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

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


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



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







International Review of Electrical Engineering - Papers- Part A


go to top   PSO Based Energy Management Strategy for Pure Electric Vehicles with Dual Energy Storage Systems
         by F. Esposito, V. Isastia, S. Meo

          Vol. 5. n. 5, pp. 1862-1871


Abstract - The paper deals with a new energy management strategy for pure electric vehicles (PEV) with dual energy storage systems (battery and ultracapacitor). The proposed strategy is able to split the power demand between battery and ultracapacitor maximising the driving range and the performances of the vehicle and increasing the life cycle of the battery. To accomplish load sharing an energetic model of the PEV is formulated and an optimal control problem with inequality constraints is resolved using the particle swarm optimization technique (PSO) to search the global near-optimum at each sample interval. Different types of batteries (lead-acid, NiMH and Li-ion) have been considered alternatively togheter with the supercapacitor. The results show that the proposed strategy guarantees energy saving and assures failsafe operations for the battery unaffecting the drivability of the vehicle.

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Keywords: Pure Electric Vehicles (PEV), Energy Management Strategy, Energy Storage System (ESS), Particle Swarm Optimization (PSO), Batteries, Ultracapacitors, Load Sharing.



go to top   A New BLDC Motor for Propulsion Application
         by A. Kolahdooz, M. Shakeri

          Vol. 5. n. 5, pp. 1872-1878


Abstract - The paper presents a new BLDC Motor for Propulsion Application. The suggested motor is a direct drive motor and consents to reduce the total weight of the system and to achieve higher efficiency in all the solutions that envisage an induction motor and its' transmission system for an propulsion application. The paper explaining the design guidelines presents also a suitable method for direct motor drive design. The proposed motor is a 24-pole, 36-slot brushless DC motor whose rotor with rare earth magnets to realize an inner rotor direct drive motor. The design and optimization of the motor was done with the aid of finite element Magnetostatic and Transient field analysis using the Maxwell 2D Simulator software. The results of simulation were compared with the results of experimental data. The numerical results were in good agreement with experimental ones.

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Keywords: BLDC motor, Design Procedure, Finite Element Method, Prototype Model.



go to top   High Power Factor Converter with Integrated Zeta-Flyback Topology
         by Bor-Ren Lin, Ming-Hung Yu

           Vol. 5. n. 5, pp. 1879-1886


Abstract - This paper presents a single-stage AC-DC converter with zeta and flyback topologies to realize the functions of power factor correction, current harmonics reduction and reactive power compensation. The buck-boost topology is adopted in the front stage to reduce the DC bus voltage stress. Thus the low voltage stress of power switches can be used in the converter. Since the buck-boost converter is operated in the discontinuous conduction mode (DCM), the input AC line current is automatically following the utility voltage and the line current is a sinusoidal waveform and in phase with AC mains. The zeta and flyack converters are integrated in the primary side and connected in parallel at the output side to share the power components in the transformer primary side, achieve the partial magnetizing flux reset and share load power. Experimental results, taken from a laboratory prototype rated at 144W, AC source voltage of 110Vrms, output voltage of 24V, and switching frequency of 55kHz, are presented to demonstrate the converter performance.

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Keywords: zeta converter, flyback, buck-boost, power factor correction.



go to top   Efficiency Improvement of Series-Connected Boost Converters
         by M. Taherbaneh, H. Ghafoorifard, A. H. Rezaie, M. B. Menhaj, K. Rahimi

           Vol. 5. n. 5, pp. 1887-1897


Abstract - Nowadays, power converter industry is moving fast toward two important goals: high efficiency and small weight and size. In this way, switching frequency is a good solution for achieving those goals, but it has two sides. A higher switching frequency allows us to use smaller components so it reduces the size and the weight of converter, in return it reduces efficiency. The use of high frequency in full load is an obligation, since it helps us to avoid excessive output ripple and core saturation problem, thus we can ignore its bad impact on efficiency. At light load, which the limitations of core saturation and excessive output ripple are not faced, it is possible to increase efficiency by using lower switching frequency. This paper shows the practical implementation of a variable switching frequency scheme for a DC-DC converter used in a SCBC and its impact on increasing the overall efficiency of the SCBC. Various methods of implementation are discussed and experimental results are provided. Finally, it was shown that efficiency can be improved up to 15% at light loads for the interior DC-DC converter and up to 11% for the SCBC.

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Keywords: Switching Frequency, Load Current, Efficiency, SCBC, Push-Pull Converter.



go to top   Bidirectional Operating of Inverse KY Converter
         by K. I. Hwu, Y. H. Chen

           Vol. 5. n. 5, pp. 1898-1906


Abstract - An inverse KY converter, derived from the KY converter, is proposed herein. And such a converter can be used as a bidirectional converter, whose operating modes are classified into two modes. One is the buck mode and the other is the boost mode. This converter can operate stably between these two modes. In this paper, the detailed illustration and mathematical deduction for the basic operating principles of the proposed topology are given, along with some measured results to verify its effectiveness.

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Keywords: Bidirectional Operating, Inverse KY Converter, Buck Mode, Boost Mode.



go to top   A Comparative Study of Reliability in Single and Two Stage PFC
         by A. H. Ranjbar, B. Abdi, G. Gharehpetian, B. Fahimi

           Vol. 5. n. 5, pp. 1907-1915


Abstract - In this paper, two-stage boost-forward PFC converter is compared with the fly-back converter, as a single-stage PFC, from reliability point of view. Based on measured results, the reliability of the single-stage and two-stage PFCs have been quantified and calculated. It is shown that the single-stage PFC offers a higher reliability than the latter. The comparison between single-stage and two-stage PFC from efficiency and cost points of view, indicates that the single-stage PFC is superior to the two-stage PFC.

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Keywords: Power Factor Correction, Reliability, Single-Stage PFC, Two-Stage PFC.



go to top   Digital Controller Dynamic Response Modification of SDM-based PFC Converter
         by M. Daryabak, J. Milimonfared, G. B. Gharehpetian, I. Salabeigi, M. Taheri

           Vol. 5. n. 5, pp. 1916-1921


Abstract - The sigma delta modulation advantage is its special power spectrum density which is better than other modulation techniques from EMC point of view. The disadvantage of this modulation technique is its low dynamic response in the case of using conventional control methods. The proposed digital control method of this paper improves the dynamic response of the boost power factor correction pre-regulator. The experimental results show the capability of the proposed modulation technique.

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Keywords: Boost PFC; Sigma-delta modulation; Digital control.



go to top   Real Time Control of Multi-Level AC/AC Converters with Strategy of DC Link Balancing
         by Mahmoud Samiei Moghaddam, Yousef Khadivi Vaneqi

           Vol. 5. n. 5, pp. 1922-1929


Abstract - A new control algorithm for AC/AC Modular Multi-Level Converter (MMLC) is introduced. This new control algorithm stands out due to its real-time operation and usage of all possible switching states in an MMLC. Independent control of output AC voltage with respect to the input AC voltage or load current is the second feature of the proposed algorithm. This control algorithm is well suited for balancing of DC link voltages which is an important factor when comparing control algorithms. It is shown that this modulation technique is advantageous for implementation of FACTS controllers and high power motor drives.

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Keywords: MMLC, Voltage Balancing , FACTS Controllers, Modulation.



go to top   High Voltage Pulse Driver with Energy Recovery Circuit for CNT-FEL
         by C.-H. Lin, C.-M. Wang, M.-H. Hung

           Vol. 5. n. 5, pp. 1930-1938


Abstract - This paper investigates a high voltage pulse driver for driving tubular carbon nanotube field emission lamp (CNT-FEL) based on a two-switch flyback topology. The proposed driver incorporates an energy recovery circuit to feedback the excess energy to DC bus, thus eliminating the arcing phenomenon caused by the traditional DC driving and improving the system efficiency. The two-switch flyback topology is used to share the high voltage stress. And the clamping circuit is incorporated to shift upward the bipolar voltage pulse to be unipolar voltage pulse. The proposed driver is operated in the discontinuous conduction mode (DCM) to suit the low power requirement and to generate the desired pulse power driving, which is the best strategy for prolonging the lifespan of CNT-FEL. Analytical modeling, simulations, complete design considerations, and experimental results confirm the validity of the theoretical predictions by the proposed low cost and simple circuit architecture.

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Keywords: Flyback converter, Pulse driver, Carbon Nanotube, Field emission, Energy recovery.



go to top   PV Based LED lighting with Integrated Sepic-Flyback Converter

         by Bor-Ren Lin, Ming-Hung Yu

           Vol. 5. n. 5, pp. 1939-1947


Abstract - An integrated sepic-flyback converter for PV-based LED lighting system is proposed in this paper. In the proposed converter, the sepic converter is used to draw solar energy via PV cell modules to battery bank in charging mode during the daytime. In the nighttime, soft switching flyback converter is used to drive LED lighting system in discharging mode. Power switches of sepic converter and soft switching flyback are integrated to reduce component count. Synchronous switch technique is used in the sepic converter to reduce conduction losses on semiconductors. Thus, the smaller size, lighter weight and higher efficiency can be achieved in the proposed circuit. Finally, laboratory experiments with a 140W prototype, verifying the effectiveness of the proposed converter, are described.

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Keywords: Zero-voltage switching (ZVS), active clamp circuit.



go to top   Soft Switching of KY Converter with Input Current Spike Suppressed

         by K. I. Hwu, Y. T. Yau

           Vol. 5. n. 5, pp. 1948-1955


Abstract - In this paper, a simple soft switching technique, together with input current spike suppressed, is applied to the KY converter, also named 1-pluse-D converter, to upgrade the efficiency in the vicinity of the rated load and hence enhance its capability in industrial applications. The basic operating principles of the proposed soft switching scheme for the KY converter are illustrated and verified by some simulated and experimental results.

