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International Review of Electrical Engineering  Vol. 4 N. 6-- Part A

International Review of Electrical Engineering  Vol. 4 N. 6-- Part B


International Review of Electrical Engineering - December 2009 - Papers Part A



go to top     International Review of Electrical Engineering - December 2009 - Papers Part B






International Review of Electrical Engineering - Papers- Part A


go to top   Overview on Automotive Energy Storage Systems
         by V. Isastia, S. Meo

         Vol. 4. n. 6, pp. 1122-1144


Abstract - The hybrid electric and electric vehicles in the next future will be employed more and more. Many considerations induce to this solution: the efficiency of these vehicles, greater than the conventional ones, the major benefits that they offer in terms of environmental pollution, the increasing costs of the petroleum and its instable market. A key component of each electric and hybrid electric vehicle is the energy storage system. It plays a prominent role on the performances and on the overall drive efficiency of the vehicles, therefore for some years the study of this subsystem has recalled a strong interest among the scientists, the automakers and the manufacturers of energy storage systems. Recently, the main auto industries have found join-ventures with the manufacturers of batteries, supercapacitors and flywheels in order to study and to produce advanced energy storage systems for electric and hybrid electric cars and many innovations are introduced in this field (i.e. lead-carbon battery, bi-polar lead acid battery, thin film metal batttery, supercabattery and so on). All this attention justifies the aim of this paper is to illustrate a comprehensive state of the art on the main energy storage systems suitable for electric and hybrid electric vehicles, introducing also the most recent innovations on this important subsystem and the next goals to earn.

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Keywords: Automotive battery, Supercapacitor, Flywheel, Energy storage system.



go to top   Comparison of Different Control Strategies for Robust Shunt Active Power Filter
         by A. Ghasemi, S. S. Mortazavi

         Vol. 4. n. 6, pp. 1147-1155


Abstract - The increasing use of power electronic loads results in a considerable amount of harmonic injection, and lower power factor in electricity networks. To reduce harmonic distortion and improve the power factor, active power filters (APFs) have been developed. Conventional active power filters are designed for fixed load conditions, however, most of non-linear loads are not fixed and change randomly. This may result in insufficient compensation under load variation condition. This paper presents and compares new control strategies to improve dynamic response of active power filter under fast load variation condition. Different methods based on linear and non-linear scale controlling are studied under load variation condition in a comparative study. Simulation results show that proposed active power filter with ideal non-linear fuzzy logic scales has the best dynamic response while it is able to maintain total harmonic distortion (THD) percentage of source current well under IEEE-519 standard limits on harmonic levels.

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Keywords: Power quality improvement, Robust active power filter, Shunt active power filter, Fuzzy logic controller, Non-linear scale controlling.



go to top   Dual-Output LLC Resonant Converter with Series Connection in Primary Side and Parallel Connection in Secondary Side
         by Bor-Ren Lin, Po-Li Chen

         Vol. 4. n. 6, pp. 1156-1163


Abstract - A dual-output LLC resonant converter for LCD-TV applications is presented in this paper. Based on the LLC resonant behavior, the power MOSFETs are turned on at zero voltage switching (ZVS) and secondary rectifier diodes are turned off at zero current switching (ZCS). In the proposed converter, the primary windings of two transformers are connected in series so that the primary currents of two transformers are equal. In the secondary side of transformers, two full-wave rectifiers with dual-output configuration are connected in parallel to share the load current and to reduce the current stresses of the secondary windings of transformers. The principle of operation, steady state analysis and design consideration of the proposed converter are provided in detail. Experimental results based on a laboratory prototype with 12V/14A and -12V/14A outputs with 92.7% efficiency for LCD-TV applications were provided to verify the effectiveness of the proposed converter.

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Keywords: LLC resonant converter, ZVS, ZCS, LCD-TV.



go to top   Recent Advances in Multilevel Voltage Source Converters Based STATCOM Technology
         by Phee Kuan Jin, Mohamed S. A. Dahidah

       Vol. 4. n. 6, pp. 1164-1181


Abstract - There has been tremendous interest concerning extending the benefits of the self-commutated power electronic converters for reactive power compensation in the last few decades and different compensating topologies have been developed. One of the most effective and promising reactive power controllers is the static synchronous compensator (STATCOM). This paper presents a comprehensive review on recent advances in multilevel converter based STATCOM systems. The power quality issues, importance and the operation of the STATCOM on power transmission systems are briefly addressed. The paper focuses on the major development of significant components in the STATCOM system namely, STATCOM configuration, converter topologies, modulation techniques and control strategies. Existing conventional to novel discoveries are studied and reported.

