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International Review of Electrical Engineering  Vol. 5 N. 6-- Part A

International Review of Electrical Engineering  Vol. 5 N. 6-- Part B


International Review of Electrical Engineering - December 2010 (Vol. 5 N. 6) - Papers Part A


go to top     International Review of Electrical Engineering - December 2010 (Vol. 5 N. 6) - Papers Part B





International Review of Electrical Engineering - Papers- Part A


go to top   Analysis and Implementation of an Interleaved Buck Converter with High Power Factor
         by Bor-Ren Lin, Sin-Jhih Shen

           Vol. 5. n. 6, pp. 2508-2515


Abstract - An interleaved buck converter with discontinuous-conduction-mode (DCM) operation is presented to achieve power factor correction (PFC) and regulate DC bus voltage. Two buck converter cells are driven in the interleaved fashion. The current ripples at input and output sides are partially cancelled and the current stresses of semiconductors can be reduced. The buck PFC can improve the circuit efficiency across the wide line and load ranges compared to the efficiency of boost PFC circuit. The low output voltage can also reduce the voltage stress of semiconductor in the second DC/DC converter. Finally, the experimental results from a 260W prototype are presented to verify the effectiveness of the proposed converter.

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Keywords: Interleaved Pulse-Width Modulation (PWM), Buck Converter, Power Factor Correction.



go to top   Active Power Filter with Soft Switching
         by P. Brandstetter, P. Chlebis, P. Simonik

           Vol. 5. n. 6, pp. 2516-2526


Abstract - Active power filters have wide application for a control of harmonic currents from nonlinear loads. The paper describes used techniques, operation characteristics and information about an unconventional active power filter with soft switching. The active power filter is connected in parallel to the front end or AC input of the system and corrects all loads directly from the AC line. The power part of the filter is based on progressive IGBT’s, high speed voltage and current sensors and works as soft switched converter. This conception brings the savings of electrical energy and much better EMC properties in comparison with common kinds of parallel active filters. The control methods of the active power filter are described. The control methods have been implemented to DSP control systems and experimentally proved. Experimental results, which are showing the dynamic properties of active power filter, are presented.

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Keywords: Active Power Filter, Soft Switching, Resonant DC Link, Resonant Converter, DSP System.



go to top   Analysis of H-bridge Current Source Parallel Resonant Inverter for Induction Heating
         by H. Javadi, B. Majidi, A. Shoulaie, J. Milimonfared

           Vol. 5. n. 6, pp. 2527-2534


Abstract - This paper gives the theory and experimental results for a current-source parallel-resonant inverter employed for induction heating. The analysis is performed in the frequency domain using Fourier series techniques to predict output power, efficiency, dc-to-ac voltage transfer function, and component voltage and current stresses. The inverter consists of four switches, a large choke inductor, and a parallel-resonant circuit. Each switch consists of a MOSFET in series with a fast diode. An inverter was designed and constructed. The dc input voltage was 70 V and the output voltage was a sine wave with a peak value of 100 V at an operating frequency of 83 kHz. The output power at full load was 400 W.

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Keywords: : Induction Heating, Parallel Resonant, Current Source Inverter.



go to top   Photovoltaic Maximum Power Point Tracking Controller Using A New High Performance Boost Converter
         by Subiyanto, Azah Mohamed, MA Hannan

           Vol. 5. n. 6, pp. 2535-2545


Abstract - This paper presents a new high performance boost converter for maximum power point tracking (MPPT) of photovoltaic (PV) systems. The proposed boost converter uses a coupled inductor and an active snubber to minimize losses in the switching and improve efficiency of the converter. For tracking the maximum power point of a PV array, the close loop fuzzy logic and proportional integral derivative (PID) control based MPPT controller has been developed. The performance of the proposed boost converter has been verified using the Orcad PSpice software whereas the MPPT controller is modeled in the Matlab Simulink program. The MPPT controller hardware is implemented in the dSPACE DS1104 platform. The performance of the boost converter and the fuzzy-PID based MPPT controller is then evaluated through simulation and experiment.

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Keywords: Photovoltaic System, Maximum Power Point Tracking, Boost Converter, Fuzzy Controller.



go to top   LLC Series Resonant High-Frequency Sinusoidal Power Supplier
         by Liang-Rui Chen, Hai-Wen Chang, Wen-Ren Yang

           Vol. 5. n. 6, pp. 2546-2552


Abstract - This paper presents an LLC series resonant high-frequency sinusoidal power supplier for contactless power transmission system utilizing the magnetizing inductance and the leakage inductance of contactless coupled transformer. The design of system’s parameters is under 2mm air gap of contactless coupled transformer and utilizes microchip dsPIC30F4011 to track resonance tank voltage and current phase in order to maintain operation of circuit resonant frequency to ensure that circuit can provide maximum power output for various loads. Finally, a 1kW prototype is designed and implemented to access the performance of the proposed LLC series resonant high-frequency sinusoidal power supplier. The proposed circuit also compares with the traditional frequency fixed high-frequency sinusoidal power supplier. The experimental result shows that the proposed circuit can provide maximum power output for various loads and the efficiency is about 95%.

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Keywords: LLC Series Resonant, Contactless Power Transmission.



go to top   Implementation of a Soft-Switching Converter with Voltage Doubler Rectifier
         by Bor-Ren Lin, Chun-Chao Yang

           Vol. 5. n. 6, pp. 2553-2561


Abstract - This paper presents a resonant converter with output voltage doubler to achieve zero voltage switching (ZVS) feature for all power switching, zero current switching (ZCS) feature for rectifier diodes, less transformer secondary winding and voltage stress on rectifier diodes compared with center-tapped rectifier topology. For high power applications, the primary sides of two transformers are connected in parallel to reduce the current stress on primary windings. The secondary windings of two transformers are connected in series to charge relative output capacitors. Since the adopted output voltage doubler topology in the secondary side, only one secondary winding per transformer is needed. The transformer secondary winding can be reduced and the peak voltage of rectifier diode is clamped to output voltage instead of two times of output voltage in the center-tapped rectifier topology. Thus low voltage stress schottky diodes can be adopted in the circuit. The principle of operation, steady state analysis and design example of the proposed converter are provided and discussed in detail. The proposed converter is suitable for high efficiency applications such as all-in-one power supply, LCD-TV power unit, and PDP-TV power unit. The laboratory experiments with a 450W (24V/19A) prototype are provided to verify the effectiveness of the proposed converter.

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Keywords: ZVS, ZCS, Soft-Switching, Dc Converter.



go to top   New Hybrid Multilevel Inverter fed Induction Motor Drive-A Diagnostic Study
         by K.Ramani, Dr.A.Krishnan

           Vol. 5. n. 6, pp. 2562-2569


Abstract - This paper elucidates the comparative study of multilevel inverter topologies fed induction motor drive, which extensively increase the level number of output waveforms and thereby dramatically reducing the lower order harmonics and total harmonics distortion. However, the stage with higher DC link voltage has lower switching frequency and thereby, reduces the switching losses. In conventional methods, need of converters to supply the cells of reversible multi level inverters increases the cost and losses. The Hybrid Multi level inverter and New Hybrid Multi level inverter are compared with same number of switches with different value of dc sources. Based on the comparison of the topologies, the new hybrid H bridge multilevel inverter gives twenty seven level outputs resulting in more advantages. The key attention has been on the excellence of output waveform and the result obtained with the developed experimental setup.

