Latest issue

International Review of
Electrical Engineering
(IREE)
April 2013 (Vol. 8 N. 2)

Part A - Part B

Review of Multilevel Converters/Inverters

by Natin Janjamraj, Anant Oonsivilai

Vol. 8. n. 2, pp. 514-527

Abstract - Multilevel converters and inverters have become the enabling power conversion technology for high voltage high power applications in industries, power systems and energy conversions. Although the neutral-point clamped inverter was invented in 1979, the multilevel concept was not formally established until the early 1990s when diode-clamped multilevel inverter and the cascade multilevel inverter were proposed and entirely study. All these multilevel inverters have their voltage balancing problems and each of them has its own distinguished topology. A generalized multilevel inverter topology was proposed to overcome the voltage balancing problems and to reveal the commonality and connection of all multilevel converters/inverters structures. Recently, many novel topologies are proposed by deriving from generalized structure, such as zigzag multilevel inverter, modular multilevel converter (M2LC), marx multilevel inverter and etc. This paper presents a survey on novel topologies, controls and applications of multilevel converters and inverters.

Keywords: Multilevel Inverters, Topologies, Power Converters.

Optimized Harmonic for H-Bridges Connection Converters using Particle Swarm Optimization

by Anant Oonsivilai, Natin Janjamraj, Ratchadaporn Oonsivilai

Vol. 8. n. 2, pp. 528-538

Abstract - One of the major problems in multilevel voltage source inverter is the voltage total harmonic distortion (THDV). The number of output voltage level and switching angles are the most important for regarding performance indices. The H-bridge connection inverter with separated DC-link including DC-link voltages are identical is called cascade multilevel inverter. However, it is possible to have different values among the DC-link voltage of HBs, and it could be termed hybrid multilevel inverter (HMI), and thus increased number of output levels. Because of many number output levels of HMI, it had numerous unknown variables and it could eliminate several harmonics in addition. This paper present Particle Swarm Optimization (PSO) technique for solve switching angles and minimum THDV of three different H-bridge multilevel inverters including cascade multilevel inverter (CMI), binary hybrid multilevel inverter (BHMI) and ternary hybrid multilevel inverter (THMI) for THDV and number of switching devices comparison. The simulation results are illustrated in depth. Both advantages high level of inverter and Particle Swarm Optimization (PSO) applied as powerful tools for harmonic elimination.

Keywords: H-Bridge Multilevel Inverters, Particle swarms Optimization, Harmonic Elimination.

Sliding Mode Control of Energy Recovery Transformer-Less Power Accumulator Battery Pack Testing System

by Bo Long, Ji Hyoung Ryu, Young Won Jang, Kil To Chong

Vol. 8. n. 2, pp. 539-549

Abstract - The main objective of the present work is to apply sliding mode controller to medium voltage and high power output energy recovery power accumulator battery pack testing systems (ERPABPTS), which is composed of a three-level neutral point clamped three-phase voltage source inverter (NPC-VSI) and a non-isolating DC-DC converter. A decoupled scheme for the proposed system is put forward, based on that, two sliding mode plane for active and reactive current component control are illustrated. The ERPBPTS is used to integrate discharging energy to the power grid with high efficiency when performing current test, active and reactive power references for the grid-connected inverter are determined based on the discharging energy from the DC-DC converter. Without using the isolation transformer, the proposed scheme could greatly reduce the total volume of the system, offer less total harmonic distortion, and meanwhile maintain higher DC-link voltage utilization. The proposed method is implemented and verified both by simulation and experimental results on a laboratory hardware platform using 175kW IGBT-based ERPABTS using an embedded DSP controller.

Keywords: Energy Recovery Power Accumulator Battery Pack Testing System (ERPABPTS), Neutral Point Clamped-Voltage Source Inverter (NPC-VSI), Sliding Mode Control (SMC), Total Harmonic Distortion (THD).

Performance Evaluation of Real Time Implementation of New Hybrid PWM Strategies for Single Phase Seven Level Asymmetrical Inverter

by Johnson Uthayakumar R., Natarajan S. P., Anandhi T. S.

Vol. 8. n. 2, pp. 550-557

Abstract - Carrier Based Pulse Width Modulation (CBPWM) techniques have been used widely for switching of multilevel inverters due to simplicity and reduced computational requirements than the Space Vector Modulation (SVM). New hybrid carrier based PWM strategies have been implemented for a prototype of single phase seven level asymmetrical inverter in this work. Two inverter bridge circuits are used to achieve seven level output voltage. Phase Disposition (PD), Phase Opposition Disposition (POD), Alternate Phase Opposition Disposition (APOD) and Carrier Overlapping (CO) PWM strategies are used with triangular carriers above zero axis and rectified sine carriers below zero axis along with stepped reference. The triggering pulses are generated using the dSPACE dS1103/Real Time Interface (RTI) hardware and front end tool control desk with MATLAB-SIMULINK environment. The performance indices used are Total Harmonic Distortion (THD), Form factor (FF), Distortion Factor (DF), Root Mean Square (RMS) output voltage. It is observed that COPWM provides relatively better DC bus utilization and relatively lesser harmonic distortion for modulation index m_a=0.7-1.

Keywords: dSPACE, PD, POD, APOD, CO, THD, RMS, DC ,Stepped.

Passivity-Based Control Scheme for the Modular Multilevel Cascaded Converter (MMCC) as the HVDC-PLUS for Smart Grid Applications

by Yang Han

Vol. 8. n. 2, pp. 558-567

Abstract - This paper presents the passivity-based controller design methodologies of the 3-phase modular multilevel cascaded converter (MMCC) as HVDC-PLUS for smart grid applications. The mathematical model of the MMCC is derived in the terms of energy dissipation mechanism among the converter cells. The solvability and passivity analysis are presented based on the state-space averaged (SSA) models. The energy shaping (ES) problem is formulated by properly selection of the energy function. And the dissipative characteristics of the MMCC-based HVDC-PLUS is revealed. The interconnection and damping assignment (IDA) technique is proposed to reshape the trajectory of the control objective to guarantee the global convergence and accurate reference tracking. The carrier phase-shifted PWM scheme is adopted to synthesize the control signals for the individual half-bridge converters. The various simulation results under reactive and active power transmission scenarios are presented, which confirms the effectiveness of the proposed passivity-based control methodologies.

Keywords: Modular Multilevel Cascaded Converter (MMCC), State-Space Avaraging (SSA), Interconnection and Damping Assignment (IDA), Energy Shaping (ES), HVDC-PLUS, Smart Grid.

