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International Review of Electrical Engineering  Vol. 5 N. 3-- Part A

International Review of Electrical Engineering  Vol. 5 N. 3-- Part B


International Review of Electrical Engineering - June 2010 - Papers Part A



go to top     International Review of Electrical Engineering - June 2010 - Papers Part B



International Review of Electrical Engineering - Papers- Part A


go to top   Analysis and Implementation of a Dual ZVS Flyback Converter
         by Bor-Ren Lin, Ming-Hung Yu

         Vol. 5. n. 3, pp. 812-819


Abstract - This paper presents a zero voltage switching (ZVS) converter for requiring low output current ripple. The proposed converter includes two active-clamp flyback converters to have well regulated and smooth dc output without the need the output filter inductor. Two interleaved parts use the primary windings to share one capacitor and to realize the active-clamp. By the shared capacitor, the charge balance of two interleaved parts is automatically regulated under input voltage and load variations. Based on the resonance between the leakage inductor and equivalent output capacitors of switches during the transition interval, the switching losses of the switches are used. The interleaved pulse-width modulation (PWM) operation will further reduce the ripple current and the size of the output capacitor. Finally the prototype circuit with 12V output voltage and 40A output current has been built to verify the effectiveness and performance of the proposed circuit.

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Keywords: Zero Voltage Switching, Flyback, PWM.



go to top   Study and Control of Three-Level PWM Rectifier-Five-Level NPC Active Power Filter Cascade by Using Feedback Control and Redundant Vectors
         by T. Abdelkrim, E. M. Berkouk, K. Benamrane, T. Benslimane

         Vol. 5. n. 3, pp. 820-830


Abstract - The purpose of this paper is to develop a control and regulation method of input DC voltages of five-level Neutral Point Clamping (NPC) Active Power Filter (APF). This APF is applied for the enhancement of medium voltage network power quality by compensation of harmonic currents produced by an induction motor speed variator. In the first part, the authors present a topology of five-level NPC Voltage Source Inverter (VSI), and its simplified Space Vector Pulse Width Modulation (SVPWM) control strategy. In the second part, the control strategy of Three-level PWM current rectifier is presented. In the third part, to remedy to instability problem of the input DC voltages of the APF, the authors propose the feedback control of the three-level rectifier associate with a simplified SVPWM with redundant vectors method of five-level APF. After that, the sliding mode regulator used to control the APF is developed. The application of the proposed control algorithm offers the possibility of stabilizing the DC voltages of APF. Stable DC bus supply associated with sliding regulator of APF allows getting low-harmonic content network currents with unity power factor. In all over, the instability problem associated with use of multilevel APF is solved. The obtained results are full of promise to use the multilevel APF in medium voltage and great power applications.

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Keywords: Active Power Filter, Feedback Control, NPC Multilevel Converter, Redundant Vectors, Space Vector Pulse Width Modulation (SVPWM).



go to top   Implementation of a Resonant Converter with Input Series Connectionand Output Parallel Connection
         by Bor-Ren Lin, Po-Li Chen, Yu-Cyun Shao

         Vol. 5. n. 3, pp. 831-841


Abstract - Series resonant converters with variable frequency modulation have been widely used for high efficiency consumer power supplies such as power units of LCD monitor and all-in-one computer. The advantages of LLC resonant converters are higher voltage gain, zero voltage switching (ZVS) turn-on for power switch with wide load range, zero current switching (ZCS) turn-off for rectifier diodes, and output voltage regulation at no-load condition. In the proposed converter, the output sides of LLC converters are connected in parallel to reduce the current stresses on output diodes. Thus the current stress of rectifier diodes is reduced and output diodes have no reverse recovery loss. The root mean square currents on transformer secondary windings, transformer copper losses, and thermal losses can be further reduced. The input sides of two LLC converters are connected in series thus the voltage stresses of each power switches are clamped to half of dc input voltage. Thus low conduction resistance of MOSFETs can be used to reduce the conduction losses. The principle of operation, steady state analysis and design example of the proposed converter are provided and discussed in detail. The proposed converter can be used for high efficiency consumer products such as LCD-TV, PDP-TV and server power supply unit. The laboratory experiments are provided to verify the effectiveness of the proposed converter.

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Keywords: Power Supply Unit, Series Resonant Converters, ZVS, ZCS.



go to top   Advanced Modulating Techniques for Multilevel Inverters by Using FPGA
         by V. Naga Bhaskar Reddy, S. Nagaraja Rao, Dr. Ch. Sai Babu

         Vol. 5. n. 3, pp. 842-848


Abstract -  Multilevel inverter is used in applications that need high voltage and high current. The topologies of multilevel inverter have several advantages such as lower THD, lower EMI generation, better output waveform and higher efficiency for a given quality of output waveform.. The main feature of multilevel inverter is the ability to reduce the voltage stress on each power device due to the utilization of multilevel on the DC bus.
This paper presents the development of Xilinx-FPGA SPARTAN 3 as a control circuit for multilevel PWM single phase inverter. 8 I/O lines of SPARTAN 3 are used as PWM output lines for Cascaded 5 level output voltage. Internal architecture of control circuit embeds in FPGA are described in detail. VHDL language is used to model the switching strategies and Xilinx ISE 9.2i software is used as a simulation and compiler tool. The results of compilation consist of 1250 logic elements with Cascaded 5 level output voltage.. In addition to Xilinx FPGA, Matlab/Simulink software was used for simulation. Hardware circuitry is developed for 5 level inverter with continuous firing pulses. Generation of PWM pulses is also obtained with Xilinx-FPGA SPARTAN 3 board. By using Matlab/simulink Modified reference and Modified carriers signals are developed for Cascaded 5 level inverter.

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Keywords: Multilevel concept, Cascade Multilevel inverter, FPGA, Multi level carrier signals, Pulse width modulation, Total Harmonic Distortion.



go to top   Analysis and Implementation of an Interleaved Isolated DC-DC Converter
         by Bor-Ren Lin, Po-Li Chen, Jyun-Ji Chen

         Vol. 5. n. 3, pp. 849-857


Abstract - An interleaved isolated dc-dc converter with simple structure is presented in this paper. The proposed converter is operated in discontinuous conduction mode (DCM). The series-resonant tank composed by leakage inductor and resonant capacitor is used to achieve the ZCS turn-off feature for all rectifier diodes. Hence, the reverse-recovery problem can be eliminated. Besides, the flux reset of transformer can be automatically achieved by resonant capacitors and the voltage stress of rectifier diodes is automatically clamped to output voltage. The advantages of the proposed converter are simple circuit configuration and high conversion efficiency. The operational principle, design consideration and circuit realization are discussed in this paper. Finally, experiments taken from a 320W laboratory prototype are presented to confirm the effectiveness of the proposed converter.

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Keywords: Interleaved PWM, Converters, ZCS.



go to top   Grid-Connected Multilevel Inverter with Intelligent Petri Nets Controller for Ocean Current Power Generation System
         by Jian-Long Kuo, Kai-Lun Chao

         Vol. 5. n. 3, pp. 858-869


Abstract - This paper proposes a grid-connected multilevel in ocean current power generation system. An experimental dynamometer with water tank is built up. A diode-clamped three-level inverter is developed to reduce the voltage change rate of power devices. A Petri-nets controller is used in the multilevel inverter. The multilevel inverter usually requires complex switching logic especially when the space vector PWM is involved. If-then logic description will have tedious programming problem depending on the control logic in the multilevel inverter. By using the developed Petri-nets algorithm in matrix form, the control signals have parallel arithmetic operation in digital controller as compared to the conventional controller for the multilevel inverter. The timing sequence of control logic is generated automatically by matrix approach. Experimental results are illustrated to show the practical control of power and reactive power connecting to the power grid. With the help of the proposed Petri nets controller, it is shown that a systematic Petri-nets based controller is successfully developed in the multilevel inverter connecting to the power grid for the ocean current power generation system.

