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International Review on Modelling and Simulations  - August 2010 - Papers

 

   

 

 

 

International Review on Modelling and Simulations - Papers

 

go to top   Further Investigations on the Causes of Manifold Ambiguities with Applications in an Array Formation
         by Supawat Supakwong

         Vol. 3. n. 4, pp. 461-468

        

Abstract - Array ambiguity is a common type of uncertainties often arises in direction finding systems due to linear dependence amongst manifold vectors in the signal subspace. When an ambiguous situation occurs, subspace-type direction-finding techniques fail to operate properly. This raises a concern of the performance degradation due to unreliability of the parameter estimation techniques. Nonetheless, the problem in minimizing the effect of manifold ambiguity has received very small attention. For these aforementioned reasons, this paper is aimed to analyze the causes of manifold ambiguities in the further extent, in an attempt to finding a method to minimize its impacts. Two important theorems are derived regarding the higher-rank ambiguity and the presence of ambiguous generator line in a planar array. Based on these findings, a novel array selection criterion is proposed to provide an array design procedure such that the presence of ambiguities can be minimized.
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Keywords:  manifold ambiguity, ambiguity minimization, higher-rank ambiguity, array design.

 


 

go to top   A New Algorithm (STF-CDQ) Based on Current Reference Detection In Hybrid Active Power Filter To Eliminate Harmonics
         by E. Samadaei, S. Lesan

         Vol. 3. n. 4, pp. 469-475

        

Abstract - According to importance of power quality in power network, improvement of compensator equipment and ways of efficiency increasing can reduces destroyer effect on network. Active power filters as more importance and finance in network and industrial has depended detector algorithm and switching technique. This paper presents a novel algorithm (STF-CDQ) for active power filter algorithm. This algorithm based on harmonic extraction is divided into two parts as feedback loop and feedforward loop. Also it increases accuracy of harmonic extraction by reducing of isolator calculation due to elimination of voltage calculation and changing of reference signal from voltage reference to current reference than similar algorithms. Also this changing causes that it can be used with switching techniques that work base on current as they are simpler and efficacy. Thus using the combination of this algorithm and current switching technique increases accuracy and decreases complication of previous structures that consequently, it increases controller efficacy of active power filter. Simulation result shows performance this model clearly.
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Keywords:  hybrid active power filters, hysteresis current control, Matlab/Simulink, self tuning filter .

 


 

go to top   Compensating of Nonlinear Loads by Hybrid Active Filters in Single Phase Non-Stiff System
         by M. Salehifar, S. M. Torabi, A. Shoulaie

         Vol. 3. n. 4, pp. 476-482

        

Abstract - This paper deals with two different configurations of hybrid filter used to compensate single phase nonlinear loads. Due to increase in number of nonlinear single phase loads in distribution system, this research has been conducted to offer a cheap solution to mitigate the adverse effects of such loads. MATLAB\Simulink based simulation for three different distorted loads and source conditions have been conducted and simulation results are shown in order to make a comparison between these configurations.
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Keywords:  hybrid active filter, passive filter, harmonic compensation, reactive power compensation, single phase loads.

 


 

go to top   A Novel Generalized SVPWM Strategy for Multiphase Multi-Machine Systems with Independent Control
         by N. Henini, L. Nezli, B. Tabbache, A. Tlemçani

         Vol. 3. n. 4, pp. 483-492

 

Abstract - The objective of this work is to establish the independent vector control of multiphase multimotor systems supplied with only one VSI (voltage source inverter) controlled by a novel generalized algorithm of SVPWM (Space Vector Pulse Width Modulation) technique. The independent vector control is allowed by employing a suitable connection of stator windings of the motors. The SVPWM technique is adopted due to its flexibility for optimizing switching waveforms and its well adaptation for digital implementation. However, the multiphase VSIs are multi-dimensional systems; consequently, the SVPWM must be implemented in a multidimensional vector space. This paper develops a novel analysis of multiphase space vector to synthesize a required phase voltages for driving multiphase multi induction machines (IMs) with a minimum switch stress. Theoretical developments are verified for two pentaphase machines series connected. Moreover, this algorithm can be easily extended to an n-phase multi-machines system.

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Keywords: multi-machine systems, independent vector control, Space Vector Pulse Width Modulation (SVPWM).

 


 

go to top   New Sliding-Mode Observer for Induction Machine in Electric Propulsion Applications
         by M. Ghariani, A. Ltifi, I. Ben Salah, M. Ayadi, R. Neji

         Vol. 3. n. 4, pp. 493-501

         

Abstract - The performance and efficiency of an induction motor drive system can be enhanced by online estimation of the critical parameters, such as the rotor time constant and stator resistance. A novel sliding mode observer with parameter identification is proposed in this paper to compensate the parameter variation effects. The (SMC) technique finds its stronger justification in the utilization of a robust nonlinear control law to model uncertainties. The used control algorithm is a sliding mode associated with a particular function “sat” to limit chattering effects that presents a serious problem in applications to variable structure systems such as electric propulsion. The observer is simple and robust, and suitable for online implementation for EV application. Simulation tests under load disturbances and parameter uncertainties are provided to evaluate the consistency and performance of the proposed control technique.

