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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Electrical Engineering and Technology
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The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 10, Issue 6 - Nov 2015
Volume 10, Issue 5 - Sep 2015
Volume 10, Issue 4 - Jul 2015
Volume 10, Issue 3 - May 2015
Volume 10, Issue 2 - Mar 2015
Volume 10, Issue 1 - Jan 2015
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Assessing the Impact of Advanced Technologies on Utilization Improvement of Substations
Han, Dong ; Yan, Zheng ; Zhang, Dao-Tian ; Song, Yi-Qun ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1921~1929
DOI : 10.5370/JEET.2015.10.5.1921
The smart substation is the heart of a transmission system, which is particularly emphasized as the most significant composition of smart grids in China. In order to assess the functionality performance of substation technologies, this paper presents methods used to identify the most promising solutions for smart substation design and to evaluate the technical levels of available technologies. The multi-index optimization model is presented to address the issue of smart substation planning. A mathematical model of the planning decision problem is established with multiple objectives consisting of economic, reliability, and green key indices, and many kinds of concerns including physical and environmentally friendly operations are formulated as a set of constraints. With respect to the assessment of the technical level regarding integration of advanced technologies into a substation, a modified grey whitenization weight function is adopted to structure a novel grey clustering method. The proposed grey clustering approach is used to overcome the difficulty of insufficient quantitative assessment capacity for traditional methods. The evaluation of technical effects provides the classification definition for the development phase and the maturity level of the smart substation. The effectiveness of the proposed approaches in planning decision-making and evaluation of construction efforts is demonstrated with case studies involving the actual smart substation projects of Wenchongkou substation in China Southern Power Grid (CSG) and Mengzi substation in State Grid Corporation of China (SGCC).
Ordinal Optimization Theory Based Planning for Clustered Wind Farms Considering the Capacity Credit
Wang, Yi ; Zhang, Ning ; Kang, Chongqing ; Xu, Qianyao ; Li, Hui ; Xiao, Jinyu ; Wang, Zhidong ; Shi, Rui ; Wang, Shuai ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1930~1939
DOI : 10.5370/JEET.2015.10.5.1930
Wind power planning aims to locate and size wind farms optimally. Traditionally, wind power planners tend to choose the wind farms with the richest wind resources to maximize the energy benefit. However, the capacity benefit of wind power should also be considered in large-scale clustered wind farm planning because the correlation among the wind farms exerts an obvious influence on the capacity benefit brought about by the combined wind power. This paper proposes a planning model considering both the energy and the capacity benefit of the wind farms. The capacity benefit is evaluated by the wind power capacity credit. The Ordinal Optimization (OO) Theory, capable of handling problems with non-analytical forms, is applied to address the model. To verify the feasibility and advantages of the model, the proposed model is compared with a widely used genetic algorithm (GA) via a modified IEEE RTS-79 system and the real world case of Ningxia, China. The results show that the diversity of the wind farm enhances the capacity credit of wind power.
Enhanced Particle Swarm Optimization for Short-Term Non-Convex Economic Scheduling of Hydrothermal Energy Systems
Jadoun, Vinay Kumar ; Gupta, Nikhil ; Niazi, K. R. ; Swarnkar, Anil ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1940~1949
DOI : 10.5370/JEET.2015.10.5.1940
This paper presents an Enhanced Particle Swarm Optimization (EPSO) to solve short-term hydrothermal scheduling (STHS) problem with non-convex fuel cost function and a variety of operational constraints related to hydro and thermal units. The operators of the conventional PSO are dynamically controlled using exponential functions for better exploration and exploitation of the search space. The overall methodology efficiently regulates the velocity of particles during their flight and results in substantial improvement in the conventional PSO. The effectiveness of the proposed method has been tested for STHS of two standard test generating systems while considering several operational constraints like system power balance constraints, power generation limit constraints, reservoir storage volume limit constraints, water discharge rate limit constraints, water dynamic balance constraints, initial and end reservoir storage volume limit constraints, valve-point loading effect, etc. The application results show that the proposed EPSO method is capable to solve the hard combinatorial constraint optimization problems very efficiently.
Optimal Reserve Allocation to Maximize Kinetic Energy in a Wind Power Plant
Yoon, Gihwan ; Lee, Hyewon ; Lee, Jinsik ; Yoon, Gi-Gab ; Park, Jong Keun ; Kang, Yong Cheol ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1950~1957
DOI : 10.5370/JEET.2015.10.5.1950
Modern wind generators (WGs) are forced or encouraged to participate in frequency control in the form of inertial and/or primary control to improve the frequency stability of power systems. To participate in primary control, WGs should perform deloaded operation that maintains reserve power using speed and/or pitch-angle control. This paper proposes an optimization formulation that allocates the required reserve to WGs to maximize the kinetic energy (KE) stored in a wind power plant (WPP). The proposed optimization formulation considers the rotor speed margin of each WG to the maximum speed limit, which is different from each other because of the wake effects in a WPP. As a result, the proposed formulation allows a WG with a lower rotor speed to retain more KE in the WPP. The performance of the proposed formulation was investigated in a 100-MW WPP consisting of 20 units of 5-MW permanent magnet synchronous generators using an EMTP-RV simulator. The results show that the proposed formulation retains the maximum amount of KE with the same reserve and successfully increases the frequency nadir in a power system by releasing the stored KE in a WPP in the case of a disturbance.
