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International Review of Electrical Engineering Vol. 6 N. 1-- Part A

International Review of Electrical Engineering Vol. 6 N. 1-- Part B

International Review of Electrical Engineering - February 2011 (Vol. 6 N. 1) - Papers Part A

	Implementation of a ZVS High Power Factor Forward Converter A Programmed Pulse Width Modulation Strategy for AC Voltage Controllers Implementation of a 5 Level Cascaded H-Bridge Inverter Using PWM Strategy with Unequal Carrier Frequency for Optimizing and Reducing the Switching Number Design and Implementation of Current Sharing Control for Switching Power Supply A New Asymmetrical DC-DC Converter with High Voltage Gain Selective Harmonic Elimination in Cascade Multilevel Inverter with Variable DC Sources Using Artificial Neural Networks Soft Switching Converter with Series-Parallel Combination for Medium Power Application Design of a High-Performance Half-Bridge Resonant Inverter Using Piezoelectric Transformer for Driving LED A New Soft Switching Current-fed Converter With Voltage Lifting Analysis and Implementation of a Soft Switching Cuk Converter Harmonic Elimination in Single Phase Systems Using a High Performance Hybrid Active Filter Design and Implementation of a DSP Based Dual-Loop Capacitor Voltage Control of the Z-Source Inverter Elimination of Low Order Harmonics in a Cascaded H-Bridge Seven-Level Six-Phase Inverter with Adjustable DC Sources Design of High Efficiency Wind Power ConverterBased on Duty Boundary Condition Interleaved APWM Converter with Less Power Switches Six-Leg AC-AC Fault Tolerant Converter with Reduced Extra-Sensor Number Comparative Switching Characteristics of the ZCZVT PWM Inverters and Reliability Analysis Experimental Comparison of Current Source and Voltage Source Active Filters with and without the Series-Connected Capacitor Topology and Control of Chopper Type Dynamic Voltage Regulator Implementation of an Interleaved AC/DC Power Converter with ZVS/ZCS Hysteresis-band Current Control of PFC with Constant Switching Frequency Impact of Induction Motor Starting on Ship Power Network Comprehensive Design of a Toroidally-Wound Limited Angle Torque Motor FPGA Based High Performance Torque and Flux Estimator Experimental Analysis of Different Control Methods for the Speed Control of Alternative-Current Servo Motors Effects of Distribution Network Unbalance Voltage Types with Identical Unbalance Factor on the Induction Motors Simulation and Experimental Design and Finite Element Analysis of a Novel Transverse Flux Permanent Magnet Disk Generator Severity Invariant Feature Selection for Machine Health Monitoring A WAN Based FF Controller for a CSI-IM Drive with State Feedback A New Protection Scheme for Power Transformers Using Time Frequency Analysis Field Assisted/Self Excited Switched Reluctance Generator as an Efficient Option in Wide Range Speed Applications Sensitivity Analysis of Effective parameters in Stray Capacitance of Magneto Cumulative Generator Having Integrated Rectangular Cross-Section Turns, with Insulating Coating Investigation of the Stator Semi-Magnetic Wedges Influences on the Behaviour of a Cage Asynchronous Motor Through Time Stepping Finite Element Analysis Method for Optimization of Energy Consumption of Electrical Trains
International Review of Electrical Engineering - February 2011 (Vol. 6 N. 1) - Papers Part B
	Tuning of Damping Controller Parameters Using Multi-Objective PSO Algorithm for STATCOM Improvement of Power System Transient Stability Using TCVR and TCPAR, a Comparative Study Reactive Power Planning Using Evolutionary Algorithms TTC Enhancement Through Optimal Location of FACTS Devices Using Particle Swarm Optimization A Study on the Occurrence of High Order Failure Scenarios in Bulk Power Transmission Systems Power System State Estimation in a Complex Form A Comprehensive Model for Zonal Short Term Load Forecasting Optimal Placement of Rotary Hybrid Flow Controller (RHFC) Considering Operational Management of Power Systems Transmission Expansion Planning Considering Congestion Management Methods in an Operation Period A Robust Approach Based on RCGA-Optimization Technique to Enhance Power System Stability by Coordinated Design of PSS and AVR Cost-Based Unit Commitment and Generation Scheduling considering Reserve Uncertainty using Hybrid Heuristic Technique Cauchy - Gaussian Infused Particle Swarm Optimization for Economic Dispatch with Wind Power Generation New Real-Time Market Facilitating Demand-Side Resources for System Balancing A Proposed Method for Classification of Wide Variety Range of Power Quality Disturbances Using S-Transform Power Quality Comprehensive Assessment Using Grey Theory Limitations of Magnetoresistive Current Sensors in Industrial Electronics Applications Modeling of Polarization in Oil-Paper Insulation Using Recovery Voltage Measurements New Method for MV Distribution Network’s Ground Capacitance Determination by DC Current Injection Partial Discharge Characteristics Over Different Levels of Humidity and Plasma Exposures in a PMMA Bounded Void A Binary Shuffled Frog-Leaping Algorithm for the Optimal Placement and Sizing of Photovoltaics Grid-Connected Systems

International Review of Electrical Engineering - Papers- Part A

Implementation of a ZVS High Power Factor Forward Converter
by Bor-Ren Lin, Chia-Hung Chao, Jin-Fa Wan

Vol. 6. n. 1, pp. 1-14

Abstract - A new soft switching two-switch forward converter is presented. In the proposed converter, active clamp circuit is used to achieve zero voltage switching (ZVS) of all switching devices. In the front-end of the proposed converter, the active clamp boost converter will draw a sinusoidal line current with nearly unity power factor and maintain the dc-link voltage at a constant value. Active clamp two-switch forward converter with current doubler rectifier is used to obtain the isolated output voltage. Active clamp circuit is adopted to recycle the energy stored in the transformer leakage inductor and to limit the voltage stress of switching devices. The current doubler rectifier offers the ripple current cancellation at the output capacitor and reduces the current stress of transformer secondary winding. The circuit configuration and principle of operation are analyzed and discussed. The characteristics of the proposed converter were evaluated on a 90-260Vrms input and 360W/12V output experimental prototype.

Keywords: Two-Switch Forward Converter, ZVS, PFC.

A Programmed Pulse Width Modulation Strategy for AC Voltage Controllers
by S. Ramkumar, V. Kamaraj, S. Thamizharasan, S. Jeevananthan

Vol. 6. n. 1, pp. 15-22

Abstract - Pulse Width Modulation (PWM) control schemes are receiving increased attention on account of their ability to control the harmonic content of the output voltage and/or input current. The main advantage of the PWM technique is the flexibility with which it can be built to generate the firing pulses. Though a number of schemes are in existence, each one is characterized by its own claims. This paper attempts to develop a digital PWM strategy based on equal area criterion with a view to improve the performance of the ac-ac conversion system by making the input current vector to closely follow the source voltage. The basic idea of the proposed area equalization method (AEM) is that the area under any sample of the required sinusoidal-fundamental output and the area of the pulse occur during the same sampling time in the actual output are made equal. The AEM amends the width of each pulse and conjures to extract a distortion less waveform for both output voltage and input current. The twin objectives of the proposed low frequency PWM method, lowering the total harmonic distortion (THD) in the output voltage and improving the input power factor, are elucidated using derived mathematical relations. The values of performance indices derived are authenticated using MATLAB7.1 based simulation study and validated with those obtained from the fabricated prototype module.

Keywords: AC Voltage Controller, Area Equalization Method, THD, Input Power Factor.