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Keywords: Lyapunov theorem, Field-oriented control, Induction motor (IM), Road vehicle electric propulsion, improved sliding mode control, fuzzy identifier.

 


 

go to top   Dual Analysis and On-line Assessment of Synchronous Generator under Line-Switching Test
         by R. Wamkeue, C. Jolette, I. Kamwa

         Vol. 3. n. 4, pp. 502-511

         

Abstract - The present paper deals with an efficient method behind the analysis of a synchronous generator (SG) under line-switching tests. The method is based on the hybrid model of the SG recently developed by the authors. The paper also attempts to point out the duality between line-switching and load-rejection (generator-tripping) tests. It appears that the line-switching test is the best alternative to the load rejection test in this context. Comparisons between simulation results and actual data obtained from a 4-pole 1.5-kVA, 208-V, and 60-Hz laboratory machine show the effectiveness of the proposed SG analysis framework in line-switching and load-rejection tests.

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Keywords: Synchronous generator, hybrid-model, line-switching tests and load-rejection tests, simulations and experiments.

 


 

go to top   Modeling and simulation of Direct Torque Control applied to a Permanent Magnet Synchronous Motor
         by Ahmed Lagrioui, Hassan Mahmoudi

         Vol. 3. n. 4, pp. 512-517

       

Abstract - Direct Torque Control (DTC) is one of the most excellent control strategies of torque and flux control of PMSM. It is considered as an alternative to the Field Oriented Control (FOC) or vector control technique. These two control strategies are different on the operation principle but their objectives are the same. Torque Control of an Permanent Magnet Synchronous machine based on DTC strategy has been developed and a comprehensive study is present in this papers. The performance of this control method has been demonstrated by simulations performed using a versatile simulation package, Matlab/Simulink.

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Keywords: Direct Torque Control (DTC), Permanent Magnet Synchronous Motor (PMSM), Matlab/Simulink.

 


 

go to top   Diagnosis of Rotor Faults in Induction Motor
         by H. Merabet, T. Bahi, Y. Soufi

         Vol. 3. n. 4, pp. 518-524

       

Abstract - In this paper we have addressed the most frequent faults in induction machine three-phase squirrel-cage, as the broken rotor bars and defects static and dynamic rotor eccentricity. The method of detecting these defects is based on frequency analysis of measurable quantities of the machine. In general we consider the stator current because it is easily measurable, significant when signatures match those on electromagnetic quantities. Despite changes in diagnostic methods, this method of analysis is effective to be used as a diagnostic technique and early detection of operating condition of the machinery in industrial plants. First, a modeling and simulation study on the defect model is presented. The first time we have developed the mathematical model of the machine, and then the simulation results are presented to illustrate the influences of these defects on the operational status of the machine.

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Keywords: Diagnosis, Detection, Eccentricity, Induction motor, Modeling, Simulation.

 


 

go to top   A New Approach to Assess the Influence of Stray Load Losses on Vector Control Accuracy in Voltage-Fed Induction Motor
         by E. Babaei, A. Sadjadi, M. B. B. Sharifian

         Vol. 3. n. 4, pp. 525-532

       

Abstract - Vector control accuracy of induction motor drives is affected by variations of motor parameters that are treated in the control algorithm as constant values, and by the phenomenon that is not modeled at all and is therefore unaccounted for in the controller. Detuning sources of the first type include variations of rotor and stator resistance, mutual inductance, and leakage inductances, while the second category includes stator iron (core) losses. All these sources of detuned operation have been investigated in a considerable depth in the past. One of the potential sources of detuned operation is the stray load loss (SLL), which belongs to the category of unmodeled phenomena because vector controllers are not aware of its existence. Taking into account no-load and under-load stray losses of machine, this paper develops an analytical model that characterizes detuning due to SLLs in indirect rotor-flux-oriented (RFO) voltage-fed induction motor drives in steady-state operation by means of the orientation angle error, actual to reference rotor- flux ratio, and actual to reference-torque ratio.

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Keywords: Stray load loss, vector control, voltage-fed induction motor.