A New Definition of Short-circuit Ratio for Multi-converter HVDC Systems
Liu, Dengfeng ; Shi, Dongyuan ; Li, Yinhong ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1958~1968
DOI : 10.5370/JEET.2015.10.5.1958
In this paper, a new definition of short-circuit ratio concept for multi-converter HVDC systems is proposed. Analysis results of voltage interaction between converters show that the reactive power-voltage characteristic of a converter has a dominant effect on voltage interaction level compared with its active power-voltage characteristic. Such a relation between converter reactive power and voltage interaction level supports taking the former into account in the definition of short-circuit ratio concept for multi-converter systems. The proposed definition is verified by the method of maximum power curve for various system configurations. Furthermore, a formula to calculate transient overvoltage for multi-converter systems is derived based on the proposed definition, and the efficiency of the derived formula is verified.
Virtual Inertia Control of D-PMSG Based on the Principle of Active Disturbance Rejection Control
Shi, Qiaoming ; Wang, Gang ; Fu, Lijun ; Liu, Yang ; Wu, You ; Xu, Li ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1969~1982
DOI : 10.5370/JEET.2015.10.5.1969
The virtual inertia control (VIC) of wind turbine with directly-driven permanent-magnet synchronous generator (D-PMSG) can act similarly to the conventional synchronous generator in inertia response and frequency control, thereby supporting the system frequency stability. However, because the wind speed is inconstant and changeable to a certain extent and the D-PMSG is a complex nonlinear system, there are great difficulties in the virtual inertia optimal control of the D-PMSG. Based on the design principle of the active disturbance rejection control (ADRC), this paper presents a new VIC strategy for the D-PMSG from the perspective of power disturbance suppression in the system. The strategy helps fulfill the power grid disturbance estimation and compensation by means of the extended state observer (ESO) so as to improve the disturbance-resisting performance of the system. Compared with conventional proportional-derivative virtual inertia control (PDVIC), this method, which is of better adaptability and robustness, can not only improve the property of the D-PMSG responding to the system frequency but also reduce the influence of wind speed disturbance. The simulation and experiment results have verified the effectiveness and feasibility of the VIC based on the ADRC.
Compensation of Power Fluctuations of PV Generation System by SMES Based on Interleaving Technique
Kim, Seung-Tak ; Park, Jung-Wook ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1983~1988
DOI : 10.5370/JEET.2015.10.5.1983
This paper proposes the enhanced application of superconducting magnetic energy storage (SMES) for the effective compensation of power fluctuations based on the interleaving technique. With increases in demand for renewable energy based photovoltaic (PV) generation system, the output power fluctuations from PV generation system due to sudden changes in environmental conditions can cause serious problems such as grid voltage and frequency variations. To solve this problem, the SMES system is applied with its superior characteristics with respect to high power density, fast response for charge and discharge operations, system efficiency, etc. In particular, the compensation capability is effectively improved by the proposed interleaving technique based on its parallel structure. The dynamic performance of the system designed using the proposed method is evaluated with several case studies through time-domain simulations.
Peak-Valley Current Mode Controlled H-Bridge Inverter with Digital Slope Compensation for Cycle-by-Cycle Current Regulation
Manoharan, Mohana Sundar ; Ahmed, Ashraf ; Park, Joung-Hu ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 1989~2000
DOI : 10.5370/JEET.2015.10.5.1989
In this paper, digital peak current mode control for single phase H-bridge inverters is developed and implemented. The digital peak current mode control is achieved by directly controlling the PWM signals by cycle-by-cycle current limitation. Unlike the DC-DC converter where the output voltage always remains in the positive region, the output of DC-AC inverter flips from positive to negative region continuously. Therefore, when the inverter operates in negative region, the control should be changed to valley current mode control. Thus, a novel control logic circuit is required for the function and need to be analyzed for the hardware to track the sinusoidal reference in both regions. The problem of sub-harmonic instability which is inherent with peak current mode control is also addressed, and then proposes the digital slope compensation in constant-sloped external ramp to suppress the oscillation. For unipolar PWM switching method, an adaptive slope compensation in digital manner is also proposed. In this paper, the operating principles and design guidelines of the proposed scheme are presented, along with the performance analysis and numerical simulation. Also, a 200W inverter hardware prototype has been implemented for experimental verification of the proposed controller scheme.