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Keywords: KY Converter, 1-Plus-D Converter, Soft Switching, Input Current Spike.



go to top   Weighted Differential Evolution Based PWM Optimization for Single Phase Voltage Source Inverter
         by H. Yahia, N. Liouane, R. Dhifaoui
           Vol. 5. n. 5, pp. 1956-1962


Abstract - Programmed pulse width modulation (PPWM) techniques require the solution of a set of nonlinear transcendental equations in order to obtain the switching angles. The main problem of almost all of them is solving these complex equations. Normally iterative methods such as Conjugate Gradient Descent Method and Newton-Raphson Method are used to solve these equations. To obtain convergence with numerical techniques, the initial values of the variables must be selected considerably close to the exact solution. Also In most cases only a local minimum can be obtained after considerable computational time. In this paper, a variant of differential evolution algorithm (DEA) is used to find the switching angles of a PPWM controlled inverter in a way that selected harmonics are removed from its output and the magnitude of fundamental is set at any desired level. The output waveform and spectrum results from simulation and experimental Digital Signal Controller (dsPic) PPWM inverter are presented to confirm the effectiveness of the proposed Weighted Differential Evolution (W-DE) method.

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Keywords: Differential Evolution, Digital Signal Controller, Programmed Pulse Width Modulation, Voltage Source Inverter, weighted Differential Evolution.



go to top   Sliding Mode PWM Control for a Buck Converter Under DCM/CCM Boundary
         by A. Savu, C. Radoi, A. Florescu
           Vol. 5. n. 5, pp. 1963-1971


Abstract - This paper presents the design and analysis of a fixed frequency sliding mode pulsewidth modulation voltage controller for a Buck converter operated under DCM/CCM boundary. The voltage controller has a similar structure as a PD type controller, but with additional instantaneous output voltage which is fed into the controller’s control law. Theory is validated by simulation and experimental results, which are in good agreement.

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Keywords: Buck converter, pulsewidth modulation (PWM), sliding mode (SM) control, discontinuous / continuous conduction mode (DCM/CCM).



go to top   Analysis of a ZVS Converter with Series Connection Transformers
         by Bor-Ren Lin, Chia-Hung Chao

           Vol. 5. n. 5, pp. 1972-1978


Abstract - A soft switching converter to achieve zero voltage switching (ZVS) turn-on for power switches is presented in this paper. Two circuit cells are connected in parallel at the primary side in order to achieve ripple current reduction at input capacitor and to reduce the size of transformer core. Active snubber is connected between two transformers in order to absorb the energy stored in leakage and magnetizing inductances and to limit voltage stresses across switches. Output capacitance of two switches and leakage inductance of two transformers are resonant during the commutation stage of main and auxiliary switches. Thus, power switches can be turned on at ZVS. Circuit configuration, operation principles and design considerations are presented. Finally, laboratory experiments with a 300W prototype, verifying the effectiveness of the proposed converter, are described.

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Keywords: Zero voltage switching, soft switching.


go to top   A New Isolated DC-DC Converter with Active Clamp Circuit
         by M. Delshad, B. Fani

          Vol. 5. n. 5, pp. 1979-1986


Abstract - In this paper a new single switch isolated buck-boost type dc-dc converter is introduced with low number of components. This converter is PWM controlled and energy is transferred to the output in both on and off switch states. An active clamp circuit is applied to the proposed converter to provide zero voltage switching condition in both buck and boost modes. Since this converter operates over a wide input voltage range, it can be employed as a power factor correction converter. Theoretical analysis is presented and the experimental results verify the converter analysis.

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Keywords: Soft Switching, Pulse Width Modulation (PWM), Buck-Boost type, DC-DC Converter, Zero Voltage switching (ZVS), Active clamp circuit.



go to top   Compact Waveguide Bandpass Filters using Dielectric Backed Patterned Conducting Planes
         by H. Ghorbaninejad-Foumani, M. Khalaj-Amirhosseini

           Vol. 5. n. 5, pp. 1987-1993


Abstract - In this paper compact bandpass waveguide filters consisting of dielectric backed patterned conducting planes (PCP) and air filled or dielectric filled waveguide sections are developed in order to realize drastic size reduction of filters. This design is different from common procedures which have been introduced and mainly rely on air filled waveguide microwave filters. The PCPs provides resonators by the combination of aperture elements and patch elements. In this manner the shape of each PCP is designed by genetic algorithm (GA) approach so that the resonant characteristic of PCPs can be fitted to that obtained from an equivalent circuit model. After designing of such PCPs, by using waveguide sections which are partially or fully filled with dielectric, a bandpass filter has been constructed. Furthermore for size reduction using the technique presented in some works, the whole length of filter has been reduced more. Coupled magnetic filed integral equation is applied which accurately takes higher order mode interactions and dyadic green’s functions are derived. Finally a set of linear matrix equations are solved using method of moment (MoM). Furthermore the set of derived matrix linear equations generally can be used for modeling of a variety of structures. The usefulness of the proposed structure and its performance are verified by designing and simulating some equal ripple bandpass filters.

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Keywords: Coupled Magnetic Field Integral Equations, Genetic Algorithm (GA), Patterned Conducting Planes, Wave Guide Bandpass Filter.



go to top   New Method of Vibration Analysis of Signal Force of Skew Permanent Magnet in Permanent Magnet Linear Synchronous Motors

         by Javier Rivas-Conde, Gabriel González-Palomino, Edwin Laniado-Jacome, Jaime Montoya-Larrahondo

           Vol. 5. n. 5, pp. 1994-1999


Abstract - In this work we perform two models of Permanent Magnet Linear Synchronous Motors (PMLSMs). Both are analyzed by finite element method with different position angles of the magnets which are called skew angles. This article proposes a technique to determine the maximum and minimum levels of vibration produced by the presence of ripple on the thrust of PMLSM by the interaction between magnets and stator slots and the harmonic magnetic flux density in the air gap. The technique is defined by the analysis of the vibration signal produced in the PMLSM, applying the Fast Fourier Transform (FFT) with spectral analysis technique, as the application to rotating machines, to see which is the skew angle that produces lower levels of vibration.The proposed numerical model was analyzed with commercial software Flux ™ using the finite element method. The data analysis of vibrations caused by variations in the thrust of the model is done with commercial software MatLab ™.

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Keywords: FFT, PM Skews, PMLSM, Ripple, Spectral Analysis, Statistical Regression Method Thrust.



go to top   High Performance Induction Motor Drive Using Hybrid Fuzzy-PI and PI Controllers: a Review
         by A. Saghafinia, H. W. Ping, M. A. Rahman

           Vol. 5. n. 5, pp. 2000-2012


Abstract - Applications of fuzzy logic controller (FLC) to induction motor (IM) drives are on the rise. This paper presents an overview of high performance indirect field-oriented control (IFOC) of IM drives with the focus of hybrid fuzzy with self-tuning FLC - PI controller plus PI speed controller. It presents a systematic design of this controller and identifies the factors that yield robust performances for niche applications.

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Keywords: Induction Motor, Indirect Field Oriented Control, Hybrid Fuzzy, Self-Tuning, Self Tuning Fuzzy PI Plus PI.



go to top   Finite-Element Analysis of Permanent Magnets Structure and Switching Angle Effects on the Efficiency of Two-Phase Brushless DC Motor
         by A. Mehrdad Jafarboland, Abdolamir Nekoubin

          Vol. 5. n. 5, pp. 2013-2021


Abstract - In this paper effect of permanent magnets structure and switching angle on a two-phase brush less direct current motor (BLDC) is analyzed. BLDC motor with four different structures for permanent magnets is designed by using RMxprt software and efficiency of BLDC motor for different structures in full-load condition has been presented. Then the BLDC motor in different conditions by using Maxwell 3D software is designed and with finite element method is analyzed electromagnetically. At the end with the use of MATLAB software influence of switching angle on motor performance investigated and optimal angle has been determined. The results indicate that with correct choosing of permanent magnets structure and switching angle maximum efficiency can be found.

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Keywords: Permanent Magnets, Switching Angle, BLDC Motor.



go to top   Improved Design for Minimizing Torque Ripples at BLDC Motors Used in Washers
         by L. T. Ergene, Y. Donmezer

           Vol. 5. n. 5, pp. 2022-2032


Abstract - In this paper, a Brushless Direct Current (BLDC) motor is analyzed and redesigned for torque ripple reduction. This motor is produced and used for home appliances, specifically washers. Electromagnetic torque ripples are produced by two different effects in BLDC motors: first by reluctance discontinuities in the magnetic circuit (cogging), second by stator and rotor magneto motive force (MMF) harmonic interactions. A simple decrease in cogging torque can be achieved by changing some physical parameters such as magnet arc, slot openings, skewing etc. Similarly changing the winding type helps to decrease some harmonic component in the MMF. In this work, a systematic approach to identify and reduce the vibration sources is presented. Some torque ripple minimization techniques are proposed and simulation results are provided for the 24 slots, interior type BLDC motor used in washers. After various comparisons, the optimized solution is chosen for prototyping. The simulation and experimental results for the prototype is also presented. These results also supported with vibration and acoustic level measurement tests.

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Keywords: Brushless Rotating Machines, Finite Element Method, Harmonic Analysis, Permanent Magnet Motors, Vibrations.



go to top   Implementation of Sinusoidal PWM Based Three Phase Four Switch Inverter Fed Induction Motor Drive Using FPGA
         by Nalin Kant Mohanty, Ranganath Muthu

           Vol. 5. n. 5, pp. 2033-2038


Abstract - A four switch three phase inverter has several advantages compared to a six switch three phase inverter such as lower cost, lower switching losses, lesser electromagnetic interference and lesser complexity of the control algorithms and interface circuits to generate PWM logic signals.
This paper presents a novel Xilinx FPGA implementation of four switch three phase inverter (FSTPI) fed Induction Motor drive. In this proposed experimental work, Xilinx FPGA is used to generate the Sinusoidal PWM pulses for FSTPI to drive the 3-phase Induction Motor. The complete Xilinx FPGA based FSTPI fed IM drive is implemented in real-time using SPARTAN-3 processor for a 3 hp 3-phase Induction motor. The simulation of FSTPI fed drive is carried out by using MATLAB SIMULINK. Simulation and experimental results are presented to demonstrate the feasibility of the proposed system.

