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International Review of Electrical Engineering Vol. 7 N. 5-- Part A

International Review of Electrical Engineering Vol. 7 N. 5-- Part B

International Review of Electrical Engineering - October 2012 (Vol. 7 N. 5) - Papers Part A

	Interleaved Bridgeless AC/DC Converter with High Power Factor Simple Three-Level Neutral Point Voltage Balance Control Strategy Based on Region Selection PWM Random Modulation Schemes for Conducted-Emi Mitigation on Sepic Converter Interleaved APWM Converter for High Voltage Applications Steady-State Error Elimination for Digital or Analog Implemented Sliding Mode Control in Single-Phase Shunt Active Power Filters An Improved High Power Factor-Soft Switched AC-DC Converter Analysis, Design and Implementation of a New Soft Switching High Voltage DC Converter New Resonant DC Link Inverter for Brushless DC Motor Drive with a Simple Auxiliary Circuit Minimum Time Current Control of Three-Phase PWM Rectifier with LCL Filter Interface Implementation of a ZVS DC/DC Converter with Low Voltage Stress MOSFETs and without Output Inductor Real-time Low-Distortion Digital PWM Modulator for Switching Converters ZVS Asymmetrical Full-bridge Buck Converter with Wide Input Voltage Range A Modulation Strategy for DC/AC ConverterBased on Voltage Limitation Criterion Input Power Factor Control of RB-IGBT Based Indirect Matrix Converter An Integrated Derived Boost-Flyback Converter with High Step-Up Conversion Ratio Analysis and Design of LCCL Load Matching Circuit for High-Frequency Induction Heating Series Resonant Inverter A Novel Grid Connected Multi-Input Direct DC-AC Converter Analysis on The Harmonic Components of Torque Characteristics of Single Phase Single Stator Small Size Brushless DC Permanent Magnet Motor: Series and Parallel Magnetic Circuit A New Approach for the Magnetic Characterization of Iron Core Materials - The Case of a Switched Reluctance Motor Design and Implementation of an Extension Robust Controller for Switched Reluctance Motor Drives Effect of the Static Air-Gap Eccentricity & Stator Inter-Turn Short Circuit Composite Fault on the Generator Circulating Current Characteristics Adaptive Modified Elman Neural Network Integral Backstepping Control for a PMLSM Drive System Conversion of Standard Induction Machines to Permanent Magnet Synchronous Machines with Higher Efficiency Optimal Design of Stand-Alone PV/ Wind Generator and Diesel System by Using Individual Particle Optimization Algorithm An Application of Wind Turbine Generator on Hybrid Power Conditioner to Improve Power Quality Design a Twelve Phase 1.1Mw Low Voltage HTS Motor for Marine Propulsion Systems Synthetic Loading of Interior Permanent Magnet Synchronous Motor and Effect of Nonzero Direct Axis Current Design, Prototyping, and Analysis of a Novel Permanent-Magnet Doubly Salient Generator Robust Backstepping Control of SynRM Drive System Using Adaptive Modified Elman Neural Network Uncertainty Observer Design Optimization and Numerical Analysis on the Magnetic Field of an Assisted Dc Field Exciting 18-12 Brushless Dc Motor Unconventional Motors Based on Vibration Motion Obtaining the Magnetic Characteristics of 15/10 and 9/6 Salient-Pole Brushless DC Machine: From 3-D FEM Analysis to the Experimental Tests Design and Analysis of a New Fuzzy Sliding Mode Observer for Speed Sensorless Control of Induction Motor Drive A Switched Reluctance Motor Driven Electric Scooter Using Novel Hybrid Modified Elman Neural Network Control System DSP Based Voltage and Current Modes Control of the Quasi-Z-Source Inverters for Electric Vehicles Power Loss Calculation and Thermal Analysis of PMA-SynRMServo System for Flywheel Energy Storage Applications Improvement of Internal Fault Detection Algorithms to Reduce Training Time of Back-Propagation Neural Networks for Transformer Differential Protection Schemes State-of-the-Art of Vanadium Redox Flow Battery: A Review on Research Prospects
International Review of Electrical Engineering - October 2012 (Vol. 7 N. 5) - Papers Part B
	Investigation of Optimal Power Flow Enhancement After Installing HVDC Links through Traditional and Evolutionary Optimization Algorithms Tuning of UPFC and PSS Parameters for Improvement of Power System Stability Using HSA Optimal Locating and Sizing of FACTS Devices in Smart Grid Environment Enhancing Failure Rate and Repair Time in Radial Distribution Network by Differential Evolution Algorithm Optimal Placement of Multi-Type FACTS Devices for Voltage Profile Enhancement Review of Simulated Annealing-Based Techniques for Power System Planning Enhancement of Interface Flow Margins Using Back-to-Back Converters in Power Systems Fault Location in Power Distribution Based on Travelling Wave Time-Domain and Frequency-Domain Analysis to Identify the Wave Front Voltage and Frequency Stabilization of Electrical Networks by Using Load Shedding Strategy Based on Fuzzy Logic Controllers dSPACE Based Adaptive Control Schemes for the Emergency Power Flow Controller in Microgrids Prior Distributions for Bayes Assessment of Photovoltaic Inverter Reliability and Availability Optimal Location of FACTS Controllers for Minimizing Severity of Overloading and Voltage Control Under Contingencies Dynamic Optimization Model of AGC Strategy Under CPS for Interconnected Power System DG Modeling Procedure Accounting for Power Output Correlation of Renewable Generators Quantitative Analysis of Power Loss Changes in Load, Generation, Storage and Distribution Sections of Different Microgrids Due to the DC Transition Pollution Emission Reduction with Minimum Transmission Loss in Power Dispatch Including Renewable Energy and Energy Storage STATCOM Based on Cascade H-Bridge Converter for Compensating Reactive Power and Current Harmonics Simultaneously Space Vector PWM Control Technique Applied in Dynamic Voltage Restorer for Power Quality Improvement Multiconductor Transmission Line Models for PQ and EMC Analysis of Railway Electrification Systems Posterior Distributions for Bayes Assessment of Photovoltaic Inverter Reliability and Availability HVDC Link and HVAC Transmission Line Comparison in Transmission Expansion Considering Social Welfare Maximization Distributed Generation Electricity Price Forecasting in a Deregulated Electricity Market Solution to Non-Convex Economic Power Dispatch Problems with Generator Constraints by Charged System Search Algorithm Cost Optimization of Power Generation Using A Differential Evolution Algorithm Enhanced with Neighbourhood Search Operation Solid-State Circuit Breaker Operation with Enhanced Commutation Circuit State of Charge Estimation for LiFePO4 Battery Using Artificial Neural Network Directional Calibration of Rogowski Coil for Localization of Partial Discharges in Smart Distribution Networks The Effect of Moisture and Temperature on Partial Discharge Behavior in New and Aged Oil/Pressboard Insulation System A Genetic Evolutionary Task Scheduling Method for Energy Efficiency in Smart Homes Binary Particle Swarm Optimization Selected Time-Frequency Features for Partial Discharge Signal Classification Study on Optimized Information Transmission Scheduling Strategy Oriented to Advanced Metering Infrastructure Application of a Photovoltaic Generation System in a Small-Scale Air Conditioner

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International Review of Electrical Engineering - Papers- Part A

Interleaved Bridgeless AC/DC Converter with High Power Factor
by Bor-Ren Lin, Po-Jen Cheng

Abstract - This paper presents an interleaved pulse-width modulation (PWM) converter to achieve the functions of high input power factor, low conduction loss and low current harmonics to meet the demand of EN61000-3-2 standard. In the adopted circuit, there are only two power semiconductors in line current path instead of three power semiconductors in a conventional boost converter. Thus the conduction losses on power semiconductors are decreased in the proposed circuit. The adopted converter can achieve the buck-boost voltage conversion such that the DC bus voltage can be less than the input voltage. The lower DC bus voltage can help to reduce the voltage stresses of power semiconductors in the second stage DC/DC converter. Interleaved pulse-width modulation (PWM) is used to further reduce the ripple currents at the input and output sides. The voltage doubler topology is adopted at the load side to double its output voltage in order to extend the useable energy of capacitor when the line voltage is off. Finally, experiments for a 750W prototype are provided to demonstrate the performance of the proposed converter.

Keywords: Power Factor Correction, Bridgeless Buck-Boost PFC, Continuous Conduction Mode.

Simple Three-Level Neutral Point Voltage Balance Control Strategy Based on Region Selection PWM
by Bo Gong, Shanmei Cheng, Yi Qin

Abstract - This paper proposes a novel neutral point balance strategy for three-level neutral-point-clamped (NPC) inverter based on region selection sinusoidal pulse width modulation (RS-SPWM). A voltage offset is added to the modulation wave in specific regions. The regions of SPWM correspond with these of space vector pulse width modulation (SVPWM) when the negative small voltage vectors are used as the first synthesis vector. Therefore, the RS-SPWM control strategy can be transplanted to SVPWM algorithm, the region selection method can be applied for both SVPWM algorithm and SPWM algorithm. The two strategies are shown to have similar control effects. Experimental results show the neutral point voltage balancing control strategies based on region selection PWM are effective.

Keywords: Three-Level Inverter, Neutral Point Voltage, Region Selection, PWM.

Random Modulation Schemes for Conducted-Emi Mitigation on Sepic Converter
by C. Krishna Kumar, Nirmal Kumar

Abstract - This paper proposes new random modulation schemes to mitigate conducted Electromagnetic Interference (EMI) in Single-ended Primary-inductor converter (SEPIC). The effectiveness of randomization on spreading the dominating frequency was studied by carrying out simulations using the MATLAB software and by estimating output power spectral density (PSD). Furthermore, the effect of using the proposed randomization techniques on conducted- EMI characteristics of the SEPIC converter is simulated and experimentally investigated. A comparative study has been carried-out to understand the effect of proposed schemes on PSD and conducted-EMI mitigation. Experimental results confirm the validity of the estimated and simulation results, and demonstrate the effectiveness of applying the randomization schemes in reducing the conducted-EMI. The class- B International special committee on Radio Interference (CISPR 22) standard has been adopted for measurements. Both simulated and measured results agree well, based on which Constant Trailing Edge, Randomized Duty ratio and Randomized Pulse Position Modulation with Fixed Carrier Frequency (CTERDRPPMFCF) scheme was contemplated for adoption.

Keywords: Conducted-EMI, Electromagnetic Interference, Power Spectral Density, Pulse Width Modulation, Randomized PWM.