Implementation of a 5 Level Cascaded H-Bridge Inverter Using PWM Strategy with Unequal Carrier Frequency for Optimizing and Reducing the Switching Number
by Hasan Bayat, J. S. Moghani, S. H. Fathi, H. Riazmontazer

Vol. 6. n. 1, pp. 23-29

Abstract - The advent of multilevel inverter topologies has caused variety of pulse width modulation (PWM) strategies. In this paper two of these strategies are presented and simulated. A 5 level cascaded H-bridge inverter is simulated using Matlab/Simulink software and the results are investigated. Simulated 5 level cascaded H-bridge inverter is implemented using two presented PWM strategy and simulation results are evaluated and verified by experimental results. One of these strategies called pulse width modulation with unequal carrier frequency, contributes to optimization of switch utilization ratio in cascaded H-bridge multilevel inverters and balances the number of switching in all levels of output voltage. Reducing total number of switching in output voltage cycle is another feature of this strategy that contributes to reduction of power losses in switches and consequently increases efficiency of the inverter. These benefits come without significant change in PWM strategy and don’t increase output voltage THD.

Keywords: : Inverter, Multilevel Inverter, Pulse Width Modulation, Unequal Carrier Frequency.

Design and Implementation of Current Sharing Control for Switching Power Supply
by K. I. Hwu, Y. H. Chen

Vol. 6. n. 1, pp. 30-40

Abstract - Design and implementation of a simple current sharing control technique, based on the concept of the differential-mode choke, is presented herein, which is applied to two-phase synchronously-rectified (SR) buck converter. This current-sharing structure is quite simple. In this circuit, a synchronously-rectified (SR) switch is used to upgrade the efficiency, two phases with phase shift of 180° is employed to reduce the inductor current ripples, and coupling output inductors is utilized to further decrease the inductor current ripples. In this paper, the detailed basic operating principles, together with mathematical derivations, are firstly described, and secondly some simulated and experimental results are offered to demonstrate the proposed control strategy.

Keywords: Current Sharing Control, Differential-Mode Choke, Switching Power Supply.

A New Asymmetrical DC-DC Converter with High Voltage Gain
by B. Fani, M. Delshad

Vol. 6. n. 1, pp. 41-48

Abstract - This paper presents a new zero voltage switching current-fed DC-DC converter with high voltage gain. In this converter all switches turn on under zero voltage zero current switching and turn off under almost zero voltage switching. Furthermore, the voltage spike across the main switch due to leakage inductance of forward transformer is absorbed. The flyback converter which is connected to the output in series, lead to high voltage gain and less voltage stress on the power devices. Considering high efficiency and voltage gain of this converter, it is suitable for green generated systems such as fuel cells or photovoltaic systems. The presented experimental results confirm the integrity of the proposed converter.

Keywords: Current-Fed, DC-DC Converter, Zero Voltage Switching (ZVS), High Voltage Gain, Active Clamp.

Selective Harmonic Elimination in Cascade Multilevel Inverter with Variable DC Sources Using Artificial Neural Networks
by M. K. Bakhshizadeh, S. H. Fathi, H. Askarian J. Milimonfared, N. Farokhnia

Vol. 6. n. 1, pp. 49-57

Abstract - Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) switching strategy is applied for the elimination of low order harmonics in the cascade multilevel inverter with stepped waveform. In this paper, practical implementation of SHEPWM strategy is improved. The case of variable DC sources is investigated and artificial neural network is utilized to perform the calculations. Previous methods have stored the switching angles in a look-up table. The table is one-dimensional and the angles are only function of modulation index. When the case of variable DC sources is considered, it is necessary to make a multi-dimensional look-up table. This look-up table contains a large amount of data without acceptable resolution and also needs multivariate interpolation. The complexity of this method results in harder and expensive implementation of it in practical systems. It is shown that this method can be embedded in the microprocessor systems for real time calculation of the switching angles. In addition, the cost of this hardware is very low. Finally, the results of a prototype system employing the proposed method are presented.

Keywords: Cascade Multilevel Inverter, Selective Harmonic Elimination, Variable DC Sources and Artificial Neural Network.

Soft Switching Converter with Series-Parallel Combination for Medium Power Application

by Bor-Ren Lin, Jia-Yu Dong

Vol. 6. n. 1, pp. 58-66

Abstract - The LLC series resonant converter has been widely used for many power supply systems. Compared with other power converters, LLC series resonant converters can achieve zero voltage switching of MOSFETs in overall operation range. However, the drawback of LLC converters is high current stresses on the transformer secondary winding and output capacitor. For high current application, it is necessary to share equally the load current into each LLC converter. The dc voltage gain of LLC converter is related to the switching frequency. Thus the load current cannot be shared equally by the interleaved pulse-width modulation. In order to automatically share the load current, the parallel LLC converter with series-connected in primary side and parallel-connected in secondary side is presented for high current application. Based on the series resonant behavior, the power MOSFETs are turned on at zero voltage switching (ZVS) and the rectifier diodes are turned off at zero current switching (ZCS). Thus the switching losses on power semiconductors are reduced. In the proposed converter, the primary windings of two LLC converters are connected in series to automatically share the load current and to reduce the current stresses on transformer secondary windings and rectifier diodes. The principle of operation, steady state analysis and design consideration of the proposed converter are provided and discussed. The proposed converter is suitable for high efficiency applications such as LCD-TV, PDP-TV and server power supply unit. The laboratory experiments with a 600W prototype are provided to verify the effectiveness of the proposed converter.

Keywords: Series Resonant Converter, Zero Voltage Switching, Zero Current Switching.

Design of a High-Performance Half-Bridge Resonant Inverter Using Piezoelectric Transformer for Driving LED
by Tsao-Tsung Ma

Vol. 6. n. 1, pp. 67-74

Abstract - This paper presents the design of a high-performance half-bridge resonant inverter (HBRI) using piezoelectric transformers (PT) for driving a light emitting diode (LED) based backlight module. The target of the proposed inverter using a PT, with a physical size of 5-mm thickness and 50-mm length operating at frequency of 60-70 kHz, is designed to work with a resonant circuit to maintain a constant output current for the LED module. Also, the Zero-Voltage-Switching (ZVS) condition is to be achieved over the full operation range. The key resonant inductance and capacitance of the HBRI are optimally designed according to a given set of specifications, i.e. the desired switching frequency, the load current, the load resistance and the PT parameters. The equivalent circuits of PT are firstly investigated with basic two-port network theories. Then, a number of key parameters are developed and mathematically verified. The performance of various control functions and efficiency of the designed HBRI are verified with a practical design example. Both the simulation results using PSIM software and the measured results from simple experimental setups are presented to show the effectiveness of the theoretical analyses and design methods.

Keywords: Half-Bridge Resonant Inverter, Light Emitting Diode (LED), Piezoelectric Transformer.

A New Soft Switching Current-fed Converter With Voltage Lifting
by M. Delshad, B. Fani

Vol. 6. n. 1, pp. 75-79

Abstract - In this paper, a new soft switching high step-up converter is proposed. This converter consists of two flyback transformers and one forward transformer which is able to increase output voltage gain. Active clamp circuit in this converter not only absorbs the voltage spike across the main switches due to leakage inductance but also provides soft switching condition for all switches. This converter controlled by PWM signal, so implementation of control circuit is very simple. In this paper experimental results verify the theoretical analysis.

Keywords: Half bridge current fed converter, PWM, ZVS, Active clamp.

Analysis and Implementation of a Soft Switching Cuk Converter
by Bor-Ren Lin, Chia-Hung Chao, Chien-Lan Huang

Vol. 6. n. 1, pp. 80-88

Abstract - A soft switching pulse-width modulation (PWM) Cuk converter with boost type of active clamp is proposed. Active clamp circuit can help the switching devices in the Cuk converter to be operated at zero voltage switching (ZVS) turn-on. Therefore this converter is suitable for high frequency operation to reduce the size of reactive components. The clamp capacitor and auxiliary switch are connected in parallel with the primary switch. When main switch is turned off, the positive inductor current will flow through the anti-parallel diode of auxiliary switch. At this instant, the auxiliary switch can turn on at ZVS. The principle of operation, system analysis, and design consideration are presented in this paper. Experimental results for a laboratory prototype rated at 400W, input voltage of 150V~300V, output voltage of 200V, and operating at 105kHz are given to demonstrate the effectiveness of the proposed converter.