High Performance of Nonlinear Active Rectifier Voltage and Power Factor Control Using Feedback Linearization

by Saidah, M. Hery Purnomo, M. Ashari

Vol. 8. n. 2, pp. 568-574

Abstract - Nonlinear property of Active rectifier is caused by the use of the semiconductor switches, resulting in high harmonic distortion and high ripple output voltage on the DC side. This research develops a nonlinear controller to improve performance of the dc output voltage and line current based on feedback linearization. This controller mathematically transforms nonlinear system dynamics into fully linear ones, so that linear control techniques can be applied. It is designed with selecting energy function on DC side and quadrature-axis current on AC side as output variables, in order to avoid the internal dynamics, so that the system becomes stable and robust. The system applies switch function of time as the input of control strategy, instead of current and voltage in d-q frame. The proposal is validated through different tests. These tests include difference performance with conventional controller (PI optimized). The simulation results in that the output voltage performing without any overshoot, while the ripple and settling time is 0.006 sec, which is better result compared to PI optimized.

Keywords: Active Rectifier, Feedback Linearization, PI Optimized.

Synthesis of Active Damping for Grid-Connected Inverters with an LCL filter

by Huafeng Xiao, Shaojun Xie, Jinming Xu

Vol. 8. n. 2, pp. 575-584

Abstract - LCL filter characterized with high harmonic current attenuating and low bulk is preferable for medium and high power grid-connected inverters, but the resonance poles of filter endanger the safety of operation. Active damping (AD) is an effective measure to increase the system stability, but various AD structures were developed with no explanation as to how they were generated. The objective of this paper is to propose a general approach for developing AD technology of grid-connected inverter with LCL-filter. Firstly, the unified analytical model and systematical synthesis method for AD are proposed, the AD structures are listed based on single-state-variable single-compensator (SSVSC), and the effective AD structures are identified by root locus. Accordingly, a family of AD structures included some of the existing AD structures and a new one has been generated systematically. In order to verify the feasibility of the synthesis method, the properties of the deduced new AD structure are analyzed and compared with the existing AD structures by theoretic and simulation. Finally, a 3kw prototype is implemented and tested to show the effectiveness of the deduced AD structures by synthesis method. Furthermore, the AD structures are developed based on multi-state-variables multi-compensators (MSVMC) to deduce another family of AD structures, and an AD table is drew. One of the main contributions of this paper is that a clear picture is made on the systematical synthesis method to generate AD structures.

Keywords: Grid-connected inverter; LCL filter; Resonance; Active damping; Feedback.

A Novel Approach in Designing an Integrated Transformer LLC Resonant Converter

by A. Savu, A. Florescu, A. Radoi, M. Teodorescu

Vol. 8. n. 2, pp. 585-594

Abstract - This paper presents the design and analysis of a LLC resonant converter with an integrated transformer. The leakage inductance of the transformer participates in the resonance. No additional series resonant inductance is introduced. The novelty consists in designing the transformer around the value of the leakage inductance. A new method of obtaining a desired value of the leakage inductance is explained. Theory is validated by simulation and experimental results, which are in good agreement.

Keywords: LLC Converter, Leakage Inductance, Integrated Transformer, Electric Resonance.

Current Estimation for Pulsed Power Applications

by E. Penovi, R. Garcia Retegui, S. Maestri, W. Kloster, M. Benedetti

Vol. 8. n. 2, pp. 595-602

Abstract - This paper presents a current sensing method to estimate the load current in pulsed current applications using a current transformer. The droop effect generated by this kind of sensor when measuring dc currents is compensated by means of signal processing techniques. The method is based on the inclusion of a sensor model in the system model so as to obtain an extended state-space model enabling to estimate the load current. A Kalman observer is employed in order to obtain an estimation with high noise rejection. The implementation of the observer in an FPGA platform allows the incorporation of this block as a stage independent of the converter control. Experimental results validate the implementation of the proposed system.

Keywords: Pulsed Power Converter, Current Measurement, FPGA.

Design, Analysis and Experimental Verification of an Efficient 2 kW Permanent Magnet Synchronous Generator for WPAs

by D. Uygun, C. Ocak, E. Buyukbicakci

Vol. 8. n. 2, pp. 603-607

Abstract - This paper presents the design procedure, analysis and experimental verification of a 2 kW in-runner permanent magnet synchronous generator (PMSG) with radial magnetic flux for wind power applications (WPAs). The generator is designed via developed CAD-procedure and design interface in which the basic parameters of the generators are calculated respectively. Subsequently, the effectiveness of the interface is supported by applying a coupled transient electromagnetic procedure using finite element method and the design and simulation principles presented apply primarily to the prototype model. Moreover, the test results of the prototype permanent-magnet generator are analyzed and compared with the calculated data and characteristics. The purposed model is particularly well suited for low-speed WPAs with a very low cogging torque.

Keywords: CAD-Procedure, Prototype PMSG, Coupled Electromagnetic Procedure, Low-Cogging Torque.

Research Into Unbalanced Electromagnetic Force Resulting from Rotor Winding-Related Short Circuit of Turbine Generator

by Wu Yucai, Zhao Qian, Li Yonggang, Li Heming, Zhang Wenjing

Vol. 8. n. 2, pp. 608-615

Abstract - Unbalanced electromagnetic force is the associated stress of the inter-turn short circuit fault of the rotor winding of a turbine generator. This paper simultaneously uses analytic and numerical methods to calculate the unbalanced electromagnetic force of a rotor and analyze the relationship between the unbalanced electromagnetic force and generator running status. The comparative analysis shows that under either no-load or loading conditions, the electromagnetic force calculated by the analytical method has a greater deviation. Taking into consideration the influence of core saturation, magnetic field skewing, higher harmonics, structure and other factors, the numerical method has more accurate and reliable calculation results. When a power generator emits its constant active power, its unbalanced electromagnetic force does not always increase with its increasing excitation current, so the rotor vibration discrimination method based on the rotor winding-related inter-turn short circuit for excitation current regulation is effective only within a certain range, and a no-load test is more suitable for the rapid diagnosis of an inter-turn short circuit fault of a rotor winding.

Keywords: Inter-Turn Short Circuit of Rotor Winding, Running State, Finite Element, Unbalanced Electromagnetic Force.

Monitoring Gear Fault by Using Motor Current Signature Analysis and Fast Kurtogram Method

by Chemseddine Rahmoune, Djamel Benazzouz

Vol. 8. n. 2, pp. 616-625

Abstract - Conventional methods (i.e. time and frequency analysis) can routinely be used to reveal gear fault-indicating information in the current signal. In recent years, Wavelet analysis, which can lead to a clear identification of the nature of faults, are widely used to describe rotating machine condition. The Capability of this method in the detection of any abnormality can be further improved when its low-order frequency moments are considered. This paper presents the use of the Fast Kurtogram in the early detection and condition monitoring of crack fault. For this purpose, a dynamic model of an electromechanical system which is a simple stage gearbox (with and without gear defect) driven by a three phase induction machine is developed. Then motor stator current is analyzed by using a Fast Kurtogram method. This method is suitable for such diagnosis and gives valuable information about the presence and effects of the crack tooth defect.