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Keywords: Power quality, STATCOM systems, Multilevel converters, Modulation techniques, Control.



go to top   Analysis of a Cascade Boost-Flyback Converter with High Voltage Conversion Ratio
         by Bor-Ren Lin

    Vol. 4. n. 6, pp. 1182-1188


Abstract -  This paper presents the system analysis of a cascade boost-flyback converter with high voltage conversion ratio to overcome the limit of conventional boost or buck-boost converter with narrow turn-off period. The proposed converter has wide turn-off period compared with the conventional boost converter. Thus the higher output voltage in the proposed converter can be realized. The circuit configuration, principle operation, system analysis, and design consideration of the proposed converter are presented in detail. Finally, experiments conducted on a laboratory prototype rated at 200W were presented to verify the effectiveness of the converter.

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Keywords: Voltage step-up, Boost, Flyback.



go to top   Control of a Four Levels Inverter by a Programmed Matrix PWM based on EPROMS
         by Lazhar Manai, Faouzi Ben Ammar

          Vol. 4. n. 6, pp. 1189-1197


Abstract - The Multilevel imbricate cells inverter has attracting increasing attention in the paste few years for high power application. When high dynamic performances are desired this type of inverter is a good option but it requires extra control strategy. Conventionally control signals fed to the PWM inverters are produced by electronic hardware or microprocessor. The cost and complexity of hardware implementation are considerable. On-line computation in the microprocessor approach is laborious and time-consuming. These two approaches seem impractical when applied to PWM multilevel inverter control. An EPROM-based programmed PWM modulator can solve the problems mentioned above and provides an easy, fast and steady control for the multilevel inverters. Experimental results are carried out to confirm the high performance of the proposed embedded PWM modulation.

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Keywords: Multilevel inverter, Programmed matrix PWM, EPROM.



go to top   Design and Implementation of a Novel Vector-Controlled Drive by Direct Injection of Random Signal
         by Amin Zabihinejad, Javad. S. Moghani

         Vol. 4. n. 6, pp. 1198-1203


Abstract - The harmonic spectrum of an inverter output voltage in a PWM inverter can be distributed by using a Random Pulse Width Modulation (RPWM) scheme. RPWM dose not affect the fundamental frequency component of voltage, however it can significantly reduce the acoustic noise and mechanical vibrations of an inverter-fed ac motor drive. Up to now, RPWM has been studied in many researches and various RPWM techniques have been introduced, but none of them have actually shown the effects of the behavior of the random signal on the frequency spectrum of the inverter output voltage and performance of the motor drive. In this paper, three different methods of random signals are employed. These different methods and the Probability Density Function (PDF) of the random signal generator will be studied and the performance of the drive is examined. Also a new method in utilizing random signal is proposed. In this method, the random signal is injected to reference value of the quadrature-axis current. It should be noted that the RPWM technique can not be utilized in hysterisis drives. Here, the random signal with different PDF is injected directly to quadrature axis current. The injection of random signal will directly affect the output responses. In this research, comparison between RSPWM technique and direct injection of random signal has been carried out. Different criteria such as total harmonic distortion (THD), torque ripple and frequency spectrum, efficiency and mechanical vibration have been analyzed. The indirect field oriented vector control drive is simulated by using Matlab-Simulink first, and the effects of various methods of employing random signal are compared and the best alternative is introduced. For the validation of the simulation results an experimental set-up is built. The experimental results confirm the simulation outputs. The simulation and experimental result show superiority of Direct Injection of Random Signal (DIRS) method in comparison with RSPWM technique. Also it is realized that the DIRS method is very simple for implementation and does not need any extra hardware.

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Keywords: FFT, Field oriented control, Harmonic components, RSPWM, Spectrum.



go to top   Application of Virtual Flux-Direct Power Control for VSC Based HVDC Systems
         by Ebrahim Abiri, Farzan Rashidi

         Vol. 4. n. 6, pp. 1204-1209


Abstract - In this paper direct power control (DPC) of three-phase space vector modulation (SVM) in the rectifier and the inverter sections of a VSC based HVDC system without any voltage line sensors are discussed. Use of the direct power control (DPC) and new synchronous double reference frame phase-locked loop (SDRF-PLL) approach, the control system is resistant to the majority of line voltage disturbances. The operation of this control strategy is verified in SIMULINK/MATLAB simulation environment. It is shown that the proposed control system is also effective to damp system oscillations and enhance power quality when power flow is reversed. To validate this control system, a 5kVA prototype system was constructed. All of the test results have shown the good agreement between simulation and experimental results.

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Keywords: VSC based HVDC, SVM, DPC, SDRF-PLL.



go to top   Performance Improvement of Linear Permanent-Magnet Synchronous Motor with Halbach Array
         by Nariman Roshandel Tavana, Abbas Shoulaie

      Vol. 4. n. 6, pp. 1210-1214


Abstract - In this paper, a detailed analytical modeling based on Maxwell equations is presented for analysis and design of permanent-magnet linear synchronous motor with Halbach array. In order to mitigate thrust ripple, the main design parameters of the analyzed machine are optimized by using genetic algorithm in an appropriate objective function. The results show an enhancement in the motor performance. Finally, we have used 2-D nonlinear time-stepping transient finite-element method to demonstrate validity of the analytical analysis and design optimization.

