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International Review of Electrical Engineering Vol. 6 N. 3-- Part A

International Review of Electrical Engineering Vol. 6 N. 3-- Part B

International Review of Electrical Engineering - June 2011 (Vol. 6 N. 3) - Papers Part A

	A New ZVS-CV Bridgeless PFC Dual Boost Converter for Pure Electric Vehicle Battery Charger Modified SHEPWM Switching Strategy for Multilevel Inverters Negative-Output Soft Switched KY Buck Converter Design of a Hybrid Power Fed-Converter and Time Controller for LED Traffic Light Systems Line Voltage THD calculation of Cascaded Multilevel Inverter's Stepped Waveform with Equal DC Sources Reliability Estimation of Uninterruptible Power Supply Using Reliability Block Diagram Method Fuzzy Logic Controlled Three-phase Three-wired Shunt Active Power Filter for Power Quality Improvement Two Types of High Step-Up DC-DC Converters Based on Charge Pump and Coupling Inductor High Voltage Ratio Interleaved Boost DC-DC Converter for High Power Fuel Cell Application 1-MHz High Frequency Resonant AC Power Supply System Multi-Output Isolated DC-DC Converter with Cross Regulation Taking into Account Load Transient Torque Ripple Reduction in Direct-Driven Permanent Magnet Wind Generators Using Particle Swarm Optimization Algorithm for Transformer Transient Study Measurement and Mathematical Fitting of Partial Discharge Pulse Burst in Transformer Oils Investigating the Effects of I-Shaped Cores in an Outer-Rotor Transverse Flux Permanent Magnet Generator Application of Duffing Oscillators to Dynamic Eccentricity Fault Detection in Squirrel Cage Induction Motors Direct Torque Control of Induction Motor in Field Weakening Without Outer Flux Trajectory Reference Stabilizing Method of Speed Adaptive Flux Observer for Speed Sensorless Induction Motor Drives Optimization Algorithm for Improvement Insulation System in HV Generator Based MultiphysicsAnalysis Using FEM Analytical Calculation of the Flux Distribution and Demagnetization in Spoke Interior Permanent-Magnet Machines With Non-Magnetic Shaft A Novel DTC-ISVM for Induction Motor Drive System Fed by Indirect Matrix Converter Using 3-Level Voltage of DC-Link and ALM Estimator to Correct the Stator Resistance Hilbert Transform-Based Bearing Failure Detection in DFIG-Based Wind Turbines Investigation of Electromagnetics Characteristics in External Rotor SRM Under Dynamic Eccentricity Fault Extended PNGV Battery Model for Electric and Hybrid Vehicles A Novel GA Based Technique for Optimizing Both the Design and Control Parameters in Parallel Passenger Hybrid Cars
International Review of Electrical Engineering - June 2011 (Vol. 6 N. 3) - Papers Part B
	Critical Study of Underfrequency Load Shedding Schemes Optimal Unit Sizing of Distributed Energy Resources in MicroGrid Based on Mixed-Integer Bacterial Foraging Algorithm Coordinated Design of STATCOM-Based Damping Controller and Dual-Input PSS to Improve Transient Stability of Power System Optimal Bifurcation Control Approach for Small-signal Stability Control of Power Systems Using Clonal Selection Algorithm for Sitting and Sizing of Distributed Generation in Distribution Network to Improve Voltage Profile and Reduce THD and Losses Optimal PMUs Placement for Power System ObservabilityUsing Grenade Explosion Algorithm A New Preconditioner Design Based on Spectral Division for Power Flow Analysis Optimal Placement of Switching Devices in Power Distribution Networks Using the Switch-Position-Exchange Technique Optimal Network Reconfiguration for Voltage Sag Mitigation in Distribution Systems Using Improved Genetic Algorithm Solution of Multi-Objective Optimal Power Flow with Chaotic Artificial Bee Colony Algorithm A Novel Method to Anti-Islanding in Grid Connected Distributed Generators A method for the sag-tension calculation in electrical overhead lines Optimal Distributed Generation Placement Using Hybrid Genetic-Particle Swarm Optimization Hybrid Railway Power Quality Conditioner for Autotransformer-Fed AC Electrified Railway Systems Power Quality Management Platform for Smart Grid Proposing a Market based Approach for Restoration of Power Systems Locating and Sizing Static Synchronous Series Compensator Using Fuzzy-Genetic Algorithm A Genetic Algorithm to Minimize the Periodic Preventive Maintenance Cost in Electrical System Improving Congestion Relief Management as Ancillary Service in Operation Planning Phase with Demand Side’s Presence Finding Nash Equilibrium Point for Optimal Bidding in PAB Electricity Markets based on PSO Algorithm A Primal-Dual Interior Point Method for Solving Environmental/Economic Power Dispatch Problem Universal Characteristics of Faults in Complex Power System The Effect of Repairs on the Occurrence of High Order Failure Scenarios in a Bulk Power Transmission System Neural Inverse Control of Wind Energy Conversion Systems Implementation of Particle Swarm Optimization Based Maximum Power Point Tracking of Solar Photovoltaic Array under Non Uniform Insolation Conditions Development of Three-Phase Grid-Interactive Inverter for a 70-kW Microturbine-Based Distributed Generation

International Review of Electrical Engineering - Papers- Part A

A New ZVS-CV Bridgeless PFC Dual Boost Converter for Pure Electric Vehicle Battery Charger
by V. Isastia, S. Meo

Vol. 6. n. 3, pp. 1060-1069

DOI: http://dx.doi.org/10.15866/iree.v6i3.8482

Abstract - In the next future pure electric vehicles will be more and more adopted as the unique viable city-car solution. The battery charger is a fundamental component for this type of vehicle. Generally it is composed by a front-end ac–dc power factor corrected converter and a dc-dc isolated converter. The front-end ac–dc converter is a key component of the charger system. High efficiency, low cost, low encumbrance and high reliability are the main requirements for such type of device. In addition to the front-end ac-dc converter is required to meet strictly the EN 61000-3-2 standard as high power factor correction (PFC) and adequate amplitudes of the main harmonics. In the paper a new zero-voltage switching clamped-voltage bridgeless PFC dual boost converter for pure electric vehicle battery charger is proposed. The soft-switching capability is achieved adding a simple auxiliary active clamping circuit for each leg of a classical bridgeless dual boost configuration. Such auxiliary circuit, operating in soft-switching mode, guarantees active clamped voltage and zero voltage switching operations of the main switches and of the slow diodes without interesting the main power path. High efficiency in continue current mode operations and reduced size are assured. In the paper the operating principle, soft-switching conditions and steady state analysis have been presented. A 2000 W prototype, suitable for automotive residential charger applications is built and experimental set-up to verify the theoretical analysis has been provided. The experimental results demonstrate unitary power factor (99.96%), full achievement of EN 61000-3-2 standard, peak efficiency of 98.9 % and THD less than 3 %.

Keywords: Boost PFC Converter, Battery Charger, Pure Electric Vehicle, ZVS Active Clamped.

Modified SHEPWM Switching Strategy for Multilevel Inverters
by N. Farokhnia, S. H. Fathi

Vol. 6. n. 3, pp. 1070-1076

Abstract - SHEPWM switching strategy is a well-known strategy which has been widely applied to multilevel inverters about 2 decades. Usually, based on degrees of freedom, some low order harmonics are removed. Since the corresponding equations are nonlinear and cannot be perfectly satisfied, only less than 50% of interval of M has feasible solution. In this paper, instead of eliminating harmonics, it is proposed to reduce them below the permitted values which are determined by standards such as IEEE standard 519-1992. In IEEE standard 519-1992, 3% of individual low order harmonics and 5% THD are acceptable. A 7-level cascaded H-Bridge inverter is selected here as a case study. Simulation and experimental results verify the effectiveness of the proposed method in expanding the interval of modulation index, over which, feasible solution exists for the switching angles.