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Keywords: Ocean Current, Power generation, Multilevel Inverter, Petri Nets, Grid-connection.



go to top   ELECTRE II Multi-criteria Decision Making for Optimum Design of Modular Multilevel Inverter Building Bloc
         by Hammami Hafsa Inès, Faouzi Ben Ammar

         Vol. 5. n. 3, pp. 870-879


Abstract - Modular Multilevel Building Bloc (MMBB) is proposed to replace a high power multilevel inverter by combined series and parallel low power multilevel bloc in order to compare different topologies and to select the optimal one. The decision should consider a variety of multiple criteria such as the cost, reliability, efficiency, output harmonic quality and components sizing. In this paper, the authors propose the ELECTRE II (Elimination Et Choix Traduisant La Réalité) tool for Multi-Criteria Decision Making (MCDM). ELECTRE is applied to compare various multilevel inverter associations according to four criteria and determining the optimum design between the different topologies.

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Keywords: Multi-criteria Analysis, Multilevel Inverter Topologies, Selection, Multi-criteria Decision Making (MCDM), ELECTRE II.



go to top   Interleaved PWM Cuk Converter with Low Switching Loss

         by Bor-Ren Lin, Jyun-Ji Chen, Huann-Keng Chiang, Chia-Yu Yeh

         Vol. 5. n. 3, pp. 880-890


Abstract - This paper presents an interleaved Cuk converter with turn-on switching loss reduction which is composed of two conventional Cuk converter cells and an additional resonant conductor. Two power switches are able to turn on at zero voltage switching (ZVS) operation when it operates with a duty cycle greater than 0.5. Besides, the turn-on switching loss is also reduced due to smooth current by resonant inductor when the duty cycle is smaller than 0.5 even though it is operated at hard switching. In this paper, the operational principles and design consideration are discussed; simulation and experimental results are also proposed to confirm the theoretical analysis and the advantages of the proposed converter.

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Keywords: Zero Voltage Switching, Cuk, Interleaved PWM.



go to top   An Improved Inverter Control Scheme for Managing the Distributed Generation Units in a Microgrid

         by Azuki Abdul Salam, Azah Mohamed, M. A. Hannan, Hussain Shareef

         Vol. 5. n. 3, pp. 891-899


Abstract - This paper presents an improved inverter control strategy for managing power sharing among the distributed generator in a microgrid. The proposed technique combines power and voltage control schemes implemented on the voltage source inverters. Dynamic models of the fuel cell, photovoltaic and micro turbine available in the PSCAD/EMTDC software are used as distributed generation units in the microgrid. To evaluate the effectiveness of the developed inverter control strategy, the microgrid is operated in grid connected and islanding modes of operation. The test results showed that the proposed control strategy provide better management of the distributed generation units in a microgrid.

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Keywords: Distributed Generation, Microgrid, Microturbine, Fuel Cell, Photovoltaic, Inverter.



go to top   Space Vector Model and Control of a Two-Leg Four-Switch STATCOM
         by Tsao-Tsung Ma
         Vol. 5. n. 3, pp. 900-908


Abstract - Voltage control and fast reactive power compensation are two important functions concerning FACTS application in the modern power systems. It has been well accepted that the static synchronous compensator (STATCOM) is the most versatile and powerful FACTS device that can provide effective means for controlling reactive power flow and improving the voltage stability of a power network. However, the STATCOM circuitry has complex and coupled system dynamics which require advanced controllers to achieve satisfactory performances. This paper presents the design of a space vector pulse width modulated (SVPWM) two-leg four-switch STATCOM to provide satisfactory performances in performing various reactive power flow control functions during steady-state and transient operations of power systems. For comparative purposes, two topologies, i.e. 2-leg 4-switch (2L-4S) and 3-leg 6-switch (3L-6S) are used for constructing the STATCOM system. Simulation studies carried out in the Matlab/Simulink environment are firstly described. Typical experimental results of basic control examples are presented to verify the feasibility of the 2L-4S STATCOM and the effectiveness of the proposed controllers.

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Keywords: Power system voltage control, Flexible ac transmission systems (FACTS), Static synchronous compensator (STATCOM), Space vector pulse width modulation.



go to top   Design and Implementation of a New ZVS Interleaved Forward-Flyback Converter Using an Integrated Transformer
         by M. Taheri, J. Milimonfared, S. H. Fathi, M. Hajizadeh
         Vol. 5. n. 3, pp. 909-918


Abstract - This paper proposes an interleaved active-clamping zero-voltage-switching (ZVS) forward-flyback converter using a single magnetic core. The presented topology is composed of an active-clamping forward converter parallel with an active-clamping flyback converter. The main switch of any converter also acts as auxiliary switch for the other one, so only two switches are required and there is no need to additional switches to achieve ZVS operation. Because of interleaved operation of the converter, the output current ripple will be reduced. Thus, the output choke and capacitor can be smaller. The transformers of converter are integrated into one magnetic core and center and outer legs are gapped. Due to the mutual influence of the coupling between the two transformers, input current ripple also can be reduced. According to the mentioned reasons, the proposed converter has high efficiency. Furthermore, the size of the converter is reduced and its power density increases. A prototype converter has been implemented and experimental results have been recorded with an ac input voltage of 85-135 Vrms, an output voltage 12V and output current 16A.

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Keywords: Active-clamping circuit, interleaved converter, integrated magnetic, zero-voltage switching.



go to top   Optimised Design and Analysis of a New Linear Switched Reluctance Actuator
         by M. R. A. Calado, S. J. P. S. Mariano, C. M. P. Cabrita

         Vol. 5. n. 3, pp. 919-926


Abstract - This paper proposes a procedure for the design of a new single-sided linear switched reluctance actuator (LSRA). First, an analytical analysis is established, using a proposed calculus sequence, to obtain electrical and mechanical parameters. After, a numerical analysis is developed, based on finite element method, to determine the effect of geometry changing, or the influence of excitation positions and current levels, in machine performance, prior to construction of a prototype. These two methods are then connected in order to proper change dimensional and performance parameters, allowing an optimised design of the machine. The theoretical traction forces, obtained as a result of the equivalent magnetic circuit co-energy variation analysis, for different relative positions between the primary and secondary parts of the machine, as well as for several excitation levels, are presented and compared with experimental results carried out by the authors, by using a prototype with 2 mm airgap. The actuator characterization allows the knowledge of proper coil excitation positions and current magnitude, for different practical applications. The LSRA experimental tests are presented, establishing thermal, electrical and mechanical limitations. The experimental stationary analysis, together with the previous analytical and numerical analysis, will be the starting point to the machine control strategies establishment.

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Keywords: Linear Switched Reluctance Actuator, Optimised Machine Design, Prototype Experimental Tests, Traction Force Analysis.


go to top   A New Approach for Transformer Loading Capability Assessment Based on Fuzzy Thermal Model
         by M. Savaghebi, A. Gholami, A. Vahedi, H. Hooshyar

         Vol. 5. n. 3, pp. 927-935


Abstract - Thermal stresses are the main factor of deterioration of transformer insulation. These stresses, which are originated from heavy loading, are more severe in the hot spot of transformer winding. So, the transformer loading capability is mainly restricted by the hot spot temperature.
In this paper, a new method is proposed for transformer dynamic loading capability assessment using fuzzy modeling. Firstly, the hot spot temperature is estimated by fuzzy thermal model and then is compared with the temperatures obtained by measurement and IEEE thermal model. Afterwards, the method of dynamic loadability assessment is described and implemented by the fuzzy model. Comparison between the results obtained by the fuzzy thermal model and the IEEE model demonstrates the usefulness of the fuzzy model application. Also, this fact is emphasized by an economic analysis.

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Keywords: Transformer Loading Capability, Insulation Loss of Life, Fuzzy Thermal Model, IEEE Thermal Model.



go to top   Axial Static Eccentricity Detection in Induction Machines by Wavelet Technique
         by Hamidreza Akbari, Jafar Milimonfared, Homayoun Meshgin-Kelk

         Vol. 5. n. 3, pp. 936-943


Abstract - In this work, multiresolution analysis of the stator startup current is carried out in order to detect the presence of axial static eccentricity in an induction motor. For this purpose, the discrete wavelet transform is applied and wavelet signals at different levels are studied. Data are obtained from simulations, using modified winding function approach, which allows forcing several kinds of faults in the machine, considering axial nonuniformity. For simulation of induction machine under axial nonuniformity conditions, this paper determines a modified model of induction machines. By means of the modified model, inductances of a three-phases squirrel-cage induction machine under axial nonuniformity conditions are calculated. Calculated inductances are used in a coupled electromagnetic model, for simulation of induction motor under healthy and faulty conditions. The results show the validity of the approach for detecting the fault and discriminating with respect to other failures.

