Showing papers in "Journal of Electrical Engineering-elektrotechnicky Casopis in 2013"

Modelling of classical and rotary inverted pendulum systems - a generalized approach

Abstract: The purpose of this paper is to present the design and program implementation of a general procedure which yields the mathematical model for a classical or rotary inverted pendulum system with an arbitrary number of pendulum links. Lagrange equations of the second kind with an integrated Rayleigh dissipation function are employed in model design, and the energetic balance relations, derived for the base and all pendulum links in a generalized (n-link) classical and rotary inverted pendulum system, are implemented in form of symbolic MATLAB functions and a MATLAB GUI application. The validity and accuracy of motion equations generated by the application are demonstrated by evaluating the open-loop responses of simulation models of classical double and rotary single inverted pendulum. K e y w o r d s: inverted pendulum systems, automated mathematical modelling, Lagrange mechanics, symbolic MATLAB functions, classical double inverted pendulum, rotary single inverted pendulum

Swinging up the Furuta Pendulum and its Stabilization Via Model Predictive Control

Abstract: This paper deals with certain options on controlling an inverted rotary pendulum also known as the Furuta pendulum. Controlling an inverted pendulum involves two stages. The first stage is the swing up of the pendulum and the second stage is its balancing in the up-right position. The paper describes two possibilities on swinging up the pendulum. First one is the classical approach based on comparing the current total (potential and kinetic) energy of the system with the energy in its stabilized up-right position. The second option uses an exponentiation operation over the pendulum position since the trend of power law function is very convenient for determining the amount of required energy to be delivered to the system. For the purposes of balancing the pendulum in the up-right position a predictive controller based on optimal control law with perturbation was proposed, which is an LQ controller with control signal corrections when constraints are exceeded. The results are illustrated by real-time experiments on a laboratory rotary inverted pendulum setup.

New double current controlled cfa (dcc-cfa) based voltage-mode oscillator with independent electronic control of oscillation condition and frequency

Abstract: In this paper, a new electronically tunable quadrature oscillator (ETQO) based on two modified versions of current feedback amplifiers (CFAs), the so called double current controlled CFA (DCC-CFAs) is presented. The frequency of oscillation (FO) of the proposed voltage-mode (VM) ETQO is electronically adjustable by current gain or by varying the intrinsic resistance of the X terminal of the active element used. The condition of oscillation (CO) is adjustable by current gain independently with respect to frequency of oscillation. Simultaneous control of current gain and intrinsic resistance allows linear control of FO and provides extension of frequency tuning range. In the proposed circuit all the capacitors are grounded. The use of only grounded capacitors makes the proposed circuit ideal for integrated circuit implementation. The presented active element realized by using BiCMOS technology and the behavior of proposed circuit are discussed in details. The theoretical results are verified by SPICE simulations based on CMOS ON-Semi C5 0.5 µm and bipolar ultra high frequency transistor arrays Intersil HFA 3096 process parameters. K e y w o r d s: electronic control, sinusoidal oscillator, current feedback amplifier (CFA), double current controlled CFA (DCC-CFA)

Measurement Systemwith Hall and a Four Point Probes for Characterization of Semiconductors

