power transformers in service is very important. An established chemical test carried out on the transformer oil to determine the level of paper insulation deterioration in power transformers is the Furan Analysis. Numerous studies have been carried out to investigate transformer ageing in the laboratory, however, field investigations on full-scale or commercial power transformers using Furan Analysis are lacking. This paper reports an investigation on the concentration of 2-Furfuradehyde in oil samples collected from 414 power transformers of Tenaga Nasional Berhad (Malaysia national power company) transmission and distribution system. Statistical analysis of the Furfural data showed a trend in the furfural concentrations (FC) of the power transformers. Temporal variation showed older transformers had higher FC. Further analysis on case by case basis on six transformers revealed that FC correlated well with the level of transformer insulation deterioration and operating conditions. Frequency Dielectric Spectroscopy test carried out on some of the power transformers corroborated the above findings.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Ageing, Frequency Dielectric Spectroscopy, Furfural Analysis, Paper Insulation, Power Transformer.

   Design of Sample Based Filtering Schemes for a Three Phase Induction Motor Model
         by J.Ravikumar, S.Subramanian

         Vol. 4. n. 5, pp. 2234-2245

Abstract - There has been a great deal of research to employ various filtering methods and from the Bayesian filtering perspective, this paper aims to investigate the applicability of different sample based filtering schemes in the context of the state estimation problem of a three phase induction motor. The Standard Particle Filter (SIR-PF), Ensemble Kalman Filter (EnKF) and newer versions such as Particle Filter with Extended Kalman Filter (PF-EKF), Particle Filter with Unscented Kalman Filter (UPF), proposed in the literature within the particle filtering framework that accentuates the importance of proposal distribution to alleviate the risk of ensemble collapse is described and the error behaviour is analyzed through Monte Carlo simulations with regard to three scenarios Viz., low speed operation, step changes in load torque and reversal of speed. A quantitative evaluation of these algorithms and comparison of the Sum of Squares of the Estimation Error (SSEE), which is often used as the performance index that indicates the EnKF appears to be an efficient estimator with a reasonable time complexity amongst the different versions of PF. Given its performance, it can be concluded that EnKF should be preferred over the other approaches, virtually for the accuracy of the state vector estimation.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Ensemble Kalman Filter [EnKF], Particle Filter with EKF as Proposal Distribution [PF-EKF], Particle Filter with UKF as Proposal Distribution [UPF], Sampling Importance Re-sampling Particle Filter [SIR-PF], Bayesian State Estimation, Three Phase Induction motor [IM].

   An ANFIS-Based Neuro-Fuzzy Controller with Supervisory Learning for Speed Control of Brushless DC Motor
         by M. R. Mosavi, A. Rahmati, A. Khoshsaadat

         Vol. 4. n. 5, pp. 2246-2254

Abstract - Brushless DC (BLDC) motor is attracting much interest due to its high efficiency, high performance and ease of control for many applications. In this paper, a hybrid Neuro-Fuzzy Controller (NFC) based on Adaptive Network-based Fuzzy Inference System (ANFIS) architecture is presented for the speed control of BLDC motors to improve the control performance of the drive under transient and steady state conditions. To develop of drive's performance, instead of usual error back propagation (EBP) learning method, a fuzzy based online supervisory learning algorithm is used. This design leads to a controller with minimum structure and improved correctness and dynamic performance. System implementation is easy, since it requires minimum fuzzy rules as compared with the conventional fuzzy and/or neural networks, used for electrical drive applications. In order to demonstrate the controller ability to follow the reference speed and to reject undesired disturbances, its performance is simulated and compared with that of a conventional PID controller and other designs.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Speed, BLDC Motor, PID Controller, Adaptive Neuro-Fuzzy Controller, Supervisory.

   Maximum Power Tracking of Wind Turbine Based on Doubly Fed Induction Generator
         by M. Hilal, M. Benchagra, Y. Errami, M. Maaroufi, M. Ouassaid

         Vol. 4. n. 5, pp. 2255-2263

Abstract - This paper develops a new dynamic model of Doubly Fed Induction Generator DFIG driven by aerodynamic representation of wind turbine using PSCAD/EMTDC. The DFIG stator is directly coupled to Grid and his rotor is linked to Grid through a frequency converter permitting rotation at variable speed to extract maximum power from wind according to maximum power point tracking MPPT strategy. The frequency converter allows a bidirectional power flow, it is made of two collaborating static power converters associated by a DC-link. The converter firing pulses are generated according to vector control approach to decouple speed and reactive power control. According to desired speed, Rotor Side Converter RSC produces reference currents to be injected in the rotor windings, using Current Reference Pulse Width Modulation CRPWM. Grid side converter GSC regulates DC bus voltage level and power factor. The optimum tip speed ratio TSR is used to compute the rotor reference speed corresponding to maximum power. During the simulation, the model is subjected to a variable wind speed and a three phase short circuit to demonstrate its efficiency, the resulting curves testify of the model robustness and the control strategy effectiveness.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Wind Turbine, DFIG, MPPT, PFC, PSCAD/EMTDC, PWM, CRPWM, Tracking Curve.

   Transient Finite Element Analysis of a Low Power Composite Solid Rotor Induction Motor
           by Akbar Rezaie Sardarabadi, Mohsen Hosseini

           Vol. 4. n. 5, pp. 2264-2268

Abstract - In this paper, transient modeling of a low power induction motor with composite solid rotor is presented. Composite solid rotor induction motor has a solid rotor which is composed of two parts: ferromagnetic core and hollow conductive cylinder. By using two dimensional transient finite element analyses, the performance of the composite solid rotor induction motor is compared with traditional induction motor. Then, for the precision study of the composite solid rotor induction motor, three dimensional transient finite element analyses is also presented and compared with two dimensional results. Two and three dimensional finite element analysis results are relatively similar. Simulation results show that in low power, small size with a few pole numbers, the performance of the composite solid rotor induction motor is better than the performance of the traditional squirrel cage induction motor.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Composite Solid Rotor, Finite Element Analysis, Induction Motor, Transient, Three Dimensional, Two Dimensional.

   An Excellent Technique for Hot Spot Temperature Reduction in 3 Phase Transformers Using Auxiliary Windings
         by Diako Azizi, Ahmad Gholami, Diar Azizi

         Vol. 4. n. 5, pp. 2269-2277

Abstract - Transformers represent the largest portion of capital investment in transmission and distribution substations. In addition, transformer outages have a considerable economic impact on the operation of an electrical network.AC loss is one of the important parameters in transformers.
The AC losses in a transformer depend on the magnetic field.These losses of the transformer affecton the hot-spot temperature (HST) value directly. At the first step, energy (thermal) equation is solved until temperature is obtained. For numerical solution of above equation, finite element method is used. At the second step, a technique will be introduced in order to reduce the ac losses and consequently to reduce the HST. Thistechnique that usually adopted to mitigate the unwanted magnetic field is using a system of coilsthat produce a magnetic field opposite to the incident one, reducing the total magnetic field.The selected model for simulation is 3 phases, 10MVAtransformer.Inthis paper adding two auxiliary windings in each phase to the typical transformer to produce this oppositemagnetic field is proposed. The proper use of these auxiliary windings could reduce the leakageflux and, therefore, the AC loss. Also, thesimulation results show that employing auxiliary windings will improve the transformerefficiency.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Coil, Flux, Hot Spot, Temperature, Transformer.

   Online Energy Efficient Control of Three-Phase Induction Motor Drive Using PIC-Microcontroller
         by Hussein S. Sarhan

         Vol. 4. n. 5, pp. 2278-2284

Abstract - Online energy efficiency optimization of three-phase squirrel-cage induction motor drive operating at constant loads and variable frequencies according to the principle of constant Volt per Herts is investigated in this paper. A hybrid optimization controller using peripheral interface controller PIC to calculate the optimal value of modulation index m of inverter-based AC-to-AC energy converter for each operating point has been designed, simulated, and experimentally tested. The proposed optimization controller combines the characteristics of both search method and loss minimization method. The performance of optimized system was illustrated and compared with that of the original system. Simulation and experimental results showed that the efficiency of the optimized system was improved. Also, it was noticed that the hardness of mechanical characteristics of the drive system increased, which makes the system operation more stable.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Modeling and Simulation of Induction Motor, Energy Optimization, Peripheral Interface Controller, Search Control.

   Power Measurement for the AUFL
         by Rasha M. El Azab, E. H. Shehab Eldin, P.Lataire, M. M. Sallam

         Vol. 4. n. 5, pp. 2285-2290

Abstract - Under Frequency Load Shedding, UFLS, is the last step and the most extreme in protecting electric power systems from black outs and severe damages. Adaptive UFLS methods usually use df/dt measurement for sizing the degree of overloads. For so many reasons the measurement of df/dt may found to be unreliable. This paper presents an alternative method for sizing the overloads through the measurement of the generated active powers in the system, as a first step of an adaptive under frequency load shedding. Using the advantage of high speed wide area protection system, the generated powers in the system can be obtained easily. The simulation and experimental results show the validity of the suggested method, and demonstrate its advantages in calculating the system overloads.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Active Power Control, Adaptive under Frequency Load Shedding, Experimental Results, Frequency Behavior.