Keywords: Fast-Kurtogram, Gearbox, Induction Machine, MCSA, Monitoring, Tooth Crack.

LQR Control of Permanent Magnet Synchronous Motor Based on Exact State Feedback Linearization

by Gang Liu, Cong Zhang

Vol. 8. n. 2, pp. 626-632

Abstract - Permanent magnet synchronous motor (PMSM) is a typical nonlinear system with significant coupling. This paper proposes a linear quadratic regulator (LQR) to control the PMSM with exact state feedback linearization. Based on the mathematical model of PMSM, the corresponding affine nonlinear system is constructed and the exact linearization conditions are discussed using differential geometry theory. Applying appropriate coordinate transformation and state feedback transformation, the affine nonlinear model is linearized into a linear system. Then, an optimal controller is designed to control the decoupled linear plant with LQR. Simulations and experiments are performed to verify the effectiveness of the proposed control strategy. The results demonstrate the feasibility of the differential geometry method and reveal the high performance and advantages of the proposed nonlinear controller in dynamic response and steady-stage error regulating characteristics.

Keywords: Permanent Magnet Synchronous Motor (PMSM), Linear Quadratic Regulator (LQR), State Feedback Linearization, Affine Nonlinear System, Differential Geometry Theory.

A Novel and Low Cost Sensorless Controller for SRM Utilizing Linear Equations: Analysis, Design and Construction

by M. Rafiee, E. Afjei, A. Siadatan

Vol. 8. n. 2, pp. 633-643

Abstract - A new low cost sensorless controller for Switched Reluctance Motor (SRM) is designed and constructed in this paper. In the presented novel technique, the rotor position is obtained from the linear equations of the SRM phase current, flux and rotor position. In other similar strategies, the detection of rotor position requires an expensive, high speed controller component since a complex process and calculations have to be performed. Because of using linear equations in the presented technique, the program used by of the controller is less complex and simpler which causes a low cost, medium frequency controller can drive the SRM easily. A new configuration of MOSFET driving is also introduced in this paper which solves a typical problem of usual converters. In this paper, one phase mathematical model of SRM is explained at the beginning. Then 50 watts 12 by 8 SRM is selected and analyzed by Finite Element Method (FEM) in order to obtain the necessary motor parameters. After that the novel sensorless technique is introduced and designed for the motor. The controller circuit is then constructed and tested in the laboratory. Finally operational results are presented for the motor and controller circuit under different load conditions.

Keywords: Linear Equations, Sensorless, SRM, FEM.

A New Direct Torque Control Algorithm For Torque And Flux Ripple Reduction

by Yavuz User, Kayhan Gulez

Vol. 8. n. 2, pp. 644-653

Abstract - In this study, a novel direct torque control (DTC) algorithm is developed to decrease torque ripple, electromagnetic noise and harmonics in the three phase squirrel caged induction motors. The space vectors of the conventional DTC method, the position of the stator flux vector and deviation from the reference flux are utilized to construct the new algorithm. Switching time of the vectors in the proposed algorithm is determined from a switching table which is based on the flux error. Switching time pairs in the table are selected using the flux error and the position of the sector. This table eliminates need for complex mathematical operations to determine the switching time of the space vectors in the induction motors and maximizes the performance of the algorithm. The algorithm is simulated and tested by an experimental setup. Simulation and experimental results suggest that the proposed algorithm decreases torque ripple and current harmonic and it has adequate dynamic and steady-state torque performance. Compared to the conventional DTC, the new algorithm has lower EMI noise level.

Keywords: Induction Motor, Direct Torque Control, Control Technology, Torque and Flux Linkage ripple.

The Voltage Control for PMSM Direct-Driven PMSG/Battery Renewable Energy System Using Modified Elman Neural Network

by Chih-Hong Lin

Vol. 8. n. 2, pp. 654-663

Abstract - The modified Elman neural network (NN) controller to be used for the voltage control of the permanent magnet (PM) synchronous generator/battery renewable energy system is proposed to improve control performance of voltage adjustment. Because the PM synchronous generator/battery renewable energy system is a nonlinear time-varying system, three sets on-line trained modified Elman NN controllers are developed for the voltage tracking controllers of DC bus voltage of rectifier, AC voltage of inverter and DC voltage of battery storage system through boost/buck converter in order to improve output performance. Finally, experimental results are verified to show the effectiveness of the proposed control scheme.

Keywords: Permanent Magnet Synchronous Generator, Rectifier, Inverter, Elman Neural Network, Battery Renewable Energy System.

An Intelligent Diagnostic Condition Monitoring System for AC Motors via Instantaneous Power Analysis

by Muhammad Irfan, Nordin Saad, Rosdiazli Ibrahim, Vijanth S. Asirvadam

Vol. 8. n. 2, pp. 664-672

Abstract - A novel intelligent diagnostic condition monitoring system for electric motors via instantaneous power analysis is proposed. Although several types of condition monitoring and fault diagnosis techniques are available, however they have limitations in terms of the hardware costs and installation of the sensors for data acquisition. The proposed sensor-less condition monitoring system will allow real-time continuous tracking of various defects and will determine the severity of the defects to provide automatic decision making. To illustrate the viability of the approach, experiments were carried out on two different defect levels of the motor bearings. It is anticipated that the proposed motor protection system will be quicker, more efficient and more user friendly than the existing methods.

Keywords: Condition Monitoring, Induction Motor, Intelligent Diagnostic, Programmable Logic Controllers, Labview, Signal Processing, Preventive Maintenance.

Implementation of DTFC Strategy Using Speed Sliding Mode Control for Induction Motor Drive

by A. Abbou, Y. Sayouti, H. Mahmoudi, M. Akherraz

Vol. 8. n. 2, pp. 673-680

Abstract - In This paper a dSPACE implementation of three phase squirrel-cage induction motor control using Direct Torque and Flux Control (DTFC) technique with speed sliding mode controller is presented. The sliding mode control technique utilizes a robust control law to model uncertain and disturbances while the system in sliding mode. The classical lookup table is replaced by a neural network selector providing switching state to the inverter. The rotor speed is estimated by a simple open loop estimator. A DSP experimental using TMS320F240 results are shown in this paper.

