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Applied and Theoretical Electricity (ICATE), 2012 International Conference on

Date 25-27 Oct. 2012

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  • [Title page]

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  • 2012 International Conference on Applied and Theoretical Electricity (ICATE) PROCEEDINGS [Copyright notice]

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  • Foreword

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  • Committee

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  • Table of contents

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  • Author index

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  • On analog circuit parameter estimation

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB) |  | HTML iconHTML  

    Our paper presents a new method to estimate the analog circuit parameters based on some measurements performed on the real circuit, the parameters of interest being those which are difficult or impossible to be measured directly. Starting from the equivalent scheme of an analog circuit in sinusoidal behavior, we generate the network function in full symbolic form, obtaining an appropriate frequency space representation based on the complex or Laplace modified nodal equations. The magnitude and the phase of the complex transfer function can be measured by supplying the circuit with a variable frequency sinusoidal voltage. Using the measured parameters as reference and the symbolic transfer function computed before, the model parameters of interest are obtained by an iterative identification algorithm based on Output Error method. In this paper are defined two new objective functions which can be minimized using one of the fminimax or fminunc functions from the Matlab toolbox. Both algorithms are based on iterative computation starting from certain initial values, being efficient for less than four estimated parameters. The algorithms are suitable for linear circuits, as well as for small-signal nonlinear circuits. Finally, the proposed estimation techniques were tested and validated on simulation data on an illustrative example. View full abstract»

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  • Generation Program of State Equations

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (337 KB) |  | HTML iconHTML  

    An analog circuit analysis method in the time domain, based on the state equation procedure, is presented. This method automatically formulates the state equations in a symbolic normal-form, for large time-invariant analog circuits. Starting from the circuit description in the netlist form, this method is based on Kirchhoff's laws, constitutive equations of the circuit elements, and it uses the facilities of symbolic simulator Maple. Using the state equations in the operational form the circuit functions in full symbolic, partly symbolic or numeric form are generated. In this paper is described one very efficient algorithm that generates the state equations in normal full symbolic form. This algorithm was implemented in a program - called SYSEG - SYmbolic State Equation Generation. This program allows the formulation of symbolic state equations without any inverse of a symbolic matrix, and, by cancellation and simplification of the expressions; it obtains a symbolic compact form. SYSEG also allows the schematic representation, the analysis and design of linear or nonlinear analog circuits, even when they have excess elements. A user guide in English version for SYSEG program is presented. Also an illustrative example is given to prove that SYmbolic State Equation Generation program is a very useful tool for symbolic analysis and design of linear and/or nonlinear time-invariant analog circuits. This example proves that SYSEG program can be used also for the circuits with excess elements. View full abstract»

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  • A low power discreet time sigma delta modulator in 50nm CMOS digital

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (462 KB) |  | HTML iconHTML  

    Sigma delta modulators (ΣΔMs) form part of the core of today's mixed-signal designs. The ongoing research on these devices shows the potential of ΣΔ data converters as a promising candidate for high-speed, high-resolution, and low power mixed-signal interfaces. This paper presents a new circuit realization for discreet time sigma delta modulator. The modulator is designed in 50nm CMOS digital technology and features low power consumption (<;100uW), low supply voltage (±1.2), and wide dynamic range (>;70db). The performance of the circuits was demonstrated using HSPICE at low voltage operation of ±1.2V. The modulator was used to design 11bit second order ΣΔ ADC. This architecture is an attractive approach to implementing precision A/D convertors in scaled digital VLSI technologies. View full abstract»

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  • Virtual instrument for study of single-phase AC unknown load

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (801 KB) |  | HTML iconHTML  

    In this paper, using Lab VIEW graphical programming environment is realized a virtual instrument (VI) which is used at the study of single-phase AC unknown load. In this study the circuit of unknown load is analyzed in case of sinusoidal permanent regime. The voltage and current of the load are the main input parameters used in this study. They are represented as phasors in the complex plane. Also the phase angle (in degrees) between voltage and current is very important for this study. These parameters are obtained by simulation and theirs values can be set and modified manually with numerical controls. The impedance of unknown load is displayed in complex form, where the real (resistance) and the imaginary (reactance) components are shown. The virtual instrument have two graphs. One graph shows the voltage and current waveforms in relative (perunit) values, while another graph displays the phasors obtained from the voltage and the current functions. The real and the imaginary components of the voltage phasor and the current phasor are also displayed in this graph. With our virtual instrument one interprets the nature of the unknown parameters of the load (pure resistive R, capacitive C, inductive L, resistiv-capacitiv RC, resistiv-inductiv RL). View full abstract»

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  • On wireless power transfer

