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International Review of Electrical Engineering Vol. 6 N. 2-- Part A

International Review of Electrical Engineering Vol. 6 N. 2-- Part B

International Review of Electrical Engineering - April 2011 (Vol. 6 N. 2) - Papers Part A

	Time Domain Analysis of Fourth Order LCLC Resonant Converter Interleaved Double Boost Converter with High Power Factor Two Types of Dual-Output Converters The Effect of Power Transformer Winding Structure on the Reliability of Switching Power Supplies An Isolated Bi-Directional DC-DC Converter with Zero Current Switching in LV Side and Zero Voltage Switching in HV Side Series Resonant Converter with Output Voltage Doubler for Server Power Supply Unit DSP Microprocessor Based-on Power Factor Correction to Improve Power Quality of Converters Using Predictive Control Control of Asymmetric Cascaded Multilevel Inverters Based on Charge Balance Control Methods Analysis and Implementation of Step-Up ZVS SEPIC Converter Analysis and Performance of a High-Efficiency Transformerless Hybrid Active Filter APWM Soft-Switching Integrated Boost Full-Bridge Converter ith High Voltage Gain Analysis of a ZVS Parallel-Connected Forward Converter Performance Analysis of Three Phase Multilevel Inverters Using Sinusoidal Pulse Width Modulation with Zero Sequence Signal Analysis of a Single-Phase Integrated LLC Resonant Converter High Precision and Auto Tune Class D Amplifier or Piezoelectric Transducers A Single-Stage PV Module Integrated Converter (MIC) with High Voltage Gain Capability Electromagnetic Interference Filter Design Based on Noise Impedance Measurements for Switching Power Converters Optimization of Inductor Based on Genetic Algorithm for the Medium Voltage Cascade Converter with Active Front End A Hysteresis Current Control Strategy for Common-Mode Voltage Reduction in AC Drive Systems A Novel Modified Space Vector Pulse Width Modulation Technique for High Performance Z-Source Inverter A Zero-Voltage-Switching Resonant Flyback Converter with Single Magnetic Component The Effect of Winding Structure on the Current Distribution of Paralleled Wires in High Frequency Transformers Recurrent Neural Network Based Nonlinear State Estimation for Induction Motors Analysis of the Transient Operation of a Salient Pole Synchronous Machine During Stator and Field Internal Short Circuit Using F.E.M. Induction Motor Real Time Application of Multimodel Modeling Approach Design of Magnetostriction Phenomena in Electric Motors by Using Time Discretization Simulation and Experimental Set of Vector Controlled Induction Machine Using Power Line Communication for Speed Measurement New External Rotor Switched Reluctance Motor in Comparison with Conventional SRM Hammerstein Based Modeling of Traveling Wave Ultrasonic Motors Improving Sensorless Control of BLDC Motors by Offering a New Parameters Estimation Algorithm for BLDC Motors PI-Elman Neural Network Based Nonlinear State Estimation for Induction Motors Stray Capacitance and Sensitivity Coefficients Ratio in One Turn of MFCG Coil Vector Control of Four-Phase Induction Machines with Two Current Sensors A Comparative Approach within Chemical Battery, Flywheel and Supercapacitor Base Energy Storage System for LEO Satellite Applications Design and Analysis of Outer Rotor in-Wheel Motor Performance Analysis of a Disc Type BLDC Motor for Electric Vehicles Axial-Flux Permanent-Magnet Brushless DC Traction Motor for Direct Drive of Electric Vehicle Optimum Design of Switched Reluctance Machine for Electric Vehicle Applications Using Chaotic Particle Swarm Optimization Control of a Flexible Platform for Photovoltaic Grid-Connected Systems Using a DSP-Microcontroller Arrangement
International Review of Electrical Engineering - April 2011 (Vol. 6 N. 2) - Papers Part B
	Optimal Placement of FACTS Devices in Large Power System Using PSO Method Voltage Stabilization of Electrical Network by Using UPFC Compensator Commanded by Fuzzy Controllers Minimization of Power Transmission Losses in Series Compensated Systems Using Genetic Algorithm Simultaneous Power Flow Control and Voltage Support Using UPFC A Novel Genetic Algorithm for the Coordinated Optimal Reactive Power Dispatch in Power Systems with Wind Farms and FACTS Available Transfer Capability Determination by Incorporating Reactive Power Flow in Deregulated Power Systems Design and Development of ANFIS Controller for STATCOM in dSPACE Environment A Novel Approach to Optimal Power Flow Problems in Power Systems Embedded with Various DG and FACTS Devices A Novel Hybrid GA-PSO Technique for Optimal Tuning of Fuzzy Controller to Improve Multi-Machine Power System Stability Evaluation of Fault Location based on Voltage Sags Profiles: a Study on the Influence of Voltage Sags Patterns A Benders Decomposition Approach for Optimal Wind Capacity Allocation to Power System with Security Constraints Damping Controller Design for Power System Oscillations Using Hybrid GA-SQP Effect of Static Synchronous Series Compensator on Damping Oscillation in Power System Enhancement Optimal Design of PID Power System Stabilizer in Multi-Machine Power System Using PSO and Genetic Algorithm Voltage Stability Analysis Using the Variable Gradient Method Application of Bacterial Foraging Algorithm for Enhancement of Voltage Stability Using L-Index Approach On-Line Voltage Stability Preventive Control Considering Double Contingency Design and Analysis of a Novel Dual-input PSS for Damping of Power System Oscillations Employing RCGA-Optimization Technique PQ Monitor-based Automated Fault Location Using Database Technique for 11kV Distribution System Congestion Cost Allocation Base on Contribution for Pool Market A New Economic Benefit and Use of System Method for Transmission Expansion Cost Allocation in the Competitive Market Environment Economic Evaluation of Uncertain Distributed Generations for a Distribution Company Electricity Tariff Design Based on Clustered Load Profiles Classified by Exploiting Questionnaires Optimized Bidding Strategy of Generation Companies in the Energy and Reserve Markets by Game Theory A Mixed Active-Passive Algorithm for Islanding Detection of Wind Turbine DG Units Reliability Assessment of Distribution System Considering Customer-Owned Distributed Generation Optimal Placement of Distributed Generators and Reconfiguration of Distribution Systems for Loss Reduction using Genetic Algorithm Evaluation of the Electromagnetic Fields due to Lightning Channel with Respect to the Striking Angle Calculation of Low Frequency Electric Fields of Complex Power System Facilities New Approach for Corona Loss Calculation Considering Ion Diffusion Variation Using FEM ANFIS Based Contamination Level Prediction of Porcelain Insulator Under Various Pollution Conditions Finite Element Simulations of the Field Distribution for Artificially Aged Polymeric Insulators Comparison of Bayesian and Fuzzy ARTmap Networks in Transformers PD Localization

International Review of Electrical Engineering - Papers- Part A

Time Domain Analysis of Fourth Order LCLC Resonant Converter
by Jafaboland Mehrdad

Vol. 6. n. 2, pp. 459-466

Abstract - An analytical methodology for the rapid steady-state analysis of fourth-order resonant power converters, with capacitive output filter, is proposed. Analysis of the converter shows that there are four intervals in half period. In each interval, the state-space equations is obtained and due to the soft switching of the converter, an exact equation for Zero Voltage Switching (ZVS) time and maximum dead time of the inverter switches is presented. To demonstrate the feasibility of this solution, prototype is assembled and tested with good performance and similar behavior to the one predicted by the models. The simulation and experimental results obtained from a 10kv, 370w prototype confirm the validity of theorical analysis.

Keywords: Fourth Order LCLC Resonant Converter, State –Space Approach, ZVS Time.

Interleaved Double Boost Converter with High Power Factor
by Bor-Ren Lin, Chih-Cheng Chien

Vol. 6. n. 2, pp. 467-474

Abstract - An interleaved double-boost converter is presented in this paper to achieve power factor correction (PFC), regulate DC bus voltage and reduce ripple current and input and output sides. The adopted double-boost converter has a high voltage conversion ratio to overcome the limit of a conventional boost converter with narrow turn-off period. The interleaved pulse-width modulation (PWM) can further reduce the input and output ripple currents such that the sizes of inductor and capacitor are reduced. Since boundary conduction mode (BCM) is adopted to control the inductor current, the AC source current can be easy to follow the utility voltage with nearly unity power factor and power switches are turned on at zero current switching (ZCS). The circuit configuration, principle operation, system analysis, and design consideration of the proposed converter are presented. Finally, experiments conducted on a laboratory prototype rated at 500W were presented to demonstrate the performance of the proposed converter.

Keywords: Double Boost, High Voltage Step-Up, Power Factor Correction.

Two Types of Dual-Output Converters
by K. I. Hwu, Y. T. Yau, Jenn-Jong Shieh

Vol. 6. n. 2, pp. 475-484

Abstract - In this paper, novel dual-output boost and buck-boost converters with positive and negative output voltages under a given single positive voltage source fed. Due to its dual output with positive and negative output voltages, these converters are very suitable for driving the half-bridge class-D amplifier, so as to remove a DC blocking capacitor required in the half-bridge class-D amplifier. In this paper, firstly the basic operating principles of this converter are illustrated along with a simple mathematical deduction, and eventually some experimental results are provided to demonstrate its effectiveness.

Keywords: Dual-Output Boost Converter, Dual-Output Buck-Boost Converter.

The Effect of Power Transformer Winding Structure on the Reliability of Switching Power Supplies
by B. Abdi, L. Yazdanparast, R. Alaei, H. Gholamrezaei

Vol. 6. n. 2, pp. 485-491

Abstract - Recently, reliability is one of the serious requirements of electronic systems. The numbers of system failures, repair cost, guarantee, etc are estimated by reliability calculations. In this paper, the reliability of a switching power supply is evaluated and the effect of the type of transformer winding on the reliability is fully discoursed. Experimental results beside calculations prove that the interleaved winding will increase the reliability of SMPS’s considerably.

Keywords: HF Transformer, Leakage Inductance, Reliability, Life Time, SMPS.