Interleaved APWM Converter for High Voltage Applications
by Bor-Ren Lin, Shih-Kai Chung

Abstract -This paper presents an interleaved DC/DC converter for high input voltage applications. Two half-bridge converters and two split input capacitors are used in the primary side to reduce the voltage stresses of active switches at one-half of input DC voltage. These two half-bridge converters are operated by interleaved pulse-width modulation (PWM) to achieve load current sharing, reduce the current ripple on the output capacitor, and regulate the output voltage. Thus the capacitances at input and output sides can be reduced. In each half-bridge circuit, two forward converters with the same active switches are operated in parallel to reduce the current stresses of transformer windings and output filter inductors. The output sides of two converter cells are connected in parallel to reduce the ripple current on output capacitor and achieve load current sharing. Asymmetrical PWM (APWM) scheme is used to generate gate signals of MOSFETs and to regulate output voltage. Based on the resonant behavior by the output capacitance of active switches and the transformer leakage inductance, MOSFETs can be turned on at zero voltage switching (ZVS) during the transition interval. Finally, experiments with a 960W (24V/40A) laboratory prototype are provided to demonstrate the performance of proposed converter.

Keywords: Soft Switching, Asymmetric PWM, Interleaved PWM, ZVS.

Steady-State Error Elimination for Digital or Analog Implemented Sliding Mode Control in Single-Phase Shunt Active Power Filters
by Mihail Teodorescu, Dumitru Stanciu, Constantin Rădoi,Stefan G. Roşu, Andrei Savu

Abstract - In this paper the sliding mode control method of a single-phase shunt active power filter is studied and improved, offering solutions for steady-state error elimination. In order to calculate the integral function, for a digital control system implementation a mathematical calculation is considered and for a analog implementation the transfer function 1/(1+sτ) is used. The sliding surface, selection of sliding coefficients and equivalent control are analyzed. Sinusoidal line current is achieved even for distorted line voltage. Simulation and experimental results obtained with a digital controller board validate the theoretical assumptions.

Keywords: Active Power Filter, Sliding Mode Control, Steady-State Error.

An Improved High Power Factor-Soft Switched AC-DC Converter
by H. Bodur, S. Cetin

Abstract - In this study, an improved high power factor AC-DC converter with soft switching is proposed. In this high power factor-soft switched (HPF-SS) converter, main switch is turned on with zero voltage transition (ZVT) and turned off with zero voltage switching (ZVS). The auxiliary switch is turned on with zero current switching (ZCS) and turned off with ZVS. The main diode and all of auxiliary diodes are operating with SS. Also, in this converter, most of SS energy stored in the snubber inductance is transferred effectively to the output by a transformer, and so the current stress of the auxiliary switch is reduced significantly. In this converter, no semiconductor device has any additional voltage stress and SS operating conditions are maintained at very wide line and load ranges. The performance of proposed HPF-SS AC-DC converter is verified experimentally by a 1 kW and 100 kHz prototype, operating with universal line range.

Keywords: Power Factor Correction, AC-DC Converters, Active Snubber Cells, Soft Switching, Zero Voltage Transition.

Analysis, Design and Implementation of a New Soft Switching High Voltage DC Converter
by Bor-Ren Lin, Huann-Keng Chiang and Han-Che Chen

Abstract - This paper presents a new DC/DC converter with series-connected transformers in order to realize the functions of zero voltage switching (ZVS) for power switches, less transformer secondary winding and less output ripple current with a current double rectifier, and load current sharing for high input voltage applications. Two converter cells are connected in series at high voltage side to reduce the voltage stresses on active switches. Thus the voltage stress of each active switch is clamped at half of input DC voltage. The output sides of two converter cells are connected in parallel to reduce the ripple current on output capacitor and achieve load current sharing. The interleaved pulse-width modulation (PWM) scheme is used for control two converter cells to reduce the ripple current at the output capacitor such that the output filter inductors can be reduced. In each converter cell, two asymmetrical half bridge circuits with the same power switches are adopted to regulate the output voltage at the desired voltage level. Based on the resonant behavior by the output capacitance of active switches and the transformer leakage inductance, MOSFETs can be turned on at zero voltage switching (ZVS) during the transition interval. Finally, experiments with a laboratory prototype (24V/40A) are provided to demonstrate the performance of proposed converter.

Keywords: PDC-DC Converter, Soft Switching, Power Electronics.

New Resonant DC Link Inverter for Brushless DC Motor Drive with a Simple Auxiliary Circuit
by Mojtaba Khalilian, Adel Deris Zadeh

Abstract - Brushless DC motors are widely used in many industrial applications. These kinds of motors are usually driven with three phase hard switching inverter which causes high switching losses, high switching stress, high electromagnetic interference and low switching frequency. In order to overcome these drawbacks, in this paper, a new DC link soft switching inverter is proposed and is used for a brushless DC motor drive. The auxiliary circuit of the proposed inverter is composed of two auxiliary switches and theses switches are operated in soft switching condition. The auxiliary circuit provides soft switching conditions for main inverter switches. The analytical equations and operating modes of the presented inverter are explained in details. The design considerations are presented and the experimental results verify the theoretical analysis.

Keywords: Brushless DC Motor, Soft Switching, Zero Current Switching, Zero Voltage Switching, Quasi Resonant.

Minimum Time Current Control of Three-Phase PWM Rectifier with LCL Filter Interface
by Bo Long, Felipe P. Vista IV, Deok Jin Lee, Kil To Chong

Abstract - This paper proposes a minimum time current optimal controller for three-phase pulse width modulation (PWM) rectifier with LCL filter. The proposed scheme is realized by choosing the optimal control voltage for the current reference tracking with minimum time under the maximum voltage and maximum current limit constraint. The solutions of this optimization model are obtained by solving the Hamiltonian function. Simulation and experimental results demonstrate that the proposed optimal controller could achieve smaller transient current response time than the conventional synchronous proportional-integral (PI) controller, and performance of dc-link voltage is greatly improved, which, at the same time, could suppress DC-bus voltage variations by way of reactive current control.

Keywords: Optimal Controller, Hamiltonian Function, LCL Filter.

Implementation of a ZVS DC/DC Converter with Low Voltage Stress MOSFETs and without Output Inductor
by B. R. Lin, S. C. Huang

Abstract - A soft switching three-level DC-DC converter with two transformers is presented to achieve zero voltage switching (ZVS) for all power switches with a wide range of load condition and input voltage and to clamp the voltage stress of MOSFETs at Vin/2. The series-connected two transformers are adopted to extend the ZVS range of the lagging switches. Each transformer can be operated as an inductor to smooth the output current or a transformer to achieve electric isolation and transfer power from input side to output load. Thus, no output inductor is needed at the secondary side.
Due to the resonant behavior by the resonant inductance and resonant capacitance at the transition interval, power MOSFETs are turned on at ZVS. Experiments with a 1kW prototype are provided to verify the performance of proposed converter.

Keywords: ZVS, Without Output Inductor, DC-DC Power Conversion.

Real-time Low-Distortion Digital PWM Modulator for Switching Converters
by F. Chierchie, A. J. Soto, E. E. Paolini, A. R. Oliva

Abstract - A compensation scheme to reduce the inherent baseband distortion in uniform PWM modulators (UPWM) is presented in this paper. The method is based on real-time mapping of the switching times of UPWM to those of natural PWM that, as it is well-known, exhibits far less in-band distortion. Two alternatives are presented: one based on an exact, analytic algorithm recently reported in the literature, and another one that uses an artificial neural network (ANN). Both methods are designed for arbitrary, band-limited modulating signals and they are not restricted to single-frequency sinusoids, as other techniques presented in the literature. Simulation results and experimental measurements of a FPGA implementation demonstrate a significant reduction of the distortion in real-time applications. The performance of both alternatives is compared for several modulating signals, and the results of industry-standard distortion tests are also reported. Finally, some guidelines for choosing the best alternative for ASIC or FPGA implementations are provided.

Keywords: Field Programmable Gate Arrays, Harmonic Distortion, Pulse Width Modulation, Spectral Analysis, Switching Converters.

ZVS Asymmetrical Full-Bridge Buck Converter with Wide Input Voltage Range
by Hyun-Lark Do

Abstract - A zero-voltage-switching (ZVS) asymmetrical full-bridge buck converter is proposed. In the proposed converter, a clamping capacitor is connected across the 2nd bridge instead of the DC-blocking capacitor in the conventional asymmetric full-bridge buck converter. The output stage consists of a full-bridge diode rectifier and a LC output filter. The ZVS operation of all power switches is achieved. Therefore, switching losses are significantly reduced and high-efficiency is obtained. Also, the drawbacks of the conventional asymmetric full-bridge buck converter such as the limited maximum duty cycle and narrow input voltage range are overcome. Steady-state analysis of the proposed converter is presented. A laboratory prototype of the proposed converter is developed, and its experimental results are presented for validation.

Keywords: Full-Bridge Buck Converter, DC-DC Converter, Buck Converter, Zero-Voltage-Switching.

A Modulation Strategy for DC/AC Converter Based on Voltage Limitation Criterion
by Xiao Xi, Kang Qing, Zheng Zedong, Zhu Ziqiang

Abstract - TIn this paper, a pulse-width modulation (PWM) method based on the voltage limitation criterion (VLCPWM) is presented. This method analyzes the desired values of phase voltages and the output voltage limitation of voltage source inverter (VSI), and the PWM duty cycles are then obtained directly. Compared with the other methods such as space vector PWM (SVPWM) and sinusoidal PWM (SPWM), this method results in high voltage utilization ratio and is simple to realize since it does not need complex coordinate transformation or trigonometric function computation. In this method, the smallest average common-mode voltage is used under the condition of full DC-bus voltage utilization. The over-modulation can be realized automatically. The effectiveness of the proposed method is verified by the simulation and experimental results.

Keywords: PWM, Voltage Limitation Criterion, Common-Mode Voltage, Voltage Utilization Ratio.

Input Power Factor Control of RB-IGBT Based Indirect Matrix Converter
by Kai Sun, Xiaonan Lu, Lipei Huang

Abstract - The topology and control method of indirect matrix converter (IMC) based on RB-IGBT is discussed in the paper. The space vector pulse width modulation (SVPWM) is employed on both of the rectifier stag and the inerter stage. The adjustment method of input power factor is developed based on the input current SVPWM of the rectifier stage. According to the polarity requirement of dc-link voltage, the regulation range of input displacement angle is determined. In addition, the influence of input LC filter on input power factor is analyzed. The calculation formula of input power factor angle at the grid side is presented. Simulation and experimental results validate the theoretical analysis.

Keywords: Indirect Matrix Converter, SVPWM, Input Power Factor, Input Displacement Angle.

