SERBIAN JOURNAL OF ELECTRICAL ENGINEERING
Vol. 12, No. 2, June 2015
CONTENTS
Influence of Various Structural Factors of Claw Pole Transverse Flux Permanent Magnet Machines on Internal Voltage using Finite Element Analysis
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1.13 MB)
DOI: 10.2298/SJEE1502129A
Abstract: This paper presents the influence of several structural factors and parameters involved in the design of Claw Pole Transvers Flux Permanent Magnet Machines (TFPMs) on their internal voltage. Knowing the influence of each factor is very important for an effective process of design and optimization for these machines. In this paper by using the complete design algorithm of Claw Pole TFPM, only one parameter is changed at a time and its influence on the internal voltage is analyzed. Output torque is also studied, because the internal voltage has effect on both the average and the ripple of output torque. The most important factors and parameters which are considered are: 1) number of poles; 2) length of air gap; 3) ratio of magnet arc to flux concentrator arc in each pole of rotor; 4) shape of pole shoe of stator and 5) area of rotor pole covered by stator pole. Due to geometrical complexities of TFPMs, analytical methods fail to describe the behavior of these machines. For this reason, in this paper finite element analysis is used both in the design and analysis of TFPMs.
Keywords: Claw pole transverse flux permanent magnet machine, Design optimization, Finite element analysis, Internal voltage, Output torque.
Optimal Power Flow for Distribution Networks with Distributed Generation
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DOI: 10.2298/SJEE1502145R
Abstract: This paper presents a genetic algorithm (GA) based approach for the solution of the optimal power flow (OPF) in distribution networks with distributed generation (DG) units, including fuel cells, micro turbines, diesel generators, photovoltaic systems and wind turbines. The OPF is formulated as a nonlinear multi-objective optimization problem with equality and inequality constraints. Due to the stochastic nature of energy produced from renewable sources, i.e. wind turbines and photovoltaic systems, as well as load uncertainties, a probabilisticalgorithm is introduced in the OPF analysis. The Weibull and normal distributions are employed to model the input random variables, namely the wind speed, solar irradiance and load power. The 2m+1 point estimate method and the Gram Charlier expansion theory are used to obtain the statistical moments and the probability density functions (PDFs) of the OPF results. The proposed approach is examined and tested on a modified IEEE 34 node test feeder with integrated five different DG units. The obtained results prove the efficiency of the proposed approach to solve both deterministic and probabilistic OPF problems for different forms of the multi-objective function. As such, it can serve as a useful decision-making supporting tool for distribution network operators.
Keywords: Optimal power flow, Distribution network, Distributed generation, Genetic algorithm, Point estimate method.
Fuzzy Logic Based Control System for Fresh Water Aquaculture: A MATLAB based Simulation Approach
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DOI: 10.2298/SJEE1502171R
Abstract: Fuzzy control is regarded as the most widely used application of fuzzy logic. Fuzzy logic is an innovative technology to design solutions for multi-parameter and non-linear control problems. One of the greatest advantages of fuzzy control is that it uses human experience and process information obtained from operator rather than a mathematical model for the definition of a control strategy. As a result, it often delivers solutions faster than conventional control design techniques. The proposed system is an attempt to apply fuzzy logic techniques to predict the stress factor on the fish, based on line data and rule base generated using domain expert. The proposed work includes a use of Data acquisition system, an interfacing device for on line parameter acquisition and analysis, fuzzy logic controller (FLC) for inferring the stress factor. The system takes stress parameters on the fish as inputs, fuzzified by using FLC with knowledge base rules and finally provides single output. All the parameters are controlled and calibrated by the fuzzy logic toolbox and MATLAB programming.
Keywords: Fuzzy logic controller, Fuzzy interference systems, ANFIS.
Series PID Pitch Controller of
Large Wind Turbines Generator
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DOI: 10.2298/SJEE1502183M
Abstract: For this stable process with oscillatory dynamics, characterized with small damping ratio and dominant transport delay, design of the series PID pitch controller is based on the model obtained from the open-loop process step response, filtered with the second-order Butterworth filter Fbw. Performance of the series PID pitch controller, with the filter Fbw, is analyzed by simulations of the set-point and input/output disturbance responses, including simulations with a colored noise added to the control variable. Excellent performance/robustness tradeoff is obtained, compared to the recently proposed PI pitch controllers and to the modified internal model pitch controller, developed here, which has a natural mechanism to compensate effect of dominant transport delay.
Keywords: PID pitch control, Wind turbines generator, Oscillatory dynamics, Dominant dead-time, Modified internal model control.