An Isolated Bi-Directional DC-DC Converter with Zero Current Switching in LV Side and Zero Voltage Switching in HV Side
by H. Riazmontazer, J. S. Moghani, M. Taheri, H. Bayat

Vol. 6. n. 2, pp. 492-500

Abstract - In this paper, a novel current-voltage fed ZCS-ZVS bidirectional dc-dc converter is proposed, which refers to current fed inverter that implements ZCS in low voltage side of transformer, and refers to Voltage fed inverter that implements ZVS in high voltage side. Using two input inductors, input current is divided equally between two legs of converter in LV side and by help of ZCS technique, transformer primary side current is limited between inductors currents that leads to minimizing the circulating loss of transformer and switches current stress. ZVS range is also increased by use of leakage inductance plus input inductances in ZVS process and without any additional control strategy. The operation principle is analyzed and verified by simulation and experimental results. A laboratory prototype is built to demonstrate the feasibility of the system.

Keywords: Bidirectional Dc-Dc Converter, Zero Voltage Switching (ZVS), Zero Current Switching (ZCS).

Series Resonant Converter with Output Voltage Doubler for Server Power Supply Unit
by Bor-Ren Lin, Yen-Ju Chiang

Vol. 6. n. 2, pp. 501-511

Abstract - The series resonant converters have been widely used for high efficiency low power applications such as LCD monitor and all-in-one computer power unit. Compared with other resonant power converters such as LC series resonant converters and LC parallel resonant converters, LLC resonant converters have the advantages of higher voltage gain, zero voltage switching (ZVS) turn-on for power switch at wide load range, zero current switching (ZCS) turn-off for rectifier diodes, and output voltage regulation at no-load condition. To reduce the current stresses on output diodes, the parallel LLC series resonant converter is presented in this paper. Thus the output diodes with low current stresses can be adopted in the circuit. The root mean square currents on transformer secondary windings, transformer copper losses, and thermal losses can be further reduced. The output voltage doubler topology is used in the output side to implement the high output voltage application. Thus the secondary winding turns are reduced. The principle of operation, steady state analysis and design example of the proposed converter are provided and discussed in detail. The proposed converter is suitable for high efficiency applications such as LCD-TV, PDP-TV and server power supply unit. The laboratory experiments with a 960W prototype are provided to verify the effectiveness of the proposed converter.

Keywords: Power Supply, Series Resonant Converter, Zero Voltage Switching.

DSP Microprocessor Based-on Power Factor Correction to Improve Power Quality of Converters Using Predictive Control
by Ahmet Karaarslan, Ires Iskender

Vol. 6. n. 2, pp. 512-521

Abstract - In this study, the predictive control approach is adapted to the current control strategy for the Bridgeless Power Factor Correction (PFC) converter. The control approach is developed to eliminate the input line current harmonics of the PFC converter without needing for the current sampling. In this approach, the zero crossing points of the input voltage are detected using DSP microprocessor. A sinusoidal signal is generated based on the detected points and used as a reference to control the converter switch to obtain unity power factor and lower input current Total Harmonic Distortion (THD). An adaptive digital FIR filter is designed and embedded into the control loop cancel the effects of noises and distortions on the output voltage. The feed forward technique is also used in the control algorithm by taking into account the maximum value of the input voltage. The implementation of feed forward and adaptive digital filter into the control algorithm improves the converter performance. The average current control (ACC) loop is used in the converter operating in continuous conduction mode (CCM). The converter used in simulation and experimental studies is a bridgeless power factor converter. The conduction losses of the switches of this converter are lower comparing to the similar PFC converters. The simulation and experimental results show that the proposed control strategy works well and the unity power factor operation can be achieved with a wide input voltage and load variation ranges. The results are compatible with IEC 61000-3-2 Current Harmonic Standard.

Keywords: AC/DC Converters, Adaptive Digital FIR Filter, Bridgeless Converter, Power Factor Correction, Power Quality, Predictive Control.

Control of Asymmetric Cascaded Multilevel Inverters Based on Charge Balance Control Methods
by Sara Laali, Karim Abbaszadeh, Hamid Lesani

Vol. 6. n. 2, pp. 522-528

Abstract - In this paper, a new algorithm is proposed to determine the magnitudes of dc voltage sources in asymmetric cascaded multilevel inverters. Using this algorithm, it is possible to generate the maximum number of output voltage levels and maximum output voltage amplitude with minimum number of dc voltage sources. Using this algorithm, it is possible to use charge balance control methods to all dc sources except the minimum amplitude dc voltage source (first H-bridge). Therefore, the lifetime of dc voltage sources used in different H-bridges of cascaded asymmetric multilevel inverter except the first H-bridge are the same. As a result, the system’s maintenance cost will be low. The simulation and experimental results confirm the abilities of the proposed method.

Keywords: Multilevel Inverter, Symmetric Cascaded Multilevel Inverter, Asymmetric Cascaded Multilevel Inverter, Charge Balance Control Methods.

Analysis and Implementation of Step-Up ZVS SEPIC Converter
by Bor-Ren Lin, Huei-Yuan Shih

Vol. 6. n. 2, pp. 529-536

Abstract - In this paper, a step-up active-clamp SEPIC converter with bi-transformer is presented for battery sourcing application. Two transformers are used in the conventional SEPIC converter and connected in series at secondary side to achieve high voltage conversion ratio. Active-clamp circuit including one auxiliary switch and one clamp capacitor is connected in parallel with the main switch to allow the resonant behavior by the output capacitances of switches and transformer leakage inductance during the transition interval. Thus the ZVS turn-on of switches can be achieved. The switching losses and thermal stresses of the semiconductors are reduced. The interleaved operation in output side reduces the ripple current and the output capacitance. Based on the circuit configuration, the voltage stresses of secondary diodes are clamped to Vo such that no snubber circuit is needed on the rectifier diodes. The circuit configuration, operation principle and design consideration of the converter are discussed in detail. Finally, experiments, based on a laboratory prototype with 48V input and 200V/2A output, are provided to verify the theoretical analysis and the effectiveness of the proposed converter.

Keywords: ZVS, Sepic, Active Clamp, Step-Up.

Analysis and Performance of a High-Efficiency Transformerless Hybrid Active Filter
by Perttu Parkatti, Heikki Tuusa, Hannu Sarén, Kosti Kuusela, Michael Björkman

Vol. 6. n. 2, pp. 537-546

Abstract - Active harmonic filters have been widely studied in recent years. Price, size and power losses have been the main problems with conventional active filters. This paper proposes a 3-phase voltage source active filter with series-connected capacitors and an LCL-type line filter (LCLC-VSAF). The system makes it possible to compensate harmonics with a lower dc-link voltage, higher switching frequency, and smaller filter inductors. Moreover, the active filter can be built using a fairly inexpensive standard frequency converter with a lower power rating. Experimental test results will be presented. Harmonics caused by 20 kW nonlinear loads were compensated in the 690 V power system. An active filter built on a commercial 400 V frequency converter with 20 kHz switching frequency was used. Efficiency up to 99 % was achieved.

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

APWM Soft-Switching Integrated Boost Full-Bridge Converter ith High Voltage Gain
by Hyun-Lark Do

Vol. 6. n. 2, pp. 547-554

Abstract - An asymmetrical pulse width modulation (APWM) soft-switching integrated boost full-bridge converter with high voltage gain is presented. In the presented converter, the boost-fed structure is utilized to provide a continuous input current. APWM full-bridge DC-DC converter with 2-stage voltage doubler in the proposed converter provides soft-switching characteristic of main switches and high voltage gain. Moreover, the leakage inductance of the transformer alleviates the reverse-recovery problems of the output diodes. The proposed converter achieves high efficiency because of mitigation of the output diodes’ reverse recovery problem and soft-switching characteristic of main switches. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.

Keywords: Full-Bridge Converter, Soft-Switching, Voltage Doubler, High Voltage Gain.

Analysis of a ZVS Parallel-Connected Forward Converter
by Bor-Ren Lin, Kun-Liang Shih

Vol. 6. n. 2, pp. 555-565

Abstract - This paper presents a soft switching converter with interleaved pulse-width modulation (PWM) scheme. There are two circuit modules in the proposed converter to share the load current. The interleaved PWM scheme is adopted to control two converter modules such that the input and output ripple currents and the current stresses on power switches and transformer windings are reduced. In each converter module, two forward converters with active clamp technique are adopted to further reduce the ripple current on the output capacitor and decrease the current stresses on transformer windings. The gate signals of two power switches in each converter module are complementary each other in order to realize the zero voltage switching turn-on of switches at the transition interval. Thus, the switching losses and thermal stresses of the semiconductors and transformers are reduced. All of these features make the proposed converter suitable for the dc-dc converters with high output current. Finally, experiments based on a 600W prototype are provided to verify the theoretical analysis.

Keywords: Power conversion, Power Converter, ZVS.

Performance Analysis of Three Phase Multilevel Inverters Using Sinusoidal Pulse Width Modulation with Zero Sequence Signal
by P. Palanivel, S. S. Dash, N. Chellammal, A. F. Zobaa

Vol. 6. n. 2, pp. 566-573

Abstract - In this paper, various pulse width modulation techniques are proposed, which can minimize total harmonic distortion and enhance the output voltages in five-level inverters. Multilevel inverters are important for power electronics applications, such as flexible AC transmission systems, renewable energy sources, uninterruptible power supplies and active power filters. Three methodologies adopting constant switching frequency, variable switching frequency and phase shifted carrier pulse width modulation concepts are proposed in this paper. These methodologies are divided into two techniques: sinusoidal pulse width modulation which minimizes total harmonic distortion and sinusoidal pulse width modulation with zero sequence signal which enhances the output voltage. FPGA has been chosen to implement the pulse width modulation due its fast prototyping, simple hardware and software design. The simulation and experimental results are presented.

Keywords: Multilevel Inverters, Pulse Width Modulation, Harmonics, Switching Frequency, Phase Shifting.