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Keywords: FPGA - Field Programmable Gate Array, FSTPI - Four Switch Three Phase Inverter, IM - Induction Motor, PWM - Pulse Width Modulation, SSTPI- Six Switch Three Phase Inverter, THD - Total Harmonic Distortion.



go to top   Analytical Method for Determining Axial-Flux Permanent-Magnet Machine Sensitivity to Design Variables
         by A. Mahmoudi, N. A. Rahim, W. P. Hew

           Vol. 5. n. 5, pp. 2039-2048


Abstract - This paper presents an analytical approach to determining sensitivity of a slotted axial-flux permanent-magnet machine to its design variables. The method is modeled on a simple nonlinear magnetic analysis of an equivalent magnetic circuit with a saturation-possible magnetic-reluctance core in a slotted axial-flux permanent-magnet machine. It calculates flux distribution and torque characteristic in various operating conditions. Its accuracy and validity are verified by results that match those of a Finite Element Analysis model. The method is as accurate as FEA but betters FEA with its shorter computation time, making it the better alternative in initial estimations and in expediting design optimization of electrical machines. Design parameters, for maximum output torque and efficiency iteratively adjusted through multi-objective optimal design, are selected via sensitivity analysis of the proposed magnetic circuit. Simulation results show AFPM machine efficiency to be affected the most by its diameter, followed by magnet fraction, and the least by back-iron thickness.

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Keywords: Axial-Flux Permanent-Magnet machine, Finite Element Analysis, Magnetic Circuit.



go to top   Application of a Four-Pole Hybrid Motor Structure Suitable for Modifying the Rotor Hybridization Ratio
         by E. Kandemir Beser, S. Camur, B. Arifoglu, E. Beser

           Vol. 5. n. 5, pp. 2049-2056


Abstract - This paper presents a four-pole hybrid motor structure suitable for modifying the hybridization ratio. First, some theoretical information is given about the generated torque by the proposed motor. Hybrid motor structure is introduced and reluctance and permanent magnet (pm) parts of the rotor are described in detail. The ratio of the reluctance and the pm parts are modified on the rotor and various rotor types are obtained. The angle between the parts is also changed by means of the suitable rotor shaft. Static torque measurements are realized for different values of the current and torque profiles are obtained for different hybridization ratio of the rotor and position of the parts. Average torque and torque ripple values are calculated from the torque profiles. The results of the motor types are compared to each other. It is possible to examine several motor types due to the proposed motor. Different combinations give different characteristics and each construction gives reasonable results compared to the others.

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Keywords: Hybridization, Hybrid Motor, Permanent Magnet, Reluctance, Torque Ripple.



go to top   Effects of Quadrature Axis Armature Reaction on Magnetic Circuit Time Harmonics and Stator Iron Losses in a Permanent Magnet Synchronous Generator with Embedded Magnets
         by H. Hamalainen, J. Pyrhonen, J. Nerg

            Vol. 5. n. 5, pp. 2057-2062


Abstract - In permanent magnet machines with inverse saliency and relatively large quadrature axis inductance, the armature reaction causes stator teeth to saturate under load. The phenomenon cannot be observed in no-load tests. Therefore, determining the iron losses in a normal no-load test does not suffice, as the iron losses under load may be considerably higher than the no-load iron losses. Losses are compared between different stator yoke thicknesses, and also different iron materials are used. Time harmonics are taken from 11 different points in the stator iron. Variations in the time harmonics are detected between different stator yoke thicknesses. This results in different losses at no load and at load. Iron loss results are obtained by using a loss surface (LS) model.

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Keywords: additional losses, iron losses, quadrature axis inductance, time harmonics.



go to top   Power Fluctuations Attenuation in Wind-PV-Diesel Hybrid System – Ultracapacitors and Batteries
         by M. A. Tankari, M. B. Camara, B. Dakyo, C. Nichita

           Vol. 5. n. 5, pp. 2063-2071


Abstract - In this paper, an energy transfer strategy in a Wind-PV-Diesel hybrid system is studied. The Photovoltaic (PV) panels and the wind generator are controlled to operate at their maximum power point, and the diesel generator is controlled to maintain the DC-bus voltage at a constant value. Ultracapacitors (UC) and batteries are used in a complementary mode to smooth the fluctuations induced by the wind generator (WGE) on the DC-bus. These fluctuations are distributed between the batteries and the UC, using two low pass filters. This study is focused on the frequencies distribution method and the power converters control strategies. An experimental tests bench is designed in the laboratory to validate the proposed energy management strategy. Some experimental results are presented and analyzed.

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Keywords: Buck converter; Buck-boost converter; Diesel generator; Photovoltaic panel; Storage devices; Ultracapacitors; Wind power generation.



go to top   Exergy Analysis of a Solar-Hydrogen Hybrid Energy System
         by Eylem Yilmaz Ulu, Harun Kemal Ozturk

           Vol. 5. n. 5, pp. 2072-2080


Abstract - In this study, exergy analysis of a photovoltaic-hydrogen production system established at the Clean Energy Center(CEC), in Denizli, Turkey has been investigated. Exergy analysis for photovoltaic systems is necessary for studying the PV performance and possible improvements. The exergy efficiency comparison of the fixed tilt(45o south) and mounted on solar trackers photovoltaic modules, is calculated here by the experimental datas taken from the system located in the CEC in Denizli, Turkey, at 37°46' North latitude and 29°05' East longitude. The experiments were carried out from 08:00 am to 18:00 pm, on July 13, 2010. It is seen that exergy efficiency of the fixed tilt PV module vary between 9,3% and 11,2%, while the  exergy efficiency of the mounted on solar tracker PV module vary between 9,7% and 11,9%.

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Keywords: Exergy analysis, photovoltaic, fuel cell.



go to top   Experimental Wavelet Packet Transient-State Analysis of Electrical Machines Directly Fed by Photovoltaic Cells
         by N. Onat, İ. Kıyak, G. Gökmen

           Vol. 5. n. 5, pp. 2081-2087


Abstract - This work describes an experimental wavelet packet transient state analysis for educational purposes. The study particularly deals with electrical machines directly fed by photovoltaic cells. In a PV system design, the selection and proper installation of appropriately-sized components directly affects system reliability, lifetime and initial cost. In any installation, one must keep in mind that trade-offs are necessary in system design and component selection. In this study, the startup and nominal operating behaviors of electrical machines directly connected to a photovoltaic system (not having any storage or control system) were empirically examined. The power values obtained (in p.u.) were decomposed to sub-frequency components by means of the discrete wavelet packet transformation then they were compared to each other.

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Keywords: Photovoltaic Cells, Transient State, Electrical Machines, Wavelet Filter Bank, Wavelet Packet Transform.



go to top   Stator Short Circuit And Broken Bar Faults Diagnosis Of An Indirect Vector Control Squirrel Cage Induction Motor
         by Souad Laribi, Azzedine Bendiabdellah

           Vol. 5. n. 5, pp. 2088-2094


Abstract - In this paper, the performance study of the vector control method applied to a three phase squirrel cage induction motor with stator short circuits faults, rotor broken bars faults as well as with both faults simultaneously is being presented. The fault diagnosis technique used in this work is based on the spectral analysis of electrical quantities such as current and voltage. Simulation as well as experimental results are being carried and presented to illustrate the influence of vector control on a faulty squirrel cage induction motor.

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Keywords: vector control, current and voltage spectral analysis, stator faults, rotor faults, squirrel cage induction motor.



go to top   Multiclass Support Vector Machines for Diagnosis of Broken Rotor Bar Faults Using Advanced Spectral Descriptors
         by A. Braham, H. Keskes, Z. Lachiri

           Vol. 5. n. 5, pp. 2095-2105


Abstract - This paper proposes an original combination of Power Spectrum Density estimation (PSD) and Support Vector Machines (SVMs) to diagnose and detect broken-rotor-bar faults in induction motor under different levels of load. The PSD estimate is used for feature extraction and aim to identify the descriptors that show high variability between different classes and thus would help distinguish between them. This paper analyses three different spectral decomposition methods applied to induction machine stator current, namely Welch, Burg and Multiple Signal Classification (MUSIC). Based on different power spectral estimation concepts, the frequency resolution, variance and detection capability are different for each method according to the set of parameters used. In this paper, the strategy of multiclass SVMs-based classification is applied to perform the faults recognition. The proposed methodology aims to determine which spectral estimate method best suited for implementation in SVMs. Also, the classification process performance due to the choice of kernel function is presented to show the excellent characteristic kernel function. Various scenarios are examined using data sets of stator current signals from experiments under different load, and the results are compared to obtain the best performance of classification process.

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Keywords: Induction Motor, Broken-Rotor-Bar, Fault Diagnosis, Power Spectrum Density Estimation, Multiclass Support Vector Machines.



go to top   A Comparison of PWM Strategies for Multilevel Cascaded and Classical Inverters Applied to the Vectorial Control
of Asynchronous Machine

         by M. Ayadi, L. El M’barki, M. A. Fakhfakh, M. Ghariani, R. Neji

           Vol. 5. n. 5, pp. 2106-2114


Abstract - The emergence of multilevel converters has been in increase since the last decade. These new types of converters are suitable for high voltage and high power application due to their ability to synthesize waveforms with better harmonic spectrum. Numerous topologies have been introduced and widely studied for utility and drive applications. Amongst these topologies, the multilevel cascaded inverter was introduced in Static Var compensation and drive systems.
This paper presents a comparison of PWM (Pulse Width Modulation) strategies for multilevel cascaded and classical inverters applied to the vectorial control of asynchronous machine in order to ensure an efficient utilization and better harmonic spectrum. A modelling and control strategy of a three phase multilevel cascaded inverter is also investigated. Computer simulation results using MATLAB program are reported and discussed together with a comparative study of the PWM strategies for multilevel cascaded and classical inverters.