   Modelling of PEM Fuel Cell Systems using ANN
         by Inmaculada Zamora, José I. San Martín, José J. San Martín, Víctor Aperribay, Pablo Eguía

         Vol. 4. n. 5, pp. 2291-2298

Abstract - PEM fuel cells are nonlinear, multi-input and multi-output, time-varying, and strongly coupled systems that are hard to model via conventional methods. A suitable model is needed for PEM fuel cells to predict how they will behave under various operating conditions. Usually, modelling of fuel cell systems requires a good knowledge of the parameters involved in the processes that, in many cases, are difficult to determine. A solution to avoid this difficulty consists in using black-box models, such as those based on artificial neural networks (ANN). This paper presents the modelling of a PEM fuel cell system, using ANNs. The selected ANN structure has been validated for the transient state, during the start up of the system, and in steady state. Results are shown for a commercial PEM fuel cell system. The ANN model developed can be applied to any PEM fuel cell, applying the principle of similarity.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Fuel Cells, PEMFC, System Identification, Modelling, ANN.

   The Effect of Size of DG on Voltage Flicker and Voltage Sag in Closed-Loop Distribution System
         by Ali Saidian, Mehrdad Heidari, Davar Mirabbasi

         Vol. 4. n. 5, pp. 2299-2304

Abstract - Application of distributed generation (DG) in distribution system is expected to increase in the near future due to its positive impacts such as voltage support, improved reliability, small size and losses reduction. However DGs may have negative impacts on power quality, such as voltage regulation, harmonic distortion, islanding and confliction with relaying and reclosing. This paper investigates the effect of the Distributed Generation (DG) and its size on voltage flicker and voltage sag which is considered recently as an urgent power quality problem that can affect motor starting, temperature rise, overloading of generators, motors and may cause health risk problems due to the annoying light flicker which is consequence of voltage fluctuation. The effect of different sizes of DG on the voltage flicker and voltage sag in different buses of IEEE 34 buses meshed distribution system has been investigated. To support this argument, simulations are achieved on MATLAB/SIMULINK, where the results reveal the amount of effect of DG on voltage flicker and voltage sag for different types of buses of meshed distribution system.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Distributed Generation (DG), Meshed Distribution System, Voltage Sag, Voltage Flicker.

   A Two-Stage Artificial Neural Network Classifier to Discriminate Three-Phase Unbalanced Voltage Sag Types
         by Ali Deihimi, Abolfazl Momeni

         Vol. 4. n. 5, pp. 2305-2311

Abstract - This paper presents an efficient two-stage classifier based on artificial neural network (ANN) concept to discriminate different types of three-phase unbalanced voltage sags at the location of power quality monitoring. In the first stage, the general type of unbalanced voltage sag (C and D) in terms of number of phases undergoing voltage drop is detected. In the next stage, the symmetrical phase is identified. Different classification approaches such as six-phase (SP), symmetrical components (SC) and three-phase three-angle (TPTA) algorithms have been previously developed to characterize and discriminate six types of unbalanced voltage sags, but they are not fully reliable because of possible incorrect results reported. The proposed classifier is widely tested and compared with three aforementioned algorithms to validate its reliability and efficiency. It is concluded that the learning intelligence of the proposed classifier is its strong point to be superior to those classifiers exclusively employing mathematical operations.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Artificial Neural Network, Classification, Power Quality Monitoring, Three-Phase Unbalanced Voltage Sag.
 

   Sinusoidal Voltage Flicker Elimination Using a New Control method for Series Active Filter
         by Mahsa Khayyatzadeh, Behrouz Tousi

         Vol. 4. n. 5, pp. 2312-2316

Abstract - Electric arc furnace (EAF) is an unbalanced, nonlinear and time-variant load which is lead to power quality problems such as voltage flicker in power system. An electric arc furnace has caused the sinusoidal cyclic flicker in the point of common coupling (PCC) voltage in this paper. To mitigate the sinusoidal flicker of the PCC voltage (or smoothing the PCC voltage envelope) by a series active filter (SAF), a new simple method has been proposed that generates the required reference voltages to control the SAF for compensating the PCC voltage flicker. Unlike the control methods which have previously been presented, the structure of the presented method is simple and has no need to use the p-q and d-q theories in its structure and this is the major advantage of the proposed method. The studied power system has been simulated by the PSCAD/EMTDC software. The analysis, comparisons and the simulation results have shown that the presented control method has considerably smoothed the PCC voltage envelope.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Sinusoidal Cyclic Flicker, Electric Arc Furnace, Series Active Filter, Point of Common Coupling, Voltage Flicker.

   Designing Passive Filters for Harmonic Reduction Based on Discrete Wavelet Transform Combined with Computational Methods
         by Hamid Rahimi Esfahani, Farshad Kiyoumarsi

         Vol. 4. n. 5, pp. 2317-2323

Abstract - Regarding the increasing importance of power electronic devices application in industry and different harmonic problems, this research aims to present a new method based on signal processing through which passive filters for harmonic reduction is designed. In other words, a new method of designing passive filters for detection and harmonic analysis in power systems, based on wavelet transform is presented. Furthermore, among different harmonic sources, HVDC system, which has many applications in industry, is chosen. For harmonic modeling in the HVDC system, it is supposed that only 5th, 7th, 11th, 13th and 24t h (as a high order harmonic) harmonics exist. Finally, we show that the proposed method works better than traditional methods due to independence of determining quality factor in different passive filters and the capability of combining wavelet transform with computational methods. Results show that the DWT-based proposed method can significantly reduce harmonics in several steps through decomposing a signal into its components.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Multi-Resolution Decomposition, Passive Filter for Harmonic Reduction, Harmonic Detection, Discrete Wavelet Transform, HVDC System.

   Identification of Harmonic Source Location in Power Networks Using Neural Networks with Minimum Number of Measurement
         by R. Farajzadeh, J.Khodaei

         Vol. 4. n. 5, pp. 2324-2333

Abstract - This paper presents a practical method for harmonic sources detection in a power network using neural network with sigmoid output layer and LVQ education algorithm. In some cases, to improve results, a consecutive BPN network has been used that in this paper is called CBPN. For comparison, the RBF neural network has been studied and results comparison shows that BPN is better. For optimum selection of numbers and locations of harmonic meters, Optimum line that is affected from harmonic sources and also system topology analysis method has been used. The applications of mentioned methods lead to obtain satisfactory results with the least number of harmonic meter and neural network input samples. When neural network is applied to harmonic sources detection, there are no knowledge about the existence of harmonic sources and their type. Using the state estimation method and optimization method such as genetic algorithm which are applied for the locating meter are confirmed, but these methods are so complicated and time consuming. The presented method in this paper is simple and also very precise. Other advantage of this paper is the proper selection of the neural network input parameters so that load and harmonic sources variations do not affect on the result considerably. Presented Method is tested on the IEEE-14 BUS network.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Locating, Harmonic Sources, Measurement, BPN, Training Samples.

   Electric Substation Ancillary Services Power Supply Using Fuel Cell
           by Constantin Barbulescu, Stefan Kilyeni, Gheorghe Vuc, Ioan Borlea

           Vol. 4. n. 5, pp. 2334-2341

Abstract - Ancillary services are support services within the power system, those which are necessary to support the transmission capacity and are essential in maintaining power quality, reliability and security of the grid. Considering these facts the supply method of the ancillary services is a key feature for the appropriate operation of the power system. Within this paper the authors are focusing on electric substation ancillary services. The paper addresses the issue of supplying them using unconventional energy sources, such as fuel cells. A critical analysis of the substation ancillary services power supply is performed. Several supply solutions are proposed, using normal and backup sources. The case study refers to a real substation from the Romanian Power System. The optimal solution using fuel cell for the substation ancillary services supplying is presented.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Substation, Ancillary Services, Power Supply, Unconventional Energy Source, Fuel Cell.

   Enhancement of Power Quality by Five Level Cascaded Control of Shunt Active Power Filter
         by C. B. Venkatramanan, K. S. Jayakumar

         Vol. 4. n. 5, pp. 2342-2347
        

Abstract - The Shunt Active Power Filter (SAPF) is one of the key controllers in Flexible Alternating Current Transmission System (FACTS) to control the transmission line voltage and can be used in Power System (PS) to enhance the power quality. This paper studies an investigation of Cascaded Five-Level Inverter (CFLI) is used in a SAPF in PS. Making use of the CFLI has benefits of low harmonics distortion, reduced number of switches and switching losses. In order to compensate the reactive power, balance the capacitor DC voltage and suppress the total harmonics distortion (THD) drawn from a Non-Linear Diode Rectifier Load (NLDRL) of SAPF, Sub-Harmonics Pulse Width Modulation (SHPWM) technique, Proportional and Integral (PI) controller and D-Q reference frame theory are proposed in this paper. The SHPWM pattern generation is used as control for the switches of CFLI. The D-Q reference frame theory is used to calculate the reference compensating currents for SAPF and PI controller is used for capacitors dc voltage regulation for SAPF. The results are validated through MatLab/Simulink simulation software with SAPF and without SAPF.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Power System, Shunt Active Power Filter, SHPWM, PI controller, D-Q theory.

