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Home>Products>Journal and Reviews>I.RE.Mo.S.>Latest issue
International Review on Modelling and Simulations - October 2009 - Papers
International Review on Modelling and Simulations - Papers
Vol. 2. n. 5, pp. 490-497
Abstract - In this
work, we present a new technique of multimodel modelling in the angular
frequency domain. This technique permits to put in evidence the aspects
of the systems that are bound closely to frequencies or strips of the
very determined frequencies. The system will be modelled by a set of
models called frequentials that are valid in ranges of adequate
frequencies. The set of ranges of frequencies will cover all the
frequential spaces. The global model is determined with the help of a
new formula of fusion between the models of the basis. We also present a
new technique of calculation of the angular frequency domain validities.
Keywords: Multimodel Approach, Angular frequency domain, Basis model, Validity phase, Validity gain.
Vol. 2. n. 5, pp. 498-506
Abstract - In this
work, we are interested in the modeling of complex systems by means of
adopting the multimodel approach. The use of a neural classification
method based on Probabilistic Neural Networks “PNN” and the “Kohonen”
Competitive apprenticeship networks allows determining the
representative models library of the system to be modeled. This
classification method requires priority knowledge about the
representation space of the collected measures, as well as about the
number of classes to generate the number of the base models.In this
paper, we propose to adopt the Principal Component Analysis “PCA” for
the selection of the systems measures’ projection axes, as well as the
algorithm of dynamic clouds “kmeans” for the automatic choice of the
number of classes. The use of these two methods proposes an interesting
solution for these two steps which must necessarily precede the
classification step. A comparative study between the two results, by
these two neural networks types, is provided in this study while two
benchmarks are studied to prove the performance of probabilistic
networks for the modeling of complex systems.
Keywords: Multimodel approach, Neural Networks, Classification, PCA, Kmeans, PNN, Kohonen.
Vol. 2. n. 5, pp. 507-512
Abstract - This paper show that can be using of distributed static series compensator (DSSC) for damping of low frequency oscillation .At first a detailed PSCAD/EMTDC simulation model of the DSSC is present. DSSC has a function like SSSC (static synchronous series compensator) but in a smaller size and a lower price with more capabilities. It lies in transmission lines in a distributed fashion. In the following, a number of DSSC are simulated in a single machine network which is connected to infinite bus. Moreover we will study one of the ancillary duties of this tool, which is used in low frequency oscillation damping, not studies so far. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Simulation Model, DSSC, Power Transfer Capability, Low Frequency Oscillation.
Vol. 2. n. 5, pp. 513-519
Abstract - In the current climate and environmental change, wind energy will not only be able to contribute to securing Australian energy independence and climate goals in the future but also it could turn a serious energy supply problem into an opportunity in the form of commercial benefits, technological research and employment. The aim of this paper is to analyse the dynamic behaviour of the GE wind turbine with Zero Power Mode (ZPM) characteristics connected to a weak power system and short transmission distance to the power grid, in terms of its stability following credible faults and its impact on export and import capability. Various system faults have been simulated to demonstrate the impact of wind energy on the system. Studies show that for all faults under most scenarios, the system remains stable and well damped, i.e. oscillations are damped to 50% within 5 seconds. Even for the most severe fault with 230kV line cleared by circuit breaker protection by tripping all the lines connected to 230kV bus, the system remains stable and well damped. The simulation studies are applied to a 24-bus WECC system. The results also demonstrate compliance with the applicable automatic standards connection to the grid with the exception of active power settling time. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Transient Stability Analysis, Renewable Energy Sources, Transmission System.
Vol. 2. n. 5, pp. 520-524
Abstract - Lightning strikes that directly hit the wind farm could cause excess damage. The blade and hub usuallly represent around one fourth of the cost of a large modern machine and may be the most expensive components to replace. The blade is not only the link between wind energy and the mechanical energy going to the gearbox, but could be a lightning link to all the equipment associated with the wind turbine.The effect of different transmission systems on overvoltages across devices in wind farm due to lightning has been studied in this paper. The most common transmission systems, i.e. AC, LCC-HVDC, and VSC-HVDC systems have been taken into consideration. Overvoltages have been simulated and compared using EMTP (ATPdraw). Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Lightning, Transmission system, VSC-HVDC, LCC-HVDC, STATCOM, Overvoltage.
Vol. 2. n. 5, pp. 525-531
Abstract - An electricity distribution system is a vital part of a total electric power supply system, since it is a link between a bulk transmission system and customers. It has been estimated that 80% of supply interruptions faced by customers are due to failures that occur in the distribution network. To secure more costumers with increasing competition, the energy supply companies are now increasingly under pressure to maintain a high degree of uninterrupted power supply quality and reliability. Therefore a practice of disconnecting all distributed generation units once a fault occurs is not a practical solution in a deregulated electricity market environment since it relies on power outage. Operation of safe intentional islanding would be viable solution. The aim of this paper is to present a genetic-based coordinated methodology for islanding operation and management of active and reactive powers in a distribution network after occurrence of a fault with regard to cost related to active and reactive powers generation of distributed generations, price of energy purchasing from a retail market, and loads interruption cost. Since optimal operation and islands configuration of a distribution network is a complicated and discrete problem, the genetic algorithm has been used for implementation and solving of the proposed algorithm. Simulations have been applied on 33-bus IEEE test system in three scenarios according to faulty branches and DGs penetration rate. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Distributed Generation (DG), Distribution Network Islanding, Genetic Algorithm (GA), Retail Market.