Analysis of a Single-Phase Integrated LLC Resonant Converter
by Ching-Ming Lai, Ming-Ji Yang

Vol. 6. n. 2, pp. 574-579

Abstract - In this paper, a single-stage boost-integrated LLC series resonant converter (S2BILLC-SRC) is proposed. The proposed S2BILLC-SRC produces new topology that combines the input current shaping capabilities of the boost power-factor correction (boost-PFC) and the soft switching operation of the LLC series resonant converter (LLC-SRC). An 110V line input, and 28V/5A output, laboratory prototype is presented to verify the feasibility. Experiments show that the proposed S2BILLC-SRC successfully meets IEC 1000-3-2 Class D regulations, nearly a unity power factor, and that the conversion efficiency can be achieved up to 91.6% under a rated condition. Also, the proposed S2BILLC-SRC, compared with a conventional single-stage boost-integrated LC series resonant converter (S2BILC-SRC) and a conventional single-stage boost-integrated LC parallel resonant converter (S2BILC-PRC), can improve the overall conversion efficiency about 2.4% and 3.1%, respectively.

Keywords: Single-Phase, Integrated LLC Resonant Converter.

High Precision and Auto Tune Class D Amplifier or Piezoelectric Transducers
by Vahid Rashtchi, Amir Safaei, Amir Abdullad

Vol. 6. n. 2, pp. 580-586

Abstract - In the applications of piezoelectric transducers, the existence of power supply is unavoidable. In the operation point of the piezoelectric transducers due to generated heat, loading effect and other environment conditions, the resonance frequency of the whole system may vary and caused to reduction of efficiency. In this paper a novel Class D amplifier with ability of self tuning is presented. The proposed amplifier has the ability of resonance frequency finding of the system in many operating conditions in a real time process. The efficiency of this class D amplifier is greater than 95%. Output frequency of the amplifier is in the range of 17 kHz to 40 kHz with resolution of 1 Hz. Also the power delivered to load can be controlled by varying of pulse width modulation (PWM) duty cycle with precision of 1%. Implementation of such amplifier with current analog power supplies may be caused to instability or reduction of efficiency. So the proposed amplifier has a fully digital control unit and its output frequency and amplitude are independent of environment conditions. Experimental results show that this low cost amplifier is able to tune and maintain the piezoelectric transducers in their resonance frequency and deliver the maximum power to load.

Keywords: Frequency Control, Gain Control, Piezoelectric Transducer, Power Converter, Self-tuning.

A Single-Stage PV Module Integrated Converter (MIC) with High Voltage Gain Capability
by Ching-Ming Lai, Yi-Hung Liao

Vol. 6. n. 2, pp. 587-592

Abstract - In this paper, a single-stage photovoltaic (PV) module integrated converter (MIC) with high voltage gain capability and galvanic isolation is presented. Moreover, a fast maximum power point tracking (MPPT) strategy with linear current control is adapted in the proposed PV MIC. Finally, a speciation of 150W/110V_rms output prototype is constructed, and experimental results indeed verify the effectiveness of the proposed converter.

Keywords: PV Module Integrated Converter, High Voltage Gain.

Electromagnetic Interference Filter Design Based on Noise Impedance Measurements for Switching Power Converters
by R. Vimala, K. Baskaran

Vol. 6. n. 2, pp. 593-598

Abstract - Fast switching in power converters generate large amount of Electromagnetic interference (EMI). Two modes of conducted EMI noise: The Differential-mode (DM) and the Common-mode (CM) are identified by frequency domain measurements associated with an ac–dc half-bridge converter. The proposed method is used to reduce the CM and DM noise of a Switching Power Converter (SPC). The frequency range of the conducted emission limits from 150 kHz to 30 MHz. This paper introduces an improved and simplified method to design EMI filters for switching power converters. This method uses the practical approach of measuring the power converter noise spectrum and using the data to calculate the maximum possible magnitude and minimum possible magnitude of the differential mode and common mode noise impedances. The noise impedance magnitude information aids the design of the EMI filter. The analysis and experimental results show that this method can guarantee that the required attenuation can be achieved, especially at low frequencies.

Keywords: Electromagnetic Interference, Noise Impedance, Switching Power Converters, Common Mode And Differential Mode, Conducted EMI.

Optimization of Inductor Based on Genetic Algorithm for the Medium Voltage Cascade Converter with Active Front End
by Liang Zhang, Guodong Chen, Xu Cai

Vol. 6. n. 2, pp. 599-606

Abstract - An optimization method based on genetic algorithm is proposed to design an optimal inductance value for the medium voltage cascade converter with Active Front End. Several aspects influencing the inductor option are firstly discussed, including the line current ripple, the dynamic response performance, the space requirements, and the efficiency. Then, according to the discussion, a nonlinear multi-objective mathematical model for the inductance optimization is presented. To validate the method advantages, some simulations are done in MATLAB/PLECS. Experiments are also tested in a prototype. The corresponding results demonstrate that the optimization reduces the inductance value, which not only meets the requirements, but also improves the device structural design.

Keywords: Medium Voltage Converter, Cascade Multi Level, Active Front End (AFE), Optimization, Genetic Algorithm.

A Hysteresis Current Control Strategy for Common-Mode Voltage Reduction in AC Drive Systems

by M. Ebrahim Adabi, A. Vahedi

Vol. 6. n. 2, pp. 607-617

Abstract - This paper presents a current control strategy to reduce the maximum common mode voltage levels of three-phase two-level inverters in adjustable speed drives application. Any reduction of the common mode voltage leads to a decrement of the high frequency related issues of AC drives such as leakage current, EMI noises, shaft voltage and motor bearing damages. A comparative study with other famous hysteresis switching strategies shows that proposed method decreases the switching frequency. Also, a three-level inverter, has seven different values of common mode voltages. Elimination of switching vectors which leads to maximum common mode voltage levels from the switching algorithm is the best option in controlling common mode voltage. In this structure, the quality of the current waveform increases due to variety of switching options. Mathematical analyses have been verified through Simulations to investigate the presented method.

Keywords: Hysteresis Current Control, AC Drives, PWM Inverters, Common Mode Voltage.

A Novel Modified Space Vector Pulse Width Modulation Technique for High Performance Z-Source Inverter
by U. Shajith Ali, V. Kamaraj

Vol. 6. n. 2, pp. 618-623

Abstract - The high performance Z-source inverter is a new topology, which provides the circuit with bi-directional power flow ability. This inverter can overcome the limitations of the basic Z-source inverter and be used as an interface between energy storage and supply networks. A novel modified space vector pulse width modulation (SVPWM) algorithm for high performance Z-source inverter is presented here, which improves the voltage gain during the boost mode. In the proposed modified SVPWM the shoot-through states are evenly assigned to each phase within zero state. So zero voltage time period is diminished for generating a shoot-through time, and active states are unchanged. Simulation and experimental results are presented to demonstrate the new features.

Keywords: Current Source Inverter, Space Vector PWM, Total Harmonic Distortion, Voltage Source Inverter, Z-Source Inverter.

A Zero-Voltage-Switching Resonant Flyback Converter with Single Magnetic Component
by Hyun-Lark Do

Vol. 6. n. 2, pp. 624-629

Abstract - A zero-voltage-switching (ZVS) resonant flyback converter with single magnetic component is presented in this paper. In the proposed converter, a simple auxiliary circuit consisting of an auxiliary switch and a resonant capacitor is added to a conventional flyback converter. By utilizing the resonance between the leakage inductance of transformer and the resonant capacitor, ZVS operation of both main and auxiliary switches and zero-current-switching (ZCS) operation of an output diode are achieved. Therefore, switching loss is significantly reduced and the proposed converter provides high efficiency. Moreover, the voltages across the power switches are clamped as the resonant capacitor voltage and the output diode voltage is also clamped without any auxiliary circuits. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.

Keywords: Flyback Converter, Soft-Switching, Zero-Voltage-Switching, Zero-Current-Switching.

The Effect of Winding Structure on the Current Distribution of Paralleled Wires in High Frequency Transformers
by B. Abdi, R. Alaei, A. Darvishi, A. Alimardani

Vol. 6. n. 2, pp. 630-635

Abstract - High frequency transformers, used in switching power supplies, carry high amount of current. High frequency effects like skin, proximity and edge effects are discussed in this paper. Multi stranded or litz wires are used for reducing skin effect, but it will be shown that they are not effective in transformer normal winding. Paralleled interleaved winding is presented for reducing the high frequency effect. Two dimensional simulations based on finite element method are done for investigation of current distribution in high power, high frequency transformers. Finally experimental results are given for normally winded and paralleled interleave winding in the high frequency transformer. Experimental results confirm the discussion and finite element method simulation results.

Keywords: Skin Effect, Proximity Effect, Edge Effect, Current Sharing, HF Transformer, SMPS.

Recurrent Neural Network Based Nonlinear State Estimation for Induction Motors
by Saadettin Aksoy, Aydın Mühürcü

Vol. 6. n. 2, pp. 636-645

Abstract - This study presents a recurrent neural network (RNN) based nonlinear state estimator which uses an Elman neural network structure (ENN) for state estimation of a squirrel-cage induction motor. Proposed algorithm only uses the measurements of the stator currents and the rotor angular speed, and learns of the dynamic behavior of the state observer from these measurements, through prediction error minimization. A squirrel-cage induction motor was fed from sinusoidal, six-steps, and Pulse Width Modulation (PWM) supply sources at different times in order to observe the performance of the proposed estimator for different operation conditions. Estimation results showed that the proposed algorithm is capable of estimating the states of an induction motor and it performs better than Extended Kalman Filtering (EKF) in terms of accuracy and convergence speed.

Keywords: Induction Motor, State Estimation, Extended Kalman Filtering, Recurrent Neural Networks.

Analysis of the Transient Operation of a Salient Pole Synchronous Machine During Stator and Field Internal Short Circuit Using F.E.M.
by S. E. Dallas, A. N. Safacas, J. C. Kappatou

Vol. 6. n. 2, pp. 646-654

Abstract - In this paper the performance of a 12-pole hydrogenerator during a field excitation and a stator inter-turn short-circuit is investigate, while the synchronous machine is connected to the 50 Hz grid. Mainly, the waveforms of all the machine currents (stator, field and damper), the electromagnetic torque and the electromagnetic field in the air-gap are derived and studied. In the inter-turn stator short-circuit analysis two different kinds of faults are considered, a short circuit between two conductors belonging to different phases and between two conductors belonging to the same phase. The calculation of the machine’s variables, the waveforms of the damper currents and the electromagnetic torque oscillations are obtained more easily and more precisely by the use of FEM than by other simulation methods.