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (704 KB) |  | HTML iconHTML  

    The paper is a general survey on power transfer by induction. The physical principle is pointed out and the constraints for an optimal operation applied both to the emitter and receiver are specified. Couple mode theory is used to study the wireless power transfer and a comparison with the circuit theory results is made. The analysis is focused on the power transfer efficiency in connection with the mutual inductance. An accurate method for mutual inductance computation is presented and the power transfer optimization is performed for different geometrical configurations which involve different mutual inductances. View full abstract»

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  • Analysis of 2D symmetrically coupled vertical microstrip lines between two infinite grounded planes using HBEM

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB) |  | HTML iconHTML  

    This paper presents an application of the hybrid boundary element method, developed at our Department of Theoretical Electrical Engineering, for calculating the parameters of symmetrically coupled vertical microstrip lines placed between two infinite grounded planes. Even and odd modes are taken into account and the quasi TEM analysis is applied. A computer code has been written to obtain numerical solutions for the observed microstrip lines. The characteristic impedance and the effective dielectric permittivity will be determined and compared to corresponding ones obtained by the finite element method. All results will be given in tables and presented graphically. The basic idea of the hybrid boundary element method is that an arbitrary shaped electrode can be replaced by equivalent electrodes. Also, an arbitrary shaped boundary surface between any two dielectric layers can be replaced by discrete equivalent total charges per unit length placed in the air. The discretization technique is similar to the method of moments and is not new, but combined with a new variant of the boundary element method and the equivalent electrodes method can be applied for solving large number of very complex 2D microstrip lines with or without symmetry. The hybrid boundary element method can be also successfully applied to 3D problems solving. View full abstract»

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  • Magnetic and thermal sizing of a quadrupolar superferric magnet

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1300 KB) |  | HTML iconHTML  

    This paper presents the magnetic and thermal sizing of the prototype of an YBCO quadrupolar superferric magnet (QSM) for high gradient magnetic field. The design of an optimal polar piece is first addressed. Simpler 2D models are used to find design level details on the magnetic field spectra. Next, the heat transfer problem is solved. The heat leakage from the ambient is a menace to the QSM superconductive operation, and radiation heat transfer plays a major role. 2D models are not an option therefore a 3D geometry imported from the CAD design of the prototype is used as computational domain. The numerical simulation results evidence the heat transfer paths within the structure, and they are used in sizing the magnet. View full abstract»

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  • Static force characteristic of e-type single phase AC electromagnets

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (407 KB) |  | HTML iconHTML  

    In this paper, we propose an approach for the determination of static force characteristic of E-type single phase AC electromagnet using 2D numerical models developed in QuickField and FEMM software. The magnetic attraction force is estimated using Maxwell stress tensor method. The results obtained with numerical models were validated by an analytical method combined with experimental data. The numerical model is an AC magnetics problem coupled with the coil electric circuit. Necessary experimental data are electromagnet coil current values at different air gaps for a known voltage. Also, the ohmic resistance of the coil, the number of turns and wire diameter are known. The numerical results for attraction force obtained in QuickField agree well with those obtained by analytical method combined with experimental data. The correspondent numerical values obtained in FEMM do not match with them, although the air gap magnetic flux density values are practically identical to those obtained in QuickField. More specifically, the numerical values obtained in FEMM for attractive force are half of QuickField values. Considering the distribution of magnetic flux density on polar surfaces and using Maxwell formula in its integral form for calculating the force, it was proved that the numerical values of force are in very good conformity with those obtained in QuickField. The authors point out that in software FEMM the AC force is wrongly calculated based on Maxwell stress tensor method although in DC this calculation is correct. View full abstract»

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  • Deep slot constriction conductance

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    In the paper, the 2D fringing magnetic flux in front of a gap, in an infinitely deep slot is studied using conformal mapping and exact formulas are proposed for transversal geometrical conductances, permeances or capacitances, as well as longitudinal resistance of the gap. Two configurations are considered: wide and narrow gap. View full abstract»

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  • Analysis of electrostatic environment and discharge models

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (406 KB) |  | HTML iconHTML  

    Interferences produced by the electrostatic discharges (ESD) events are sources of multiple failures and malfunction of electric and electronic equipment. To reduce the negative impact, a clarification of ESD processes is proposed. The paper deals with the analysis of charging/discharging processes and the establishing methods to reduce the risk of electrostatic discharge. For the contact electric charging, a comparative analysis of the material properties is done. Different ESD models are discussed and, waveforms of discharge current for these models are obtained, as basis for designing the standard testing simulators. View full abstract»

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  • Testing equipment to electrostatic discharge. Case study-communication cables