Keywords: Multilevel Inverter, Selective Harmonic Elimination PWM, Non-Zero Harmonics And Modulation Index.

Negative-Output Soft Switched KY Buck Converter
by K. I. Hwu, Y. T. Yau

Vol. 6. n. 3, pp. 1077-1085

Abstract - A negative KY buck converter is presented herein along with its soft switching operation. This converter can transfer the positive input voltage to the negative output voltage. Above all, zero voltage switching (ZVS) and zero current switching (ZCS) are used to achieve soft switching operation. Moreover, the input current is limited to some extent. In this paper, the behavior of the proposed circuit is firstly described in detail, and secondly some simulated and experimental results are provide to demonstrate the effectiveness of the proposed topology.

Keywords: Negative-Output KY Buck Converter, Soft Switching, ZVS, ZCS.

Design of a Hybrid Power Fed-Converter and Time Controller for LED Traffic Light Systems
by K. H. Chao, R. H. Lee , K. L. Yen

Vol. 6. n. 3, pp. 1086-1093

Abstract - The main purpose of this paper is to develop an intelligent LED traffic light system with hybrid power from photovoltaic (PV) module as well as commercial sources. First, LED traffic lights powered with hybrid power from photovoltaic module and commercial source are designed and implemented. The PV module with a maximum power point tracker (MPPT) and a boost converter is employed to supply a suitable voltage level for LED traffic lights. The photovoltaic module and commercial sources generated the power complementarily so the solar energy can be utilized most effectively. To reduce hardware size, the proposed LED traffic light system is implemented using Programmable System on a Chip (PSoC). Then, a novel extension traffic flow control method based on the extended correlation function and the matter-element model is proposed to control the traffic flow. Some simulation and experimental results are made to verify the effectiveness of the proposed intelligent LED traffic light system with hybrid power from photovoltaic module and commercial source.

Keywords: LED Traffic Light System, Hybrid Power Source, Photovoltaic (PV) Module, Extension Theory, Programmable System on a Chip (PSoC), Traffic Flow Control.

Line Voltage THD calculation of Cascaded Multilevel Inverter's Stepped Waveform with Equal DC Sources
by Naeem Farokhnia, Hadi Vadizadeh, Fariba Anvariasl

Vol. 6. n. 3, pp. 1094-1108

Abstract - Multilevel Inverters can produce a stepped voltage that has less harmonic content rather than H-bridge inverters. THD is normally used as a benchmark to evaluate the harmonic content. In literature, the THD formula of phase voltage of the multilevel inverter has been presented. But, for calculation of line voltage THD where, triplen harmonics are removed, approximate methods have been used. In this paper, actual line voltage THD as a multi criteria formula is presented. Both methods are compared. It is shown that approximate method has not the capability to be used in all operating points (switching angles values) and the difference in notable. The formulas accuracy is verified. Finally experimental results are offered.

Keywords: Multilevel Inverter, Equal DC Sources, Stepped Waveform, Formulation of Line Voltage THD.

Reliability Estimation of Uninterruptible Power Supply Using Reliability Block Diagram Method
by M. K. Rahmat, S. Jovanovic

Vol. 6. n. 3, pp. 1109-1117

Abstract - The aim of this paper is to investigate the reliability estimation technique for the Uninterruptible Power Supply (UPS) systems. A new methodology in estimating the reliability parameters of the AC Uninterruptible Power Supply (AC UPS) using the Reliability Block Diagram (RBD) method is proposed. In contrast with the existing UPS reliability prediction methods that requires more input data and computationally tedious, this approach provides useful and fast method to evaluate the system’s Failure Rates, Mean Time Between Failures, Availability and Unavailability. Reliability parameters obtained from five major UPS configurations were compared and discussed in detail. Equations for calculating the MTBF and Unavailability were presented along with component reliability estimates. Sensitivity analysis on the major components of the AC UPS was performed to investigate the effect on the overall system reliability. Finally, the actual field data from industrial best practice were used to validate the results obtained.

Keywords: Uninterruptible Power Supply, Reliability Block Diagram, Mean Time Between Failures, Availability, Unavailability.

Fuzzy Logic Controlled Three-phase Three-wired Shunt Active Power Filter for Power Quality Improvement
by N. Gupta, S. P. Singh, S. P. Dubey, D. K. Palwalia

Vol. 6. n. 3, pp. 1118-1129

Abstract - The simulation and experimental study of a digital signal processor based fuzzy logic controlled, three-phase shunt active power filter to improve power quality by compensating current harmonics and reactive power required by non-linear load is presented. Conventionally, dc-link voltage regulation is achieved by PI controller. However, during load changes, there is considerable variation in dc-link voltage which affects the controller dynamic performance. The proposed work replaced the PI controller by fuzzy logic controller to improve the transient performance of the dc link under fast load variations. The superiority and accuracy of fuzzy controller depends upon linguistic variable set theory and does not require a mathematical model of the system. The proposed control scheme is simple and it is capable of maintaining compensated supply currents sinusoidal and balanced, irrespective of the distortions and unbalance in load currents. Simulations are carried out using MATLAB/Simulink environment to show the effectiveness of the proposed methodology. A laboratory prototype based on TMS320F28335 digital signal processor (Texas Instrument, USA) has been developed to verify the simulations results. Simulated and experimental results reflect the effectiveness of the proposed active power filter control scheme to meet the IEEE-519 standard recommendations on harmonic limits.

Keywords: Power Quality, Active Power Filter, Fuzzy Logic Controller, Hysteresis Current Controller, Current Harmonics, Reactive Power Compensation, Digital Signal Processor.

Two Types of High Step-Up DC-DC Converters Based on Charge Pump and Coupling Inductor
by K. I. Hwu, W. C. Tu, C. H. Lin

Vol. 6. n. 3, pp. 1130-1139

Abstract - Two types of high step-up DC-DC converters based on the concept of the charge pump and coupling inductor, together with a passive voltage clamping circuit which pumps part of the leakage inductance energy to the output, are presented herein. Moreover, the implementation of the passive voltage clamping circuit for this converter with multiphase is very easy. Above all, there are two types of high step-up converters in this paper, depending on gate driving signals without changing any circuit structure. In this paper, the basic operating principles of the proposed converter are firstly described, and secondly some experimental results are provided to verify the effectiveness of the proposed converter topologies.

Keywords: Charge Pump, Coupling Inductor, Passive Voltage Clamping Circuit.

High Voltage Ratio Interleaved Boost DC-DC Converter for High Power Fuel Cell Application
by A. S. Samosir, M. Anwari, A. H. M. Yatim

Vol. 6. n. 3, pp. 1140-1146

Abstract - The application of fuel cell is increasing in the last years mainly due to the possibility of high efficient decentralized clean energy generation. Fuel cells are a potential power source for electric vehicle or distributed power generation system. In electric vehicle application, a high power boost dc-dc converter is adopted to adjust the output voltage, current and power of fuel cell engine to meet the vehicle requirements. The major challenge of designing a boost converter for high power application is how to handle the high current at the input and high voltage at the output. In this paper, a high voltage ratio interleaved boost dc-dc converter is proposed for stepping-up the voltage on high power application. A prototype of converter system was built. The experimental waveforms of the high voltage ratio interleaved boost converter are presented.

Keywords: Interleaved Boost Converter, Fuel Cell Electric Vehicle, High Voltage Ratio, High Power Application.