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Keywords: Permanent-magnet linear synchronous motor with Halbach array, Finite-element method, Analytical model, Optimization, Genetic algorithm.



go to top   General Formulas and Detailed Model of Broken Bar 3-Phase Induction Motor Considering Skew Effect and Linear
MMF Rise across the Slots

         by Mohammad Ali Faturachi, Khalil Banan Aliabbasi, Mohammad Bagher Bannae Sharifian

      Vol. 4. n. 6, pp. 1215-1222


Abstract - A new detailed model of 3-ph squirrel cage induction motor based on modified winding function theory is presented in this paper. Slotting, skewing and linear MMF rise across the rotor and stator slots are considered in the model. The state space equations in terms of flux linkages as well as motor currents, and a more general form of nonlinear state space equation are obtained. Three methods for calculating mutual inductance matrix between stator and rotor, and two schemes for incorporating rotor faults into the model are discussed. Also general formulas for rotor inductance calculation in healthy and broken bar motor are proposed. Simulation results of healthy and broken bar motors show the ability of the model.

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Keywords: Induction motor, Modeling, Winding function, Broken bar, Skew effect, MMF.



go to top   Dynamic Model for Brushless Doubly-Fed Machine with Stator Winding Faults

         by Hamed Gorgin, Pedram Sotoodeh, Hashem Oraee

     Vol. 4. n. 6, pp. 1223-1230


Abstract - In this paper, a detailed analytical model for dynamic analysis of the Brushless Doubly-Fed Machine is presented. The model is capable to predict the machine behavior under different modes of operation including: simple induction mode, cascade mode and synchronous mode, both with and without winding faults and unbalanced excitations. The proposed approach employs the basic principles of the generalized harmonic theory for calculating self inductances and mutual inductances of circuits with any distribution of conductors. Dynamic equations of modified coupled-circuit method are then solved to compute the currents flowing in the stator windings and rotor loops.

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Keywords: Brushless Doubly-Fed Machine (BDFM), Nested loop rotor, Generalized harmonic analysis, Space harmonic.



go to top   Optimal Sizing, Economic Analysis and Dynamic Behaviour of an Isolated Integrated Wind Turbine, Microturbine, and Battery Storage
         by S. M. Mousavi G., M. Kalantar

     Vol. 4. n. 6, pp. 1231-1242


Abstract - In this paper, dynamic modelling, simulation and synthetic operation of adaptive control, supervisory control and space vector control are considered in a stand-alone hybrid power generation system of wind turbine, microturbine and battery storage. Due to efficient and economical utilisation of the renewable energy resources, optimal sizing of the hybrid system is fulfilled based on economic analysis using genetic algorithms. For extraction of maximum energy from a variable speed wind turbine, a developed Lyapunov model reference adaptive feedback linearisation method accompanied by an indirect space vector control is applied. Because of more reliability, more fuel flexibility, less environmental pollution, less noise generation and less power fluctuation in comparison with a diesel generator, a hydrogen based microturbine integrated with battery storage is suggested as a back up for this system.

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Keywords: Optimal sizing, Wind turbine, Microturbine, Battery storage, Adaptive control, Supervisory control.



go to top   A High-Level Environment for FPGA Neural Network Implementation
         by C. Benbouchama, M. Tadjine, A. Bouridane

     Vol. 4. n. 6, pp. 1243-1247


Abstract - This work aims at the realization of a high-level environment to facilitate and accelerate the neural network implementation on FPGAs. A parameterizable tool was designed to generate a neural multi-layer network implementation through the use of Handel-C language. The algorithm used for the training is the back-propagation. The tools of implementation and synthesis are the DK of Celoxica and the ISE of Xilinx. The targeted components are XCV2000 on Celoxica RC1000 board and XC2V1000 on RC200. Experimental evaluations are presented to demonstrate the validity of the design.

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Keywords: Neural networks, FPGA, Parameterizable implementation, Handel-C.



go to top   Improved Dynamic Average Modeling of Synchronous Machine with Diode-Rectified Output
         by M. Shahnazari, A. Vahedi

     Vol. 4. n. 6, pp. 1248-1258


Abstract - This paper presents an improved dynamic average model for synchronous machine-rectifier system. The dc load current is modeled using its first-order Taylor series expansion throughout the complete averaging period. The behavior of the machine-converter in different rectification modes is expressed by mathematical equations makes it suitable for analysis of variable frequency systems. The paper expresses an in-depth description of the modeling approach, together with a transient validation of the proposed model. The model is validated through comparison of average model in MATLAB and the experimental results.