   A Novel Approach to Power System Controller Design
         by Aliakbar Mohammadi

         Vol. 4. n. 5, pp. 2348-2354

Abstract -The paper discusses an innovative state estimation and design of controller method for nonlinear power systems. The method uses a nonlinear differential equation solution approach called modal series which is very favourable for modelling of nonlinear systems. Modal series preserves many nonlinear dynamics of system which may be lost in the linearizing process. We apply modified linear controller design schemes to modal series model of a power system. It is investigated that a better performance achieves since our approach uses a more accurate model for the nonlinear system. Using modal series model of a nonlinear power system, we also present an LQG (Linear Quadratic Gaussian) controller design scheme for power systems. We arrange several simulations in order to evaluate the results of what argued in this paper.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  State Estimation, LQG Controller, Modal Series, Power System.

   Influence of Automation Introduction to Power Distribution Systems on their Reliability
         by A. Benouareth, H. Meglouli

         Vol. 4. n. 5, pp. 2355-2360

Abstract - The aim of this paper is to show the impact of automation introduction to power distribution systems on reliability indices of the system and the customer. It provides an analytical technique, generally employed for quantitative evaluations, and shows the influence of SCADA systems installation to control power distribution systems in order to improve their reliability. The results show clearly the improvements on reliability as the automation of lines switches is increased.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Automation, Reliability, Power, Distribution Systems, SCADA, Line Switches.

   FPGA-Based Real Time Simulation of ANFIS-MPPT Controller for Photovoltaic Systems
         by F. Chekired, C. Larbes, A. Mellit

         Vol. 4. n. 5, pp. 2361-2366

Abstract - Real time simulation of an intelligent MPPT controller for photovoltaic systems is presented in the present paper. The presented MPPT is based on the using of an Adaptive Neuro-Fuzzy Inference System (ANFIS) controller. This controller is designed and implemented on a Xilinx (Virtex-IIV2MB1000) reconfigurable Field Programmable Gate Array (FPGA) using Hardware Description Language (VHDL). Implemented controller has been simulated and tested under constant and rapid variation of atmospheric conditions. Results show that the ANFIS controller performs well in the viewpoint efficiency, response time and stability.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Photovoltaic, MPPT, ANFIS, FPGA, Control, Real-Time Simulation.

   Coordinated Control of TCSC and SVC for System Stability Enhancement Using ANFIS Method
         by Ghazanfar Shahgholian, Amir Movahedi

         Vol. 4. n. 5, pp. 2367-2375

Abstract - Flexible ac transmission systems (FACTS) are used to strengthen controllability and to improve the transmission capacity of networks, application and utilization of controllers and power electronic devices. Thyristor controlled series capacitor (TCSC) and static var compensator (SVC) are used in this paper to increase damping and stability of the power system. This study applies adaptive Neuro-fuzzy inference system (ANFIS)-based TCSC and SVC controllers for damping oscillations. ANFIS which tunes the fuzzy inference system with a back propagation algorithm based on collection of input-output data makes fuzzy system to learn ANFIS controller is designed to damp out the low frequency local and inter-area oscillations of the multi-machine power system. The parameters of the system are optimized by ANFIS model and therefore, the damping and stability of the system improve. The designed controller is used in a wide range of operational conditions in a multi-machine power system. Analysis of the simulation results shows that the proposed controller can improve successfully damping and stability of the power system and therefore, the transmission power increases.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  TCSC, SVC, Coordinated Control, ANFIS, Damping, Oscillations.

   Optimal Placement of PMUs Solved by Mixed Integer Programming
         by E. Dahri, G. R. Yousefi, M. M. Pedram, S. M. Ezzati, H. Vahedi

         Vol. 4. n. 5, pp. 2376-2381

Abstract - This paper shows the optimum PMUs (Phasor Measurement Unit) placement for full observation of the power system considering minimum number of PMUs. This paper compares Mixed Integer Programming (MIP) with Mixed Integer Bacterial Foraging Algorithm (MIBFA) and other algorithms. In this paper IEEE 30-57 bus and Tehran 41bus regional electric power network are used as test systems and results show good efficient of purpose programming.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Phasor Measurement Unit (PMU), Power System Observation and Mixed Integer Programming.

   Load-Flow Analysis Using Hybrid Power-Current Injection Mismatches
         by Mamdouh Abdel-Akher, Salah Kamel, Mohamed K. Elnemr

         Vol. 4. n. 5, pp. 2382-2391

Abstract - This paper proposes a direct implementation for voltage and power control devices in the Newton-Raphson (NR) power flow method using hybrid current-power mismatches formulation. This is a new technique for load flow which overcomes the disadvantage of the NR current injection method when the voltage controlled nodes exist. The mismatch equations at voltage controlled nodes are represented by power mismatches rather than current mismatches. In addition, Flexible AC transmission devices (FACTs) are also implemented without modification in the hybrid load flow Jacobian matrix. The STATCOM is represented by a generator bus in terms of power mismatches. The SSSC and UPFC are modeled by series impedance and two current injections at their corresponding nodes. In the case of UPFC, additional power injection equation is included at the sending end node to represent the voltage controlled node. The proposed hybrid mismatches power-flow model reduces the complexities of the computer program codes and enhance the reusability by avoiding modifications in the Jacobian matrix. Results computed using the IEEE data exhibits robust convergence characteristics and superior performance over existing Newton-Raphson power-flow alternatives.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Load Flow Analysis, Newton-Raphson Method, Current Injection Method and Facts.
 

   Optimal PV and FC Application in a Hybrid Power System with the Aim of Selling Electrical Energy to Distribution Network
         by S. Arabi Nowdeh, B. Tousi, A. A. Zoraghchian, M. Hajibeigy

         Vol. 4. n. 5, pp. 2392-2401

Abstract - In this paper, a hybrid system with single ownership with the aim of selling electrical energy to distribution network is presented which consists of photovoltaic (PV) module and PEM (proton exchange membrane) fuel cell (FC). Since studies in optimal application between FC and PV with power electronic view aimed at load provision. In this paper (moreover load provision), the application between PEMFC and PV is considered with the aim of maximizing profit gained due to selling electrical energy to the distribution network. The revenue from selling electrical energy is considered as the system profit. Also, the sold power to the network is difference between FC power and load power demand. We have done optimization to maximize the system profit gained by selling electrical energy to the distribution network using GAMS software. Also Hourly optimal amount of sold electrical energy to the network due to changes in solar radiation and electrical energy price, the optimal amount of PEMFC hydrogen consumption and stored hydrogen in the tank are determined. Then the effect of effective parameters of PEMFC and PV on system profit is investigated. The results of optimization prove this claim that moreover providing load, electrical energy can also be sold by proposed hybrid system.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Photovoltaic, Fuel Cell, Optimal Application, Distribution Network, GAMS.

   Bidding Strategy of Generating Companies in Simultaneous Energy and Spinning Reserve Markets
         by Amin Karimi Zadeh, Mohammad Taghi Ameli, Arash Ehsani

         Vol. 4. n. 5, pp. 2402-2409

Abstract - This paper presents a novel method to simulate producers’ behavior in the energy and spinning reserve markets in order to make good strategic bids. Nash theory is used for this purpose and that Producers’ marginal cost is multiplied by strategic coefficients to make the strategic bids that producers can offer to the energy market. Because of clearing the spinning reserve and energy markets simultaneously, producers should offer their spinning reserve and energy bids to the market simultaneously. A participation factor is defined that can be used to withhold a proportion of the generators’ capacity in order to participate in the spinning reserve market only. The offered price for spinning reserve is another decision variable that should be determined by producers in order to making good offer in the spinning reserve market. The Genetic Algorithm and particle Swarm optimization (PSO) Algorithm have been combined to solve this optimization problem. Transmission constraints have been considered by using DC optimal power flow (DCOPF) in the proposed algorithm. The Western System Coordinating Council (WSCC) nine bus test system is employed to illustrate and verify the results of the proposed method.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Bidding Strategy, Strategic Coefficients, Nash Equilibrium, DCOPF, Genetic Algorithm, Particle Swarm Optimization.