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


Keywords: Asynchronous machine, control-oriented vector of rotor flux, PWM, cascaded multilevel inverter PSCPWM, junction temperature.



go to top   Analytical Modeling, 3-D FEM Analysis and Experimental Tests of a Capsule Pipeline System Driven by Dodecahedron Tubular Linear Induction Motor
         by M. H. Aliabadi, M. Ataei, M. Nafar, M. Heidari

           Vol. 5. n. 5, pp. 2115-2121


Abstract - In this paper analytical and 3-D finite element modeling of a Dodecahedron Tubular Linear Induction Motor (DTLIM) as a capsule pipelines system drive is developed. Initially analytical model has been studied to predict the distribution of current density, flux density and forces. The validity of calculation and the accuracy of assumption are assessed by comparing the results of the 2-D and 3-D finite element model with analytical model and experimental results. It can be seen that both analytical and three dimensional finite element computation have a good agreement with the experimental results.

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Keywords: Dodecahedron Linear Motor, Finite Element Method (FEM).



go to top   On-line Monitoring of Transformer Winding Axial Displacement Using UWB Sensors and Neural Network
         by G. Mokhtari, G. B. Gharehpetian, R. Faraji-dana, M. A. Hejazi

           Vol. 5. n. 5, pp. 2122-2128


Abstract - In this paper Ultra Wide Band (UWB) sensors and neural network has been used to detect the axial displacement of a simplified model of transformer. The proposed experimental set-up for this method has been modelled using CST (Computer Simulation Technology) software. The results of CST software are given to a neural network to be used for detection the amount of unknown axial displacement. It has shown that this method has a good accuracy to determine the displacement of the winding and its extent.

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Keywords: Transformer axial displacement, On-Line Monitoring, CST Simulation, UWB sensors.



go to top   Chaos Control via Optimal Generalized Backstepping Method
         by Ali RezaSahab, Masoud Taleb Ziabari, Seyed Amin Sadjadi Alamdari

            Vol. 5. n. 5, pp. 2129-2140


Abstract - One of the most important phenomenons in some systems is chaos; so control chaotic systems is difficult and shows the abilities of control methods. In this paper, first known chaotic systems, Lorenz, Chen and Lu equations, was selected as chaotic systems. One of the best control methods that would be used for stabilization these systems, was Backstepping. In this paper this method is improved to Generalized Backstepping Method (GBM). This method is called GBM because of its similarity to Backstepping and more applications in systems than it; Backstepping method is used only to strictly feedback systems but GBM expand this class. For this new method, expose a new theorem and its proof and for showing its abilities, control Lorenz, Chen and Lu equations in two participate sections; stabilization and tracking reference input. Generalized Backstepping approach consists of parameters which accept positive values. The parameters are usually chosen optional. The system responded differently for each value. It is necessary to select proper parameters to obtain a good response because the improper selection of the parameters lead to inappropriate responses or even may lead to instability of system. Genetic algorithm can select appropriate and optimal values for the parameters. GA by minimizing the fitness function can find the optimal values for the parameters. This selected fitness function is for minimizing the least square error. Fitness function forces the system error to decay to zero rapidly that it causes the system to have a short and optimal setting time. Fitness function also makes an optimal controller and causes overshoot to reach to its minimum value. This hybrid makes an optimal Backstepping controller.

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Keywords: Chaos, Lyapunov, Generalized Backstepping Method, Genetic Algorithm.



International Review of Electrical Engineering - Papers- Part B



go to top   Optimal Management of Microgrid in Island-Mode Using Bacterial Foraging Algorithm

         by Hesan Vahedi, Reza Noroozian, Abolfazl Jalilvand

           Vol. 5. n. 5, pp. 2141-2151


Abstract - This paper studies the general Microgrid architecture of an optimal power management to evaluate potential economic, technical and environmental benefits. In this context, the system model components from some real manufactured data are constructed. Also, the optimal operating strategy and cost optimization scheme using Bacterial Foraging Algorithm are introduced in detail. The generation resources and load demand are optimally dispatched and able to operate in island-mode (off-grid). The battery storage bank has been used for charging and discharging modes. However, the proposed cost function takes into consideration the reduction of the emissions caused as well as the operation and maintenance costs. Numerical results show that the optimization strategy has been achieved in an actual MG based on suitable stand-alone mode of operation.

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Keywords: Microgrid, Cost optimization, Bacterial Foraging Algorithm, islanding operation.



go to top   Fuzzy Clustering Techniques for the Analysis of PQ Data in Electrical Power Distribution System
         by Zahir J. Paracha, Akhtar Kalam

           Vol. 5. n. 5, pp. 2152-2158


Abstract - Power Quality (PQ) in electrical power system is of paramount importance to power utilities. Power quality issues are complex and have become diversified with the addition of non-linear loads in electrical power system which draws non-sinusoidal current from a sinusoidal voltage source. Power system problems related to non-linear loads need comprehensive analysis as there can be more than one reason for the power system instability. This paper investigates the power distribution system behavior by analyzing harmonics in distribution network in conjunction with other PQ parameters. It classifies the PQ data of harmonics of the power distribution network with voltage unbalance, sag and swell, power factor and power system frequency by employing fuzzy clustering techniques. It has been shown that GK based fuzzy clustering outperforms fuzzy C-mean clustering to accurately predict the important PQ parameters of the power distribution system.

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Keywords: Power Quality, Harmonics, Sag, Swell, Voltage Unbalance, Computational Intelligence, Fuzzy Clustering.



go to top   Robust Design of PID Controller for Power System Stabilization by using Real Coded Genetic Algorithm
         by Serhat Duman, Ali Öztürk

           Vol. 5. n. 5, pp. 2159-2170


Abstract - A real coded genetic algorithm based PID controller (RCGAPID) is presented in this paper to improve power system dynamic stability. The proposed RCGAPID parameters are optimized using real coded genetic algorithm (RCGA). The design problem of the proposed controller is formulated as an optimization problem and RCGA is employed to search for optimal PID controller parameters. Integral absolute error (IAE) and integral squared error (ISE) performance indexes have been used for the determination of the PID controller parameters in power systems stabilization. The performance of the proposed RCGAPID under various loading and small disturbance conditions are analyzed and compared in single machine infinite bus (SMIB) power system. Simulation results show the effectiveness and robustness of proposed controllers to improve the stability performance of power system.

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Keywords: Power system stability, PID parameter tuning, Real coded genetic algorithm, Optimization.



go to top   Calibration System For Electric Energy Quality Measurement Equipment
         by C. Vlaicu, A. Florescu, C. D. Oancea, C. Radoi

            Vol. 5. n. 5, pp. 2171-2176


Abstract - Because of electric energy quality requirements, it is mandatory to use in power network, measurement and monitoring equipment. Calibration system from this paper is necessary in design and calibration stage of these equipments. Main components are function generator driven by a computer through USB or GP-IB bus and a power amplifier with a wide frequency bandwidth (20Hz-5kHz). For example it can be used an audio amplifier, with a flat frequency characteristic. The function generator control software, done like a virtual instrument (VI), may give a sinusoidal waveform at multiple power line frequency. The amplitude and phase of signal can be adjusted, regarding the 1st order harmonic (50 or 60 Hz). Another facilities is to generate harmonics combinations (in this program additional 3 components) to check selectivity of tested equipment. The synthesized waveform is send to functions generator to convert in analog signal, which will be amplified by power amplifier stage. The system was build using HP33120A function generator and audio power amplifier based on power operational amplifier 3572 Burr Brown, with a known frequency output characteristic.

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


Keywords: Calibrator, Electric Energy Quality, Power Network.



go to top   Classification of Power Quality Disturbances by Using DOS-Transform and Support Vector Machines
         by Suriya Kaewarsa, Kitti Attakitmongcol

            Vol. 5. n. 5, pp. 2177-2185


Abstract - This paper presents a new method based on discrete orthogonal S-transform and support vector machines for classification of power quality disturbances. DOS-transform is mainly used to extract features of power quality disturbances and support vector machines are mainly used to construct a multiclass classifier which can classify power quality disturbances according to the extracted features. Results of simulation and analysis demonstrate that the proposed method can achieve higher correct identification rate, better convergence property and less training time compared with the method based on neural network.

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


Keywords: Power Quality, Discrete Orthogonal S-Transform, Support Vector Machines, Wavelet Transform, Neural Network.



go to top   Wavelet Transform Based Differential Protection For Power Transformer and Classification of Faults Using SVM and PNN
         by Sendilkumar Subramanian, Mathur Badrilal, Joseph Henry

           Vol. 5. n. 5, pp. 2186-2198


Abstract - This paper presents using wavelet transform for differential protection and neural networks for fault classification. The wavelet transform is one of the powerful signal-processing tool is used to extract information’s of differential current from wavelet coefficients. A two cycles of fault current data’s are processed to wavelet transforms, which produces wavelet coefficients, and features like energy and standard deviations are calculated using Parseval’s theorem. Extracted features are processed to Probability neural network and support vector machine for fault classification. Application of the proposed algorithm has been analyzed using different mother wavelets for signal processing. The application of the proposed simulation model has been studied by simulation of the fault (with and without noise) using MATLAB/SIMULINK software taking 2 cycles of data window (40 m sec) containing 800 samples. Tripping signals are issued using the energy vectors that calculated from wavelet coefficients. Classification accuracy for the combination of wavelet transform and Support vector machine has been found better than the combination of wavelet transform and Probabilistic neural network.

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


Keywords: Differential Protection, Inrush Current, Internal Fault, Wavelet Transform, Mother Wavelets, Probabilistic Neural Network And Support Vector Machine.



go to top   Real and Reactive Power Flow Allocation in Deregulated Power System Utilizing Genetic-Support Vector Machine Technique
         by M. H. Sulaiman, M. W. Mustafa, O. Aliman, S. N. Abd. Khalid, H. Shareef

           Vol. 5. n. 5, pp. 2199-2208


Abstract - This paper presents a technique to allocate the real and reactive power flow in deregulated power system environment by incorporating the hybridization of Genetic Algorithm and Least Squares Support Vector Machine (Genetic-SVM). The idea is to use GA to find the optimal values of hyper-parameters of LS-SVM and adapt a supervised learning approach to train the LS-SVM model. The manipulation of proportional sharing method (PSM) is utilized as a teacher. Based on converged load flow and followed by PSM for power flow allocation procedures, the description of inputs and outputs of the training data are created. The Genetic-SVM model will learn to identify which generators are supplying to which loads. In addition, the equivalent transmission model will be discussed in reactive power tracing methodology together with the concept of virtual load for both real and reactive power tracing methods. In this paper, 5-bus system and 25-bus equivalent system of southern Malaysia are used to show the effectiveness of the proposed method. The comparison with other method is also given.