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Keywords: Synchronous Machine, Dynamic Average Modeling, Generator-rectifier.



go to top   Experimental Evaluation of Novel High Order Sliding Mode Controllers for High Performance Direct Drive Systems

         by Aydemir Arisoy, Seta Bogosyan, Metin Gokasan

     Vol. 4. n. 6, pp. 1259-1272


Abstract - The high speed, high accuracy control of DD systems requires the full system dynamic effects to be taken into account in the control design, due to the eliminated gear mechanism, and hence, the increased effect of structured or unstructured uncertainties between the motor and load. The actuator dynamics and structural flexibilities become of increased importance particularly when high speed, high accuracy operation of lightweight DD structures is aimed. However, most related studies on DD robots neglect these effects concentrating only on link dynamics; hence compromising the tracking accuracy in the transient and steady state. On the other hand, the actuator dynamics and/or torque ripple is taken into consideration only in relation to the high performance control of DD motors. This paper aims for the high accuracy, high speed control of direct-drive (DD) robotics systems via novel robust high-order sliding mode controllers (HOSMCs) of 2nd order (2-HOSMC), and 3rd (3-HOSMC), designed and experimentally tested on a single link arm under uncertain gravity effects. Two novel 3-HOSMCs are designed, both with the simultaneous consideration of the actuator dynamics, torque ripple, and structural flexibilities to address the above mentioned problems with DD systems. This is one of the contributions of the paper to existing literature, where HOSMCs are derived by artificially increasing the system order, creating additional needs for integration. To avoid the excitement of internal dynamics and to increase accuracy, one of the HOSMCs is also designed and tested with continuous input, which is another contribution of the study. The performances of the novel HOSMCs are tested experimentally on a hardware-in-the-loop (HIL) simulator test-bed, developed for a 1 degree-of-freedom (DOF) direct-drive (DD) flexible link arm (FLA). The experiments performed under load variations and external disturbances reveal the superiority of the designed new 3-HOSMCs, especially that of the continuous input HOSMC, in terms of improved tracking accuracy and reduced torque ripple effects, motivating the use of such controllers for demanding high performance control applications under heavy uncertainties.

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Keywords: High order sliding mode controllers (HOSMCs), 2-HOSMC, 3-HOSMC, Direct drive systems, Flexible-link robotic arm, Structural flexibilities, Actuator dynamics, Torque ripple minimization, Hardware-in-the-loop (HIL) simulators.



go to top   Comparative Analysis of Control Strategies for DFIG Based Wind System under Small Grid Faults
         by S. Skander-Mustapha, M. Jebali-Ben Ghorbal, J. Arbi, I. Slama-Belkhodja

    Vol. 4. n. 6, pp. 1273-1282


Abstract - In this paper, the authors investigate the evaluation of FOC, DTC and DPC strategies applied to a Variable Speed Wind System (VSWS) based on a DFIG. A comparative analysis of the three controls is performed, in healthy and faulty grid conditions: balanced and unbalanced small voltage dips and grid frequency disturbances. The study emphasizes the limitations introduced by the approximations usually assumed to simplify the design of these control strategies. The influence of these hypotheses is analysed through of the specific wind turbine quantities like generated active and reactive power, electromagnetic torque and currents. Simulation results are provided to illustrate the effectiveness of the approach.

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Keywords: Variable Speed Wind System, Doubly Fed Induction Generator, Field Oriented Control, Direct Torque Control, Direct Power Control, Grid fault.



go to top   Effects of Skewing on Torque Ripples for Brushless Doubly-Fed Machine
         by Hamed Gorgin, Pedram Sotoodeh, Hashem Oraee

    Vol. 4. n. 6, pp. 1283-1293


Abstract - In this paper, analytical expressions are presented to describe the stator and rotor slotting effects on the distribution of Brushless Doubly-Fed Machine’s quantities. The effects of rotor slot and loop skewing on the produced torque ripples are then investigated by means of an analytical model considering skew. Torque ripples have considerable effects in the machine operation especially on its starting process and avoid machine from successful starting in some instances. The cogging torque and distortion of the sinusoidal distribution of the magnetic flux density in the air gap, are two principle sources of torque ripples in Brushless Doubly-Fed Machine that are studied.

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Keywords: BDFM, Skew Effect, Wind Turbine.



go to top   Intelligent Active Force Control with Piezoelectric Actuators to Reduce Friction Induced Vibration Due to Negative Damping
         by S. M. Hashemi-Dehkordi, M. Mailah, A. R. Abu Bakar

    Vol. 4. n. 6, pp. 1294-1305


Abstract - In this paper, a novel approach to reduce the effect of negative damping that causes friction induced vibration (FIV) is proposed by applying an intelligent active force control (AFC)-based strategy employing piezoelectric actuators with hysteresis effect to a simplified two degree-of-freedom mathematical model of a friction induced vibration system. At first, the model is simulated and analyzed using a closed loop pure proportional-integral-derivative (PID) controller. Later, it is integrated with the intelligent AFC with fuzzy logic (FL) estimator and simulated under similar operating condition. After running several tests with different sets of operating and loading conditions, the results both in time and frequency domains show that the PID controller with the intelligent AFC is much more effective in reducing the vibration, compared to the pure PID controller alone.