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Keywords: AC Drive, Multilevel Inverter, Total Harmonic Distortion, Pulse Width Modulation.



go to top   Topology Exchange Between KY Converter and its Derivative based on Duty Cycle
         by K. I. Hwu, Y. T. Yau

           Vol. 5. n. 6, pp. 2570-2577


Abstract - In this paper, topology exchange between the KY converter and its derivative is presented so as to tackle the wide input voltage range and hence to increase system control reliability. Since the KY converter, named 1-plus-D converter, is a non-isolated voltage-boosting converter with buck-type behavior, its derivative, named 1-plus-2D converter, also possesses fast transient responses. And hence, the proposed topology exchange control strategy can make each other transferred smoothly. Some experimental results are provided to demonstrate the effectiveness of the proposed control scheme.

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Keywords: KY Converter, 1-Plus-2D Converter, Topology Exchange, Duty Cycle.



go to top   Predictive Current Control of Three-phase PWM Rectifiers using Virtual Voltage Vectors
         by Xingwu Yang, Jianguo Jiang

           Vol. 5. n. 6, pp. 2578-2585


Abstract - This paper presents a novel predictive current control method for three-phase PWM rectifier using virtual voltage vectors. The method uses the discrete-time model of the system to calculate the desired value of the converter voltage, and then select an appropriate voltage vector among all possible vectors to force the future current to be equal to its reference. In order to improve system performance without changing main circuit topology, virtual voltage vector synthesized by time-weighted averaging of basic vectors is introduced in this paper. The combination of virtual voltage vectors and basic vectors can make an optimum space vector for PWM rectifier, and as a result, it could bring ripple reduction in system current. Both simulation and experimental results are shown to verify the performance of the proposed control method.

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Keywords: Predictive Current Control, PWM Rectifier, Virtual Voltage Vector.



go to top   Analysis and Implementation of a Double Buck-Boost Converter with Power Factor Correction

         by Bor-Ren Lin, Huann-Keng Chiang, Ruei-Song Wu

           Vol. 5. n. 6, pp. 2586-2592


Abstract - This paper presents an AC/DC converter with discontinuous conduction mode (DCM) to achieve power factor correction, low total harmonic distortion of line current, reactive power compensation and load voltage regulation. Double buck-boost topology with only one MOSFET is adopted to reduce the DC bus voltage stress and achieve a high voltage step-up/down feature between the output and input sides. Thus low voltage stress of power switch can be used in the adopted converter. Since the buck-boost converter is operated in DCM mode, the input line current is automatically following the utility voltage and the line current is a sinusoidal waveform and in phase with AC mains. Compared to a conventional buck-boost converter, the proposed converter has wide duty ratio such that the lower or higher output voltage can be achieved. Finally, experimental results based on a 100W prototype are provided to verify the effectiveness of the proposed converter.

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Keywords: Double Buck-Boost, High Conversion Ratio, Power Factor Correction.



go to top   Improved MWFA for Computation of Salient Pole Machine Inductances

         by Hamidreza Akbari, Jafar Milimonfared, Homayoun Meshgin-kelk

           Vol. 5. n. 6, pp. 2593-2600


Abstract - All available techniques based on modified winding function approach, approximate the mean radius of the air-gap and simplify the geometrical model of salient pole machines. This approximation is applied in geometrical evaluation of this function and determining the inductances of salient pole machines. In this paper an improved MWFA is applied to calculate inductances of a salient pole synchronous machine under different eccentricity conditions. The improvement of the method is verified with FE analysis. Inductances with the improved MWFA are compared to those obtained from MWFA and it is shown that the results with the improved method are closer to those obtained from finite element computations. Effects of stator and rotor slots and several rotor asymmetries on inductances in these conditions are shown.

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Keywords: Salient Pole Machine, Inductance Computation, MWFA.



go to top   Study of Asynchronous Motors with Asymmetrical Rotor Slots under FEM Steady-State Analysis
         by Konstantinos N. Gyftakis, Joya Kappatou, Athanasios N. Safacas
           Vol. 5. n. 6, pp. 2601-2609


Abstract - In this work, models combining NEMA’s classes A and D slot geometry are created, with the use of a library of parameterized Squirrel Cage Induction Machine models. The models were analyzed using AC non-linear FEM analysis. The influences of the different analogy of class A versus class D slots in the asynchronous cage motor, on the distribution of the magnetic field, the torque as well as the stator and rotor currents are investigated. Furthermore, the electromagnetic behaviour of the class D motor, with iron closed rotor slots and with closed stator slots with semi-magnetic wedges is investigated. Finally, the efficiency of the model, with analogy of class A to D rotor slots, 1:1 was optimized, by closing the stator slots with semi-magnetic wedges of magnetic permeability equal to 5.

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Keywords: Finite Element Method, Induction Machine, NEMA’s Classes, Slot Geometry, Wedges.



go to top   Adaptive Compensation of VSI Non-Idealities to Improve Sensorless Control of PMSM in Low Speed
         by A.Amiri, M.Mohamadian, M.Dehghan, A.Sadeghilarijani
           Vol. 5. n. 6, pp. 2610-2622


Abstract - This paper proposes an adaptive compensation strategy for voltage source inverter (VSI) non-idealities to improve sensorless vector control of PMSM in low speed. An adaptive observer, which combined with HF signal injection method in startup and very low speed, is employed for position estimation. VSI non-ideality and DC bus voltage disturbances affect position estimation method and control system performances, especially in low speed operation. In previous research, switches non-ideality compensation, based on dead time compensation voltage (DTCV) and dead time compensation time (DTCT) method employed to compensate a part of non-ideal behavior of PWM VSIs.
In this paper, DC bus voltage disturbances compensation and zero current clamping compensation are also included and a simple lookup table based method for online identification of DTCT is introduced. Effectiveness of proposed method on improvement of low speed operation in comparison with uncompensated system and other compensation methods are investigated via simulation and experimental results. Results show significant improvement in transient and steady state responses of drive system.

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Keywords: Adaptive VSI Non-Idealities Compensation, Combined Position Observer, Dead Time Compensation, DC Bus Disturbances Compensation.



go to top   Finite Element Analysis of Axial, Radial and Halbach Permanent Magnet Linear Generators
         by Wijono, H Arof, WNLW Mahadi, SM Said

           Vol. 5. n. 6, pp. 2623-2629


Abstract - This paper presents a finite element analysis of permanent magnet linear generators. The machines can utilize axially magnetized permanent magnets (AMPM) only, radially magnetized permanent magnets (RMPM) only or a combination of both (Halbach) as the field sources. The study includes the analysis of the magnetic flux, flux linkage, induced voltage, cogging force and core-loss in the machines. The results provide comparative performances of tubular linear generators utilizing AMPM, RMPM and Halbach permanent magnet configuration along with the advantages and drawbacks of each type. It is found that the Halbach configuration provides a compromise between the axial and radial configuration, which results in a moderate induced voltage and overcomes the problem of high cogging force experienced in the axial configuration.