Keywords: Damper Bars, Finite Element Method, Short Circuit Currents, Synchronous Generator Transient Analysis.

Induction Motor Real Time Application of Multimodel Modeling Approach
by Abid Aicha, Ben Hamed Mouna, Sbita Lassaâd

Vol. 6. n. 2, pp. 655-660

Abstract - As induction motor (IM) is a non linear system and it is a subject of several disturbances as load disturbances and parameters variation, it can be a real problem for a conventional modeling approach that don’t put up with relatively large model uncertainly and external disturbances. Therefore, in this paper, a robust IM model is presented. The robustness is guaranteed using multimodel approach. This approach consists of four steps which are clusters estimation, structure identification, parametric identification and local models combination. The collected data on IM are, firstly, clustered into several groups through a Chui’s clustering algorithm. Then, the structure identification is performed on each group using the instrumental ratio (RDI) method. Parameters of each sub model are identified using recursive least square (RLS) method. Finally, obtained sub models are combined using the validity concept. Experimental results for 1kw IM are presented and analyzed up on a dSpace system with DS1104 controller board based on digital signal processor (DSP) TMS320F240.

Keywords: Induction Motor, Chui’s Clustering Algorithm, Modeling and Multimodel Approach.

Design of Magnetostriction Phenomena in Electric Motors by Using Time Discretization

by A. Boulassel, M. R. Mekideche

Vol. 6. n. 2, pp. 661-670

Abstract - In this paper, the nodal displacements of magnetic cores of induction motor due to magnetostriction are studied. By using time discretization (step by step in the time) a magnetostriction model is used to design and computing the deformation of a ferromagnetic material (Fe-Si) due to magnetic forces and magnetostriction in electrical motors in 2D cases, the model based on magnetostriction measurements is needed. Displacements of nodes of the stator’s teeth are also calculated, the results indicate that magnetostriction forces must be accounted to study of vibrations and noises in electric machines.

Keywords: Time Discretization, Magnetostriction, Magnetic Forces, Induction Motor, Finite Elements Method.

Simulation and Experimental Set of Vector Controlled Induction Machine Using Power Line Communication for Speed Measurement
by F. Poitiers, C. Millet, C. Batard, N. Ginot

Vol. 6. n. 2, pp. 671-678

Abstract - This paper presents simulation results and experimental set of a vector controlled induction machine where the speed information is routed to the control board using Power Line Communication (PLC) device on a classical sinusoidal 230 V AC grid. After presenting the control strategy and the principles of PLC transmission, the authors present simulation results taking into account the delay induced by speed measurement with PLC modems. The simulation results are then compared to the results given by experimental set.

Keywords: Induction Machine, Vector control, Power Line Communication.

New External Rotor Switched Reluctance Motor in Comparison with Conventional SRM
by N. Arbab, H. Karim, H. Torkaman, E. Afjei

Vol. 6. n. 2, pp. 679-684

Abstract - In this paper a novel three-phase 6 by 8 external rotor switched reluctance motor is presented. The most important advantage of the proposed motor is producing high torque per volume in household and industry applications. This construction not only leads to reduction of the total torque per volume, but also increases the total efficiency in small size motor. Three dimensional finite element method is applied to evaluate the main characteristics of the proposed motor. These characteristics of the motor are compared to a conventional three-phase 8 by 6 SRM configuration with similar conditions. It is shown that the proposed motor has great advantages over the conventional type in production of minimum to maximum inductance ratio, which results in higher output torque per volume for the motor.

Keywords: Switched Reluctance Motor, External Rotor Configuration, Three Dimensional Finite Element Method, Comparative Study.

Hammerstein Based Modeling of Traveling Wave Ultrasonic Motors
by Hamed Mojallali, Mohamadreza Ahmadi

Vol. 6. n. 2, pp. 685-697

Abstract - TTraveling Wave Ultrasonic Motors (TWUSMs) possess extreme nonlinear properties such as dead-zone and saturation reverse effect, which are reliant on the driving conditions. These characteristics make modeling and control of TWUSMs quite problematic. In this paper, a new scheme for the identification of TWUSM’s Hammerstein model consisting of a nonlinear static function followed by a linear dynamical model is introduced. The nonlinear static function is identified using the Bezier–Bernstein polynomial functions. The identification method is based on a hybrid scheme including the inverse de Casteljau algorithm, the least squares method, and the Levenberg-Marquart (LM) algorithm. Simulation results and their validation with the data derived from experiments demonstrate the efficiency of the proposed scheme.

Keywords: Travelling Wave Ultrasonic Motor, Modeling, Bezier-Bernstein Polynomial Functions, Hammerstein Model, Levenberg-Marquart Algorithm.

Improving Sensorless Control of BLDC Motors by Offering a New Parameters Estimation Algorithm for BLDC Motors
by M. R. Rahmati, M. Jafarboland

Vol. 6. n. 2, pp. 698-705

Abstract - The existence of position sensors in the motor structure is one of the major problems of permanent magnet brushless dc (PM-BLDC) motors. In order to correct and optimized current commutation and also precise estimation of the motor speed meanwhile position sensors removal, various types of sensorless drives have been introduced which their algorithms estimate the rotor position. A group of these algorithms estimate the rotor position based on the calculating a function of the flux linkage. One of the major problems of this class of algorithms is the requirement to the exact values of motor parameters for correct operation, whereas motor parameters change as motor operation conditions change. Error in the motor parameters values can cause severe deterioration in the quality of rotor position and speed estimation and even lead to the motor instability. This paper proposes a new algorithm which is capable to estimate BLDC motors parameters quickly and accurately. Simulation results confirm good consistency between the parameters estimation algorithm and the sensorless algorithm.

Keywords: Current Commutation, Flux linkage, Permanent Magnet Brushless DC (PM-BLDC) Motors, Sensorless Control.

PI-Elman Neural Network Based Nonlinear State Estimation for Induction Motors
by Saadettin Aksoy, Aydın Mühürcü

Vol. 6. n. 2, pp. 706-718

Abstract - This study presents a nonlinear state estimator based on recurrent neural network (RNN) which uses a PI Elman neural network (PI-ENN) structure for state estimation of a squirrel-cage induction motor. Proposed algorithm uses the measurements of the stator currents and rotor angular speed. It learns the dynamic behavior of the state observer from these measurements, through the prediction error minimization. Since the stator currents are available for measurement it may appear that the stator current estimates are redundant but these estimates are actually filtered version of the measured stator currents. We also include these variables to the state vector for completeness of the algorithm and to check the results. In order to observe the performance of the proposed estimation algorithm for different operation conditions the squirrel-cage induction motor was fed with various supply voltages, such as sinusoidal, six-steps, and pulse width modulation (PWM) waveforms. Estimation results show that the proposed algorithm performs better than for the extended Kalman filter (EKF) in terms of accuracy and convergence speed.

Keywords: Induction Motor, Extended Kalman Filter, State Estimation, Recurrent Neural Networks, PI Elman Neural Network.

Stray Capacitance and Sensitivity Coefficients Ratio in One Turn of MFCG Coil
by M. E. Mosleh, M. R. Besmi

Vol. 6. n. 2, pp. 719-730

Abstract - TCalculation of Magneto Flux Compression generator (MFCG) parasitic parameters, such as capacitance, is fundamental to predicting the frequency behavior of the MFCG generator, reducing this capacitance value and moreover, for more advanced aims of capacitance integration and cancellation. This paper presents a comprehensive procedure for calculating all contributions to the stray capacitance (SC) of high-voltage MFCG generators and provides a detailed analysis of the problem, based on a physical approach and physic-basic laws. In this paper, the advantages of the analytical formulation for calculation SC of MFCG are discussed. The approach and formulas presented in this paper can be used for other wound components, for example, electrical machines, and also can be use for calculation of SC in physic sciences. Furthermore, in this paper SC analytical results by using of vespiary regular hexagonal (VRH) model is presented for high frequency MFCG generators coil with circular cross-section. Presented approach in this paper is based on the geometrical structure of single-layer wire filaments in one turn of the generator coil. Also, the sensitivity coefficients’ ratio of effective parameters is discussed and analyzed. Finally, we will see that in order to decrease the total SC of one turn of the MFCG coil; we should increase the number of conductor wire filaments in one turn.

Keywords: Analysis of Effective Parameters, Magneto Cumulative Generator, Stray Capacitance, Winding Pitch, Vespiary Model, High Frequency.

Vector Control of Four-Phase Induction Machines with Two Current Sensors
by H. P. Nabi, P. Dadashi, A. Shoulaie

Vol. 6. n. 2, pp. 731-738

Abstract - Increasing the phase number enables reduction of the power per inverter leg, improvement of efficiency, reduction in torque ripples and etc. However, increasing the phase number causes the need of more power electronic devices and peripheral equipments such as sensors. Furthermore, in vector control of induction machine for controlling the d-q current components, measuring all independent currents is needed. Therefore, in this paper, a novel and simple structure is proposed for vector control of four-phase induction machines with only two current sensors. Although, it is shown in this paper that zero sequence current components will be eliminated due to the proposed structure. The simulation and experimental results verify the performance of proposed structure

Keywords: Symmetrical Four-Phase Induction Machine, Vector Control, Current Sensor, Multiphase Drives.

A Comparative Approach within Chemical Battery, Flywheel and Supercapacitor Base Energy Storage System for LEO Satellite Applications
by B. Abdi, A. Alimardani, J. S. Moghani, S. H. Hosseinian

Vol. 6. n. 2, pp. 739-744

Abstract - This paper presents three energy storage systems, based on chemical batteries, flywheels and supercapacitors as the energy source of low earth orbit satellites in eclipse duration. Each system is designed and optimized with regard to energy requirement of a typical LEO satellite and various vital parameters in satellites which are discussed. The storage system and electronic interface are presented to give an adequate view for comparing them in different aspects. Afterwards, a comparison between these energy storage systems (ESSs) is applied considering their efficiency, reliability, weight, operational temperature and self-discharge dissipation (trickle charge). Finally, the conclusion presents the most recommended systems in order of their capability.

Keywords: Energy Storage System, Chemical Battery, Flywheel, Supercapacitor, LEO Satellite.