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Keywords: Friction Induced Vibration, Negative Damping, Active Force Control, Fuzzy Logic Estimator, Piezoelectric Actuators.



International Review of Electrical Engineering - Papers- Part B



go to top   A Policy-Driven Method for IT Infrastructure Selection in Power Distribution Automation System

         by A. Fereidunian, C. Lucas, H. Lesani, R. Rahmani, A. W. Wymore

    Vol. 4. n. 6, pp. 1306-1317


Abstract - Electric power utilities invest heavily on their IT infrastructures; however, a large number of IT development projects fail. These failures are mostly caused by unsystematic and ad hoc designs, which can be summarized as lack of consistent design decision methods. This consistent design decision method should include a well-aligned IT development plan, considering requirements of the needed system. The literature shows the positive effect of this alignment of the IT requirements with the utility corporate policy, referred to as being Policy-Driven, here.
This paper proposes a Policy-Driven design decision method for electric utility IT development projects, based on Wymorian T3SD theory of systems design. The proposed method possesses the following two features. First, it is highly sensitive to corporate policy of the utility, as our proposed method is able to assure the alignment of the IT development to utility corporate policy. Second, the proposed method is able to deal with the multiple disciplines related to the utility business; which includes at least: the utility core technology (power and automation), IT, human resources and financial matters.

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Keywords: Policy-driven decision making, Power distribution systems, IT infrastructure, Utility Management Automation (UMA), Distribution Automation (DA), Architectural design, Multi-Criteria Decision-Making (MCDM).



go to top   An Efficient Hybrid Evolutionary Optimization Algorithm for Multi-Objective Distribution Feeder Reconfiguration
         by Reza Khorshidi

    Vol. 4. n. 6, pp. 1318-1325


Abstract - This paper presents a new hybrid evolutionary algorithm based on Particle Swarm Optimization (PSO) and Simulated Annealing (SA), called PSO-SA, for multi-objective Distribution Feeder Reconfiguration (DFR). The objective functions are to minimize real power losses; deviation of nodes voltage; the number of switching operation and to balance the loads on the feeders. Due to the objectives are different and no commensurable, it is difficult to solve this problem by conventional approaches that optimize a single objective. In the proposed algorithm, these objective functions are first modeled with fuzzy sets to evaluate their imprecise nature and then the hybrid PSO-SA is used to determine the optimal solution. The feasibility of the proposed optimization algorithm is demonstrated and compared with the solutions obtained by other approaches over different distribution test systems.

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Keywords: Ant Colony Optimization (ACO), Distributed Generators, Particle Swarm Optimization (PSO) Voltage and Reactive Power Control.



go to top   Optimal Allocation of Multi-Type FACTS Devices to Improve Security and Reduce the Losses and Fault Level using Multi-Objective Particle Swarm Optimization
         by H. R. Baghaee, M. Mirsalim, A. Kashefi-Kaviani, G. B. Gharehpetian

    Vol. 4. n. 6, pp. 1326-1335


Abstract - Flexible alternative current transmission system devices can regulate the active and reactive power as well as voltage-magnitude. Placement of these devices in suitable locations can lead to the control of line power flow, bus voltages and short circuit currents at desired levels and as a result, improvement of power system security margins.
This paper presents an optimal allocation algorithm for FACTS devices based on a novel m-objective particle swarm optimization method considering both power system costs and security. The proposed algorithm has successfully been applied to an IEEE 30-bus power system and the results are presented and discussed.

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Keywords: Power System Security, Transmission Systems, FACTS Devices, Multi-Objective Particle Swarm Optimization.



go to top   Evaluation of Different Options for SSSC-Based Stabilizer to Improve Damping Inter-Area Oscillations in A Multi-Machine
Power System

         by M. R. Shakarami, A. Kazemi

    Vol. 4. n. 6, pp. 1336-1346


Abstract - In the static synchronous series compensator (SSSC) a controllable AC voltage is generated by a voltage-source converter. There are two control channels for controlling of magnitude and phase of the voltage. If the purpose of SSSC is damping inter-area oscillations in multi-machine power systems, damping stabilizer can be included in the both channels. In steady state condition, the magnitude of the voltage can be controlled by two methods, namely constant voltage mode and constant reactance mode. A damping stabilizer can be included in the both modes of magnitude controller. In this paper, effect of line compensation by SSSC in the constant voltage and constant reactance mode on damping inter-area oscillations in a two–area multi-machine power system is investigated. To design a SSSC-based stabilizer a method using quadratic mathematical programming has been proposed. In this method gain and phase of stabilizer are simultaneously calculated. Four options for using SSSC-based stabilizer to damp mechanical oscillations are presented. The obtained results on the two multi-machine power systems show that usage of SSSC stabilizer in the suitable option can significantly reduce the control cost of the stabilizer.