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Keywords: Axial eccentricity, Winding function approach, Wavelet transform, Induction machine.



go to top   Novel DTC Based on SVPWM with utilizing all Feasible Voltage Vectors of Matrix Converter for Induction Motor Drives

         by Farhad Montazeri, Davood Arab Khaburi

         Vol. 5. n. 3, pp. 944-951


Abstract - This paper proposes a novel control method for DTC based on SVPWM by using all voltage vectors of matrix converters to give a constant torque switching frequency and reduce the torque ripple. The standard look up table for direct torque control by matrix converters is improved in order to include the small, medium and large voltage vectors of matrix converters. With the new look-up table and new hysteresis comparator with seven levels of output the system will differentiate between small, medium and large torque errors and consequently the electromagnetic torque ripples are reduced. The DTC scheme is characterized by the PI regulators and coordinates transformations and therefore allows to having a good torque control in both steady state and transient operating conditions. The superiority of the proposed method over the conventional methods that use matrix converter for DTC is proved by FFT and THD analysis and the simulation results demonstrate the effectiveness of this novel control strategy.

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Keywords: Direct Torque Control (DTC), Induction Motor, Matrix Converters, Space Vector pulse width Modulation (SVPWM).



go to top   A Probabilistic Approach for Power Transformer Dynamic Loading Capability Assessment
         by B. Shahbazi, M. Savaghebi, M. Shariati

         Vol. 5. n. 3, pp. 952-960


Abstract - Power transformers are among the most critical and expensive equipment of the power system. So, transformer proper loading has been an important issue in power system operation. In order to have a reliable estimate of transformer loading capability, it is necessary to consider the uncertainty of load and ambient temperature. To cover this mater, a probabilistic method for dynamic loading capability assessment is proposed in this paper. In this method, probability distribution functions of load and ambient temperature is determined and loadability assessment is carried out using Monte Carlo simulation. The proposed approach is illustrated by a case study on the load and ambient temperature practical data of a transformer equipped with a transformer online monitoring system.

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Keywords: Power Transformer, Dynamic Loading, Probabilistic Method, Montecarlo Simulation.



go to top   Design and Optimization of a Double-Sided Linear Induction Motor Based on Finite Element Method
         by Mehrdad Jafarboland, Abdolamir Nekoubin

         Vol. 5. n. 3, pp. 961-969


Abstract - Effective parameters on the performance of linear induction motors such as air gap, number of poles and the thickness of secondary must be selected and optimized to increase power efficiency and motor performance significantly. In this paper a double-sided linear induction motor in different condition by using MAXWELL3D software is designed and with finite element method is analyzed. For comparing analytical model and numerical model a linear motor by using MATLAB software is simulated. Then an optimization of the motor is done to maximize its efficiency. It is clear from the results that with determination of optimal value of effective parameters, power losses is decreased also performance of motor is improved and efficiency of linear motor is increased.

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Keywords: Air Gap, Number of Pole, Thickness of Secondary, Linear Motors, Optimization.



go to top   A Novel Algorithm Based on Wavelet and Parallel Neural Networks for Diagnosing Power Transformer Status
         by Tsao-Tsung Ma

         Vol. 5. n. 3, pp. 970-979


Abstract - This paper presents a new algorithm based on wavelet and parallel neural networks for diagnosing power transformer status. The proposed algorithm is developed by analyzing the energy distribution patterns derived from the inrush currents under various conditions, i.e., normal inrush currents, internal faults and insulation deteriorations. In this method, the discrete wavelet transform, a powerful tool in extracting information from the transient signals simultaneously in both time and frequency domains, is firstly applied to decompose the online detected inrush currents of the power transformer into a series of approximated and detailed wavelet components. Then, the energy distribution features of the wavelet components are calculated and employed to train the probabilistic neural networks to discriminate a variety of transformer internal status. The merit of this method is demonstrated by simulation of different faults and switching conditions on a power transformer using MATLAB/SIMULINK software. The simulated results clearly show that the proposed technique can accurately recognize various internal faults, insulation deteriorations and normal magnetizing inrush currents in power transformers. Also the proposed algorithm is tested with data practically collected from a real-life power transformer of Taiwan Power Company. Test results verify the feasibility and effectiveness of the proposed algorithm.

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Keywords: Power Transformer, Magnetizing Inrush Current, Status Monitoring System, Probabilistic Neural Network.



go to top   Hurst Parameter and Fractal Dimension Concept for Fault Detection in Electric Motors
         by S. İkizoğlu, R. Çağlar, S. Şeker

         Vol. 5. n. 3, pp. 980-984


Abstract - In this paper we aim to define the degradation of the bearings in electric motors related to parametric values. Aging tests of an electric motor are performed according to IEEE test procedures. The vibration signals of the bearings are acquired via accelerometers. This step is followed by the analysis of the data in the spectral frequency domain. Finally, the Hurst parameter is calculated as a measure of the degradation. Since there is a simple relationship between the Hurst parameter and the Fractal Dimension concept, the latter can be considered as another parametric approach to define the degradation. We recognize that the positive Hurst parameter in the healthy case changes to a negative value for the faulty case, which indicates that the degradation is produced by the aging process. The difference between the parameters for the healthy and faulty cases is a measure of the degradation.

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Keywords: Vibration Signal, Spectral Analysis, Hurst Parameter, Fractal Dimension, Condition Monitoring, Degradation, Electric Motor.



go to top   Assessment of the Hydrogenerators State, Based on their History of Life Analysis
         by Dan Zlatanovici, Rodica Zlatanovici, Cristinel Cicirone, Sorin Dumitrescu

         Vol. 5. n. 3, pp. 985-991


Abstract - The assessment is made based on the analysis of the hydrogenerator life history in a determined period of time; the analysis is based on a well organised informatised database comprising the events in the life history of the hydrogenerator. A points rating method is settled for the gravity of the defects and for the extent of the maintenance works, for the results of tests and for operating and design characteristics. The system of rating is unique, in the base of 5, with a score of 1 point for normal situations, 5 points for situations of maximum gravity and 2, 3 or 4 points for intermediate situations.The decisional criteria for assessment of the technical state depending on the total value of the conferred scores comprise 6 levels of state: new, very good, good, satisfactory, unstisfactory and severe. For the application of the method itself , list oof ebvents products must be made for hydrogenerator evaluated. The number of point for each event is assigned according to the catalog of events possible, and then the sum of these points is made.

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Keywords: Hydrogenerator, Defects,Testing Maintenance, Criteria, Aassessment.



go to top   Optimal Controller Designing for a Mechanical Coupling of Two Different Electric Motors
         by Mehrdad Jafarboland, Jawad Faiz

         Vol. 5. n. 3, pp. 992-1002


Abstract - Two different motors shafts mechanical coupling has some outstanding advantages such as: reduction of weight and volume of the system, improvement of system efficiency and multi-purpose application of motors. But, coupling of two motors with different ratings needs a complicated controller. The controller must adjust the speed and shares the load power between two motors. The previous controllers share the load power non-optimally; therefore this paper introduces a new controller that enables to share the load optimally between two motors over different speeds. This increases the efficiency of the system for wide range of speeds. The proposed optimal controller is designed and a prototype is built and its performance is simulated. Simulation results for under-water drive system are verified by experimental results.