Keywords: Zero-Voltage Switching (ZVS), Active Clamp Circuit, Cuk Converter.

Harmonic Elimination in Single Phase Systems Using a High Performance Hybrid Active Filter
by M. Salehifar, A. Shoulaie

Vol. 6. n. 1, pp. 89-97

Abstract - In recent years, more and more single phase loads are used in house hold appliances, electronic equipments and etc; these loads have a significant harmonic spectrum in power source current. Although rating of these load for a single consumer is low, as the number of consumers connected to a feeder is increased; harmonic currents with high THD are drawn from power system which can lead to high losses for end users and equipments connected in power system. In this paper, a fully-digital-controlled hybrid series active filter for harmonic elimination and reactive power compensation is presented in single phase systems. Studied configuration is a cheap and high efficiency method to mitigate adverse effects of single phase loads in power distribution system. The hybrid filter composed of two single tuned LC filters and a small-rated active filter. A new control method is proposed for active filter whose important advantage is that it is applicable in the most configurations of power electronic converters such as shunt and series active filters. Another advantage of the presented control method is its fast speed response to load changes, less than 1 cycle. Simulation results using MATLAB program shows the effectiveness of the proposed method. In addition, a hybrid series active filter is implemented verifying the accuracy of the proposed control method.

Keywords: Hybrid Series Active Filter, Single Phase Active Filter, Harmonic Elimination, Reactive Power Compensation, Detection Methods, Power Quality.

Design and Implementation of a DSP Based Dual-Loop Capacitor Voltage Control of the Z-Source Inverter
by Omar Ellabban, Joeri Van Mierlo, Philippe Lataire

Vol. 6. n. 1, pp. 98-108

Abstract - The Z-source inverter is a recently proposed single stage converter topology with buck-boost capabilities. This paper proposes a dual-loop capacitor voltage control, with outer voltage loop and inner current loop, of the Z-source inverter (ZSI). Both controller are designed based on a third order small signal model of the ZSI using the direct digital design method. Real-time control algorithm is implemented using Digital Signal Processor (DSP) linked with MATLAB real time workshop (RTW) as rapid prototyping tool. The feasibility of the proposed dual loop control method has been verified by the simulation and experimental results.

Keywords: Z-Source Inverter, Direct Digital Control, Small Signal Modeling, Dual-Loop Control.

Elimination of Low Order Harmonics in a Cascaded H-Bridge Seven-Level Six-Phase Inverter with Adjustable DC Sources

by H. Hakimollahi, S. H. Fathi, M. Jamshidi, J. S. Moghani

Vol. 6. n. 1, pp. 109-116

Abstract - An analytical and experimental study in elimination of low order harmonics in a cascaded H-bridge seven-level six-phase inverter with adjustable DC sources is provided in this paper. Between different types of switching techniques for multi-level inverters, the Selective Harmonic Elimination (SHE) technique is selected because not only it is capable of working in nominal frequency, which is important in high power and high voltage systems, but also it is flexible to eliminate more harmonics by adjusting DC sources. Since six-phase induction motors began to be a widely acceptable alternative for conventional three phase motors in high power applications, and also inverters with adjustable DC sources present several advantages over the inverters with equal DC sources, a seven-level six-phase inverter with adjustable DC sources is made and chosen as the case study. Genetic Algorithm (GA) is applied for elimination and minimization of output voltage low order harmonics of this system. Finally simulation and experimental results have been obtained which shows a close agreement.

Keywords: Multi-Level Multi-Phase Inverter (MLMPI), Selective Harmonic Elimination (SHE), Genetic Algorithm (GA) , Adjustable DC Sources.

Design of High Efficiency Wind Power ConverterBased on Duty Boundary Condition

by Chung-Ming Yang, Neng-Yi Chu, Liang-Rui Chen, Wun-Chin Wu

Vol. 6. n. 1, pp. 117-122

Abstract - A high efficiency wind power converter, mainly constructed by the proposed duty boundary condition boost converter (DBC-BC) is proposed in this paper. It can work in the high efficiency duty cycle to effectively increase the efficiency of wind power converter. A 3kW prototype is designed and implemented to assess the performance of the proposed DBC-BC. Experimental results show that the proposed DBC-BC can obtain efficiency 95.6%.

Keywords: Duty Boundary Condition, Boost Converters, High Efficiency.

Interleaved APWM Converter with Less Power Switches
by Bor-Ren Lin, M. Y. Li

Vol. 6. n. 1, pp. 123-131

Abstract - This paper presents an interleaved converter to share the load current and achieve soft switching feature on switches. There are two modules in the proposed converter. Two modules are operated with the interleaved PWM to achieve load current sharing, reduce the current ripple on the output capacitor, and regulate the output voltage. In each module, there are two circuit cells to achieve parallel operation. Only two power switches are required in each converter module to realize the parallel operation and equally share the output current. Each circuit cell is controlled using the asymmetrical PWM (APWM) scheme to realize the ZVS turn-on for power switches. The leakage inductance of the transformer is employed to realize the ZVS feature during the transient interval. The voltage stress of each switch is clamped at the input source voltage. Instead of the conventional interleaved converter, each power switch in the proposed converter can achieve both functions of forward converter for one cell and active clamp circuit for the other cell at the same time. Compared with the conventional parallel converters with four circuit cells, the proposed converter has less power switches, less circuit complexity and lower cost. The system analysis, operation principle and design consideration are presented. Finally experiments based on a laboratory prototype with rated 480W are provided to verify the effectiveness of the proposed converter.

Keywords: APWM, ZVS, Half-Bridge Converter.

Six-Leg AC-AC Fault Tolerant Converter with Reduced Extra-Sensor Number
by Mahmoud Shahbazi, Philippe Poure, Mohammad Reza Zolghadri, Shahrokh Saadate

Vol. 6. n. 1, pp. 132-138

Abstract - In order to prevent further damage and to provide the continuity of service of six-leg converter in case of open-switch fault, it is mandatory to perform fast fault detection and converter reconfiguration schemes. Extra sensors are needed to detect the faults rapidly. In this paper, a very fast FPGA-based fault detection scheme is presented that minimizes the number of additional voltage sensors. A six-leg fault tolerant converter topology without redundancy and with bidirectional power flow is studied. First simulations are carried out to evaluate the proposed fault detection principle and the fault tolerant converter topology. The fully digital control and the fault detection are implemented on a single FPGA. Experimental tests of the digital controller and the detection scheme are performed to verify the high performance of the proposed method.

Keywords: Continuity of service, Fault detection; Fault tolerant six-leg converter, Field Programmable Gate Array (FPGA).

Comparative Switching Characteristics of the ZCZVT PWM Inverters and Reliability Analysis
by Mustafa Nil, Metin Nil, Bekir Cakir, Murat Demir

Vol. 6. n. 1, pp. 139-148

Abstract - Switching characteristics of resonance based ZCZVT (Zero Current Zero Voltage Transition) PWM (Pulse Width Modulation) soft-transition inverters analyzed; methods of increasing efficiency and reliability testing were focused on. Several soft-transition inverter structures are developed to eliminate the inadequacies of hard-switched inverters. Electrical circuit analysis is performed using the software ORCAD 10.5.and Micro-Cap 8 Guap Edition. This inverter operates with soft switching at high frequencies under a wide range of line and load voltages. The new proposed circuit includes the characteristics of the desired circuits beforehand. DC bus voltage is gradually modified by the new circuit consisting of magnetic coupling inductor with common air gap. Simultaneously, switching frequency is increased up to 51,02 kHz without any problems. A number of reliability test methods and a plan were proposed for the switching inverter circuit and reliability MTBF calculations performed using the Relex Software in accordance with Mil-Std-217F.