Abstract: This article describes the design, construction and control program of an automatic measuring system (AMS), which was designed for sheet resistance and sheet Hall mobility measurements. The van der Pauw technique and 4-point probe method are used to measure sheet resistance and calculate the specific resistance. Furthermore, the software of the AMS contains graphical subroutines for conversion of resistivity to concentration and mobility. Hall effect and electronic transport measurements are invaluable for understanding and characterization of the physical properties of semiconductors such as Si, GaAs, ZnO, and nanocrystal diamond as well as other electronic and magnetic materials. An important part in production of electronic components and integrated circuits is the diagnostics of basic material parameters. The van der Pauw method is one of the most utilized measurement methods for evaluation of the semiconductor material electrical properties, such as resistivity, carrier density, and mobility [1]. Method can be used to measure samples of arbitrary shape, although several basic sample conditions must be satisfied to obtain accurate measurements. Among them the most important are good homogeneity of the sample, constant thickness of the sample and in ideal case infinitive small point contacts placed at the edges of the samples [2]. Moreover, the quality of contact in terms of good ohmic behavior has to be assured. The van der Pauw method is a common method used for investigation of new prepared thin films to determine their quality. Characterizing the mobility of new materials is essential for semiconductor technology innovations, so making accurate Hall effect measurements will continue to be important [2]. Additional resistivity measurement method, the 4point probe, is also widely used in the semiconductor industry to monitor the production process. Electrical measurements are done on test structures to provide information on the various process steps. For example, resistivity measurements of doped semiconductor structures provide information about the carrier concentration and mobility and are used as feedback for the doping diffusion process [3]. This paper describes an AMS with Hall and the 4point-probe method. Optimum measurement conditions for determination of mobility µ are established for different semiconductor layers and structures. Hall effect is invaluable to understand and characterize the physical properties of semiconductors including materials such as: Si, Ge, GaAs, AlGaAs, ZnO, and others. Transport measurements of Hall effect and magnetoresistance are ideally suited for material research, product development, and quality control [2,45]. 2 THEORY The designed automatic measuring system can be used to determine several material parameters: the Hall voltage (VH), carrier concentration (n), Hall coefficient (H) and the conductivity type (n or p) are all derived from the Hall voltage measurement. To be able to evaluate carrier mobility (µ) it is necessary to measure also the resistivity of the sample (�). Due to the required contact node arrangement shown in Fig. 1, the van der Pauw method is the most frequently used method in the Hall measurement systems to evaluate the sample resistivity.

An Application of Artificial Neural Network to Compute the Resonant Frequency of E–Shaped Compact Microstrip Antennas

Abstract: An application of artificial neural network (ANN) based on multilayer perceptrons (MLP) to compute the resonant frequency of E-shaped compact microstrip antennas (ECMAs) is presented in this paper. The resonant frequencies of 144 ECMAs with different dimensions and electrical parameters were firstly determined by using IE3D (tm) software based on the method of moments (MoM), then the ANN model for computing the resonant frequency was built by considering the simulation data. The parameters and respective resonant frequency values of 130 simulated ECMAs were employed for training and the remaining 14 ECMAs were used for testing the model. The computed resonant frequencies for training and testing by ANN were obtained with the average percentage errors (APE) of 0.257 % and 0.523 %, respectively. The validity and accuracy of the present approach was verified on the measurement results of an ECMA fabricated in this study. Furthermore, the effects of the slots loading method over the resonant frequency were investigated to explain the relationship between the slots and resonant frequency. K e y w o r d s: compact microstrip antenna, E-shaped antenna, resonant frequency, artificial neural network (ANN)

A Comparative Study Between Direct Torque Control and Predictive Torque Control for Axial Flux Permanent Magnet Synchronous Machines

Abstract: This paper presents a comparative study between direct torque control (DTC) and predictive torque control (PTC) of Axial Flux Permanent magnet Machines (AFPM). In conventional DTC method for permanent magnet machines, only six actives voltage vectors of inverter are used to control torque and flux of machine. But in predictive torque control, in addition to six active voltage vectors, zero voltage vectors are used to control machine. So number of voltage vectors to control AFPM increases that leads to lower ripple of torque and flux. In predictive torque control, the response of torque and flux are computed for all possible switching states of inverter at every sample time according to discrete time model of machine, and then the switching state that optimizes ripple of torque and flux, will be applied in next discrete-time interval. Simulation results which compare the results of implementation of both methods and confirm the good performance of the proposed predictive torque control are presented.