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Keywords: Axial Permanent Magnet, Radial Permanent Magne,T Halbach Configuration, Linear Generator.


go to top   Speed Tracking Control of PMSM using Backstepping Controller - Simulation and Experimentation
         by K. Kendouci, B. Mazari, M. R. Benhadria

           Vol. 5. n. 6, pp. 2630-2636


Abstract - In this paper, a backstepping design technique to the speed control of permanent magnet synchronous motors (PMSM) is developed. Using backstepping method, both feedback laws and Lyapunov based designs are applied in the controller design. The proposed control scheme is not only to stabilize the PMSM system, but also to driv the speed tracking error to converge to zero asymptotically. Furthermore some experimental results are given to illustrate the excellent performance of the nonlinear backstepping control design and to show the robustness of the estimation control drive system.

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Keywords: Permanent magnet synchronous motor, backstepping design, nonlinear control, Parameters uncertainties.


go to top   Influencing Factors Investigation of Polarization and Depolarization Current Measurements on Assessment Aging Condition of Power Transformer
         by Junhao Li, Yanming Li

          Vol. 5. n. 6, pp. 2637-2643


Abstract - For reliable operation of power transformer, the aging condition of the insulation system is essential. The polarization and depolarization current (PDC) analysis is a non-destructive dielectric testing method to evaluate the aging condition of insulation materials in power transformer. The main influencing factors of PDC measurement have been studied after the basic theory of PDC is described in this paper. The study results show the insulation structure, moisture level and aging state have great influence on the test results of PDC method. Analyses and interpretation of the field test data are also presented in this paper.

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Keywords: Transformer, Oil-Paper Insulation, Aging, Dielectric Response, Polarization Current, Depolarization Current.



go to top   Controlling Chaotic Ferroresonance oscillations in Autotransformers Including Linear and Nonlinear Core Losses Effect

         by Hamid Radmanesh

           Vol. 5. n. 6, pp. 2644-2652


Abstract - This paper investigates the effect of linear and nonlinear core losses on the onset of chaotic ferroresonance and duration of transient chaos in an autotransformer and control of these phenomena by considering nonlinear core losses effect. The magnetization characteristic of the transformer is modeled by a single-value two-term polynomial. The nonlinear core losses are modeled by a third order power series in voltage with nonlinearities in core losses included, four effects are clear: (i) onset of chaos at larger values of open phase voltage, (ii) shorter duration of transient chaos, and (iii) less susceptibility to ‘jump’ phenomena and finally, (iv) great controlling effect of nonlinear core losses on the chaotic ferroresonance oscillation in autotransformer. It is shown that nonlinear core losses can cause ferroresonance drop out. For confirmation these aspects, nonlinear study is done by using MATLAB/Simulink and nonlinear dynamical tools such as bifurcation and phase plan diagram are used to shown the simulation results.

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Keywords: Nonlinear Core Losses, Chaos Control, Bifurcation Diagram, Ferroresonance Oscillation, Autotransformers.



go to top   Bidimensional Modelling Non-Equilibrium Fluid Model of Glow Discharge at Low Pressure
         by B. Kraloua, A. Hennad

           Vol. 5. n. 6, pp. 2653-2656


Abstract - In this work, we present new numerical technique for bidimensional resolution fluid model formed by first three Boltzmann's moments. The main purpose is calculated electric and physical properties in non-equilibrium electric discharge at low pressure maintained by secondary electron emission coefficient. The transport equations and Poisson's equation formed self-consistent model. This equations system is written by cylindrical coordinates while respecting the geometric shape of plasma reactor. Our transport equations system is discretized using the finite volumes approach and resolved by N-BEE explicit scheme coupling at time splitting method. This bidimensional programming structures reduce considerably the calculation time. The test validity our 2D code is carried out by comparing our results with the literature.

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Keywords: 2D Fluid Model, Glow Discharge, N-BEE Scheme, Time Splitting Method.



go to top   Design of a Vehicle Negative Ions Generating Circuit
         by Liang-Rui Chen, Chia-Hsuan Wu, Chung-Ming Yang, Neng-Yi Chu

           Vol. 5. n. 6, pp. 2657-2663


Abstract - Negative ions technology has been widely used to deal with air pollution problems in recent years. In this paper, a negative ions generating circuit is proposed for dealing with the exhaust gas in vehicle, which circuit generates high electric field to ionize the air. The number of active particles increases in the air, which react with the exhaust gas and make the air clean. The circuit analysis and simulation are presented in this paper, and a 6.44kV prototype is also realized to verify the performance.

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Keywords: Negative Ions, Vechile.



go to top   Impacts of TCSC on Distance Relay Performance
         by H. Shateri, A. Kazemi, S. Jamali

           Vol. 5. n. 6, pp. 2664-2672


Abstract - This paper presents the measured impedance at the relaying point in the presence of Thyristor Controlled Series Compensator (TCSC), one of series connected Flexible Alternating Current Transmission System (FACTS) devices, in the case of symmetrical (three phase) and asymmetrical (single phase to ground and phase to phase) faults. The presence of TCSC on a transmission line has a great influence on the measured impedance at the relaying point. The measured impedance itself depends on the power system structural conditions, pre-fault loading, and especially the fault resistance. In the presence of TCSC, its compensation degree as well as its installation location affects the measured impedance and consequently the locus of the apparent impedance.

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Keywords: Distance Protection, FACTS Devices, Locus of the Apparent Impedance, Measured Impedance, TCSC.



go to top   Pattern Recognition for Partial Discharge Based on Tri-Training Semi-Supervised Learning
         by Linpeng Yao, Hui Wang, Yong Qian, Chengjun Huang, Xiuchen Jiang

           Vol. 5. n. 6, pp. 2673-2678


Abstract - Pattern recognition of partial discharge is considered as a useful tool for insulation fault detection on high voltage electrical apparatus. A pattern recognition method for partial discharge on XLPE Cable based on Tri-training semi-supervised learning is presented. Three C4.5 classifiers are generated from the original labeled sample set, with statistical features such as skewness, kurtosis, cross-correlation factor and degree of asymmetry extracted from phase resolved data. These classifiers are then refined with unlabeled samples in the process of Tri-training. Compared with C4.5 algorithm, Tri-training algorithm could effectively improve detecting ability by exploiting a large amount of unlabeled samples. Experimental results on example set of artificial defects prove high performance of the proposed algorithm.

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Keywords: XLPE Cable, Partial Discharge (PD), Semi-Supervised Learning (SSL), Tri-training, Pattern Recognition, C4.5, Classification.



go to top   Interruption of Inductive Currents Using an Ideal Vacuum Circuit Breaker
         by J. A. Brandão Faria

           Vol. 5. n. 6, pp. 2679-2685


Abstract - Vacuum circuit breakers are modernly employed for the interruption of medium and high voltage circuitry. These circuit breakers are not ideal devices because of two main problems; on the one hand the degree of vacuum is not perfect and, on the other hand, the metal plasma created at the metallic contacts surface ignites arcing. Here, the theoretical operation of an ideal breaker, where the above referred problems would not exist, is analyzed by taking into account the dynamical behavior of the contacts separation process. Simulation results concerning the mechanical and electrical transient phenomena, due to the sudden interruption of an inductive circuit fed by a DC voltage as small as 1 kV, are presented. Results show that such an ideal device would not work due to the overwhelming electric force exerted between contacts, preventing the latter to get separated.