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Keywords: Damping stabilizer, Inter-area oscillations, SSSC, Quadratic mathematic programming.



go to top   Simultaneous Clearing of Wind-Thermal Generation and Reserve Market with Interruptible Load Participation
         by A. Zakariazadeh, S. Jadid

    Vol. 4. n. 6, pp. 1347-1356


Abstract - This paper focuses on the development of a model for Interruptible Load (IL) procurements within the operating reserve where significant wind power capacity is available through the grid. In this paper a stochastic mixed-integer linear programming model is utilized. This model considers the network constraints and takes into consideration the cost of both expected load not served and two kinds of reserves. Both spinning reserve and interruptible load are taken into account as the reserve services. The characteristics of the procurement of interruptible load such as locational aspect of the IL, maximum interrupted time and minimum connected time, different offer in each IL’s agent, maximum and minimum IL’s quantity participation are explicitly considered. The main purpose of this paper is to determine a sufficient amount of spinning reserve in a power system with a high penetration of wind power that considers the accidental disturbances such as outages of generating units and transmission lines and errors in the forecasts of wind power production, simultaneously. These uncertainties are modeled as credible scenarios. The proposed approach is tested on the modified IEEE-RTS for 24 hours.

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Keywords: Expected load not served (ELNS), Interruptible Loads (ILs), Mixed-integer linear programming (MILP), Spinning reserve, Stochastic optimization, Transmission limits, Wind power generation.



go to top   The Effect of the Zero Sequence Component on the Evaluation of the Series APF Apparent Power
         by A. Kouzou, M. O. Mahmoudi, M. S. Boucherit

    Vol. 4. n. 6, pp. 1357-1366


Abstract - The main purpose of this paper is the study of the effect of the zero sequence components in the evaluation of the apparent power, which is intended to be used in the evaluation of the performance and the process design of the Series Active Power Filter (SAPF). The capability of the SAPF is determined by the maximum rate of the apparent power that can be delivered. This leads to the evaluation of the apparent power rate required to achieve the needed compensations under different perturbations. This study is based on the definition of the effective apparent power as it was defined by three different approaches such as the IEEE approach; the European approach and the theoretical approach. Those approaches were proved to be the most correct methods concerned in the design process of different devices. They allow a good estimation of the SAPF dimensions with low economic burden. This paper is concluded by the representation of general cases of perturbations in three phase AC power system.

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Keywords: Series Active Power filter, Apparent power, Equivalent voltage, Equivalent current.



go to top   Development of State Space Model and Control of the STATCOM for Improvement of Damping in a Single-Machine Infinite-Bus
         by Ghazanfar Shahgholian

    Vol. 4. n. 6, pp. 1367-1375


Abstract - – This paper is used to investigate a novel design of PID controller for a single-machine infinite-bus (SMIB) power system installed with the STATCOM. A simplified analytic approach is proposed. The SMIB has a multi-input multi-output (MIMO) structure and the use of two-port and state space models is a good approach for modeling and control. The effectiveness of speed and feedback control loops in providing damping was investigated for the linearized model. The simulation results are show ability of the STATCOM to damp system oscillation under changes in operation in the system, location of STATCOM and different combinations of PID controller.

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Keywords: Static synchronous compensator (STATCOM), PID controller, State space analysis.



go to top   Effects of STATCOM, TCSC, SSSC and UPFC on Static Voltage Stability
         by Mehrdad Ahmadi Kamarposhti, Mostafa Alinezhad

  Vol. 4. n. 6, pp. 1376-1384


Abstract - The purpose of this paper is to study the effects of four FACTS controllers: STATCOM, TCSC, SSSC and UPFC on static voltage stability in power systems. Continuation power flow is used to evaluate the effects of these devices on system loadability. Applying saddle node bifurcation theory with the use of PSAT, effects of these devices controllers on Maximum Loading Point are determined. Static voltage stability margin enhancement using STATCOM, TCSC, SSSC and UPFC is compared in the modified IEEE 14-bus test system.

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Keywords: Voltage collapse, Static voltage stability, STATCOM, TCSC, SSSC, UPFC.



go to top   New Fault Location Technique for Series Compensated Transmission Lines
         by Ning Kang, Yuan Liao

  Vol. 4. n. 6, pp. 1385-1390


Abstract - A new fault location algorithm for series compensated transmission line utilizing two-terminal unsynchronized voltage and current measurements is presented in this paper. The distributed parameter line model is adopted to fully take into account the shunt capacitance. The fault impedance is assumed to be pure resistive. By formulating the fault current in terms of unknown fault location, boundary conditions under different fault types can be made use of to derive the fault location. Two subroutines assuming the fault occurs on the left or right side of the series compensator are developed and the principle to identify the correct fault location estimate is described. Matlab SimPowerSystems is utilized to simulate the faults of various conditions and generate the voltage and current waveforms from both terminals of the series compensated single-circuit line. The fault location results are quite accurate based on simulation studies.