1-MHz High Frequency Resonant AC Power Supply System
by Ching-Ming Lai, Yi-Hung Liao

Vol. 6. n. 3, pp. 1147-1153

Abstract - A growing demand for size reduction of power systems has stimulated substantial development and research efforts in high power density power supplies. To achieve high power density converters, it is required that they operate at high switching frequencies. This paper presents a high frequency resonant ac power supply with frequency tracking control by using Phase-locked loop (PLL) techniques. Based on the PLL control method, the resonant inverter can be guaranteed to provide a stable operation characteristic in spite of sensitive load parameters variation as well as power regulation. The detailed control circuit and the operation principle of resonant ac power supply are analyzed and verified experimentally.

Keywords: Resonant Ac Power Supply System, Phase-Locked Loop (PLL).

Multi-Output Isolated DC-DC Converter with Cross Regulation Taking into Account Load Transient
by K. I. Hwu, Y. T. Yau, Jenn-Jong Shieh

Vol. 6. n. 3, pp. 11534-1160

Abstract - In this paper, a one-comparator counter-based sampling strategy, together with the proposed primary-side post regulator and the proposed pulse width modulation (PWM) type, is applied to a forward converter with a single isolation stage and multiple outputs having synchronous rectification (SR). With only the required comparators and without any analog-to-digital converter (ADC), the information on feedback output voltage is entirely obtained according to the counter. To upgrade the load transient response, the proposed nonlinear control technique is applied. Therefore, the proposed control topology can improve the cross regulation and load transient response of the SR forward converter. In this paper, the proposed sampling and control schemes are described and some experimental results are provided to verify its feasibility.

Keywords: Cross Regulation, Load Transient Response, Multi-Output, SR, without any ADC.

Torque Ripple Reduction in Direct-Driven Permanent Magnet Wind Generators
by Vesa Ruuskanen, Janne Nerg, Panu Kurronen, Juha Pyrhönen

Vol. 6. n. 3, pp. 1161-1173

Abstract - Several methods to improve torque quality in direct-driven permanent magnet megawatt-range wind generators are compared with each other, including magnet width variation, skewing, magnet shaping, buring magnets inside the rotor lamination, stator slot placement, and asymmetric magnets. Both the load torque quality and the cogging torque are analyzed by the two-dimensional (2D) finite element method (FEM). The effect of the torque ripple reduction methods on the machine performance and characteristics with reference to no-load voltage and manufacturing are also discussed.

Keywords: AC Electrical Machines, Cogging Torque, Permanent Magnet Synchronous Machine, Torque Ripple, Wind Generator.

Using Particle Swarm Optimization Algorithm for Transformer Transient Study
by Vahid Rashtchi, Ebrahim Rahimpour, Jaber Mirzaei

Vol. 6. n. 3, pp. 1174-1180

Abstract - The R-C-L-M model of power transformer is able to simulate the high frequency behavior of the magnetic and electric filed inside transformer. This model is used not only in design step for studying transient phenomena but also during operation for detecting mechanical faults. The model is obtained from geometrical structure and the material properties of the transformer. While the precision of the model depends strongly on the precision of its parameters, the accuracy of these parameters calculated by analytical formulas is limited due to different reasons. In this paper a particle swarm optimization (PSO) algorithm is introduced as a method to identify the parameters of the R-C-L-M Model, which are more precise than the parameters achieved by common formulae.

Keywords: Transformer, Transient Model, Parameter Identification, Particle swarm optimization (PSO).

Measurement and Mathematical Fitting of Partial Discharge Pulse Burst in Transformer Oils
by Junhao Li, Quanwei Hu, Wenrong Si, Yanming Li

Vol. 6. n. 3, pp. 1181-1186

Abstract - Partial discharge (PD) detection is a technique widely used for high voltage equipment insulation condition assessment. In such applications, an understanding of PD mechanisms, characteristics and development processes is important. In this paper, PD characteristics of transformer oils are examined under AC conditions, using a needle-to-plane electrode system. The PD activity in transformer oil is confirmed as appearing in pulse burst form. The duration time of PD pulse bursts was found to decrease with voltage above the PD inception voltage; this decrease was accompanied by both an increase in number of discrete PD pulses and their average maximum amplitude within the pulse burst itself. In order to obtain the increase principle of pulse amplitude within PD pulse burst, mathematical fitting models for discrete pulse current peak value within PD burst are established using exponential express and validity of mathematical models is proved by fitting error.

Keywords: Partial Discharge, Oil Insulation, Pre-Breakdown, PD Pulse Burst, Fitting.

Investigating the Effects of I-Shaped Cores in an Outer-Rotor Transverse Flux Permanent Magnet Generator
by Seyedmohsen Hosseini, Javad Shokrollahi Moghani, Bogi Bech Jensen

Vol. 6. n. 3, pp. 1187-1195

Abstract - This paper deals with the effects of I-shaped cores in an outer-rotor transverse flux permanent magnet generator. Performance characteristics of a typical outer-rotor transverse flux permanent magnet generator are obtained in two cases; with and without I-shaped cores. The results show that although using I-shaped cores can increase the output power to weight ratio and the power factor, the cogging torque as well as output harmonics increase. Moreover, construction with I-shaped cores is complicated because of the forces exerted on these during operation. The analysis in this paper presents the advantages and disadvantage of using I-shaped cores and emphasizes the necessity of performing a tradeoff study between using and not using I-shaped cores in practical transverse flux permanent magnet generators.

Keywords: Cogging Torque, Finite Element Analysis, Generator, Permanent Magnet, Transverse Flux.

Application of Duffing Oscillators to Dynamic Eccentricity Fault Detection in Squirrel Cage Induction Motors
by Vahid Rashtchi, Reza Aghmashe, Mansor Ojaghi

Vol. 6. n. 3, pp. 1196-1203

Abstract - Air gap eccentricity in a three-phase squirrel cage induction motor is one of the most common faults that can make it necessary to remove the motor from the production line; thus, fault diagnosis in induction machines is gaining more attention. The development of motor drive systems with fault diagnostic and prediction features is of great concern and would help to avoid costly breakdowns. In this paper, a novel approach, based on chaos theory, is presented for detecting dynamic eccentricity. A chaotic oscillator called the Duffing oscillator is used for fault diagnosis. The presence of a fault is detected from a phase transition from chaotic motion to periodic motion in the Duffing oscillator phase plane. The method is tested on an eccentric motor under different loading conditions. Experimental results demonstrate the effectiveness of the proposed technique and the suitability of Duffing oscillators for diagnosing faults due to dynamic eccentricity.

Keywords: Squirrel Cage Induction Motor, Dynamic Eccentricity, Duffing Oscillator, Fault Diagnosis.

Direct Torque Control of Induction Motor in Field Weakening Without Outer Flux Trajectory Reference
by Petar R. Matić, Slobodan N. Vukosavić

Vol. 6. n. 3, pp.1204-1212

Abstract - In this paper an algorithm for Direct Torque Control (DTC) of induction motor (IM) in field weakening is presented. The study includes the analysis of the usual IM control approaches in field weakening which are based on open loop stator or rotor flux reference calculations from steady-state machine equations. Drawbacks of the usual approaches are pointed out and an algorithm for DTC of IM without outer flux reference is proposed. In the proposed algorithm rotor flux is accomplished automatically by closed loop regulation, enabling fast and well damped torque response with full voltage utilization, and maintaining optimal flux level in the whole range of field weakening. Torque control is obtained by voltage angle control. Effectiveness of proposed method is investigated via simulation and experiment on Digital Signal Processor (DSP) development platform.

Keywords: Induction Motor, Direct Torque Control, Field Weakening.