An Integrated Derived Boost-Flyback Converter with High Step-Up Conversion Ratio
by Kuo-Ching Tseng, Chi-Chih Huang, Ming-Wei Huang

Abstract - This paper presents an Integrated Derived Boost-Flyback Converter (IDBFC) for high step-up conversion. The circuit topology combines derived boost and flyback converters utilizes a coupled-inductor and a voltage-lift capacitor to achieve a high step-up gain. The proposed converter functions as an active clamp circuit, which alleviates large voltage spikes across the power switches. Thus, the low-voltage-rated MOSFETs can be adopted for reductions of conduction losses and cost. Efficiency improves because the energy stored in leakage inductances is recycled to the output terminal. The primary or secondary side can increase the number of series and parallels to achieve higher voltage gain. Finally, the prototype circuit with a 36- V input voltage, 400- V output, and 500- W output power is operated to verify its performance, and the resulting waveforms and efficiency curves are presented and discussed.

Keywords: DC-DC Converter, Boost-Flyback Converter, High Step-Up.

Analysis and Design of LCCL Load Matching Circuit for High-Frequency Induction Heating Series Resonant Inverter
by Z. J. Zhang, N. W. Bergmann, H. M. Li

Abstract - An LCCL load matching electrostatic coupling approach for high-frequency induction heating series resonant inverters (SRI) is proposed. The new method has a high efficiency by replacing the commonly used heavy and expensive output transformer in high-frequency induction heating SRI. Secondly, this approach could be used in low load quality factor situations. In this paper, the LCCL resonant circuit topology and electrical characteristics are analyzed in detail. The design scheme for LCCL load matching method is then presented. The LCCL voltage-fed high-frequency single phase full-bridge power supply prototype is designed and tested using an FPGA as the main controller. The experimental results validate the proposed approach.

Keywords: Electrostatic Coupling, Load Matching, Series Resonant Inverter, Induction Heating, Electromagnetic Coupling.

A Novel Grid Connected Multi-Input Direct DC-AC Converter
by Z. J. Zhang, N. W. Bergmann, H. M. Li

Keywords: Electrostatic Coupling, Load Matching, Series Resonant Inverter, Induction Heating, Electromagnetic Coupling.

Analysis on The Harmonic Components of Torque Characteristics of Single Phase Single Stator Small Size Brushless DC Permanent Magnet Motor: Series and Parallel Magnetic Circuit
by R. N. Firdaus, M. Norhisam, I. Aris, N. Mariun, M. Nirei, H. Wakiwaka

Abstract - This paper present the analysis on harmonics components of torque characteristics of single phase single stator small size Brushless DC permanent magnet motor (BLDC). The main objective of this paper is to analyze the harmonic components of the torque characteristics due to optimal air gap flux density and proposed serial magnetic circuit as alternative to parallel magnetic circuit in this BLDC. A sinusoidal torque characteristic is evolved by varying the taper parameter. Finite Element Analysis (FEA) is used to simulate the torque characteristics based on various combinations of taper parameters. The result shows that minimum value of THD can be found by optimizing the width of slot and rotor. Also it is found that with reducing height of stator teeth a smoother torque waveform can be achieved. The proposed series magnetic circuit improves the magnetic energy distribution and thereby more torque is being produced. For extensive evaluations, torque density on the proposed series and parallel magnetic circuit are compared with a fabricated motor. Finally, this paper shows the advantages of using serial magnetic circuit and the possibility of choosing the taper parameter in designing this kind of BLDC.

Keywords: Single Stator, Brushless DC Motor, Series Magnetic Circuit, Parallel Magnetic Circuit, BLDC, Harmonic Components.

A New Approach for the Magnetic Characterization of Iron Core Materials - The Case of a Switched Reluctance Motor
by D. S. B. Fonseca, N. M. F. Pinto, A. J. M. Cardoso, C. M. P. Cabrita

Abstract - The study of magnetic materials characteristics is an important issue in Electrical Engineering Education. On the other hand, Electrical Engineering students should be familiar with the use of the most important computer tools in this domain.
Usually, to obtain the magnetization characteristic of a given material, a magnetic core with a very simple geometry is built, with both an excitation coil and a search coil. From the waveforms analysis of both the excitation coil current and the search coil induced electromotive force; it is possible to draw the magnetization curve.
This paper reports on the experiments concerning a new methodology for the magnetic materials characteristic determination. The proposed method uses both laboratory results and finite element analysis, combined with Matlab® software supervision, and allows the magnetic characterization of a material arranged in such a complex geometry unable to be easily performed analytically.

Keywords: Electrical Engineering Education, Magnetic Material’s Characterization.

Design and Implementation of an Extension Robust Controller for Switched Reluctance Motor Drives
by K. H. Chao, P. Y. Chen

Abstract - The main purpose of this paper is to develop an extension robust speed controller using digital signal processor (DSP) for a converter-fed switched reluctance motor (SRM) drive. First, the dynamic model of a converter-fed switched reluctance motor (SRM) drive is established. Then a two-degree-of-freedom controller (2DOFC) for an ideal switched reluctance motor (SRM) drive at nominal case is designed. As the variations of system parameters and operations occur, a compensation signal is yielded by an extension robust controller (ERC) to preserve the prescribed speed control response. The compensation signal is adaptively tuned by a model following error driven extension weighting controller. Effectiveness of the proposed controller is verified by some simulation and measured results.

Keywords: Extension Robust Speed Controller, Converter-fed Switched Reluctance Motor (SRM) Drive, Digital Signal Processor (DSP), Model Following, Extension Theory.

Effect of the Static Air-Gap Eccentricity & Stator Inter-Turn Short Circuit Composite Fault on the Generator Circulating Current Characteristics
by Yuling He, Guiji Tang, Shuting Wan, Yucai Wu

Abstract - This paper investigates the stator circulating current characteristics under the static air-gap eccentricity & stator inter-turn short circuit composite faults, and the effect of the faulty parameter development on the circulating current. The air-gap magnetic flux density is firstly deduced, based on which the electromotive force (E.M.F.) difference between the two parallel-branches is obtained. Then the harmonic characteristics of the circulating current, also the relationship between the faulty parameters and the circulating current are investigated. Finally, the experiments are taken on a SDF-9 fault simulating generator to verify the theoretical analysis. The result shows that there will be circulating current of 1st and 3rd harmonics induced inside the parallel-branch loop under the composite faults.
Moreover, the development of the stator inter-turn short circuit, the increment of the static air-gap eccentricity, and the rise of the exciting current will all make the 1st and 3rd harmonic components of the circulating current increased. The investigation presented in this paper will be beneficial to the failure criterion and the diagnosis of the static air-gap eccentricity & stator short circuit composite fault of turbo-generator.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Turbo-Generator, Static Air-Gap Eccentricity, Stator Inter-Turn Short Circuit, Composite Fault, Circulating Current Characteristics.

Adaptive Modified Elman Neural Network Integral Backstepping Control for a PMLSM Drive System
by Chih-Hong Lin

Abstract - The good control performance of the permanent magnet linear synchronous motor (PMLSM) drive system is very difficult achieved by using linear controller due to the uncertainty effects. An adaptive modified Elman neural network (ENN) integral backstepping control system is proposed to increase the robustness of the PMLSM drive system. Firstly, the field-oriented mechanism is applied to formulate the dynamic equation of the PMLSM drive system. Secondly, an integral backstepping approach is proposed to control the motion of PMLSM drive system. With proposed integral backstepping cotrol system, the mover position of the PMLSM drive possesses the advantages of good transient control performance and robustness to uncertainties for the tracking of periodic reference trajectories. Because the dynamic characteristics and motor parameters of the PMLSM are nonlinear and time-varying, an adaptive modified ENN uncertainty observer is proposed to estimate the required lumped uncertainty to further increase the robustness of the PMLSM drive system. The on-line parameter training methodology of the adaptive modified ENN can be derived using adaptive laws based on Lyapunov stability theorem. Then, a sigmoid function is adopted in the hidden layer of the modified ENN to facilitate hardware implementation. Finally, the effectiveness of the proposed control system is verified by experimental results.

Keywords: Permanent Magnet Linear Synchronous Motor, Modified Elman Neural Network, Integral Back stepping Control.

Conversion of Standard Induction Machines to Permanent Magnet Synchronous Machines with Higher Efficiency
by Isabelle Hofman, Peter Sergeant, Alex Van den Bossche

Abstract - To increase the efficiency of commercial induction machines, especially at part load and speed, these machines are converted into permanent magnet synchronous machines. The stators are not changed at all; only the rotors are modified. The appropriate size of the rotor iron and the magnets is found by a numerical optimization, using finite element software. The parameters that are optimized are: the magnet thickness (t_m), the number of magnet segments per pole (N_ps) and the magnet pole angle (α_m). The objectives are high efficiency, low magnet volume, low cogging torque and with sufficient mechanical power. The high robustness and reliability of the original induction machines remain high because the stators, the shafts and the bearings are not modified. The resulting synchronous machines still have a rather low torque to weight ratio, but they have low rotor losses, a good power factor and high efficiency. A financial analysis is made in order to assess if the payback time of the conversion is reasonable.
Two induction machines with approximately the same outer dimensions (a 2-pole 3 kW machine and a 6-pole 1.5 kW machine) were converted into synchronous machines by different production techniques for the rotor. The efficiency maps were simulated and measured. For both machines, the peak efficiency increases by 5% and 10% respectively, and the average efficiency (between 0.5 and 1 times nominal torque, and 0.5 and 1 times nominal speed) by 4% and 14%, while the cogging torque and magnet volume are low. Conversion of induction machines with many poles to synchronous machines improves the efficiency much more than conversion of two-pole induction machines.

Keywords: Asynchronous Machines, Induction Motors, Losses, Permanent Magnet Machines.

Optimal Design of Stand-Alone PV/ Wind Generator and Diesel System by Using Individual Particle Optimization Algorithm
by A. Ahmari-Nezhad, A. Abbaspour-Tehrani-Fard, M. Ehsan, M. Fotuhi-Firuzabad, M. Abroshan

Abstract - In this paper an optimized wind/PV hybrid system with battery and diesel backup is designed. As a result of this study the costs of the hybrid system will be minimized in its 20-year life time.
The optimization is done by considering the annual load increase and fuel cost rise. This Optimization is subject to load covering and minimizing the total cost. The total cost entailed maintenance, equipment and diesel fuel consumption substitution. An advanced variation of individual particle optimization algorithm (IPO) is used to solve the optimization problem.

Keywords: Hybrid Systems, Renewable Power System, Individual Particle Optimization.