A Novel Flexible PCB Conductive Structure for Electrodynamic Bearings and Measurement in its Induced Voltage
Ding, Guoping ; Sandtner, Jan ; Bleuler, Hannes ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2001~2008
DOI : 10.5370/JEET.2015.10.5.2001
This paper proposes the concept of FlexPCB(flexible Printed Circuit Board) conductive structure for electrodynamic bearings. It has three main advantages: easy “printing” of considerably thin conductive wires, resulting in potential reduction in stray eddy currents; realization of specific conductive configurations with high precision to optimize the eddy current flowing; simplicity in being wound to cylinders or hollow cylinders of different diameters. To verify this new concept, the FlexPCB conductive structure was manufactured, an axial electrodynamic bearing test rig was built and the conductive structure's induced voltage was measured along the axial displacements from 0mm to 56mm at three rotating speeds. The finite element method was used to calcuatlate the flux density of electrodynamic bearing and induced voltage of the FlexPCB conductive structure. The experimental results are compared with the results from the FEM calculation. It is concluded that the measured and calculated induced voltages have consistency in the middle part of the bearing.
Rotor Position Estimation Strategy Using Artificial Neural Network for a Novel Design Transverse Flux Machine
Turker, Cigdem Gundogan ; Kuyumcu, Feriha Erfan ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2009~2017
DOI : 10.5370/JEET.2015.10.5.2009
The E-Core Transverse Flux Machine is a different design of transverse flux machines combined with reluctance principle. Determination of the rotor position is important for the movement of the ETFM by switching the phase currents in synchronism with the inductance regions of the stator windings. It is the first time that rotor position estimation based on Artificial Neural Network (ANN) is purposed to eliminate the position sensor for the ETFM. Simulation and experimental tests are demonstrated for the feasibility of the proposed estimation algorithm for the exercise bike application of the ETFM.
A Ripple Rejection Inherited RPWM for VSI Working with Fluctuating DC Link Voltage
Jarin, T. ; Subburaj, P. ; Bright, Shibu J V ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2018~2030
DOI : 10.5370/JEET.2015.10.5.2018
A two stage ac drive configuration consisting of a single-phase line commutated rectifier and a three-phase voltage source inverter (VSI) is very common in low and medium power applications. The deterministic pulse width modulation (PWM) methods like sinusoidal PWM (SPWM) could not be considered as an ideal choice for modern drives since they result mechanical vibration and acoustic noise, and limit the application scope. This is due to the incapability of the deterministic PWM strategies in sprawling the harmonic power. The random PWM (RPWM) approaches could solve this issue by creating continuous harmonic profile instead of discrete clusters of dominant harmonics. Insufficient filtering at dc link results in the amplitude distortion of the input dc voltage to the VSI and has the most significant impact on the spectral errors (difference between theoretical and practical spectra). It is obvious that the sprawling effect of RPWM undoubtedly influenced by input fluctuation and the discrete harmonic clusters may reappear. The influence of dc link fluctuation on harmonics and their spreading effect in the VSI remains invalidated. A case study is done with four different filter capacitor values in this paper and results are compared with the constant dc input operation. This paper also proposes an ingenious RPWM, a ripple dosed sinusoidal reference-random carrier PWM (RDSRRCPWM), which has the innate capacity of suppressing the effect of input fluctuation in the output than the other modern PWM methods. MATLAB based simulation study reveals the fundamental component, total harmonic distortion (THD) and harmonic spread factor (HSF) for various modulation indices. The non-ideal dc link is managed well with the developed RDSRRCPWM applied to the VSI and tested in a proto type VSI using the field programmable gate array (FPGA).
The Dimmable Single-stage Asymmetrical LLC Resonant LED Driver with Low Voltage Stress Across Switching Devices
Kim, Seong-Ju ; Kim, Young-Seok ; Kim, Choon-Taek ; Lee, Joon-Min ; La, Jae-Du ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2031~2039
DOI : 10.5370/JEET.2015.10.5.2031
In the LED lighting industry, the dimming function in the LED lamp is required by demands of many consumers. To drive this LED lighting, various types of power converters have been applied. Among them, an LLC resonant converter could be applied for high power LED lighting because of its high efficiency and high power density, etc. The function of power factor correction (PFC) might be added to it. In this paper, a dimmable single-stage asymmetrical LLC resonant converter is proposed. The proposed converter performs both input-current harmonics reduction and PFC using the discontinuous conduction mode (DCM). Also, the lower voltage stress across switching devices as well as the zero voltage switching (ZVS) in switching devices is realized by the proposed topology. It can reduce cost and has high efficiency of the driver. In addition, the regulation of the output power by variable switching frequency can vary the brightness of a light. In the proposed converter, one of the attractive advantages doesn’t need any extra control circuits for the dimming function. To verify the performance of the proposed converter, simulation and experimental results from a 300W prototype are provided.