Stabilizing Method of Speed Adaptive Flux Observer for Speed Sensorless Induction Motor Drives
by Wei Chen, Yong Yu, Dianguo Xu

Vol. 6. n. 3, pp. 1213-1222

Abstract - Speed sensorless vector control induction motor drive systems adopting the speed adaptive flux observer usually suffer from an instability problem in the low speed regenerating mode. Stability analysis of the drive system at the steady state operating point was performed by applying the root-locus technique to the linearized model of the speed estimation system. Based on the analysis, an improved speed estimation method was proposed. The speed accuracy can be greatly improved by adding the magnetizing current error via an adaptation gain to the general speed adaptation law. The instability behavior in the low speed regenerating mode can be remedied by adjusting the adaptation gain on-line. The validity of the proposed scheme is verified by the experimental results.

Keywords: Induction Motors, Speed Adaptive Flux Observer, Speed Adaptation Law, Stability Analysis.

Optimization Algorithm for Improvement Insulation System in HV Generator Based MultiphysicsAnalysis Using FEM
by Diako Azizi, Ahmad Gholami

Vol. 6. n. 3, pp. 1223-1227

Abstract - Electrical insulations are one of the basic parts of electrical machines. Requirement for inspection of the electrical machine insulation along with the electromagnetic tensions is an important fact. Therefore with respect to insulation system improvement of stator, the HV generator can be optimized. Dielectric parameters such as insulation thickness, spacing, material types, geometry of winding and slot are major design factors. A very powerful method available to analyze multiphysics performance is Finite Element Method (FEM) which is used in this paper. The multiphysicsanalysis of various stator coil and slot configurations are used to design the better dielectric system to reduce electrical stresses in order to increase the power of generator in the same volume of core. These processes of optimization have been done according the proposed algorithm. In this algorithm the technical constraints have been considered. This paper describes the process used to perform classical design and improvement analysis of stator slot’s insulation with respect to given objective function and constraints.

Keywords: : FEM, Insulation, Multiphysics, Objective Function.

Analytical Calculation of the Flux Distribution and Demagnetization in Spoke Interior Permanent-Magnet Machines
With Non-Magnetic Shaft
by A. I. Egaña, I. Elosegui, J. M. Echeverría, M. Martínez-Iturralde

Vol. 6. n. 3, pp. 1228-1238

Abstract - This paper presents an analytical method to compute the magnetic flux distribution in spoke interior permanent-magnet (IPM) machines with non-magnetic shaft from no-load to short-circuit conditions. Despite non-magnetic shaft gets significant reduction of the PM leakage flux, this cannot be neglected to calculate correct flux distribution; thus, shaft leakage flux is analyzed and modelled. Moreover, as the demagnetization characteristic of the machine depends on the magnetic circuit, simple mathematical equations to estimate the demagnetization level of the magnets are also given. Based on this approach, protection against demagnetization due to short-circuit current and maximum field-weakening level achievable are easily estimated. The presented formulation and methods are used to optimize the rotor of an IPM machine in order to maximize the electromagnetic torque (30% higher), minimize the amount of PM material, and protect PMs against demagnetization under field-weakening and short-circuit conditions.
Analytical results are compared with finite-element software, showing errors lower than 4% in the no-load magnetic circuit and lower than 12% at short-circuit conditions. Presented formulation and methods have very low computation time, so the design process time of spoke IPM machines is significantly reduced. The proposed analytical approach is also applicable to other PM machines.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: : Interior Permanent-Magnet Machines, Leakage Flux, Demagnetization, Fault-Tolerance.

A Novel DTC-ISVM for Induction Motor Drive System Fed by Indirect Matrix Converter Using 3-Level Voltage of DC-Link and ALM Estimator to Correct the Stator Resistance
by Vahid Faraji, Davood Arab Khaburi, Majid Aghasi

Vol. 6. n. 3, pp. 1239-1248

Abstract - In this paper, a novel Direct Torque Control (DTC) method based on Indirect Space Vector Modulation (ISVM) technique using Indirect Matrix Converters (IMC) is proposed. This method is characterized by simple structure, minimal torque ripple and unity input power factor. In order to improve the performance of the motor drive system, a suitable switching pattern in rectifier-bridge is proposed which allows to using all of the possible vectors of the indirect matrix converter. By selecting this switching pattern in rectifier-bridge, and controlling of the voltage level of intermediate dc link, it is possible to produce small, medium and large voltage vectors in the IMC. By this way, the electromagnetic torque ripples could be reduced. On the other hand, DTC method uses the stator resistance in its calculation. Variations of this resistance, due to changes in temperature, cause some difficulties at low speeds. Therefore to estimate the changes in stator resistance during the operation of the machine, an Active Learning Method (ALM) is implemented beside the DTC algorithm. The ALM uses its own modeling technique called Ink Drop Spread (IDS) method. The superiority of this method in comparison to conventional methods that uses IMC for DTC is proved by FFT and THD analysis and the simulation results confirm its effectiveness and accuracy.

Keywords: Active Learning Method (ALM), Direct Torque Control (DTC), Indirect Matrix Converter (IMC), Indirect Space Vector Modulation (ISVM), Induction Motor (IM), Ink drop spread (IDS).

Hilbert Transform-Based Bearing Failure Detection in DFIG-Based Wind Turbines
by Yassine Amirat, Vincent Choqueuse, Mohamed Benbouzid, Sylvie Turri

Vol. 6. n. 3, pp. 1249-1256

Abstract - Cost-effective, predictive and proactive maintenance of wind turbines assumes more importance with the increasing number of installed wind farms in more remote location (offshore). A well-known method for assessing impeding problems is to use current sensors installed within the wind turbine generator. This paper describes then an approach based on the generator stator current data collection and attempts to highlight the use of the Hilbert transform for failure detection in a doubly-fed induction generator-based. Indeed, this generator is commonly used in modern variable-speed wind turbines. The proposed failure detection technique has been validated experimentally regarding bearing failures. Indeed, a large fraction of wind turbine downtime is due to bearing failures, particularly in the generator and gearbox.

Keywords: Wind Turbine, Doubly-Fed Induction Generator, Fault Detection, Amplitude Modulation, Hilbert Transform.

Investigation of Electromagnetics Characteristics in External Rotor SRM Under Dynamic Eccentricity Fault
by E. Afjei, H. Torkaman

Vol. 6. n. 3, pp. 1257-1263

Abstract - External Rotor Switched Reluctance Motor (ERSRM) has growing use in applications that demand high torque and high performance in small motor sizes. Aerospace and automotive are such areas where these motors may be used. In this regard, magnetostatic analysis and condition monitoring of these motors would provide added value. This paper investigates the influence of dynamic eccentricity fault on the ERSRM performance with a view to arise a valuable control and condition monitoring trends. The three dimensional Finite Element Method (3D-FEM) is used for the measurements of the main profiles of the motor under healthy and eccentric conditions. In this context, applicable profiles such as flux linkage, inductance, mutual inductance, flux density and radial force are calculated and analyzed. An assessment is also provided to evaluate the impact of the saturation. The results are presented to substantiate those aforementioned profiles analysis could be feasible tools for diagnosing the condition of ERSRMs under influence of dynamic eccentricity fault.

Keywords: Switched Reluctance Motor, External Rotor Machines, Electromagnetics Analysis.