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


Keywords: Deregulation, Genetic Algorithm, Least Squares Support Vector Machine, Proportional Sharing Method.



go to top   A Combinatorial Approach for Active and Reactive Power Flow Tracking
         by A. Rashidinejad, M. R. Habibi , H. Khorasani, M. Rashidinejad

           Vol. 5. n. 5, pp. 2209-2216


Abstract - This paper establishes a simple and topological approach to track real and reactive power flow in electric transmission systems. The presented method utilizes the well-known Proportional Sharing Theorem in order to evaluate the contribution of each power source to grid elements’ supplied input power. We have also put forward an approximate power tracing method for upgraded grids, using its own previously surveyed results. The main advantages of the proposed procedure, compared with conventional methods, are discussed extensively. The effectiveness of this approach has been studied and ascertained for small-scale power systems, showing prominent speed and accuracy.

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Keywords: Power Flow Tracking, Loss Allocation, Real & Reactive Power Approximation, Electric Power Transmission.



go to top   Active Power Loss Minimization in Electric Power Systems through Artificial Bee Colony Algorithm
         by S. Çobanlı, A. Öztürk, U. Güvenç, S. Tosun

           Vol. 5. n. 5, pp. 2217-2223


Abstract - Reactive power optimization (RPO) is an important area of study to provide working for power systems in a secure and economical way. RPO is used for the voltage control, decreasing of active power losses, and for the optimization of the power coefficients. In RPO the non-linear power loss function is used as a purpose function to be minimized. The control parameters of that function are bus voltages of the generators, level settings of transformers and the reactive power output values of the capacitors added to buses. Artificial Bee Colony (ABC) algorithm, one of the intuitive methods is used in this optimization study. In this study, by using the ABC algorithm, RPO provided on the IEEE 6-bus and IEEE 30-bus test systems. The ABC algorithm is compared with some heuristic algorithms. It is shown by the results that active power losses can be decreased by ABC algorithm.

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Keywords:  Power Systems, Optimization, Artificial Bee Colony Algorithm.



go to top   A New Protection Strategy for Electrical Distribution Systems
         by Angelo Campoccia, Antonio Cataliotti, Gioacchino Corso, Valentina Cosentino, Maria L. Di Silvestre, Eleonora Riva Sanseverino, Gaetano Zizzo

           Vol. 5. n. 5, pp. 2224-2233


Abstract - In this paper, the authors propose a new protection strategy for electrical Medium Voltage distribution networks, based on a distributed intelligence system composed of a central unit and of many local processing units. The distributed intelligence system can precisely identify and locate faults in suitably limited times. Each local processing unit is composed of a data acquisition system and a data analysis system. The first allows the accurate reconstruction of the fundamental using only 1.5 cycles of under fault transient electrical quantities. The second performs suitably precise on-line fault diagnosis based on the data provided by the data acquisition module. The data acquisition algorithm and the data analysis algorithm are managed by the data processing system of the remote processing units implemented on a micro-processor. With the proposed architecture, if local acquisition, elaboration and clearing times are limited, the faulted line experiences only two micro-interruptions, also during multi-phase permanent faults, with a great improvement of the quality of the service. Some experimental results on a simulated test system, proving the efficacy and simplicity of the proposed approach, are reported.

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


Keywords: Power Distribution Protection, Power System Faults, Fault Diagnosis, Fault Location, Fundamental Extraction.



go to top   Optimal Location and Parameters Setting of UPFC Based on Particle Swarm Optimization for Increasing Loadability
         by M. Sarvi, M. Sedighizadeh, J. Qarebaghi

           Vol. 5. n. 5, pp. 2234-2240


Abstract - Unified Power Flow Controller (UPFC) is one of the most effective Flexible AC Transmission Systems (FACTS) devices for increasing loadability of power system by minimizing the overloaded lines and the bus voltage violations. However, to what extent the performance of UPFC can be brought out, it highly depends upon the location and the parameters setting of this device in the system. This paper presents an approach to find out the optimal placement and the optimal parameters setting of UPFC for increasing loadability. The Particle Swarm Optimization (PSO) technique is used to find out the optimal location and the optimal parameters setting of UPFC for increasing loadability. To verify our proposed approach, we perform simulations on IEEE 14-bus power system and the results are compared to Genetic Algorithm (GA) in term on speed and accuracy of convergence. The results indicate that GA and PSO can successfully achieve the proper settings and placement of UPFC.

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


Keywords: Unified Power Flow Controller (UPFC), Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Loadability, Optimal Location.



go to top   Analysis and Design of PSS for Multi-Machine Power System Based on Sliding Mode Control Theory
         by Ghazanfar Shahgholian, Amin Rajabi, Bahram Karimi

            Vol. 5. n. 5, pp. 2241-2250


Abstract - This paper present a new method for design of power system stabilizer (PSS) based on sliding mode control (SMC) technique. The control objective is to enhance stability and improve the dynamic response of the multi-machine power system. In order to test effectiveness of the proposed scheme, simulation will be carried out to analyze the small signal stability characteristics of the system about the steady state operating condition following the change in reference mechanical torque and also parameters uncertainties. For comparison, simulation of a conventional control PSS (lead-lag compensation type) will be carried out. The main approach is focusing on the control performance which later proven to have the degree of shorter reaching time and lower spike.

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Keywords: Power System Stabilizer, Sliding Mode Control, Multi-Machine Power System, Controller Design.



go to top   Available Transfer Capability for Power System Planning Using Krylov-Algebraic Method
         by Mojgan Hojabri, Hashim Hizam, Norman Mariun, Senan Mahmod Abdullah, Edris Pouresmaeil

           Vol. 5. n. 5, pp. 2251-2262


Abstract - In transmission systems, due to uncertainties such as bus loading variation and transmission line status, estimation of the available transfer capability (ATC) is very difficult. This paper presents krylov-algebraic method to calculate deterministic ATC. This method is based on the algebraic equations and linear optimization method. Statistical analysis of ATC with time varying load and line outage are done on the IEEE- 118 bus system to determine ATC between three separated areas in this system. The probabilistic analysis is done to estimate the transfer of energy and it is analyzed to find a more reliable transaction path. Furthermore, it could be efficient power marketing. The results for the analysis enable the buyers and sellers of energy to make a better decision on energy pricing.

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


Keywords: Available Transfer Capability (Atc), Contingency Ranking, Load Time Varying, Line Outage, Power System Planning, Power Market.



go to top   Voltage Stability Enhancement by Optimal SVC and TCSC Location Via CPFlow Analysis

         by O. L. Bekri, M. K. Fellah, M. F. Benkhoris, A. Miloudi

           Vol. 5. n. 5, pp. 2263-2270


Abstract - In this paper, voltage stability assessment with appropriate representation of SVC and TCSC is investigated and compared in the IEEE 6-bus test. Continuation power flow, with accurate model of these controllers, is used for this study. Applying Continuation Power Flow analysis (CPFlow), the optimal location of these controllers is determined. The effects of these controllers on voltage stability are examined. It is found that these controllers significantly increase the loading parameter of power systems.

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


Keywords: FACTS, SVC, TCSC, CPFlow, Voltage Stability.



go to top   Virtual Power Plant: Concept and Operation Optimization Algorithm

         by M. Amin Salmani, S. M. Moghaddas Tafreshi, Alireza Bagherian

           Vol. 5. n. 5, pp. 2271-2279


Abstract - Considering recent growing trend towards new technologies in electrical power supply, the need for systemized controlling methods have emerged. Morphing from centralized into decentralized electrical power supplies, tremendous growth in Communication and information technology and the advent of environmental friendly, small size and efficient generators close to the loads have introduced new issues in power supply researches. Indicating small size and separate characteristics, the aggregation of these efficient generators can be developed as a virtual power plant (VPP) concept in order to provide added-value to the electric Power system. VPP is the primary solution for achieving cost efficient integration in distributed generation (DG) in electrical power market. In this paper an operation optimization algorithm is proposed to integrate two DGs and a micro grid into a VPP control area, containing several loads, which will be able to generate and sell electrical energy to loads and electrical power market. Suitable model is proposed to simulate suggested VPP, and the energy exchange between VPP and Grid. The optimization problem is here formulated as a non-liner maximization algorithm with constraints, where the objective function is profit of the VPP. Finally, solving a case study of the proposed VPP with GAMS and also genetic algorithm will be presented and the results will be compared.

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Keywords: Distributed Generation, Operation Optimization Algorithm, Profit Function Maximization, Virtual Power Plant.



go to top   Islanding Detection for Inverter-Based Distributed Generation Using a Hybrid SFS and Q-f Method

         by Hesan Vahedi, Abolfazl Jalilvand, Reza Noroozian, Gevorg B. Gharehpetian

           Vol. 5. n. 5, pp. 2280-2285


Abstract - Sandia Frequency Shift (SFS) Islanding Detection Method (IDM) has been widely applied to inverter-based distributed generators due to its small Non-Detection Zone (NDZ). In this paper, a new hybrid islanding detection method has been introduced, which is based on SFS and Q-f droop curve methods. The optimal SFS configuration is calculated by using instability criterion of phase angle and Bacterial Foraging Algorithm. The results are verified on MATLAB / Simulink environment.