Thermal Analysis of High Speed Induction Motor by Using Lumped-Circuit Parameters
Han, Pil-Wan ; Choi, Jae-Hak ; Kim, Dong-Jun ; Chun, Yon-Do ; Bang, Deok-Je ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2040~2045
DOI : 10.5370/JEET.2015.10.5.2040
This paper deals with the electromagnetic and thermal analysis of high speed induction motor. The induction motor is analyzed by time-varying magnetic finite element method and its thermal analysis is carried out by using analytical lumped-circuit method. Analysis results are compared with the experiment of 29kW high speed motor prototype at 12,000rpm.
Prediction of Insulation Capability for Ground Fault to Consider Asymmetry in SF6 Circuit Breaker
Oh, Yeon-Ho ; Song, Ki-Dong ; Kim, Hong-Kyu ; Lee, Hae June ; Hahn, Sung-Chin ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2046~2051
DOI : 10.5370/JEET.2015.10.5.2046
Currently, most high-voltage gas circuit breakers (CBs) include asymmetrical geometries in the shield, the tank, the hot-gas exhaust, and the connection parts for bushings. For this reason, a 3-dimensional (3-D) analysis of the insulation capability is necessary, rather than a 2-D analysis. However, a 3-D analysis has difficulties due to the computational time and complex modeling. This paper presents a 3-D analysis considering the asymmetry in high-voltage gas CBs and a technique to reduce the calculation time. In the proposed technique, the arc plasma requiring the most computational time is first calculated by a 2-D analysis. Then, the results such as pressure, temperature, and velocity are input as a source for the 3-D analysis. This technique is applied to a 145kV self-blast-type CB and the analysis result exhibits good agreement with the experimental result.
Current Control Method of WRSM in High-speed Operation Range
Lee, Jae-Jun ; Lee, Ki-Doek ; Jang, Ik-Sang ; Lee, Sung-Gu ; Chae, Woong-Chan ; Lee, Hyung-Woo ; Lee, Ju ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2052~2056
DOI : 10.5370/JEET.2015.10.5.2052
This Paper analyzes the characteristics of the WRSM in high-speed operation range. To verify the control characteritics of various WRSM models, the relative position of the central point of current limit circle and voltage limit ellipse is defined as M value and 3 models according to M
value are designed through inductance change. Through the designed models, the current control method of 3-variables control for maximum power especially in high-speed operation range is presented.
Analysis and Experimental Characterization of Low Speed Direct Drive Fractional Slot Concentrated Winding Surface Permanent Magnet Synchronous Motor with Consequent Pole Rotor
Chung, Shi-Uk ; Chun, Yon-Do ; Moon, Seok-Hwan ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2057~2061
DOI : 10.5370/JEET.2015.10.5.2057
This paper describes analysis and experimental characterization of low speed direct drive fractional slot concentrated winding (FSCW) surface permanent magnet synchronous motor (SPMSM) with consequent pole (CP) rotor, for which studies have been recently performed. The proposed motor, which consists of 30 poles and 36 slots, is analyzed and characterized by extensive 2D finite element analysis (FEA) and together with 3D FEA for an appropriate PM overhang length design. The validity of the analysis is confirmed by the corresponding experiments which fully characterize the proposed motor with excellent agreement between the FEA and the experiments. Thermal stability is also experimentally examined to determine continuous operating points and instantaneous operating points of the proposed motor. It is highly expected that the proposed motor is applicable for low speed direct drive applications.
Research on the Inter-harmonics Equivalent Impedance of Series Hybrid Active Power Filter
Jian-gong, Zhang ; Jian-ben, Liu ; Shao-jun, Dai ; Qiao-fu, Chen ; Jun-jia, He ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2062~2069
DOI : 10.5370/JEET.2015.10.5.2062
In the series hybrid active power filter (SHAPF) with magnetic flux compensation (MFC), the system current oscillate in the experimental results when adding the same phase harmonic current command in current control block. This condition endangers the security of the SHAPF. Taking the digit period average arithmetic as example, this paper explains the inter-harmonics current oscillation in the experiment. The conclusion is that the SHAPF is unstable to the inter-harmonics current in theory. Limited by the capacity of the inverter, the system current and the inverter output current do not increase to infinite. At last, some methods are proposed to solve this problem. From the practical viewpoint, the voltage feed-forward control is easy to achieve. It can suppress the current oscillation problems, and also improve the filtering effect. The feasibility of the methods is validated by both the emulation and experiment results.