 


 

go to top   Eccentricity Fault Monitoring by Analysis Stator Phase Currents
         by A. Metatla, S. Benzahioul, T. Bahi, D. Lefebvre

         Vol. 3. n. 4, pp. 533-537

        

Abstract - In this paper we develop an approach based on residue analysis of stator currents to detect and diagnose faults eccentricity static, dynamic and mixed in three phase induction motor. To simulate the behaviour of motor failure, a model is proposed based on the approach of magnetically coupled coils. The simulation results show the importance of the approach applied for the detection and diagnosis of fault in three phase induction motor.

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Keywords: Monitoring, Modelling, Induction Motor, Detection, Diagnosis, Residuals, Fault, Stator Currents.

 


 

go to top   Indicators and Signal Processing Techniques Developed to Investigate the Effects of Rotor Faults in Cage Rotor Induction Machines
         by L. Mihet-Popa, V. Groza

         Vol. 3. n. 4, pp. 538-545

          

Abstract - Rotor faults on cage-rotor induction machines can occur during normal operation due to design and manufacturing defects, misoperation, misapplication, lack of preventive maintenance and so on. In this paper the rotor faults are detected by investigating the spectrum of the flux linkage of the stator windings and frequency spectrum of rotor currents. Rotor faults of three-phase induction machines can also be detected by monitoring stator currents, speed and torque, as a function of time, during steady-state and transient operations. A variety of signal processing strategies to detect how serious the rotor damage is has been proposed and developed. The simulation algorithm has been written in MATLAB using a modular construction based on a flowchart.

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Keywords: broken rotor bars, cage-rotor induction machine, fault detection methods, signal processing techniques.

 


 

go to top   Best Operating Parameters of the Disc-Rotor Switched Reluctance Motor
         by E. A. El-Kharashi

         Vol. 3. n. 4, pp. 546-552

          

Abstract - The disc-rotor switched reluctance motor is a new type of the SRMs. It is designed by a particular way to increase the saliency ratio to its maximum possible value in order to achieve high torque density. It produces approximately double the torque of its equivalent conventional SRM. The paper examines the impact of the operating parameters on the output torque of this ultra high torque SRM which employ a disc rotor construction. The performance is studied at different conducting angles and for different advance switching on angles meanwhile the copper losses are monitored. From the simulation results the best operating parameters are selected which run the disc rotor SRM efficiently at the highest possible output torque with the lowest possible losses. At this best operating point the performance is studied extensively to assess this type of SRM precisely.

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Keywords: Disk type rotor, Conduction angle, Phase advancing and Switched reluctance motor.

 


 

go to top   A Modified Direct Torque Control for BLDC Motor Drives
         by Farshad Montazeri and Davood Arab Khaburi

         Vol. 3. n. 4, pp. 553-559

          

Abstract - In this paper a modified Direct Torque Control (DTC) scheme for Brushless DC Motors is presented. The aim of this modification is to overcome the problem of variable switching frequency and high torque ripple in conventional hysteresis based controllers of DTC drives. Also with a new modified switching table and a new torque controller, the power recovery and electrical braking performance of BLDC motors are improved. As it is known, in DTC drives for BLDC motors there is a commutation torque ripple, which occurs every 60 electrical degrees. In this novel method, these commutation ripples are completely eliminated by employing the three-phase switching table in the preceding time of the commutation periods. This novel method has a simple control structure which is compatible with principle of conventional DTC scheme. In classic DTC drives, the switching frequency is variable. In this paper, in order obtain a fix switching frequency, a new and simple torque controller is introduced, to replace the conventional hysteresis comparator. These simple modifications have significantly improved the performance of the DTC drive system, while at the same time all the advantages of the basic DTC are still retained. Simulation results have shown the proposed modified DTC scheme causes apparent reduction of the torque ripple and maintaining a constant switching frequency, compared with conventional DTC drives for BLDC motors.

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Keywords: Brushless DC (BLDC) Motor, Current Commutation, Direct Torque Control (DTC), Fix switching frequency.

 


 

go to top   Effects of FACTS Devices on Voltage Stability for Different Static Load Models
         by Ali Zare, Mehdi Ghasemi

         Vol. 3. n. 4, pp. 560-567

 

Abstract - Loads, generators, and power system’s structures are effective factors that significantly affect the voltage stability. The selection of a sufficient model for loads has a significant effect on the accuracy of voltage stability analysis. The constant power load model is commonly used in voltage stability studies and specially in examining the effects of FACTS devices. However, the actual loads in power systems are not constant power. This paper focuses on the hidden effects of the interaction between loads and STATCOM on the voltage stability. Simulations results revealed the salient effect of loads on the STATCOM performance.

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Keywords: Static Load Model, Voltage Stability, STATCOM.