Keywords: dSPACE, DTFC, Sliding Control, Sensorless, Neural Network, Induction Motor (IM).

Modal Analysis of Stator System of Large Turbo-Generator

by Yixuan Wang, Ying Wang

Vol. 8. n. 2, pp. 681-689

Abstract - The stator core is an important part of large turbo-generator .The natural frequency of the stator core must be to avoid the operating frequency and the double frequency. In this paper, 1000MW generator stator core structure is considered as the research object. In the Pro / E software, a virtual manufacturing model is built for design and manufacture of stator core; In ANSYS software, a parametric finite element model of the stator core is built for virtual experimental modal analysis; The virtual prototype model of the stator core in the different constraints (free, and different constraints) and different core parameters (such as the core inner and outer diameter, length) is used to analyze and solve the natural frequencies and mode shape changes. For design, manufacturing and on-line monitoring and fault diagnosis of a variety of large-capacity turbine generator, the research approach and results provide an important basis.

Keywords: Large turbo-Generator, Stator Core, Virtual Prototype, Modal Analysis.

Force and Torque Modeling for Linear Actuator Under State of Large Yaw Angle

by Gan Zhou, Liping Zhan, Shihai Yang

Vol. 8. n. 2, pp. 690-695

Abstract - The planar motor prototype is driven by four permanent-magnet ironless linear actuators. In order to achieve its positioning control under the large yaw angle, this paper proposed a novel dual-parameter half-analytical model for the linear actuator. Firstly, using numerical Lorentz force method, the fast simulation method of the linear actuator is established. Secondly, using spectrum analysis and curve fitting methods, the dual-parameter expressions of the force and torque are deduced in detail. Lastly, a new decoupling control strategy is proposed based on the dual-parameter model. The errors of this modeling method are evaluated with the 3-D finite-element method. The same approach can be applied to similar types of planar motors with the structure of symmetrical three-phase windings.

Keywords: Force and Torque, Linear Actuator, Modeling, Yaw Angle.

High Performance Direct Torque and Flux Control of Induction Motor Drive using Fuzzy Logic Based Speed Controller

by Tejavathu Ramesh, A. K. Panda

Vol. 8. n. 2, pp. 696-710

Abstract - In this research study, direct torque and flux control of induction motor drive (IMD) using fuzzy logic based speed controller (FLSC) is implemented to minimize the ripple contents of stator current, flux and torque and also improve the speed responses under transient and steady state operating conditions. It is quite difficult to optimize the high performance of an IMD using conventional PI- speed controller (PISC), because of the nonlinear model of induction motor drive. The conventional PI-controller requires accurate and continuous tuning of gain values. Therefore, the FLC technique is implemented to improve the system performance. The detailed simulation results are presented in forward and reversal motoring under 1200 rpm and 900 rpm with no-load, load, sudden change in speed and sudden zero speed operating conditions using MATLAB/Simulink software to support the feasibility of the control strategy. To validate the FLSC control approach, the system is also implemented on real-time system and adequate results are reported for its validation.

Keywords: Direct torque control (DTC), Fuzzy logic speed control (FLSC), Induction motor drive (IMD), PI-speed controller (PISC).

Torque Ripple Reduction Analysis and Dynamic Performance Improvement of PMSM Drives Based on Direct Torque Control Strategy

by Selin Ozcira, Nur Bekiroglu, Ibrahim Senol

Vol. 8. n. 2, pp. 711-716

Abstract - This paper examines the torque ripple reduction based on direct torque control (DTC) for permanent magnet synchronous motors (PMSM). The proposed DTC method includes reference flux vector calculator and torque estimator introducing space vector pulse-width modulation (SVPWM) method. Since the constant switching frequency is produced by SVM technique, the SVPWM method enables the drive to produce voltage vector of any direction and magnitude thus, torque ripple is eliminated compared with classical hysteresis DTC. A digital signal processor (DSP) is used for PMSM drive system. The effectiveness of the proposed method is verified by both simulation and experimental results. Experimental results obtained by a motor & generator setup are shown to verify the operating performance. The experimental setup exhibits validity of the analysis and demonstrates good dynamic response by reducing torque ripples.

Keywords: Torque Ripple Reduction, Permanent Magnet Synchronous Motor, Direct Torque Control, Space Vector Pulse-Width Modulation.

An Effective Method for Optimal Design of Electric Machines Based on Finite Element Analysis

by Zhao Haisen, Liu Xiaofang, Peter Baldassari

Vol. 8. n. 2, pp. 717-721

Abstract - This paper presents an effective method for optimal design of electric machines. In this method, three numerical techniques are employed to save computational time related to the time-stepping finite element method (T-S FEM). The first technique involves using the field-circuit coupling steady state FEM to calculate initial values for the time-stepping finite element analysis. The steady state method uses a simpler, faster model to estimate the initial values reasonably close to the actual ones. The second technique is an adaptive meshing adjustment for minor shape modifications in which minor geometric changes can be made without re-meshing. The third technique involves using state variables from the previous design iteration as the initial conditions for the next iteration. Together these three techniques can reduce the total simulation time required to optimally design an electric machine. An example 5.5kW induction motor is discussed and the results demonstrate a significant reduction in simulation time.

Keywords: Electric Machines, Finite Element Analysis (FEA), Losses, Optimal Design, Stator Slot.

Damage Analysis of Lithium Iron Phosphate Batteries for Pure Electric Vehicles

by Yinquan Hu, Heping Liu

Vol. 8. n. 2, pp. 722-728

Abstract - Charge and discharge experiments of Lithium iron phosphate (LiFePO₄) battery packs have been performed on an experimental platform, and electrochemical properties and the damage mechanism of LiFePO₄ batteries are also analyzed in extreme cases. Our results indicate that over-charge has little impact on utilizable capacity of the battery in the short term. Over-discharge has a huge impact on utilizable capacity of the battery. Based on these results, a battery pack management method for reducing battery damage is proposed. Namely, by detecting voltage, temperature and other parameters of each cell, charge and discharge processes of the battery pack are monitored and controlled. This management method can avoid the battery pack damage problems arising from over-charge, over-discharge and over-temperature. At the same time, this method can also slow the rate of the battery pack capacity attenuation and extend the cycle life of the battery pack.

Keywords: Electrochemical Properties, Over-Charge, Over-Discharge, Series Charge, State of Charge.