Very Compact UWB Antenna
with Group Delay Improvement
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DOI: 10.2298/SJEE1502197T
Abstract: In this paper, very compact (12mm×17mm) and simple UWB antenna is proposed. The achieved bandwidth of the presented antenna is from 3.05 GHz to 12.5 GHz and in the most of the bandwidth, the return loss is less than –20dB. In addition to frequency characteristics, time characteristics such as group delay variations for three different antenna positions, namely, front to front, back to back and side by side using CST MW studio are simulated and discussed. To improve the group delay variations, by changing the radius of the circle on the back side of the antenna, the antenna gain in different frequencies will be tuned, therefore, the time domain characteristics of the proposed antenna are greatly improved.
Keywords: UWB antenna, Group delay variation, Gain.
Sliding Mode Controller for Four Leg Shunt Active Power Filter to Eliminating Zero
Sequence Current, Compensating Harmonics and
Reactive Power with Fixed Switching Frequency
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DOI: 10.2298/SJEE1502205C
Abstract: In this paper, the four leg inverter controlled by the three dimensional space vector modulation (3D SVM) is used as the shunt active power filter (SAPF) for compensating the three phase four wire electrical network, by using the four leg inverter with 3D SVM advantages to eliminated zero sequence current, fixed switching frequency of inverter switches, and reduced switching losses. This four leg inverter is employed as shunt active power filter to minimizing harmonic currents, reducing magnitude of neutral wire current, eliminating zero sequence current caused by nonlinear single phase loads and compensating reactive power, and a nonlinear sliding mode control technique (SMC) is proposed for harmonic currents and DC bus voltage control to improve the performances of the three phase four wire four leg shunt active power filter based on Synchronous Reference Frame (SRF) theory in the dq0 axes, and to decoupling the four leg SAPF mathematical model.
Keywords: Shunt active power filter, Space vector modulation, Sliding mode control, Synchronous reference frame.
Implementation of Control Logic
in the Scoreboard of Tennis
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DOI: 10.2298/SJEE1502219I
Abstract: This paper presents one original solution of control logic for score¬board in tennis match. The main goal is to simplify the process of recording points. Instead of using six buttons the chair umpire (referee) will use only two control buttons or a joystick to assign a point to a player. The proposed system takes care of all other data processing. The system is designed in Application Specific Integrated Circuits (ASIC) and Standard Application Specific Integrated Circuits (SASIC) technology to demonstrate similarities and differences between two design technologies. Finally it is realized on FPGA type EP2C35F672C6 from Cyclone II Altera’s family.
Keywords: Application Specific Integrated Circuit, Standard Application Specific Integrated Circuit, Tennis scoreboard.
Modeling the Effect of the Stress Demagnetization Phenomenon on the Magnetic Properties in a NO Fe-Si 3% Sheet
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DOI: 10.2298/SJEE1502237Y
Abstract: The aim of this paper is the modeling of the stress demagnetization effect on the magnetic properties in a non-oriented Fe-Si 3% sheet under different external stresses. The magneto-mechanical model used for magnetic hysteresis is based on a model originally formulated by Sablik-Jiles-Atherthon (S.J.A.). This latter has been modified by including both the stress demagnetization factor and the eddy current effects. The influence of the stress demagnetization term SDT on the magnetostrictive behavior of the material is also modeled. The proposed model has been validated by extensive simulations at different stresses, namely compressive and tensile stresses. Simulation results obtained by this model are very close to those published in the literature. Using the proposed model, very satisfactory performance has been achieved.
Keywords: Magneto-mechanical model, Stress demagnetization effect, Eddy current, Magnetic properties, Magnetostriction, NO Fe-Si 3% Sheets.
Estimation of Similarity between Functions Extracted from x86 Executable Files
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DOI: 10.2298/SJEE1502253B
Abstract: Comparison of functions is required in various domains of software engineering. In most domains, comparison is done using source code, but in some domains, such as license violation or malware analysis, only binary code is available. The goal of this paper is to evaluate whether the existing solution meant for ARM architecture can be applied to x86 architecture. The existing solution encompasses multiple approaches, but for the purpose of this paper three representative approaches are implemented; two are based on machine learning, and the third does not require previous knowledge. Results show that the best recalls obtained for the first ten positions on both architectures are comparable and do not differ significantly. The results confirm that adaptation of all approaches of the existing solution is not only possible but also promising and represent adequate basis for future research.
Keywords: Code analysis, Binary code, Software clones, Similarity assessment.