Application of Nano Coating to ACSR conductor for the Protection of Transmission lines against Solar Storms, Surface Flashovers, Corona and Over voltages
Selvaraj, D. Edison ; Mohanadasse, K. ; Sugumaran, C. Pugazhendhi ; Vijayaraj, R. ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2070~2076
DOI : 10.5370/JEET.2015.10.5.2070
Nano composite materials were multi-constituent combinations of nano dimensional phases with distinct differences in structure, chemistry and properties. Nano particles were less likely to create large stress concentrations and thereby can avoid the compromise of the material ductility while improve other mechanical properties. Corona discharge was an electrical discharge. The ionization of a fluid surrounding a conductor was electrically energized. This discharge would occur when the strength of the electric field around the conductor was high enough to form a conductive region, but not high enough to cause electrical breakdown or arcing to nearby objects. This paper shows all the studies done on the preparation of nano fillers. Special attention has given to the ACSR transmission line conductor, TiO
nano fillers and also to the evaluation of corona resistance on dielectric materials discussed in detail. The measurement of the dielectric properties of the nano fillers and the parameters influencing them were also discussed in the paper. Corona discharge test reveals that in 0%N ACSR sample corona loss was directly proportional to the applied line voltage. No significant change in corona loss between 0%N and 1%N. When TiO
nano filler concentration was increased up to 10%N fine decrement in corona loss was found when compared to base ACSR conductor, corona loss was decreased by 40.67% in 10%N ACSR sample. It was also found from the surface conditions test that inorganic TiO
nano filler increases the key parameters like tensile strength and erosion depth.
Calculation on the Ion Flow Field under HVDC Transmission Lines Considering Wind Effects
Wu, Jing ; Gao, Sheng ; Liu, Yuxiao ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2077~2082
DOI : 10.5370/JEET.2015.10.5.2077
Based on Deutsch assumption, a calculation method on the electric field over the ground surface under HVDC transmission lines in the wind is proposed. Analyzing the wind effects on the electric field and the space charge density the existing method based on Deutsch assumption is improved through adding the wind speed to the ion flow field equations. The programming details are illustrated. The calculation results at zero wind speed are compared with available data to validate the code program. Then the ionized fields which resulted from corona of ±800kV HVDC lines are analyzed. Both the electric field and the current density on the ground level are computed under different wind direction and speed. The computation results are in good agreement with measurements. The presented method and code program can be used to rapidly predict and evaluate the wind effects in HVDC transmission engineering.
RTDS-based Model Component Development of a Tri-axial HTS Power Cable and Transient Characteristic Analysis
Ha, Sun-Kyoung ; Kim, Sung-Kyu ; Kim, Jin-Geun ; Park, Minwon ; Yu, In-Keun ; Lee, Sangjin ; Kim, Jae-Ho ; Sim, Kideok ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2083~2088
DOI : 10.5370/JEET.2015.10.5.2083
The transient characteristics of the tri-axial High Temperature Superconducting (HTS) power cable are different from those of a conventional power cable depending on whether the cable is under a steady or transient state due to the quench. Verification using simulation tools is required to confirm both the characteristics of the cable and the effect of the cable when it is applied to a real utility. However, a component for the cable has not been provided in simulation tools; thus the RTDS-based model component of the tri-axial HTS power cable was developed, and a simulation was performed under the transient state. The considered properties of model component include resistance, reactance and temperature. Simulation results indicate the variation of HTS power cable condition. The results are used for the transient characteristic analysis and stability verification of the tri-axial HTS power cable. In the future, the RTDS-based model component of the cable will be used to implement the hardware-in-the-loop simulation with a protection device.
Cavity and Interface effect of PI-Film on Charge Accumulation and PD Activity under Bipolar Pulse Voltage
Akram, Shakeel ; Wu, Guangning ; Gao, GuoQiang ; Liu, Yang ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2089~2098
DOI : 10.5370/JEET.2015.10.5.2089
With the continuous development in insulation of electrical equipment design, the reliability of the system has been enhanced. However, in the manufacturing process and during operation under continues stresses introduce local defects, such as voids between interfaces that can responsible to occurrence of partial discharge (PD), electric field distortion and accumulation of charges. These defects may lead to localize corrosion and material degradation of insulation system, and a serious threat to the equipment. A model of three layers of PI film with air gap is presented to understand the influence of interface and voids on exploitation conditions such as strong electrical field, PD activity and charge movement. The analytical analysis, and experimental results are good agreement and show that the lose contact between interfaces accumulate more residual charges and in consequences increase the electric field intensity and accelerates internal discharges. These residual charges are trapped charges, injected by the electrodes has often same polarity, so the electric field in cavities increases significantly and thus partial discharge inception voltage (PDIV) decreases. Contrary, number of PD discharge quantity increases due to interface. Interfacial polarization effect has opposite impact on electric field and PDIV as compare to void.