Mobile Robot Navigation Based on Circle Recognition

Abstract: This paper presents a navigation method for a mobile robot using a visual system Circular marks with specific colors are used for marking the significant points of the mobile robot’s trajectory that it needs to pass The colors of the used marks are signalizing the way of their bypassing with the mobile robot (from the left or right side) The mobile robot uses only one camera for the marks recognition task and it is able to determine its own relative position from the detected marks The image processing and the mobile robot’s trajectory planning algorithm working in real-time are described in this paper K e y w o r d s: circular mark detection, mobile robot trajectory planning, image processing, Hough transform The aim of this paper is to propose a navigation method for a mobile robot using a visual system that consists of only one ordinary camera (web camera) The algorithm should be able to determine the relative position between the mobile robot and the detected marks and to plan the mobile robot’s trajectory to bypass the marks from a desired side Most of visual system applications are using stereo vision techniques for object’s position determination In this paper the position of the mobile robot relative to the detected mark is computed using only one camera with unknown optical parameters The navigation consists of two main parts: the image processing part and the trajectory planning part Image processing part is a combination of more image processing algorithms (steps) and its goal is to detect all the circular marks in an unknown environment while the changing of light conditions is possible This part also determines the colors of the detected marks Changing of the light conditions is an important disturbance bringing noise into the image processing Therefore the image processing application needs to be designed the way to be able to troubleshoot this disturbance Trajectory planning part is computing the positions of the detected marks relative to the position of the mobile robot using the data obtained with image processing part After it the mobile robot’s trajectory is planned using ? +

Mechanical Behavior and Thermal Stability of EVA Encapsulant Material Used in Photovoltaic Modules

Abstract: The mechanical behavior and the thermal stability of an encapsulant based on ethylene-vinyl acetate (EVA) were studied. The EVA properties were verified at temperatures ranging from −70 ◦ C to 500 ◦ C. Thermogravimetry, differential scanning calorimetry and dynamic mechanical analysis were used in this study. It has been shown that the encapsulant has a good weight stability; however, the encapsulant passes through both a glass transition and a melting phase in the range of operating temperatures. The kinetic parameters of crosslinking were also analyzed. It is possible to achieve 65% crosslinking at a temperature of 150 ◦ C and a time of 5 minutes. The activation energy of crosslinking is 95.6 kJ/mol. K e y w o r d s: renewable energy resources, photovoltaic, EVA, encapsulant, glass transition, thermal analysis

Precise Assessment of Performance of Induction Motor under Supply Imbalance Through Impedance Unbalance Factor

Abstract: This paper presents precise assessment of steady-state performance of induction motor (IM) operating under voltage unbalance. The variation of two voltage unbalance factors viz. complex voltage unbalance factor (CVUF) and impedance unbalance factor (IUF) with positive sequence voltage component, reveals that degree and manner of unbalance in supply voltage is exactly reflected in CVUF and IUF, respectively. On this basis, it is shown that for the precise assessment of IM performance, knowledge of both, manner (IUF) and degree (CVUF) of unbalance is important. Further, effect of angle of unbalance, on the performance of the IM and voltage pattern is analyzed. Results depict high sensitivity of derating factor and peak copper losses to this angle. Thus, it should be included along with unbalance factors for the precise and complete performance assessment of IM.

Distribution Network Reconfiguration Considering Power Losses and Outages Costs Using Genetic Algorithm

Abstract: This paper discusses the problem of finding the optimal network topological configuration by changing the feeder status. The reconfiguration problem is considered as a multiobjective problem aiming to minimize power losses and total interruptions costs subject to the system constraints: the network radiality voltage limits and feeder capability limits. Due to its complexity, the metaheuristic methods can be applied to solve the problem and often the choice is genetic algorithm. NSGA II is used to solve the multiobjective optimization problem in order to get Pareto optimal set with possible solutions. The proposed method has been tested on real 35 kV distribution network. The numerical results are presented to illustrate the feasibility of the proposed genetic algorithm.

Development of Smart Underfrequency Load Shedding System

Abstract: The paper describes possibility to apply innovation technology of Smart Grid for power system emergency automation. Operational characteristics of existing emergency automation and new suggested one are compared in the paper. The method for liquidation of drawback of existing automation is suggested. The paper describes the developed mathematical model of intellectual underfrequency load shedding system and its operational algorithms. Emergency automation is a major part of the power system. The operation of any emergency automation is based on the metering of certain parameters and reaction corresponding to the operational algorithm. Many types of emergency automation and control systems are used in the power system. They differ with functionality, design, etc. Some types of emergency automation use simple equations, other types — complex algorithms. However, they all have one common initial condition — receiving

Robust Control Methods a Systematic Survey

Abstract: The paper addresses the problem how to recognize a level of robust controller design and is aimed show the difficulties of implementation for practical use. In the first part of paper we introduce the survey of robust controller design for SISO systems with generalization design procedure for structured and unstructured uncertainties. The second part of paper is devoted to MIMO systems. In the frequency domain robust controller design procedure we reduce to independent design of SISO subsystems and in time domain the LMI or BMI approaches with polytopic system description are favorable.