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Keywords: Electromagnetic Forces. Transient Phenomena. Vacuum Circuit Breakers.



go to top   Investigation of Surface Modifications in ADSS Cables Due to Dry Band Arcing
         by İbrahim Güneş, Aysel Ersoy, Mukden Uğur

           Vol. 5. n. 6, pp. 2686-2691


Abstract - In the present work dry band arcing phenomena on ADSS (All-dielectric-self-supporting) cables has been studied using chemical analysis. To determine the degradation level and behavior after IEEE 1222 Electrical surface degradation test, several test methods, such as Oxidative Induction time (OIT)/ Differential Scanning Calorimetry (DSC), Thermogravametric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) analysis were used. The results of these physico- chemical analysis reveal that, dry band arcing IEEE 1222 test standard is a surface degradation test method which only effect the sample surface get carbonized.

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Keywords: ADSS, Aging, Fiber-optic cable, Physico-chemical Tests, Transmission Lines.



go to top   Multiple Target Parameter Estimation in Multi-Frequency Array Radar
         by M. A. Sebt, M. M. Nayebi, H. R. Amindavar

           Vol. 5. n. 6, pp. 2692-2709


Abstract - Since space diversity and frequency diversity are both efficient techniques in the radar applications, we propose in this paper a method for simultaneous usage of both techniques. On this basis, multi-frequency array radar in which all frequencies are used simultaneously to increase the number of targets that can be uniquely identified, is introduced and analyzed. First, the signal model for such a system is derived and then, it is shown how the use of multi-frequency signal can noticeably improve the parameter identifiability. Specifically, we show the maximum number of targets that can be uniquely identified by the multi-frequency array radar is L times that of its single-frequency array counterpart, where L is the number of frequencies. Finally, the Maximum Likelihood estimator and Cramer-Rao lower bound are derived for the fluctuating and constant reflection coefficient models. By extensive simulations, it is demonstrated that the use of the fluctuating reflection coefficient model estimator is necessary since the constant reflection coefficient model estimator may lead to high estimation errors. Also, it is shown that for a fixed total transmitted power, the parameter estimation error decreases as the number of frequencies increases.

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Keywords: Array Radar, Multi-Frequency, Parameter Estimation.



go to top   A Compact Dual-Band Printed Dipole Antenna Loaded with CLL-Based Metamaterials
         by A. Jafargholi, M. Kamyab, M. Rafaei Booket, M. Veysi

           Vol. 5. n. 6, pp. 2710-2714


Abstract - This paper examines reactive loading technique to achieve dual band operation and further size reduction for double-sided printed dipole antennas. The reactive loads are realized by two balanced capacitively loaded loops (CLLs) placed close to the edge of the printed dipole antenna. It is demonstrated that the proposed loaded dipole antenna is a dual band radiator with sufficient gain suitable for applications such as mobile communication and Industrial, Scientific and Medical (ISM) system. Finally, the CLL element is integrated with chip capacitor to provide a larger capacitance which in turn allows the resulting CLL element to resonate at a lower frequency. Prototypes of double resonant dipole antennas are designed and tested. A good agreement is achieved between measurement and simulation.

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Keywords: Capacitively Loaded Loop (CLL), Double-Sided Printed Dipole Antenna.



go to top   Estimation of Pseudo-Range DGPS Corrections Using Neural Networks Trained by Evolutionary Algorithms
         by M. R. Mosavi

           Vol. 5. n. 6, pp. 2715-2721


Abstract - GPS measurements can be degraded by several type of error like unmodelled ionosphere and troposphere delays, satellite and receiver clocks inaccuracies, receiver noise, dilution of precision and multi-path effects, and also the U.S. military’s intentionally such as Selective Availability (SA). These errors degrade the accuracy of GPS position. DGPS provides users with corrections to remove the correlated bias terms between receivers. The DGPS has the problem of slow updates. Any interruption of the DGPS service causes a loss of navigation guidance. This paper proposes the prediction of DGPS corrections using Neural Networks (NNs) trained by evolutionary algorithms such as the genetic algorithm and the Particle Swarm Optimization (PSO). A low cost commercial and single-frequency GPS receiver is utilized to demonstrate the DGPS positioning. The experimental results show the feasibility and effectiveness of the proposed methods. The results are analyzed and compared with NNs trained by the back propagation algorithm. The NNs trained by PSO gives better accuracy in estimating the DGPS corrections; so that the total RMS error reduces to less than 1.32 metre with SA on and 0.46 metre with SA off.

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Keywords: Improvement, Differential GPS, Neural Network, Back Propagation, Genetic Algorithm, Particle Swarm Optimization.



go to top   Application of the Charge Simulation Method to the Calculation of the Characteristic Parameters of Printed Transmission Lines
         by Alenka Milovanovic, Branko Koprivica, Miroslav Bjekic

           Vol. 5. n. 6, pp. 2722-2726


Abstract - In this paper the analysis of TEM propagation of electromagnetic waves in microstrip lines and striplines have been presented. Most used techniques for this analysis, their advantages and disadvantages, have been discussed. The aim of this paper is to present an application of the Charge Simulation Method (CSM) to the calculation of some characteristic parameters of coupled microstrip transmission lines and striplines. The capacitance per unit length, characteristic impedance and effective dielectric constant have been determined. For a comparison of the results obtained with the Charge Simulation Method, approximate analytical expressions and the software package COMSOL Multiphysics have been employed. The results have been found to be in very good agreement.

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Keywords: Charge Simulation Method, Characteristic Parameters, Microstrip Line, Stripline, COMSOL Multiphysics.




International Review of Electrical Engineering - Papers- Part B



go to top   Improvement of Power System Transient Stability using TCBR and TCSC, a Comparative Study
         by Sabir Messalti, Saad Belkhiat, Shahrokh Saadate, Damien Flieller

           Vol. 5. n. 6, pp. 2727-2736


Abstract - This paper shows the modeling and the effectiveness of two FACTS devices for transient stability improvement of power systems: The ability of flexible adjustment of Thyristor Control Breaking Resistor (TCBR) and Thyristor Controlled Series Capacitor (TCSC) can presumably increase the power systems stability. Their effect has been investigated separately and can be combined together to have a higher benefits when the power system is equipped with a compensator. Critical Clearing Time (CCT) has been used as an index for evaluated transient stability. The transient stability is assessed by the criterion of relative rotor angles, using Runge-Kutta method. The effectiveness of the proposed method is tested on the WSCC3 nine-bus system applied to the case of three-phase short circuit fault in one transmission line. The simulation results and their comparison are presented in this paper.

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Keywords: Critical Clearing Time CCT, Transient Stability, Runge-Kutta Method, TCBR, TCSC.



go to top   Flexible Distributed Generation Planning in Distribution Systems Considering the Plans Assessment
         by A. Moeini, H. Yassami, M. Banejad, M. Owladi, A. Bagheri, M. Ghadiri

           Vol. 5. n. 6, pp. 2737-2744


Abstract - Numerous methods for Distributed Generation (DG) planning in electrical power systems have been presented over the years. This paper proposes a new technique for DG planning in distribution networks using Strength Pareto Evolutionary Algorithm (SPEA). This multi-objective optimization algorithm is used to deal with the optimization objectives separately. A 28-node distribution system is used to present the capabilities of the mentioned approach. Four common types of DGs are nominated to be installed in the test system. Minimization of the total power losses and the marginal cost of the DGs are two major objectives considered in the paper. According to reverse linkage of the objectives, the SPEA generates a Pareto Front (PF) that contains some optimal DG planning with different features. The choice of the optimum solution depends on the planner's interest. Finally, to have a comprehensive view, economical analysis is done.