Keywords: Inverter, Switching Frequency, Soft Switching, Snubber, ZCZVT, Reliability Analysis, MTBF.

Experimental Comparison of Current Source and Voltage Source Active Filters with and without the Series-Connected Capacitor
by Perttu Parkatti, Heikki Tuusa

Vol. 6. n. 1, pp. 149-159

Abstract - Active filters are an effective way to decrease harmonics caused by nonlinear loads. Nevertheless, the price, the size and the power losses have often been drawbacks with the active harmonic filters. Power losses of the active filter can be decreased using series-connected capacitors between the supply and the inverter bridge. These structures are usually called transformerless active harmonic filters.
In the paper, five active filter topologies are compared, two of which are conventional and three of which are connected with series-connected capacitors. First, the main circuits and the digital control systems are presented. The filtering performances of the systems with two different kinds of 20 kVA nonlinear load are examined and finally the power losses and efficiencies of the active filters are studied. The comparison is based on experimental tests with the prototypes constructed. The results clearly show the properties of the active filters examined. In addition, the results prove that active filters with series-connected capacitors offer a considerable choice for harmonic filtering when high efficiency is desired and capacitive reactive power is needed.

Keywords: Active Filters, Harmonic Distortion, Power Quality, Power Conditioning.

Topology and Control of Chopper Type Dynamic Voltage Regulator
by Jin Nan, Tang Hou Jun, Yao Chen, Wu Pan

Vol. 6. n. 1, pp. 160-168

Abstract - This article presents a novel design of dynamic voltage regulator using transformer and PWM ac chopper. The proposed voltage regulator adopts an ac chopper converter to generate compensation voltage and uses the transformer to isolate the power converter from the load. The instantaneous voltage predictive control method is designed to regulate the compensation voltage. When input voltage sags and swells occur, proper compensation voltage is obtained by changing the duty cycle of the PWM control signals. Therefore, the load voltage can be kept stable. A prototype dynamic voltage regulator controller system with TMS320F2812 digital signal processor has been developed, its dynamic performance is investigated at different operating conditions such as voltage sags compensation mode and voltage swells compensation mode. The simulation and experiment results show that the proposed dynamic voltage regulator has fast transient response, and can suppress the load voltage fluctuations effectively.

Keywords: Ac Chopper, Dynamic Voltage Regulator, Pulse Width Modulation, Predictive Control, Voltage Sags, Voltage Swells.

Implementation of an Interleaved AC/DC Power Converter with ZVS/ZCS
by Bor-Ren Lin, Feng-Pin Tsao

Vol. 6. n. 1, pp. 169-178

Abstract - This paper presents an interleaved pulse-width modulation (PWM) AC/DC converter to achieve power factor correction in the front stage and to implement zero voltage switching (ZVS) turn-on for power switches and zero current switching (ZCS) turn-off for rectifier diodes in the DC/DC converter. Interleaved boost converters with boundary conduction mode (BCM) are used in the front stage to achieve ZCS turn-on for power switches and reduce the ripple currents at the input and output capacitors. Thus the input and output capacitances can be reduced and the size of boost inductors is also decreased. In the DC/DC converter, three identical series resonant converters are operated in an interleaved PWM scheme to reduce the input and output ripple currents, decrease the output capacitance, achieve ZVS turn-on for switches and implement ZCS turn-off for rectifier diodes. Thus the switching losses of MOSFETs are decreased and the reverse recovery losses of fast recover diodes are eliminated. The proposed converter is suitable for high efficiency applications such as industrial power supply unit, LCD-TV power unit and power supply unit of server and data storage systems. Laboratory experiments with a 1200W (48V/25A) prototype, verifying the effectiveness of the proposed converter, are described.

Keywords: ZVS, ZCS, PFC, Series Resonant.

Hysteresis-band Current Control of PFC with Constant Switching Frequency
by Kessal Abdelhalim, Rahmani Lazhar, Jean-Paul Gaubert, Mostefai Mohammed

Vol. 6. n. 1, pp. 179-185

Abstract - This paper presents a modeling approach to obtain a small-signal model and the digital implementation of a PI controller in the loop voltage and two controllers in the loop current based first on a standard fixed and sinusoidal band hysteresis control, followed by a variable band hysteresis control for a single-phase power factor corrector (PFC). All these controllers have been verified via simulation in Simulink using a continuous time plant model and a discrete time controller. Real-time implementation is performed on an experimental test bed using a rapid prototyping tool. All these controllers are experimentally compared for steady-state performance and transient response. It is shown that the PI controller gives a better steady-state performance under large load disturbance and plant uncertainties, whereas the variable band hysteresis control in the loop current gives a low THD of the input current compared to a standard classical fixed and sinusoidal band hysteresis control.

Keywords: Power Factor Correction, AC-DC, Boost Converter, Switching Frequency.

Impact of Induction Motor Starting on Ship Power Network
by M. Mirošević, D. Sumina, N. Bulić

Vol. 6. n. 1, pp. 186-197

Abstract - The aim of this paper is to analyze the dynamics of the starting of induction motors connected to a synchronous generator in an autonomous operation. A complex mathematical model has been developed with the following components: a diesel engine, a synchronous generator, a mechanical connection between them, and two unregulated induction motors that are fed directly from the terminals of the synchronous generator. For the purpose of the analysis of torsional dynamics of the combined sequences of the starting of induction motors the system is represented as a system with two concentrated masses. The dynamics is analyzed during the starting of two induction motors. The first induction motor starts connected to the unloaded synchronous generator, while the second induction motor starts at different current values of the electromagnetic torque of the first induction motor. The cases with the induction motor unloaded and the induction motor loaded as well as the case of a power supply interruption to an induction motor are analyzed.

Keywords: Synchronous Generator, Induction Motor, Diesel Generator, Torsional Torque, Torsional Stresses.

   Comprehensive Design of a Toroidally-Wound Limited Angle Torque Motor
         by Reza Nasiri Zarandi, Homayoun Meshgin Kelk, Farhad Toorani, Hosein Farahmandzad
         Vol. 6. n. 1, pp. 198-206

Abstract - This paper presents a comprehensive design procedure of a brushless DC limited angle torque motor (LATM) based on magnetic equivalent circuit analysis which predicts its performance and magnetic characteristics. Design of toroidally wounded armature and rotor with two pole tip segments are developed using selected ferromagnetic material and rare earth permanent magnets. Derivation of airgap and other motor dimensions and design parameters with their expressions are given. A finite element analysis verification of designed LATM using a 2D modeling and simulating package is presented. Performance characteristic of analytical model and FEA model of designed LATM is compared which validates the design procedure.

Keywords: Finite Element Analysis, Magnetic Circuit Analysis, Limited Angle Torque Motor.

FPGA Based High Performance Torque and Flux Estimator
by Tole Sutikno, Aiman Zakwan Jidin, Auzani Jidin, Nik Rumzi Nik Idris

Vol. 6. n. 1, pp. 207-214

Abstract - This paper presents a new design of the torque and stator flux estimators for Direct Torque control (DTC) for Field Programmable Gate Array (FPGA) implementation, which permit very fast calculations. An alternative variable word-size approach in two’s complement fixed-point format is used for the implementation, in order to minimize calculation errors and the hardware resource usage. The simulation results of DTC model in Matlab, which performed double-precision calculations, are used as references to digital computations executed in FPGA implementation. The Hardware-in-the-loop (HIL) method is used to verify the minimal error between Matlab simulation and the experimental results, and thus the well-functionality of the implemented estimators.

Keywords: Direct Torque Control, FPGA, HIL, MATLAB/Simulink, Torque and Flux Estimator.