Adaptive Neural Controller for Maximum Power Point Tracking Of Ten Parameter Fuel Cell Model

Abstract: Nonlinear characteristic and internal behavior of the Proton Exchange Membrane (PEM) Fuel Cells under different load conditions is of paramount importance. This paper presents an adaptive neural controller based on a back-propagation algorithm for maximum power control of PEM fuel cell system. The system consists of a buck-boost converter connected to the fuel cell. The adaptive neural controller receives the error and change of error signals as inputs during load changes and generates the DC-DC converter duty cycle. By using the inference, the duty ratio of the buck-boost converter is controlled so that the fuel cell can provide the maximum power. The ANN controller monitors also the temperature, the pressure and the cell voltage. In this paper the dynamic model for proton exchange membrane fuel cells using ten parameter model is used. The model has been implemented in MATLAB/SIMULINK. Both the double-layer charging effect and the thermodynamic characteristic inside the fuel cell are included in the model.

Random Binary Sequences in Telecommunications

Abstract: Realization of modern telecommunication systems is inconceivable without use of different binary sequences. In this paper, an overview of random binary sequences used in different telecommunication systems is given. Basic principles of pseudorandom, chaotic, and true random sequence generation are presented, as well as their application in telecommunications in respect to advantages and drawbacks of the same. Moreover, particular scheme for true random binary sequence generation is given, as well as results of randomness assessment obtained by NIST statistical test suite. Finally, short insight into importance of random binary sequence in secure communications is given.

Mössbauer Spectroscopy System with Increased Performance and Flexibility ––– Utilization In Material Research

Abstract: A new concept of Mssbauer spectrometer used for material research is presented. Performance of this computer based measurement system was carefully analyzed and programming code of the application step by step optimized. By implementation of parallel data processing the control application with zero dead-time of measurement was developed.

Evolutionary Algorithm for Calculating Available Transfer Capability

Abstract: The paper presents an evolutionary algorithm for calculating available transfer capability (ATC). ATC is a measure of the transfer capability remaining in the physical transmission network for further commercial activity over and above already committed uses. In this paper, MATLAB software is used to determine the ATC between any bus in deregulated power systems without violating system constraints such as thermal, voltage, and stability constraints. The algorithm is applied on IEEE 5 bus system and on IEEE 30 bus system.

Control and Fault Diagnosis Based Sliding Mode Observer of a Multicellular Converter: Hybrid Approach

Abstract: In this article, the diagnosis of a three cell converter is developed. The hybrid nature of the system represented by the presence of continuous and discrete dynamics is taken into account in the control design. The idea is based on using a hybrid control and an observer-type sliding mode to generate residuals from the observation errors of the system. The simulation results are presented at the end to illustrate the performance of the proposed approach. K e y w o r d s: multicellular converter, diagnosis based-observer, hybrid observer, residual, cell fault sliding mode, hybrid dynamical systems

Dipole Near Field Analysis – A Closed Form Calculation in Cartesian Coordinates

Abstract: In many areas of an electrical engineering like measurement of the electromagnetic fields, antenna theory, etc one needs to quantify mutual effect between conductive elements which are in the electromagnetic field. We rely upon the EMF method, [1] as a classical method to compute self and mutual impedances. The induced opencircuit voltage (output) in conductive element 2, due to the radiation from conductive element 1 carrying current (input). The radiated field of conductive element 1 is usually calculated in cylindrical coordinates and the current distribution in conductive element 2 is estimated using antenna theory. Conductive elements are often arranged perpendicularly to a plane. If we want calculate the mutual impedance of such elements placed randomly in the space, more suitable may be the problem formulation and the near-field evaluation in Cartesian coordinates, particularly if we focus on the radial component. Besides this, the computation can be done without any approximation in a closed form as will be shown here. 2 CALCULATION OF NEAR FIELD OF THE ELECTRIC DIPOLE