Vol. 2. n. 5, pp. 532-535
Abstract - In this paper calculation of parameters of a six-phase transmission line is presented. The calculation is carried out by extending the Carson’s line model in three-phase system. An existing three-phase double-circuit transmission line with two ground wires of Malaysian network, which belongs to TNB (Malaysian power utility), is chosen as a case study. The result of calculation of parameter of the line revealed that the positive sequence inductive reactance is somewhat higher for 6-phase single-circuit line than for a 3-phase double-circuit line. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Carson’s Line Model, Six-Phase Transmission Line.
Vol. 2. n. 5, pp. 536-541
Abstract - Permanent magnets due to their high energy production are widely used in a variety of electromagnetic devices. Such devices can be found in marine, aerospace, and robotic applications which require the minimization of weight and volume of the electro- magnetic devices. The coercively of some permanent magnets are high so the magnetizer is used for high magnetic field generation. Different parameters such as core shape, core material, turn number, cross section of the air gap, magnet type, etc have been known to affect the magnetizer operation. The amplitude and waveform of fixture current is obtained from PSPICE simulations and also experimental measurement. A 2D finite element analysis is developed to simulate magnetic fields and mechanical forces. The main parameters affecting optimal design of the magnetizer are discussed. Simulation results show that the core structure, air gap width, and turn numbers are the most important parameters when designing such a device. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Magnetizer, Effective Parameters, Fixture, Finite element method, ANSYS.
Vol. 2. n. 5, pp. 542-547
Abstract - A disturbance may occur on a grid power system during its normal operation. One of the most important disturbances on a grid is the opening of an energized line. In this work, the authors analyzed the behavior of a self-excited induction generator (SEIG) subsequently to a disconnection and sudden reconnection to the utility grid. Using the d-q axis model, the authors developed a mathematical model of the induction generator including the magnetizing flux saturation. Experimental results of transient rotor currents agreed well with simulation. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Modeling, Induction generator, Grid-connected induction generator, Saturation.
Vol. 2. n. 5, pp. 548-557
Abstract - The influence of arrangement, dimensions, and magnetic permeability of the magnetic flux shunts on the flux distribution, leakage reactance as well as axial electromagnetic forces acting on the transformer yokes, is studied in this paper using finite elements method and a simple modeling. By using magneto-static analysis and finite element method, the flux distribution in the 2D model of a core-type three phase power transformer was calculated, and then the leakage reactance of the transformer windings is calculated using the magnetic stored energy method. By calculating the leakage reactance, the short circuit current amplitude and therefore the flux distribution in short circuit conditions and axial electromagnetic forces on the transformer windings were obtained. By studying the different models including magnetic flux shunts, the effect of the arrangement, geometric dimensions as well as the magnetic permeability of the magnetic flux shunt on the leakage reactance and the net axial forces acting on the transformer yokes were studied and some interesting results were obtained. It is shown that the variation of these parameters in the transformer model has the significant effect on the leakage reactance and net axial force acting upon the transformer yoke, for instant, for certain value of the magnetic shunt length, the net axial force acting upon yoke has its maximum value. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Axial Forces, FEM, Leakage Reactance, Magnetic Shunts, Power Transformer.
Vol. 2. n. 5, pp. 558-564
Abstract - Frequency response analysis is deemed as a suitable diagnostic method in identifying electrical and/or mechanical faults of power transformers that is extended recently. Sensitivity and accuracy of measured FRA is very effective in detecting faults that may not be investigated in power transformers comprehensively. In this paper, parameters that have influence on the sensitivity of power transformer are checked and the best conditions are obtained out of many analyses. The simulation is accomplished by using finite element method which is known as one of the most accurate types of simulation. Some novelties in analysis and solution type are used that has increased accuracy and decreased the time of simulation considerably. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Power transformer, Monitoring, Frequency-response analysis (FRA), Finite element method (FEM), Transfer function.
Vol. 2. n. 5, pp. 565-572
Abstract - Hybrid drive systems have become more common during the past decade not only in passenger cars but also in work machinery and heavy vehicles. The energy efficiency and performance of such systems is of interest, leading to a need for modelling and simulating a hybrid drive system. In this paper, a diesel-electric parallel hybrid drive system simulation model is introduced and some simulation results are presented. The expected lifetime of a supercapacitor is evaluated in an example duty cycle. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Diesel-electric parallel hybrid drive, Mobile working machines, Modelling and simulation.