Design and Analysis of Outer Rotor in-Wheel Motor
by A. Fenercioğlu, M. Dursun

Vol. 6. n. 2, pp. 745-751

Abstract - In this study, an Outer Rotor Switched Reluctance Motor (OR-SRM) was designed and calculated for electrical vehicle by finite element method (FEM). This motor has very simple geometrical structure. It has no rotor winding, bar, magnet, brush and bracelet. The OR-SRM has outer rotor and it generates high torque because diameter of rotor is enlarged. The OR-SRM which is installed in wheel drive the vehicle directly. It doesn’t require gear box. Proposed OR-SRM has a 12 / 8 pole combinations, 3 phases, 5 kW power and 1200 rpm maximum speed. This study presents determination of motor geometrical structure parameters. Power, torque, inductance parameters and magnetic model of the OR-SRM are examined. The OR-SRM is analyzed by Maxwell 3D field simulator. Analysis results are verified by analytical calculations. The motor phase inductance profile, instantaneous torque values are predicted in a variety of rotor positions obtained from simulation results. Approximately 40 Nm of torque are calculated for 5 kW, 1200 rpm speed.

Keywords: Wheel Motor, In Wheel SRM, Outer Rotor SRM.

Performance Analysis of a Disc Type BLDC Motor for Electric Vehicles
by Abdolamir Nekoubin

Vol. 6. n. 2, pp. 752-759

Abstract - TThe objective of this paper were to determine by computer simulation and laboratory test the electromechanical characteristics of a double-sided axial flux permanent magnet brushless DC (AFPM BLDC) motor with two-phase winding. To study the motor operation, a mathematical dynamic model has been proposed for motor, which became the basis for simulations that were performed using MATLAB/SIMULINK software package. The results of simulations were presented in form of the waveforms of selected quantities and the electromechanical characteristics performed by the motor. The calculation results show that the two-phase motor version develops smooth torque and reaches high efficiency. An experimental device is developed to compare experimental and simulated results. The results obtained from the test practically do not differ from those obtained from simulation. The two-phase motor can be applied where more smooth torque is required. Finally a study on the influence of switching angle on motor performance shows that when advance switching technique is used, the motor operates with the highest efficiency.

Keywords: Brushless DC motor, Switching angle, Inverter, Dynamic.

Axial-Flux Permanent-Magnet Brushless DC Traction Motor for Direct Drive of Electric Vehicle
by N. A. Rahim, W. P. Hew, A. Mahmoudi

Vol. 6. n. 2, pp. 760-769

Abstract - This paper presents the design of an inside-out axial-flux permanent-magnet brushless dc motor for direct traction drive in an electric vehicle. The prototype motor is a double-sided axial-flux permanent-magnet motor with non-slotted stator. The preliminary design had 16 rotor poles, for high torque density and stable rotation at low speed. The design was simulated via Finite Element Method Magnetics (FEMM) Software, for obtainment of design parameters. The motor was fabricated and tested in an in-wheel test-bed. There exist close agreements between the simulated and experimental results

Keywords: Axial-Flux Permanent-Magnet Motor, Electric Vehicle, Finite Element Analysis.

Optimum Design of Switched Reluctance Machine for Electric Vehicle Applications Using Chaotic Particle Swarm Optimization
by M. Balaji, V. Kamaraj, S. Ramkumar

Vol. 6. n. 2, pp. 770-776

Abstract - This paper proposes design optimization of Switched Reluctance Machine (SRM) for electric vehicle applications using chaotic Particle Swarm Optimization (PSO). Two different PSO approaches based on chaotic sequences using logistic equation are proposed in this work. The objective function considered is a correct compromise between maximum average torque, maximum average torque per motor lamination volume and maximum average torque per copper loss. The three most influential parameters, the stator pole arc, the rotor pole arc, and the bore radius on the performance of the machine are chosen as optimization variables. The feasibility of the proposed method is demonstrated for an 8/6, four-phase, 5 HP, 1500 rpm SRM and compared with classical PSO and Genetic Algorithm (GA) method. The results show that the proposed method is effective and robust.

Keywords: Average Torque, Chaotic Sequences, Particle Swarm Optimization, Switched Reluctance Machine.

Control of a Flexible Platform for Photovoltaic Grid-Connected Systems Using a DSP-Microcontroller Arrangement
by Alexis B. Rey-Boué, Francisco Ruz-Vila, José M. Torrelo-Ponce, Salvador Subiela-Valls

Vol. 6. n. 2, pp. 777-788

Abstract - In this paper, a flexible platform for the connection of Solar Photovoltaic Panels to the utility grid is developed. The platform is made with the Power Subsystem, which includes a DC/DC boost converter and a 3-phase DC/AC converter as the main devices, together with the Control Subsystem, which includes a DSP-microcontroller arrangement made by a floating-point DSP and a fixed-point microcontroller. A detailed mathematical model of the plant is described for analysis purposes and the real-time control algorithms for the DC/DC and DC/AC converters are established. Both processors are intended to do real-time control in an easy way, and the communication process between them is carried out with the McBSP bus in a MASTER/SLAVE configuration. The flowcharts of the main programs in both processors are shown together with the detail explanation of the interrupt capabilities employed: the DC/DC boost converter is controlled by selecting the adequate duty cycle in real time, whereas the DC/AC converter is managed by a d-q control approach where the decoupled regulation of the instantaneous active and reactive powers fed to the 3-phase utility grid is achieved, allowing unitary power factor operation. Several measurements of the involved variables of the platform are shown in order to evaluate the performance of the exerted control algorithms. The possibility of exerting future complex algorithms and high computational tasks are also validated

Keywords: PV Panels, DSP-Microcontroller, d-q Control, DC/DC Boost Converter, 3-phase VSI.

International Review of Electrical Engineering - Papers- Part B

Optimal Placement of FACTS Devices in Large Power System Using PSO Method
by L. Boumediene, K. Hartani

Vol. 6. n. 2, pp. 789-796

Abstract - In this paper, we propose an approach for the optimal location of SVCs in the electrical network. This approach uses Load flow control the violation of the network nodal voltages. This mathematical approach permits to obtain maximum loss reductions for each of types of optimally placed of FACTS. Moreover, voltage profile improvement and branch current reduction are obtained.The application of the proposed method on two electrical networks at 14 bus and at 68 bus. We have expanded our work by the injection of SVC (static VAR compensator) on the electrical networks of 14 bus and 68 bus to control the tension and application development with a program on MTALAB.

Keywords: FACTS, PSO, TTC, TCSC, SVC.

Voltage Stabilization of Electrical Network by Using UPFC Compensator Commanded by Fuzzy Controllers
by Houda Jouini, Souad Chebbi, Kamel Jemai

Vol. 6. n. 2, pp. 797-809

Abstract - The capacity to maintain the electric network reliability by ensuring the good quality of the electric quantities to be deliver to users became one of the major challenges as well as for the energy producers and the consumers facing this challenge, several research in this field are started. Some works were directed towards the study of the voltage profile; this profile is one of electric network reliability factor. Moreover, the FACTS use represents one of the efficient ways allowing the stability voltage control. In this context our contribution consists in implementing a new voltage stabilization strategy. Our strategy was tested on the IEEE 14 buses network with the presence of fault conditions putting the network in a critical state. This strategy rests on the reactive power quantity estimation to inject by a static compensator, UPFC, provided with fuzzy logic regulators of the fault occurrence phase in a given network point. We expose, in the present paper, our new strategy which ensures the reactive quantity estimation procedure that the UPFC must exchange with the network remainder aiming to stabilize the voltage at each bus in order to avoid the voltage collapse phenomenon which worries all the nations. The proposal innovation consists in ensuring a perfect decoupling between the UPFC converters and the point of fault occurrence.

Keywords: Voltage Collapse, Fuzzy Controller, UPFC, FACTS.

Minimization of Power Transmission Losses in Series Compensated Systems Using Genetic Algorithm
by Fatma Gul Bagriyanik, Zehra Elif Aygen, Mustafa Bagriyanik

Vol. 6. n. 2, pp. 810-817

Abstract - The optimal allocation of reactive power sources considering location and size is one of the most important problems for a power system operator. In general, only active power losses are considered for minimization, and the optimization problems are solved by controlling generator terminal voltages, transformer tap positions and shunt VAR sources. However, the generator reactive power limits contribute to voltage stability, and minimization of the reactive power losses has a beneficial effect on ensuring an adequate spinning reactive power reserve. In this paper, the series reactive power losses are also included to the objective function, a sensitivity analyses based procedure using genetic algorithm is proposed for the solution of the problem. Thyristor Controlled Series Capacitors (TCSC) are considered as an addition control device, because the series compensation has a big effect on the series reactive power losses. The resulting optimization problem is solved using genetic algorithm. The proposed method is applied to standard test systems and the results are presented.

Keywords: Reactive Power Dispatch, Series Compensation, Genetic Algorithms (GAs), Power Systems, Power Flow.

Simultaneous Power Flow Control and Voltage Support Using UPFC
by S. M. Shirvani Boroujeni, R. Hemmati, H. Delafkar, A. Safarnezhad Boroujeni

Vol. 6. n. 2, pp. 818-825

Abstract - This paper presents the application of Unified Power Flow Controller (UPFC) in order to simultaneous power flow control and voltage support and also transient stability improvement at a Single-Machine Infinite-Bus (SMIB) power system installed with UPFC. PI type controllers are considered for power flow and voltage control and the parameters of these PI type controllers are tuned using Particle Swarm Optimization (PSO) and Genetic Algorithms (GA). Also a stabilizer supplementary controller based UPFC is considered for increasing power system damping and stability enhancement. In order to UPFC performance study and also comparison of PSO and GA, the SMIB power system is simulated under different scenarios. Numerous simulations show the ability of UPFC in simultaneous power flow control and voltage support and also stability enhancement by damping of power system oscillations. Simulation results emphasis on the better performance of PSO in comparison with GA.

Keywords: Unified Power Flow Controller, Low Frequency Oscillations, Power Flow Control, Voltage Control, Particle Swarm Optimization, Genetic Algorithms.