Simulation and modelling of passivity based control of pmsm under controlled voltage

Abstract: The aim of the present paper is the study of the behaviour of passivity based control and difficulties due to synthesis for various operating conditions of a synchronous motor with a permanent magnets. The study takes into account the guarantee of satisfactory static and dynamic performance. It also allows the system to be insensitive to disturbances and uncertainties on the parameters. A number of estimation techniques have been developed to achieve speed and position sensorless permanent magnet synchronous motor (PMSM) drives. Most of them suffer from variation of motor parameters such as the stator resistance, stator inductance and torque constant. Also it is known that conventional linear estimators are not adaptive variations of the operating point in a nonlinear system. K e y w o r d s: passivity based control (PBC), Permanent magnet synchronous motor (PMSM), synthesis, voltage, modelling, simulation The use of electrical machines is expanding rapidly owing to their good performance. The control of machines is the primary concern of control theory research. In fact, an electrical machine is characterised by a non linear behaviour. Adding to that the major difficult tasks to be executed which require a higher precision under rapid trajectories. In order to meet performance criteria always in increase, algorithms of control more and more complex are developed. The progress is not sufficient thus a theory for non linear system is necessary. However, the non linear theory for general systems is complicated and seldom worthy in technological applications. But, from the accomplished works in these last three decades, aiming to improve performance advanced research had allowed emergence of new non linear control techniques for electrical machine application. In this context a method has been proposed in [1] allowing a new control PBC (Passivity Based Control). [2] et al. made similar development on robust passivity based control. Using a shaping of the total energy of the closed-loop system plus an injection of depreciation using the properties of energy dissipation system. The development of this method had allowed many improvements. It uses essentially Lagrangian structure of mechanical systems in order to make a decreasing Lyapunov function. It is necessary to know the position of the rotor. The stator currents of the PMSM are controlled to generate constant torque using the rotor position signal. It is possible to distinguish two fundamental steps while using passive control for a given system. The system modelling is put under the EL formalism and its (possible) passivity is used to create relations describing the stabilizing control. From these relations and by using a variety of techniques (control with variable structure a control based on average representation); the dynamic of the corrector is computed (if it exists) and the control value.

Performance of converters suitable for switched reluctance generator (srg) operation

Abstract: The paper deals with various kinds of converter topologies and their performances suitable for SRG operation. For each topology the equivalent circuit, mathematical model and simulation waveforms of phase variables are given. At the end of the paper the performances of individual converter topologies are compared and recommendations for their employment are given. K e y w o r d s: switched reluctance generator, converter, mathematical model, simulation

Design and EPGA Implementation of Digital Pulse Compression for Band–Pass Radar Signals

Abstract: The paper presents fully digitized approach for band-pass discrete coded radar signals. The emphasis is to use one generalized reconfigurable compressor for several different types of signals and different types of receivers. It fits for direct radio frequency receiver (RF) as well as for intermediate frequency (IF) receiver. The system implementation on field programmable gate area (FPGA) let us eliminate special chips previously needed. From the experimental results it is known that this approach appears to work well for matched and mismatched pulse compression and it outstands when timebandwidth product (TB) is of order 1000. A precision of 14 bits has been considered in the input signal and 16 bits in the filter coefficients. It gives the dynamic range of 78 dB and the quantification error less than 0.012%.

Multi Grid Chaotic Attractors with Discrete Jumps

Abstract: In this paper the discrete step functions are used in order to generate m×n scroll chaotic hypercube attractors. The design and realization of multi-scroll attractors depends on synthesizing the nonlinearity with an electrical circuit. The essence of the novel approach is in designing the transfer function with analog to digital converters connected directly without any microcomputer, instead of using standard comparator or hysteresis methods. Therefore there is no special need for synthesizing the nonlinearity towards m × n scroll chaotic attractors. The approach is verified with PSpice16.0 circuit simulator and experimentally measured. K e y w o r d s: multi grid scrolls, chaos, dynamical systems, integrator synthesis, digital converters