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Keywords: Mechanical Coupling, Under-Water Traction System, Optimal Control, Multi-Machine Control, Control of Motor Speed.



go to top   New π Model Validation Approach to the Leakage Flux Transformer of a High Voltage Power Supply Used for Magnetron for the Industrial Micro-Waves Generators 800 Watts
         by M. Ould Ahmedou, M. Chraygane, M. Ferfra

         Vol. 5. n. 3, pp. 1003-1011


Abstract - The high voltage power supply for magnetron, used for the microwaves generators in industrial applications, is a classical design. This system is composed of a phase leakage flux transformer supplying a cell composed of a capacitor and a diode, which double the voltage and stabilize the current. A π quadruple model of this transformer is developed taking into account the saturation phenomena and the stabilization process of a magnetron current. Each inductance of the model is characterized by a non linear relation between flux and current that we obtain directly from the transformer’s data (magnetizing curves, geometry, etc.). In this paper, we present a new validation approach of this model, by MATLAB- SIMULINK® code at the nominal state, based on the comparison between experimental and simulated fluxes. The simulation curves match the experimental measurements as closely as expected. The results from SIMULINK and EMTP® (Electromagnetic Transient Program) code are also compared. The results’ analysis confirms the conservation law of fluxes and proves that the leakage flux in the shunt can not be ignored contrarily to the conventional transformer.

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Keywords: EMTP, High Voltage (HV), Generators, Magnetrons, Microwaves, Modeling, Power Supply, SIMULINK, Transformer.



go to top   Influence of Time Gap between Impact Loads on Torsional Dynamics of Generator Units
         by M. Mirošević, D. Sumina, N. Bulić

         Vol. 5. n. 3, pp. 1012-1021


Abstract - The paper analyzes the dynamics of generator units during the start-up of induction motor drives. A unique mathematical model of integral motor drives has been developed consisting of a diesel machine, a synchronous generator, and three non-regulated motor drives fed directly from generator unit terminals. The aim of this paper is to analyze the influence of time gap between starting moments of induction motors on the dynamics of diesel generator units. The mechanical system of a diesel machine generator set is modeled as a rotating system with two concentrated masses connected with an elastic coupling. The main objective of this paper is to take this elastic coupling into consideration and analyze torsional dynamics in the coupling.

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Keywords: Synchronous Generator, Induction Motor, Diesel Generator, Torsional Torque, Torsional Stresses, Electromagnetic Torque.



go to top   Transient Response Study on Transformer Windings Under Impulse Voltage Stresses
         by Hendri Masdi, Norman Mariun

         Vol. 5. n. 3, pp. 1022-1026


Abstract - The study reported in this paper was aimed to investigate transient response of power transformer when lightning current pass through its winding. Analysis of distribution voltage at the winding taps was done, both by experimental and numerical simulation, by applying IEC-71 standard current surge (8/20 µs impulse current and 1.2/50 µs impulse voltage). Transformer’s constants as: R, L, C were derived from the transformer construction, which consists of 9 winding layers at HV-side. The wave-shapes of the voltage across the winding sections were recorded. The response of the windings was then compared with results of a simulation using EMTDC/PSCAD. The simulation based on an RLC network model resulted in wave-shapes that are in good agreement to those of the experiment. Both results of the simulation and experiment show that the distribution of the impulse voltage across the windings is non linear, especially during the period of fraction of microseconds. Furthermore, results of the investigation show that a simple capacitance network model is sufficient for study of the impulse voltage distribution across transformer windings.

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Keywords: Transient Overvoltage, EMTDC/PSCAD, Transformer Model.



go to top   Design of a Series Hybrid Propulsion System for a Bimodal Tram
         by C. H. Bae, J. K. Mok, Y. S. Byun, K.W. Lee

         Vol. 5. n. 3, pp. 1027-1032


Abstract - A bimodal low-floor tram is developing to provide the flexibility of bus and the punctuality of trains together to the passengers. Its propulsion system is a series hybrid type using a set of CNG engine generator and Li-polymer battery.
The present paper presents the specifications of the propulsion system in the bimodal tram and how the propulsion system of the bimodal tram can be controlled. With using a computer simulation tool of hybrid vehicles, ADVISOR, the performance of the bimodal tram was investigated.

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Keywords: Series Hybrid Propulsion, Bimodal Tram.



go to top   SDTC-EKF Control of an Induction Motor Based Electric Vehicle
         by B. Tabbache, A. Kheloui, M. E. H. Benbouzid, N. Henini

         Vol. 5. n. 3, pp. 1033-1039


Abstract - This paper presents the experimental implementation of sensorless direct torque control of an induction motor based electric vehicle. In this case, stator flux and rotational speed estimations are achieved using an extended Kalman filter. Experimental results on a test vehicle propelled by a 1-kW induction motor seem to indicate that the proposed scheme is a good candidate for an electric vehicle control.

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Keywords: Sensorless Direct Torque Control (SDTC), Extented Kalman Filter (EKF), Electric Vehicle (EV), DSP TMS320LF2407.



go to top   Using Grey Model to Predict Lithium-ion Battery Discharge Behavior
         by Chuan-Sheng Liu, Liang-Rui Chen

         Vol. 5. n. 3, pp. 1040-1044


Abstract - In this paper, the study of Li-ion battery discharge voltage predicting using Grey model is presented. A test-bed for the battery discharge predicting is designed and devised. By utilizing this test-bed, the discharge condition for discharging Li-ion battery can be easily set and the data of the discharged Li-ion battery can be simultaneously obtained. Experimental results show that the GM(1,1) Grey model can precisely predict the Li-ion battery voltage curve as theory predicts. The result is greatly helpful for engineers to design a Grey-Predicted Battery Monitoring System (GP-BMS).

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Keywords: Lithium-ion Battery, Discharge.



go to top   Determination of the Etching Rate from the Silicon Symmetry Properties by Extension of the Level Set Method
         by M. Radmilović-Radjenović, B. Radjenović

         Vol. 5. n. 3, pp. 1045-1052


Abstract - Implementation of the level set method for the case of non-convex Hamiltonians is illustrated by the three dimensional simulation (3D) of the profile evolution during anisotropic wet etching of silicon Some aspects of the silicon wet etching process are discussed. The angular dependence of the etching rate has been derived on the base of the silicon symmetry properties, by means of the interpolation procedure using experimentally obtained values of the principal directions in KOH solutions. In addition, detailed analysis of the obtained simulation results for some interesting initial 3D shapes (sphere and cube) are presented.

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


Keywords: Level Set Method, Etching Rate, Simulation.



go to top   Distributed Memory Parallel Transient Stability Analysis on a PC Cluster with Ethernet
         by Gürkan Soykan, Alexander J. Flueck, Hasan Dağ

         Vol. 5. n. 3, pp. 1053-1060


Abstract - On-line transient stability analysis is a necessity for real-time power system control and security. Parallel processing is a natural technology for achieving real-time solution performance. This paper presents a parallel-in-space algorithm based on a multi-level partitioning scheme in a distributed memory cluster environment. The main aim of the research is to decrease the wallclock time of transient stability analysis of large scale power systems by leveraging open source software and commodity off the shelf hardware of a Linux PC cluster. The proposed solution algorithm focuses on speeding up the transient stability simulation by partitioning via METIS the linearized update solution process of the Very Dishonest Newton Method for solving the differential-algebraic equation system. Results are presented for two power systems: 1) 3493 buses, 844 generators, 6689 branches and 2) 7935 buses, 2135 generators, 13624 branches. The simulations were run on a small Linux-cluster with a 100 Mbit/s ethernet interconnect, which is cheaper than any specially constructed parallel computer. By tuning vertex weights, the performance of the partition strategy can be improved relative to the no-weight case. The proposed method easily can be adapted by commercial packages and used in various parallel environments, including multicore architectures with non-uniform memory access.

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Keywords: Distributed Memory, Multi-level Partitioning, Parallel Computing, Sparse Linear Solver, Transient Stability Analysis.



go to top   Human Identification and Localization Using Active Capacitive RFID Tags and an Electric Field Floor Sensor
         by Henry Rimminen, Matti Linnavuo, Raimo Sepponen

         Vol. 5. n. 3, pp. 1061-1068


Abstract - In this study an active capacitive RFID tag embedded in a shoe was developed. The tags are identified and located with an existing near field imaging (NFI) floor sensor. The NFI system can detect the location of a person in an indoor environment, but does not provide identification. The goal was to identify a person when he or she enters a room. This is used to identify staff in nursing homes that are already equipped with the NFI floor sensor. The tag alters the impedance seen by the floor using ASK modulation. Adapted FM0 encoding with a symbol rate of 200 bit/s was used. An SNR of 17 was reached at floor level and the read range was 5 mm. With fixed location the success rate was 100% and the latency was 0.4 s. With random locations the performance was 93%. A two-week test period in a nursing home showed that a 93% success rate can also be achieved in everyday use. The results promote the intended use.