A Novel Genetic Algorithm for the Coordinated Optimal Reactive Power Dispatch in Power Systems with Wind Farms and FACTS
by M. Alonso, H. Amarís, M. Chindris

Vol. 6. n. 2, pp. 826-835

Abstract - Optimal reactive power dispatch of large-scale power systems with great amount of wind farms is one of the main issues in power systems operation. This paper focuses on the incorporation of reactive power capacity from Flexible AC Transmission Systems (FACTS) and from variable speed wind turbines in a coordinated reactive power dispatch. The reactive power capability of Double Fed Inductor Generator (DFIG) considers the capacity of the machine as well as the one of the grid side converter. The Optimization strategy is thus based on genetic algorithms (GA) and includes in its formulation the reactive power capability of DFIG and the reactive power injection of Static Var Compensators (SVC). The suitability of the proposed methodology is tested on a real 140-bus power system in order to determinate an optimal reschedule of the reactive power injection from different VAR sources minimizing, at the same time, the real power losses of the whole power system.

Keywords: Reactive Power Dispatch, Wind Energy, Genetic Algorithms, FACTS.

Available Transfer Capability Determination by Incorporating Reactive Power Flow in Deregulated Power Systems
by S. Charles Raja, P. Venkatesh, B. V. Manikandan, S. C. Srivastava

Vol. 6. n. 2, pp. 836-846

Abstract - Transmission networks throughout the world are being regulated to ensure a competitive, open and reliable market in this new deregulated environment. One of the key concepts is to quantify the remaining transfer capability in the supply system accurately and rapidly for further transactions, which is termed as Available Transfer Capability (ATC). Generally in the determination of ATC using linear sensitivity factors such as Power Transfer Distribution Factors (PTDFs), the effects of reactive power flows in line loading are neglected. This leads to a number of potential errors in ATC calculation and accuracy is very much affected. This paper describes a simple, fast and non-iterative method which incorporates the effect of reactive power flows directly in ATC determination using a new set of distribution factors namely Apparent Power Transfer Distribution Factor (STDF) and Line Outage Apparent Power Transfer Distribution Factor (LOSTDF). Single area ATC and multi-area ATC have been calculated using the above factors for both normal mode and (n-1) line outage contingency mode operations. The accuracy and validity of the proposed method has been tested by considering both bilateral and multilateral wheeling transactions in the IEEE 30 bus system and Indian 69-bus utility systems.

Keywords: Deregulation, Available Transfer Capability, Power Transfer Distribution Factor, Apparent Power Transfer Distribution Factor, Line Outage Apparent Power Transfer Distribution Factor, Performance Index, Contingency Analysis.

Design and Development of ANFIS Controller for STATCOM in dSPACE Environment
by S. Arockia Edwin Xavier, P. Venkatesh , M. Saravanan

Vol. 6. n. 2, pp. 847-854

Abstract - Reactive power compensation is an important issue in the control of electric power system. Reactive power from the source increases the transmission losses and reduces the power transmission capability of the transmission lines. Moreover, reactive power should not be transmitted through the transmission line to a longer distance. Hence Flexible AC Transmission Systems (FACTS) devices such as static compensator (STATCOM) unified power flow controller (UPFC) and static volt-ampere compensator (SVC) are used to alleviate these problems. In this paper, a voltage source converter (VSC) based STATCOM is developed with PI and Adaptive Neuro Fuzzy Inference System (ANFIS) controllers. The conventional PI controller has more tuning difficulties while the system parameter changes, whereas an ANFIS controller requires less computation time and characteristics of both fuzzy and neuron controllers. The ANFIS has the ability to generalize and can interpolate in between the training data as well as the membership function has been decided according to the training data. The ANFIS controller designed was tested on a 75V, 100VA STATCOM in real time environment via state- of- the- art of digital signal processor advanced control engineering (dSPACE) DS1104 board and it was found that it was producing better results than the PI controller.

Keywords: ANFIS, dSPACE DS1104, STATCOM, PI controller, PWM.

A Novel Approach to Optimal Power Flow Problems in Power Systems Embedded with Various DG and FACTS Devices
by Tsao-Tsung Ma

Vol. 6. n. 2, pp. 855-862

Abstract - This paper presents a universal approach to the optimal power flow (OPF) problem in power systems embedded with various distributed generators (DG)and flexible ac transmission systems (FACTS) devices using real-valued genetic algorithms (RGA). In the study, the most versatile FACTS device, unified power flow controller (UPFC), is used as a generalized model to investigate performances of various DG and FACTS devices in targeting a set of assigned power flows and optimization objectives. A general power injection model taking into account the desired control functions and the related parameters of various DG and FACTS devices is developed and verified. A regular RGA working with a close-loop controlled power flow program is utilized to directly search the best FACTS regulation parameters and generation dispatches for minimizing the cost function and/or the real power losses. The feasibility and effectiveness of the proposed solution methods are verified with comprehensive simulation studies on IEEE test systems.

Keywords: Optimal Power Flow, Real-Valued Genetic Algorithm, Distributed Generation, FACTS, Unified Power Flow Controller.

A Novel Hybrid GA-PSO Technique for Optimal Tuning of Fuzzy Controller to Improve Multi-Machine Power System Stability
by O. Abedinia, Mohammad S. Naderi, A. Jalili, A. Mokhtarpour

Vol. 6. n. 2, pp. 863-873

Abstract - This paper presents a design of FPSS using hybrid GA and PSO to damp low frequency oscillation in multi-machine power system where the parameters of proposed controller are optimized offline automatically by the hybrid techniques. This newly proposed controller is more efficient because it cope with oscillations and different operating points. In this strategy the controller is tuned on line from the knowledge base and fuzzy interference. For achieving the desired level of robust performance in fuzzy controller, exact tuning of rule base and membership functions are very important. The motivation for using the GA and PSO as a hybrid method are to reduce fuzzy effort and take large parametric uncertainties in to account. This newly developed control strategy mixed the advantage of GA and PSO techniques leads to a flexible controller with simple structure while is easy to implement. The New England 10-unit 39-bus standard power system, under various system configurations and loading conditions, is employed to illustrate the performance of the proposed method. The effectiveness of proposed controller is compared with robust PSS that tune using TS and the fuzzy controller which is optimized rule base by GA through FD and ITAE performance indices. Simulation results show the effectiveness of the proposed PSO-based fuzzy membership function of power system stabilizer and GA-based fuzzy rule base of PSS to damp the oscillation of multi-machine system and work effectively under variable loading and fault conditions.

Keywords: Fuzzy, PID, Genetic Algorithm, Particle Swarm Optimization, Multi Machine System.

Evaluation of Fault Location based on Voltage Sags Profiles: a Study on the Influence of Voltage Sags Patterns
by H. Mokhlis, Hasmaini Mohamad, A. H. A Bakar1, H. Y. Li

Vol. 6. n. 2, pp. 874-880

Abstract - TResearch and development of fault location techniques for distribution system have been given a great emphasis to enhance reliability and quality of power supply. In a recent work, a comprehensive fault location method based on voltage sag profile has been proposed. In relation with this method, this paper presents a further test to evaluate the method performance by using a non-homogenous and unbalanced distribution network. A focus is given more on the influence of voltage sags patterns to the performance of the method. The test results present the strength and limitation of the method when applied for different fault resistances, loading variation and load models.

Keywords: Fault Location, Distribution Network, Unbalanced, Non-homogenous, Voltage Sags Profile.

A Benders Decomposition Approach for Optimal Wind Capacity Allocation to Power System with Security Constraints
by M. Nick, G. H. Riahy, S. H. Hosseinian, F. Fallahi

Vol. 6. n. 2, pp. 881-887

Abstract - Wind energy is leading technology among renewable energy resources, and many countries have ambitious wind energy plans for future. Wind-rich sites which are a variable source of energy, are mostly located in remote areas that transmission network in these areas cannot absorb additional power from new wind sites. Therefore, a non-physically firm connection strategy is key to its cost-effective and timely integration to presently constrained transmission networks. This problem is computationally challenging and a proper method is needed to relieve this computationally burden of the problem. In this paper, it is shown that the large-scale linear programming is exploitable by benders decomposition method. Hourly wind speed data are used to accurately model the effects of wind speed pattern on unit commitment (UC) and DC optimal power flow (OPF) problem for an entire year. The results show effectiveness of a proper wind capacity allocation method on the total investment and operation costs and overall wind energy penetration into the power system

Keywords: Wind Energy, Benders Decomposition, Power System Planning, Constrained optimization.

Damping Controller Design for Power System Oscillations Using Hybrid GA-SQP
by Mahdiyeh Eslami, Hussain Shareef, Azah Mohamed, Mohammad Khajehzadeh

Vol. 6. n. 2, pp. 888-896

Abstract - In this paper, a hybrid optimization method, GA–SQP, is described in which the genetic algorithm (GA) is a stochastic method is combined with the sequential quadratic programming (SQP) method, which is a deterministic method. The power system stabilizers (PSSs) parameters tuning problem is converted to an optimization problem which is solved by hybrid GA- SQP optimization algorithm. It was shown that although the SQP is fast, it is not able to solve this problem properly and is very sensitive to the choice of initial point. The GA was able to solve the problem after a large number of generations. It was shown that the proposed method is able to determine the final solution considerably faster than the GA while it is not sensitive to the initial point. GA is the main optimizer of the algorithm, whereas SQP is used to fine tune the results of GA to increase confidence in the solution. The New England 10-unit 39-bus standard power system, under various operation conditions, is employed to illustrate the performance of the proposed method. The results are very encouraging and suggest that the hybrid GA–SQP algorithm is very efficient in damping improvement of the power system.

Keywords: Multi-Objective Optimization, Hybrid, Design PSS, GA, SQP.

Effect of Static Synchronous Series Compensator on Damping Oscillation in Power System Enhancement
by A. Saidi, H. Hadj Abdallah

Vol. 6. n. 2, pp. 897-906

Abstract - This paper describes the damping of power system oscillation using a static synchronous series compensator (SSSC). The SSSC mathematical model and the controller structure to damp oscillation and stabilize the power system voltages are investigated. Simulations are performed with the Power System Analysis Toolbox (PSAT). Both cases of single-machine infinite-bus and multi-machine power systems are studied over a wide range of disturbances. The results obtained show the effectiveness and robustness of the SSSC on power system stability.