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Keywords: Cost Effectiveness Index, Distributed Generation, Flexible Schemes, Marginal Rate of Substitution, Multi-Objective Optimization, Pareto Front.



go to top   Damping of Power System Oscillations Using Genetic Algorithm and Particle Swarm Optimization
         by Mahdiyeh Eslami, Hussein Shareef, Azah Mohamed, Mohammad Khajehzadeh

          Vol. 5. n. 6, pp. 2745-2753


Abstract - In this study, the application and performance comparison of particle swarm optimization (PSO) and Genetic algorithms (GA) optimization methods, for power system stabilizer (PSS) design is presented. Recently, GA and PSO methods have attracted considerable attention among different modern heuristic optimization methods. The GA has been popular in academia and the industry, mostly because of its intuitiveness, ease of implementation, and the capability to efficiently solve highly non-linear, mixed integer optimization problems that are typical of complex engineering systems. PSO method is a relatively new heuristic search method whose mechanics are inspired by the swarming or collaborative behavior of biological populations. Since the two approaches are supposed to find a solution to a given objective function but utilize different strategies and computational effort, it is appropriate to compare their performance. The design objective is to increase the power system stability. The design problem of the PSS parameters is formulated as an optimization problem and both PSO and GA optimization methods are used to search for optimal PSS parameters. The two-area multi-machine power system, under a wide range of system configurations and operation conditions is investigated to illustrate the performance of the both PSO and GA. The performance of both optimization methods is compared with the conventional power system stabilizer (CPSS) in terms of parameter accuracy and computational time. The eigenvalue analysis and non-linear simulation results are presented and compared to show the effectiveness of both the methods in optimal tuning of PSS, to enhance power system stability.

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


Keywords: Genetic Algorithm, Multi-objective Optimization, Design PSS, Particle Swarm Optimization.



go to top   Decentralized Nonlinear Adaptive Control and Stability Analysis of Multimachine Power System
         by M. Ouassaid, M. Maaroufi, M. Cherkaoui

          Vol. 5. n. 6, pp. 2754-2763


Abstract - In this paper, a solution to the problem of transient stabilization of multimachine power systems is proposed in a multivariable and nonlinear framework. The design method is based on a new power system model. The main characteristic of this model is that interactions between generators and changes in operating conditions are represented by time-varying parameters. Nonlinear decentralized controllers are designed explicitly for the excitation model and turbine governor model. Deviations of terminal voltage and angular frequency are selected as the feedback variables, which make it possible to achieve satisfactory voltage regulation as well as damping capability. The methodology adopted is based on adaptive backstepping design strategy. The proposed stabilizing feedback laws for the power system are shown to be globally asymptotically stable in the context of Lyapunov theory. The tracking errors are shown to be globally uniformly bounded. The proposed technique is illustrated with a two-area benchmark power system. Numerical simulation results show that the proposed control approach is effectual in improving voltage and rotor speed regulation and suppressing all modes of oscillation. The decentralized proposed controller requires only local measurement, which owns highly desirable advantages in cost, reliability and can be easily implemented.

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Keywords: Multimachine Power System, Backstepping Design, Transient Stability, Decentralized Control.



go to top   Advanced Control Techniques for Grid-connected Distributed Generators in Microgrids
         by Tsao-Tsung Ma

           Vol. 5. n. 6, pp. 2764-2772


Abstract - This paper presents a new integrated multifunctional power flow and power quality control scheme, which is based on three-phase power converters and the decoupled d-q axis power flow control concepts, for the grid-connected distributed generators used in microgrids. In the proposed control scheme, the modular design concepts and advanced control algorithms are used to design the required controllers for the proposed power interface in performing various control functions of a DG system operating in microgrids, i.e. fast power flow regulation, real-time voltage control, reactive power and harmonic current compensations. The effectiveness of the proposed control scheme is verified with comprehensive simulation and experimental studies. Typical results are presented with discussions.

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Keywords: Power Converter, Microgrids, Power System Control, Distributed Generation Systems (DG).



go to top   Optimal Power Flow with Unified Power Flow Controller Using Artificial Bee Colony Algorithm
         by Arjang Yousefi-Talouki, S.Asghar Gholamian, Mehdi Hosseini, Sepideh Valiollahi

           Vol. 5. n. 6, pp. 2773-2778


Abstract - This paper presents a solution of optimal power flow incorporating unified power flow controller (UPFC), as a powerful and versatile FACTS devices, using artificial bee colony (ABC). The power injection model of FACTS devices is used for modeling UPFC in the power system. The main goal of this paper is to minimize generation fuel cost while satisfying system’s constraints such as generation capacity limits, power balance, line flow limits and bus voltage limits. The proposed ABC method is demonstrated and compared with particle swarm optimization (PSO) approach on the standard IEEE 30-bus system. The results show that the proposed ABC method can obtain higher quality solution than PSO algorithm.

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Keywords: OPF, UPFC, ABC Algorithm, PSO.



go to top   Optimal State Feedback Damping Controller for the STATCOM Using Particle Swarm Optimization
         by Amin Safari, Rouzbeh Jahani, Mehrdad Fazli, Hossein Shayeghi, Heidar Ali Shayanfar

           Vol. 5. n. 6, pp. 2779-2785


Abstract - This paper presents a new method for the design of state feedback damping controller for static synchronous compensator (STATCOM) using particle swarm optimization (PSO) algorithm. The selection process of the state feedback gains for the STATCOM is converted to an optimization problem with the objective function based on eigenvalue which is solved by PSO algorithm which has a strong ability to search and find the most optimized and optimistic results. Only local state variables are selected as the input signals of each controller in the design process. Therefore, the structure of designed STATCOM is very simple and easy to perform. The effectiveness of the proposed controller is illustrated through eigenvalue analysis and nonlinear time-domain simulation studies. The performance of the proposed method is compared to that of GA (Genetic Algorithm) based on designed state feedback controller for different operating conditions and various disturbances. The results analysis shows that the proposed PSO algorithm based on designed damping controller for STATCOM, is very capable to damp power system low-frequency oscillations and improves the dynamic stability of the power system, significantly.

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Keywords: STATCOM, State Feedback Damping Controller, PSO, Low Frequency Oscillations.



go to top   A New Advanced Heuristic Method for Optimal Placement of Unified Power Flow Controllers in Electrical Power Systems
         by Rouzbeh Jahani, Hadi Chahkandi Nejad, Alireza Shafighi Malekshah, Heidar Ali Shayanfar

          Vol. 5. n. 6, pp. 2786-2794


Abstract - In this paper a new method called “Modified Shuffled Frog Leaping Algorithm” is used to obtain optimal location and number of FACTS devices in a power system. Among the FACTS devices, Unified Power Flow Controller (UPFC) enables the active and reactive power flow and bus voltages to be controlled simultaneously due to its great flexibility. Decoupled model of UPFC is applied to maximize the system loadability considering transmission line capacity limits and specified voltage level. The Shuffled Frog Leaping Algorithm (SFLA) is a new meta heuristic algorithm with a global search capability which uses efficient mathematical function. The objective is to maximize the transmission capability and loadability subject to the transmission line capacity limits and specified bus voltage levels. Location of the UPFCs and their parameters will be optimized simultaneously by using the proposed method. The proposed method (SFLA) is tested on IEEE 14-bus , 30-bus and IEEE 118-bus systems. The simulated results show that the steady state performance of the power system can be improved effectively due to the optimal location and parameters of the UPFC.