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Keywords: Capacitive RFID, Electric Field Measurement, Indoor Positioning.



International Review of Electrical Engineering - Papers- Part B



go to top   Optimal Variable-gain Neural Network-Based UPFC Controller by Means of Differential Evolution Algorithm

         by S. Jazebi, H. R. Baghaee, G. B. Gharehpetian

         Vol. 5. n. 3, pp. 1069-1077


Abstract - This paper presents a modified control strategy for a Unified Power flow Controller (UPFC). UPFC is one of the most promising FACTS devices to control power system oscillations and enhancing the transient stability. Power systems, always contains parametric uncertainties which must be considered in controller designs. Variations of power system operating conditions could move parameter region of UPFC controllers in its parameter space. Focus of present study is to investigate two main functions: (1) prevent interactions caused by inappropriate setting of UPFC controller's parameters by using differential evolution algorithm; (2) how to conclude the optimized controller's parameters in the model preventing delays caused by DEA slow convergence response. In this paper, a novel gain-varied control for UPFC based on artificial neural network (ANN) and k-means clustering algorithm is proposed and compared with a conventional PI controller. Simulation results developed in MATLAB-SIMULINK environment verify the viability and effectiveness of proposed control scheme in comparison with conventional PI controller.

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Keywords: UPFC, Power System Stability, Inter-area Oscillations, Differential Evolution Algorithm, Artificial Neural Networks.



go to top   New Hybrid Controller Based on Sliding Mode Modulation for Inverter-Based DG with Existing Fast Load Changes
         by M. Davari, A. R. Pourshoghi, M. R. Hajiahmadi, G. B. Gharehpetian, S. H. Fathi

         Vol. 5. n. 3, pp. 1078-1086


Abstract - The controller of Voltage Source Inverter (VSI) is the important part of inverter-based Distributed Generation (DG) systems. In this paper, in order to control the loads with fast dynamics, a new controller has been proposed based on Sliding Mode Modulation (SMM) feedback linearization method. The new controller has been designed using nonlinear average state space model of VSI and network. Considering the variable structure of VSI, the state trajectory controller with sliding mode controller, named hybrid control, have been combined, in this paper. Also, a fast fuzzy PLL for the proposed controller has been designed. The real time simulation of the proposed system shows that it can track the loads with fast dynamic better than other controllers.

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Keywords: Voltage Source Inverter, Distributed Generation, Feedback Linearization, Sigma-Delta Modulation, Real Time Simulator.



go to top   Design of Fuzzy Based UPFC Damping Controllers Using Particle Swarm Optimization Algorithm
         by Tsao-Tsung Ma

         Vol. 5. n. 3, pp. 1087-1094


Abstract - This paper describes the design of a Takagi-Sugeno type fuzzy controller for the unified power flow controller (UPFC) to enhance the dynamic stability of power systems. The proposed fuzzy controller uses a regular rule base structure and the Takagi-Sugeno type defuzzification algorithm which offers the possibility of optimally designing either linear or nonlinear control gains over a wide operating range. This type of fuzzy controllers is expected to be robust and effective in complex control applications, e.g. damping electromechanical oscillations of multi-machine power systems. To achieve the best control results, a direct search optimization technique, particle swarm optimization (PSO) algorithm is used to find the best parameters for the designed UPFC damping controllers. Nonlinear time domain simulations on a two-area, multi-machine power system embedded with a UPFC are carried out. Typical simulation results including the comparison with the conventional PI type regulators used for the same UPFC control objectives are presented to validate the superior performance of the proposed control scheme.

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Keywords: Flexible AC Transmission Systems, Unified Power Flow Controller, Power Systems Damping Control, Particle Swarm Optimization.



go to top   Enhancement in Static Security Assessment for a Power System Using an Optimal Artificial Neural Network
         by A. AL-Masri, M. Z. A. Ab Kadir, H. Hizam, N. Mariun, A. Khairuddin, J. Jasni

         Vol. 5. n. 3, pp. 1095-1102


Abstract - Artificial Neural Network (ANN) is addressed as a tool for the power system security assessment. The goals of this study are to test the reliability of ANN in Static Security Assessment (SSA) by determining the security level due to changes in aspects of contingencies and load increases and to compare the results of ANN and Load-Flow models in terms of accuracy and computational time. The proposed method has been successfully tested on 5-bus and IEEE 30-bus test systems. ANN can provide the security states of the current operating point and enhanced to be faster and more accurate.

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Keywords: Neural Network, Back Propagation (BP), Power System, Load-Flow, Security Assessment, Contingencies.



go to top   Improvement of Power System Stability with Fuzzy Logic Based IPFC
         by Alivelu M. Parimi, Irraivan Elamvazuthi, Nordin Saad

         Vol. 5. n. 3, pp. 1103-1109


Abstract - The Interline Power Flow Controller (IPFC) is one of the recently developed Flexible AC Transmission System (FACTS) devices. The IPFC is realized by two voltage source converters connected by a common DC link. Fuzzy logic (FL) controllers are designed to operate the controls of IPFC for damping the power system oscillations. The proposed FL controller uses machine speed and its integral as its inputs and the output of the controller controls the input signal of the IPFC. The effectiveness of the fuzzy controller is tested on a single machine infinite bus power system operating with an IPFC for various disturbances and operating conditions. The performance of the proposed controller is compared with the conventional controller of the IPFC and the results of time-domain simulation studies show that the designed FL controller provides enhanced damping of power system oscillations.

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Keywords: Flexible AC Transmission System, Fuzzy Logic Controller, Interline Power Flow Controller, Power System Oscillations.



go to top   Power Systems Load Flow & State Estimation: Modified Methods and Evaluation of Stability and Speeds Computing
         by A. Thabet, S. Chniba, D. Gaetan, M. Boutayeb, M. N. Abdelkrim

         Vol. 5. n. 3, pp. 1110-1118


Abstract - In this paper, we present a study and evaluation of modified methods of calculating the load flow and the state estimation of power systems. We present basic algorithms and its modified versions, with a comparative study and evaluation of stability analysis and the various criteria of CPU time, computing time, memory capacity and the number of iteration in order to optimize the computing speed. The study is applied on IEEE 13 and 24 buses test systems.

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Keywords: Computing Time, Load Flow, Power Systems, Stability, State Estimation.



go to top   Determination of Best Location of FACTS Devices for Damping Oscillations
         by N. Magaji, M. W. Mustafa

         Vol. 5. n. 3, pp. 1119-1126


Abstract - This paper proposes a residue factor method to find the optimal location of the FACTS controllers. Three types of FACTS controllers have been considered, which include thyristor-controlled series compensator (TCSC), Static Var compensator (SVC) and unified power flow controller (UPFC). The effectiveness of this controller depends on its optimal location and proper signal selection in the power system network. The proposed residue factor is based on the relative participation of the parameters of FACTS controller to the critical mode. A simple approach of computing the residue factor has been proposed, which combines the linearised differential algebraic equation model of the power system and the FACTS input and output equations. The placements of FACTS controllers have been obtained for the base case and for the dynamic critical contingences. The effectiveness of the proposed method of placement is demonstrated on 11 bus system and New England 39 Bus system.

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Keywords: FACTS, Power System Oscillations, Linear Models, Eigenvalues, Residues Factors.



go to top   QFT-based Load Frequency Controller Design with GA-based Optimized Bias Coefficients
         by A. Sakhavati, G. B. Gharehpetian, S. H. Hosseini

         Vol. 5. n. 3, pp. 1127-1137


Abstract - This paper presents the design method of a robust controller for the Load Frequency Control (LFC) problem, which is based on QFT (Quantitative Feedback Theory). Using this method, it is possible to obtain robustness against power system uncertainties. GA (Genetic Algorithm) has been used to optimize the frequency bias coefficients of power system, too. The simulation results of a two-area power system show that the system response with the proposed controller has a better transient response than the PI controllers.