Experimental Analysis of Different Control Methods for the Speed Control of Alternative-Current Servo Motors
by I. Temiz, Z. Dogan

Vol. 6. n. 1, pp. 215-222

Abstract - This paper focused on increasing the control performance of alternative-current servo motor (ACSM) drive by solving problems occurring during the speed control of this motor widely used in many industrial areas. The speed control of ACSM was implemented by a vector-controlled drive controlled by means of the designed external controllers. For this aim, firstly, the equations of ACSM were obtained by deriving mathematical model of permanent-magnet synchronous motor used as ACSM. Then, Proportional-integral, proportional-integral-derivative, fuzzy logic, and adaptive artificial neuro-fuzzy inference system controllers were designed. These controllers were applied into the simulation and experimental studies under different load and speed conditions, and the results of ACSM drive were illustrated.

Keywords: AC Servo Motor, Proportional-Integral, Proportional-Integral-Derivative, Fuzzy Logic, Adaptive Artificial Neuro-Fuzzy Inference System.

   Effects of Distribution Network Unbalance Voltage Types with Identical Unbalance Factor on the Induction Motors Simulation and Experimental
         by M. Heidari, R. Kianinezhad, S. Gh. Seifossadat, M. Monadi, D. Mirabbasi
         Vol. 6. n. 1, pp. 223-228

Abstract - The induction motors are extensively used in the industry because of their simplicity reason of economical and technical preferences in residential, commercial and industrial systems. The unbalance voltage conditions have been taken into consideration by electrical engineers for studying power quality. Excessively growing temperate of rotors and stators, defect of shok entropy armature and insulation as well as damaged bearings, remarkable power defect , unbalanced line currents and lower outcome resulted from the negative effectives of the voltage unbalance. In this paper , speed, torque, copper losses are to be analyzed under the condition of six types of voltage equilibrium by three voltage unbalance factor, a type of three-phase induction motor, through simulation and practical test.

Keywords: Induction Motor, Unbalance Voltages.

Design and Finite Element Analysis of a Novel Transverse Flux Permanent Magnet Disk Generator
by Seyedmohsen Hosseini, Javad Shokrollahi Moghani, Nima Farrokhzad Ershad, Bogi Bech Jensen

Vol. 6. n. 1, pp. 229-237

Abstract - This paper presents a novel structure of a transverse flux permanent magnet disk generator. The proposed disk shape structure simplifies prototyping by using simple laminated steel sheets in comparison with previous transverse flux structures that employ bent laminations and soft magnetic composites. Also the proposed structure has a higher power factor than what has been reported previously for transverse flux permanent magnet structures. After introducing the transverse flux permanent magnet disk generator, the design process is explained and a small power generator is designed and then optimized. The necessity of optimization is to find the best inner radius which maximizes output power to weight ratio, power factor and efficiency. To this end, the optimization process needs three dimensional finite element analyses.

Keywords: Axial Flux Machine, Finite Element Analyses, Generator, Power Factor, Transverse Flux Machine.

Severity Invariant Feature Selection for Machine Health Monitoring
by M. F. Yaqub, I. Gondal, J. Kamruzzaman

Vol. 6. n. 1, pp. 238-248

Abstract - Vibration signals used for abnormality detection in machine health monitoring (MHM) suffer from significant variation in the patterns with fault severity. This variation results in overlap among the features extracted against different fault types and causes severe degradation in fault detection accuracy. This paper identifies a newfangled problem originated by severity variant features and mitigates this impact by using appropriate feature selection based on Fisher linear discriminant (FLD) and Bhattacharyya distance (BCD) to enhance fault classification accuracy. In order to validate the performance of the proposed scheme, training and testing data are obtained from different severity levels. To capture the non-stationary behavior of vibration signal, robust tools such as wavelet transform (WT) for time-frequency analysis is employed. Simulation studies show that the proposed scheme ensures good fault diagnostic accuracy even if training and testing data belong to different severity levels.

Keywords: Severity Invariant, Fault Diagnosis, Machine Monitoring, Wavelet Transform.

A WAN Based FF Controller for a CSI-IM Drive with State Feedback
by I. Gerald Christopher Raj, P. Renuga, V. Rajasekaran

Vol. 6. n. 1, pp. 249-256

Abstract - In this paper a new control strategy for induction motor drives fed by CSI (Current Source Inverter) is proposed. A multivariable state feedback as well as FF (Feed Forward) control is applied for fast regulation and stability of the drive system. The design of the state feedback controller is based on the application of the pole assignment technique of industrial regulation control theory to a d-q axis state space linearised model of the drive and includes a reduced order observer to obtain faster dynamic response. The observer is designed to reconstruct the inaccessible states such as d-q axis rotor currents from the knowledge of the system inputs and outputs. The hardware and software implementation of the controller around an inexpensive microcontroller based kit, controlled by WAN/wLAN is discussed. The simulation results for step changes in references and load torque show the possible improvement in response with the addition of feed forward control.

Keywords: CSI, Feed Forward, Microcontroller, Observer, Pole Placement, WAN/Wlan.

A New Protection Scheme for Power Transformers Using Time Frequency Analysis
by Z. Moravej, A. A. Abdoos, M. Sanaye-Pasand

Vol. 6. n. 1, pp. 257-266

Abstract - This paper presents a new approach for power transformer protection based on Hyperbolic S-Transform (HST) which is a very powerful tool for non-stationary signal analysis giving the information of transient currents both in time and frequency domains. Some important characteristics of differential currents in different transformer operating conditions such as normal, transformer energization, over excitation, internal and external faults are extracted based on HST. Two indices are defined for proposed protection scheme. Thereafter, by setting two proper thresholds, the internal fault currents are accurately discriminated from other operating conditions. The suitable performance of this method is demonstrated by extensive simulation of different faults and switching conditions in power transformers using PSCAD / EMTDC software. Simulation results show that the proposed scheme is robust against noisy condition.

Keywords: Hyperbolic S-transform, Power Transformer Protection, Threshold Value.

Field Assisted/Self Excited Switched Reluctance Generator as an Efficient Option in Wide Range Speed Applications
by M. S. Toulabi

Vol. 6. n. 1, pp. 267-274

Abstract - An interesting combination of two different types of switched reluctance generators (SRG) can be considered as an efficient option to produce electrical energy in wide range speed of applications. To evaluate this configuration, the interesting structure is introduced firstly; secondly the output voltages of both two generators in low speed of applications as well as high speed of applications are illustrated experimentally. In addition, as another inquiry, the efficiency of each generator and the effect of their parameters on the efficiency are also analyzed in wide range speed of applications. The proposed generators have been manufactured within one commonly physical framework. This framework consists of two magnetically independent stator and rotor sets (layers), where each stator set includes four salient poles, while the rotor comprises of two salient poles with almost equal arc lengths and no windings. The first generator called Field assisted SRG has a stationary reel, and so the field coil wrapped around it, and it is placed between the two-stator sets, whereas in the second type named Self excited SRG, there is no field coil. Via experimental findings, it is proven that this interesting combination can help users to obtain electrical energy from low speeds to high speeds of performance through employing each of the generators in special case of study and application separately. This beneficial characteristic of the proposed combination can be noticed as a suitable trait in different industries such as aerospace, automobile and production of electrical energy via windmill.

Keywords: Electric Efficiency, Field Assisted SRG, Self Excited SRG, Voltage Production.

Sensitivity Analysis of Effective parameters in Stray Capacitance of Magneto Cumulative Generator Having Integrated Rectangular Cross-Section Turns, with Insulating Coating
by M. E. Mosleh, M. R. Besmi

Vol. 6. n. 1, pp. 275-284

Abstract - This paper presents effective parameters and a new method to calculate stray capacitance of coil turns of magneto cumulative generator (MGG). The presented method depended to coil geometrical properties. Furthermore, study effective parameter sensitivity in product of stray capacitance between coil turns and between the coil turn and central cylindrical liner. The proposed method is based on the calculation of capacitance between two adjacent turns and capacitance between the coil turns and central cylindrical liner of the generator. This method takes the effects of insulating coating of winding, winding pitch, distance of coil turns to central cylindrical liner and other effect parameters in theory calculations. It will be shown that in order to decrease the overall stray capacitance of the MCG; the rectangular-shape cross-section, length and width of coil should be reduced. Furthermore, coil turns diameter, winding pitch, the air gaps between the coil turn and central cylindrical liner, and thickness of coil turns insolating coating should be increased. The proposed method in this paper is very useful for designing the geometrical structure of the coil of MCG. Finally, we will see that by progress of explosion and volume extension of liner and decrease of the number of turns of coil of the generator to second turn, total capacitance of generator increases and when there remains only one turn in the circuit, there occurs a descending decrease in the total capacitance of the generator.