Suggested Temperature Monitoring System for Distribution Transformers by Using Microcontroller Scheme
El-Gawad, Amal F. Abd ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2099~2104
DOI : 10.5370/JEET.2015.10.5.2099
The paper presents a monitoring system for the cooling of distribution transformers. The suggested system is controlled by a microcontroller scheme. The system is designed to control the oil temperature. It gives a solution to improve the cooling system by adding a number of fans especially for indoor transformers that are placed in badly-ventilated rooms. Also, the paper includes an alarm system with the possibility of tripping the transformer if it is necessary. The monitoring system consists of acquisition temperature sensor, and on-site unit. The hardware and software of the on-site unit are demonstrated with sufficient illustrations. Small prototype is constructed in the laboratory. Some laboratory experiments are carried out for examining the designed circuit by using Proteus Virtual System Modeling as well as for testing the prototype monitoring system. Concerning this research point, a study is carried out to evaluate the economic feasibility. The results are recorded and associated with many recommendations that may be valuable to electrical distribution (utility) companies.
Study of Dielectric Properties of a Potential RBD Palm Oil and RBD Soybean Oil Mixture as Insulating Liquid in Transformer
Azmi, Kiasatina ; Ahmad, Azmier ; Kamarol, Mohamad ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2105~2119
DOI : 10.5370/JEET.2015.10.5.2105
This paper reported the experimental result of dielectric properties of Refined, Bleached and Deodorized Palm Oil (RBDPO) combined with 0-50% of Refined, Bleached and Deodorized Soybean Oil (RBDSO). The dielectric strength and relative permittivity of RBDPO/RBDSO was higher compared to mineral oil at all ranges of ratios and temperatures which indicated a positive sign for its possible use as insulating liquid in a transformer. All ratios of the RBDPO/RBDSO mixture also demonstrated lower dissipation factor compared to mineral oil at 40℃, 70℃ and 90℃. Apart from that, the kinematic viscosity for the oil mixtures shown exceeded the IEC 60296 as well as the mineral oil results. 70%RBDPO/30%RBDSO mixture ratio was chosen as the best mixing percentage after comparison was made with the mineral oil and IEC 60296 standard where the mixture accumulated the most satisfactory of dielectric properties hence making it as the potential candidate for palm and soybean-based transformer oil.
Theoretical and Experimental Investigation on the Probe Design of a Ridge-loaded Slot Type for Near-Field Scanning Microwave Microscope
Son, Hyeok-Woo ; Kim, Byung-Mun ; Hong, Jae-Pyo ; Cho, Young-Ki ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2120~2125
DOI : 10.5370/JEET.2015.10.5.2120
In this paper, a rectangular waveguide probe with a ridge-loaded straight slot (RLSS) is presented for a near-field scanning microwave microscope (NSMM). The RLSS is located laterally at the end wall of the cavity and is loaded on double ridges in a narrow straight slot to improve the spatial resolution compared with a straight slot. The probe consists of a rectangular cavity with an RLSS and a feed section of a WR-90 rectangular waveguide. When the proposed NSMM is located at distance of 0.1mm in front of a substrate without patches or strips, the simulated full width at half maximum (FWHM) of the probe improve by approximately 31.5 % compared with that of a straight slot without ridges. One dimensional scanning of the E-plane on a sample under test was conducted, and the reflection coefficient of the near-field scanning probe is presented.
A Localization Method for First and Second Heart Sounds Based on Energy Detection and Interval Regulation
Min, Se Dong ; Shin, Hangsik ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2126~2134
DOI : 10.5370/JEET.2015.10.5.2126
The present study suggests a localization method for the first (S
) and the second (S
) feature of heart sounds, based on an algorithm involving frequency filtering, energy detection, and interval regulation. Localization accuracy was evaluated by comparing the algorithm with the traditional Hilbert transform-based localization method. Results show that the sensitivity and the positive predictivity value of proposed method, respectively, were 97.27 % and 99.94 % in S
detection and 94.99 % and 100 % in S
Vertex Coloring based Slot Reuse Scheduling for Power Line Communications
Yoon, Sung-Guk ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2135~2141
DOI : 10.5370/JEET.2015.10.5.2135
Power line communication (PLC) is one of the major communication technologies in smart grid since it combines good communication capability with easy and simple deployment. As a power network can be modeled as a graph, we propose a vertex coloring based slot reuse scheduling in the time division multiple access (TDMA) period for PLCs. Our objective is to minimize the number of assigned time slots, while satisfying the quality of service (QoS) requirement of each station. Since the scheduling problem is NP-hard, we propose an efficient heuristic scheduling, which consists of repeated vertex coloring and slot reuse improvement algorithms. The simulation results confirm that the proposed algorithm significantly reduces the total number of time slots.
