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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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Journal DOI :
The Korean Institute of Electrical Engineers
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Volume & Issues
Volume 6, Issue 6 - Nov 2011
Volume 6, Issue 5 - Sep 2011
Volume 6, Issue 4 - Jul 2011
Volume 6, Issue 3 - May 2011
Volume 6, Issue 2 - Mar 2011
Volume 6, Issue 1 - Jan 2011
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ISO Coordination of Generator Maintenance Scheduling in Competitive Electricity Markets using Simulated Annealing
Han, Seok-Man ; Chung, Koo-Hyung ; Kim, Balho-H. ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 431~438
DOI : 10.5370/JEET.2011.6.4.431
To ensure that equipment outages do not directly impact the reliability of the ISO-controlled grid, market participants request permission and receive approval for planned outages from the independent system operator (ISO) in competitive electricity markets. In the face of major generation outages, the ISO will make a critical decision as regards the scheduling of the essential maintenance for myriads of generating units over a fixed planning horizon in accordance with security and adequacy assessments. Mainly, we are concerned with a fundamental framework for ISO's maintenance coordination in order to determine precedence of conflicting outages. Simulated annealing, a powerful, general-purpose optimization methodology suitable for real combinatorial search problems, is used. Generally, the ISO will put forward its best effort to adjust individual generator maintenance schedules according to the time preferences of each power generator (GENCO) by taking advantage of several factors such as installed capacity and relative weightings assigned to the GENCOs. Thus, computer testing on a four-GENCO model is conducted to demonstrate the effectiveness of the proposed method and the applicability of the solution scheme to large-scale maintenance scheduling coordination problems.
Study on Advanced Frequency Estimation Technique using Gain Compensation
Park, Chul-Won ; Shin, Dong-Kwang ; Kim, Chul-Hwan ; Kim, Hak-Man ; Kim, Yoon-Sang ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 439~446
DOI : 10.5370/JEET.2011.6.4.439
Frequency is an important operating parameter for the protection, control, and stability of a power system. Thus, it must be maintained very close to its nominal frequency. Due to the sudden change in generation and loads or faults in a power system, however, frequency deviates from its nominal value. An accurate monitoring of the power frequency is essential for optimum operation and prevention of wide area blackout. Most conventional frequency estimation schemes are based on the DFT filter. In these schemes, the gain error could cause defects when the frequency deviates from the nominal value. We present an advanced frequency estimation technique using gain compensation to enhance the DFT filter-based technique. The proposed technique can reduce the gain error caused when the frequency deviates from the nominal value. Simulation studies are performed using both the data from EMTP-RV software and the user-defined arbitrary signals to demonstrate the effectiveness of the proposed algorithm. Results show that the proposed algorithm achieves good performance under both steady state tests and dynamic conditions.
A Novel Energy Storage System based on Flywheel for Improving Power System Stability
Wu, Jinbo ; Wen, Jinyu ; Sun, Haishun ; Cheng, Shijie ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 447~458
DOI : 10.5370/JEET.2011.6.4.447
In this paper, a novel flywheel energy storage device, called the flexible power conditioner, which integrates both the characteristics of the flywheel energy storage and the doubly-fed induction machine, is proposed to improve power system stability. A prototype is developed and its principle, composition, and design are described in detail. The control system is investigated and the operating characteristics are analyzed. The test results based on the prototype are presented and evaluated. The test results illustrate that the prototype meets the design requirement on power regulation and starting, and provides a cost-effective and effective means to improve power system stability.
Phasor Estimation Algorithm Based on the Least Square Technique during CT Saturation
Lee, Dong-Gyu ; Kang, Sang-Hee ; Nam, Soon-Ryul ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 459~465
DOI : 10.5370/JEET.2011.6.4.459
A phasor estimation algorithm based on the least square curve fitting technique for the distorted secondary current due to current transformer (CT) saturation is proposed. The mathematical form of the secondary current during CT saturation is represented as the scaled primary current with magnetizing current. The information on the scaled primary current is estimated using the least square technique, with the measured secondary current in the saturated section. The proposed method can estimate the phasor of a fundamental frequency component during the saturated period. The performance of the algorithm is validated under various fault and CT conditions using a C400 CT model. A series of performance evaluations shows that the proposed phasor estimation algorithm can estimate the phasor of the fundamental frequency component with high accuracy, regardless of fault conditions and CT characteristics.
Protection for a Wind Turbine Generator in a Large Wind Farm
Zheng, Tai-Ying ; Kim, Yeon-Hee ; Kang, Yong-Cheol ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 466~473
DOI : 10.5370/JEET.2011.6.4.466
This paper proposes a protection algorithm for a wind turbine generator (WTG) in a large wind farm. To minimize the outage section, a protection relay for a WTG should operate instantaneously for an internal fault or a connected feeder fault, whereas the relay should not operate for an internal fault of another WTG connected to the same feeder or an adjacent feeder fault. In addition, the relay should operate with a delay for an inter-tie fault or a grid fault. An internal fault of another WTG connected to the same feeder or an adjacent feeder fault, where the relay should not operate, is determined based on the magnitude of the positive sequence current. To differentiate an internal fault or a connected feeder fault from an inter-tie fault or a grid fault, the phase angle of the negative sequence current is used to distinguish a fault type. The magnitude of the positive sequence current is then used to decide either instantaneous operation or delayed operation. The performance of the proposed algorithm is verified under various fault conditions with EMTP-RV generated data. The results indicate that the algorithm can successfully distinguish instantaneous operation, delayed operation, or non-operation depending on fault positions and types.