Keywords: Analysis of effective parameters, magneto cumulative generator, stray capacitance, winding pitch.

Investigation of the Stator Semi-Magnetic Wedges Influences on the Behaviour of a Cage Asynchronous Motor Through Time Stepping Finite Element Analysis
by Joya Kappatou, Konstantinos N. Gyftakis, Athanasios N. Safacas

Vol. 6. n. 1, pp. 285-291

Abstract - The closure of the stator slots of an Asynchronous Motor using wedges to reduce the permeance harmonics is investigated using a transient finite element analysis, which considers the rotor movement. The waveforms of the stator current, the magnetic field in the air-gap and the electromagnetic torque, as well as their harmonic content have been calculated and compared to the case of open stator slots using the 2D Finite Element Model of the Motor. Moreover, the full characteristics of the two simulated models are calculated, using time harmonic finite element analysis.

Keywords: Induction machine, frequency domain analysis, stator wedges, time harmonics, transient finite element analysis.

Method for Optimization of Energy Consumption of Electrical Trains
by M. Mandić, I. Uglešić, V. Milardić

Vol. 6. n. 1, pp. 292-299

Abstract - The paper presents a model of a traction system and a method for optimization of electrical train energy consumption. The simulation model includes traction vehicles, traction substations and catenary for electric railways. The results obtained from the developed model were compared with the measurements in a traction system of 25 kV. The developed method for optimization of energy consumption is based on sequential quadratic programming. The method was first applied to the test case of a few sections, and then on real cases of energy consumption for passenger and freight trains. The obtained results show that by using this optimization method significant savings in energy consumption for traction supply can be achieved.

Keywords: Modified SQP-Method, Energy Consumption, Electric Traction System.

International Review of Electrical Engineering - Papers- Part B

Tuning of Damping Controller Parameters Using Multi-Objective PSO Algorithm for STATCOM
by M. R. Banaei

Vol. 6. n. 1, pp. 300-308

Abstract - In this paper, on the basis of the theoretical analysis of a SMIB, using its modified linearized Phil¬lips-Heffron model installed with STATCOM, the potential of the STATCOM supplementary controller to enhance the dynamic stability of a power system is evaluated by measuring the electromechanical controllability through SVD analysis. This controller is tuned to simultaneously shift the undamped electromechanical modes to a prescribed zone in the s-plane. The problem of robus¬tly STATCOM based damping controller is formulated as an optimization problem according to the eigenvalue-based multi-objective func¬tion comprising the damping factor, and the damping ratio of the undamped electromechanical modes to be solved using PSO technique that has a strong ability to find the most optimistic results. To ensure the robustness of the proposed damping control¬ler, the design process takes into account a wide range of operating conditions. The effectiveness of the proposed controller is demon¬strated through controllability measure, eigenvalue analysis and some performance indices studies. The simulation re¬sults reveals that the tuned PSO based STATCOM controller using the proposed multi-objective function has an excellent capabil¬ity in damping power system low frequency oscillations and enhance greatly the dynamic stability of the power systems.

Keywords: STATCOM, Particle-Swarm Optimization, Multi-Objective, Power System Stability.

Improvement of Power System Transient Stability Using TCVR and TCPAR, a Comparative Study
by Sabir Messalti, Saad Belkhiat, Shahrokh Saadate, Damien Flieller

Vol. 6. n. 1, pp. 309-315

Abstract - This paper examines the effects of Thyristor Controlled Voltage Regulator (TCVR) and Thyristor Controlled Phase Angle Regulator (TCPAR) on the transient stability improvement of a multi-machine power system. The proposed control strategy is proposed to supply a supplementary control signal to both FACTS devices to increase the Critical Clearing Time (CCT). To show the effectiveness of the dynamic oscillation , the criterion of relative rotor angles, using Runge-Kutta method is used to demonstrate that the proposed TCVR and TCPAR controllers significantly improves the dynamic performance of the power system. The effectiveness of the proposed method is tested on the WSCC3 nine-bus system applied to the case of three-phase short circuit fault in one transmission line. The simulation results and their comparison are presented in this paper.

Keywords: Critical Clearing Time CCT, Transient Stability, Runge-Kutta Method, TCVR, TCPAR.

Reactive Power Planning Using Evolutionary Algorithms
by S. K. Nandha Kumar, P. Renuga

Vol. 6. n. 1, pp. 316-323

Abstract - This paper proposes an application of Evolutionary Algorithms (EAs) such as Differential Evolution (DE), Evolutionary Programming (EP), Real coded Genetic Algorithm (RGA), Covariance Matrix Adaptation Evolution Strategy (CMAES) and Particle Swarm Optimization (PSO) to Reactive Power Planning (RPP) problem. RPP is a non-smooth and non-differentiable optimization problem for a multi-objective function. Three loading conditions (Normal load, 1.25% and 1.5% of normal load) have been considered. The IEEE 30 bus system is used to validate the effectiveness of the Evolutionary Algorithms. Simulation results shows that, the DE algorithm gives better results compared to other algorithms for all the loading conditions and it can be better suited for the multi objective RPP problem.

Keywords: Power Systems, Reactive Power Planning, Evolutionary Algorithms, Differential Evolution, Evolutionary Programming, Real Coded Genetic Algorithm, Covariance Matrix Adaptation Evolution Strategy, Particle Swarm Optimization.

TTC Enhancement Through Optimal Location of FACTS Devices Using Particle Swarm Optimization
by M. Sarvi, M. Sedighizadeh, A. A. Bagheri

Vol. 6. n. 1, pp. 324-331

Abstract - Flexible AC Transmission Systems (FACTS) controllers offer an effective means to enhance the power transfer capability of the network. Beside, the extent which a FACTS controller can enhance Available Transfer Capability (ATC) depends on its optimal location and its capacity in the system. This paper investigates the application of particle swarm optimization (PSO) technique to determine the optimal location and optimal capacity of SVC and TCSC in order to enhance total transfer capability (TTC). The effectiveness of the proposed method has been demonstrated on the modified IEEE 9-bus and 30-bus systems.

Keywords: Total Transfer Capability (TTC), Particle Swarm Optimization (PSO) Algorithm, FACTS, SVC, TCSC.

A Study on the Occurrence of High Order Failure Scenarios in Bulk Power Transmission Systems
by Carlos J. Zapata, Daniel S. Kirschen, Mario A. Ríos

Vol. 6. n. 1, pp. 332-339

Abstract - The n-1 reliability criterion has been applied extensively for power systems because the loss of two or more components over a short period due to independent failures has traditionally been considered not credible. However, the post-mortem analysis of some blackouts has shown that these kinds of events do occur; hence, the question about what contingency level is relevant for bulk power transmission systems arises. In order to reply this question, a method for studying the occurrence of high order failure scenarios (HOFS) is presented in this paper; it is based on stochastic point process (SPP) modeling and Monte Carlo simulation (MCS). In contrast to traditional methods, it can include aging, currently a matter of great concern in the power industry, and does not require the elaboration of a list of system operating states, a cumbersome task even for small systems. Results obtained using the IEEE Reliability Test System show that independently of system size or the presence of aging HOFS of order 2 and 3 are the most relevant because they have higher probability of occurrence and lesser time span than others. It is then recommended to consider HOFS of these orders for the study of bulk power transmission systems.