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Keywords: Load Frequency Control, Bias Coefficients, Quantitative Feedback Theory, Robust Control, Genetic Algorithm.



go to top   AIPSO-SA Based Approach for Power System Oscillation Damping with STATCOM
         by A. Ajami, H. Asadzadeh

         Vol. 5. n. 3, pp. 1138-1150


Abstract - Power system dynamic stability enhancement by STATCOM-based stabilizers is thoroughly investigated in this paper. This study presents singular value decomposition (SVD) based approach to assess and measure the controllability of the poorly damped electromechanical modes by STATCOM different control signals. The supplementary controller of STATCOM to damping the low frequency oscillation in a weakly connected system is presented. Individual designs of the STATCOM controller using adaptive improved particle swarm optimization hybrid with simulated annealing (AIPSO-SA) are discussed. In this paper, the STATCOM-based controllers' parameters are optimized over a wide range of operating conditions and system parameter uncertainties (multi point tuning) in order to have robust stabilizers. The effectiveness of proposed controller on enhancing dynamic stability is tested through eigen value analysis and time domain simulation. Also nonlinear and electrical simulation results show the validity and effectiveness of the proposed control schemes over a wide range of loading conditions. It is also observed that the proposed STATCOM-based damping stabilizers enhance greatly the power system transient stability.

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Keywords:  Power System Stability, Power System Oscillation, STATCOM, Dynamic Modeling, AIPSO-SA.



go to top   Application of Evolutionary Algorithm and Classifier System in Optimisation of Electric Power Distribution Networks Post-fault Configuration
         by S. Filipiak

         Vol. 5. n. 3, pp. 1151-1158


Abstract - The description of the proposed algorithm together with the calculation procedures prepared for the considered problem has been included. Exemplary calculations for a selected medium-voltage network system have been presented in the final part of the paper. The elaborated method uses the theoretical background of genetic-based machine learning systems. The method shows the ability to collect experience on the base of information on faults, occurred or simulated in the power distribution systems. In the elaborated method the decisive variables, essential from the network operation reliability point of view, described with the use of fuzzy sets theory, have been taken into account in the formulated objective function. A method enabling to formulate scenarios of network configuration changes (at changes in network operation conditions) has been characterised in the paper.

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Keywords: Computer Modelling and Computer Simulation, Evolutionary Algorithms, Intelligent Systems, Distribution Power Networks.



go to top   The Improvement of Voltage Sags Pattern Approach to Locate a Fault in Distribution Network
         by H. Mokhlis, A. H. A. Bakar, D. N. A.Talib, Hasmaini Mohamad

         Vol. 5. n. 3, pp. 1159-1164


Abstract - This paper describes an improvement of a faulted section identification method. The improvement has made the method not only able to identify a faulted section, but at the same time calculate fault distance from one-end of the faulted section. By having this new feature, the locating fault time can be further reduced. The method has been tested on an actual underground rural distribution network feeder with all type of fault. The results show that most faults can be located by the first attempt and with high accuracy of fault distance. Only few faulted sections found by the second attempt. Since the proposed method is using only voltage sag data, monitored at the primary substation, the method is considers economical to be implemented for a rural distribution network.

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Keywords: Distribution network, faulted section, fault location, voltage sags.



go to top   Fault Location for a Series Compensated Transmission Line Based on Wavelet Transform and an Adaptive Neuro-fuzzy Inference System
         by El Sayed Mohamed Tag Eldin

         Vol. 5. n. 3, pp. 1165-1171


Abstract - Fault diagnosis is a major area of investigation for power system and intelligent system applications. This paper proposes an efficient and practical algorithm based on using wavelet MRA coefficients for fault detection and classification, as well as accurate fault location. A three-phase transmission line with series compensation is simulated using MATLAB software. The line currents at both ends are processed using an online wavelet transform algorithm to obtain wavelet MRA for fault recognition. Directions and magnitudes of spikes in the wavelet coefficients are used for fault detection and classification. After identifying the fault section, the summation of the sixth level MRA coefficients of the currents are fed to adaptive neuro-fuzzy inference system (ANFIS) to obtain accurate fault location. The proposed scheme is able to detect all types of internal faults at different locations either before or after the series capacitor, at different inception angles, and at different fault resistances. It can also detect the faulty phase(s) and can differentiate between internal and external faults. The simulation results show that the proposed method has the characteristic of a simple and clear recognition process. We conclude that the algorithm is ready for series compensated transmission lines.

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


Keywords: Adaptive Neuro-Fuzzy Inference System (ANFIS), Series Compensated Transmission Lines, Fault Location, Fault Recognition Traveling Waves, Wavelet Transforms.



go to top   A New Coordinated Approach to Load Shedding in Integrated Transmission and Distribution Systems
         by Ahmadreza Malekpour, Alireza Abbasi, Alireza Seifi

         Vol. 5. n. 3, pp. 1172-1182


Abstract - Bulk power systems are composed of hybrid transmission and distribution networks, while traditionally, transmission and distribution load shedding is studied and developed separately. In order to achieve a global consistent load shedding solution, the transmission and distribution networks are studied simultaneously in this paper. A novel master–slave-splitting (MSS) iterative method is developed for calculating large-scale and integrated load shedding (ILS) problem. In the MSS method, with introducing the boundary fictitious values, the ILS problem of large scale is split into a transmission load shedding and many distribution load shedding sub-problems of small scale. Numerical results on a sample transmission and distribution test network show the satisfactory of proposed approach.

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


Keywords: Integrated Load Shedding (ILS), Transmission System, Distribution System, Energy Management System (EMS), Distribution Management System (DMS).



go to top   Automatic Generation Control of a Multi-area Power System Using Bacterial Foraging Algorithm

         by H. Noormohamadi, S. Niknafs, A. A. Gharaveisi

         Vol. 5. n. 3, pp. 1183-1188


Abstract - Automatic Generation Control (AGC) is a means of automatically controlling the outputs of power-generating units to accomplish economic dispatch, and maintain system frequency and power flows over tie lines at desired levels. In order to maintain the frequency in nominal boundaries, some parameters must be adjusted. In an automatic generation control system the most important parameter is the coefficients of conventional integral controllers. This paper deals with automatic generation control of a multi-area non-reheat thermal system. For optimization the coefficients of the integrators, the Bacterial Foraging Algorithm (BFA) is proposed. Simulation results can show clearly a desirable performance of the proposed system within a wide range of variation for specified parameters and indicate the effectiveness of the proposed algorithm for AGC system destination.

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Keywords: Automatic Generation Control (AGC), Load Frequency Control, Multi-area Power System, Bacterial Foraging Algorithm (BFA).



go to top   Transmission Loss Minimization Using Evolutionary Programming Considering UPFC Installation Cost

         by N. R. H. Abdullah, I. Musirin, M. M. Othman

         Vol. 5. n. 3, pp. 1189-1203


Abstract - A critical factor effecting power transmission systems today is the power flow control technique. The increment of load variation in a power transmission system can lead to potential failure on the entire system as the system has to work under a stressed condition and various contingencies. Thus, the Flexible AC Transmission System (FACTS) are integrated in power system to control the power flow in specific lines and improve the security of transmission line. This paper presents Evolutionary Programming (EP) technique for solving reactive power problem incorporating Unified Power Flow Controller (UPFC). The objective of the study is to employ EP optimization technique for loss minimization along with the installation cost calculation and voltage profile monitoring when a power transmission system is subjected to (N-1) contingency. The location of the UPFC installation is determined based on a pre-developed voltage stability index. The UPFC devices are installed in the system in order to enhance the system security; performed on the IEEE 30-bus RTS for several loading conditions. The simulations results are compared with those obtained from the Artificial Immune System (AIS) technique in the attempt to highlight its merit.