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Keywords: Unified Power Flow Controller (UPFC); Maximize the Loadability of Transmission Lines; Modified Shuffled Frog Leaping Algorithm (MSFLA).



go to top   Damping of Low Frequency Oscillation in AC/DC Interconnected Power System Using LQG/LTR Controller Approach
         by K. Rahmani, Mehdi S. Naderi, G. B. Gharehpetian, Mohammad S. Naderi, M. Karrari

           Vol. 5. n. 6, pp. 2795-2802


Abstract - This paper presents a Linear Quadratic Gaussian with Loop Transfer Recovery (LQG/LTR) controller design method to enhance power system oscillation damping in an AC/DC power system. The LQG/LTR controller has been used to improve the performance and to meet the stability robustness conditions in the frequency domain. The simulation results show that the designed controller damps all torsional modes. It is also shown that the closed loop system with proposed stabilizer is robust in the presence of noise and different fault conditions.

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Keywords:  LQG/LTR Control, AC/DC Power System, Dynamic Stability, DC Modulation.



go to top   COA Based Coordinated Design of FACTS and PSS Output Feedback Controllers
         by Amin Safari, Rouzbeh Jahani, Mehrdad Hajinasiri, Amir Hossein Araskalaei, Heidar Ali Shayanfar

           Vol. 5. n. 6, pp. 2803-2808


Abstract - This paper presents a systematic procedure for modeling and simulation of a power system installed with a power system stabilizer (PSS) and a flexible ac transmission system (FACTS)-based out put feedback damping controller. The coordinated design problem of PSS and FACTS with output feedback controllers over a wide range of loading conditions is formulated as an optimization problem which is solved by a Chaotic Optimization Algorithm (COA) based on Lozi map. Only local and available state variables are adopted as the input signals of each output feedback controller for the coordinated tune. The effectiveness of the proposed method is demonstrated through nonlinear time-domain simulation and some performance indices studies under of over a wide range of loading conditions. The results of these studies show that the COA based output feedback controllers for coordinated design has an excellent capability in damping power system oscillations.

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Keywords: Chaotic Optimization Algorithm (COA); Power System Stabilizer (PSS); Flexible Ac Transmission System (FACTS); Feedback Controller.



go to top   Application of LQG\LTR Method in Load Frequency Control
         by M. Ghazal, J. Poshtan, M. Poshtan

           Vol. 5. n. 6, pp. 2809-2818


Abstract - A new robust controller for power systems has been proposed in this paper. The new strategy is based on applying the LQG\LTR method to Load Frequency Control (LFC) of power systems. Power systems are growing more extensive and complex recently so the load frequency control has become more significant to achieve reliable control. Because proportional integral controllers are incapable of obtaining good dynamic performance for wide range of operation conditions and various load change scenarios in multi-area power systems, in this paper the LQG\LTR method is proposed. This method is a systematic design method and based on shaping and recovering open loop singular values. Because the complexities of computation are realized, the inputs and outputs are redefined. Although the proposed method can be used for n-area power systems, it is tested on two-area power system under various operating conditions and it is compared with a QFT controller. In order to show the practical limitation in the rate of changes in the generating power of generation companies, generation rate constrains are considered for each area. The simulation results show that the proposed controller design method achieves a good performance even in the presence of Generation Rate Constraints (GRC), Governor Dead Band (GDB), and parameter variations.

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


Keywords: Load Frequency Control, Parameter Uncertainty, LQG\LTR Design, Kalman Filter, Robust Control.



go to top   Analysis and Assessment of FACTS-Based Stabilizers for Damping Power System Oscillations using Genetic Algorithms
         by J. Barati, S. S. Mortazavi, A. Saidian

           Vol. 5. n. 6, pp. 2819-2827


Abstract - This paper investigates and compares the enhancement of damping the power system oscillations via coordinated design of the power system stabilizer (PSS), Thyristor Controlled Series Compensation (TCSC) and Static Var Compensator (SVC) controllers. The design problem of FACTS-based stabilizers is formulated as an optimization problem. The proposed approach employs genetic algorithm (GA) for stabilizer parameters optimization. In this paper eigenvalue analysis method is used for small signal stability of single machine infinite bus (SMIB) system installed with PSS, TCSC and SVC. The proposed stabilizers are tested on a weakly connected power system with loading conditions. The eigenvalue analysis and non-linear simulation results are presented and to show and compare the effects of these FACTS-based stabilizers and reveal that TCSC-based stabilizers is much better than SVC-based stabilizers on the damping power system oscillations.

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


Keywords: PSS, FACTS Devices, Damping Controller, Genetic Algorithm, Power System Stability.



go to top   Voltage Unbalance Analysis in Power Systems Supplying Electrical Railways
         by Ivica Pavić, Tin Bobetko, Viktor Milardić

           Vol. 5. n. 6, pp. 2828-2835


Abstract - The electric railway system represents one of the largest sources of unbalances in the three-phase power system. This paper presents the modified three-phase load flow method in order to achieve greater precision in determining the voltage and current unbalances in the observed network. Traditionally, the AC traction loads are modeled in three-phase load flow program as constant two or three equivalent single-phase loads depending on traction transformer connection. The modified Newton-Raphson algorithm, presented in this paper, is based on constant phase-to-phase load modeling. Using this method it is possible to determine bus voltages and power flow in the railway traction system and power system simultaneously. A part of Croatian power system has been used as a test network to present the numerical results of the proposed method.

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Keywords: Railway Traction System, Voltage Unbalance, Three-Phase Load Flow.



go to top   Voltage Sag Compensation in Distribution System due to SLG Fault Using D-STATCOM
         by Hendri Masdi, Norman Mariun, S. M. Bashi, Azah Mohamed

           Vol. 5. n. 6, pp. 2836-2845


Abstract - This paper presents the distribution static compensator (D-STATCOM) for load compensation in an unbalanced distribution system. Simulation were carried out for both cases where, D-STATCOM was connected to the system and not, with simulation interval 0.20 sec. In order to verify the simulation results, a prototype D-STATCOM is constructed and connected in shunt load. Single Line to Ground (SLG) fault is tested on the load and the corresponding results without and with D-STATCOM are recorded then the experimental results obtained from the constructed D-STATCOM are compared with the simulation results. The aim of the D-STATCOM here is to provide voltage regulation at the load point and mitigate the voltage sag generated when the fault occurred. The D-STATCOM is intended to replace the widely used static var compensator (SVC). The compensation scheme of the D-STATCOM is derived using the symmetrical component method. In this work, the 12-pulse D-STATCOM configuration with IGBT has been designed and the graphic based models of the D-STATCOM have been developed using the PSCAD/EMTDC4.2 electromagnetic transient simulation program.