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

Power System State Estimation in a Complex Form
by Domagoj Peharda, Ivica Pavić

Vol. 6. n. 1, pp. 340-345

Abstract - This paper describes power system state estimation problem in a complex form. State estimation problem is defined as a WLS problem with complex variables and solved with directional Newton method. Directional derivative is used to create Jacobian matrix. State variables include complex voltages and complex tap ratios. Numerical example of 3-bus system is given. Convergence properties and calculation speed of the proposed method are examined and compared with classic state estimation on a real 297 bus network with actual measurements.

Keywords: Power Systems, Directional Newton Method, WLS Method, Weighted Least Squares Method, State Estimation, Synchrophasor Measurement.

A Comprehensive Model for Zonal Short Term Load Forecasting
by A. Moshari, A. Ebrahimi

Vol. 6. n. 1, pp. 346-354

Abstract - Short-term load forecasting for small power systems, namely zonal STLF, is one of the issues in the load forecasting area which has vital value for electricity market competitors like retailers and ISO. This paper discusses the common problems related to short term load forecasting which are particularly raised in the small power systems. Identifying bad data which constitute a large portion of load data in these systems, choosing a proper manner for selecting ANN training data, and requirements which should be considered in the structure of zonal STLF to facilitate its employing to different power systems are investigated in this paper. Here, a comprehensive model which considers these problems as well as the generality of structure and the simplicity of implementation is proposed. This model is tested on Isfahan power system which is one of the regional power companies of Iran national power system. The results show that this structure can be implemented effectively and have an acceptable error in spite of large amount of bad data among historical data.

Keywords: Short-Term Load Forecasting, Zonal STLF, Principal Component Analysis, Neural Networks.

Optimal Placement of Rotary Hybrid Flow Controller (RHFC) Considering Operational Management of Power Systems
by R. Rezaeipour, A. Kazemi

Vol. 6. n. 1, pp. 355-362

Abstract - This paper presents a hybrid configuration of FACTS controller named Rotary Hybrid Flow Controller (RHFC) which seeks to improve both steady state and dynamic conditions. The RHFC is comprised of a Rotary Phase-Shifting Transformer (RPST), a multimodule Thyristor-Switched Series Capacitor (TSSC), a multimodule Thyristor-Switched Series Reactor (TSSR) and a Mechanically-switched Shunt Capacitor (MSC). The RHFC provides series compensation and phase shifting simultaneously by injecting a series voltage into the transmission line. In this paper the steady state model of RHFC is developed as a power injection model. This model is used to develop an Optimal Power Flow (OPF) algorithm including RHFC to find the optimal location and settings of RHFC to optimize the total fuel cost, power losses and system loadability. Also, a quantitative comparison of RHFC with PST and UPFC is investigated. The optimal location and OPF results are presented for the IEEE 14-, 30-, 118-bus systems. The simulation results demonstrate the effectiveness of RHFC to control power flow and improve the optimization goals. Furthermore, the simulations are implemented in Matlab and General Algebraic Modelling System (GAMS) softwares.

Keywords: PST, FACTS, UPFC, Rotary Hybrid Flow Controller (RHFC).

Transmission Expansion Planning Considering Congestion Management Methods in an Operation Period
by M. Karimi, A. Pirayesh, A. Farshidfar, M. Hamidian

Vol. 6. n. 1, pp. 363-370

Abstract - In a deregulated power market, it is important to expand or strengthen transmission system in order to provide a fair and competitive environment for all market participants. In this paper a new method for transmission expansion planning, which considers congestion management methods including congestion pricing methods used in day-ahead market and alleviation methods used in real-time reserve market, is presented. In this method, defined market-based criteria such as investment cost, congestion surplus, alleviation cost, and reliability (both adequacy and security) are calculated considering congestion management method in an operation period. Harmony search algorithm is utilized to solve the optimization problem. The proposed method has been applied to IEEE 24-bus reliability test system.

Keywords: Transmission expansion planning, Harmony search algorithm, Optimization, Congestion management methods, Alleviation cost, Congestion surplus.

A Robust Approach Based on RCGA-Optimization Technique to Enhance Power System Stability by Coordinated Design of PSS and AVR
by A. D. Falehi, M. Rostami

Vol. 6. n. 1, pp. 371-378

Abstract - In this paper, Power System Stabilizer (PSS) and Automatic Voltage Regulator (AVR) are selected in order to improve power system stability. Using coordinated design of AVR and PSS, which are investigated using Real Coded Genetic Algorithm (RCGA) optimization technique thoroughly. The Genetic Algorithm is perceptive, ease to perform, and has the ability to impressively solve the highly non-linear problems. Problem of coordinated control of AVRs and PSSs is formulated as an optimization problem. RCGA is developed to solve as an optimization problem to achieve optimal parameters of AVRs and PSSs. To appraise the coordinated design of these devices, three different types of disturbances are considered for single-machine, infinite-bus power system. Also, reduction of power system multi-mode oscillations while a severe disturbance takes place in transmission line of a multi machine power system is completely pursued. The results of nonlinear simulation display that by coordinated design of AVRs and PSSs power system oscillations are exceptionally damped. In addition, undesirable inter-area and local modes of oscillations in multi machine power system are superiorly diminished and the optimal parameters of the controller are obtained.

Keywords: Power System Satiability; Coordinated Design; PSS; AVR; Genetic Algorithm; Single-Machine, Infinite-Bus; Multi-Machine.

Cost-Based Unit Commitment and Generation Scheduling considering Reserve Uncertainty using Hybrid Heuristic Technique
by E.Alishahi, M.Siahi, A.Abdollahi, M.Rahmani, A.Abdollahi

Vol. 6. n. 1, pp. 379-386

Abstract - This paper proposes a new approach for solving generation scheduling and ramp rate constrained unit commitment (GSRCUC) considering spinning reserve uncertainty. In order to handle reserve uncertainty the estimated probability that spinning reserve might be called and delivered is taken into account. A combinatorial genetic algorithm and lambda iteration method is applied to solve such problem. The proposed methodology is implemented to a 10-unit base problem and a 26-unit IEEE reliability test system. The performance of GSRCU model associated with the impact of spinning reserve requirement (SRR) probability is studied in this paper. Numerical results show a significant improvement in the solutions of a cost-based unit commitment in comparison with the other studies.

Keywords: Unit Commitment, Generation Scheduling, Spinning Reserve Uncertainty, Economic Dispatch, Hybrid Heuristic Technique.

Cauchy - Gaussian Infused Particle Swarm Optimization for Economic Dispatch with Wind Power Generation
by N. B. Muthuselvan, M. Devesh Raj, P. Somasundaram

Vol. 6. n. 1, pp. 387-395

Abstract - The utilization of renewable energy resources like wind energy for electrical power generation has undergone several developments in the recent past. The wind electrical power generation is greatly affected by its sporadic nature and weather conditions. Hence to utilize the wind power into traditional grid certain security limitations are to be implemented. In this paper, Economic Dispatch (ED) problem with wind power generation for minimization of the operational cost along with risk minimization is discussed. A Cauchy – Gaussian infused Particle Swarm Optimization (CGPSO) technique employing Cauchy and Gaussian probability distribution function is developed for solving ED problem with wind generation. The developed models are tested on a standard IEEE 30-bus test system. From the analysis it is found that the proposed algorithm is simple, reliable, consistent, and can be implemented for real time applications.

Keywords: Economic Dispatch, Wind Power Penetration, Particle Swarm Optimization, Gaussian and Cauchy Distribution.