An Application of Wind Turbine Generator on Hybrid Power Conditioner to Improve Power Quality
by Narin Watanakul

Abstract - This article applies wind turbine generator by the Salient Permanent Magnet Synchronous Generator (PMSG) for compensation low voltage distribution power system. The wind turbine generator combining with a dynamic voltage restorer (DVR) in order to compensate the voltage variation in the electrical power system. The proposed system consists of wind energy system whose maximum power is equal to 5 kWp. The electrical energy form wind turbine system supplies the DVR, which is controlled by four-wire bidirectional boost converter for regulating the DC link voltage at 440 V. While, the DVR consists of three-level neutral point clamped (NPC) inverter. The control system of the DVR is based on In-phase compensation technique, which controls the NPC inverter producing the sinusoidal voltage. The compensated voltage variation is inversely proportional to source voltage and injected voltage, the power source voltage of parallel transformer (output voltage 0.5 per unit (pu.)) though the series transformer (producing injected voltage 0.5 per unit (pu.)),adding with the output load voltage 1.0 per unit (pu.). Of this principle will result the system that can deliver electrical power of 50 percentage of normal voltage condition, and one hundred percent during a power outage. The prototype DVR is built and tested in laboratory. In the test cases, the depletion of power quality is monitored both in unbalanced voltage sags / interruption cases. The data collected by MATLAB simulation are used in comparison with the experimental results. This provides guideline to further analyze and improve power conditioning in electrical system pertinent to wind turbine generator.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Power Conditioners, Power Quality, Dynamic Voltage Restorer(DVR), Wind Turbine Generator, Permanent Magnet Synchronous Generator(PMSG), Voltage Sags/ Interruption, In-Phase Compensation, Neutral Point Clamped NPC Inverter.

Design a Twelve Phase 1.1Mw Low Voltage HTS Motor for Marine Propulsion Systems
by M. Kashani, M. Hosseina, A. Darabi

Abstract - Recently the high temperature superconducting technology has been developed. This matter attracts propulsion electric motor designers' attentions. Specially, as a result significant capabilities of the HTS motors, such as lower electrical losses, the conventional propulsion motors are supposed to be replaced by superconducting ones in early future. In HTS motors, conventional copper windings are replaced by superconducting tapes. A cryogenic system is also equipped to decrease the temperature until the superconducting state is achieved. Considering all types of superconducting motors, there is an agreement between HTS engineers on this point that synchronous motors with superconducting field windings have higher power density, lower noise, higher life time and also more cost saving. These reasons made us think about designing an appropriate HTS synchronous motor for marine propulsions which can be adapted with marine applications inherent limitations. In this paper, a marine propulsion synchronous motor with high temperature superconducting (HTS) field winding was designed initially, and then electromagnetic analysis was performed. A proper cooling structure and a practical HTS power supply were designed for the model respectively.

Keywords: Synchronous Motor, HTS Field Windings, Cooling Structure.

Synthetic Loading of Interior Permanent Magnet Synchronous Motor and Effect of Nonzero Direct Axis Current
by Seyed Jafar Salehi

Abstract - The application of the synthetic loading technique to interior permanent magnet (IPM) synchronous machines is investigated. Mathematical equations for synthetic loading are developed. From the equations, a quadrature-axis current algorithm is proposed from which rotor speed and the stator direct- and quadrature-axis voltage and current equations are derived. The impact that synthetic loading frequency has on the dc-link voltage and the inverter phase-leg volt-ampere rating are analyzed. This shows that the synthetic loading technique requires an increased dc-link voltage and inverter volt-ampere rating compared to the standard efficiency test method. Synthetic loading is verified experimentally using a IPM synchronous machine. Simulation and experimental results are compared with the standard efficiency test. The simulation and the experimental results show that the synthetic loading technique is capable of evaluating the losses in the IPM synchronous machine.

Keywords: Efficiency Test, Interior Permanent Magnet Synchronous Machine, Synthetic Loading.

Design, Prototyping, and Analysis of a Novel Permanent-Magnet Doubly Salient Generator
by H. Bahrami, M. Mirsalim, A. R. Taheri, S. Saeedi Tehrani

Abstract - This paper presents the design, prototyping, and analysis of a novel permanent-magnet doubly salient generator. The excitation of the machine is carried out by neodymium-iron-boron magnets. This generator has two stators and two rotors, each of them also have four poles and two poles respectively. The rotors are shifted forty-five degrees in space with respect to each other to prepare full energy in each cycle. This leads to a lower voltage ripple after rectification. Moreover, by using the two-pole rotor, which leads to lower core losses, this generator can be used for high-speed applications. Finite element analysis of this generator is carried out to investigate the magnetic field distribution at different rotor positions and load currents. To verify the theoretical results, a prototype has been constructed and tested. The experimental results are in good agreement with the theoretical results.

Keywords: Doubly Salient, Design, Finite Element Analysis, Generator, High Speed, Permanent Magnet, Prototype.

Robust Backstepping Control of SynRM Drive System Using Adaptive Modified Elman Neural Network Uncertainty Observer
by Chih-Hong Lin

Abstract - Due to simple construction with convex effect, the synchronous reluctance motor (SynRM) drive system has highly nonlinear uncertainties. The accurate mathematic models are difficult to be established for time-varying and nonlinear uncertainties of the actual SynRM drive system. In this paper, the robust backstepping control system using an adaptive modified Elman neural network (ENN) uncertainty observer for a SynRM drive system is proposed to achieve the better performance and robustness. Firstly, the field-oriented mechanism is applied to formulate the dynamic equation of the SynRM drive system. Secondly, the backstepping approach is proposed to control the motion of SynRM drive system. With proposed integral backstepping control system, the rotor position of the SynRM drive possesses the advantages of good control performance and robustness to uncertainties for the tracking of periodic reference trajectories. Moreover, to further increase the robustness of the SynRM drive system for nonlinear uncertainties, an adaptive modified ENN uncertainty observer is proposed to estimate the required lumped uncertainty. The on-line adaptive law of the modified ENN is derived in accordance with Lyapunov function. The updated parameters of the modified ENN are used by the gradient descent method and the backpropagation algorithm. Finally, the effectiveness of the proposed control scheme is verified by some experimental results.

Keywords: Synchronous Reluctance Motor, Modified Elman Neural Network, Backstepping, Lyapunov Function.

Design Optimization and Numerical Analysis on the Magnetic Field of an Assisted Dc Field Exciting 18-12 Brushless Dc Motor
by Hassan Moradi, Ebrahim Afjei

Abstract - This paper presents the design optimization and accurate electromagnetic field analysis of an 18-12 there phase Brushless dc motor (BLDCM) by using a two-dimensional Finite-Element analysis. Proposed motor will provide a wide range of air-gap flux control by a dc assisted field winding which is replaced with the permanent magnet in the rotor structure. In proposed BLDCM a simple dc current control is used and no brushes or slip rings are required to perform this control. Physical dimensional of understudy 18-12 BLDCM configuration are optimized to obtain required electric and magnetic characteristic. To evaluate the motor performance, the numerical technique has been utilized and obtained results have been compared with those obtained from analyzed a 9-6 BLDCM configuration. In the numerical part, 2-D Finite Element (FE) analysis has been carried out using a MagNet CAD package (Infolytica Corporation Ltd.) for two type of BLDCM to confirm the accuracy and the efficacy of the proposed design procedure. The analysis results demonstrate the effectiveness of the proposed machine design methodology.

Keywords: FE Analysis, Field Analysis, Brushless Dc Motor.

Unconventional Motors Based on Vibration Motion
by M. Rata, G. Rata, D. Cernomazu, L. Mandici, C. Afanasov

Abstract - The vibromotors are part of the unconventional electrical motors, which convert alternative vibration motion in a continuous motion linear or rotational. The vibromotor rotor is typically in direct contact with the stator, which offers a very good dynamic quality in transient motion conditions (i.e., in start-stop and stepping regimes), because the vibrating element becomes a brake during power supply switching off. In many fields of application, vibromotors solve the problems of positioning and uniform high-speed displacements, and execute prescribed motions. This paper presents some constructive variants of vibromotors, which operate using “Marinescu oscillomotor” principle. These vibromotors usually work on an industrial frequency. The experimental results of vibromotors, which are powered by a mono-phase inverter, are also presented. This inverter may also adjust both the frequency and the duty-cycle.

Keywords: Friction, Motion Control, Motors, Oscillators, Vibration Measurement.

Obtaining the Magnetic Characteristics of 15/10 and 9/6 Salient-Pole Brushless DC Machine: From 3-D FEM Analysis
to the Experimental Tests
by Hassan Moradi, Ebrahim Afjei

Abstract - This paper describes the magnetic characteristics and comprising results of two 15-10 and 9-6 salient pole brushless dc machine with concentrated stator winding which does not use a permanent magnet in the rotor. The permanent magnet is replaced with assisted field coil in the rotor. To evaluate the generator performance, numerical analysis for both 15-10 and 9-6 Salient-Pole structure have been utilized. In the numerical analysis, 3-D Finite Element (FE) analysis has been carried out to confirm the accuracy of the predicted flux-linkage characteristics and, also an improved 3-D hybrid method coupling the FE method and boundary integral equation method to confirm the accuracy of the 3-D FE analysis has been carried out. Afterward, a series of experimental tests are performed to obtain the magnetic characteristics of the 9/6 configuration machine, comparing, correcting, and discussing the results with those of 3-D FEM analysis.

Keywords: Salient Pole Machine, Brushless DC Generator, Finite Element Analysis, Flux-Linkage Characteristic.

Design and Analysis of a New Fuzzy Sliding Mode Observer for Speed Sensorless Control of Induction Motor Drive
by N. Benharir, M. Zerikat, S. Chekroun, A. Mechernene

Abstract - The subject of the paper is the implementation of fuzzy sliding mode control conception for robust accurate tracking of induction motor drive operating in a high-performance drives environment. The introducing of fuzzy sliding mode in the control system helps to achieve a good dynamic response, disturbance rejection and low to plant parameter variations of the A.C drive. The fuzzy sliding mode controllers combine the advantages of both fuzzy controllers and sliding mode controllers. By combining variable structure systems theory and fuzzy logic concept, a new algorithm is developed. The proposed control scheme can drive the dynamics of controlled system into a designed sliding surface in finite time and guarantee the property of asymptotical stability. The synthesis of sliding mode control and the control laws for the controls of speed are described. In order to verify the performances of the proposed observers and control algorithms and to test behavior of the controlled system, numerical and real experiments are achieved. to demonstrate the potential and practicality of the presented approaches.

Keywords: Sensorless Speed Control, Sliding Mode Observer, Fuzzy Logic Control, Induction Motor, High- Performance.