 


 

go to top   Power Quality Enhancement Using Gate-Controlled Series Capacitor
         by M. R. Alizadeh Pahlavani, R. Ghandehari, A. Naghashpour, H. A. Mohammadpour

         Vol. 3. n. 4, pp. 568-574

         

Abstract - This paper presents a new application of the Gate - Controlled Series Capacitor (GCSC) for voltage sag mitigation of a sensitive load and power quality enhancement of power systems. For this study, a GCSC was tested in conjunction with a power system having a sensitive load. The study was performed using MATLAB program. It is shown that if the GCSC's control system is well designed, it will help to mitigate the voltage sag consequences during strong faults and can help to enhance the power quality and the transient state of the load voltage and the power system.

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Keywords: Gate-Controlled Series Capacitor, Power Quality, FFT, FACTS.

 


 

go to top   Improvement of SSR by Using GA Tuned Fuzzy Logic UPFC Controller
         by Ali Hemmati, Mostafa Ghafoori

         Vol. 3. n. 4, pp. 575-580

         

Abstract - This paper presents the result of an investigation on the application of recently developed FACTS devices, Unified Power Flow Controller (UPFC), for damping torsional oscillations that occur in a series compensated AC system. A Fuzzy Controller is designed to control UPFC for this. In order for a Fuzzy rule based control system to perform well, the Fuzzy sets must be carefully designed. A major problem plaguing the effective use of this method is the difficulty of accurately constructing the membership functions. because it is a computationally expensive combinatorial optimization problem. On the other hand, Genetic Algorithms (Gas) is a technique that emulates biological evolutionary theories to solve complex optimization problems by using directed random searches to derive a set of optimal solutions. For this reason, in the designed Fuzzy Controller, the membership functions are tuned automatically using GA.

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Keywords: UPFC ; SSR ; Genetic Algorithm(GA) ; Fuzzy Controller; FACTS.

 


 

go to top   Control Loops Design and Harmonic Distortion Minimization in Active Filtering-based Compensation Power Systems
         by Mihaela Popescu, Alexandru Bitoleanu

         Vol. 3. n. 4, pp. 581-589

         

Abstract - This paper is mainly focused on improving the performance of a three-phase shunt active power filter system by adopting an optimization-based method to design the control loop parameters under conditions of an optimized DC-bus voltage value in order to minimize the grid current harmonic distortion. The simulations performed under Matlab-Simulink environment show a very good behavior of the control system regarding the reference tracking. Besides, it is pointed out that the equality of the apparent powers at the AC and DC sides of the active power filter leads to a minimum harmonic distortion factor of the grid current. The theoretical achievements are verified by experimental way on a MaxSine-type active power filter.

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Keywords: Controller tuning, Modulus Optimum method, Optimum control, Shunt active power filter.

 


 

go to top   Fuzzy Logic Based Frequency Stabilization in a Parallel AC – DC Multi Area Non Reheat Thermal Power Systems
         by S. Ramesh, A. Krishnan
         Vol. 3. n. 4, pp. 590-597

         

Abstract - In this paper, a set of fuzzy logic rules is designed to maintain the system frequency is parallel AC-DC interconnected non- reheat thermal power system. When an interconnected AC system is subjected to a load disturbance, the system frequency may be disturbed. By utilizing the control channel of HVDC link in parallel with the AC link, the system dynamic stability is improved and reduces the area control error. In the design of power modulation controller, the overlapping decomposition techniques and Eigen value assignment method are applied to establish the system control. The system responses to various load changes in the multi area system are studied with help of MATLAB simulation. The conventional integral control does not yield adequate control performance. To overcome this problem fuzzy logic controller is employed with a set of rules. The study shows that the proposed controller is effective in damping the oscillation. The performance of the proposed approach was verified from simulation and comparison.

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Keywords: Load Frequency Control, AC – DC Interconnected System, High Voltage Direct Current (HVDC) Link, Area Control Error, Fuzzy Logic Control.

 


 

go to top   New Method to Connect Wind Turbines Equipped With DFIGs to the Power Grid Using FCL and STATCOM
         by M. Fazli R. Jahani, Ali Fazli, J. Olamaei, H. A. Shayanfar
         Vol. 3. n. 4, pp. 598-603

         

Abstract - The wind power has the most rapid growth in comparison with other renewable energies. The main issue of wind turbines that equipped with Doubly Fed Induction Generators (DFIGs) is the grid faults or low voltage ride through capability. In this paper, a new solution for uninterrupted operation of wind turbine driving a DFIG has been proposed during fault condition in the grid. A Fault Current Limiter (FCL) is placed in series with the rotor circuit. During fault condition FCL enters a huge solenoid in the rotor circuit to inhabit increasing of current in the rotor circuit. When the fault is cleared the FCL bypasses the solenoid. A Static Synchronous Compensator (STATCOM) has been applied for supplying required reactive power in faults and steady states. Capability and modeling accuracy of the proposed method confirmed with simulating a sample power system in PSCAD/EMTDC software.