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Keywords: SLG, D-STATCOM, voltage sag compensation.



go to top   Application of Multi Objective Optimization Approach in Designing of Power System Stabilizers and power system stability Enhancement
         by M. Ahmadzadeh, S. Mortazavi, S. Mohammadzadeh, S. V. Heydari

          Vol. 5. n. 6, pp. 2846-2854


Abstract - In this paper a new multi - objective genetic approach (MOGA) based optimization method is proposed for optimal coordinated selection of power system Stabilizers (PSS) and Flexible AC Transmission Systems (FACTS) devices. FACTS devices are containing Thyristor controlled Series Compensator (TCSC), Static var compensators (SVC), Thyristor Controlled phase shifter (TCPS) based conventional lead-lag damping controller. The controller's parameters are tuned in order to shift the lightly damped and undamped modes under nominal loading condition toward a prescribed stability region. The objective function includes system stability criteria (e.g., Integral of Time Absolute Error (ITAE) and sum of the squared errors of electrical torque) considering boundaries of controller parameters (as constraints). This approach is called MOFF (multi objective fitness function). Its robustness is tested under nominal loading condition. To select effective feedback signal for the damping controller, analysis of mode observability and the theoretical analysis of a Single- Machine Infinite-Bus (SMIB) are done. This modeling is done using its modified linearized Phillips-Heffron model installed with PSS and FACTS devices. Finally the results of proposed approach is compared by other approach (genetic algorithm approach (GA) and single objective fitness function (SOFF)). Obviously, in SOFF only one stability criteria is considered.

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


Keywords: PSS, FACTS Devices, Damping Controller, Robustness, Multi – Objective Genetic Approach, Multi - Objective Function And Small Signal Stability.



go to top   Feasible Domain-Driven Genetic Operators for Distribution Systems Optimal Reconfiguration
         by A. Augugliaro, L. Dusonchet, S. Favuzza, M. G. Ippolito, E. Riva Sanseverino

           Vol. 5. n. 6, pp. 2855-2866


Abstract - In this paper, the problem of minimum losses reconfiguration in weakly meshed medium voltage (MV) distribution systems is dealt with. The presence of meshes can either be a cause of the presence of particular loads, favoured customer (FC) nodes, requiring a double supply path or of distributed generation (DG) nodes, that cannot work in islanded mode. The problem has been brought back to the more general problem of radial networks reconfiguration with the major aim of minimising power losses subject to constraints on voltage drops at load nodes and current in branches as well as on the partition of power generated among supply nodes in the network. The problem is non-linear and combinatorial considering the objective function, the constraints and the unknowns; for its solution, the authors have used a genetic algorithm. For the creation of the first generation as well as of the subsequent generations, a set of new generation and perturbation operators have been set up. They guarantee that all solutions represent a radial structure while supplying all the loads. In this way, the generation of unfeasible solutions is avoided and the verification step afterwards is no longer necessary. The applications show that such operators allow a wider exploration of the search space, while their implementation is quite easy and does not require a particular computational effort.

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Keywords: Distribution Systems, Optimal Reconfiguration, Genetic Algorithm.



go to top   Economic Evaluation of Security-Constrained Unit Commitment for System with High Penetration of Wind Power

         by L. Alinezhad, A. Sadeghi Yazdankhah, A. Zakariazadeh

           Vol. 5. n. 6, pp. 2867-2872


Abstract - Spinning reserve (SR) is one of the energy resources to compensate for unpredictable imbalances between load and generation caused by unforeseen events. For systems with high penetration of wind power it is difficult to commit the amount of power injected by generator units into the power system. This paper presents a stochastic mixed-integer linear programming model with stressing on simultaneous optimization of energy and reserve markets. The main purpose of this paper is to propose a cost efficient technique to determine sufficient amount of spinning reserve for a power system, while the expected load not served (ELNS) and the value of lost load (VOLL) for each bus in the model are included. This paper also introduce a stochastic scheduling of spinning reserve in power system with high penetration of wind power that considers the accidental disturbances such as outages of generating units and transmission lines , and errors in the forecasts of wind power production, simultaneously. The proposed approaches are performed on the two IEEE-RTS for 24 hours, and the results show significant reduction in the spinning reserve requirement and possible lower operation cost compared to the modified traditional deterministic reserve criterion.

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


Keywords: Expected Load Not Served (ELNS), Mixed-Integer Linear Programming (MILP), Spinning Reserve, Stochastic Optimization, Transmission Limits, Wind Power Generation, Unit Commitment (UC).



go to top   Optimum Placement and Sizing of DG Using Binary PSO Algorithm to Achieve the Minimum Electricity Cost for Consumers

         by J. Moshtagh, A. Jalali, K. Karimizadeh

           Vol. 5. n. 6, pp. 2873-2881


Abstract - Nowadays placement of distributed generation units (DGs) is carried out to achieve a variety of operational or planning purposes. Minimizing the network losses, improving the voltage profile, reliability and economic goals, etc are several common goals. In this area, analysis of DGs location effect on electricity nodal prices in distribution networks rarely has been considered. In this paper placement and sizing of DGs in a radial distribution network that operates under locational market pricing (LMP) rules, is carried out. Some operational and economic goals in a variety of scenarios are tested on a practical distribution network. A binary particle swarm optimization (BPSO) algorithm is used to optimizing the multi-objective optimization problem.

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Keywords: BPSO Algorithm, Distributed Generation, Locational Prices, Optimal Power Flow.



go to top   Nonlinear Control of VSC-HVDC Transmission Converter for Offshore Wind Farm

         by Wang Guoqiang, Wang Zhixin

          Vol. 5. n. 6, pp. 2882-2889


Abstract - VSC-HVDC (high voltage direct current based on voltage source converter) is of many advantages compared with traditional HVDC, such as flexible operating ways and reliability, especially in the transmission problem of offshore wind farm. But it is sensitive to AC unbalanced input voltage and instability of wind energy under traditional PI control strategy. This paper adopts dual vector current controller (DVCC) in conjunction with input-output feedback linearization method to design the system. The DVCC can control the positive and negative sequence current respectively. The linearization method makes the double current loop be linear and decoupled. To the difficulty of regulating massive PI parameters of multi-inside-loop, we substitute pole placement for PI parameters setting. Namely that it changes the problem of adjusting PI parameters to the one of pole placement. Finally, Simulation study is realized by software of Matlab/Simulink and compare with the traditional control method. The results show that the control method of this paper is effective.

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Keywords: VSC-HVDC, Nonlinear Control, Feedback Linearization, Wind Farm.



go to top   Gravitational Search Algorithm for Economic Dispatch with Valve-Point Effects
         by S. Duman, U. Güvenç, N. Yörükeren

           Vol. 5. n. 6, pp. 2890-2895


Abstract - In recent years, various heuristic optimization methods have been proposed to solve Economic Dispatch (ED) problem in power systems. This paper presents the well-known power system ED problem solution considering valve-point effect by a new optimization algorithm called as Gravitational Search Algorithm (GSA). The proposed approach has been applied to various test systems with incremental fuel cost function taking into account the valve-point effects. The results shows that performance of the proposed approach reveal the efficiently and robustness when compared results of other optimization algorithms reported in literature.