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (394 KB) |  | HTML iconHTML  

    The paper deals with the analysis of the characteristics of electrostatic discharges (ESD) processes and the impact of ESD to the performances of equipment, especially to the communication cables. ESD current models are analyzed, and, in conformity with basic standards in this field the measuring methods of the discharges are applied. The comparative results for unshielded and shielded cables are done. The experimental determinations show that the cable shielding offers an improvement to their functionality, but it does not totally eliminate the probability to damage on the electrostatic discharge actions. New mitigation techniques should be developed. View full abstract»

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  • Modeling and simulation of electromagnetic conducted emissions from buck converter with resistive load

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (294 KB) |  | HTML iconHTML  

    The paper deals with the modeling and simulation of conducted emissions from a buck converter switch mode power supply which operates at a switching frequency of 100 kHz. The design of a buck converter is also presented, its operation being afterward simulated. The corresponding waveforms demonstrate the proper operation. The switch control is performed with a 0.5% duty cycle PWM technique. The studied ideal switch is modeled using a MOSFET model. The study of conducted emissions produced by a buck converter considered a constant impedance and a frequency range 150 kHz - 30 MHz. To meet the measurements standards, the line impedance stabilization network is simulated and the results are compared with the CISPR 16-1-2 standard. The variations of the impedance over the 150 kHz - 30 MHz frequency range are plotted. The compatibility between the line impedance stabilization network (LISN) and the measurement standard CISPR 16-1-2 is evaluated. One also performs an analysis in the frequency domain of the measured noise signal produced by the buck converter. The results are presented both in RMS value and in dBμV and comparisons are made considering the Europeans standards. Finally, some methods of reducing the conducted emissions are suggested (e.g. the using of snubber circuit type, filtering etc). View full abstract»

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  • About the EMC of non-conventional electronic instrument transformer Case study

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB) |  | HTML iconHTML  

    The modernization of the control, monitoring, measurement and protection equipment from electric power grid has been for a long time a normal process which at present is much accelerated by the spreading of smart grid, sustained by the existence of the new generation of equipment, containing low signal, electronic modules/ subassemblies, like the voltage and current non-conventional instrument transformers (NCIT), merging units or modern information transmission systems . Assurance of electromagnetic compatibility (EMC) and especially of the immunity of this inherently sensitive equipment in severe electromagnetic environment, specific to electric substations, is a very important requirement because it determines the compliant operation, under normal or failure duty, of the measurement, protection, monitoring a.s.o. functions. In this paper there are approached the EMC issues related to non-conventional instrument transformers by the presentation of EMC requirements provided in the specific standards in force and also in those ones under approval, followed by an analysis of the application difficulties (high sizes, voltages, currents) and a reporting of the sources of possible uncertainty regarding the test results. Further on, it is presented a case study referring to EMC tests for a 24 kV, 200 A electronic current transformer developed at ICMET Craiova. View full abstract»

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  • The coal conveyor celts functioning modelling of the energy block by 330 MW

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (535 KB) |  | HTML iconHTML  

    In this paper, the authors, with Matlab - Simulink programs help, achieve the energy performances modelling of the mills conveyor belts, that assure the fuel flow require to the energy block functioning by 330 MW, for three characteristic loads: 96%, 82% and 65%. In this purpose, starting up real, functional and constructive parameters of the six coal conveyor belts and, considering the constant transported coal density, with computer simulation help, the variation curves of the power absorbed by gear motors of the coal conveyor belts were traced in function of the usual speed of their functioning. A calculation algorithm, which is based on the simulation, aims at determining idle consumption of the conveyor belt and values for different power consumption categories, such as: for horizontal movement of the material transported, for vertical movement of the material, for overcoming friction between the conveyor belt and the discharge chute guides, for overcoming resistance of the belt unloaders of type two drums. Based on these powers calculated and taking into account the belt transmission speed variation, the variation graphs for the powers absorbed from the electric network have been withdrawn the MATLAB-SIMULINK Program. View full abstract»

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  • Parallel operation of combined heat and power plants and wind farms

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    The paper evaluates the potential for parallel operation of conventional power plants and wind farms. In this way it is possible to identify the best possible methods that would allow the integration of the wind turbines into the energy production mix. The paper shows that the parallel operation of wind turbines and conventional plants within a system is possible and reduces the negative effects of the integration of renewable sources in the energy system. In this case, if the conventional power plant compensates the power variations of the wind farm, then the specific investment necessary for the energy storage decreases thus leading to a smaller specific investment for the construction of the wind farms. The results reveal the necessity of a differentiated CO2 emission tax calculated at system level and not at the level of the conventional power plants. This is important because sometimes the increased CO2 emissions of the conventional power plants might lead to an overall decrease of the CO2 emissions at system level (for example when conventional plants are operating at partial loads in order to allow an increased electricity production of the wind turbines). In this case calculating the CO2 emissions for the entire system leads to a smaller increase of the price of the electrical energy, thus decreasing the negative effect of the construction of new wind farms. View full abstract»