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Keywords: Doubly Fed Induction Generators (DFIGs), Fault Current Limiter (FCL), Static Synchronous Compensator (STATCOM), Wind Turbine.

 


 

go to top   A Novel Structure for Distributed Generation Using Battery Pack and Power Injection Controller
         by Peyman Naderi, Amir R. Naderipour, Mohammad Azizianfard
         Vol. 3. n. 4, pp. 604-612

         

Abstract - In this paper a strategy has been introduced for Distributed Generation (DG) structure using battery package and SPWM method for bi-directional AC/DC convertor. In the proposed structure, a battery pack is connected to a typical power network via an AC/DC converter and a filter block where a fuzzy controller have been devised for active power flow direction considering the battery’s state of charge (SoC). Also, a method has been introduced for islanding detection and isolated operation of DG system. Finally, verification as simulation results shows the effectiveness of the proposed method.

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Keywords: Fuzzy; Islanding; SPWM Method; SoC.

 


 

go to top   DSM Strategy Based Effective Management of Households to Support Energy Sector
         by Parmal Singh Solanki, Venkateswara Sarma Mallela, Malcolm Allan, Chengke Zhou, K.G. Balakrishnan
         Vol. 3. n. 4, pp. 613-620

         

Abstract - The increasing demand for electricity in all gulf states, in particular the Sultanate of Oman, is reminding energy sector to verify their productivity as well as their consumption levels of late. Lack of knowledge about the electrical energy consumption and generation levels results in lavish utilization thereby leading to shortage of electrical power. Load data are mandatory for determining and regulating the demands to produce electricity that meets the required level. This paper proposed an analytical model for the utilities to aid in the supply of generated electricity in such a way that the energy is distributed without any insufficiency of usage for the rural and urban regions. The aim of the model is to recommend the solutions for end-users so that the appliances considered as less significant may be shutdown. The energy consumed by these appliances is equalized with the energy consumed by appliances which are considered to be inevitable. A case study is presented in paper to shutdown the 25 kWh of energy from households at rural and urban area during weekdays and weekends. The MATLAB codes are developed to implement the proposed model to simulate the solutions by recommending shutdown of less significant household appliances to achieve declared target.

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Keywords: Analytical model, Demand side management, Household appliances, and Shutdown rate.

 


 

go to top   Improving the PV Panel Model Based on Manufacturer Data
         by M. Taherbaneh, A. H. Rezaie, H. GhafooriFard, M. B. Menhaj, J. M. Milimonfared
         Vol. 3. n. 4, pp. 621-629

         

Abstract - Solar panels modeling is very interesting based on data supported by manufacturers exclusively and without any measurements. Knowing that manufacturers only report the electrical specifications of their products at one operating condition, there are so many cases in which the specifications in other conditions are of interest. To cover this necessity, an appropriate model with sufficient accuracy shall be utilized. In this research, a comprehensive one-diode model for a solar panel with maximum attainable accuracy is fully developed. The model is scrutinized for a typical multi-crystalline solar panel.
MATLAB environment is used to implement and simulate the proposed model. The Newton's method is chosen to solve the model nonlinear equations. A modification is also reported in the Newton's solving approach to attain the best convergence. Based on datasheet values, the model parameters are only extracted in standard conditions. Then, the model parameters dependencies on environmental conditions are taken into consideration as much as possible. Two recursive nonlinear equations are proposed in order to extract dark-saturation current and open-circuit voltage dependencies on environmental conditions accurately. Using the Newton's approach to find the numerical solution of the equations, dark-saturation current and open-circuit voltage dependencies on temperature and irradiance are fully obtained. Finally, some results are given to approve that dark-saturation current and open-circuit voltage of the model both have the nonlinear relationships with the temperature and irradiance level. The proposed Model is validated through experimental results. Comparison between real data and simulations results also show that our proposed model has maximum obtainable accuracy.

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Keywords: Solar Panel, One-Diode Model, Manufacture Data, Environmental Conditions.

 


 

go to top   Application Preconditioned Conjugate Gradient Method for Large Earthing System
         by Halid Matoruga Hamid Zildžo, Rasim Gačanović
         Vol. 3. n. 4, pp. 630-633

         

Abstract - Earthing systems for large substation are usually made as horizontal meshed earthing grid with vertical rods. Procedures for design of earthing system are based on achieving protection against danger touch and step voltage into substation and just outside metallic fences of substation. When designing earthing systems, it is important to concentrate on the ploating potential that occur on the passive electrodes during flow fault current from active part of earthing system in earth. Passive electrode may be all buried metallic structures that are located in substation or in its vicinity, which are not galvanic connected with the main earthing system. The most common examples for passive electrode are metallic fences, rails, piping, communication and signal circuits, cable sheaths or armor etc. In this paper will be analyzed numerical model based on Finite element Method for solving the Poisson equation for stationary current field of earthing system. Large linear system equation will be solution with Preconditioned Diagonal Scaled Conjugated Gradient Methods.