Three–Parameter Feedback Control of Amorphous Ribbon Magnetization

Abstract: This work describes a specially developed software for controllable magnetic hysteresis measurements of amorphous and nanocrystalline ribbons. The sophisticated algorithm enables to simplify a hardware design and to suppress an influence of experimental conditions on the measurement results. The main software feature is a three-stage feedback algorithm, which accurately adjusts the magnetization conditions: magnetization amplitude, geomagnetic bias and magnetization waveform. Air flux compensation of the induction signal is also performed by the software using an effective value of the coil cross section obtained from a calibration measurement without the ribbon. Applicability of the designed setup is illustrated for a series of nanocrystalline Hitperm ribbons measured at the power-line conditions: 50 Hz frequency and sinusoidal magnetization waveform.

The evaluation of the practical adhesion strength of biocompatible thin films by fuzzy logic expert system and international standards

Abstract: This work focuses on describing an evaluation method used in nano- and micro-thin films based on fuzzy logic expert systems. The aim is the elimination of comparison complications with mechanical properties of tin films, practical adhesion being one of the most important characteristic of tin films. The basic method for evaluating the practical adhesion strength is scratch test method, while the issue is that research teams use measurement methods based on the non-uniform measurement conditions of adhesion of biocompatible thin films. The authors tested new evaluation method and procedure based on international standards and fuzzy rule based expert system in order to eliminate the problem of comparison of practical adhesion of the films. The article concentrates on testing and using the fuzzy logic expert system designed based on international standards for evaluating adhesion of thin films in nano and micro dimensions. The materials used for tests of the fuzzy expert system were DLC biocompatible layers and substrate a titanium alloy Ti6Al4V. K e y w o r d s: international standards, fuzzy expert system, practical adhesion , scratch test, thin film

Cooling of Electrical Cu Conductor with PVC Insulation – Analytical, Numerical and Fluid Flow Solution

Abstract: This paper describes calculation of cooling process of electrical Cu conductor with PVC insulation Three types of solutions were performedAnalytical solution considers free convection and radiation effect of heat transfer Numerical solution was performed by finite element method (FEM) using software ANSYS Workbench and fluid flow solution was performed by computational fluid dynamics (CFD) analysis in software ANSYS CFX Results from all types of solutions were compared with results of the experimental measurement

Modelling and Examining Open Circuit Voltage for PEM Fuel Cells

Abstract: Fuel cells are ultimately one of the best promising devices that convert the potential energy in the reactants into the electrical energy after steps of sequential electrochemical processes with no hazards up on the environment. This paper presents comprehensive derivation and understanding of the electrochemical reaction for Polymer Electrolyte Membrane Fuel Cell (PEMFC) in terms of parameters and surrounding impacts, starting from the initial phenomena of splitting hydrogen molecule to the final mathematical model of open circuit voltage for PEMFC. The open circuit voltage has been derived and modelled for two operational conditions, when the output water from fuel cell is in liquid state, and when the output water is in state of vapour. Examining and analysing OCV under different operational temperature and pressure. Using pure oxygen instead of air has very small impact on increasing the OCV by 1% under same operational temperature and pressure; hence the use of pure oxygen is no longer defensible motive as this will increase the weight and cost of the system.

A multi-alphabet arithmetic coding hardware implementation for small fpga devices

Abstract: Arithmetic coding is a lossless compression algorithm with variable-length source coding. It is more flexible and efficient than the well-known Huffman coding. In this paper we present a non-adaptive FPGA implementation of a multi-alphabet arithmetic coding with separated statistical model of the data source. The alphabet of the data source is a 256-symbol ASCII character set and does not include the special end-of-file symbol. No context switching is used in the proposed design which gives maximal throughput without pipelining. We have synthesized the design for Xilinx FPGA devices and used their built-in hardware resources. K e y w o r d s: arithmetic coding, compression algorithm

Performance evaluation of harmonic current estimation using independent component analysis