Extended PNGV Battery Model for Electric and Hybrid Vehicles
by Mohamed Daowd, Noshin Omar, Joeri Van Mierlo, Peter Van Den Bossche

Vol. 6. n. 3, pp. 1264-1278

Abstract - Battery performances at different operating conditions, temperature, loading … etc, have a great influence on the performance of the electrical vehicles (EVs) and hybrid electric vehicles (HEVs). Therefore, an accurate and efficient battery model is needful to predict and optimize the battery performance. This paper presents a battery model with a series of innovative aspects into the partnership for a new generation of vehicles (PNGV), which also known as FreedomCAR battery model. The proposed battery model, extended PNGV (EPNGV), proposes some modification in the parameters estimation and modeling techniques as well the PNGV battery model itself. In addition, the EPNGV model includes the influence of the state of charge, temperature, current rates (c-rates) and cycle number on the model parameters, as well the Peukert constant, self-discharging, energy efficiency and state of health prediction. Experimental results of lithium-polymer 12Ah 3.7V batteries are used for the battery models parameters estimation and validation. The EPNGV battery model has been compared with other battery models: the Thevenin and the traditional PNGV battery models at different operating conditions based on experimental and simulation results. The battery parameters estimation as well the battery modeling are implemented using MATLAB/Simulink.

Keywords: Cell Testing, Freedomcar Battery Model, MATLAB/Simulink, Parameter Estimation, PNGV Electrical Battery Model.

A Novel GA Based Technique for Optimizing Both the Design and Control Parameters in Parallel Passenger Hybrid Cars

by K. Varesi, A. Radan

Vol. 6. n. 3, pp. 1279-1286

Abstract - Fuel economy, emissions and performance of the Hybrid Electric Vehicles (HEVs) are greatly affected by Degree of Hybridization (DOH) and control parameters of the vehicle. In this paper, the authors have linked the GA optimization algorithm to the ADVISOR software, for a small parallel hybrid car in order to find the optimal values for DOH and control parameters. In this study, also a new technique has been proposed for deciding about the number of battery modules used in the vehicle, which results in a great improvement in performance of the car. However the proposed methodology takes long time for running the simulations, but, it's simple and at the same time so efficient.

Keywords: Hybrid Electric Vehicle (HEV), Degree of Hybridization (DOH), Electric Motor (EM), Internal Combustion Engine (ICE), Fuel Economy, Performance, Emissions, Genetic Algorithm (GA), Control Strategy, ADVISOR.

International Review of Electrical Engineering - Papers- Part B

Critical Study of Underfrequency Load Shedding Schemes
by A. A. Mohd Zin, Dur Muhammad Soomro

Vol. 6. n. 3, pp. 1287-1296

Abstract - It has been prime objective of any power producer and distributor to supply uninterruptible power to the consumer at its premises with best quality, high reliability and most economy. To ensure quality, reliability and economy, the frequency (f) and voltage of the power supply system should remain constant. If for any reason there is increase in load, or generator outage, or tie line trip there will be inequilibrium between generation and load demand. For this purpose Load Shedding Schemes (LSS) are important and powerful tools in present day power systems (PS) to maintain system stability. They are also quite important where there is lack of adequate spinning reserve margin and shortage of tie line capacity to make up for the lost generation. In this paper critical study of underfrequency LSS (UFLSS) is discussed. The parameters studied include: Static and Dynamic UFLSS. Using DIgSIENT PowerFactory an example of IEEE 009 bus system is also presented.

Keywords: Reliability, System Stability, Spinning Reserve, Tie Line Capacity, Dynamic Underfrequency Load Shedding Scheme.

Optimal Unit Sizing of Distributed Energy Resources in MicroGrid Based on Mixed-Integer Bacterial Foraging Algorithm
by S. M. M. Tafreshi, H. A. Zamani, S. M. Ezzati, H. Vahedi

Vol. 6. n. 3, pp. 1297-1307

Abstract - In this paper, a methodology to perform the optimal unit sizing for Distributed Energy Resources (DER) in MicroGird (MG), has been developed. Based on a Mixed-Integer Bacterial Foraging Algorithm (MIBFA), a new optimal unit sizing method was developed to calculate the optimum system configuration that can achieve the customers required Loss of Power Supply Probability (LPSP) with a minimum Cost of Energy (COE). The proposed method results are validated for single source DG and hybrid DG with results obtained from HOMER and Genetic Algorithm (GA) for the same test systems.

Keywords: ZOptimal Unit Sizing, Cost of Energy, Hybrid Renewable Energy System, Mixed-Integer Bacterial Foraging Algorithm, Genetic Algorithm.

Coordinated Design of STATCOM-Based Damping Controller and Dual-Input PSS to Improve Transient Stability of Power System
by A. D. Falehi, A. Dankoob, S. Amirkhan, H. Mehrjardi

Vol. 6. n. 3, pp. 1308-1317

Abstract - To improve the power system stability and reduce the undesirable multi mode oscillation in power system coordinated design of dual-input Power System Stabilizer (PSS3B) and static synchronous compensator (STATCOM)- based damping controller is performed by the Genetic Algorithm (GA). Due to the GA being perceptive, comfort of implementation, and the ability to impressively solve highly non-linear objective has been approved in academic environments. Coordinated design problem of STATCOM- based damping controller with PSS3B is formulated as an optimization problem. Thus, to solve an optimization problem, subsequently attainment to gain the optimal parameters of STATCOM- based damping controller and PSS3B employed the GA optimization technique. Efficiency of coordinated design between these devices is evaluated under severe disturbance in transmission line and different operating positions for single-machine, infinite-bus power system. Also, a multi machine power system is presented to diminish the power system multi-mode oscillations. Time domain information is use to acquire the objective function for the determination of the optimal parameters of STATCOM-based damping controller and PSS3Bs. The time-domain simulation results show that coordinated design of STATCOM-based damping controller and PSS3Bs increases the power system stability and power system undesirable inter-area and local modes of oscillations in multi machine power system are superiorly damped.

Keywords: STATCOM-based Damping Controller, Dual-input PSS, Genetic Algorithm, Coordinated Design, Power System Stability.

Optimal Bifurcation Control Approach for Small-signal Stability Control of Power Systems
by Wei Gu, Wei Liu, Ping Jiang, Guoqing Tang

Vol. 6. n. 3, pp. 1318-1324

Abstract - Combined with the conception of small signal stability region, this paper proposes an optimal bifurcation control approach to implement the small signal stability control of power systems —“Assuring the uncontrollable bifurcation parameter μ ≥ μref, the optimal configurations of controllable parameters p are searched in the small signal stability region to ensure the minimum control costs”. The mathematic models of optimal saddle-node bifurcation control and optimal Hopf bifurcation control are presented including all kinds of inequality constraints, which strictly ensure both security and economy of power systems. An optimal saddle-node bifurcation control approach, which takes AVR reference voltages as control parameters, is tested in New England 39-bus test system. The initial value prediction and the control parameter selection are proposed for the optimal Hopf bifurcation control of bulk power systems. Simulation results show the effectiveness of the proposed small-signal stability control strategy.

Keywords: Optimal Bifurcation Control, Small-Signal Stability Region, Optimal Saddle-Node Bifurcation Control, Optimal Hopf Bifurcation Control, Aperiodic Instability, Oscillatory Instability.

Using Clonal Selection Algorithm for Sitting and Sizing of Distributed Generation in Distribution Network to Improve Voltage Profile and Reduce THD and Losses
by A. Khanjanzadeh, M. Sedighizadeh, A. Rezazadeh, A. Pahlavanhoseini

Vol. 6. n. 3, pp. 1325-1331

Abstract - The purpose of this paper is minimizing THD and line losses and improving voltage security by DG allocation based on CSA (Clonal Selection Algorithm).The increasing need of electricity and establishing powerhouses, as well as spending a great amount of time to build powerhouses, indicate the necessity of distributed generation in small size and close to the consumer location. In this paper, selecting apart of Tehran network, attempts to investigate the effects of distributed generation on line losses, voltage profile and THD (total harmonic distortion)as one of the indexes of power quality harmony in this network and to consider optional place and sizing to losses reducing. Finally the results are compared to Particle Swarm Optimization (PSO) and Genetic Algorithm (GA).