A Switched Reluctance Motor Driven Electric Scooter Using Novel Hybrid Modified Elman Neural Network Control System
by Chih-Hong Lin

Abstract - Since the electric scooter driven by switched reluctance motor (SRM) has nonlinear and time-varying characteristics, it is difficult to establish an accurate dynamic model for designing a linear controller. In order to overcome this problem, a novel hybrid modified Elman neural network (ENN) control system is proposed to control for SRM driven electric scooter. The novel hybrid modified ENN control system consists of a supervisor control, a modified ENN and a compensated control with adaptive law. Moreover, the novel hybrid modified ENN control system is developed to reduce torque ripple and raise robustness for uncertainties. The on-line parameter training methodology of the modified ENN can be derived using adaptive laws and the Lyapunov stability theorem. The modified ENN has the on-line learning ability to respond to the system’s nonlinear and time-varying behaviors. Finally, to show the effectiveness of the proposed control scheme, comparative studies with supervisor control system are demonstrated by experimental results

Keywords: Switched Reluctance Motor, Modified Elman Neural Network, Lyapunov Stability.

DSP Based Voltage and Current Modes Control of the Quasi-Z-Source Inverters for Electric Vehicles
by Ping Liu, Heping Liu,Qiang Guo

Abstract - Two strategies of peak DC-link voltage control of the voltage-fed quasi-Z-Source inverters (qZSI) are presented. Both strategies are digitally implemented using a DSP based direct digital design approach, where the real-time workshop (RTW) is used for automatic real time code generation for a TMS320F2808 DSP.
Voltage mode (VM) and current mode (CM) controls are derived based on the dynamic ideal small-signal model of the quasi-Z-source network with inductive load. In VM and CM, the DC-link voltage is controlled by measuring the two capacitor voltages of qZSI, and proper compensators are designed digitally employing the bode diagram and discrete-time frequency response approaches. The performance of the proposed control strategies are verified by experimental results for reference voltage changes, input voltage and load disturbances.

Keywords: Quasi-Z-Source Inverters, DC-Link Voltage Control, Voltage Mode, Current-Programmed Mode, Direct Digital Control, Digital Signal Processor, Real Time Workshop.

Power Loss Calculation and Thermal Analysis of PMA-SynRM Servo System for Flywheel Energy Storage Applications
by Hossein Azizi, Abolfazal Vahedi

Abstract - In this paper the electromagnetic and thermal analysis of permanent magnet assisted synchronous reluctance machine (PMA-SynRM) is presented for flywheel energy storage applications. The 2D-FEM thermal model is used to evaluate the transient and steady stated thermal behavior of PMA-SynRM under different operating conditions. The transient coupled load finite element analyses are performed to approximate the value of power loss in different part of machine. The dimensionless empirical heat transfer correlations analysis is used to predict the heat transfer coefficient of all convection surfaces in the machine. The temperature distribution of individual components in the motor is obtained after the thermal analysis. The effect of the fluid velocity and external frame manufacturing on heat exchange and overload capability of PMA-SynRM is studied.

Keywords: Thermal Analysis, Flywheel Energy Storage, Finite Element, Permanent Magnet Assisted Synchronous Reluctance Machine.

Improvement of Internal Fault Detection Algorithms to Reduce Training Time of Back-Propagation Neural Networks for Transformer Differential Protection Schemes
by S. Bunjongjit, A. Ngaopitakkul

Abstract - This paper presents an algorithm based on a combination of Discrete Wavelet Transforms (DWT) and back-propagation neural networks for detection and classification of internal faults in a two-winding three-phase transformer. Fault conditions of the transformer are simulated using Electromagnetic Transients Program (EMTP) in order to obtain current signals. The training process for the neural network and fault diagnosis decision are implemented on MATLAB. In addition, the initial number of neurons for the first hidden layer to decrease duration time of train process is taken into account. Various cases based on Thailand electricity transmission and distribution systems are studied to verify the validity of the proposed algorithm. A comparison between the proposed technique and conventional training is presented. The result is shown that the proposed technique is very effective in reduce training time and gives a satisfactory accuracy.

Keywords: Wavelet Transform, Transformer, Neural Network, Differential Relay, Internal Fault.

State-of-the-Art of Vanadium Redox Flow Battery:A Review on Research Prospects
by Mohd R. Mohamed, Hamzah Ahmad, Mazrul N. Abu Seman

Abstract - A significant research in redox flow battery (RFB) has been carried out by numerous researchers; some are under field testing and demonstration stage, yet several technological challenges remain in the optimisation and improvement of current RFB. This paper deals with the state-of-the-art redox flow battery (RFB), focusing on vanadium-based electrolytes. A broad review on energy storage technologies is first presented to bring RFBs system into perspective. Subsequently, discussion focuses on vanadium-based RFB (V-RFB) with regards to justifying the motivation factors for choosing V-RFB as a system to be studied. Research potential and challenges for V-RFB system are also discussed in detail.

Keywords: Redox Flow Battery, Vanadium, Energy Storage, Hybrid Electric Vehicle.

International Review of Electrical Engineering - Papers- Part B

Investigation of Optimal Power Flow Enhancement After Installing HVDC Links through Traditional and Evolutionary Optimization Algorithms
by A. Rahiminejad, A. Alimardani, S. H. Hosseinian, M. Rahmatian

Abstract - The effect of HVDC transmission lines on optimal power flow (OPF) in a power system considering different objective functions is discussed. Four objective functions are defined for OPF problem based on fuel emission, power loss, generation cost regarding valve effect and voltage deviation. In this study, besides a traditional optimization method, different evolutionary optimization algorithms are applied to the AC-DC OPF problem. The results are compared with the OPF results obtained for the same power system without HVDC transmission line to demonstrate the effect of HVDC transmission systems on OPF. The optimization process is mainly based on differential evolution (DE) algorithm and the results of the proposed method are also compared with the results of mixed-integer nonlinear programming (NLP) method as a traditional one, shuffled frog leaping algorithm (SFLA), and three versions of particle swarm optimization (PSO) method while all the constraints are satisfied. The system under study is the IEEE 30-bus system. As more than one objective function is considered, fuzzy strategy is also embedded into the optimization algorithm regarding its advantages for handling multi-objective optimization problems. The comparison expresses the effect of HVDC transmission lines on OPF and the efficiency of DE as a method for AC-DC OPF.

Keywords: AC-DC Optimal Power Flow (AC-DC OPF), HVDC Transmission Lines, Differential Evolution (DE) Algorithm, Multi-Objective Optimization.

Tuning of UPFC and PSS Parameters for Improvement of Power System Stability Using HSA
by M. Sedighizadeh, M. Hamidian, A. Rezazadeh

Abstract - In this paper, a control method based on simultaneous adjustment of all control coefficients for Unified Power Flow Controller (UPFC) and Power System Stabilizer (PSS) is proposed. Harmony Search Algorithm (HAS) has been used for parameter optimization. Studies in time and frequency domains for single machine infinite bus power system in different working conditions are performed.
In the control system, local state variables are chosen as inputs to control blocks and simultaneous adjustment of control parameters carried out through HSA algorithm led to interesting results and some advantages over the control systems used previously in similar settings. Different scenarios are simulated in this study and compared to the proposed control system using the characteristics of the objective function in time domain and the position of system poles in frequency domain. The efficiency of the proposed system is demonstrated under different conditions for disturbance and variations of loads in the simulation.

Keywords: UPFC, PSS, Small Signal Disturbance, Harmony Search Algorithm, Improvement of Damping.

Optimal Locating and Sizing of FACTS Devices in Smart Grid Environment
by A. Sharifi Nasab Anari, R. Ghadiri Anari, Y. Ramezani

Abstract - It is expected that in the future of power systems an augmented level of intelligence and integration of new technologies in every aspect of the power grid be involved. In Such condition, intelligent optimization techniques arise as the only reliable and suitable tool to be used for optimal designs in such smart grid. This paper presents Shuffled Frog Leaping Algorithm (SFLA) to obtain the optimal location and parameters of Unified Power Flow Controller (UPFC) in smart grid environment. UPFC has great flexibility that can control the active and reactive power flow and bus voltages, simultaneously. UPFC is applied to maximize the system loadability subject to the transmission line capacity limits. The results of the proposed optimization problem are compared to Harmony Search algorithm (HSA) and Clonal Selection Algorithm (CSA) that they were evaluated previous studies. These results are compared with those obtained from SFLA to show the effectiveness of the proposed method in finding the best solution for the optimization problem. The proposed approach is conducted and tested on IEEE 9-bus and IEEE 14-bus test systems in smart grid environment. The results show that the loadability of the power transmission system can be effectively enhanced through the optimal location and proper parameters selection of the UPFC.

Keywords: Power System Loadability, Unified Power Flow Controller (UPFC), Shuffled Frog Leaping Algorithm (SFLA), Harmony Search Algorithm (HSA), Clonal Selection Algorithm (CSA).

Enhancing Failure Rate and Repair Time in Radial Distribution Network by Differential Evolution Algorithm
by A. Khodadadi, M. Sadeghi Gogtapeh, S. S. Vakili

Abstract - In this paper a numerical method is used to optimize the failure rate and repair time of a five parts radial distribution network. Failure rate and repair time are effective parameters in customer oriented indices of reliability. Decrease of these two parameters improves reliability indices, thus, system stability will be boost. Failure rate and repair time defined by penalty functions. The penalty functions indirectly reflect the cost of investment which spent to improve these indices. The differential evolution algorithm is a population based evolutionary algorithm which has been used to optimize the failure rate and repair time of typical radial distribution network. Boundary limitations and inequities constraint of these parameters is considered in differential evolution algorithm. The differential evolution algorithm implemented by Matlab , optimized failure rate and repair time obtained.

Keywords: Optimization, Differential Evolution Algorithm, Failure Rate, Repair Time, Radial Distribution Networks.

Optimal Placement of Multi-Type FACTS Devices for Voltage Profile Enhancement
by A. Subramanian, G. Ravi

Abstract - This paper presents a new method for optimal placement of multi-type FACTS devices with a view to minimize load voltage deviations and network losses using biogeography based optimization. The strategy uses three types of FACTS devices that includes static VAR compensator, thyristor controlled series compensator and unified power flow controller; and offers optimal locations for placement, type and parameters of the FACTS devices. Test results on IEEE 14, 30 and 57 bus systems reveal the superiority of the algorithm.

Keywords: Biogeography Based Optimization, FACTS Devices.