   Effects of Maximum Loading Ability and Minimum Voltage Source on Voltage Regulation by Using D-STATCOM
         by Kittaya Somsai, Nitus Voraphonpiput, Thanatchai Kulworawanichpong

         Vol. 4. n. 5, pp. 2410-2416

Abstract - This paper presents the steady state performance of a D-STATCOM applied for load voltage regulation by injecting only reactive power into the system. This study begins with determining dynamic equations of the distribution system with the installed D-STATCOM. The dynamic equations are determined with reference to the synchronous rotating dq reference frame transformation theory. Then, the steady state equations are derived from the dynamic equations. The amount of apparent power of D-STATCOM for load voltage regulation in both increased load power and decreased source voltage are considered and compared. Additionally, the maximum load power and minimum source voltage that can regulate the load voltage magnitude without injecting any active power into the system are also determined.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  D-STATCOM, Load Voltage Regulation, Voltage Sag, Maximum Loading Effect, Minimum Voltage Source Effect.

   The Application of a SVPWM STATCOM for Voltage Regulation in Wind Power Integration
         by W. Z. Chan, V. K. Ramachandaramurthy

         Vol. 4. n. 5, pp. 2417-2424

Abstract - Due to global warming, the importance of the environmentally friendly method of converting wind power into useful energy has increased significantly. Studies over the years have made the integration of wind farms into electrical networks feasible today. However, due to the fluctuating nature of the wind, voltage variation at the interconnection of wind farms continues to be a problem. This paper aims to study the viability of a STATCOM in providing reactive power compensation, and in turn voltage regulation at the interconnection of wind farms. The proposed technique uses space vector PWM (SVPWM) modulation strategy which has lower switching losses, higher output voltage for the same dc-bus voltage, and better harmonic performance compared to the sinusoidal PWM (SPWM) technique. Results show that the proposed technique provides voltage regulation and fault ride through capability for the voltage at the point of common coupling.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  STATCOM, SVPWM, voltage regulation, fault ride through capability, wind power.

   Using PMSG Based Wind Generation to Improve Inter-area Oscillations Damping in Power System
         by Iman Pourfar, Heidar Ali Shayanfar, Hasan Modir Shanechi, Ali Hesami Naghshbandy

         Vol. 4. n. 5, pp. 2425-2433

Abstract - This paper investigates the use of wind farms equipped with direct- derive permanent magnet synchronous generators (PMSG-WTs) to damp inter-area oscillations in power systems with high wind power penetration. For this purpose this work addresses the use of a supplementary control loop to be added to the conventional vector control system of PMSG-WTs. The performance of the supplementary damping control loop is evaluated, employing modal analysis and time domain simulations on a two area power system test case.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Wind Turbine, Permanent Magnet Synchronous Generator, Inter-Area Oscillation .

   Techno-Economic Evaluation of a Micro-Hydropower Plant for Rural Electrification in South Africa
         by K. Kusakana, J.L. Munda, A.A. Jimoh, B.B. Monchusi

         Vol. 4. n. 5, pp. 2434-2446

Abstract - This study investigated the techno-economic viability of micro-hydropower generation in the electrification of a rural area in KwaZulu-Natal, South Africa. The proposed scheme is composed of a squirrel cage induction machine running as a generator and directly coupled to a Kaplan hydro-turbine. Mathematical models were developed and simulations performed using MATLAB/SIMULINK software to highlight the characteristics of the output power supplied to consumers for varying water flow rate. A small-scale experimental model based on a DC machine as a turbine driving a self-excited induction generator was developed to validate the designed model. Economic and environment analyses were performed using HOMER software to assess the possibility of using the proposed stand-alone micro-hydropower system for low-cost electricity production and supply for the specific site. The MATLAB/SIMULINK model developed and the laboratory experiments demonstrated the technical viability of using a Kaplan turbine and a self-excited induction generator in micro-hydropower generation. The economic and environmental results highlight the cost-effectiveness character and the reduction of gas pollutant emissions achieved by the plant. The micro-hydropower plant is a technically and economically viable and environmentally friendly means for rural electrification. 
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Micro-Hydropower, Rural Power Supply, Techno-Economic Analysis.

   Using Clonal Selection Algorithm to Determine the Optimal Capacity and Place of DGs to Improve the Voltage Profile and Reduce the Loss
           by H. Piarehzadeh, A. Khanjanzadeh, R. Pejmanfar, A. Pahlavanhoseini

           Vol. 4. n. 5, pp. 2447-2453

Abstract - The purpose of this paper is minimizing line losses and improving voltage profile by DG allocation based on CSA (Clonal Selection Algorithm).The increasing need of electricity and establishing powerhouses, as well as spending a great amount of time to build powerhouses, indicates the necessity of distributed generation in small size and close to the consumer location. Determining the optimum location and capacity of DG resources is an important consideration in obtaining the maximum efficiency. DGs' optimal place and size can be determined according to different parameters and through different methods In this paper, selecting a part of Tehran network, attempts to investigate the effects of distributed generation on line losses and voltage profile and to consider optional place and sizing to losses reducing.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Clonal Selection Algorithm, DG Optimal Location and Size, Voltage Profile Improvement, Loss Reduction, Distributed Generation.

   Modeling and Simulation of Back Propagation Artificial Neural Network Based Smart Controller for
Stand-alone Renewable Hybrid Energy System
         by Kumaravel S., Ashok S.

         Vol. 4. n. 5, pp. 2454-2461

Abstract - Wind and photovoltaic power generation are two of the most promising renewable energy technologies for stand-alone applications. Harvesting maximum power from intermittent nature of renewable sources is a difficult task, when the load is asymmetrical in nature. This leads a necessity of an intelligent controller. ANN based smart controller for solar-PV/wind/battery Hybrid Energy System (HES) is discussed in this paper. Modeling and dynamic simulation of the HES is developed in MATLAB/Simulink platform and developed model is validated with the experimental results obtained from lab scale model installed at National Institute of Technology Calicut(NITC) campus. ANN based smart controller is incorporated to harvest maximum power from solar-PV and wind sources. Loads are considered according to priority such as primary, deferrable and dump loads. Simulation studies have been carried out to verify the system performance under different scenarios using practical load profile and renewable potential data obtained from the monitoring station installed at NITC campus.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Hybrid Energy System, Solar Photovoltaic, Wind Energy, Renewable Energy, Smart Control, ANN Controller.

   New Approach for LMP Calculation in Large Scale Power System Based on Network Incident Matrix
         by M. S. Javadi, A. Javadinasab, A. Shishebori3, H. Basri, R. Azami

         Vol. 4. n. 5, pp. 2462-2469

Abstract - Locational Marginal Price (LMP) is one of the techno-economical indices in modern restructured power system. This paper represents the new approach to modeling large scale power system considering multi transmission lines per corridor and also, multi-generation units located at generation buses of power system. This approach is based on graph theory and incorporates an identical incidence matrix of the grid. Based on this methodology, system operator and planning entity could easily establish and operate the power system in an optimal manner. Incorporating a strong and flexible clearing market tool is one of the recent challenges in large scale power system. To overcome this challenge, we present an analytical approach based on graph theory in modeling the network and utilizing linear programming software in LMP calculation. One of the strongest features of this method is to reducing the computational memory needs and increasing the speed of reaching the optimal answers by implementing sparsity techniques.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Locational Marginal Price, Incidence Matrix, Modern Restructured Power System.

   Tuning of Power System Stabilizers in Multi-machine Systems Using Particle Swarm Optimization
         by G.Naresh, M.Ramalinga Raju, S.V.L.Narasimham, K.Ravindra

         Vol. 4. n. 5, pp. 2470-2479

Abstract - Power system stabilizers (PSSs) are used to generate supplementary control signals for the excitation system to damp electromechanical oscillations. This paper presents a particle swarm optimization based approach for tuning the parameters of PSSs in multi-machine power systems. The stabilizers are tuned to simultaneously shift the undamped and lightly damped electromechanical modes of all plants to a prescribed zone in the s-plane. A multiobjective problem is formulated to optimize a composite set of objective functions comprising the damping factor and the damping ratio of lightly damped electromechanical modes. The performance of the proposed PSSs under different disturbances, loading conditions, and system configurations is investigated on two multi-machine power systems. The non-linear simulation results are presented under wide range of operating conditions; disturbances at different locations show the effectiveness and robustness of the proposed PSSs and their ability to provide efficient damping of low frequency oscillations.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Power System Stabilizer, Electromechanical Oscillations, Particle Swarm Optimization, Multi-machine Power System.

   Fast Optimal Power Flow Using Linear Programming Applicable in Power System Planning
         by Arash Shabani

         Vol. 4. n. 5, pp. 2480-2484

Abstract - The problem of power system expansion planning has large dimensions in generation and transmission sections. One of the required tools which have an important role in this problem analysis is power flow. Optimal DC power flow is faster than AC power flow and it is preferred for large problems.
In this paper, an approach of fast optimal power flow based on DC power flow is presented and is formulated simply to be user friendly. The linear programming is used as an optimization tool to solve this problem. Finally, performance of the proposed approach is studied on a case. The results verify that this approach can be used as a tool in planning problems easily.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Expansion Planning, Linear Programming, Optimal Power Flow.