Keywords: Distributed Generation, THD, Voltage Profile, DG Allocation, Clonal Selection Algorithm, Particle Swarm Optimization, GA.

Optimal PMUs Placement for Power System Observability Using Grenade Explosion Algorithm
by Farshad Khavari, Vahid Naseri, Ali Hesami Naghshbandy

Vol. 6. n. 3, pp. 1332-1338

Abstract - This paper presents a method of optimal phasor measurement unit (PMUs) placement complete observability of a power system using Grenade Explosion Method (GEM). The optimal PMU placement problem is formulated to minimize the number of PMUs installation subject to full network observability. The IEEE 14, 30, 39 and 57-bus test systems and Tehran regional power network, 41-bus practical power system are used for simulation purposes. The results are compared with those of previously obtained in the literature. The results show good efficacy of the proposed algorithm in determining the optimal placement of phasor measurement units to make power system full observable.

Keywords: Phasor Measurement Unit, Observability, Optimal Placement, Grenade Explosion Algorithm.

A New Preconditioner Design Based on Spectral Division for Power Flow Analysis
by Hasan Dağ, E. Fatih Yetkin, Murat Manguoğlu

Vol. 6. n. 3, pp. 1339-1348

Abstract - Solution of large sparse linear systems is the most time consuming part in many power system simulations. Direct solvers based on LU factorization, although robust, are known to have limited scalability on parallel platforms. Thus, Krylov subspace based iterative methods (i.e. Conjugate Gradient method, Generalized Minimal Residuals (GMRES) method) can be used as alternatives. To achieve competitive performance and robustness, however, the Krylov subspace methods need a suitable preconditioner. In this work we propose a new preconditioner for iterative methods, which can be used in Newton-Raphson process of power flow analysis. The suggested preconditioner employs the basic spectral divide and conquer methods and invariant subspaces for clustering the eigenvalues of the Jacobian matrix appearing in Newton-Raphson steps of power flow simulation. To obtain the preconditioner, we use Matrix Sign Function (MSF) and to obtain the MSF itself we use Sparse Approximate Inverse (SPAI) algorithm with Newton iteration. We compare the convergence characteristics of our preconditioner against the well-known black-box preconditioners such as incomplete-LU and SPAI.

Keywords: Iterative Methods, Power Flow Analysis, Spectral Projectors, Preconditioner.

Optimal Placement of Switching Devices in Power Distribution Networks Using the Switch-Position-Exchange Technique
by Kaigui Xie, Kan Cao, Peng Wang

Vol. 6. n. 3, pp. 1349-1355

Abstract - This paper presents a switch-position-exchange (SPE) technique for determining the optimal positions of switching devices (OPSD) in power distribution networks (PDN) when the number of switching devices is pre-specified. In the OPSD process, each candidate switching device is moved to its K-degree-positions (K-DP) in turn for improving system reliability. When the position of a switching device in a PDN is changed, the rules for the corresponding system reliability variation can be derived using a section technique. System reliability is only updated for those sections whose nodal classes have been changed during switching exchange in reliability evaluation. Case studies on the RBTS and a practical PDN show that the SPE is a very useful technique for determining the OPSD, and the SPE technique usually provides a better result than those from the existing methods.

Keywords: Power Distribution Networks, Optimal Placement of Switching Devices, Reliability Evaluation, Section Technique, Switch-Position-Exchange Technique.

Optimal Network Reconfiguration for Voltage Sag Mitigation in Distribution Systems Using Improved Genetic Algorithm
by N. Salman, A. Mohamed, H. Shareef, S. P. Ghoshal

Vol. 6. n. 3, pp. 1356-1364

Abstract - Network reconfiguration is an efficient method for line loss reduction in power systems and though uncommon, it can also be employed for voltage sag mitigation. Voltage sag is considered as one of the most common power quality problems. In this paper, a method for improving bus voltage magnitudes during voltage sag is presented. It is done by applying network reconfiguration to the exposed weak area in distribution systems. In the process of reconfiguration, genetic algorithm with a new encoding method is used to maintain radial structure of distribution network while reaching the optimal solution. The simulation results show that the proposed method is efficient and feasible for improving the bus voltage profile during voltage sag considering the benefits obtained from the reduction of the financial losses by the load outages due to voltage sag problems. The proposed method may assist utility engineers in taking the right decision for network reconfiguration.

Keywords: Voltage Sag, Network Reconfiguration, Distribution Systems, Power Quality.

Solution of Multi-Objective Optimal Power Flow with Chaotic Artificial Bee Colony Algorithm
by K. Ayan, U. Kilic

Vol. 6. n. 3, pp. 1365-1371

Abstract - In the study multi objective optimum power flow problem is solved through chaotic artificial bee colony algorithm. For the solution of the problem both chaos theory and artificial algorithm are utilized together. Until today chaos theory has been used with numerous heuristic methods. The chaos theory is utilized together with artificial bee colony algorithm through its application on the best individual at the end of the each generation. The artificial bee colony algorithm is a new population based heuristic algorithm that reaches its global minimum at linear and non-convex problems in a short while. In this algorithm the source of inspiration is the nutrition pursuit of the bees in nature. The proposed method is applied to IEEE 30-bus test system. In order to illustrate the efficiency of chaotic artificial bee colony algorithm the results are compared with other findings in the literature.

Keywords: Artificial Bee Colony Algorithm, Chaos, Multi-Objective, Optimal Power Flow.

A Novel Method to Anti-Islanding in Grid Connected Distributed Generators
by S. Sajedi, F. Khalifeh, T. Karimi, Z. Khalifeh

Vol. 6. n. 3, pp. 1372-1379

Abstract - Islanding operations of DG usually occur when the main utility supply is interrupted due to several contingencies (inrush currents, faults, etc) while the DG is still supplying power to the distribution networks. These conditions have negative impacts on the system protection, restoration, operation, and management. Therefore, it is necessary to detect the presence of this condition and switch off the DG from distribution network or isolate the DG with its load from the rest of the system. In this paper, a new islanding detection method for any possible network loading is proposed based on utilizing and combining various system parameter indices. In order to secure the detection of islanding, eight intentional disturbances are imposed to the system under study in which two sets of them simulate the islanding condition. The proposed technique uses the adaptive notch filters for extracting the frequency of oscillation of generator’s output waveform as one of the output parameter indices. An advantage of this technique is that it does not need to vary the islanding detection boundaries under various system loading conditions.

Keywords: Islanding Detection, Distributed Generator, Adaptive Notch Filter.

A method for the sag-tension calculation in electrical overhead lines
by I. Albizu, A.J. Mazon, E. Fernandez

Vol. 6. n. 3, pp. 1380-1389

Abstract - The sag and tension values of overhead conductors are influenced by the creep developed during the line lifetime. This paper presents a method for the sag-tension calculation of overhead conductors that is characterised by the creep sequential calculation. Thus, the creep developed in previous stages influences the creep developed in subsequent stages. Two periods are differenced in the creep development: the installation period and the operation period. The relation between the creep development and the factors that influence it such as the installation process and the operation conditions during the line lifetime is described step by step.

Keywords: Sag-Tension, Overhead Conductor, Creep.