Review of Simulated Annealing-Based Techniques for Power System Planning
by Huo-Ching Sun, Yann-Chang Huang

Abstract - This paper reviews various simulated annealing (SA)-based methods for the planning, operation, and optimization of power systems, including relevant recent and historical developments. Relevant publications in international journals that cover a broad range of applications of SA methods to solving problems of power system planning are reviewed. As is well known among power engineers, many kinds of combinatorial optimization problems arise in the planning and operation of power systems, including generation expansion planning, transmission expansion planning, generator maintenance scheduling, unit commitment, load forecasting, economic dispatch, reactive power planning, and the other applications. In this paper, articles that have been published in international journals on the use of simulated annealing (SA), tabu search (TS), genetic algorithm (GA), evolutionary programming (EP), artificial intelligence (AI), and combinations relation to power system planning are systematically reviewed.

Keywords: Power System Planning, Simulated Annealing-Based Techniques.

Enhancement of Interface Flow Margins Using Back-to-Back Converters in Power Systems
by Hwachang Song, Sungmin Ohn, Byonghoon Jang

Abstract - This paper discusses the enhancement of interface flow margins of power systems using Back-to-Back (BtB) converters. The interface flow margin is a measure of how much additional active power can be transferred from the external regions to the study region of interest, satisfying the power flow equations. BtB converters are series-type equipment that mainly controls active power injection through them. The establishment of BtB converters onto transmission lines can decrease the fault current level of the alternate current (AC) power network due to the decoupling effect by their direct current (DC) links. This paper employs FV (Interface Flow-Voltage) analysis to determine interface flow margins for the study systems with BtB converters and evaluates the controllability of BtB converters on candidate locations by observing the margin enhancement sensitivities. Furthermore, the paper provides an optimization formulation for adequately setting BtB parameters using the sensitivity information to satisfy the given criterion of interface flow margins.

Keywords: Back-To-Back Converter, FV Analysis, Interface Flow Margins, Margin Enhancement, Parametric Sensitivity.

Fault Location in Power Distribution Based on Travelling Wave Time-Domain and Frequency-Domain Analysis to Identify the Wave Front
by Rui Liang, Joseph Sottile, Zheng Jin

Abstract - Time difference determination between the reflected waves from fault and other special points is a key point while using single terminal travelling wave to realize the single-phase earth fault locating, the accurate identification of the wave fronts from special points has not yet been solved well. In this paper, as the first step, the characteristic frequency associated to fault point is determined to get a relatively accurate fault distance from the measurement point based on analysis on transient signal originated from fault point by waveform-inferred mother wavelets at frequency domain. Then the fault distance got from former step is used as a clue for Daubechies(Db) wavelet analysis at time domain, arrival time of the wave fronts from the far terminal bus is accurately identified, then a more accurate fault location is achieved by time differences between initial wave front from fault point and that from far terminal bus of the fault feeder. Many simulations show that the procedure achieves a good fault location performance though integration of time and frequency analysis on transient signals..

Keywords: Fault Location, Power Distribution, Travelling Wave, Wave Front Identification

Voltage and Frequency Stabilization of Electrical Networks by Using Load Shedding Strategy Based on Fuzzy Logic Controllers
by Moez Ben hessine, Houda Jouini, Souad Chebbi, Sahbi Marrouchi

Abstract - We present, in this paper, the analytical development of a new load shedding strategy based on fuzzy regulators. The aim of this strategy is to ensure the voltage and frequency stability of an electrical network. The strategy foundation is based on the sensitivity evaluation, in real time, of generated powers by alternators in relation to injected power levels at different network buses. Indeed, any variation of the power transit levels, taking place at the time of a disturbance appearance affecting the electrical network in a specified point, implicitly induced an operation imbalance of different alternators. We took into account, in our strategy, of possible network component dynamic behaviors resulting from the disturbance appearance via an optimized action established by fuzzy controllers.

Keywords: Load Schedding, Fuzzy Logic, PSRF, NSRF, Sensitivity, Positive Sequence, Negative Sequence, Eigen Value.

dSPACE Based Adaptive Control Schemes for the Emergency Power Flow Controller in Microgrids
by Tsao-Tsung Ma

Abstract - Distributed generation (DG) units with power electronics interfaced systems have been widely utilized in microgrids. These DG units can be considered as alternative real and reactive power sources besides satisfying the power demand of their local loads. In practice, DG units having higher power ratings are normally interfaced with utility grid via three-phase inverters equipped with dc storage units. Using proper controllers, both active and reactive power pumped into the utility grid from the DG units can be regulated as desired. In addition, with the reactive power control capability the DG units can also be used as reactive power compensation units for voltage regulation of microgrids. This paper presents a decoupled real and reactive power flow control scheme for an emergency power flow controller (EPFC) especially designed for some urgent microgrid operations. The proposed approach aims to achieve satisfactory adaptive and decoupled control features under grid-connected operating mode. The proposed control approach has been developed to control P or the voltage of the DC bus by adjusting the d-axis current of the inverter and to control Q by adjusting the component of q-axis current. To demonstrate the feasibility and verify the performance of the proposed control schemes, the related theoretical analysis and mathematical modeling are firstly described and followed by a set of comprehensive simulations and hardware studies on dSPACE1104. Both simulation and measured results have demonstrated a number of valuable merits, e.g. decoupled P and Q regulation capability, fast response in tracking P-Q commands and robust in a wide operating range.

Keywords: Distributed Generation, Microgrid, Decoupled Power Flow Controller, dSPACE1104.

Prior Distributions for Bayes Assessment of Photovoltaic Inverter Reliability and Availability
by L. Battistelli, E. Chiodo, D. Lauria

Abstract - The paper deals with the quantitative assessment of photovoltaic inverter system performance, focusing on the problem of its reliability and availability predictions. In particular, the problem of data uncertainty, due to a scarce knowledge of the components’ reliabilities, is taken into account. This problem is crucial for new technology systems and is faced within a Bayesian probabilistic framework: components’ reliability and availability parameters - hazard rate and repair rate - are considered as random variables, characterized in the paper by suitable Lognormal distributions, as motivated by well known and established physical and mathematical models relating, for instance, the hazard rate to the various factors (environmental, operational, manufacturing factors etc.) affecting the components’ reliabilities. Such methodology allows expressing the system availability uncertainty as a function of component uncertain data. For sake of brevity, due to complexity of the problem deriving from many sources of randomness, the paper develops only a methodology for establishing the prior (or “a priori”) distributions characterizing the basic (input) random variables (hazard rate and repair rate). On the basis of such distributions, the prior distribution of the components’ availability (output random variables of the problem) is deduced analytically. It is shown that a new distribution, denoted as “Beta-Lognormal”, is capable of efficiently representing the uncertainty of component availability, and its analytical properties are deduced. Numerical applications are presented to show the feasibility of the approach.

Keywords: Availability, Bayesian Inference, Beta and Lognormal Distributions, Photovoltaic Inverter, Reliability, Renewable Distributed Generation.

Optimal Location of FACTS Controllers for Minimizing Severity of Overloading and Voltage Control Under Contingencies
by G. Balamurali, K. Thanushkodi

Abstract - In this study, minimizing the severity of overloading (SOL) of the system and voltage control under contingencies is achieved by optimally locating the FACTS controllers in the power system. The Thyristor Controlled Series Compensator (TCSC) and Unified Power Flow Controllers (UPFC) are used in this work. A new index called Overload Value Index (OVI) is proposed and simultaneously used with Contingency Severity Index to identify the optimal location and then the optimal settings of TCSC and UPFC are arrived using the Constriction factor based particle swarm optimization (CF-PSO) algorithm. To show the validity of the proposed method, simulations are carried out on IEEE 6 Bus system and on practical 26 Bus Indian Grid System. The results show the effectiveness of the proposed method for selection of lines for TCSC and UPFC placement for minimizing the severity of overloading and voltage control under contingencies instead of only Contingency Severity Index based prioritising of lines for placement of FACTS controllers suggested by earlier researches. On comparing the results of placement of TCSC with UPFC, TCSC proved its superiority in minimizing the SOL of the system.

Keywords: Thyristor Controlled Series Compensator (TCSC), Unified Power Flow Controllers (UPFC), Severity of Overloading (SOL), Constriction Factor Based Particle Swarm Optimization.

Dynamic Optimization Model of AGC Strategy Under CPS for Interconnected Power System
by Wei Yan, Ruifeng Zhao, Xia Zhao, Yiming Li, Juan Yu, Zhenwen Li

Abstract - Automatic generation control (AGC) is an important domain in the unit scheduling and control of the power system. The pros and cons of its control strategy directly determine its effect. To address the problem of the inadequate effect of the traditional AGC strategy, a dynamic optimization model of an AGC strategy under CPS (DOMAGCSC) for interconnected power systems is proposed in this paper to improve the performance of AGC. The optimal CPS indicator and the minimum ancillary service cost are considered as objective functions. The influence of frequency change in the optimization cycle, the characteristic of minimum duration time of unit adjustment, and other power system constraints are considered in the DOMAGCSC, which is a multi-objective mixed-integer nonlinear programming problem. Then, a multi-objective immunity evolutionary programming (MIEP) algorithm is presented to solve the DOMAGCSC. Numerical tests on two different power systems are implemented to examine the proposed model by MIEP. The simulation results show that the proposed DOMAGCSC could optimize and improve the efficiency of AGC through a coordinative control of hydro and thermal units as well as of fast and slow units between multi-control cycles.

Keywords: Automatic Generation Control (AGC), Control Strategy, Frequency Control, CPS, Power Regulation, Multi-Objective Optimization, Evolutionary Programming.

DG Modeling Procedure Accounting for Power Output Correlation of Renewable Generators
by S. Conti, S. A. Rizzo

Abstract - The possibility to operate in islanding mode some portions of a distribution network potentially helps to improve system reliability when faults occur. In such a context, it is crucial to estimate the ability of local distribute generators (DGs) to meet the load, i.e. DGs’ adequacy. To this purpose, the present paper presents a new method to model power output correlation among local renewable generators of same technology, e.g. photovoltaic generators. Moreover, hourly model are considered in order to account for correlation among load power demand and renewable generators power output. An interesting aspect of the proposed generation modeling approach is that it encompasses such correlation avoiding the analytical calculating of its value.

Keywords: Islanding Operations, Micro-Grids, Power Output Correlation, Power System Reliability, Renewable Generators.