Vol. 2. n. 5, pp. 573-576
Abstract - In this paper, a low-voltage low-power transconductor structure is proposed to be used in Gm-C Filters. Specifically, an impedance-enhancement technique has been employed in order to overcome the output-impedance reduction phenomenon in low-voltage deep-sub-micron applications. In order to illustrate the effectiveness of the proposed architecture, a 1-V 3rd–order Butterworth low-pass Gm-C filter has been designed and simulated in a 0.18-μm CMOS process. The filter has a cut-off frequency of 2.2MHz and consumes less than 1.5mW. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Body-driven gain-boosting, Flipped Voltage Follower, Gm-C filter, Low-voltage, Output impedance, Transconductor.
Vol. 2. n. 5, pp. 577-582
Abstract - Yield is undoubtedly the most critical factor to the competitiveness of a product in a semiconductor manufacturing factory. Therefore, evaluating the competitiveness of a product with its yield is a reasonable idea. For this purpose, Chen’s approach is extended in this study to evaluate the long-term competitiveness of a product through yield learning modeling in various ways. Subsequently, to enhance the long-term competitiveness of the product, capacity re-allocation is shown to be helpful. The effects are modeled, and the relationship between them is also discussed. A practical example is used to demonstrate the proposed methodology. Experimental results show that with an additional capacity of 3000 wafers per month, the long-term competitiveness of the product can be elevated up to 25%. Further, the most efficient way is to allocate 15000 more wafers per month to the product. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Yield Modeling, Fuzzy, Semiconductor.
Vol. 2. n. 5, pp. 583-587
Abstract - Two diffraction gratings placed in front of a flat surface generate an interference pattern representing the surface deformations. The local deformation about fatigue cracks has been investigated by the coherent optics method of moiré interferometry. The complexity of the interference fringe patterns motivated the parallel development of companion numerical models for simulating moiré interferometric response for known boundary conditions. Experimental patterns are here examined in the light of computer-generated fringe systems for a stationary crack in elastic as well as elastoplastic solids. Various effects due to material plasticity, specimen-dependent nonsingular stress, and mixed mode loading are identified in the fringe patterns. The high sensitivity of moiré interferometry permits quantitative analysis in the small- strain domain. We discuss the theory used and obtain general expressions for evaluation of slope and curvature by means of projection moiré. Severally examples models illustrate possible application of model and the method proposed. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Numerical Simulation, Crack Tips, Crack Propagation, Moiré fringes, Diffractions Patterns, Elastic Properties, Gratings.
Vol. 2. n. 5, pp. 588-594
Abstract - The main objective of this paper is to present a new model in order to describe the motion of the barchan dune. In the first part, we present a simple model of the dune: we show that the shape of the back of the dune can be predicted as a function of its height. And in the second part, we give the details of our model to describe the motion of the barchan dune in a field. The obtained results are in concordance with those obtained by other authors. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Barchan dune, Dune model, Velocity.
Vol. 2. n. 5, pp. 595-598
Abstract - Roughness plays an important role in determining how a real object will interact with its environment. Although roughness is usually undesirable, it is difficult and expensive to control in manufacturing. Decreasing the roughness of a surface will usually increase exponentially its manufacturing costs. This often results in a trade-off between the manufacturing cost of a component and its performance in application. In this paper we have modeled roughening of nanocomposite materials during both isotropic and anisotropic etching by using a level set method. It was found that the presence of two phases with different etch rates takes effect on the development of the surface roughness. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Level set method, etching, roughness, three dimensional simulations, nanocomposite.
Vol. 2. n. 5, pp. 599-605
Abstract - In this paper, long term load forecasting is presented, focusing on external factors. Factors having impact on the load are categorized into three groups, namely: governance factors, social factors and urban planning factors. Subordinates of each factor are identified and quantified. Then, a data-driven model is constructed, having the external factors as inputs and peak loads and energy consumptions as outputs. Subsequently, the outputs of the model (i.e. peak loads and energy consumption) are utilized to calculate load factors. Using the developed model, sensitivity of the load factor is investigated versus the external factors. This can be used for self-governance of distribution company (DISCO). Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Forecasting, Load, Consumption, Distribution Networks, Influencing External Factors.
by N. Uchaipichat Vol. 2. n. 5, pp. 606-609
Abstract - The objective of this study is to investigate the characteristic of electrocardiogram (ECG) for detecting sleep apnea. The heart rate variability (HRV) was extracted from RR interval information from ECG trace. In this study the HRV within 5 minutes sliding window was analyzed with continuous wavelet transform. The sum energy of wavelet power spectrum density between 0.015 and 0.05 Hz was studied in this analysis. Then the position of sliding 5-minute window was shifted along the HRV signal in steps of 3 minutes until the end of trace. The interquartile range (IQR) of the analyzed energy was used as the maker in this investigation. As the results it is found that the IQR performs in order to detect sleep apnea with area under receiving operating characteristics of 0.83. The performance in sleep apnea detection achieved at 100% sensitivity and 70% specificity. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Sleep Apnea, Electrocardiogram, Wavelet Transform, Heart rate variability, Stroke.
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