Part A - Part B

Load Leveling with Electrical Storage Systems: a Two-Step Optimization Procedure

by G. Carpinelli, S. Khormali, F. Mottola, D. Proto

Vol. 8. n. 2, pp. 729-736

Abstract - In this paper an optimal storage-system control strategy is proposed aimed at leveling the active power requested by the loads connected to a distribution substation. The control strategy is based on a two-step procedure: first, a day-ahead scheduling is effected, and then a very short time predictive control is performed. For both the procedures, optimization models were formulated and solved including technical constraints that guarantee adequate storage-system lifetime (e.g., depth of discharge and maximum number of charge/discharge cycles). A numerical application demonstrates the effectiveness and advantages of the proposed procedure.

Keywords: Energy Storage Systems, Power System, Optimal Strategies and Load Leveling.

The Burr XII Model and its Bayes Estimation for Wind Power Production Assessment

by E. Chiodo

Vol. 8. n. 2, pp. 737-751

Abstract - The probabilistic Burr XII model for the characterization and estimation of the wind-speed distribution is analyzed in the paper, in view of wind power production evaluation. Most of the existing methods for such evaluation are based upon the popular Weibull distribution for wind speed statistics. However, recent studies have pointed out some inadequacies in the Weibull distribution. The analysis of many field data show indeed significant “heavy tails” in the probability distribution of wind speed for large values of speed. This constitutes a critical aspect when the Weibull model is adopted, not only for its consequences on wind speed estimation, but especially on wind power estimation. The Burr model is here justified on theoretical grounds, being based on a proper "mixture" of Weibull probability distributions. After illustrating such derivation, a suitable Bayes approach for the estimation of the Burr model is proposed. The method is based upon the Negative Log-Gamma distribution for the assessment of prior information in a novel way which should be easily feasible for the system engineer. The method appears indeed to be very practical, since it only requires some prior information on the probability distribution of the wind speed. The results of a large set of numerical simulation are reported to illustrate the simplicity and efficiency of the proposed method.

Keywords: Bayes Estimation, Burr Distribution, Negative Log-Gamma Distribution, Renewable Energy, Weibull Distribution, Wind Power.

Transient Stability Margins Evaluation Based Upon Probabilistic Approach

by E. Chiodo, D. Lauria, C. Pisani, D. Villacci

Vol. 8. n. 2, pp. 752-761

Abstract - Transient stability is recognized as a crucial aspect both in planning and operating conditions and it constitutes one of the most crucial challenges to address for the designers and for operators. Furthermore, the recent evolution of the methodologies employed in this context allows to treat in a more systematic manner some aspects related to the inherent randomness of the problem. In light of this considerations, the paper proposes a new probabilistic approach for deriving the stability margins of an electrical power system, taking into account the stochastic nature of the main problem randomness: the fault clearing time, the reclosing time and the fault type and location. Differently from previous works, the probabilistic approach properly considers also the friction forces which make more difficult the mathematical formulation of the problem. In order to give a measure of the system exploitation with respect its own transient stability, a probabilistic stability index has been adopted in the work. In the last part of the paper, a numerical application is presented in order to show the feasibility and the effectiveness of the proposed methodology.

Keywords: Transient Stability, Transient Stability Margins, Probability, Exploitation.

Prediction of Fault Location in Overhead Transmission Line and Underground Distribution Cable Using Probabilistic Neural Network

by P. Chiradeja, A. Ngaopitakkul

Vol. 8. n. 2, pp. 762-768

Abstract - This paper proposes an algorithm based on a combination of discrete wavelet transform (DWT) and probabilistic neural network (PNN) for locating fault on transmission and distribution system. Simulations and the training process for the PNN are performed using Electromagnetic Transients Program (EMTP) and MATLAB. The mother wavelet daubechies4 (db4) is employed to decompose high frequency component from fault signals. The first peak time in first scale of each bus, that can detect fault, is used as input pattern for the training pattern. Various cases studies based on Thailand electricity transmission and distribution systems have been investigated so that the algorithm can be implemented. The results show that the proposed algorithm is capable of performing the fault location with satisfactory accuracy.

Keywords: Wavelet Transform, Fault Location, Transmission and Distribution, Probabilistic Neural Network.

Cost / Loss Minimization by the Placement of DG in Distribution System Using GA and PSO – a Comparative Analysis

by D. Sattianadan, M. Sudhakaran, S. S. Dash, K. Vijayakumar

Vol. 8. n. 2, pp. 769-775

Abstract - The development of Distributed Generation (DG) has been paying more attention in recent years in the field of distribution systems. The primary objective of DG is to reduce the power losses in the distribution system by proper location and sizing of it. But to reduce the power losses, large size of DG has to be installed which in turn increases the cost of installation of DG. To overcome the above mentioned issue, in this paper the cost and loss are minimized simultaneously by placing the DG in the distribution system. This paper consists of two phases, phase-1 reveals the location of DG with the help of Voltage Stability Index (VSI) and size of DG is found by trail and error method and Phase-2 deals with the optimal location and size of DG by Genetic Algorithm (GA) and the results are compared with the Particle Swarm Optimization(PSO) Technique. A simulation study has been performed on a 33 and 69 bus Radial Distribution System for various load modeling.

Keywords: Distributed Generation, Genetic Algorithm, Particle Swarm Optimization, Voltage Stability Index, Load Modelling .

Classification of Power Quality Disturbances Using Support Vector Machines and Comparing Classification Performance

by Ç. Arıkan, M. Özdemir

Vol. 8. n. 2, pp. 776-784

Abstract - In this study pure sine and five kinds of power quality disturbances (PQD) such as voltage swell, voltage sag, voltage with harmonics, transients and flicker are classified by using wavelet based support vector machines (SVM). The performance of proposed method is evaluated by using real time and synthetic data based on mathematical model. Real time data is obtained from national energy system of Turkey. Synthetic data is acquired by using MATLAB. Additionally performance of SVM is compared with artificial neural network (ANN) and Bayes classifier for same future vector and data. Multi-resolution analysis (MRA) technique of discrete wavelet technique (DWT) and Parseval’s theorem are employed to extract the energy distribution features of signals consisting of PQD. When classification performance of SVM is compared with ANN and Bayes classifier, it’s seen that SVM gives the best result both real time and synthetic data.

Keywords: Artificial Neural Network, Bayes Classifier, Discrete Wavelet Transform, Flicker, Power Quality, Support Vector Machine, Transients, Voltage Sag, Voltage Swell, Voltage with Harmonics.

A New Approach to Fault Location in the Random Disturbance of Wind Power

by Yagang Zhang, Zheng Zhao, Yi Sun, Zengping Wang

Vol. 8. n. 2, pp. 785-791

Abstract - The development and utilization of renewable energy resources is the future development direction. Wide area backup protection needs to locate fault element and fault section before backup protection action, and prepare for modifying fixed value of backup protection. The researches in this paper are mainly serving wide area adaptive backup protection system. Considering the development of new energy resources power system, especially the random disturbances of wind power, based on Bayes posterior decision principle, we will explore a new fault location technology. According to different types of faults, extensive simulation experiments have amply demonstrated the reliability of this fault location technology.