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Keywords: Distributed Generation, Sandia Frequency shift, islanding; inverter, Bacterial Foraging Algorithm.



go to top   Comparison of Modified Shuffled Frog Leaping Algorithm and Other Algorithms for Optimal Distributed Generation Location and Sizing
         by Hadi Chahkandi Nejad, Rouzbeh Jahani, Heidar Ali Shayanfar

             Vol. 5. n. 5, pp. 2286-2292


Abstract - In this paper we propose a comparison between Heuristic Search and PSO optimization methods and Modified Shuffled Frog Leaping Algorithm (MSFLA) for optimal location and sizing of distributed generation in a distribution network. The objective function consists of power losses and improvement in voltage profile and the methods are tested on the IEEE 69-bus system. This study comprises a comparison between the proposed approaches. It shows the importance of installing the right amount of DG in the best suited location. Studies also show that if the DG units are connected at non-optimal locations or have nonoptimal sizes, the system losses may increase. Test results indicate that MSFLA method can obtain better results than PSO and the simple heuristic search method on the 69-bus radial distribution systems. The MSFLA can obtain maximum loss reductions for each of three types of optimally placed multi-DGs. Moreover, voltage profile improvement and branch current reduction are obtained.

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


Keywords: Distributed Generation; DG types; Optimal DG size; Modified Shuffled Frog Leaping Algorithm (MSFLA); Particle Swarm Optimization (PSO), Heuristic Search (HS).



go to top   An Application of Photovoltaic Cell for Improving the Electrical Power Quality
         by Narin Watanakul, Singthong Pattanasethanon, Apinan Aurasopon

           Vol. 5. n. 5, pp. 2293-2300


Abstract - This article applies the Photovoltaic (PV) Power conditioning system for low voltage distribution power system. The effect is compensated and protected sensitive equipment against balance/unbalance voltage Sags and interruption mitigation through Dynamic voltage restore (DVR) by three-level neutral point clamped (NPC) inverter. Strategy for the DVR controller is based on in-phase compensation with conserved energy storage DC-link from PV stand-alone system. The modeling system is designed to have reference voltage supply 0.5 pu and injected voltage 0.5 pu, PV cell system with the type of amorphous rated 5kWp. The energy storage with controlling battery charger uses buck-boost converter.
The result of the controlling system contains Power conditioning load rating of 10 kVA. Simulation is also conducted paralleled along with the prototype. As a result short duration of voltage , this system can compensate voltage 0-0.9 pu. Which is used to test the cause of electric fault current. This provides guideline to further analyze and improve Power conditioning in electrical system pertinent to stand-alone photovoltaic system.

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


Keywords: Power Conditioners, Power Quality, Dynamic Voltage Restorer (DVR), PV Stand-Alone, Voltage Sags/Interruption Mitigation, Neutral Point Clamped (NPC) Inverter.



go to top   A Novel Voltage Sag Source Detection Method Using TFR Technique
         by Mohamed F. Faisal, Azah Mohamed, Hussain Shareef

           Vol. 5. n. 5, pp. 2301-2309


Abstract - Voltage sag is considered as the major power quality disturbance that can disrupt the operation of sensitive equipment. Many power utilities around the world install power quality recorders at strategic sites to monitor the frequency and severity of voltage sags that may affect their customers. The immediate identification of sources of voltage sags is very critical in providing information to customers to resume back their operations. The sources of voltage sags can originate either from upstream or downstream with respect to the monitoring point. This paper presents a novel method to identify the sources of voltage sags using a signal processing technique called the S-transform (ST). An index named S-Transform Disturbance Power (STDP) was developed to identify the origin of the voltage sags. The results of this study showed that the novel method is superior to the other methods in detecting the origin of both symmetrical and asymmetrical voltage sag in actual power systems.

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


Keywords: Power Quality, Signal Processing, Sources of Voltage Sags, S-Transform.



go to top   A Comprehensive Fault Location Estimation Using Voltage Sag Profile for Non-Homogenous Distribution Networks
         by H. Mokhlis, H. Y. Li, Hasmaini Mohamad, A. H. A. Bakar

           Vol. 5. n. 5, pp. 2310-2316


Abstract - An improvement in service continuity of power supply in distribution system could be achieved through a fast fault location. In line with this objective, a fault location method for a distribution network is proposed in this paper. The method uses non-linear voltage sag profile equations as a means to locate a fault. Considering the possibility of having non-homogeneity of line impedances in distribution network, the voltage sag profile equations are constructed for each section. The possible fault location is estimated by incorporating the measured voltage magnitude and its corresponding phase angle into equation of voltage sag as a function of fault distance. The uncertainty of fault resistance is also considered in this method by constructing the voltage sag equations based on different fault resistance values. The performance of the algorithm is presented using an actual distribution network.

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


Keywords:  Faulted Section, Fault Distance, Non-linear Voltage Sags, Distribution Network.



go to top   Transient Stability Emergency Control Using Generator Tripping Based on Tracking Area-based Rotor Angle Combined with UFLS
         by Noor Izzri Abdul Wahab, Azah Mohamed

            Vol. 5. n. 5, pp. 2317-2326


Abstract - This paper concerns with transient stability control which is part of transient stability assessment which needs to be considered so that the power systems remained intact when failures originating from faults occurred in power systems. Conventional under frequency load shedding (UFLS) system is designed to retrieve the balance of generation and consumption following disturbances occurrences in the system. In UFLS method, whenever the system’s frequency drops below a predetermined value, the system loads are shed in stages. An efficient UFLS method needs to be devised so as to reduce the impacts of transient disturbance on power systems and prevent total system blackout. In this paper, an emergency control scheme known as the combined UFLS and generator tripping is developed in order to stabilize the system when unstable faults occurred in a power system. The performance of the combined UFLS and generator tripping scheme is compared with the conventional UFLS control scheme. The results show that the combined control scheme performed better.

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Keywords: Transient Stability Assessment, Transient Stability Index, Transient Stability Control, Generator Tripping.



go to top   Optimization and Coordination of UPFC Controls Using MOPSO
         by Nannan Yan, Zhengcai Fu

            Vol. 5. n. 5, pp. 2327-2332


Abstract - Multi-objective Particle Swarm Optimization (MOPSO) Algorithm is proposed to solve the coordinated design problem from optimization perspective. This study focuses on minimizing the dynamic interactions among different UPFC control channels which is of interest to the controller design. A systematic approach to apply MOPSO to multi-objective optimization is presented. The effectiveness of the method is verified by a single-machine infinite-bus (SMIB) power system with UPFC. On the basis of this model, comparison of the optimization effects between MOPSO and the Multi-objective Evolutionary algorithm (MOEA) is carried out. The obtained results show that the proposed MOPSO based strategy is capable of obtaining high quality solutions. Comparing with MOEA, the MOPSO based method provides better computation efficiency and stable convergence characteristics. The time-domain results show the effectiveness of the proposed coordinated design method of UPFC controllers.

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Keywords: UPFC, MOPSO, Coordinated Design, Multi-Objective Optimization.



go to top   Static Synchronous Compensator for Improving Performance of Power System: a Review
         by Ghazanfar Shahgholian, Jawad Faiz

           Vol. 5. n. 5, pp. 2333-2342


Abstract - Flexible ac transmission systems (FACTS) controller can provide better control than conventional control and achieve fast control response time. Static synchronous compensator (STATCOM) is one of the key FACTS devices based on voltage source converter (VSC) techn¬ol¬o¬g-y whose capacitive or inductive output current can be control¬l¬e¬d independent of the ac system voltage. In this review paper, the authors have tried to broadly categorize the research work done so far on the STATCOM. A substantial number of relevant research papers can be found on the plant, modeling, operation and control fundamentals of the STATCOM and their perfor¬ma¬n¬c-e study.

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Keywords: FACTS Device, STATCOM, Damping Controller, Model, Location.



go to top   A New Approach for Sub-transmission System Expansion Planning Using Genetic Algorithm
         by Seyed Hadi Hosseini, Saeid Jalilzadeh, Abolfazl Jalilvand, Amir Bagheri

           Vol. 5. n. 5, pp. 2343-2349


Abstract - This paper proposes a new approach for expansion planning of sub-transmission System (SS). Distribution network (downward grid) is considered in the problem by modeling it as the load points, then Modified Mathematical Clustering Algorithm (MMCA) has been used for candidate selection of sub-transmission substations. Finally Genetic Algorithm (GA) is employed to allocate the load points to the existing or candidate substations, and to find the best configuration of lines among the candidate ones. The proposed method is applied on a typical SS and the results are presented.

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Keywords: Sub-transmission System, Modified Mathematical Clustering Algorithm (MMCA), Genetic Algorithm.



go to top   A New Approach for Protection and Control of Distribution Systems with DG
         by Fatih M. Nuroğlu, Ayşen Basa Arsoy

           Vol. 5. n. 5, pp. 2350-2356


Abstract - The paper aims to propose a Central Coordination Relay (CCR) to provide a solution to islanding protection, which became one of the major issues as distributed generating resources penetrate into electrical distribution systems. The operating procedures of the relay are identified after defining islanded areas and fault areas. The relay is modeled and its response in a real based small-scale system is tested using DigSilent PowerFactory. It is shown that the CCR can maximize the DG capacity usage and improve service continuity in any fault conditions.

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


Keywords: Distributed Generation, Intentional Islanding, Central Coordination Relay.



go to top   Dynamic Investigation of Hybrid Phase Shifters for Damping Power System Oscillations Studies
         by A. Lashkar Ara, A. Kazemi, S. A. Nabavi Niaki

           Vol. 5. n. 5, pp. 2357-2365


Abstract - This paper develops dynamic investigations of Optimal Unified Power Flow Controller (OUPFC) and Hybrid Flow Controller (HFC) devices as Hybrid Phase Shifters (HPSs) and designs the control algorithm incorporated the nonlinear power system dynamic equations in order to damping power system oscillations. An adaptive optimal control strategy for damping power system oscillation is presented. The proposed control algorithm incorporates the nonlinear power system dynamic equations. The optimization method is numerically solved using Matlab and GAMS (General Algebraic Modelling System) software environments. The solution procedure uses Mixed Integer Non Linear Programming (MINLP) and Non Linear Programming (NLP) to solve the optimal control algorithm of HFC and OUPFC controllers, respectively. The performance of the controllers is tested on a Single-Machine Infinite-Bus (SMIB) power system. Furthermore, the nonlinear simulation results show that the control strategy improves the dynamic stability and coordinated design of HPS controller and Power System Stabilizer (PSS) improve greatly the system damping.