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Keywords:  Fault location, Series compensation, Single-circuit transmission lLine, Two-terminal, Unsynchronized voltage and current phasors.



go to top   Steady State Model of STATCOM and SSSC Using Averaging Technique

         by S. Rahimzadeh, M. Tavakoli Bina, A. Houshmand Viki

  Vol. 4. n. 6, pp. 1391-1403


Abstract - The application of FACTS devices in operating power systems has been growing. However, achieving the full advantages of these devices is severely dependent on their type, size, number and their location. Furthermore, their optimal size and placement are affected by their steady state models applied in power system studies. But the use of exact model of FACTS devices in steady state calculations is complex, due to their switching behavior. On the other hand, applying very simple models such as pure inductor/capacitor for FACTS devices leads to inaccurate results. In addition, in a power market the use of inaccurate models for power system components affects the electrical energy pricing system; while this is very crucial when FACTS devices are used for congestion management of the transmission systems. Average technique provides an appropriate time-domain representation of FACTS devices in which high frequency switching ripples are vanished. But average model can not be directly applied to the power system steady states. Thus this paper extends average models and presents average-neural (AN) models of STATCOM and SSSC as parallel and series FACTS devices, which are well-suited for analytical purposes in power system applications. To this extend, design and development of four neural identifiers are performed using the GAMMA, DNN, RBF and MLP. To verify the developed models, the exact solutions obtained from the average models of STATCOM and SSSC are compared with the outcomes of the identifiers. To show the accuracy of using the AN model, an optimal placement problem of STATCOM is solved by applying the AN model and then the results are compared to those reported in literature.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Averaging technique, FACTS devices, Modeling, Neural network.



go to top   Significance of Measurement and Analysis of Partial Discharges of Low Magnitudes

         by J. Sundara Rajan, Michael G. Danikas

  Vol. 4. n. 6, pp. 1404-1412


Abstract - The problem of insulation damage due to partial discharges of low magnitudes has not yet attracted much attention. Indications of possible damage and long term effects of accumulated partial discharges of low magnitudes are evident from published literature. In this paper, the possibility of existence of such phenomena is investigated with different insulation systems namely small air gaps under point-plane electrode arrangement, gas-gap in a coaxial geometry consisting of a 10:90 gas mixture of SF6 and N2 gases and paper-oil insulation of a power transformer. It is observed that random discharges below inception voltage do exist. Such discharges are studied and their impact on insulation is discussed. Experimental evidence is offered to substantiate that discharges change from the pulse-type to a pulse less-type as the gap becomes larger in case of air. Phenomena of PD below or in the vicinity of inception voltages may help in better understanding of the mechanism of small current flow at relatively low voltages and may help in development of better dielectric materials and insulation systems for high voltage applications.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Partial Discharge, Inception voltage, Statistical PD parameters, Paper-oil insulation, SF6-N2 gas mixture, Air.



go to top   The Electroquasistatic Field Simulation and Analysis for the Insulation Defects in XLPE Power Cables
         by Canxin Guo, Chengjun Huang, Yong Qian, Junhua Liu, Xiuchen Jiang

  Vol. 4. n. 6, pp. 1413-1417


Abstract - The insulation defect is one of the main problems challenges the widely used cross-linked polyethylene (XLPE) power cables. To study the effect of defects on the insulation performance, some typical insulation defects are modeled and analyzed, including needle penetrating into insulation and void in insulation. To simulate more precisely, the electroquasistatic solver equations are utilized. Then, the electric field and potential distribution inside the cable are obtained. It is found that the electric field is distorted by different type of insulation defects. Any air gap or void appeared in insulation tends to failure because their low breakdown strength compared to XLPE. Experiments are carried out to validate the simulation and show that the simulation has a good approximation to the real operation status.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: XLPE Power cables, Electroquasistatic field, Simulation, Insulation defects, Void.



go to top   A Novel Algorithm for Internal Impedance Computation of Solid and Tubular Cylindrical Conductors
         by S. Vujević, V. Boras, P. Sarajčev

  Vol. 4. n. 6, pp. 1418-1425


Abstract - Computation of the internal impedance per unit length of solid and tubular cylindrical conductors, energized by time-harmonic current, needs to take into account the skin effect. Computation algorithm often involves direct numerical manipulations with Bessel functions, which yields unstable and often erroneous results for large magnitudes of the function argument at high frequencies. In order to alleviate the afore mentioned problem, this paper presents a novel computational algorithm based on the Hankel asymptotic approximations of the Bessel functions for large magnitudes of the arguments. Proposed approximate formulas assure numerical stability and very high accuracy of the numerical solution, even in case of very large function arguments. They are, at the same time, very convenient for the numerical implementation in any high level programming language.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Internal impedance, Cylindrical conductor, Skin effect, Approximate formula, Bessel functions, Hankel asymptotic approximation, Large parameters.