   Comparison of Voltage Stability by Optimal Location of TCSC and SVC Using Loss Sensitivity Method under Line Outages
         by J. Sridevi, Dr. J. Amarnath, Dr. G. Govinda Rao

         Vol. 4. n. 5, pp. 2485-2493

Abstract - It is becoming increasingly important for power system planning and operating engineers to be capable of performing comprehensive voltage stability analyses of the systems. This need is largely due to the recent trends towards operating systems under stressed conditions—as a result of increasing system loads without sufficient transmission and/or generation enhancements. There have been many failures, due to voltage instability in power systems around the world. This paper is mainly concerned with optimal location of Thyristor Controlled Series Capacitor and Static VAr Compensator using loss sensitivity method for voltage stability improvement even at critical line outages contingency cases. The effectiveness of the proposed method has been tested on an IEEE 118 bus system and 62 bus Indian Utility System. The results show that the suggested method of Static VAr Compensator placement is effective than Thyristor Controlled Series Capacitor for voltage stability improvement during normal as well as critical contingency cases.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Voltage Stability, Thyristor Controlled Series Capacitor, Static VAr Compensator, Contingency, Loss Sensitivity.

   Application of Matlab/Simulink for the Analysis of Multi-Machine Transient Stability of a Power System
         by P.Nagaraju Mandadi, K.Dhanvanthri

         Vol. 4. n. 5, pp. 2494-2501

Abstract - Simulink is an advanced software by Math Works Inc., which is increasingly being used as a basic building block in many areas of research. As such, it also holds great potential in the area of power system simulation. In this paper, we have taken a multi-machine power system example to demonstrate the features and scope of a Simulink- based model for transient stability analysis. A self-sufficient model has been developed with full details, which can work as a basic structure for an advanced and detailed study. The effects of Excitation controller and speed governing systems has also been demonstrated and any additional controllers can be incorporated very easily for any desired accuracy.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Transient Stability, Exciter, Speed Regulator, Load Flow, Simulink, Matlab.

   Impacts of Reducing Short Circuit Current Level on Circuit Breakers Transient Studies
         by J. Beiza, Mehdi Salaynaderi, N. Taghizadegan, A. A. Dadjouyan, J. Rabbaani

         Vol. 4. n. 5, pp. 2502-2511

Abstract - Increase in demand and ever-increasing expansion of interconnected power networks lead to increase in short circuit levels higher than interrupting rating of power circuit breakers and other pertinent equipments. This paper is considered planned expansion of Iran Electric Power Network for 2013. A few substations such as Rey-Gas substation in Tehran Regional Electric Company have been experiencing the over mentioned problem for long time. Firstly, necessity of fault current limiter utilization in substations which face high short circuit current levels has been investigated. Then, considering infrastructure and condition of the substation, number of practically applicable methods are employed to control and reduce short circuit level and a suitable method is selected on the base of maximum reduction rate of fault current range after limiting as well as minimum variation rate of bus voltage and active power losses and static stability limit in Tehran Regional Electric Power Network. At the end, the most suitable configurations which provide maximum fault current limitation and has minimum effect on load flow results have been compared in regards to switching transient over voltage. All simulations were carried out utilizing DIgSILENT software package and results showed that the final selected method is able to limit fault current level down to nominal interrupting level of circuit breakers and TRV will have desired condition.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Short circuit level, Fault current limiter, Bus split, Interphase Power Controller (IPC), Current Limiter Reactor, Transient Recovery Voltage (TRV).

   An Intelligent Diagnostic System for Condition Monitoring of Ageing Glass Insulators
         by Nouruddeen Bashir, Hussein Ahmad, Muhammad Abu Bakar Sidik

         Vol. 4. n. 5, pp. 2512-2518

Abstract - A strong correlation exists between leakage current (LC) and insulator surface condition in relation to contamination severity and flashover. Subsequently, systems have been developed to monitor and evaluate contamination flashover. However, few works have been reported on the relationship between LC and insulator ageing especially glass insulators and thus a system capable of diagnosing ageing transmission line glass insulators does not exist. This paper describes the design and development of an intelligent diagnostic system for ageing transmission line insulators. The system consists of hardware and computer program. The LabVIEW and MATLAB softwares were employed to develop the computer program. Results from laboratory experiments using the developed system have shown the capability and effectiveness of the system in characterizing the surface condition of aged insulators.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Ageing, Artificial Neural Network, Contamination, Flashover, Glass Insulator, Labview, Leakage Current, MATLAB.

   Simultaneous Effect of Temperature and Site Altitude on Generators Output
         by M. M. Hamidi, A. Estebsari, M. Ardebili, A. J. Shahrood

         Vol. 4. n. 5, pp. 2519-2523

Abstract - The effect of environmental conditions of the site must be considered as one of the most important aspects of designing generators as well as theoretic calculations and considerations. The real amounts which are measurable on the sites under real conditions are usually different from the rated values of the generators. In this paper we exerted this consideration and a typical model of generator produced by Ansaldo Energia was selected and studied. The material of the generator application guide and the measured values on site are used to get related curves of the environmental conditions effect, such as the effect the site altitude and the ambient temperature, on generator rated values. The practical and measured values of this model of generator which has been installed on Parand and Oroumieh sites in Iran are used for verification of the results of this paper and the related error is calculated. We claim this technical research has not been done before with such mentioned considerations and necessities. This paper gives the necessary instruction to evaluate the applicability and the generator characteristic data at different operating conditions (load, voltage, power factor, site and cooling condition). This study enables the designer to evaluate the generator behavior under the customer requirements and environmental conditions as well as to prepare the necessary proposed documentation for the client.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Generator, Environmental Conditions, Site Altitude, Environment Temperature, Output Power, Rated Power.

   Simulation-Based Criteria for the Power Sizing of Grid-Connected PV Systems
         by G. Velasco, F. Guinjoan, R. Piqué, M. Román, A. Conesa

         Vol. 4. n. 5, pp. 2524-2533

Abstract - This paper discusses about the photovoltaic (PV) generator/inverter power sizing factor in grid-connected PV systems. The optimal sizing factor is defined as sizing factor value that maximizes the yearly energy injected to the grid. The criteria obtained for the sizing factor choice come from the estimation of the injected energy by means of a set of Matlab-based simulations. These simulations involve a simulation-oriented model of the PV conversion chain elements, the environmental data of several European sites as well as the PV installation mounting type, the PV cell materials characteristics, the inverter efficiency and the estimation of DC power losses. The simulation results show, among others, that the current practice of under-sizing the inverter maximum power, with respect to the PV generator nominal power, may not be the best choice in terms of yearly produced energy. These results also evidence the strong impact of both the PV generator operating temperature and inverter efficiency in the choice of the optimal inverter power sizing, and on the yearly energy injected to the grid.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Grid-Connected PV Systems, PV System Modeling, PV System Simulation, Sizing Factor.

   Determination of Resistance to Earth for Rod Grounding by Use of a Finite Element Method – Application to Benin Grounding System
         by Sossou Houndedako, Jean-Marie Kauffmann

         Vol. 4. n. 5, pp. 2534-2543

Abstract - Grounding substations are one of the fundamental elements in electrical power supply protection systems for all types of equipments but especially for electronics one which are very sensitive to lightning. Rod grounding is usually used in states like Benin. Grounding resistance is highly depending on field geology and on atmospheric conditions which can change rapidly. So it is interesting to have at disposal a model able to evaluate quickly the grounding conditions. In complementary with approached formulas we propose a more general tool using FEM in 2D or 3D. The validity has been verified in comparison with well known expressions. FEM may be used for more general geometries of the different layers in the soil or with continuous variable resistivity. The Wenner’s method has also been modelled using a 3D FEM. It allows extending the classical two-layer modelling to a three-layer one by linking two two-layer models. It has been verified by using FEM and has been applied to substations in Benin with a sufficient accuracy.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Grounding Substation, Soil Resistivity, Resistance, Analytical Method, Finite Element Method, Wenner’s Method.

   Using Fuzzy Method for Tradeoff Management between Exploration and Exploitation in Multi-agent Systems
         by Somayeh Hajforoosh, Seyed Mohammad Hossein Nabavi

         Vol. 4. n. 5, pp. 2544-2553

Abstract - Balancing between exploration and exploitation in multi-agent environments is a dilemma that does not have a clear answer and there are still different methods for investigation of this problem that all refer to it. This paper presents a fuzzy variables based method for balancing between exploration and exploitation in the multi-agent environments. Fuzzy variables and rules are used to update the exploration probability, ε, using fuzzy variables in each step to improvement the tradeoff between exploration and exploitation. In addition, the Nash-Q method is used in order to determine and learn agents functions’. The proposed algorithm is investigated to determine an optimized path in the Grid World. In this method, agents effort to reach locations with a highest gain in cooperative and noncooperative environment. Outcomes of the suggested fuzzy based algorithm compared with the results by conventional ε-greedy method. First we use our proposed fuzzy based algorithm in cooperative environment then we present this method in a noncooperative one. Several quality improvement of interaction between exploration and exploitation is discussed.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Reinforcement Learning, Multi-Agent Environment, Balance between Exploration And Exploitation, Nash-Q.
 