Keywords: Fault Location, Wind Power, Random Disturbance, Posterior Decision, Weibull Distribution, Wide Area Backup Protection.

Robust Shunt FACTS Controller Design for Power System Damping Improvement

by G. Y. Rajaa Vikhram, S. Latha

Vol. 8. n. 2, pp. 792-801

Abstract - This paper presents a design of robust PID controller structure for shunt FACTS controllers namely STATCOM and SVC. Robust STATCOM and SVC is designed using H-infinity loop-shaping technique. The performance of the controller is tested in single machine infinite bus power system to damp out the oscillations. The variation of transmission line reactances is considered as multiplicative uncertainty and the design is carried out by applying robustness criteria to improve both stability and performance. The performance of robust controller is compared with conventional PID controller in damping out the oscillations. It has been observed that the conventional PID controller is ineffective at operating points other than nominal. The robust design provides an extremely good damping characteristic over a range of operating conditions and it is evaluated based on the time domain specifications.

Keywords: STATCOM, SVC, Shunt-Connected FACTS, Damping Control, Robust Control, Loop Shaping Technique.

A Hybrid Islanding Detection Method for Grid-Connected Renewable Generation System

by Wen-Yeau Chang

Vol. 8. n. 2, pp. 802-809

Abstract - This study proposes a hybrid islanding detection method for use by the grid-connected inverter of a distributed renewable power generation system (RPGS). The proposed hybrid islanding detection method combines active technique and passive technique. The proposed active islanding detection technique is the correlation factor islanding detection method. The proposed passive technique involves two indices: the rate of change of voltage (ROCOV) and the rate of change of frequency (ROCOF). In this study, experiments are conducted to illustrate the principles of the proposed techniques for a prototype grid-connected inverter of a RPGS. The test results show that the newly proposed method is reliable, economical, and easy to implement for islanding detection of grid-connected inverter.

Keywords: Islanding Detection, Grid-Connected Inverter, Renewable Power Generation System, Active Islanding Technique, Passive Islanding Technique.

On the Profitability of Load Dispatch in Power Systems

by John G. Vlachogiannis

Vol. 8. n. 2, pp. 810-819

Abstract - The state-of-the-art research on load dispatch in power systems proposes as best applicable strategy either economic load dispatch (ELD) or combined economic emission dispatch (CEED). The economic emission dispatching (EED) option is an alternative. In this paper, the raised query of which load dispatch in a power system is actually profitable with respect to economy of the country or region of power system is clearly answered. A benchmark is developed based on the environmental Kuznets curve (EKC) and an improved coordinated aggregation-based particle swarm optimization (ICA-PSO) algorithm. The ICA-PSO is implemented for optimal ELD and EED solutions on Crete’s island in Greece and Hellenic bulk power systems. The obtained ELD and EED compete on EKC-based benchmark. In addition, deterministic and stochastic load dispatch obtained by other optimization techniques on Midwestern USA, Taipower, 40-generator and IEEE 30-bus power system compete on developed benchmark. The competition yields subversive conclusions for load dispatch strategies in power systems from country to country. The paper provides a novel closed-formula indicating which load dispatch strategy is profitable for the economy of the country where a power system is located.

Keywords: Carbon Dioxide Emissions, Economic Growth, Energy Policy, Environmental Kuznets Curve, Optimal Load Dispatch, Particle Swarm Optimization, Power System.

Petri Nets Fault Diagnosis System for a Large Power Station and its Transmission Lines

by M. M. Mansour, Mohamed A. A. Wahab , Wael M. Soliman

Vol. 8. n. 2, pp. 820-831

Abstract - In order to assist and support the operation engineers in control center of a large power station to make rapid and reasonable decision in the critical situations. This paper proposes a fault diagnosis system based on Petri nets to estimate the faulty item/section(s) of that large power generation station and its transmission lines with solving the excess information which received in control center. The proposed methodology utilizes the final information of protective relays and corresponding circuit breakers to build a fault diagnosis model based on Petri net for each item/section(s). It can diagnose and estimate the faulty item/section(s) correctly for multiple faults as well as simple faults. Moreover, it examines the misoperation of circuit breaker based on the relays information and then determines the faulty item/section(s). In order to testify the validity and feasibility of the method, a computer simulation of High Dam power generation station and its 500 kV double-circuit transmission lines is used. It is shown from two study cases that the Petri nets fault diagnosis method has many merits such as: accurate fault diagnosis results, rapid reasoning, less storage memory, easy and flexible correctness of Petri nets fault diagnosis models for each item/section(s). Moreover, it can be applied into a large power generation station and its transmission lines for real time fault diagnosis.

Keywords: Petri Nets, Fault Diagnosis, Power Station, Transmission Lines.

Advancements in PV Plant Energy Production Prediction with Model Improvement Based on Measured Data

by Igor Petrović, Zdenko Šimić, Mario Vražić

Vol. 8. n. 2, pp. 832-838

Abstract - The object of this research is to implement modifications into conventional analytical model for calculating energy production from a PV plant. Improvements are introduced through equipment work characteristics and Liu-Jordan-Klein model modifications used in conventional analytical model predictions for the PV plant in Varaždin, Croatia. A two-year measured energy production data is available and is stored into a database. The original conventional analytical model selected for this research is presented with the Homer software tool. The improvements are based on one year period measured data to get more accurate results on hourly basis, and therefore ensure better results for monthly and annual values. The second year period measured data is used to verify the introduced modifications. It can be expected that verification of the model will generate more inaccurate results, especially in transition periods. If model output results for the second year are more accurate than the original conventional model, it can be concluded that the improvements are rather correct. It is estimated that at least 5 years of measuring process are needed in order to generate the best set of correction factors. Methods for implementation of improvements are now developed for the available data and results, and are presented in this paper.

Keywords: : PV Plant, Conventional Analytical Model, Measured Energy Production, Modelling Improvements.