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


Keywords: UPFC, Loss Minimization, EP, AIS, (N-1) Contingency.



go to top   Experimental Studies of Load’s Influence on AC Voltage Switches During Endurance Tests

         by L. Chaâbane, H. Jenhani, Z. Ettouzri, M. Abdellaoui

         Vol. 5. n. 3, pp. 1204-1208


Abstract - The important demand in the sense of safety and reliability in the area of domestic applications requires, for the improvement of switch devices, deeper knowledge on the influence of loads, particularly those including a capacity. These loads simulate fluorescent lamps (IEC 60-669-1). Switches shall withstand, without excessive wear or other harmful effect, the mechanical, electrical and thermal stresses occurring in normal use during their lifetime. The purpose of this work is the study, during endurance tests, of the influence of inductive load and inductive one witch including a capacity, on arc characteristics and contacts surface. The experimental tests have been done on switches with AgNi contacts and have been carried out under a rated alternative voltage of 250V and a rated current of 10A, for different numbers of opening/closing operations (from 500 to 5000). The main result shows that the peak arc current value for load containing a capacity reaches very high values at closing operations and is increasing with the number of operations. For inductive loads, it doesn’t exceed twice the maximum rated current value and stays relatively constant at closing and opening operations. The observation of contacts surface with SEM after different numbers of operations, shows far more important and different damage of contacts with loads containing a capacity.

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Keywords: Switch, Alternative Current, Inductive Load, Electrical Arc, Endurance Test.



go to top   Adaptive Distance Relay during Voltage Collapse
         by Ahmad Farid Bin Abidin, Azah Mohamed, Hussain Shareef

         Vol. 5. n. 3, pp. 1209-1217


Abstract - This paper presents a new technique to prevent the false distance relay tripping during voltage instability and voltage collapse by integrating the adaptive setting of zone 3 distance relay, rate of change of voltage (dV/dt) and voltage stability index (VSI). The existing dV/dt approach is not able to differentiate between a fault and near voltage collapse condition and may initiate the false tripping signal. Therefore, a rigorous indicator, VSI is proposed as an additional relay feature to prevent such signals to be initiated. The performance of proposed technique is evaluated by comparing it with the dv/dt and the combination of dv/dt with system status indicator (SSI).

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Keywords: Adaptive Setting, Distance Relay, Fault, Voltage Collapse.



go to top   Reliability Centered Maintenance of the Circuit Breakers
         by Maricel Adam, Adrian Baraboi, Catalin Pancu, Adrian Pleşca

         Vol. 5. n. 3, pp. 1218-1224


Abstract - The diagnosis of the technical state of circuit breakers is of great actuality. The necessity of diagnosing is imposed by the need of adaptation the maintenance intervals to the real technical state of the circuit breakers. In this paper is presented a possibility for modeling of operation reliability of circuit breakers. Starting from the primary failures of the circuit breakers, theirs reliability model has the following components: operating mechanism subsystem; extinguishing chamber subsystem; unexpected failures subsystem; construction and montage failures subsystem; the subsystem of the explanatory variables. For the reliability model and each subsystem of this model, the probability functions are calculated. On the basis of reliability model is realized a software of predictive maintenance of the circuit breakers.

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


Keywords: Circuit Breaker, Reliability Model, Predictive Maintenance.



go to top   An Arcless Current Interruption Technique via Application of Resistive and Liquid Metal Contacts
         by P. Pourmohamadiyan, K. Niayesh, H. Mohseni

         Vol. 5. n. 3, pp. 1225-1235


Abstract - In this paper, theoretical and experimental studies of an arcless current interruption technique are presented. The introduced method eliminates the switching arc and its consequences through application of liquid metal and resistive contacts. First, the solid-liquid contact system is analyzed and the basic phenomena related to arcless switching are elaborated. Then the design requirements are recognized and are converted to a set of mathematical expressions and accordingly the design parameters are determined. The major electromagnetic quantities like current density distribution, magnetic flux density and the force are obtained by a FEM solver and the calculated force is used in numerical calculations of motion simulation. Finally, the designed structure is evaluated through a set of experiments which test the performance of the switch especially in the arcless current interruption.

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Keywords: Arcless Current Interruption, Liquid Metal Contact, Inherently Controlled Switch.



go to top   Testing of Power Electrical Apparatus Using Modular High Current Source
         by Adrian Pleşca, Alina Scîntee

         Vol. 5. n. 3, pp. 1236-1243


Abstract - As some workshops and profile sections running tests over the electrical apparatus of the modern production systems, interest in adjustable current and voltage modular sources is motivated. Such modular power source consists of a voltage-current single-phase transformer with independent ferromagnetic modules, each with its own primary winding and a common secondary winding. In this paper, a three-phase high current source is described and its primary voltage vs. secondary current characteristic is presented. Using this type of power current source, the low voltage circuit breakers have been tested in order to check their protection characteristics.

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


Keywords:  Circuit Breakers, High Current Source, Protection Characteristic.



go to top   Lightning Incidence of Wind Farm Underground Power Cable Networks
         by Petar Sarajčev, Ranko Goić

         Vol. 5. n. 3, pp. 1244-1254


Abstract - This paper presents a general procedure for the estimation of the lightning incidence of underground power cable networks, in this particular case, associated with modern wind farms. The modern wind farms are often comprised of several dozens of wind turbines mutually interconnected through an extended medium voltage underground power cable network. It is unfortunate coincidence that these wind farms are often located in regions of increased lightning activity, which stems from the fact that regions with high wind potential often coincide with regions of increased thunderstorm activity. Furthermore, wind farm locations could additionally be accompanied with the high soil resistivity of the terrain, which would provide favorable conditions for the lightning-initiated damage of the associated wind farm cable networks. Hence, it is considered prudent to estimate the lightning incidence of the wind farm underground power cable networks and, if necessary, provide additional cable-damage mitigation techniques combined with the appropriate overvoltage protection measures.

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


Keywords: Lightning, Log-normal Distribution, Underground Cables, Wind Farm.



go to top   High Impedance Fault Detection Using Duffing Oscillator and FIR Filter
         by Abolfazl Jalilvand, Hossein Kazemi Kargar, Hadi Fotoohabadi

         Vol. 5. n. 3, pp. 1255-1265


Abstract - The high impedance fault detection in power system is one of the hard works and if the fault does not clear then the power system may get into damage. In this paper a new and effective algorithm is proposed for arcing fault detection in distribution network with the application of FIR filter bank and duffing oscillator. The method detects the changes on the low order harmonics exist in the line current by identifying the transformation of the Duffing oscillator from chaotic state to large periodic and vice versa, due to inception of arcing fault. Also the paper, present a new method based on the frequency spectrum analysis to automatically identify the state transformation of duffing oscillator. The simulation results show that the proposed method can successfully distinguish the high impedance fault from most normal operations.

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Keywords: High Impedance Fault, FIR Filter, Duffing Oscillator, Frequency Analysis.



go to top   Analysis on Partial Discharge Localization Using UHF Combined with Acoustic Method in GIS
         by Junhua Liu, Chengjun Huang, Yong Qian, Xiuchen Jiang

         Vol. 5. n. 3, pp. 1266-1270


Abstract - To improve the accuracy of PD localization and enhance the maintenance efficiency of gas insulated switchgear (GIS), a partial discharge (PD) localization method based on Ultra High Frequency (UHF) combined with acoustic technique is proposed in this paper. The PD source is located in a rough range with UHF method firstly, which usually consists of two or three chambers. Secondly, the PD source can be located quickly and accurately by detecting the acoustic and UHF signals simultaneously. As the PD localization method detects UHF and acoustic signals of PD synchronously, it can exclude the interference and confirm PD signal more effectively. The laboratory experiment and on-site application results both show that the PD localization method using UHF combined with acoustic method can be used in online GIS PD localization effectively and precisely.