New Real-Time Market Facilitating Demand-Side Resources for System Balancing
by Donghan Feng, Preben Nyeng, Jun Xie, Jacob Østergaard, Zheng Yan

Vol. 6. n. 1, pp. 396-404

Abstract - Many demand side resources have the potential to provide fast and low cost balancing services. Switching these devices on and off can be executed in seconds and have limited consequences for the customers if the duration is not long. With carefully designed market rules, tens of thousands of such loads can deliver a well-behaved, stable and predictable balancing support. Based on a comprehensive analysis of the current balancing markets, as well as the technical properties of traditional and potential balancing resources, this paper proposes a new real-time balancing market setup facilitating the participation of demand-side resources. In light of the future environment of increasing intermittent renewable power and distributed energy/storage resources, stochastic time-series and Monte-Carlo simulation are used to analyze the relationship between balancing requirement and generation/demand uncertainties. This research is potentially useful for designing future balancing markets and utilizing demand response for system services.

Keywords: Electric Power System, Active Demand Side, Electricity Market Design, Real-Time Balance, Renewable Energy, Distributed Storage, Electric Vehicle, Vehicle to Grid, Wind Power, Time-Series Analysis, Monte-Carlo Simulation.

A Proposed Method for Classification of Wide Variety Range of Power Quality Disturbances Using S-Transform
by S. Hasheminejad, S. Esmaeili

Vol. 6. n. 1, pp. 405-414

Abstract - This paper proposed a method of detecting and classifying wide range of power quality disturbances using the advantages of S-transform. S-transform is a time-frequency analyzing technique that bridges the gap between the short-time Fourier transform and wavelet transform. Features extracted from S-transform are distinct, understandable and noise has no effect on them. In proposed method by use of s-transform and a discriminative function, twelve kinds of single disturbances like sag, swell, interruption, harmonic, spike, notch, noise, oscillatory transient, flicker, sub-harmonic, DC, inter- harmonic and two complex disturbances are well recognized. The discriminative function which quantify the algorithm output, make the classification easier. Furthermore, it is possible to characterize some of these power quality disturbances very accurately, as well as the number of disturbances happened in a waveform in the period of study. Simulation results show that the proposed method is effective on detecting and classifying and characterizing power quality disturbances. In addition, immunity against noise makes it possible to use this method for real applications. Testing the proposed method with different noise levels and comparison with the results obtained from other methods shows the robustness and effectiveness of proposed method.

Keywords: Classification, Disturbances, Power Quality, S-transform, Distribution System.

Power Quality Comprehensive Assessment Using Grey Theory

by Wei Gu, Fang Wang, Gang Lei, Xiao-Dong Yuan

Vol. 6. n. 1, pp. 415-422

Abstract - This paper proposes a novel approach for power quality (PQ) assessment based on grey relational analysis (GRA). The standard matrix is built according to PQ standards, and the relational grades obtained by GRA are used for ranking the samples. To overcome the shortcomings of single weights, combinational weights of PQ factors are introduced by linearizing the results of the entropy and improved analytic hierarchy process (AHP) analysis. Real measurements are used to test the performance of the proposed approach. Simulation results indicate that the proposed GRA is accurate with more objective and sufficient weights of PQ indices. And this method can provide decision-makers a scientific and feasible technical support.

Keywords: Power Quality (PQ), Comprehensive Assessment, Improved AHP, Integrated Weighting Method, Grey Relational Analysis (GRA).

Limitations of Magnetoresistive Current Sensors in Industrial Electronics Applications
by M. D. Cubells-Beltrán, C. Reig, J. Martos, J. Torres, J. Soret

Vol. 6. n. 1, pp. 423-429

Abstract - Electrical current monitoring is a key issue in the most of the industrial electronics systems. For this reason, a huge effort has been, and is being, carried out in finding optimal current meters, for different scenarios. With the recent development of the giant magnetoresistance principle, the interest on magnetoresistance based electrical current sensors has been relaunched. These sensors display obvious advantages with respect to classical current metering methods, and also when compared to Hall effect based ones. Nevertheless, some issues still need to be fixed, before they can definitively replace the classical schemes. In this paper, a sound and up to date review is made regarding the particular limitations of magnetoresistive based current sensors, when used in industrial environments. These limitations are mainly related to the range of application, voltage offset, surrounding noise sources, temperature drift, bandwidth and lack of electrical models.

Keywords: Current Sensing, Magnetoresistive Sensors.

Modeling of Polarization in Oil-Paper Insulation Using Recovery Voltage Measurements
by Božidar Filipović-Grčić, Dalibor Filipović-Grčić, Ivo Uglešić

Vol. 6. n. 1, pp. 430-437

Abstract - The state of the oil-paper insulation is a key factor for assuring a reliable operation of power transformers. Recovery voltage measurement is one of the methods utilized to estimate the polarization spectrum. Analysis of the polarization spectrum is used to evaluate the condition of the insulation with respect to moisture content and aging. In this paper, the elements which represent a polarization process are determined from recovery voltage measurement test results by using a new method based on genetic algorithm. The method was successfully tested on a simple circuit and then applied to two power transformers located in hydropower plants.

Keywords: Genetic Algorithm, Oil-Paper Insulation, Polarization, Power Transformer, Recovery Voltage Measurement .

New Method for MV Distribution Network’s Ground Capacitance Determination by DC Current Injection
by D. Franković, A. Marušić, V. Šunde

Vol. 6. n. 1, pp. 438-444

Abstract - The paper presents a novel method for Petersen coil regulation based on temporary DC current injection at the MV network neutral point. The introduced disturbance generates a voltage transient in network’s neutral point. Sampling of voltage transient allows for an extrapolation of function parameters which in turn define the MV network’s ground capacitance and resistance.

Keywords: Petersen coil, regulation, DC current injection, distribution network neutral point, resonant grounding, distribution network capacitance measurement and calculation, voltage transient, non-linear least squares.

Partial Discharge Characteristics Over Different Levels of Humidity and Plasma Exposures in a PMMA Bounded Void
by Zainuddin Nawawi, H Ahmad, Rudi Kurnianto, Masayuki Nagao

Vol. 6. n. 1, pp. 445-451

Abstract - The issue of high voltage equipment tropicalization is critical particularly when high voltage equipment designed for temperate application are imported to areas in the tropics. It raises the question whether the insulation used in these equipments can performance under the impact of high relative humidity level and the intense midst noon sun rays. This paper presents the study of dielectric material performance under the impact of relative humidity and plasma exposures to simulate the material aging in service by studying the discharge characteristics of PMMA which was used as the basis of study. The discharge characteristics in cylindrical void bounded by dielectric of polymethylmethacrylate (PMMA) which were exposed to different levels of relative humidity (RH) and plasmas intensity were investigated. The insulation material under test was subjected to AC excitation. The partial discharge (PD) signatures produced were measured with the aid of a CIGRE Method II (CM II) electrode system. It was found that when the void cavity was humidified from 33 % up to 98 %(extreme level), the PD inception voltage decreased about 15 %. For negative AC cycles, the following discharges occur with larger number of pulses, however, with small number of magnitudes. PD seems easily to occur with larger number of pulses as the surface of specimen was degraded by plasma (especially under humid environment).So it is recommended that high voltage equipments imported from temperate countries must performance in the tropics adverse environmental conditions.

Keywords: PD Characteristics, Relative Humidity, Surface Resistance, Plasma.

A Binary Shuffled Frog-Leaping Algorithm for the Optimal Placement and Sizing of Photovoltaics Grid-Connected Systems
by M. Gómez-González, F. Jurado

Vol. 6. n. 1, pp. 452-458

Abstract - This paper introduces a Shuffled Frog-Leaping algorithm based method to accomplish optimal location and size of a Photovoltaic Grid-Connected System for distributed power generation. The main technical constraint is the maximum installed peak power, which is limited for Distribution Companies. The fitness function to be optimized is the profatibility index. Comparisons among the proposed algorithm and other methods are performed. The proposed algorithm reaches the bests solutions when a similar computational time is considered.

Keywords: Distributed Generation, Photovoltaic System, Profitability Index, Shuffled Frog-Leaping Algorithm.