Keywords: Transient Stability, Voltage Stability, SSSC, PSAT, Damping.

Optimal Design of PID Power System Stabilizer in Multi-Machine Power System Using PSO and Genetic Algorithm
by A. Jalilvand, R. Aghmasheh, E. Khalkhali

Vol. 6. n. 2, pp. 907-913

Abstract - This paper presents Optimal tuning of Proportional-Integral-Derivative Power System Stabilizers (PID-PSS) using evolutionary optimization algorithms. The problem of selecting the parameters of the PSS for a multi-machine power system is converted to an optimization problem with the eigenvalue-based objective function. Two well known heuristic optimization methods, Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) are used for PID-PSS parameters tuning based on minimizing the objective function. The results are compared with each other and also eigenvalue analysis is used for comparison. The proposed method is confirmed by obtained simulation results of a three-machine power system under different operating conditions.

Keywords: Power System Stabilizer, Evolutionary Algorithms, PID, Root Locus.

Voltage Stability Analysis Using the Variable Gradient Method
by Ahmet Cifci, Yilmaz Uyaroglu, Ahmet Turan Hocaoglu

Vol. 6. n. 2, pp. 914-921

Abstract - Power system stability is usually the situation that a power system is in an acceptable operation state and that it is capable of returning to the normal equilibrium state after a disturbance. Voltage stability and collapses began to play a significant role in power system analysis and control as a result of energy system collapses in various places of the world. In this paper, by applying the variable gradient method to a four-bus system, the system’s energy function is created and thus the system’s energy level changes’ effects on the system’s stability is shown by using Macsyma program.

Keywords: Voltage Stability, The Variable Gradient Method, Energy Function.

Application of Bacterial Foraging Algorithm for Enhancement of Voltage Stability Using L-Index Approach
by M. Senthil Kumar, P. Renuga

Vol. 6. n. 2, pp. 922-929

Abstract - The unscheduled increment of load variation in power transmission system has driven the system to experience stressed condition leading to potential cascading trip on the entire system. This phenomenon has also led to voltage profile depreciation below the acceptable secure limit. The Voltage instability condition in a stressed power system could be improved by having effective reactive power compensation. Reactive power compensation can be accomplished by controlling the reactive power dispatch, reactive power injection on the load bus and controlling the tap changing of on- load-tap-changer (OLTC) transformer. This paper presents an application of Bacterial Foraging (BF) in optimizing the optimum rating of Static VAR Compensator (SVC) for voltage stability improvement in power system. The reactive power supplied by SVC is randomly distributed and it is the control variable in bacterial foraging algorithm and produces near optimal solutions. The proposed approach has been evaluated with four different objective functions namely, loss minimization, voltage profile improvement, voltage stability enhancement and total cost minimization. Voltage stability level of the system is defined based on the L-index of load buses. The IEEE 6, IEEE 14 and IEEE 30- bus systems were used as test systems to demonstrate the applicability and efficiency of the proposed method.

Keywords: Static Var Compensator (SVC), Bacterial Foraging, L-index, Voltage Stability.

On-Line Voltage Stability Preventive Control Considering Double Contingency
by Wei Gu, Rui Wang, Wei Liu, Zhi Wu

Vol. 6. n. 2, pp. 930-937

Abstract - This paper presents a mathematical model of security constrained optimal power flow based on the primal-dual interior point method. The model aims to minimize the control cost while taking into account voltage security constraints of power systems not only in normal state, but also in a contingency scenario. In on-line voltage stability assessment package, the set of contingencies is formed by means of screening and ranking considering double contingency in addition to the single one. Based on the above-mentioned mathematical model, preventive control is performed for each individual contingency in the set of contingencies in turn. The module of on-line voltage stability preventive control is constructed which can provide control strategies in time to ensure the secure operation of the system in case of the voltage unsecure state. Finally, simulation results of the IEEE 39, 118 and 300-bus test systems validate the correctness of the proposed approach.

Keywords: Voltage Stability, Preventive Control, Optimal Power Flow, Interior Point Method, Double Contingency, Screening and Ranking.

Design and Analysis of a Novel Dual-input PSS for Damping of Power System Oscillations Employing RCGA-Optimization Technique
by A. D. Falehi, M. Rostami

Vol. 6. n. 2, pp. 938-945

Abstract - In this paper, a dual-input Power System Stabilizer (PSS) is proposed to damp the low frequency oscillations in power system. The performance of proposed dual-input PSS has been compared with single input Conventional PSS (CPSS). The Real Coded Genetic Algorithm (RCGA) optimization technique is employed to optimum tune the parameter of both the single-input and dual-input PSS in order to improve the power system stability. Having the high sufficiency to solve the very non-linear objective, the RCGA technique is exerted to solve an optimization problem. The transient performance of these devices is evaluated considering three different conditions of disturbance in single-machine infinite-bus power system. Furthermore, to more investigate the role of proposed dual-input PSS in damping the power system multi-mode oscillations, a multi-machine power system (three-machine nine-bus) is considered. The results of nonlinear simulation suggest that with proposed dual-input PSS, power system stability is considerably improved than CPSS in single-machine power system. In addition, it is revealed that with proposed dual-input PSS, undesirable inter-area and local modes of oscillations in multi machine power system are superiorly damped than CPSS.

Keywords: Power System Oscillations, Conventional Power System Stabilizer, Dual-input Power System Stabilizer, Real Coded Genetic Algorithm, Single-machine Infinite-bus Power System, Multi-Machine Power System.

PQ Monitor-based Automated Fault Location Using Database Technique for 11kV Distribution System
by Chia Kwang Tan, V. K. Ramachandaramurthy

Vol. 6. n. 2, pp. 946-952

Abstract - Various fault locating techniques have been thoroughly discussed throughout the decades. Many of the techniques prior to this require many monitors and also relay operation information to accurately locate the fault. The latest fault locating approach utilizes power quality (PQ) monitors, which are faster and able to detect any short duration events. Majority of the fault locating techniques however focuses on locating downstream faults only. This paper proposes a novel technique to locate faults in several neighboring substations utilizing only one PQ monitor, thus breaking the boundaries of conventional downstream fault locating techniques. Besides locating faults in neighboring substations, this technique also allows the type of fault to be identified. The algorithm uses Three-Dimension (3D) Voltage Vector Database Matching method to accomplish this task. The algorithm proposed in this paper can accurately point to the fault location. Successful identification of fault location using this proposed technique will allow engineers to identify incipient faults in the substation. This will certainly revolutionize the way engineers plan and execute their substation maintenance strategy.

Keywords: Fault Location, Database Method, Power Quality Monitoring, Substation Predictive Maintenance.

Congestion Cost Allocation Base on Contribution for Pool Market
by M. P. Abdullah, M. Y. Hassan, F. Hussi

Vol. 6. n. 2, pp. 953-959

Abstract - In power system operation, congestion refers to an event where a transmission line becomes overload. Under pool-based electricity market, congestion is solved by re-dispatching the generation output at a cost known as congestion cost. This cost is then allocated to the electricity market participants as security charges. In the current markets, the allocations of congestion cost are based on either the participants’ MW demand or their location in the system. It does not reflect the participants’ contribution towards congestion problem. Furthermore, it allocates the cost entirely to the loads while the generators are not charged. This paper proposes a new approach for allocating the congestion cost, which is based on each participant’s contribution towards congestion problem. The one that cause more problem will be charged more and vice versa. The cost is also shared between generators and loads. The approach is illustrated using a simple three bus system and tested on the IEEE-30 bus and IEEE-118 bus system.

Keywords: Pool Market, Congestion, Congestion Cost Allocation, Market Dispatch.

A New Economic Benefit and Use of System Method for Transmission Expansion Cost Allocation in the Competitive Market Environment
by Javad Nikoukar, M. R. Haghifam, G. R. Yousefi

Vol. 6. n. 2, pp. 960-966

Abstract - The expansion of transmission systems impacts many entities in the market environment. Each entity may fare better or worse as a result of congestion relief in the presence of new facilities. Negatively affected firms apply their authority to prevent the expansion from taking place. The opposition of these firms and the lack of appropriate incentives results in insufficient investments in transmission assets. The network is being frequently used at its maximum limits, leading to economic inadequacies and reduced reliability. Hence, there is a necessity for effective encourage schemes for system expansion. The objective of this paper is to introduce a simple transmission expansion pricing scheme using economic benefit and use of system method, to allocate and price the transmission expansion among the participants.
The proposed method can utilize clearly, intelligible and the fairer for transmission expansion cost allocation between the participants at the different uncertainty such as adding the new line, augmenting the new generator and adding the new load to the system. Numerical example using a test power system is presented to illustrate the effectiveness of the studied method.

Keywords: Transmission Expansion, Cost Allocation, Economic Benefit, Use of System, Competitive Market.

Economic Evaluation of Uncertain Distributed Generations for a Distribution Company
by M. Sadeghi, A. Shishebori, F. Taki

Vol. 6. n. 2, pp. 967-973

Abstract - In this paper, the energy procurement for a distribution company (Disco) from the pool market and distributed generations (DGs) with a stochastic programming framework is presented. We propose a formulation that considers uncertainty of some parameters such as pool price, end user demand and the items which are related to DGs so that maximize the expected profit of Disco. This approach arrives at the optimal feasible DG investment plan under uncertainty of gas price, wind speed and solar radiation for gas fired DG, wind turbine generator and photovoltaic (PV) panel, respectively. Also the revenue of not producing emission gas by utilizing clean energy is considered.

Keywords: Distributed Generation Investment, Distribution Company, Pool Market, Stochastic Programming.

Electricity Tariff Design Based on Clustered Load Profiles Classified by Exploiting Questionnaires
by D. Mileta, M. Skok, Z. Simic

Vol. 6. n. 2, pp. 974-982

Abstract - Since the deregulation of electricity sector, load profiles of electricity customers are even more important because the knowledge gathered from load profiling can be used for various additional purposes. Special use is, for example, tariff design under market environment. In this paper new framework is developed for tariff design. This framework uses k-means algorithm for clustering samples of measured load profiles and makes classification by using decision trees for data from questionnaires which were filled by household customers. This way it is possible to maximize combined use of historic load measurements and simple information about various household customers.