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Keywords: Finite element Method , Large linear system equation, earthing systems, Preconditioned Diagonal Scaled Conjugated Gradient Methods.

 


 

go to top   Computer Model Analysis of Variations of Parameters of the Short-Horizontal Grounding Electrode for Ionization
         by Rasim Gačanović, Hamid Zildžo, Halid Matoruga
         Vol. 3. n. 4, pp. 634-638

         

Abstract - This paper briefly exposed to the principles of modeling of soil ionization on the lightning rod grounding electrodes telecommunications systems and small power facilities. We also provide basic data on the computer model to simulate ION.GR ionization, which was created during the research project "Analysis of the frequency dependent parameters of the grounding." Using the above model we analyzed the variations of some important parameters on the effects of ionization on the short strap grounding electrodes. Particularly interesting appears the possibility of applying the analysis of this phenomenon in isolated and exposed to atmospheric discharge facilities.

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Keywords: Ionization of soil, a short strip grounding, electromagnetic transients, frequency dependence, voltages, grounding, atmospheric discharge, numerical methods.

 


 

go to top   Novel Intelligent Sizing Algorithm for Grid-connected Photovoltaic System Design
         by S. I. Sulaiman, T. K. A. Rahman, I. Musirin
         Vol. 3. n. 4, pp. 639-652

         

Abstract - This paper presents a new intelligent algorithm for sizing grid-connected photovoltaic (GCPV) systems. The sizing process involves the selection of PV module and inverter as well as the estimation of the technical and economic output performance of the system. Although many existing sizing software have been beneficial in assisting the GCPV system design, the application of these software might be limited due to the rigid algorithm embedded in the software. On the other hand, the manual calculation-based design approach could be another viable option but the design process could be extremely tedious especially when various design options need to be evaluated. In this study, the PV module and the inverter were selected from the respective databases whereas the sizing algorithm was developed evolutionary programming (EP). Besides selecting the PV module and inverter, the new algorithm, known as EP-based sizing algorithm (EPSA) was used to determine the techno-economic performance of the system. The EPSA was tested using the classical EP and meta-EP models before the best model was selected for EPSA. The proposed EPSA with meta-EP model was found to outperform a proposed conventional iterative sizing algorithm (ISA) in terms of computation time.

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Keywords: evolutionary programming (EP), grid-connected photovoltaic (GCPV), inverter, module, photovoltaic (PV).

 


 

go to top   Efficient and Accurate Modeling and Simulation Techniques for Substrate Coupling Analysis in Deep Submicron Mixed-Signal IC’s
         by Gh. Karimi, E. Akbari

         Vol. 3. n. 4, pp. 653-664

         

Abstract - Phase-locked loops (PLLs) are used in wireless receivers to implement a variety of functions, such as frequency synthesis, clock recovery, demodulation, and mixed-signal integrated circuits. Substrate coupling noise is a key problem in today’s large mixed-signal systems. Switching-noise generated by digital circuits can be coupled to sensitive analog circuits through the substrate, can degrade circuit performance. Substrate noise in integrated circuits is a major impediment to mixed-signal integration. Accurate simulation is therefore, needed to investigate generation, propagation, and impact of substrate noise. The estimating an accurate modeling of noise coupling effects is a major challenge for designers. In this paper, we introduce novel substrate noise estimation and describe a fast and accurate simulation for modeling substrate coupling noise in mixed-signal RF IC design. Using a three-dimensional finite element method for extraction of substrate parasitic elements is developed. This approach allows the designer to maintain a grasp of the fundamentals using coarse models at the early stage of the design and to eventually gain insight on the lower order effects by gradually increasing the level of detail as the design develops.

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Keywords: phase-locked loop (PLL), substrate coupling, substrate noise, Mixed-signal, phase noise, Three-dimensional finite element method.

 


 

go to top   Precise Modeling of GPS GDOP using Neural Network
         by M. R. Mosavi, M. Saraf

         Vol. 3. n. 4, pp. 665-671

         

Abstract - GPS errors resulting from satellite configuration geometry can be expressed in terms of Geometric Dilution of Precision (GDOP), the factor often used for selecting good satellite’s subset. The most straightforward approach for GPS GDOP computation utilizing matrix inversion is a time-consuming task. In this paper, the Back-Propagation Neural Network (BPNN)-based GPS GDOP accurate approximation optimized with Genetic Algorithm (GA) is presented in order to reduce the computational burden. One general class of stochastic methods, GAs are numerical algorithms inspired by both natural selection and genetics. Considering GA methods for finding NN weights, the task is to bias the search toward regions where we expect the solution to be and allow randomness to help find good weights. Using gradient information to update weights in BPNN is so sensitive to weights vector initializing. For overcoming this problem, GA is used for better initializing of weights vector. The computer simulations emphasize the good effectiveness of proposed method compared with self GA optimization and stochastic gradient descent algorithm. This research demonstrates BPNN with GA optimization provide a new precise modeling of GPS GDOP with less complexity.