Abstract: An augmented use of non-linear loads results in generation of harmonics, which is difficult to estimate in electric power systems. Using, Independent Component Analysis (ICA) methods like fastICA (FICA)the harmonic currents can be estimated without the knowledge of the topology of the system, particularly when the probability distribution of majority of the harmonic sources is non-gaussian. A typical scenario with all the harmonic sources close to Gaussian is considered and hence efficient variant fastICA (EFICA) algorithm is attempted in the paper. A harmonic state estimation using ICA is implemented on an IEEE 14 bus system and on a laboratory three bus model. A performance evaluation between the two methods of ICA for harmonic current estimation is done in the form of recording and evaluating the infinitesimal error that exists between the actual and estimated harmonic currents for the two interconnected bus systems. The graphical results of both the systems for the two methods also point to the superior performance of EFICA algorithm. Key wordsHarmonic State estimation;Mixing/Demixing matrix; FastICA;Efficient variant fastICA 1.Introduction: With the advent of power electronics, non linear loads are inherently present in power systems. The non linear loads inject harmonics into power system networks which propagate into the system. The methods available in literature for estimating the level of harmonics at different frequencies employ information on the topology of the interconnected network. However, using time structured Independent Component Analysis (ICA) the harmonic estimation can be carried out independent of the topology of the system [1-2]. One of the main assumptions for ICA is that only the probability density function of the source is known. Ekrem Gursoy et al suggested the use of ICA for estimating the harmonics in power system and did a theoretical simulation using FastICA algorithm [1].The FastICA algorithm is based on maximization of non-gaussianity. It is known to converge faster and is simpler to design owing to the absence of a learning parameter. In the presence of finite data samples, FICA’s validity is lost. The difference arises due to the variance of the samples which is well compensated in EFICA [3-4]. However, most of the non linear loads possess a near normal or gaussian probability distribution. An accurate harmonic estimation under such a scenario becomes significant. Hence, the EFICA algorithm which is suited for generalized gaussian distribution is attempted in this work. A simulation study is carried out on an IEEE 14 bus along with an experimental verification of the performance edge of EFICA on a three bus laboratory model. Section two discusses the problem formulation and its relation to harmonic state estimation along with the algorithms of FICA and EFICA. The technique for the generation of data and the brief mention of the sources of the IEEE 14 bus along with the method for implementing the algorithm is given in Section three. Section four gives the results of the current profiles obtained for an IEEE 14 bus system for both the algorithms along with analysis of the error. The descriptions of the three bus laboratory model along with the results of implementation of the two algorithms are presented in Section five. Section six lists the conclusions of the work and directions for future work. 2. Problem Formulation: 2.1 Basics of ICA Generally, the noiseless linear model of ICA problem is assumed as

Acoustic Properties of Magnetic Fluids Based on Transformer Oil Under Magnetic Field

Abstract: The structural changes in magnetic fluids based on transformer oil TECHNOL and MOGUL upon the effect of an external magnetic field and temperature were studied by acoustic spectroscopy. When a magnetic field is increased, the interaction between the magnetic field and the magnetic moments of the nanoparticles leads to the aggregation of magnetic nanoparticles and following clusters formation. However, the temperature of magnetic fluids has also very important influence on the structural changes because of the mechanism of thermal motion that acts against the cluster creation. The live time of clusters have relative long time scale for the magnetic fluid based on TECHNOL, while for MOGUL is quite short. K e y w o r d s: magnetic fluid, transformer oil, acoustic spectroscopy, clusters, magnetic field

Enhancement in steady state and dynamic performance of direct torque control induction motor drive

Abstract: An enhancement in dynamic performance of a traditional DTC drive can be achieved by a robust speed control algorithm while the steady state performance depends upon the switching strategy selected for minimization of torque ripples and an efficient flux control loop. In this paper a new torque ripple reduction technique with a modified look up table incorporating a larger number of synthesized non zero active voltage vectors is utilized to overcome the limitations of the conventionally controlled DTC drive. A fuzzy logic based speed controller and a low pass filter with tunable cutoff frequency for flux estimation is proposed in this paper. The proposed study is investigated through simulation and experimentally validated on a test drive. K e y w o r d s: direct torque control (DTC), induction motor, torque ripple minimisation, modified low pass filter, fuzzy logic