Accurate Unbalanced Fault Location Method for Multi-Ended Multi-Tapped Structures

by M. Rezaei Jegarluei, N. Moaddabi, G. B. Gharehpetian, M. Mohammadalizadeh Shabestary

Vol. 8. n. 2, pp. 839-848

Abstract - The accurate fault location is an important criterion for protection system. Accurate and fast fault location decreases the outage time, consumers dissatisfaction and operation cost. Different methods have been proposed to determine the fault location. The impedance-based methods are usually used to protect power systems. The accuracy of these methods depends on system parameters and the structure of power systems. Also, these methods require an iterative process, the phase alignment and a high volume of data. Another algorithm has been newly presented based on negative sequence parameters, which is not iterative and the amount of data communicated between relays is small. Besides, this algorithm is not affected by pre-fault load flow, zero-sequence mutual coupling and fault resistance. This algorithm has been applied for one-tapped systems. But, that method is not applicable for multi-ended structures with more than one tap. In this paper, a new algorithm is introduced to extend the negative sequence method for multi-ended structures with more than one tap. This new algorithm covers a larger area of the power system. Hence, it improves the reliability of power systems. It decreases the amount of relays necessary for the fault location. So, it can noticeably reduce the costs. Also, in this paper, a new idea is presented to reduce the time of the fault location process. The proposed methods are implemented in PSCAD/EMTDC and MATLAB software. The results of simulations will show the effectiveness and accuracy of proposed methods.

Keywords: Power System Protection, Unbalanced Short Circuit, Fault Location, Negative Sequence.

Medium Voltage Quality Series Injection DVR with MMC base on Stand-Alone Photovoltaic Application for ADS

by Narin Watanakul, Singthong Pattanasethanon

Vol. 8. n. 2, pp. 849-857

Abstract - This article applies the photovoltaic PV cell system. The effect is compensated and protected sensitive equipment against balance/unbalance medium voltage Sags, through series injection of the dynamic voltage restore (DVR). The multilevel modular converter (MMC) with the phase shift PWM algorithm for 9-level cascaded H-bridge (CHB) inverter. The power IGBT modular selection type double leg unit of the series connection with the separated dc sources PV arrays. The modeling Inphase compensated type of controller DVR, the controller designed to have reference voltage supply 0.5 pu and injected voltage 0.5 pu. The PV cell system with the type of amorphous. The result of the controlling system contains medium voltage Sags for distribution automation system (ADS) load rating of 25 kVA. Simulation is also conducted paralleled along with measurements of the prototype. As a result short duration of medium voltage, which is used to test the cause of electric fault current. This provides guideline to further analyze and improve voltage quality in electrical system pertinent to stand-alone photovoltaic system. The configuration is suitable for PV application as the PV strings operate independently and later expansion is possible, PV gird connection has been widely installed.

Keywords: Power Quality, Dynamic Voltage Restorer (DVR), PV Stand-alone, Medium Voltage Sags, Multilevel Modular Converter(MMC), Cascaded H-Bridge (CHB), Distribution Automation System (DAS).

Co-ordinated Design of PSS with Multiple FACTS Controllers in Multi-machine Power System using Advanced Adaptive PSO

by Rajendraprasad Narne, Prafulla Chandra Panda

Vol. 8. n. 2, pp. 858-866

Abstract - This study presents coordinated control tuning of power system stabilizer (PSS) with thyristor controlled series capacitor (TCSC) and static var compensator (SVC) for multi-machine power system. The design of proposed coordinated damping controller is formulated as an optimization problem and the controller gains are optimized instantaneously using advanced adaptive particle swarm optimization (AAPSO). Here the multi-machine power system employed with PSS, TCSC and SVC is considered for analysis. The coordinated tuning among the damping controllers is performed on the non-linear power system dynamic model. Finally, the proposed coordinated controller performance is discussed with time domain simulations. Different loading conditions are employed on the test system to test the robustness of proposed coordinate controller and the simulation results are compared with four different control schemes.

Keywords: Coordination, Power System Stabilizer, Particle Swarm Optimization, Static Var Compensator, Thyristor Controlled Series Capacitor.

Design of High Speed Adaptive Load Shedding for Industrial Cogeneration System

by Mukesh Kumar Kirar, Ganga Agnihotri

Vol. 8. n. 2, pp. 867-874

Abstract - This paper presents transient stability analysis and enhancement of Industrial Cogeneration Plant (ICP) interconnected with Public Power Company (PPC) for quality and reliability of power supply. If difference between In-plant generation and demand in islanded system is large, the speed and accuracy of load shedding is extremely important to achieve stable operation. This paper presents prompt load shedding technique for ICP in which load-generation difference is huge. In this paper load shedding scheme is configured in to three stages, User defined Knowledge base (UDKB) generation, Artificial Neural Network configuration, and online implementation. The purpose of the proposed scheme is to accomplish high speed and adaptive load shedding by real-time measurement and UDKB. By selecting the total power import, total in-plant generation, spinning reserve, total demand and frequency decay rate as the input neurons of the ANN, the minimum amount of load shedding is determined to maintain the stability of islanded systems. Transient stability analysis has been performed with the help of ETAP software, to prepare the training data set for ANN, by considering all possible contingency and combination of generation and load scenarios which affect system stability. Artificial Neural Network (ANN) has been implemented on MATLAB.

Keywords: Artificial Neural Network, Islanded System, Load Shedding, Electrical Transient Analyser Program (ETAP), Supervisory Control and Data Acquisition .

Junction Temperature-Forward Voltage Characterization of LEDs Based Accelerated Degradation Test

by Xingming Long, Ruijin Liao, Jin Zhou, Jinshe Yuan, Liang Fang

Vol. 8. n. 2, pp. 875-878

Abstract - The experimental junction temperature-forward voltage characterization of ageing white light-emitting diodes (LEDs) based 460nm-GaN with different package materials is presented. The junction temperature stepping into the nonlinear region of temperature junction-forward voltage moves towards lower point (130°C). The fitted linear temperature coefficient (K) holds constant for about 336 hours burn-in period in our accelerated degradation testing (ADT), after the period, the increase of K in magnitude larger than the theoretical result (−1.76 mV/ °C) is demonstrated, and then the differences among LEDs types are also compared. A modified theoretical result resolving ageing information is explained.

Keywords: White Light-Emitting Diode, Accelerated Degradation, Temperature Coefficient, Dynamic Change.

Design of Digital IIR Filter with Conflicting Objectives

by Ranjit Kaur, Manjeet Singh Patterh, J. S. Dhillon

Vol. 8. n. 2, pp. 879-890

Abstract - Infinite impulse response (IIR) filter design is a highly constrained multiobjective optimization problem involving conflicting objectives. In this paper, particle swarm optimization (PSO) is purposed to efficiently and effectively handle multiple conflicting objectives of IIR filter design. The weighted sum approach is used to minimize magnitude response and phase response of digital IIR filter simultaneously. The value of weights are searched using PSO along with filter coefficients thus assigning different weight vector to each individual particle. The order of the filter is controlled by a control gene whose value is also optimized along with the filter coefficients to obtain optimum order of designed IIR filter. The proposed algorithm shows competitive results with improved diversity and convergence.