Keywords: Electricity Market, Load Profiles, Data Mining, K-Means, Decision Trees, Clustering, Tariff Design.

Optimized Bidding Strategy of Generation Companies in the Energy and Reserve Markets by Game Theory

by Hassan Barati, Ali Habibzadeh, Ali Asghar Bagheri

Vol. 6. n. 2, pp. 983-991

Abstract - In this paper, a new bidding strategy will be modeled for the day-ahead market. Algorithm gained for this model, is produced by a company which its aim is to maximize its profit as a participant in the active power and spinning reserve. In this method, the forecasted energy price method, and the forecasted reserve price are used as the bidding strategy of possible price of a generation company in both markets. For determination of the reserve amount, two pricing models are used in combined markets. A bi level optimization method in which in the first level the subject of maximizing the profit of the generation companies individually is solved in order to get the amount of optimized energy suggested in the markets, and in the second level of optimization, the amount of the energy devoted to each generating unit as a an independent system operator (ISO) will be determined, by use of the results of the first level and network problems. In this paper, game theory is used to organize optimization model. Also, a six bus system is used to indicate the application of the presented model as well as considering its sufficiency.

Keywords: Nash Equilibrium Point, Energy Market, Independent System Operator, Spinning Reserve, Game Theory.

A Mixed Active-Passive Algorithm for Islanding Detection of Wind Turbine DG Units

by Behrooz Sobhani, Hossein Kazemi Kargar, Adel Akbarimajd

Vol. 6. n. 2, pp. 992-999

Abstract - – A new islanding detection algorithm method based on combination of passive and active techniques is presented for wind turbines as distributed resource units at the distribution voltage level. In the first step of the proposed algorithm, the rate of change of output active and reactive power is calculated. If these values exceed a predetermined threshold, the islanding is likely occurred. To verify happening of islanding, capacitor bank of wind turbine is switched and signs out from the system. Islanding is detected by measuring frequency and rms value of load voltage. The detection time of the proposed method is less than IEEE1547 standard. Time-domain simulations in MATLAB are used to verify the performance of the algorithm. The feasibility of the proposed method is also evaluated by an experimental system. The results show that the proposed islanding detection method successfully distinguishes between islanding phenomenon and other switching conditions.

Keywords: Distributed Generation, Islanding, Rate of Change of Output Power (ROCOAP) -Wind Turbine, Capacitor Bank Switching.

Reliability Assessment of Distribution System Considering Customer-Owned Distributed Generation
by S. M. Hashemi, A. Sadoughi

Vol. 6. n. 2, pp. 1000-1006

Abstract - By increasing the number of customer-owned DGs, which are normally fuel-based generators, reliability evaluation of distribution system face some problems; it is because of the fact that such systems are usually not controlled by network managers. In this paper an analytical technique is developed to consider the influence of customer-owned DGs on reliability evaluation. This method is based on estimating annual output power of DGs, load curve classification and probability evaluation of each section. This method needs less calculations and yields acceptable and accurate results, to the extent that its accuracy is comparable to that of Monte-Carlo Simulation (MCS).

Keywords: Customer-Owned Distributed Generation, Distribution System, Reliability Evaluation.

Optimal Placement of Distributed Generators and Reconfiguration of Distribution Systems for Loss Reduction using Genetic Algorithm
by Bahram Rashidi Jouybari, Mehdi Hosseini, Zaki Byagowi

Vol. 6. n. 2, pp. 1007-1012

Abstract - In this paper network reconfiguration and optimal placement of distributed generators (DGs) methods are used for minimizing of the total power losses in distribution systems. For this purpose, genetic algorithm (GA) optimization approach is proposed for the reconfiguration of distribution system and determination of optimum placement of DGs. The main innovation of this research paper is optimal placement of DGs for loss reduction and also using network reconfiguration in the system with DGs on the optimum locations for achieving more loss reduction. Comparative studies are conducted to investigate the impacts of optimal DGs placement and also using system reconfiguration in the system with DGs on the optimum locations compared to the system in the base case without using DGs and reconfiguration, system without using reconfiguration but with DG on the initial state, system only with DG on the initial state and finally, system without using reconfiguration but with DG on the optimum locations. Furthermore, the effects of DGs placement and network reconfiguration on voltage improvement are presented. The effectiveness of the proposed method is examined in the 33 bus distribution system. The results show that determination of optimum location of DGs in addition to reconfiguration method has a considerable effect on total loss reduction and voltage improvement.

Keywords: Network reconfiguration, Optimal placement, DGs, Loss reduction, Genetic algorithm.

Evaluation of the Electromagnetic Fields due to Lightning Channel with Respect to the Striking Angle
by M. Izadi, M. Z. A. Ab Kadir, C. Gomes, W. F. Wan Ahmad

Vol. 6. n. 2, pp.1013 -1023

Abstract - This paper reviews the different engineering return stroke current models and determines the current wave shape along the lightning channel. The general equations for electromagnetic fields due to vertical and slope lightning channel in the time domain are expressed using dipole method, extended Maxwell’s equations, FDTD and Gauss-Lobatto quadrature methods. In addition, effect of striking angle on the electromagnetic field values is also considered using a current sample from triggered lightning measurement. Results are then validated and compared with the measured values.

Keywords: Lightning Channel, Maxwell’s Equations, FDTD, Return Stroke Current .

Calculation of Low Frequency Electric Fields of Complex Power System Facilities
by Bojan Trkulja, Željko Štih, Tomislav Župan

Vol. 6. n. 2, pp. 1024-1029

Abstract - In this paper electric field of the large HV power system facility is calculated by the integral equations approach. System of equations is solved by the appliance of BEM and Galerkin methods. Non – flat ground is modelled with the surface elements. A comparison between thin-wire elements and surface elements is performed on cylindrical base of a busbar construction. A computer program for calculation of 3D low frequency electric fields is developed, based on described methods.

Keywords: Boundary Element Methods, Electric Fields, Galerkin Method, Integral Equations.

New Approach for Corona Loss Calculation Considering Ion Diffusion Variation Using FEM
by M. Mohammadi, R. Ebrahimi, M. Najafi

Vol. 6. n. 2, pp. 1030-1037

Abstract - TThis paper describes a new method of the corona loss in HVDC transmission lines using Finite Element Method (FEM).The present method implements the potentials and field at conductor surface as boundary conditions. In this paper the effect of ion diffusion coefficient is taken in account as function of electric field in calculation of power corona loss. In present method programming calls for only one loop and a new approach for updating of space charge densities around the conductor is implemented using Rung-Kutta integration method. The proposed method of solution has been applied for laboratory and full scale models of unipolar conductor to plane configuration .the calculated V-I characteristics and calculated electric field characteristics at ground plane agreed well with those calculated and measured before .fast convergence and reduction iteration numbers is characterized of the proposed method.

Keywords: Corona, Corona Power Loss, Ion Diffusion Coefficient, Finite Element Method(FEM) Engineering.

ANFIS Based Contamination Level Prediction of Porcelain Insulator Under Various Pollution Conditions
by K. Krishnamoorthi, S. Chandrasekar

Vol. 6. n. 2, pp. 1038-1045

Abstract - This paper deals with analysis of leakage current of porcelain insulator in order to develop a better diagnostic tool to identify the pollution severity of outdoor insulators. In this work laboratory based Pollution performance tests are carried out on porcelain insulator under AC voltage at different pollution levels and relative humidity conditions with sodium chloride as a contaminant. The pollution severity of outdoor insulators could be identified from the DWT STD-MRA (Standard Deviation Multi Resolution Analysis) Distortion Ratio pattern analysis of leakage current signals. Four parameters have been selected and used as the inputs for an Adaptive Neuro-Fuzzy Inference System(ANFIS) model, such as leakage current, distortion ratio, relative humidity and temperature. The model is appropriate to predict the equivalent salt deposit densities (ESDD) with an error difference of less than 0.0050mg/cm2 if the training data and the testing data are selected at the security stage. This reported result in the optimal prediction input parameters provide an invaluable tool for maintenance planning of a contamination flashover.

Keywords: Porcelain Insulators, Contamination Flashover, Leakage Currents, ANFIS Model, Prediction Characteristics, Contamination Prediction.

Finite Element Simulations of the Field Distribution for Artificially Aged Polymeric Insulators
by Aysel Ersoy, Ayten Kuntman

Vol. 6. n. 2, pp. 1046-1050

Abstract - In this study, a two dimensional finite element method (FEM) simulation is carried out for the calculation of the potential and the electrical fields through polymeric insulators. Prior to modeling, the samples are aged as indicated by the ASTM D2303 test standard. Different tracking patterns occurring after the aging test are used for modeling. The electrical field distribution on the polymeric sample surface is investigated in terms of the tracking behavior based on whether it is tracked or eroded. The theoretical results obtained from the FEM simulations suggest that the way that the liquid contaminant is used has a vital effect on the electric field distribution of the sample surface.

Keywords: Finite Element Method, Polymeric Insulators, Artificial Aging.

Comparison of Bayesian and Fuzzy ARTmap Networks in Transformers PD Localization
by Hamed Nafisi, Mehrdad Abedi, Gevorg B. Gharehpetian

Vol. 6. n. 2, pp. 1051-1059

Abstract - Insulation system of high voltage equipment has a vital role in apparatus lifetime and continuity of power supply. In power transformers one major source which can cause insulation failure is partial discharge (PD). PD localization has significant importance in the maintenance and repair of a transformer. In this paper two methods by use of neural networks for identifying partial discharge locations in transformer winding are proposed. Detailed model (DM) of transformer is developed for simulation and detection of PD. With modeling of partial discharge impulse source in EMTP software, this phenomenon is implemented in different points of transformer winding. Then produced currents in the both ends of winding are used for training and test of neural networks. In actual, obtained current signals contain noisy components. Thus in this paper the performance of the Fuzzy ARTmap neural network and Bayesian network for correct determination of partial discharge location in power transformer with considering different noises on simulated current signals for simulation of actual conditions is surveyed.

Keywords: Bayesian network, detailed model (DM), Fuzzy ARTmap (FAM) neural network, Partial discharge (PD), Power Transformer.