   An Energy Cost Minimization Algorithm for Wind Turbine System Design
         by Ulas Eminoglu

         Vol. 4. n. 5, pp. 2554-2563

Abstract - Optimal Wind Turbine System (WTS) design for one location is not necessarily the optimal design for another location because the wind speed distribution may wary between locations. For wind turbine design, the most important design variables may be listed as generator capacity, rotor diameter and hub height. This is due to the fact that a larger rotor captures more energy and a larger generator can capture more energy as well but also costs more. Moreover, the wind speed increase with hub height but so does the tower cost. They must match one another and the optimal match is dependent on the site’s wind conditions. Accordingly, this paper introduces a design optimization algorithm based on minimizing the cost of energy of a Horizontal Axis Wind Turbine (HAWT) to be operated at a specific wind site. The algorithm uses probability distributions of wind speed and computes optimal values of HAWTs’ design parameters such as generator capacity, rotor diameter and hub height by taking into account site’s wind condition to generate electrical energy in minimum cost.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Cost of Energy, Design Optimization, Horizontal Axis Wind Turbine, Probability Distributions of Wind Speed.

   Modeling the Mechanisms of the Processes Optical Pumping in Dyes Lasers
         by Mohammedi Ferhat, Bensaada Said

         Vol. 4. n. 5, pp. 2564-2569

Abstract - Liquid dye lasers are a coherent source of radiation with a wide tuning range and find many applications in various fields. However, these lasers cannot be used in certain applications due to the need for large volumes of organic solvents. All the chemical bonds have frequencies of vibration which are clean for them. One studied methods which aim at using the interaction light-matter to obtain information on these molecular, vibrations. To reach the spectrum vibration of the molecules which interact with a beam luminous in a process of diffusion, a wave pumps, in a photonic vision of the process, the waves correspond to absorption to leave respectively the level vibration fundamental or excited. The process generating the wave excited, on the basis of the excited level vibration, Theoretical predictions are compared with experimental results. The feasibility and effectiveness of the proposed method is demonstrated by computer simulation.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Modeling Process, Lasers, Populations Inversion, Pumping Optical, Simulation.

   Optimal Determination of Financial Transmission Rights for Presenting in Primary Auction with Considering the Energy Market Conditions
         by M.Birzhandi, J.Khodaei, M. Abroshan, S. Tarafdar, B. Abdi

         Vol. 4. n. 5, pp. 2570-2577

Abstract - Financial transmission rights is considered to be a financial tool to cover the congestion risk and more clearly it can be referred to as one of the congestion risk management tools. The FTR is defined from point to point and more specifically from the injection point to the receiving point in many works, the researchers put the emphasis on the profit of the FTR buyers. In this paper, we focus on the FTR selling by the independent system operator (ISO) in the primary auction. The important advantage of the presented and simulated method in this paper is considering the market conditions and its integration with the mathematical model of the average-variance method for reducing the selling, risk by the ISO. The proposed method was tested on a sample system and the results are depicted.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: FTR, LMP, Primary Auction.

   Modeling and Design of Patient-Electrodes Isolator for Bioimpedance Measurement
         by M.Chaoui, M. Boussarsar, H. Ghariani, M. Lahiani

         Vol. 4. n. 5, pp. 2578-2584

Abstract - This work is part of a process aiming at measurement of the biogical impedance charactisations. The tools include methods to measure the macroscopic electrical properties of biological media, and numerical methods allowing to model and compute the bioimpedance of the human body. The main instrumentations of biological tissue isolation of a signal electrical and the existing characterisation methods are presented. The main specificities and operating frequency range are emphasized in this article. A usual description method based on four-electrode impedance measurements is then studied. In this article we present a concept electrical isolation of patient for bioimpedance. Medical safety requires measurement of electrical bioimpedance, wherein an alternating current is applied to the human body, an isolation barrier between the energy source, which provides the energy for the current, and the human being. This isolation barrier can be accomplished by using a wide bandwidth transformer.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Bioimpedance, Electrical Isolation System, Safety Device, Current Source.

   Modeling Pilgrims Movement using GPS and GSM Notification
         by Mohd Helmy Abd Wahab, W. Zafirah W. Ibrahim, Herdawatie A. Kadir, Ayob Johari, A. Noraziah, Roslina M. Sidek, Ariffin A. Mutalib

         Vol. 4. n. 5, pp. 2585-2590

Abstract - This paper report the development of a prototype model to locate missing people in a location with big crowds such as in Mecca during Hajj time. The prototype integrates the Global Positioning System (GPS) for data transmission and the Global System for Mobile (GSM) network to track missing Malaysian Hajj pilgrims. The prototype is developed using Microsoft Visual Basic and Microsoft Access as the database. In addition, the development involves also GSM modem and circuit configuration. The prototype has been initially functionally tested. Accordingly, results indicate that the prototype can be used in locating the missing Hajj successfully.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Global Positioning System, Global System For Mobile, Tracking System, Databases.
  

   A Novel Fault Location Algorithm for Multi-Tapped Transmission Lines Using Local Measurement
         by A. Esmaeilian, M.Tasdighi, S. Astinfeshan, M. Mohajeri, M. Ansari

         Vol. 4. n. 5, pp. 2591-2601

Abstract - The tapped lines are usually used to supply small communities or facilities in sparsely populated and isolated rural areas. Locating faults in such lines are difficult regarding the effect of infeed/outfeed current from tapped lines as well as reactance effect. To deal with mentioned problems a novel one ended fault location algorithm is presented in this paper, which applies generalized models of fault loop voltage and current to formulate the fault location algorithm. The derived algorithm has a very simple first-order formula and does not require knowledge of data from other ends. This feature becomes more significant in the case of isolated rural areas where it may not exist proper communicational link to exchange data with main ends. The methodology is based on calculating the current distribution factor and estimating the current from two other ends, so it measures the exact distance from fault locator to fault point. The result of simulation for three ended transmission line verifies the high accuracy of the method with regard to various equivalent source impedances, fault resistances and locations as well as fault types. Finally the algorithm expanded to multi-tapped lines and the results demonstrate the high accuracy and robustness of the proposed algorithm.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Fault Locator, Current Distribution Factor, Multi-Tapped Line, Infeed/Outfeed Current.

   A High-Speed Relay for Integrated Fault-Identification and Zone-Classification in EHV Transmission Lines
         by O. Asokan, R Sreerama Kumar

         Vol. 4. n. 5, pp. 2602-2607

Abstract - In this paper a novel approach based on Radial Basis Function Network (RBFN) is proposed for fault identification and zone classification in extra high tension (EHT) lines for high speed protection using terminal line data. The proposed method utilizes the current and voltage signals measured online at the line terminals for generating the training patterns for training the RBFN and with this approach, the faulty phase identification and fault zone classification could be achieved very effectively. The effectiveness of the proposed relay model is established by comparing its performance with an existing practical numerical line protection relay.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Fault Identification, Zone Classification, Transmission Line Protection, Radial Basis Function Neural Network.

   A New Method for Classification of Different Types of Ferroresonant Oscillations Modes
         by A. Abbasi, M. Rostami, A. Gholami, H. R. Abbasi

         Vol. 4. n. 5, pp. 2608-2620

Abstract - In this paper a new method for classification of different types of ferroresonant oscillations modes is introduced. Using this method, ferroresonant modes such as harmonic, subharmonic, quasi periodic and chaotic modes are characterized and using multiple scales method chaotic behavior and types of fixed points in occurrence of ferroresonance in voltage transformer with considering a nonlinear core loss model is analyzed and investigated. It is proved that ferroresonance phenomenon in voltage transformer can be classified in chaotic dynamics systems. In this contribution chaos occurs in system from a sequence of period doubling bifurcation (PDB). This phenomenon includes different types of bifurcations such as period doubling bifurcation (PDB), saddle node bifurcation (SNB), hopf bifurcation (HB) and chaos. Analysis of dynamics of ferroresonant circuit is carried out using bifurcation theory. For this work bifurcation diagrams and phase plane diagrams are drawn using a continuation method for linear and nonlinear core loss models, lyapunov exponents are gained using multiple scales method and feigenbaum number are used. Bifurcation diagrams show with changing parameter of control and its increasing chaos occur in system. Border collision is shown in bifurcation diagrams. 
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Ferroresonant Oscillations, Chaos Theory, Period Doubling, Subharmonic Mode, Poincare Map, Bifurcation Diagram.