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Keywords: Back-Propagation Neural Network, GPS GDOP, Genetic Algorithm, Precise Modeling.

 


 

go to top   Microstrip-Fed Printed Slot Antennas Based on Hilbert-Type Space-Filling Curves for Wireless Communication Systems
         by Jawad K. Ali

         Vol. 3. n. 4, pp. 672-678

         

Abstract - In this paper, two microstrip-fed printed slot antennas have been introduced to be used in modern communication systems, as alternatives for conventional Hilbert slot antenna. The slot structures of the proposed antennas are in the form of the 3rd iteration of two variants of the conventional Hilbert space-filling curves. These antennas are fed with 50 Ω microstrip line printed on the reverse side of the slot structure. The proposed antennas have been modelled and analyzed using the method of moments (MoM) based commercially available software, IE3D from Zeland Software Inc,. Simulation results show that all these antennas possess a multi-resonant behavior with a miniature size of about half the guided wavelength. It has been found that the fundamental resonance depends on the external side length of the slot structure, while higher mode resonances are attributed by the smaller self-similar structures the slot pattern contains. Furthermore, amongst the proposed antennas, the antenna with slot structure based on Moore’s space-filling curve, which is a closed version of Hilbert curve, has been found to offer a multiband behavior with enhanced bandwidths around the multiple resonances as compared with the other two antennas based on other Hilbert space-filling variants.

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

 

Keywords: Printed Slot Antenna, Microstrip-Fed Antenna, Multiband Antenna, Hilbert-Type Fractal Curves.

 


 

go to top   A Chaotic Pulse Radar Based on Double Scroll Chaotic Oscillator
         by Seyed Arash Sheikholeslam, Mahmood Modarres-Hashemi

         Vol. 3. n. 4, pp. 679-683

         

Abstract - In this paper one approach for radar pulse compression, named chaotic phase modulation, is presented which is based on double scroll chaotic oscillator. The features of the proposed chaotic waveform, specially the power spectral density (PSD) and ambiguity diagram are compared with LFM pulse compression method through simulations. It is shown that the new wavefrom has an acceptable PSD feature and also has a better ambiguity diagram than that for LFM.

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

 

Keywords: Chaos, Double scroll, Ambiguity diagram, LPI Radar, Linear-FM, Chaotic Phase Modulation.

 


 

go to top   An Experimental Study of the Influence of the Background Noise Actual Due to Vibration on the Behavior of a Structure
         by A. Touhami, B. Benabdelkader, M. Elmir, M. Bouanini

         Vol. 3. n. 4, pp. 684-688

         

Abstract - The aim of this work is to determine the dynamic of a structure; namely the proper frequencies and damping coefficients of the structure when subjected to vibration. Our experimental study took place at the Vibration laboratory in the technological hall of the University of Béchar.
We have determined the actual behavior of this structure after excitation by a background noise generated by a vibrating table placed outside the laboratory and simulated by a power extractor. The response of the structure was captured by a tri-axial accelerometer.
The experimental results obtained were validated by a numerical simulation based on the finite element method.

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

 

Keywords: Background noise, damping, dynamic structure, excitation, proper frequency, response, trafic road.

 


 

go to top   Investigation of Effective Parameters of Springback in Hydroforming Process and Comparison by Deep Drawing Process by FEM
         by R. Alipour, M. A. Bahari

         Vol. 3. n. 4, pp. 689-693

         

Abstract - Spring back is a key factor that can play a major role in the degree of quality and deformation of deep-drawing parts through a variety of methods of deep drawing. It is, therefore, necessary to know the factors involved in this phenomenon in order to optimize the production process and maximize. The dimensional accuracy of the manufactured parts, thus enabling the manufacturer. To fully control deep drawing process. This paper examines both methods of traditional deep drawing and finite element hydroforming and by using modeled explicit solution methodology and the parameters involved in the spring back in each of the methods. Studying the influence of the die clearance to Sheet thickness ratio, the friction coefficient and variations in blank holder force in reducing spring back, are among the most important objects of this study. The results suggest that optimization of the above parameters in hydroforming method, compared to traditional deep drawing, has more remarkable effects on the quality of manufactured product.

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

 

Keywords: Spring Back, Deep Drawing, Hydroforming.