Quantitative Analysis of Power Loss Changes in Load, Generation, Storage and Distribution Sections of Different Microgrids Due to the DC Transition
by R. Asad, A. Kazemi

Abstract - Electrical systems mainly generate, transmit and distribute electrical energy through ac voltage for more than a century. But, some new modifications in electrical systems, such as the fast promising growth of renewable sources, dc loads and dc storage systems, make it necessary to study the possible roles of dc microgrids in current and future electrical systems, i.e. smart grids. In this paper, firstly, considering the recent modifications in the electrical industry, the new challenges of ac microgrids by dc microgrids are clarified. Then, one of the most important impacts of the transition to dc systems, i.e. power loss changes, has been separately studied and derived quantitatively and practically in four main sectors of microgrids, i.e. load, generation, storage and distribution systems, and the whole microgrids. The possible domain of the total power loss reduction for the four sectors and the whole microgrids has also been determined individually. Besides, the impacts of all parameters affecting the power loss changes, including the efficiency of different converters and storage units, are studied in detail. Moreover, to clarify the results of the dc transition more, the annual saved power, energy and cost of sixteen different microgrids are described. The quantitative results of this paper, in each sector and in the whole microgrid, are applicable for different numerous microgrids. The analyses done in this paper, is a significant step to determine which ac microgrids are to be converted to dc microgrids. Also, using the detailed results, the achieved profit due to the dc transition of various microgrids can be estimated.

Keywords: DC Microgrids, AC Microgrids, Power Loss, Load, Generation, Storage, Distribution, Smart Grids.

Pollution Emission Reduction with Minimum Transmission Loss in Power Dispatch Including Renewable Energy and Energy Storage
by F. R. Pazheri, M. F. Othman, N. H. Malik, E. A. Al-Ammar

Operating policies with minimum pollutants emission and transmission loss for an entire day is power dispatch operation are discussed in this paper. One of the main objectives of Economic/Environmental Dispatch (EED) and Environmental Friendly Dispatch (EFD) is to optimize the amount of pollutants emitted from the hybrid power plants. EED is an important multi-objective problem which minimizes both the fuel cost of generation and the amount of pollutants emission while EFD has the single objective of optimizing the amount of emission only. Here, EED and EFD are modified and renamed as EEDL and EFDL, respectively by including minimization of transmission loss as an additional objective. Optimization of these problems determines the amount of optimum generation which to be allocated to each generating unit including renewable sources without violating system constraints and minimizing the amount of pollutant emissions as well as transmission losses. Extraction and storing of renewable energy at off-peak times or at times when there would be a surplus of its availability and reuse of such stored energy during its unavailable periods makes such approach more effective. Optimum EEDL and EFDL can be obtained by extracting maximum renewable energy during their availability periods, then using it for both available and unavailable periods with the aid of energy storage. MATLAB simulations are performed using IEEE-30 test bus data with 6 generators to illustrate the benefits of renewable energy storage in reducing the unwanted pollutants emission.

Keywords: Economic/Environmental Dispatch, Energy Storage, Multi-Objective Optimization, Power Demand, Renewable Energy, Transmission Loss.

STATCOM Based on Cascade H-Bridge Converter for Compensating Reactive Power and Current Harmonics Simultaneously
by J. Pérez, V. Cárdenas, J. Alcalá, H. Miranda

Abstract - This paper presents how, through a suitable DC link regulation strategy, the cascade H-bridge converter can perform reactive power compensation and active filter functions simultaneously. The proposal consists in taking advantage of the fact that a current injected by STATCOM can be split up in three components that are linearly independent. The first component is devoted to compensate the converter losses in order to maintain the DC links regulated, the second component is in charge of compensating the reactive power and the third one is used to compensate current harmonics. As part of the control strategy it is shown how to generate individual control signal for each cell even if the multilevel converter is symmetrical or asymmetrical. A two cell binary prototype is used to evaluate the control scheme performance. Simulation and experimental results are presented.

Keywords: Active Filter, Asymmetrical Multilevel Converter, DC Link Regulation, STATCOM.

Space Vector PWM Control Technique Applied in Dynamic Voltage Restorer for Power Quality Improvement
by S. Deepa, S. Rajapandian

Abstract - The dynamic voltage restorer as a means of series compensation for mitigating the effect of voltage sags has become established as a preferred approach for improving power quality at sensitive load locations A technique based on the E-Z source inverter for the DVR is proposed in order to enhance the voltage restoration property of the device. By controlling the shoot through duty cycle, the Z source inverter system using MOSFET provide ride through capability during voltage sags, reduces line harmonics, and improves power factor and high reliability. The control for the DVR based on the dqo algorithm is discussed .There is an increasing trend of using space vector pulse width modulation (SVPWM) because of its easier digital realization and better DC bus utilization. A new control algorithm based on the SVPWM technique to generate the pulses is also presented. The proposed control algorithm is investigated through computer simulation by using MATLAB. A prototype of the proposed DVR was built and tested to confirm the feasibility of the hardware implementation, based on the simulation results.

Keywords: DVR, Voltage Sag, SVPWM, E-Z Source Inverter.

Multiconductor Transmission Line Models for PQ and EMC Analysis of Railway Electrification Systems
by A. Dolara, S. Leva

Abstract - This paper present and discuss two methods that allows to define MTL models that allows to represent the railway power electrification systems with a reduced number of conductors. Groups of conductors shorted together are replaced with an equivalent conductor and group of conductors grounded are included into the reference conductor. Reducing criteria are developed in the frequency domain and their extension to the time domain is discussed.
A section of the Italian 2x25 kV 50 Hz AC high speed railway power system is considered as a benchmark and reduction methods are applied to the MTL cells that represent this kind of electrification system, also including the high voltage grid that supply the Electrical Substation. The equivalent impedance at pantograph terminals and the disturbances on the track circuits caused by trains harmonic current injection are evaluated by using reduced models and taking into account several train positions along the railway line. The numerical results are reported, compared and discussed, considering both precision and computational times.

Keywords: Multiconductor Transmission Lines, Power System Harmonics, High Speed Railway Lines, Power Quality.

Posterior Distributions for Bayes Assessment of Photovoltaic Inverter Reliability and Availability
by L. Battistelli, E. Chiodo, D. Lauria

Abstract - TThe paper deals with the quantitative assessment or prediction of photovoltaic inverter system performance as measured by its reliability and availability, with the aim of developing an efficient and robust evaluation the above performance, in the presence of uncertainty due to a scarce knowledge of the basic parameters affecting such evaluation (e.g., the hazard rate and repair rate). The problem is dealt with by means of a Bayesian method of inference, in which the parameters to be estimated are considered as random variables. Once established – as shown in a previous paper – the prior probability distributions of the above parameters, in this paper their posterior distributions, both for Lognormal and Gamma prior models, are computed, in order to accomplish the Bayesian procedure of estimation. The paper also illustrates – by means of numerous numerical simulations - the efficiency of the estimates in the presence of field data, particularly in the case of scarce data. In the final section, an extensive numerical analysis is also performed, showing that the efficiency of estimation method and its robustness with respect to chosen prior distributions.

Keywords: Availability, Bayesian Inference, Beta and Lognormal Distributions, Photovoltaic Inverter, Reliability, Renewable Distributed Generation.

HVDC Link and HVAC Transmission Line Comparison in Transmission Expansion Considering Social Welfare Maximization
by M. Rahmatian, A. Rahiminejad, S. H. Hosseinian, G. B. Gharehpetian, M. J. Sanjari

Abstract - In this paper, transmission expansion planning problem with High Voltage Direct Current (HVDC) links and AC transmission tie lines are compared based on social welfare maximization in a Deregulated Power System (DPS). The social welfare is optimized using Differential Evaluation Algorithm (DEA) for four different scenarios. First, the loads, generations and power flow of transmission lines are determined for each scenario. In the next step, the most congested line of the system is selected for transmission expansion. To overcome the problem, two options are considered, i.e., an HVDC link and an AC tie line. These options are compared considering social welfare optimization in a ten-year planning horizon. IEEE 30-bus system is selected for this study. The obtained results show more increase in social welfare using HVDC transmission links.

Keywords: High Voltage Direct Current (HVDC), Social Welfare, Deregulated Power Systems (DPS), Differential Evaluation Algorithm (DEA).

Distributed Generation Electricity Price Forecasting in a Deregulated Electricity Market
by S. Porkar, P. Poure, S. Saadate

Abstract - This paper presents a new methodology for optimal placement, size and electricity price of different types of Distributed Generation (DG) considering electricity market price fluctuation. DG is introduced to participate in electricity market comparing with voltage regulator devices and interruptible load, to solve the lacking electric power supply problem with a reasonable price. The problem of optimal placement and size is formulated in two stages; minimization the total cost to find optimal sizing and siting of the different types of DG vs. different investment payback time, and maximization the Global System Benefit (GSB) function to find optimum DG electricity price. In this methodology, cost function is investment costs, which evaluated as Equivalent Annual Cost (EAC), plus to total running cost and GSB function is defined as the difference between global system costs before and after DG installation. Different system conditions are assumed to indicate the effect of the system conditions on planning decision. In this paper, five types of DG are studied. The proposed two-stage model aims to find optimal DG placement and DG electricity price, especially in a deregulated electricity market environment. The proposed methodology is tested in IEEE 30-bus test system by using a developed user-friendly software package.

Keywords: Distributed Generation (DG), Distribution System Planning, Electricity Market, Global System Benefit (GSB), Mathematical Optimization.

Solution to Non-Convex Economic Power Dispatch Problems with Generator Constraints by Charged System Search Algorithm
by S. Özyön, B. Durmuş, C. Yaşar, H. Temurtaş, G. Kuvat

Abstract - Today along with an increase in the need for electrical energy, economic power dispatch problem has become one of the most important issues in the operation of power systems. In this study, the solution of the economic power dispatch problems with valve point effects and prohibited operating zones which consider ramp rate limits of the generators as well as the present power limits have been found by the charged system search (CSS) algorithm. In the solution of the problems, the transmission line losses have been calculated by using B loss matrices. The CSS method has been applied to the 15 generator test system in literature for economic power dispatch problem with prohibited operating zones and power generation limit and it has been applied to 30 bus 6 generator (IEEE) test system in literature for non-convex economic power dispatch problem with valve point effect under different constraints. The best solution values found for both of the test systems have been compared with the solution values found by the application of different methods in literature and the results have been discussed.

Keywords: Non-Convex Economic Power Dispatch, Prohibited Operating Zones, Ramp-Rate Limits, Valve-Point Effects, Charged System Search Algorithm.