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


Keywords: Hybrid Phase Shifter (HPS), FACTS, OUPFC, HFC, PST, Dynamic investigation.



go to top   Qualitative and Quantitative Analysis of System Stability and Power Quality in Networks with DG of Different Penetration Levels
         by Mudathir F. Akorede, Hashim Hizam, Ishak Aris, Mohd Zainal A. Ab Kadir

           Vol. 5. n. 5, pp. 2366-2377


Abstract - The benefits offered by distributed generation (DG) in electric power systems have opened opportunities for the increasing penetration of DG in distribution networks. In normal operating conditions, the penetration level of DG can go up to 50 % of the load demand of the system, especially in radial networks, before it begins to have a negative impact on the power loss. However, this is not the case when the system experiences some contingencies, such as loss of a central generator, short circuit faults, sudden disconnection of a DG unit, loss of a main transformer or a transmission line, etc. For this reason, it is necessary to limit the capacity of DG to be penetrated in a particular power network. This paper investigates the impact of different penetration levels of DG in both subtransmission and distribution networks. In the study, a 15-bus test system is employed and modelled in detail using Power System Analysis Toolbox (PSAT). Only synchronous type of DGs is considered since it is the most popular type is use. In this work, the impact of DG of different penetration levels on system stability and power quality are thoroughly examined under different fault scenarios. The results obtained suggest that 20 % penetration level of DG is optimal for both normal and during contingencies in the case study system.

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


Keywords: distributed generation, transient stability, rotor angle, voltage stability, synchronous generator, short circuit fault.



go to top   Participation in Reactive Power Market Considering Generator Aging
         by Ismail Niazy, Hashem Mortazavi, Jaafar Ebadi, Soheil Sabzevari, Abraham Niazy

           Vol. 5. n. 5, pp. 2378-2384


Abstract - As one of the most important ancillary services, reactive power production plays a crucial rule in power system operation, reliability and security. Because of the opportunity costs in providing reactive power, producers are under great pressure to provide VAr support. This paper presents a new challenge on the reactive capability curves (RCC) of the synchronous generator taking in account the normal limits of operation without exceeding thermal limitations. The importance of re-evaluation of RCC in the real world is because of the RCC is changed over time and aging of the generators. In this paper it is discusses about some reasons, which lead to the variations, and the importance of re-evaluation of RCC.

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


Keywords: Ancillary Services, Generator Capability Curve, Generator Aging, Reactive Power Market.



go to top   Optimal Operation of Combined Wind Power Generation and Pumped-Storage Units in the Electricity Markets
         by S. Aghajani, M. Kalantar

            Vol. 5. n. 5, pp. 2385-2391


Abstract - At present, wind power is the fastest growing kind of renewable energy in the world. Since wind has no production costs, all the productions are taken through the system. However, one of the major features of wind power is that the capacity of wind power changes according to the wind speed and consequently, wind forecasting is accompanied with uncertainty even in the short-term. In order to eliminate this shortcoming, in this paper the combination of pumped-storage units and wind farm are suggested. By this combination, pumped-storage unit can rectify uncertainty in wind power forecasting. In the present study, optimized operation of system power, along with the combination of pumped-storage and wind units are considered with the aim of minimizing the expected social cost in a short-term. Also, the uncertainty of the demand forecasting is discussed, too. The present model in this paper is scheduled on a three-bus system. Moreover, numerical results obtained from the operation of three cases (i.e., Base case and Base case with wind power unit and Base case with pump-wind coordination) have been demonstrated.

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


Keywords: Electricity Markets, Energy Storage, Stochastic Security, Uncertainty, Wind Power.



go to top   Social Welfare Maximization in Double-Sided Auction Market by Placement and Sizing of TCSC Using Fuzzy-Based Genetic Algorithm
         by Mohammad A. S. Masoum, Syed M. H. Nabavi, Ahad Kazemi

            Vol. 5. n. 5, pp. 2392-2404


Abstract - This paper presents a fuzzy-based genetic algorithm (Fuzzy-GA) to perform congestion management and maximize social welfare by placement and sizing of one TCSC device in a double-sided auction market. Simulation results (with line flow constraints, before and after the compensation) are used to analyze the impact of TCSC on the congestion levels of the modified IEEE 14-bus and 30-bus test systems. Conventional quadratic smooth and augmented quadratic nonsmooth (with sine components to introduce more accurate modeling that incorporates the valve loading effects) generator cost curves and quadratic smooth consumer benefit functions are considered. By adding the valve point effect, the model presents nondifferentiable and nonconvex regions that challenge most gradient-based optimization algorithms. The proposed approach makes use of the fuzzy-based genetic algorithm to allocate the near-optimal GenCos, DisCos and TCSC location and its size while the Newton–Raphson algorithm minimizes the mismatch of the power flow equations. Several cases are investigated to test and validate the consistency of detecting near global solutions. Simulation results are compared to solutions obtained by GA, sequential quadratic programming (SQP) and trial-and-error approaches. The main contributions are inclusion of customer benefit in the congestion management objective function, consideration of nonsmooth generator characteristics and the utilization of a fuzzy-based GA for locating/sizing of TCSC.

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


Keywords: Congestion Management, Social Welfare, Double-Sided Auction Market, Rescheduling, TCSC, Fuzzy And GA.



go to top   Application of Hilbert Huang Transform with Locally Weighted Projection Regression Method for Power Quality Problems
         by M. K. Elango, Dr. A. Nirmal Kumar, Dr. S. Purushothaman

           Vol. 5. n. 5, pp. 2405-2412


Abstract - This paper presents application of Hilbert Huang transform (HHT) and locally weighted projection regression (LWPR) for power quality disturbance classification. The input features to the LWPR are extracted from the envelope of the disturbance signals by applying Huang method called empirical mode decomposition (EMD) followed by Hilbert transform which gives instantaneous frequency and instantaneous amplitude. The features obtained from the HHT are unique to each type of electrical fault. These features are normalized and given to the LWPR. The data required are generated by simulating various faults in the test system. The performance of the proposed method is compared with the existing feature extraction techniques. Simulation results show the effectiveness of the proposed method for power quality disturbance classification.

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


Keywords: Harmonics, Hilbert Huang transform, Locally weighted projection regression, Power quality.



go to top   Locational Marginal Price (LMP) Assessment Using Hybrid Active and Reactive Cost Minimization
         by Hossein Zeynal, Alimorad Khajeh Zadeh, Khalid Mohamed Nor, Mostafa Eidiani

           Vol. 5. n. 5, pp. 2413-2418


Abstract - This paper presents a new aspect in assessment of Locational Marginal Prices (LMP). LMP values are the key indications, which enables handling settlement procedures in the competitive electricity markets, so the fairness and accuracy of LMP’s values have always been the central issues. An approach can be developed, where reactive power costs take part into the objective function of the system dispatch. The intent is to find what happens if the costs of active and reactive powers are explicitly bided and therefore minimized. It is indicated that the cost of system will be further minimized when the cost of both active and reactive powers simultaneously minimized. Unlike traditional way at which the cost of real power were only considered, the LMP values are calculated with respect to proposed objective function in which the active and reactive sources are optimally dispatched and all the system constrained came into the optimal region of operations. In short, this approach provides better and cheaper way to deal with system dispatch and its settlement procedures. The proposed method indicates that adding reactive power costs in the objective function of the system will affect the LMPs drastically and can increase the profits in the energy market. An IEEE-14 bus system is employed to represent the promised approach.

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


Keywords: Locational Marginal Price (LMP), Reactive cost optimization, AC-OPF, Electricity Market.



go to top   Reverse Power Data Analysis and Feature Extraction Based Upon Continuous Wavelet Transform for Electric Power Plants
         by Sezai Taskin, Serhat Seker, Burak Irgen, Tahir Cetin Akinci

           Vol. 5. n. 5, pp. 2419-2426


Abstract - This study is focused on the investigating of a power plant generator in reverse power condition. For this purpose, reverse power data were collected from a Combined Heat and Power Plant generator protection relay. The reverse power conditions were evaluated by means of the time-frequency and time-scale methods. As a result of this evaluation, it can be said that the time-frequency and time-scale properties of the signals like current, voltage, frequency, active and reactive powers were extracted with all details.

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


Keywords: Power plants, generator protection, reverse power, continuous wavelet transform.



go to top   Automating Consumers’ Connections to the Distribution Network for Enhanced Performance
         by O. M. Popoola, A. Jimoh, D. Nicolae

           Vol. 5. n. 5, pp. 2427-2438


Abstract - Trial and error approach which involves service interruption is usually carried out to resolve unbalance on phases in power distribution system. This approach might improve the phase voltage and current but the resultant effect (change) does not last for too long; thereby reduces the market value in terms of quality and reliability of supply. To enhance the performance of the secondary distribution system there is a need for an automating technology. The aim of this paper is to introduce a method and technology developed for resolving imbalances in a secondary distribution system as a result of the uneven distribution of single phase load across a three phase power system. The technology developed is able to monitor, acquire/display collected data and perform self changing switching actions electronically. This action is in form of rearrangement or transfer of consumer loads for optimal performance of the distribution feeder. The proposed switching technology is based on open- transition switch that enables transfer or rearrangement of consumer loads in a three-phase system within milliseconds with supervisory control system. The following methodologies: System Simulator - Matlab (Simulink), Virtual Instrumentation-Lab VIEW and Hardware implementation were applied for the validation of the proposed technique.

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


Keywords: Automated technology, Current imbalances, Load balancing, Phase arrangement, Static transfer switching.



go to top   Suppression of Fast and Very Fast Transients in GIS
         by A. Tavakoli, A. Gholami

           Vol. 5. n. 5, pp. 2439-2445


Abstract - Though lightning surges and switching operation have been reduced to an acceptable level in modern substation insulation coordination, still transformer failures related to lightning and switching are often reported in the gas insulated substation (GIS). There are methods to suppress the stresses created by very fast transient (VFT) from the source side. Ferromagnetic rings and resistor can be mounted on the conductors linked to the disconnector from both sides. Also extra arrester is a method for mitigation of lightning overvoltage. However, these methods are suitable before installing the substation and during the substation design period. This paper covers the estimation of the peak magnitudes of very fast transient overvoltage (VFTO), very fast transient currents (VFTC), and lightning overvoltage at various locations that have been computed in a typical GIS. The aim of this paper is to investigate methods for mitigation of overvoltage magnitude in GIS. The advantages of the proposed methods are their simplicity and low cost for implantation along with producing minimal changes in the installed GIS. Computer simulation has been done using the alternative transients program (ATP).