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  • Thermal analysis of underground power cables-A monitoring procedure

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB) |  | HTML iconHTML  

    The implementation of underground power distribution lines grown significantly over the last decades and this has increased to need to obtain a high level of operational reliability. Current monitoring strategies for underground power lines are developed based on different diagnosis tools and many of them are not cheap at all. As an example, traditional methods of thermal endurance characterization for XLPE insulated power cables are all based on analytical tools-infrared carbonyl absorbance, melting point, differential scanning calorimetry and others. These diagnosis techniques are either too time consuming or some can only give vague data that cannot be interpreted. The current paper proposes a new method for underground power cable monitoring based on cable historical operation temperature. Based on the current study, the aim of this innovative monitoring procedure is to estimate the degree of ageing for an underground power cable considering thermal stresses. Different parameters related to thermal aging are determined such as daily thermal aging and the average daily rate of aging. The input data considered for the current researches are chosen arbitrarily, but it can be switched with real data from exploitation. For thermal life-time estimation, the thermal endurance profile for XLPE was applied. The current procedure can be applied either paper insulated or XLPE insulated power cables. View full abstract»

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  • Phase coordinates system versus orthogonal reference frame in control of shunt active filtering systems

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (241 KB) |  | HTML iconHTML  

    This paper is focused on the implementation of the different theories of powers and current decomposition methods in the compensating current calculation for three-phase three-wire shunt active filtering systems. They are grouped into two categories, depending on the type of coordinate system used in the processing measurements involved in calculations. The former is based on the phase coordinates system and includes the theories of Fryze, Fryze-Buchholz-Depenbrock as well as the so-called generalized theories of instantaneous reactive and non-active powers. The latter refers to the orthogonal reference frame-based approaches such as the p-q theory and id-iq method. The applicability of each theoretical approach in the control of a shunt active power filter was analyzed through a lot of simulations on a Matlab-Simulink platform purposely developed by authors. Both the operation of the active filtering system under sinusoidal and nonsinusoidal voltage conditions are taken into consideration. It is shown that all formulations based on the powers flow can lead to unity power factor after compensation when the supply voltage is not distorted. Finally, conclusions are drawn by analyzing the capability of each method to meet different compensation objectives in any conditions of the supply voltage and taking into consideration the complexity of the calculations required in implementation. View full abstract»

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  • Integrated didactic software package for computer based analysis of power quality

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (592 KB) |  | HTML iconHTML  

    The actual state and operation of the Romanian power system ask for a certain expertise in detecting the causes of electromagnetic perturbations and their evaluation in power grids. Consequently, all the aspects regarding the power quality issues became a common characteristic of the power systems' curricula within Romanian power engineering faculties. The students attending these classes are involved in computer-based laboratory works. This paper describes the authors' contribution regarding the development of an integrated software package for power quality analysis at the Faculty of Electrical Engineering, University of Craiova. This software structure is built on a link between professional specialized software packages and software subroutines conceived by the authors. The parameters related to voltage/current harmonics can be analyzed using MATLAB subroutines and EDSA package - Electrical Power System Design Software. The results can be visualized as different types of reports. They can be further exported to EDSA program or/and MATLAB subroutine in order to size the harmonic filters and evaluate their effect on power quality in the analyzed power grids. EDSA programs package, as well as the subroutines developed in MATLAB environment are traditional tools used by the students attending the Power Quality classes within the Faculty of Electrical Engineering. View full abstract»

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  • Comparative study on power transformers vegetable and mineral oil ageing

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB) |  | HTML iconHTML  

    Due to the increasing need to replace the petroleum based products, there's an interest in replacing the mineral insulating oil for electrical equipment with biodegradable vegetable oil. This paper presents a comparative experimental study concerning the ageing of mineral and vegetable oils used in power transformers. In this view, samples of mineral and vegetable oil were accelerated thermally aged, and their dielectric properties (real part of the complex relative permittivity, loss factor and resistivity) were determined at different ageing times. The evolution of the degradation process in time was studied by determining the dielectric properties variation rate. The results show that the values of the relative permittivity and loss factor determined for new oil are higher in the case of vegetable oil than for the mineral oil, and vegetable oil's resistivity is lower than that of mineral oil. It has been determined that during the ageing process the color of the mineral oil samples visibly changes with the ageing time, while in the case of vegetable oil samples, these changes are not significant. Also, the variation rate of vegetable oil's real part of relative permittivity, loss factor and resistivity is decreasing in time, while that of mineral oil has an increasing tendency. View full abstract»

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