  Investigation of Buckling Behaviors of Graphene Sheets via Molecular Mechanics Method
           by M. M. S. Fakhrabadi, V. Norouzirfard, M. Dadashzadeh, B. Dadashzadeh

           Vol. 4. n. 5, pp. 2621-2626

Abstract - This paper investigates the buckling loads and mode shapes of the graphene sheets with two widely used boundary conditions including cantilever and doubly fixed. We employ molecular mechanics to simulate the bond between carbon atoms. Afterwards, the buckling phenomena of the graphene sheets with different dimensions and boundary conditions are studied using molecular mechanics-based finite element method. The results propose higher load values for the doubly fixed boundary condition in comparison with the other one.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Graphene Sheet, Buckling, Finite Element Method.

   A New Procedure for Solving the Shortest Superstring Problem, Using the Memetic Algorithm
         by A. Safaei, M. Shams-Javi

         Vol. 4. n. 5, pp. 2627-2633

Abstract - The shortest superstring problem (SSP) is a NP-Hard which is used a lot in data compression algorithms, data encryption and also in medical and biological calculations. This problem remains a NP-Hard problem, even with different limitations in size of superstring alphabet. This article presents an optimal solution for shortest superstring problem via using memetic algorithm. Memetic algorithm is an evolutionary algorithm that mixed the local searches with partial improvements to reach better solutions than other evolutionary algorithms like as genetic algorithm.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Memetic, Memetic Algorithm, Shortest Superstring, SSP, Superstring.

   Evaluation of the Performance Study of Solar Air Collector by Using Bond Graph Approach
         by H. Oueslati, S. Ben Mabrouk, A. Mami

         Vol. 4. n. 5, pp. 2634-2643

Abstract - In this paper, the modelling and thermal performance results of the solar air collector have been presented. This system is conceived to heat the ambient air in order to be used in many domains like drying processes and heating buildings. The pseudo-bond graph methodology was used in modelling this system. Such methodology was very suitable for this thermodynamic process since it allows good management of the non-linearity present in the system. The simulation of the global model with bond graph software [20-sim] allows us to analyze the temperature variations and the efficiency of the solar collector and compared with experiment results.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Solar Air Collector, Temperature, Collector Efficiency, Pseudo Bond Graph Modelling.

   A Hybrid Method of Memetic Algorithm and Artificial Immune System for Solving RCPSP
         by A. Safaei, M. Shams-Javi

         Vol. 4. n. 5, pp. 2644-2650

Abstract - The RCPSP is a difficult optimization problem and it is ranked as NP- hard. Each project is combined of some discrete or connected activities for which there are some special priority and postponing rules to perform them. The aim of this problem is to choose the best collection of starting times, amount and the type of consuming resources thus constraints is considered and the whole time of the project is minimized. This article discusses a hybrid method of memetic algorithms and artificial immune system to solve this problem. Memetic algorithm is an evolutionary method which reaches to more qualified responses by mixing genetic algorithm with local searches and partial optimization. Artificial immune system algorithm is a meta-heuristic parallel method based on cloning the cells in natural immunity system in the creature's body. The results of the algorithm performance show the success of the suggested compound method.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  AIS, Artificial Immune System, MA, Memetic Algorithm, RCPSP.

   A System for Adaptive Intelligent Learning (SAIL)
         by Murad S. Samhouri, Sahar Idwan, Adnan Mukattash

         Vol. 4. n. 5, pp. 2651-2656

Abstract - The main purpose of this paper is to introduce a complete design of a novel system for adaptive intelligent learning system (SAIL), and to innovate on both technical and conceptual fronts by addressing relevant barriers. This research was focused on actualizing a human centered approach through the guidance of experts in the learning and psychological fields. System intelligence was sought through the utilization of automated machine learning technologies to classify learners as well as through information processing at a semantic level. Adaptively was achieved through the constant monitoring of learners' behavior and psychophysiological status, feedback and performance to draw actionable conclusions for both the learners and the system itself. SAIL uses intelligent and interactive technologies in processing individual learner perceptions, preferences and cognitive profiles. In addition, it focuses on a highly configurable architecture to provide a system that can be used in varying training scenarios, so as to produce a tailor-made learning experience, suiting both the needs of the individual learners and the goals of the organizations, thus, improving the professional training process outcomes. Evaluation of both content and the learning system itself were conducted in a sound and statistically relevant way, under the supervision of learning and cognitive experts. SAIL industrial “added value” are quantified and measured, as the industry needs to see a clear connection between competence gaining of employees, business goals, resources and organizational performance. Emphasis is also given on producing fully-reusable system architecture for varying training purposes in the future.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Adaptive Learning, Intelligent Agent-Based Systems.

   The Modelling of Hybrid Surge Protection Circuit with Effect of Adding a Filter
         by A. M. Ariffen, M. Z. A. Ab Kadir, W. F. Wan Ahmad, M. S. A. Ishak

         Vol. 4. n. 5, pp. 2657-2665

Abstract - Surge protective device is a part of internal lightning protection and it essentially to divert the certain amount of surges to the ground before the protected load able to handle. Therefore, this paper studying the enhancement of SPD through the effect of adding a filter in hybrid surge protection circuit using simulation modelling. Customarily, filter is used as in eliminating noises in certain application such as electronic apparatus. In addition, an experiment testing is pursues in high voltage laboratory for evaluation and to validate the simulation. The analysis involved the surge protector Class 3 according to IEC or Category A as referring to IEEE standards with a filter design concerning the combination of inductor and capacitor. The significance of filter whether it is appropriate to be added in hybrid circuit is being discussed whilst in this simulation the filter design involving the combination of inductor and capacitor with varistor at first stage followed by transient voltage suppressor diode in second stage. From this research is found that a significant improvement of about 38% obtain when filter is added in surge protective device.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Surge Protector, Transient Voltage Suppressor Diode, Metal Oxide Varistor, Hybrid Protection, Surges, EMI Filter.

   Fuzzy-Based Active Force with Computed Torque Control of 3-RRR Parallel Robotic Manipulator
         by A. Noshadi, M. Mailah

         Vol. 4. n. 5, pp. 2666-2676

Abstract - This paper presents a robust intelligent scheme to control a highly non-linear parallel manipulator. The primary objective is to force the manipulator to track a prescribed Cartesian trajectory accurately when the system is subjected to different types of disturbances in the forms of forced harmonic excitations. In fact, in an environment containing various forms of disturbances, noises, uncertainties, and parametric changes, a robust control approach is pivotal in ensuring the system performance conforms to the desired specifications. A class of computed torque controller (CTC) is designed in cascade form with an active force control (AFC) technique which employs a fuzzy logic (FL) algorithm to control a 3-RRR (revolute-revolute-revolute) planar parallel manipulator. The scheme to be known as CTC-AFCAFL is applied in order to reject the disturbances while at the same time precisely track the prescribed trajectory in the wake of the introduced harmonic disturbances. The FL is specifically used to compute the estimated inertial parameters required in the AFC loop to trigger the compensation effect. The simulation results provide further insight into the superiority of the proposed control scheme in rejecting the disturbances of the 3-RRR manipulator system for the given loading and operating conditions. The results clearly demonstrate that the proposed CTC-AFCAFL scheme provides a much superior trajectory tracking capability compared to the conventional CTC alone.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  3-RRR Parallel Manipulator, Active Force Control, Computed Torque Control, Fuzzy Logic, Robust Motion Control.

   Prandtl and Hartmann Numbers Effects on Entropy Generation in Natural Convection
         by Atef El Jery, Mourad Magherbi, Ammar Ben Brahim

         Vol. 4. n. 5, pp. 2677-2690

Abstract - The influence of Prandtl number on entropy generation in natural convection under an external uniform magnetic field for different electrically conducting fluids, from liquid metal to liquid passing through gas, in square cavity is numerically studied in steady-unsteady states by solving the mass, the momentum and the energy conservation equations. Entropy generation depends on three parameters which are: the Prandtl, the Hartmann and the thermal Grashof numbers. Effects of these parameters on total and local irreversibilities as well as on heat transfer and fluid flow are studied. It was found that the magnetic field tends to decrease the convection currents, the heat transfer and entropy generation inside the enclosure. The effect of Prandtl number tends to increase the heat transfer, on the other hand tends to decrease the entropy generation.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Heat Transfer, Convection, Magnetic Field, Cavity, Entropy Generation and Numerical Methods.

   A Robust Closed-Form Solution of Nonlinear Heat Transfer Equations
         by G. Darmani, S. Setayeshi, H. Ramezanpour

         Vol. 4. n. 5, pp. 2691-2695

Abstract - We proposed an analytic method, sensitivity approach, for computing the closed-form approximate solution of nonlinear heat transfer equations, which are described mathematically by a nonlinear ordinary differential equation. In this manner we avoid directly solving of nonlinear ordinary differential equations by discretization or linearization which can lead to low accuracy in resulted response. This approach is very easy to use and only requires solving a sequence of linear differential equations. The effect of small parameter increaser on the accuracy of the analytical result also has been studied. A cooling lumped system with combined convection and radiation has been focused as a case study and the results have been compared with homotopy perturbation method and homotopy analysis method.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Nonlinear Heat Transfer Equation, Sensitivity Approach, Closed-Form Solution.