Real-time Footstep Planning and Following for Navigation of Humanoid Robots
Hong, Young-Dae ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2142~2148
DOI : 10.5370/JEET.2015.10.5.2142
This paper proposes novel real-time footstep planning and following methods for the navigation of humanoid robots. A footstep command is defined by a walking direction and step lengths for footstep planning. The walking direction is determined by a uni-vector field navigation method, and the allowable yawing range caused by hardware limitation is considered. The lateral step length is determined to avoid collisions between the two legs while walking. The sagittal step length is modified by a binary search algorithm when collision occurs between the robot body and obstacles in a narrow space. If the robot body still collides with obstacles despite the modification of the sagittal step length, the lateral step length is shifted at the next footstep. For footstep following, a walking pattern generator based on a 3-D linear inverted pendulum model is utilized, which can generate modifiable walking patterns using the zero-moment point variation scheme. Therefore, it enables a humanoid robot to follow the footstep command planned for each footstep. The effectiveness of the proposed method is verified through simulation and experiment.
Fragile Watermarking Scheme Based on Wavelet Edge Features
Vaishnavi, D. ; Subashini, T.S. ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2149~2154
DOI : 10.5370/JEET.2015.10.5.2149
This paper proposes a novel watermarking method to discover the tampers and localize it in digital image. The image which is to be used to generate a watermark is first wavelet decomposed and the edge feature from the sub bands of high frequency coefficients are retrieved to generate a watermark (Edge Feature Image) and which is to be embed on the cover image. Before embedding the watermark, the pixels of cover image are disordered through the Arnold Transform and this helps to upgrade the security of the watermark. The embedding of generated edge feature image is done only on the Least Significant Bit (LSB) of the cover image. The invisibleness and robustness of the proposed method is computed using Peak-Signal to Noise Ratio (PSNR) and Normalized Correlation (NC) and it proves that the proposed method delivers good results and the proposed method also detects and localizes the tampers efficiently. The invisibleness of proposed method is compared with the existing method and it proves that the proposed method is better.
Optical Method to Determine Gait Parameters Using Position Sensitive Detector
Jung, Gu-In ; Kim, Ji-Sun ; Lee, Tae-Hee ; Choi, Ju-Hyeon ; Oh, Han-Byeol ; Kim, A-Hee ; Goh, Bong-Jun ; Kim, Jun-Sik ; Lee, Eun-Suk ; Jun, Jae-Hoon ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2155~2161
DOI : 10.5370/JEET.2015.10.5.2155
This study suggests an optical method to measure cardinal of gait (step width, step length, and stride length) with position sensitive detector (PSD). The effect of reflector’s shape (flat and cylinder) on the PSD output voltage was examined for the application of the suggested system to real situations with a curved shape reflector (e.g. shoes). Various mathematical models were evaluated to find the optimal equation for the distance measurement. Considering the effect of shape on detected signal, the inverse polynomial model was developed. The suggested method is simple to operate, low in cost, small in size, and can evaluate gait parameters in real time. This method is expected to be useful in the field of rehabilitation and sport science
Design of Autonomous Cruise Controller with Linear Time Varying Model
Chang, Hyuk-Jun ; Yoon, Tae Kyun ; Lee, Hwi Chan ; Yoon, Myung Joon ; Moon, Chanwoo ; Ahn, Hyun-Sik ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2162~2169
DOI : 10.5370/JEET.2015.10.5.2162
Cruise control is a technology for automatically maintaining a steady speed of vehicle as set by the driver via controlling throttle valve and brake of vehicle. In this paper we investigate cruise controller design method with consideration for distance to vehicle ahead. We employ linear time varying (LTV) model to describe longitudinal vehicle dynamic motion. With this LTV system we approximately model the nonlinear dynamics of vehicle speed by frequent update of the system parameters. In addition we reformulate the LTV system by transforming distance to leading vehicle into variation of system parameters of the model. Note that in conventional control problem formulation this distance is considered as disturbance which should be rejected. Consequently a controller can be designed by pole placement at each instance of parameter update, based on the linear model with the present system parameters. The validity of this design method is examined by simulation study.
Effective and Reliable Speed Control of Permanent Magnet DC (PMDC) Motor under Variable Loads
Tuna, Murat ; Fidan, Can Bulent ; Kocabey, Sureyya ; Gorgulu, Sertac ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2170~2178
DOI : 10.5370/JEET.2015.10.5.2170
This paper presents the effective and reliable speed control of PMDC motors under variable loads and reference speeds. As is known DC motors are more preferred in industrial practices. This is that, the PMDC motors don’t require brush and commutator care and to increase in torque per motor depending on developments in power electronics. In this study, proportional-integral controller (PI) and fuzzy logic controller (FL) have been designed for speed control of PMDC motor. In the design of these controllers, characteristics such as minimum overrun time, response time to the load, settling time and ideal rise time have been taken into consideration for better stability performance. In this design, the best system response was searched by examining the effect of different defuzzification methods onto the fuzzy logic system response. In conclusion, it has been seen that FL controller has a better performance for variable speed-load control of PMDC motor compared to PI controller.