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Keywords: Gravitational Search Algorithm, Economic Dispatch, Valve-Point Effect, Optimization.



go to top   Introducing a Fuzzy Interactive Multi-Objective Approach to Optimal Location of UPFC
         by A. Lashkar Ara, J. Aghaei, M. Shabani

           Vol. 5. n. 6, pp. 2896-2906


Abstract - The coupling of performance functions due to common design variables and uncertainties in an engineering design process will result in difficulties in optimization design problems, such as poor collaboration among design objectives and poor resolution of design conflicts. To handle these problems, a fuzzy interactive multi-objective optimization model is developed based on Pareto solutions while the metric function and some additional constraints are added to ensure the collaboration among design objectives. This method is applied to find the optimal location of Unified Power Flow Controller (UPFC) to enhance power system operation. The Optimal Power Flow (OPF) formulated as a nonlinear optimization problem with both equality and inequality constraints. The proposed multi-objective functions are: minimization of total fuel cost, minimization of active power losses, maximization of system loadability and minimization of investment cost of UPFC. Numerical example is presented in order to show efficiency of proposed technique through 30-bus IEEE test system using MATLAB and Generalized Algebraic Modeling of System (GAMS) softwares.

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Keywords: Interactive Optimization, Pareto Solutions, Fuzzy Optimization, OPF, Decision Making, UPFC.



go to top   Electric Power Quality Disturbance Assessment Using Wavelet Transform Analysis
         by S. Mohammadzadeh, S.S. Mortazavi, M. Ahmadzadeh

           Vol. 5. n. 6, pp. 2907-2913


Abstract - This paper presents a method for power quality measurement and analysis in electrical power systems. Sag, swell, sag with harmonic, swell with harmonic and flicker are studied in this paper as Power quality problems. The detection and localization of the disturbances and their duration, starting time and ending time are attained by discrete wavelet transform (DWT). The standard deviation curve of wavelet of the given signal is evaluated. This paper shows that each power quality wavelet disturbance has unique deviations from the pure sinusoidal wavelet and this is adopted to provide a reliable classification of power quality type. Finally, a new technique is proposed to determine amplitude of sag and swell.

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Keywords: Power Quality, Wavelet Transform, DWT, Sag, Swell.



go to top   Multi-Objective Reactive Power Control by a Global Best Harmony Search Algorithm
         by S. M. Shariatmadar, H. Khomami Pamsari, V. Amir, A. SiahVashi

           Vol. 5. n. 6, pp. 2914-2918


Abstract - Reactive power control is a nonlinear and non-convex optimization problem which has a salient effect on the secure and economic operation of the power system. In this optimization problem the proper settings of bus voltages, tap settings of transformers, and reactive compensation devices. The optimization problem can be solved considering different objects such as decreasing power loss of the system, increasing voltage stability and also decreasing voltage deviation of buses. In this work a compromising multi-objective approach has been used to solve the reactive power control problem. Also for solving the optimization problem the global best harmony search algorithm has been used. The IEEE_57 bus system has been used in this study. The results are compared with other optimization algorithms and the results show that the selected approach is effective and approaches feasible results.

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Keywords:  Multi objective Operation; Global Harmony Search Algorithm (GHSA); Power Losses; Voltage Stability; Voltage Profile.



go to top   Improving Mho and Quadrilateral Relays Performance during Power Swings
         by Doaa Khalil Ibrahim, Ahmed F. Zobaa, Essam Abo El-Zahab, Ghada M. Abo-Hamad

           Vol. 5. n. 6, pp. 2919-2928


Abstract - Power swings, both stable and unstable, may precipitate wide spread outages to power systems with the result that cascade tripping of the power system elements occur. This paper deals with improving Mho and Quadrilateral relays performance under power swing conditions by discriminating between faults and power swings phenomenon. Distance relay may misinterpreted power swing as three-phase fault, but wavelet transform is able to discriminate clearly between power swings and faults. So, a logic block for fault detection based on the wavelet transform combined with the output of the conventional distance relay is proposed. Only voltage signals are used in wavelet relay to distinguish between fault and power swings conditions. The described scheme has been tested on a double line simulated power system using MatLab program.

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Keywords:  Fault Detector, Mho Relay, Power Swing, Quadrilateral Relay, Wavelet Transform.



go to top   Generation Expansion of a Hydro Producer by Constructing Pumped-Storage Plant
         by M. Najafi, M. Hoseinpour, M. Siahi

           Vol. 5. n. 6, pp. 2929-2935


Abstract - This paper addresses the generation expansion of a price-taker hydro generating company by means of pumped-storage plant construction. This company comprises several cascaded hydro plants along a river basin. By assuming the existence of a suitable zone as a natural reservoir, the hydro producer would like to evaluate the economic justification of pumped-storage plant construction using the mentioned natural zone as upper reservoir and one of his hydro reservoirs as lower reservoir. Before commencing the construction of this pumped-storage plant, its economic merit must be evaluated. In order to reach this goal, the profits of pumped-storage operation in the possible markets such as energy and ancillary service markets should be determined. It is essential to have an appropriate strategy to calculate the profit amount. Hence, a comprehensive approach to self-schedule hydro producer before and after of pumped-storage construction is developed. Comparing the results of mentioned self-scheduling problems in a specific time interval, the net profit of pumped-storage plant in this interval can be obtained. Then, the economic justification of pumped-storage plant construction can be determined using Internal Rate of Return (IRR) index during its expected life time. As well as energy market, the spinning reserve and regulation services are considered as ancillary services that hydro producer can participate in their markets. The self-scheduling problem of hydro producer is therefore formulated and solved as a mixed integer non-linear programming (MINLP) problem. Numerical results for a case study are discussed.

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


Keywords:  Hydro Producer, Pumped-Storage Plant, Generation Expansion, Self-Scheduling, Energy Market, Spinning Reserve Market, Regulation Market.



go to top   Multi-Objective Evolutionary Programming for Optimal Grid-connected Photovoltaic System Design
         by S. I. Sulaiman, T. K. A. Rahman, I. Musirin

           Vol. 5. n. 6, pp. 2936-2944


Abstract - This paper presents a multi-objective-evolutionary programming (MOEP) algorithm for sizing grid-connected photovoltaic (GCPV) system. Unlike previous studies which focused on the sizing of GCPV system based on a single objective optimization problem, the sizing of GCPV system in this study was initially converted into a three different bi-objective optimization problems. The objectives were formulated based on the aim to maximize the expected technical and economic performance indicators for the system design. Apart from that, in each bi-objective optimization problem, the proposed MOEP was used to select the optimal combinations of photovoltaic (PV) module and inverter such that the optimal values of the two performance indicators could be achieved in a single run. The performance of the proposed MOEP-based sizing algorithm was later compared with the performance of the weighted sum method (WSM)-based sizing algorithm. In addition, when illustrating the effectiveness of the proposed MOEP in approximating the Pareto front, the non-dominated solutions from MOEP were compared with a benchmark algorithm which produced all possible design solutions. The proposed MOEP-based algorithm was found to outperform WSM in providing faster computations and better approximation of the Pareto front.

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


Keywords:  Multi-Objective Evolutionary Programming (MOEP), Grid-Connected Photovoltaic (GCPV), Inverter, Module, Photovoltaic (PV).


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