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


Keywords: Gas Insulated Substation (Gis), Switching, Lightning Overvoltages, Very Fast Transient Overvoltages (Vftos), Very Fast Transient Currents (Vftcs), Suppression.



go to top   Fuzzy Clustering Analysis for PD Signals in GIS Based on the Validity Index
         by Hui Wang, Yong Qian, Linpeng Yao, Chengjun Huang, Xiuchen Jiang

           Vol. 5. n. 5, pp. 2446-2451


Abstract - Cluster validity index algorithm, which can find the number of clusters in a given object set, plays an important role in clustering analysis. There have been many proposals of cluster validity index, especially for fuzzy clustering, and many of them are dependent on clustering algorithms that can use the different interpretations of similarities between objects, usually in the geometric interpretation of objects. We introduce the Gustafson-Kessel (GK) and Fuzzy C-mean(FCM) clustering algorithms in this paper to separate the four different partial discharge(PD) defects in gas insulated switchgear (GIS), according to the parameters of Skewness (Sk), Kurtosis (Ku), number of peaks (Pe), cross-correlation factor (CC) and the discharge factor Q.

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


Keywords: Gas Insulated Switchgear (GIS), Partial Discharge (PD), Cluster Validity Index, Fuzzy Cluster Analysis, Gustafson-Kessel (GK) Algorithm, Fuzzy C-Mean (FCM) Algorithm.



go to top   Distance Relay Mal-Operation Caused by Voltage Inversion due to Presence of TCSC on Adjacent Lines
         by S. Jamali, A. Kazemi, H. Shateri

           Vol. 5. n. 5, pp. 2452-2460


Abstract - This paper discusses the distance relay mal-operation in the presence of Thyristor Controlled Series Compensator (TCSC), one of the 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. This is done by presenting the measured impedance at the relaying point in the presence of TCSC at the near end of the line behind. The measured impedance is greatly influenced by the presence of TCSC on a transmission line or even in the case of TCSC installation at the adjacent lines, near end of the line behind. The measured impedance depends on many factors including power system structural conditions, pre-fault loading, the fault resistance, and TCSC compensation degree.

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


Keywords: Distance protection, FACTS devices, Locus of the apparent impedance, Measured impedance, TCSC.



go to top   A Critical Review on the Contamination Effect on Distribution Overhead Lines
         by Zawati Mohd Nawi, Nor Ratna Misbah, M. Z. A. Ab. Kadir

           Vol. 5. n. 5, pp. 2461-2470


Abstract - Year by year, performance of the power system distribution lines is one of the important subject that need to be considered. This paper presents a review on the effects of contamination on distribution overhead lines. Apart from the physical configuration of the lines such as lower in height and simple build-up structure, the location of the lines and the withstand capability of the systems are among another factors that determine the performance of the line. Insulator, which is used in between the cross-arm and phase conductor for instance, is very much sensitive to the surrounding environment such as humidity (wet and dry) and contamination such as salt, cement, dust, smog and etc. In the event of the direct or indirect effects of the lightning for instance, this contamination will affect the breakdown strength of the insulator which will result in the flashover across the insulator or coordination gap. This paper will consider in details the effect from different contaminants and different types of testing in evaluating the performance of the insulator. At the end of the paper, some mitigations approaches will be suggested with respect to the issue being discussed.

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


Keywords: Lightning, Insulator, Contamination, Withstand Capability, Distribution System.



go to top   Experimental Study of Leakage Current and Calculation of ESDD of Polluted Composite Insulators
         by I. A. Joneidi, A. A. Shayegani, H. Mohseni

           Vol. 5. n. 5, pp. 2471-2477


Abstract - The faults which are arisen due to the polymeric insulators pollution are the problem which currently influence on the transmission and distribution line of polluted areas. Occurrence of this kind of faults leads to power quality and safety ability decrement of distribution lines. In case of wet pollution, pollution layer create an appropriate path for leakage current and increasing of this pollution leads to more values of this leakage current. Therefore for better recognition of insulator changing process from normal state to fault outbreak, studying of leakage current and artificial aging models is necessary. In this paper, the experimental test results on two insulators with profile and voltage of 20 and 63 KV have been shown. Artificial aging on insulators has been done using solid layer methods according to IEC60507 standard. Leakage current waveforms during the experimental studies were measured. Normally FFT method used to find the harmonic spectrum in the leakage currents. Three states of analysis are considered. In the first stage, it is done with nominal voltage and without arc. In the second state, it is done in presence of dry band arcing and corona discharge and in the last case, continues arc is investigated and in each stage harmonic analysis is performed. Eventually, to distinguishing of pollution intensity, ESDD calculations are implemented.

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


Keywords: Artificial aging, Leakage Current, polymer insulator, Solid layer pollution, ESDD.



go to top   Synchronous Distributed Partial Discharge Measurement System
         by M. Azizian Fard, Asghar Akbari, Reza Shojaee, M. A. Rasuli

           Vol. 5. n. 5, pp. 2478-2483


Abstract - Partial discharge measurement is a major diagnostics method of insulation systems in high voltage equipments, which makes it convenient to assess the insulation status and its prospective condition. Here the design of a distributed modular conventional system with the capability of synchronous operation is presented. The system relays on an FPGA in each module for preprocessing and controlling purposes, where the PD signals acquired by each module are preprocessed for the extraction of common PD features in order to avoid superfluous data. The extracted potential features are temporary stored in external memories and finally delivered to host computer via serial channel for further statistical and mathematical analysis.

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


Keywords: partial discharge, insulation, distributed, FPGA, synchronous.



go to top   Experimental Evaluation of Sliding Mode and EKF Observers for Network Delay Compensation in Bilateral Control
         by Seta Bogosyan, Bindu Gadamsetty, Metin Gokasan, Asif Sabanovic, Mustafa Unel

           Vol. 5. n. 5, pp. 2484-2493


Abstract - Network delays in the feedback and control loop can give rise to loss of transparency and instability in teleoperation and bilateral control systems, especially with the use of the internet as the medium of communication. This is a current problem of bilateral control, with numerous approaches taken to improve the performance in the face of network delay. This study is based on the more recent approach of taking communication delay effects into account as disturbance, and addressing the problem via the design of a disturbance observer. To this aim, a novel sliding-mode observer (SMO) and an EKF observer are developed and tested for improved performance in bilateral position control systems. The SMO runs on the master side and estimates the slave position using delayed measurement feedback from the slave side. The estimated feedback is used in a PD controller, also running on the master side, the output of which is sent to the slave through the internet as control input for trajectory tracking dynamics. As another contribution to bilateral control, in this study, an extended Kalman Filter (EKF) is also developed to estimate the variable load changes on the slave side, which are further compensated by a “plus” term added on the slave side to the PD control input sent by the master. The designed SM and EKF based bilateral control approach is tested with experiments conducted on a slave system comprising a single link arm under gravitational load. For added challenge, the system is tested for bi-directional load and reference trajectory variations and for both constant and random measurement and control input delays of 1-2 seconds in all cases. The experiment results demonstrate that the designed SM and EKF based observers perform very well under no control input delay, and well- known slave parameters and initial conditions. The developed system performs reasonably well with bi-directional load and reference variations under parameter uncertainties, and definitely maintains stability even under simultaneous random measurement and control delays of 1-2 seconds, which is considerably more than the considered delays in current literature.

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


Keywords: Bilateral Control, Communication Delay, Disturbance Observer, EKF, SM Control, Teleoperation, Load And Parameter Estimation.



go to top   Stepped Impedance Resonators in Triple Band Bandpass Filter Design for Wireless Communication Systems
         by Abdullah Eroglu

           Vol. 5. n. 5, pp. 2494-2499


Abstract - Triple band microstrip tri-section bandpass filter using stepped impedance resonators (SIRs) is designed, simulated, built, and measured using hair pin structure. The complete design procedure is given from analytical stage to implementation stage with details. The coupling between SIRs is investigated for the first time in detail by studying their effect on the filter characteristics including bandwidth, and attenuation to optimize the filter perfomance. The simulation of the filter is performed using method of moment based 2.5D planar electromagnetic simulator. The filter is then implemented on RO4003 material and measured. The simulation, and measured results are compared and found to be very close. The effect of coupling on the filter performance is then investigated using electromagnetic simulator. It is shown that the coupling effect between SIRs can be used as a design knob to obtain a bandpass filter with a better performance for the desired frequency band using the proposed filter topology. The results of this work can used in wireless communication systems where multiple frequency bands are needed.

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


Keywords: Bandpass, resonators, SIRs, microstrip, filter, communication, wireless.



go to top   Effect of Pulse Repetition Frequency on the Semiconductor Devices Burnout Caused by Microwave Pulses
         by Xi Chen, Zhengwei Du

           Vol. 5. n. 5, pp. 2500-2507


Abstract - Microwave pulses, one of the electromagnetic interferences, may cause permanent damage to semiconductor devices. Microwave pulses can be either single shot or repetitive. Pulse repetition frequency (PRF) is one of the most important parameters of repetitive pulses. Every semiconductor component burnout caused by microwave pulses has a threshold of PRF. Increasing the PRF can reduce the burnout peak power only when the PRF is above the threshold. To calculate the threshold, a theoretical model is proposed in this paper. The model is relatively general and can be applied to both transistors and p-i-n limiter diodes in common radio frequency front ends. Based on the model, an approximate formula is further proposed for quick estimation. The verification has shown that both the model and the approximate formula are competent to estimate the value of the threshold.

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


Keywords: burnout, high power electromagnetic, microwave pulse, pulse repetition frequency, semiconductor device.


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