Underdetermined Blind Source Separation from Time-delayed Mixtures Based on Prior Information Exploitation
Zhang, Liangjun ; Yang, Jie ; Guo, Zhiqiang ; Zhou, Yanwei ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2179~2188
DOI : 10.5370/JEET.2015.10.5.2179
Recently, many researches have been done to solve the challenging problem of Blind Source Separation (BSS) problems in the underdetermined cases, and the “Two-step” method is widely used, which estimates the mixing matrix first and then extracts the sources. To estimate the mixing matrix, conventional algorithms such as Single-Source-Points (SSPs) detection only exploits the sparsity of original signals. This paper proposes a new underdetermined mixing matrix estimation method for time-delayed mixtures based on the receiver prior exploitation. The prior information is extracted from the specific structure of the complex-valued mixing matrix, which is used to derive a special criterion to determine the SSPs. Moreover, after selecting the SSPs, Agglomerative Hierarchical Clustering (AHC) is used to automaticly cluster, suppress, and estimate all the elements of mixing matrix. Finally, a convex-model based subspace method is applied for signal separation. Simulation results show that the proposed algorithm can estimate the mixing matrix and extract the original source signals with higher accuracy especially in low SNR environments, and does not need the number of sources before hand, which is more reliable in the real non-cooperative environment.
Disparity Refinement near the Object Boundaries for Virtual-View Quality Enhancement
Lee, Gyu-cheol ; Yoo, Jisang ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2189~2196
DOI : 10.5370/JEET.2015.10.5.2189
Stereo matching algorithm is usually used to obtain a disparity map from a pair of images. However, the disparity map obtained by using stereo matching contains lots of noise and error regions. In this paper, we propose a virtual-view synthesis algorithm using disparity refinement in order to improve the quality of the synthesized image. First, the error region is detected by examining the consistency of the disparity maps. Then, motion information is acquired by applying optical flow to texture component of the image in order to improve the performance. Then, the occlusion region is found using optical flow on the texture component of the image in order to improve the performance of the optical flow. The refined disparity map is finally used for the synthesis of the virtual view image. The experimental results show that the proposed algorithm improves the quality of the generated virtual-view.
Enhancing Medical Images by New Fuzzy Membership Function Median Based Noise Detection and Filtering Technique
Elaiyaraja, G. ; Kumaratharan, N. ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2197~2204
DOI : 10.5370/JEET.2015.10.5.2197
In recent years, medical image diagnosis has growing significant momentous in the medicinal field. Brain and lung image of patient are distorted with salt and pepper noise is caused by moving the head and chest during scanning process of patients. Reconstruction of these images is a most significant field of diagnostic evaluation and is produced clearly through techniques such as linear or non-linear filtering. However, restored images are produced with smaller amount of noise reduction in the presence of huge magnitude of salt and pepper noises. To eliminate the high density of salt and pepper noises from the reproduction of images, a new efficient fuzzy based median filtering algorithm with a moderate elapsed time is proposed in this paper. Reproduction image results show enhanced performance for the proposed algorithm over other available noise reduction filtering techniques in terms of peak signal -to -noise ratio (PSNR), mean square error (MSE), root mean square error (RMSE), mean absolute error (MAE), image enhancement factor (IMF) and structural similarity (SSIM) value when tested on different medical images like magnetic resonance imaging (MRI) and computer tomography (CT) scan brain image and CT scan lung image. The introduced algorithm is switching filter that recognize the noise pixels and then corrects them by using median filter with fuzzy two-sided π- membership function for extracting the local information.
Initial Study of a Wire Mesh Tomography Sensor for Liquid/Gas Component Investigation
Rahiman, M.H.F. ; Siow, L.T. ; Rahim, R.A. ; Zakaria, Z. ; Ang, Vernoon ;
Journal of Electrical Engineering and Technology, volume 10, issue 5, 2015, Pages 2205~2210
DOI : 10.5370/JEET.2015.10.5.2205
Experimental studies have been carried out to study the principle operation of the conductive type wire-mesh tomography sensor and analyse the wire-mesh tomography sensor for the liquid/gas two-phase flow interface and void fraction distribution in a process column. The measurement of the two-phase flows in the process column is based on the cross-sectional local instantaneous conductivity. The sensor consists of two planes of parallel electrode wires with 16 electrodes each and was placed orthogonally with each plane. The sensor electrode wires were made of tinned copper wire with an outer diameter of 0.91 mm which stretched over the sensor fixture. Therefore, this result in the mesh grid size with 5.53×5.53mm
. The wire-mesh sensor was tested in a horizontal liquid/gas two-phase flows process column with nominal diameter of 95.6 mm and the sampling frequency of 5882.3529 Hz. The tomogram results show that the wire-mesh tomography provides significant results to represent the void fraction distribution in the process column and estimation error was found in the liquid/gas interface level