 


 

go to top   A Novel Hybrid Method for Thermal Unit Commitment Problems
         by S. Ganesan, S. Subramanian

         Vol. 3. n. 4, pp. 694-704

         

Abstract - This paper presents a hybrid approach for solving thermal unit commitment problems. The solution methodology comprises of two stages processes of unit selection and economic dispatch of the committed units. The Modified Priority List (MPL) is used for unit selection, which is developed by sorting the units in descending order in respect of their Contribution Factor (CF). Sequential Approach with Matrix Framework (SAMF) is applied to determine the optimal real power dispatches of the committed units. The proposed methodologies are validated by solving standard ten unit system and suitably scaled 20, 40, 60, 80 and 100 unit systems with one day schedule horizon. Further, the potential of the proposed approach is verified for solving a unit commitment problem with ramp rate constraints. Numerical simulation results indicate an improvement in total cost saving and hence the superiority of the proposed method has also been revealed.

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

 

Keywords: Economic dispatch, modified priority list, ramp rate limit, sequential approach, unit commitment.

 


 

go to top   Reciprocal Relations Between Experimental and Numerical Results of Fluidization
         by J. Wydrych, N. Szmolke

         Vol. 3. n. 4, pp. 705-716

         

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

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

 

Keywords: small fluid boilers, PIV and CFD correlation.

 


 

go to top   Modelling of a Welded Steel Tube Subjected to Internal Pressure
         by Hamid Djebaili, Mohamed Tahar Hannachi, Mansouri Khelifa

         Vol. 3. n. 4, pp. 717-725

         

Abstract - The rapid pace of technology development and strong competition in the market, prompted us to consider the field of manufacturing of steel pipes by a process complies fully with the requirements of industrial induction welding is high frequency (HF), this technique is better known today in Algeria, more precisely for the manufacture of tubes diameters Single Annabib TG Tebessa. The aim of our study is based on the characterization of processes controlling the mechanical behavior of steel pipes (type E24-2), welded by high frequency induction, considering the different tests and among the most destructive known test internal pressure. The internal pressure test is performed according to the application area of welded pipes, or as leak test, either as a test of strength (bursting). All tubes are subjected to a hydraulic test pressure of 50 bar kept at room temperature for a period of 6 seconds. This study provides information that helps optimize the design and implementation to predict the behavior of the tubes during operation.

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

 

Keywords:  pressure, tubes, welding induction HF, Von Mises stresses, Castem.

 


 

go to top   Numerical Prediction of Engine Pressure at Direct Injection of Hydrogen Fuel in a Natural Gas Spark Ignited Direct Injection Engine
         by Khaled A. Rezk, Mohsen M. Osman, Mohamed M. El-kassaby

         Vol. 3. n. 4, pp. 726-738

         

Abstract - The design, development and optimization of an internal combustion engine require the application of a modern sophisticated analysis tool. In addition to experimental work, numerical calculations are now necessary to provide an insight into the complex in-cylinder process. A commercial Computational fluid dynamic code Fluent 6.3 has been used as the modeling platform for investigating the effect of hydrogen direct injection in DI-CNG spark ignited engine on engine operation. The simulation was conducted in a single cylinder, 4 stroke direct injection engine running at wide open throttle (WOT) condition. Different hydrogen ratios by mass (3%, 4 %, 5 %) were injected in the combustion chamber for the considered engine speed of 1000 rpm. The engine was configured with no swirl and low tumble motion. The numerical calculations have been carried out during crank angle period that starts after intake valve closure to exhaust valve opening with different hydrogen injection timing and different ignition timings. With controlling the hydrogen injection then we can control the lean limit in the combustion chamber for different driving conditions. The results show loss of in-cylinder pressure with different ignition timing and slightly hydrogen injection timing effect. Also it was noticed that increasing the hydrogen percentage in the combustion chamber decreases the in-cylinder pressure with these conditions.

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

 

Keywords: Fluent, CFD, DI, Natural Gas, Hydrogen Direct Injection.

 


 

go to top   Calculation of Cooling Massive Conductors with Finite Element Method in Fluid Dynamics
         by Hamid Zildžo, Rasim Gačanović , Halid Matoruga

         Vol. 3. n. 4, pp. 739-745

         

Abstract - This paper presents procedure for solving non-stationary thermal field of massive conductors using the finite element method. To solve the equations of conservation of mass, momentum, thermal energy, kinetic energy of turbulence and its dissipation is used well-known Simplex method was modified with Chorinom and Greshoom. Turbulence of the surrounding fluid is modeled with the k-ε turbulence model.

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

 

Keywords: buses, substations, Galerkinov procedure, simplex method, finite element method, numerical solution, fluid dynamics.

 

 


 
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