Optimal Distributed Generation Placement Using Hybrid Genetic-Particle Swarm Optimization
by L. Y. Wong, M. H. Sulaiman, Siti Rafidah Abdul Rahim, O. Aliman

Vol. 6. n. 3, pp. 1390-1397

Abstract - This paper proposes a hybrid Genetic-Particle Swarm Optimization (HGPSO) method for the allocation of distributed generation (DG) in distribution system. The mutation operation of the Genetic Algorithm (GA) is implemented into the Particle Swarm Optimization (PSO) approach. This proposed method is used to determine the location and size of the DG and the objective function to be minimized in this problem is the total power losses of the system. The program was simulated using MATLAB software and the proposed method has been tested on IEEE 30 and 69-bus test systems.

Keywords: Distributed Generation, Hybrid Genetic-Particle Swarm Optimization, Loss Minimization, Voltage Improvement.

Hybrid Railway Power Quality Conditioner for Autotransformer-Fed AC Electrified Railway Systems
by Haneol Park, Joongho Song

Vol. 6. n. 3, pp. 1398-1408

Abstract - The AC electrified railway systems have several power quality problems, which include mainly the harmonic current pollution, the reactive power demand, and the load imbalance. This paper proposes a hybrid railway power quality conditioner and a novel control algorithm based on the synchronous reference frame and the level-shifted PWM to compensate those power quality problems. The proposed hybrid railway power quality conditioner is applied to the autotransformer-fed AC electrified railway system, and then is comprehensively investigated through the case study. The simulation results demonstrate the proposed hybrid railway power quality conditioner can compensate effectively the harmonic current pollution, the reactive power demand, and the load imbalance, and further the proposed control algorithm brings good dynamic and steady-state performances to the autotransformer-fed AC electrified railway system.

Keywords: Electrified Railway, Power Quality, Active Power Filter, Railway Power Quality Conditioner.

Power Quality Management Platform for Smart Grid
by Wei Gu, Fang Wang, Zhi Wu, Xiao-Dong Yuan

Vol. 6. n. 3, pp. 1409-1416

Abstract - As renewable sources and electric railways are largely connected into power grid, with the development of smart grid and the demand of high-quality power supply, power quality have become a major concern in power industry. Since traditional power quality monitoring system cannot meet expanding demands from customers and power supplies, a better one is in great need to improve power quality of distribution network, help customers to participate in power quality management. In this paper, a smart power quality management platform is proposed and purposes, framework, main functional modules as well as implementation strategies of smart platform are described in details. At last, practical application in Jiangsu province and the idea of utilizing smart platform into the premium power park are presented, results of which show smart platform has much extensive research space and great application prospects.

Keywords: Power Quality Management, Power Quality Assessment, Custom Power, Premium Power Park, Smart Grid.

Proposing a Market based Approach for Restoration of Power Systems
by H. R. Jafarian, M. Rajabi M., M. H. Javidi

Vol. 6. n. 3, pp. 1417-1424

Abstract - Power system restoration is an important task for system operators. Therefore, much research has been carried out to optimize restoration process, among which, recognition and access to the network skeleton during restoration has been considered as a dominant approach. If the main skeleton-network is recognized appropriately, then reconfiguration and restoring major parts of the network can be performed at the shortest possible time.
Restructuring in power industry has introduced new challenges to power system. While, restructuring has affected power system operation seriously, little attention has been paid to restoration process as an extra ordinary mode of system operation in a market based environment. One approach for restoration problem is based on performance indices introduced to rank nodes of the network. In this paper, a new method based on a comprehensive ranking index for electrification of network buses during restoration process is proposed which results in reduction of both the interruption cost and restoration cost. In our ranking approach, both the network configuration and the value of lost load at different buses of the network have been considered in a market based operated system. In the method, the dominant network skeleton for restoration is distinguished such that the restoration time for the rest of network from this skeleton network will be reduced. Our simulation results confirm the validity and efficacy of our proposed approach in different situations, especially in a market-based environment. We have used the Genetic Algorithm (GA) to solve the optimization problem. The method has been tested on IEEE 30-bus network. Results show that this method in compare with similar methods has a better performance.
Copyright © 2011 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Power System Restoration, Skeleton-Network Reconfiguration, Restructured Power Industry, Genetic Algorithm.

Locating and Sizing Static Synchronous Series Compensator Using Fuzzy-Genetic Algorithm
by Seyed M. H. Nabavi, Somayeh Hajforosh, Sajad Hajforoosh, Ahmad Karimi

Vol. 6. n. 3, pp. 1425-1438

Abstract - IThis paper presents a genetic algorithm (GA) to maximize total system social welfare and alleviate congestion by best placement and sizing of SSSC device, considering its investment cost in a double-sided auction market. To introduce more accurate modeling, the valve loading effects is incorporated to the conventional quadratic smooth generator cost curves. Considering valve point loading effect in the gradient-based algorithms introduces non-convex and non-differentiable regions and complicates the optimization problem. In addition, quadratic consumer benefit functions integrated in the objective function to guarantee that locational marginal prices charged at the demand buses is less than or equal to DisCos benefit, earned by selling the power to retail customers. The proposed approach utilizes genetic algorithms for optimal scheduling of GenCos and DisCos, as well as optimal placement and sizing of SSSC unit. In addition, the Newton-Raphson approach is used to minimize the mismatch of the power flow equation. Simulation results on the modified IEEE 14-bus and IEEE 30-bus test systems (with/without line flow constraints, before and after the compensation) are used to examine the impacts of SSSC on the total system social welfare improvement versus its cost. To validate the accuracy of the proposed method, several case studies are presented and simulation results are compared with those generated by sequential quadratic programming (SQP) approaches.

Keywords: Social Welfare Maximization, Congestion Management, Double-Sided Auction Market, Generator And Load Rescheduling, SSSC, GA.

A Genetic Algorithm to Minimize the Periodic Preventive Maintenance Cost in Electrical System
by Z. Otsmani, M. Khiat, A. Chaker

Vol. 6. n. 3, pp. 1439-1446

Abstract - This article describes a methodology to minimize the preventive maintenance (PM) cost of series-parallel system. This flexible methodology based on the genetic algorithm (GA) was used successfully to determine the solution vector of system component inspection periods (Tp) and the optimization of the function cost with a constraint of availability. Suggested methodology was applied to the electric feeding system of a natural gas liquefaction unit in Algeria, the results obtained allowed a considerable improvement of the plan of the preventive maintenance in this unit IREE.

Keywords: Availability, Cost, Preventive Maintenance, Optimization, Genetic Algorithm.

Improving Congestion Relief Management as Ancillary Service in Operation Planning Phase with Demand Side’s Presence

by M.H.Moradi, S. Dehghan, A. Mirzaei

Vol. 6. n. 3, pp. 1447-1454

Abstract - This paper introduces congestion relief management (CRM) as one of ancillary services in market structure for improving its operation. The CRM maintains the system operation within the security limits and defines the charge, receiving and paying in non-discriminatory methods which are based on how much of congestion is relieved and caused by each participant. The proposed method is based on congestion relief index (CRI) which can be used for selecting the offers. We compare two market-clearing procedures for CRM in terms of only supply side management and economical efficiency of demand side management to avoid transmission congestion in an optimum manner. We also use a zonal-based congestion relief management approach, which relieves the congested lines in large systems better. These sensitivity zones are determined here based on the congested lines with the CRI. The applied numerical studies are based on the IEEE 30-bus system.

Keywords: Ancillary Service Market (ASM), Congestion Relief Management (CRM), Demand Side Management (DSM).