Keywords: Digital Infinite-Impulse Response Filters, Multi-Objective Optimization, Particle Swarm Optimization, Lowest Order, Magnitude Response, Phase Response.

FEA Aided Design of Power Shunt-Reactors with Discretely-Distributed Air-Gaps

by Atilla Donuk, Muammer Ermis

Vol. 8. n. 2, pp. 891-903

Abstract - In this paper, a Finite Element Analysis (FEA) aided design methodology for power shunt-reactors is proposed. The lack of simple and straightforward expressions for the calculation of gap-loss component and leakage inductance is the bottleneck of a fully analytical design procedure. To tackle with the difficulty arising from the calculation of gap-loss, the total air-gap is subdivided into several discretely-distributed air-gaps. This makes the gap-loss component negligibly small in comparison with the core loss. The preliminary design of the target reactor can therefore be achieved analytically by using an initial estimate of percentage leakage inductance. The preliminary design can then be tested and fine-tuned by using Maxwell 3D Magnetostatic Excitation and 2D Transient Sinusoidal Current Excitation tools,in the second phase of the recommended design procedure. The reactor under design can be optimized according to one of minimum Initial Cost, minimum Total Loss or minimum Present Value Cost design objectives, upon the request of the customer or the designer. Advantages and disadvantages of Maxwell 3D and 2D Transient Sinusoidal Current Excitation and Transient Sinusoidal Voltage Excitation analyses facilities are also discussed in the paper.

Keywords: Discretely-Distributed Air- Gaps, Finite Element Analysis, Inductance, Shunt-Reactor.

Maximizing the Magnetic Force Generated by an Actuator with Non-Magnetic Body in a Ferrofluid Pre-Magnetized by Permanent Magnets

by R. Olaru, C. Petrescu, A. Arcire

Vol. 8. n. 2, pp. 904-911

Abstract - The purpose of this paper is to investigate possibilities and means that lead to the increase of the magnetic force generated by an actuator with a non-magnetic body levitated in a ferrofluid pre-magnetized by permanent magnets. The numerical simulations outline the components of the structure, dimensions and magnetic constants of materials that render a maximum magnetic force. The experimental measurements effectuated on an experimental model of the actuator are in acceptable agreement with theoretical and simulation results.

Keywords: Actuators, Ferrofluid, Magnetic Fluid, Magnetic Force.

Digital Generator Capability Curve for Improving Optimal Power Flow based on IPSO

by Mat Syai’in, Kuo Lung Lian, Adi Soeprijanto

Vol. 8. n. 2, pp. 912-919

Abstract - The generator capability curve (GCC) based on neural network (NN) is used as a constraint in optimal power flow based on improved particle swarm optimization (OPF-IPSO) to replace rectangular (Pmin-Pmax and Qmin-Qmax) constraint in achieving lower cost at the same security level. The security check algorithm is developed to eliminate the complicated mathematical equations in employing GCC as a constraint in OPF-IPSO. The algorithm is very simple and flexible especially for representing non-linear generation operation limits and under excitation operation areas. In effort to avoid local optimal solution and to get global optimal solution faster, chaotic parameter is used in updating weights of PSO. The data used to verify the performance of the proposed method is the Java-Bali 500 kV power systems that containt 8 generators and 23 buses.

Keywords: Optimal Power Flow, Generator Capability Curve, Neural Network, Improved Particle Swarm Optimization, Chaotic Parameter.

Analysis of Variation of Brillouin and Rayleigh Scattering Coefficients with Thermal Strain in Landau-Placzek Ratio Based Optical Fiber Distributed Sensing for XLPE Insulated Power Cables

by Abdurrahman Gunday, Sait Eser Karlik, Gunes Yilmaz

Vol. 8. n. 2, pp. 920-929

Abstract - The optical fiber distributed sensing method based on Landau-Placzek Ratio (LPR), where Rayleigh and Brillouin scattering coefficients are utilized, is widely used for detecting thermal strain formations in XLPE insulated power cables. In this study, using strain dependence of material characteristics in XLPE cable insulation, i.e. Young and Shear moduli and the Poisson ratio, variations of Rayleigh and Brillouin scattering coefficients with thermal strain and their thermal strain sensitivities have been analyzed. Using Matlab R2008a, behaviour of the sensing fiber integrated to a 64/110 kV power cable has been obtained with simulations for 318 K – 339 K temperature range and 668 με - 1231 με thermal strain range. For thermal strain variations in 668 με - 1231 με range, while thermal strain sensitivity of Rayleigh scattering coefficient is changing from 1.8286 × 10^-4 % to 1.8267 × 10^-4 % , that of Brillouin scattering coefficient changes from – 7.9727 × 10^-4 % to - 8.0086 × 10^-4 % . Using simulation results, thermal strain sensitivity variations of Rayleigh and Brillouin scattering coefficients have been computed as ~ - 3.27 × 10^-10 %/με and ~ - 6.38 × 10^-9 %/με, respectively. In 668 με - 1231 με range, it has been observed that thermal strain sensitivity of LPR changes from 9.7439 × 10^-4 % to 9.7068 × 10^-4 %. Using LPR simulation results, strain-dependent LPR formula derived with the analytical method has been simplified and expressed with a linear equation.

Keywords: Brillouin Scattering Coefficient, Distributed Sensing, Landau-Placzek Ratio, Optical Fiber, Rayleigh Scattering Coefficient, Thermal Strain.

A Cost Efficient Algorithm for System Reliability Calculation with Aleatory and Epistemic Uncertainties Using Evidence Theory

by B. Suo, C. Zeng, Y. S. Cheng, J. Li

Vol. 8. n. 2, pp. 930-937

Abstract - In reliability calculation of complex system, it is always in the situation that experimental data is inadequate, or information is not complete, which makes the system not only involving aleotory uncertainty, but also epistemic uncertainty. To reduce the cost of reliability calculation, an effective approach with evidence theory is developed. In this approach, the mean of belief and plausibility function is taken as the approximation of system reliability. The discretization methods for uncertain parameters are discussed when system involves only aleatory uncertainty, and involves aleatory and epistemic uncertainties simultaneously, respectively. Algorithms for belief and plausibility function evaluation are proposed for monotonic and non-monotonic system. Four numerical examples with different conditions are studied. Simulation results show that, the proposed method is much more effective than Monte Carlo method without sacrificing the accuracy of resulting reliability, and is a general method which is applicable for various systems with different types of information.

Keywords: Reliability Calculation, Evidence Theory, Aleatory Uncertainty, Epistemic Uncertainty, Cost Efficient Algorithm.