   A Hybrid Power Series – Artificial Bee Colony to Solve Magnetohydrodynamic Viscous Flow over a Nonlinear Permeable Shrinking Sheet
         by Aminreza Noghrehabadi, Mohammad Ghalambaz, Mehdi Ghalambaz

         Vol. 4. n. 5, pp. 2696-2700

Abstract - A hybrid Power series and Artificial Bee Colony Algorithm (PS-ABC) is applied to solve a system of nonlinear differential equations arising from the similarity solution of magnetohydrodynamic viscous flow over a nonlinear permeable shrinking sheet. The flow is subjected to variable magnetohydrodynamic effects. A similarity solution is obtained for the boundary layer governing equations. Then, a trial solution of the governing differential equation is defined as sum of two polynomial parts. The first part satisfies the boundary conditions and contains an adjustable parameter and the second part which is constructed so as not to affect the boundary conditions and involves adjustable parameters (Coefficients of polynomial of the second part). The artificial bee colony algorithm is applied to find adjustable parameters of trial solution (in first and second part). The problem successfully is solved using proposed method. The obtained solution is compared with numerical solution as well as exact solution in a case which closed form exact solution exists. The main objective is to propose a power series solution which do not require small parameters and avoid linearization and physically unrealistic assumptions. In addition, the results of presented method represent a remarkable accuracy in compare with exact solution and numerical results. Present method can be easily extended to solve a wide range of boundary layer problems.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  MHD, Artificial Bee Colony, Similarity solution, Power series, Variable magnetic.

   The Variable Porosity Effect on the Natural Convection in a non-Darcy Porous Media
         by M. Sammouda, K. Gueraoui, M. Driouich, A. El Hammoumi, A. Iben Brahim

         Vol. 4. n. 5, pp. 2701-2707

Abstract - The objective of this work is to establish a numerical code in order to study the natural convection in a cylinder heated from bellow and filled with a porous media which has a variable porosity. A generalized non-Darcian porous medium model for natural convective flow has been developed taking into account the viscous forces within the fluid, The porosity of the medium is assumed to vary exponentially with distance from the wall. The dimensionless equations reveal some important dimensionless numbers controlling this phenomenon such as the thermal Rayleigh number, Ra, the number of Darcy, Da, the number of Prandtl, Pr, the aspect ratio, RA, and the porosity, ε. It is found that the variable porosity has an effect on the flow and the heat transfer rate.
The established numerical code can also be used in various other industrial applications.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Natural Convection, Porous Media, Variable Porosity, Cylindrical Cavity, Extension Darcy Law.

   New Study of the Propagation of a Quasi-TEM Wave by the Finite Elements Method
         by S. Mekerta

         Vol. 4. n. 5, pp. 2708-2714

Abstract - This study is to correctly model a coplanar line (Coplanar waveguide, CPW) by localized elements, inductance and capacity . The coplanar line is characterized analytically in the frequency band where the transmission is quasi-TEM. The circuit under the Ansoft Designer software simulation results are compared with analytical modelling under Matlab between 1 and 8 GHz as well as a numerical modelling 3D under Ansoft HFSS which use the finite elements method. The results obtained by the three methods are in good agreement. Experimental results are presented and demonstrate excellent agreement with the simulations. That allows to define rules of design based on simulation of type circuit which is very fast and very effective compared to other 3D electromagnetic simulation software.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Modelling, Coplanar Waveguide, Cells, Repartited Elements ,Quasi -TEM.

   Hydrodynamic and Thermal Characteristics of Conjugate Heat Transfer in an Annular Finned Duct
         by M. Benkhedda, T. Boufendi

         Vol. 4. n. 5, pp. 2715-2723

Abstract - This study concerns the modelisation and the simulation of the three-dimensional conjugate heat transfer, the forced and the mixed convection in the fluid and the conduction in the solid, between two long horizontal concentric cylinders of finites thicknesses. The inner wall of the internal cylinder is subject to a constant heat flux. The outer wall of the outer cylinder is adiabatic while the inner wall is equipped with longitudinal fins. The fins are of the same physical nature as the solid wall. The complete model Navier-Stokes equations are numerically solved by the finite volume method with the schemes of spatial and temporal discretizations of second order precision. The results obtained show a complete change of fluid flow structure with new distributions of velocity and temperature for various fins configurations and different numbers of fins considered. These results are compared with the unfinned case. For a same Reynolds number, the addition of fins causes a significant increase of the axial velocity and temperature. Also, for a same configuration and a same number of fins, the axial velocity, as well as the temperature, decreases with the increase of the number of Reynolds.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Annulus, Finite Volume Method, Conjugate Heat Transfer, Fins.

   One Model of Vertical Armature Construction inside Concrete Foundation and Ring Electrodes as Pillar Grounding System
         by Nenad N. Cvetković, Dejan D. Krstić

         Vol. 4. n. 5, pp. 2724-2733

Abstract - Unknown current distributions along axe of the pillar grounding system's wire conductors are determined in the paper. The system consists of vertical wire electrodes inside the cylindrical concrete foundation and a system of ring electrodes formed of different number of rings. The paper describes a simple procedure for modeling a system of vertical wire armature electrodes placed inside the concrete cylinder using a single wire electrode of equivalent parameters placed in homogeneous ground. Unknown currents of polynomial form are determined solving the system of integral equations using the Method of Moments. The analysis grounding systems consisting of one, two or three ring electrodes is carried out. There is a significant mutual influence between the two parts of the grounding system. The first part is a system of armature electrodes and the second one is a system of interconnected ring electrodes. As measure of this influence, self- and mutual-resistances are determined. The results of the applied procedure are also the values for total resistance, as well as electrical scalar potential distribution on the ground surface.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Electromagnetic Analysis, Grounding Electrodes, Pillar Foundation, Polynomial Approximation.

   A Thermo-Elasto-Plastic Model for Cemented Soils under Unsaturated Condition
         by Anuchit Uchaipichat

         Vol. 4. n. 5, pp. 2734-2738

Abstract - This paper presents a development of thermo-elasto-plastic model for unsaturated soils under unsaturated condition based on the effective stress principle. The thermo-elasto-plastic framework satisfies the equations of total stress equilibrium, compatibility and consistency. The yield surface is affected by plastic volumetric strain, cementation bond, matric suction and temperature. The variation of yield surface with matric suction is obtained from the loading collapse curve which varies with cementation bond and temperature. Plastic flow is defined using a generalized associated flow rule.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Unsaturated Soils, Cemented Soils, Thermal Effect, Elasto-Plastic Model.

   A Conceptual Framework for Collaborative Design Process
         by Manuel-Viggo Castilla

         Vol. 4. n. 5, pp. 2739-2742

Abstract - Developments in SIC²T (Sciences, Information, Communication and Computing Technology), have an impact not only from the process and technical point of view, but also from the creative design point of view. Many software systems are in common use in the field of engineering design. The general objective is to support the designer during the whole creative process in order to increase the efficiency and to improve the quality of the final products. In this work we will provide a survey on a project dealing with the solution of both problems. First we will give a general description of the support that software can provide to engineers during the design process. Second, many different tools are needed which have to be integrated. Support software for the engineer designer will become tools will be integrated and be able to communicate with each other. Exact Sciences such as Physic and Mathematics, and new technologies will make contributions to the problem solving aspects of the conceptual, simulation and materialization process. This paper provides an overview of these techniques include into SIC²T.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Engineering Design, Simulation, Advanced Mathematics, Software, Decision Support.

   2D-FEM Simulation of the Effects of Welding Current, Sequence and Geometry on Residual Stresses in Dissimilar Joints
         by E. Ranjbarnodeh, M. Farajpour

         Vol. 4. n. 5, pp. 2743-2748

Abstract - In the present study a 2D thermo-mechanical model is developed to analyze the effects of welding current, sequence and workpiece geometry on the of residual stresses in dissimilar TIG welds between low carbon steel CK4 and ferritic stainless steel AISI409. To perform the simulation, a finite element program, ANSYS, is used. To verify the predictions, the model results are compared with residual stresses measured by X-ray diffraction and good agreement is found. The results show that the magnitude of tensile residual stresses increases by increasing the welding current while larger residual compressive stresses are produced in the longer samples. Evaluating of residual stresses with various types of welding layouts also shows that symmetric and back-step welding sequences have little effects on minimum of residual stress however, the magnitudes of residual stresses significantly decrease in the middle part of the welded sample as symmetric welding sequence is employed.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords:  Dissimilar Joint, Welding Residual Stresses, Welding Sequence, Geometry.