Finding Nash Equilibrium Point for Optimal Bidding in PAB Electricity Markets based on PSO Algorithm
by Y. Abbasi, N. Bigdeli, K. Afshar

Vol. 6. n. 3, pp. 1455-1462

Abstract - In a deregulated electricity market with transmission constraints and limited number of producers, bidding strategy has become a major issue. In this market, each GenCo may increase its own profit through a favorable bidding strategy. This paper proposes a new method to obtain the Nash equilibrium points for optimal bidding strategy of GenCo's without the use of game theory. For this purpose, the first optimal bidding problem is modeled with two optimization sub-problem. In the first sub-problem, each GenCo maximizes its payoff, and in the second sub-problem, a system dispatch will be accomplished. Then, particle swarm optimization (PSO) algorithm is used to find optimal bidding strategy of each GenCo in this method. finally, each GenCo update its optimal bidding strategy in terms of optimal bidding strategy of other GenCo's until Nash equilibrium points are obtained. The Western System Coordinating Council (WSCC) nine bus test system is used to illustrate the implementation of the proposed method for a typical power system.

Keywords: Electricity Market, Nash Equilibrium Point, Optimal Bidding, Genco, PSO Algorithm.

A Primal-Dual Interior Point Method for Solving Environmental/Economic Power Dispatch Problem
by Hossein Mohammadian Bishe, Ashkan Rahimi Kian, Mahdi Sayyed Esfahani

Vol. 6. n. 3, pp. 1463-1473

Abstract - We proposed a Primal-Dual Interior Point Method (PDIPM) to solve a combined Environmental and Economic Power Dispatch (EEPD) problem. The EEPD problem is a multiobjective problem with competing and non-commensurable objectives. The PDIPM produces a set of nondominated Pareto optimal solutions for the problem. Fuzzy set theory is employed to extract a compromise nondominated solution. The proposed algorithm is applied to the standard IEEE 30 bus six-generator test system. Comparison of our PDIPM results with the various algorithms reported in the literature shows that the solutions of the proposed algorithm are very accurate for the EEPD problem.

Keywords: : Environmental and Economic Power Dispatch, Fuzzy Set Theory, Primal-Dual Interior Point Method.
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Universal Characteristics of Faults in Complex Power System
by Yagang Zhang, Zengping Wang, Jinfang Zhang

Vol. 6. n. 3, pp. 1474-1482

Abstract - The universal characteristics of faults in complex system will be clarified in this paper. Power system is essentially a complex nonlinear system. The complexity is determined by its characteristics about constitution, configuration, operation, organization, etc. The faults in complex systems can not be completely avoided. In this paper, based on principal components analysis theory, two schemes for fault diagnosis will be put forward. According to “Scheme A: node coefficient”, the fault is usually corresponding to the variable with the biggest coefficient in principal component. According to “Scheme B: node score”, the fault is usually corresponding to the node with the biggest principal component score. The innovation of this paper is that two research schemes of principal component analysis are proposed, and both of them have the universal characteristic of faults in complex power system. The advancing of these two schemes will have significant theoretical value and practical significance. These research results will also have guiding significance for fault diagnosis in other kinds of complex systems.

Keywords: Fault Diagnosis, Universal Characteristic, Principal Components Analysis, PCA, Complex System, Phasor Measurement Unit, PMU, Wide Area Measurement System, WAMS.

The Effect of Repairs on the Occurrence of High Order Failure Scenarios in a Bulk Power Transmission System
by Carlos J. Zapata, Daniel S. Kirschen, Mario A. Ríos

Vol. 6. n. 3, pp. 1483-1490

Abstract - For studying the occurrence of high order failure scenarios (HOFS) in bulk power transmission systems, these authors presented in a previous issue of this journal a method based on stochastic point processes (SPP) modeling and Monte Carlo simulation (MCS) that in contrast to other ones can manage time varying failure rates and avoids the cumbersome task of elaborating a list of system operating states. Now, it has been upgraded in order to assess the effect of repairs on the occurrence of HOFS. For this, the repair service rendered in the power system is modeled using SPP and queuing theory concepts; this allows representing constant and time varying repair rates and diverse repair logistics, two features not offered by any other method. After applying this method to a test system, it is concluded that as more limited the resources for repairs are, higher is the risk of occurrence of HOFS. It is then recommended to consider this fact when planning the expansion and the operation of the bulk power transmission system.

Keywords: Monte Carlo Simulation, Power System Reliability, Queuing Theory, Stochastic Point Processes.

Neural Inverse Control of Wind Energy Conversion Systems
by A. Rezazadeh, M. Sedighizadeh, M. Bayat

Vol. 6. n. 3, pp. 1491-1502

Abstract - Induction generators with double inputs have a high efficiency over a wide range of velocities caused by their capability of operation at variable speeds, so their application is increasing progressively. These generators along with wind turbines construct a suitable wind energy conversion system. Due to the intensive nonlinear and variant time characteristics of wind turbines and generators, there are some difficulties in conventional controlling methods. For this reason, usage of an adaptive controller is required. In the present paper, a predictive inverse neural model has been employed in order to control a wind system. In order to design this controller, input-output data set for wind energy conversion systems is required. In this paper, since real data for system were not available, modeling of the considered system has been performed. Afterward, two controlling structures including direct structure and adaptive scheme, which are based on multilayer neural networks, have been introduced for our modeled system. Furthermore, in order to study the ability of proposed controllers, several situations have been considered including the application of instant disturbance, the application of noise on the system as well as parameters variations and uncertainties of the system.

Keywords: Doubly-Fed Induction Generator, Wind Turbine, Neural Inverse Control, Model Identification, Autoregressive Moving Average, Adaptive Control.

Implementation of Particle Swarm Optimization Based Maximum Power Point Tracking of Solar Photovoltaic Array under Non Uniform Insolation Conditions
by R.Ramaprabha, N. Balamurugan and Dr.B.L.Mathur

Vol. 6. n. 3, pp. 1503-1510

Abstract - This paper presents a Global Maximum Power Point Tracking (GMPPT) for a series connected Solar Photovoltaic Array (SPVA) under mismatched irradiance conditions/partially shaded conditions using Particle Swarm Optimization (PSO) technique. Partial shaded SPV modules produce several local maximum power points, which makes the tracking of the global maximum power point a difficult task. Most of conventional tracking methods fail to work properly under these non uniform insolation conditions. Some methods proposed in the literature track the global peak (GP) with some limitations. This paper proposes PSO based GP tracking with the objective of maximizing the power. This method tracks GP by finding the optimum value of SPVA current which maximizes the total power extracted from SPVA. The proposed method is checked for different shading patterns through simulation and verified through experimentation using TMS320LF2407 DSP. The results show the effectiveness and robustness of the proposed optimization approach.

Keywords: SPVA, MPPT, Global Peak, PSO, MATLAB, DSP.

Development of Three-Phase Grid-Interactive Inverter for a 70-kW Microturbine-Based Distributed Generation
by Mahmoud Ranjbar, Mehdi Salehifar, Hassan Ebrahimirad, Saeed Mohaghegh, AmirPirooz Ghaleh, Masoud Serpak

Vol. 6. n. 3, pp. 1511-1521

Abstract - This paper deals with required power electronics interface for a 70 kW microturbine-based distributed Generation system. First, an introduction of microturbine technology and its applications is presented, and then the power electronics interface that is required to transfer microturbine’s output power to an islanded local load or an electric power grid is described. Different control strategies for controlling the inverter in stand-alone and grid connected modes and the seamless transfer between two modes are described in this paper. Also, the required power converter protection system is presented. An LCL filter design and analysis is presented to maintain optimal voltage and current at the point of common coupling. Finally, controller design procedure used in literature is reviewed and applied in the control system design. To show effectiveness of the designed inverter and its digital controller the experimental results based on a constructed 70 kW semi-industrial setup has been demonstrated.

Keywords: Microturbine, Distributed Generation (DG), Grid-Tied Inverter, Islanding, Digital Controller.