Cost Optimization of Power Generation Using A Differential Evolution Algorithm Enhanced with Neighbourhood Search Operation
by J. Jasper, R. S. Sivakumar, T. Aruldoss Albert Victoire, S. N. Deepa

Abstract - This study discusses a novel and efficient algorithm for solving economic load dispatch (ELD) problem formulated with non-smooth fuel cost function. A more realistic ELD problem is formulated by considering non-linear generator characteristics such as valve point effect, ramp rate limits, prohibited operating zones and spinning reserve. To solve this complex ELD problem, a new method based on differential evolution (DE) is considered. In this method, a neighbourhood search operation (NSO) for each population member is performed and thereby accelerating it to find the best solution. This also explores the search space for new optimum regions by replacing weak solutions with randomly selected individuals. The idea of this technique is to balance the exploitation and exploration capability of DE. The NSO-DE method incorporates DE as the main optimizer and NSO as a local optimizer. The performance of the NSO-DE method is validated using various standard test systems consisting of 10, 13 and 15 thermal units. The robustness and effectiveness of the NSO-DE is compared with other strategies of DE based on the quality of the final solution obtained.

Keywords: Differential Evolution, Economic Load Dispatch, Neighbourhood Search Operation, Prohibited Operating Zones, Spinning Reserve, Valve Point Effect.

Solid-State Circuit Breaker Operation with Enhanced Commutation Circuit
by I. Alagarasan, B. Karthik, S. Chandrasekar

Abstract - TSolid-State Circuit Breaker (SCB) is a high power semiconductor device which is used to improve the voltage quality as well as it will also reduce the short circuit current and voltage distortion during a short circuit failure. In the time of short circuit, the voltage distortion occurs and it increases the short circuit current. The short circuit current is reduced by using a commutation circuit. The commutation circuit is interconnected by power electronic devices such as main, auxiliary thyristors and commutation capacitor. During short circuit, the increased fault current reaches the commutation capacitor. Then the commutation capacitor is discharged and it will make an open circuit to reduce the short circuit current. But, the discharging time of the commutation capacitor is very high and so it takes more time to reduce the short circuit current. Due to this reason, the performance of SCB is affected. Therefore, to improve the performance of SCB, a modified commutation circuit based SCB is proposed in this paper. Our proposed commutation circuit will consist of a digital switch and current comparator. The digital switch will be added in the place of commutation capacitor. Then the fault current will be calculated by using the current comparator. When the time of fault occurs, the fault current will be reduced by opening the digital switch. If the digital switch is opened, then an open circuit is formed in the commutation circuit and it will take less time to make the open circuit when compared with the performance of capacitor-enabled SCB. This will lead to improved performance of SCB in handling short circuit failure. The performance of the proposed commutation circuit will be evaluated.

Keywords: PQ, SCB, Voltage Distortion, Commutation Circuit, Digital Switch, Current Comparator.

State of Charge Estimation for LiFePO4 Battery Using Artificial Neural Network
by Wen-Yeau Chang

Abstract - An artificial neural network based state of charge (SOC) estimation method for LiFePO4 battery is proposed. The artificial neural network is one of the best tools applied to state estimate. In this paper two types of typical neural networks, namely, back propagation (BP) neural network and radial basis function (RBF) neural network are investigated. The proposed SOC estimation method uses the input data of the terminal voltage, discharging current, and temperature of battery to estimate the SOC for LiFePO₄ battery under different discharging conditions. To demonstrate the effectiveness of the proposed estimation method, the method has been tested on 3.2V, 10AH LiFePO₄ batteries under several different discharging conditions. The experimental data are found to be in close agreement. The test results show that the proposed method is efficient and reliable.

Keywords: State of Charge, LiFePO4 Battery, Back Propagation Neural Network, Radial Basis Function Neural Network.

Directional Calibration of Rogowski Coil for Localization of Partial Discharges in Smart Distribution Networks
by M. Shafiq, L. Kütt, M. Isa, M. Hashmi, M. Lehtonen

Abstract - Partial discharge (PD) diagnostics is an important criterion for evaluation of the insulation condition of high voltage electrical equipments. In this paper, Rogowski coil is used as a PD sensor to propose a technique for localization of PD defects based on direction of arrival of PD current pulses approaching towards Rogowski coil. Directional calibration of Rogowski coil is made by analyzing its theoretical and practical response to a PD pulse. An experimental model is presented to implement the proposed technique for straight and branched type power cable network. The proposed technique can be used to increase the accuracy of PD faults localization in an integrated PD monitoring system for a smart electricity distribution network.

Keywords: Partial Discharges, Rogowski Coil, Calibration, Direction of Arrival, Fault Localization, Smart Distribution Network.

The Effect of Moisture and Temperature on Partial Discharge Behavior in New and Aged Oil/Pressboard Insulation System
by Milad Karimi, AmirAbbas Shayegani Akmal, Benyamin Alamati, Hossein Mohseni

Abstract - This paper presents an investigation of partial discharge (PD) behavior in oil-impregnated new and aged, wet and dried pressboard insulation system at both ambient (around 20°C) and the hottest temperature of transformer normal operation (around 90°C). The main idea of this investigation is to study the impact of specific conditions such as those occur in practical cases in oil type transformers, on the variation of moisture and temperature. Temperature is a major cause of deterioration and aging of cellulose insulation. On the other hand, moisture equilibrium in oil/pressboard insulation is dependent on temperature and the estate of power transformer.
The dynamic of moisture transfer from oil into pressboard and vice versa according to the variation of temperature affects partial discharge inception voltage (PDIV) and phase resolved PD (PRPD) patterns.
Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved

Keywords: Partial Discharge (PD), Partial Discharge Inception Voltage (PDIV), Temperature, Moisture, Aging, Pressboard, Oil.

A Genetic Evolutionary Task Scheduling Method for Energy Efficiency in Smart Homes
by Hui Miao, Xiaodi Huang, Guo Chen

Abstract - For electricity consumers, there are power loads which need to be processed in a predefined time interval. The electricity price could vary between peak and off-peak time. In that case, the intelligent task scheduling module in a smart home can minimize the entire energy expense if the task control module could schedule the electrical equipments’ start times, which are determined by their power consumptions and operation time constraints. In Smart Grid environments, this Advanced Metering Infrastructure (AMI) could automatically schedule the operation time of each equipment to minimize the residential overall power consumption while satisfying the equipment’s operation constraint such as the equipment needs to be started at a time between two predefined time instants, and the power system is not overloaded at any time instant. In this research, the paper formulates the situation as an optimization problem and proposes a Genetic Algorithm (GA) based algorithm to find the optimum schedule arrangement for all the tasks in a smart home to reduce the energy cost. The performance of the GA based method is evaluated with the previous research works such as SA based method and greedy search method. The simulation results show that the GA based scheduling algorithm can efficiently and optimally minimize customers’ electricity cost.

Keywords: Smart Home, Genetic Algorithm, Task Scheduling, Smart Grid.

Binary Particle Swarm Optimization Selected Time-Frequency Features for Partial Discharge Signal Classification
by Ruijin Liao, Ke Wang, Lijun Yang, Jian Li, Shijun Nie, Lei Yuan

Abstract - In this study, the development of binary particle swarm optimization (BPSO) feature selection algorithm is proposed for partial discharge (PD) signal classification based on quantified time-frequency features. Firstly, adaptive optimal kernel (AOK) time-frequency representation technique is employed to obtain a high quality of time-frequency distribution of partial discharge ultra-high-frequency (UHF) signals with reasonable resolutions in both time and frequency domains. Then, a non-negative matrix factorization (NMF)-based matrix decomposition (MD) method is applied to obtain a series of base vectors in frequency domain and location vectors in time domain which are further used to extract statistical features to construct an adequate feature space representing the time-frequency information. Finally, the developed BPSO feature selection algorithm is adopted to improve PD classification performance. A fuzzy k-nearest neighbor (FkNN) classifier is responsible for the classification task and used as the fitness evaluator of BPSO. Using a UHF detector, 600 PD signals sampled from four categories of artificial defect models in the laboratory are adopted for testing. Performances of various feature sets, including all the statistical features, artificially combined features with different dimensions and BPSO selected features, are compared. Results demonstrate that the proposed feature extraction and selection algorithm can provide an effective tool for partial discharge signal classification, and it is easy to extend to other image or matrix applications.

Keywords: Partial Discharge, Pattern Recognition, Adaptive Optimal Kernel, Non-Negative Matrix Factorization, Statistical Parameters, Binary Particle Swarm Optimization, Fuzzy K-Nearest Neighbor.

Study on Optimized Information Transmission Scheduling Strategy Oriented to Advanced Metering Infrastructure
by Xianji Jin, Weiming Tong, Lei Lu

Abstract - Advanced metering infrastructure (AMI) is considered to be the first step in constructing smart grid. AMI allows customers to make real-time choices about power utilization and enables power utilities to increase the effectiveness of the regional power grids by managing demand load during peak times and reducing unneeded power generation. These initiatives rely heavily on the prompt information transmission inside AMI. Aiming at the information transmission problem, this paper researches the communication scheduling strategy in AMI at a macroscopic view. First, the information flow of AMI is analyzed, and the power users are classified into several grades by their importance. Then, the defect of conventional information transmission scheduling strategy is analyzed. On this basis, two optimized scheduling strategies are proposed. In the wide area, an optimized scheduling strategy based on user importance and time critical is proposed to guarantee the important power users’ information transmission being handled promptly. In the local area, an optimized scheduling strategy based on device and information importance and time critical is proposed to guarantee the important devices and information in AMI user end system being handled promptly. At last, the two optimized scheduling strategies are simulated. The simulation results show that they can effectively improve the real-time performance and reliability of AMI information transmission.

Keywords: Smart Grid, Advanced Metering Infrastructure (AMI), Information Transmission, Scheduling Strategy.

Application of a Photovoltaic Generation System in a Small-Scale Air Conditioner
by K. H. Chao, C. H. Huang, Y. C. Chang

Abstract - The goal of the present study is to develop a photovoltaic generation system for small-scale air conditioners. The structure of the photovoltaic generation system comprises an intelligent maximum power point tracking controller, a bidirectional DC-DC converter, and a small-scale air conditioner, wherein the intelligent maximum power point tracking controller adopts the extension perturb and observe method, such that the controller excels at dynamic response and achieves a stable performance. Since the maximum power point tracking process results in variation in the voltage of the DC-link, the present study proposes a DC-link voltage regulation strategy. This system makes use of the bidirectional DC-DC converter and the charge/discharge control of the battery to achieve DC-link voltage regulation, and uses the regulated stable voltage of the DC-link to supply power for the small-scale air conditioner. Finally, the practicality of application of the photovoltaic generation system in small-scale air conditioners is verified with evidence based on simulation and empirical testing.

Keywords: Photovoltaic (PV) Generation System, Maximum Power Point Tracking (MPPT), DC-link Voltage Regulation, Bidirectional DC-DC Converter.

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International Review of Electrical Engineering - October 2012 (Vol. 7 N. 5) - Papers Part A

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