go to top   Current Mode Tow-Thomas Biquadratic Differential Class AB Log Domain Filter
         by Abdullah T. Tola, Remzi Arslanalp, Saziye Surav Yilmaz

  Vol. 4. n. 6, pp. 1426-1432


Abstract - In this study, a current-mode Class AB differential type Tow-Thomas filter has been synthesized in the log domain by using the state space method and by adopting translinear circuits. Varying the values of the current sources of the circuit, the pole frequency of the filter as well as the quality factor and DC gain of the circuit can be tuned electronically. The circuit was simulated in PSpice for both idealized transistor models and CBIC-R type transistors. We are able to tune the pole frequency between 50 kHz and 5 MHz, precisely two decades, and we can easily set the quality factor of circuits electronically to various values between 0.5 and 7. In this work, a high dynamic range is achieved within 4 decade change in Ipeak/Ibias . The proposed circuit has unity gain and independent of Q quality factor for the band pass filter response. All simulation results are verified by THD analysis. Our results show that the measured total harmonic distortions under the %2. We also performed noise analysis. Various simulations results are presented to show the effectiveness of the proposed circuit.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Current Mode circuits, Differential Class AB, Log domain filters, Tow Thomas.



go to top   Insulator Leakage Current Studies in Artificial Climatic Chambers using Dimensional Analysis
         by N. Bashir, H. Ahmad

  Vol. 4. n. 6, pp. 1433-1439


Abstract - The study of insulator leakage current in the laboratory to simulate the outdoor conditions for insulator flashover and ageing studies has been conducted for decades; however, development of mathematical relationships of the insulator leakage current with factors that strongly affect its behavior outdoor viz. environmental factors and contamination severity has not been attempted. This paper describes the use of mathematical modelling based on dimensional analysis technique in investigating and predicting the behavior of insulator leakage current (LC). The magnitudes of insulator leakage current from the developed model are calculated using different contamination levels, electrical stresses and varying atmospheric conditions. These predicted results are compared with results obtained from experiments carried out to measure the leakage current magnitude in an artificial climatic chamber at same conditions. The predicted results from the model are found to be in good agreement with experimental results.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords:  Dimensional analysis, Leakage Current, Insulator.



go to top   Reliability Assessment of Protective Schemes Considering Time Varying Rates
         by Carlos J. Zapata, Daniel S. Kirschen, Mario A. Rios, Alvaro Torres

  Vol. 4. n. 6, pp. 1440-1446


Abstract - Reliability assessments of protective schemes have been traditionally performed considering constant event rates. As a consequence, situations of improvement and deterioration on protective components reliability and maintenance performance are not considered. As these situations do happen in real life, this paper presents a method which allows considering time varying rates and diverse strategies of maintenance. It combines the modeling of failure and repair processes using stochastic point process theory and a procedure of sequential Monte Carlo to artificially generate the operating sequence of the protective system and for computing its reliability indexes. However, as it is shown in the example, this great improvement in the modeling detail of these kinds of studies has a price; it is the long computational time required by the simulation.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Aging, Monte Carlo Simulation, Power System Reliability, Protective Relaying, Stochastic Point Processes.



go to top   Low Power Flash A/D Converter with TIQ Comparators for Multi-Standard Mobile Applications
         by Jaehyun Lim, Insoo Kim, Nguyen Minh Son, Jincheol Yoo, Jongsoo Kim, Kyusun Choi

  Vol. 4. n. 6, pp. 1447-1452


Abstract - The need for high speed A/D converters has increased in numerous areas such as multi-standard mobile devices and real-time data acquisition applications. The flash type A/D converter, known for its fast data conversion rate, has not been popular with these applications because of its high power consumption. Unlike typical flash type A/D converters, the Threshold Inverter Quantization (TIQ) technique enables low power consumption as well as high speed data conversion. Two power management methods, sampling frequency scaling and frequency adaptive power management, are proposed for low power TIQ A/D converters in multiple frequency band applications. Both methods apply power switching and clock gating techniques. Power consumption of the TIQ A/D converter can be reduced efficiently by the proposed methods. Average power consumption in the ADC was reduced by 44 % to 99 % between the frequency ranges of 52 kHz to 161.3 MHz. The results show that the TIQ A/D converter can be used in SOC designs for multi standard mobile devices with reasonable power consumption. The proposed designs are implemented and fabricated in 0.18µm CMOS technology.

Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved


Keywords: Analog-Digital Converter (ADC), Flash type ADC, Low power ADC, TIQ ADC.



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