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Keywords: Gas Insulated Switchgear, Partial Discharge, Insulation Defect Localization, UHF Combined with Acoustic.



go to top   Anti-theft Grounding System for Industrial Application
         by H. Ahmad, M. A. B. Sidik, K. Y. Lau

         Vol. 5. n. 3, pp. 1271-1276


Abstract - Grounding systems for industrial applications are prone to theft. This is true for telecommunication receiving, transverse and repeater towers. They are erected along highways, urban areas and residential areas to provide more coverage to users and customers. Material which is popularly used for grounding system is copper. Copper conductor has been widely used in grounding system due to its high conductivity and good resistance to underground corrosion. However, copper is a very expensive material and its recycled value is also attractive. This resulted in high cost of grounding system. For the pasts few years telecommunication utilities’ grounding system copper material are subjected to theft when installed as grounding conductor. In order to prevent the grounding system from being stolen and to reduce the cost of grounding system, this study proposed the use of galvanized steel conductor to replace copper conductor in grounding system. Galvanized steel conductor does not suffer from theft issue faced by copper conductor. Since the conductivity of galvanized steel is not as good as copper, backfills consisting of peat soil and oil palm ash are added as parts of the grounding system to improve the overall conductivity of the proposed grounding system resistance value. However to cater for high current transfer capability of the galvanized steel diameter can be increased. The anti-theft grounding system which basically use galvanized steel with soil enhancement by means of using peat soil and oil palm ashes was proven to be capable of providing reasonably low resistance value of grounding system (better than copper grounding) for monitored period of 10 months while reducing the cost of the system and preventing theft.

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Keywords: Grounding System, Anti-theft Grounding, Galvanized Steel Grounding, Palm Ashes.



go to top   An ANFIS Based Approach and Finite Element Method for Measuring the Electric Conductivity
         by N. Mohdeb, M. R. Mekideche, T. Hacib

         Vol. 5. n. 3, pp. 1277-1284


Abstract - Estimating of electric conductivity parameter of the metallic walls from measured effective properties is an important problem in industrial engineering. In general, this problem of estimation is called inverse electromagnetic problem. In this research, a new hybrid approach is presented for the identification of electric conductivity in non-destructive evaluation. Adaptive neuro-fuzzy inference system and 2D-finite element method (2D-FEM) were used. In the proposed approach, finite element simulations are carried out to build up a database which will be used to train ANFIS network. The detected signal of the magnetic induction at sensor position is selected as input of the trained ANFIS model. The electric conductivity is the output parameter of the hybrid network. The trained ANFIS are experienced using the set of validation data. The ANFIS is presented so as to construct a good approximation to the nonlinear relationship between the physical property and the detected signal at sensor position. Performance of the trained ANFIS network was compared with the multi-layer feed-forward network MLP model.

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Keywords: Finite Element Method, Neuro-Fuzzy Inference System, Inverse Problem, Neural Network.



go to top   A Review of Statistics on Lightning Currents in Relation to the Lightning Incidence of New-Generation Wind Turbines
         by Petar Sarajčev

         Vol. 5. n. 3, pp. 1285-1296


Abstract - This paper provides a review of current issues, pertaining to the statistical depiction of lightning currents and in relation to the lightning incidence of modern, new-generation wind turbines. Lightning is a stochastic natural occurrence, described by the log-normal distribution. It can be divided into upward- and downward-initiated lightning, which could be further subdivided into the positive and negative polarity; the polarity being that of the charge transferred from the cloud to the ground. Significant differences exist between positive and negative lightning currents, as well as between upward- and downward-initiated lightning strikes. Additionally, some parameters of the lightning currents are statistically correlated, e.g. amplitude and front duration. All these features are addressed in this paper. Furthermore, it has been established that wind turbines – as tall and exposed structures – are rather prone to lightning strikes. With heights exceeding 100 meters they initiate their own upward lightning to some extent, as will be hereafter illustrated. This bears consequences on the wind turbine lightning incidence and will subsequently have influence on the selection of lightning currents pertaining to their overvoltage protection analysis.

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


Keywords: Lightning, Log-normal Distribution, Correlation, Wind Turbine.



go to top   A Market Clearing Method with Consideration of Power Generation Response Reliability
         by M. Najafi, M. Ehsan, M. Fotuhi-Firuzabad, A. Akhavein

         Vol. 5. n. 3, pp. 1297-1306


Abstract - A method for clearing energy and reserve market in an aggregated framework is presented in this paper. The objective function of the optimization problem considers offered costs for energy and reserve requirements, the cost of nondelivery energy and the cost of nondelivery reserve. Incorporating these costs in the objective function, the proposed algorithm can obtain a solution in which the market required energy and reserve capacities are assigned to generating units with lower costs and higher response reliability. A new method based on optimal selection of nondelivery compensation alternatives is proposed to determine the mentioned costs. The proposed procedure provides incentives for generating companies to improve their reliability and have higher share in the market. A test system is applied to show effectiveness of the proposed method.

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


Keywords: Aggregated Framework, Clearing Method, NonDelivery Energy Cost, NonDelivery Reserve Cost, Response Reliability.



go to top   A New Approach for Solving Profit-Based Unit Commitment Problem in Competitive Electricity Market
         by M. J. Sirizi, M. M. Ardehali, M. E. Nazari

         Vol. 5. n. 3, pp. 1307-1316


Abstract - This study presents a new approach for solving profit-based unit commitment (PBUC) problem in a day-ahead competitive electricity market. The new approach benefits from deterministic mathematical procedures and the uncertainty and probabilistic behavior inherently associated with evolutionary methodologies such as genetic algorithm and particle swarm optimization are avoided and, as a result, the optimum solution found are same in each simulation run. To solve the PBUC problem, a fitness function (FF) is defined and the optimum power of each generating unit that maximizes the FF is determined (FF*). Among all generating units, the least-cost option for generating power at each hour is determined and Then, generating unit priority is specified based on FF*s. Finally, by considering hourly power price, non-profitable generating units are switched OFF, final results of PBUC are determined, and total profit is calculated. The proposed approach is applied to a 10-unit power system and in addition to a very short processing time, it is found that proposed approach results in 3.21% higher profit as compared with the Tabu search method. To verify the efficiency of proposed approach in large-scale PBUC problem, the simulations included test runs for 20, 40, 60, 80 and 100 unit systems and the results are presented.

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


Keywords: Electricity market, Power price, Profit-based unit commitment, Restructured power system.



go to top   Risk Aversion in a Mixed-Integer Nonlinear Approach to Support Decision-Making for a Hydro Power Producer
         by J. P. S. Catalão, H. M. I. Pousinho, V. M. F. Mendes

         Vol. 5. n. 3, pp. 1317-1323


Abstract - In this paper, a mixed-integer nonlinear approach is proposed to support decision-making for a hydro power producer, considering a head-dependent hydro chain. The aim is to maximize the profit of the hydro power producer from selling energy into the electric market. As a new contribution to earlier studies, a risk aversion criterion is taken into account, as well as head-dependency. The volatility of the expected profit is limited through the conditional value-at-risk (CVaR). The proposed approach has been applied successfully to solve a case study based on one of the main Portuguese cascaded hydro systems.

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


Keywords: Decision Support, Hydro Power Producer, Mixed-integer Nonlinear Programming, Risk Aversion.



go to top   Investigation on the Development of Bidding Strategies for a Wind Farm Owner
         by H. M. I. Pousinho, V. M. F. Mendes, J. P. S. Catalão

         Vol. 5. n. 3, pp. 1324-1329


Abstract - In this paper, the development of bidding strategies is investigated for a wind farm owner. The optimization model is characterized by making the analysis of scenarios. The proposed approach allows evaluating alternative production strategies in order to submit bids to the electricity market with the goal of maximizing profits. The problem is formulated as a linear programming problem. An application to a case study is presented.

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


Keywords: Bidding Strategies, Profit, Scenarios, Wind Power.



go to top   Design of an Adaptive Preheating Time Electronic Starter for Dimmable Magnetic Ballast System
         by Liang-Rui Chen, Chuan-Sheng Liu

         Vol. 5. n. 3, pp. 1330-1335


Abstract - Based on the environmental consideration, a novel central dimming system with magnetic ballast driven lighting system, called Dimmable Magnetic Ballast System (DMBS), was presented to replace the electronic ballast driven lighting system. To make the DMBS work in a wide rang input voltage for dimming, a cost competitive circuit of an adaptive preheating time fluorescent lamp electronic starter is proposed in this paper. In order to analyze the proposed electronic starter, circuit topologies in each working state are derived. A prototype for 20W fluorescent lamps is also designed and implemented to access the performance. Experimental results show that features of a single-pulse ignition, adaptive preheating time, fast reset and lower voltage working ability can be achieved to meet the requirements of DMBS.

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


Keywords: Fluorescent Lamps, Electronic Starter, Dimming.




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