Enhancement of Power System Transient Stability and Power Quality Using a Novel Solid-state Fault Current Limiter
Fereidouni, A.R. ; Vahidi, B. ; Mehr, T. Hoseini ; Doiran, M. Garmroodi ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 474~483
DOI : 10.5370/JEET.2011.6.4.474
Solid-state fault current limiters (SSFCL) in power systems are alternative devices to limit prospective short circuit currents from reaching lower levels. Fault current limiters (FCL) can be classified into two categories: R-type (resistive) FCLs and L-type (inductive) FCLs. L-type FCL uses an inductor to limit fault level and is more efficient in suppressing voltage drop during a fault. In contrast, R-type FCL is constructed with a resistance and is more effective in consuming the acceleration energy of generators during a fault. Both functions enhance the transient stability of the power system. In the present paper, a novel SSFCL is proposed to enhance power system transient stability and power quality. The proposed SSFCL uses both functions of an L-type and R-type FCL. SSFCL consists of four diodes, one self-turn-off IGCT, a current-limiting by-pass inductor (L), and a variable resistance parallel with an inductor for improvement of power system stability and prevention of over-voltage across SSFCL. The main advantages of the proposed SSFCL are the simplicity of its structure and control, low steady-state impedance, fast response, and the existence of R-type and Ltype impedances during the fault, all of which improve power system stability and power quality. Simulations are accomplished in PSCAD/EMTDC.
Visualization of Dynamic Simulation Data for Power System Stability Assessment
Song, Chong-Suk ; Jang, Gil-Soo ; Park, Chang-Hyun ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 484~492
DOI : 10.5370/JEET.2011.6.4.484
Power system analyses, which involve the handling of massive data volumes, necessitate the use of effective visualization methods to facilitate analysis and assist the user in obtaining a clear understanding of the present state of the system. This paper introduces an interface that compensates for the limitations of the visualization modules of dynamic security assessment tools, such as PSS/e and TSAT, for power system variables including generator rotor angle and frequency. The compensation is made possible through the automatic provision of dynamic simulation data in visualized and tabular form for better data intuition, thereby considerably reducing the redundant manual operation and time required for data analysis. The interface also determines whether the generators are stable through a generator instability algorithm that scans simulation data and checks for an increase in swing or divergence. The proposed visualization methods are applied to the dynamic simulation results for contingencies in the Korean Electric Power Corporation system, and have been tested by power system researchers to verify the effectiveness of the data visualization interface.
Maximizing the Overall Satisfaction Degree of all Participants in the Market Using Real Code-based Genetic Algorithm by Optimally Locating and Sizing the Thyristor-Controlled Series Capacitor
Nabavi, Seyed M.H. ; Hajforoosh, Somayeh ; Hajforoosh, Sajad ; Karimi, Ali ; Khafafi, Kamran ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 493~504
DOI : 10.5370/JEET.2011.6.4.493
The present paper presents a genetic algorithm (GA) to maximize social welfare and perform congestion management by optimally placing and sizing one Thyristor-Controlled Series Capacitor (TCSC) device in a double-sided auction market. Simulation results, with line flow constraints before and after the compensation, are compared through the Sequential Quadratic Programming SQP method, and are used to analyze the effect of TCSC on the congestion levels of modified IEEE 14-bus and 30-bus test systems. Quadratic, smooth and nonsmooth (with sine components due to valve point loading effect) generator cost curves, and quadratic smooth consumer benefit functions are considered. The main aims of the present study are the inclusion of customer benefit in the social welfare maximization and congestion management objective function, the consideration of nonsmooth generator characteristics, and the optimal locating and sizing of the TCSC using real code-based GA to guarantee fast convergence to the best solution.
Performance of Passive Boost Switched Reluctance Converter for Single-phase Switched Reluctance Motor
Ahn, Jin-Woo ; Lee, Dong-Hee ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 505~512
DOI : 10.5370/JEET.2011.6.4.505
A novel passive boost power converter forsingle-phaseswitched reluctance motor is presented. A simple passive circuit is proposed comprisingthree diodes and one capacitor. The passive circuitis added in the front-end of a conventional asymmetric converter to obtain high negative bias. Based on this passive network, the terminal voltage of the converter side is a general DC-link voltage level in parallel mode up to a double DC-link voltage level in series mode. Thus,it can suppress the negative torque generation from the tail current and improve the output power. The results of the comparative simulation and experiments forthe conventional and proposed converter verify the performance of the proposed converter.
A New Unified Design Environment for Optimization of Electric Machines Based on Continuum Sensitivity and B-Spline Parametrization
Kim, Min-Ho ; Lee, Hyang-Beom ; Kim, Hyeong-Seok ; Byun, Jin-Kyu ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 513~518
DOI : 10.5370/JEET.2011.6.4.513
In this paper, a unified design environment is developed for the optimization of electric machines based on continuum sensitivity. For electromagnetic (EM) system analysis, COMSOL scripting environment is used. Optimization module is developed by MATLAB programming, which can be combined with COMSOL script commands. The modules are combined into one MATLAB project, and iteration process necessary for the optimization of EM system can be performed efficiently. During the design process, visual feedback of the current design status is given to the designer. In addition, the B-Spline parametrization of the nodal points is implemented to obtain smooth boundary of the device. The developed software is applied to the problem of finding uniform flux density distribution at the air gap of an electromagnet to verify its feasibility and effectiveness.
Investigation of the Mechanism of Period-doubling Bifurcation in Voltage Mode Controlled Buck-Boost Converter
Xie, Ling-Ling ; Gong, Ren-Xi ; Zhuo, Hao-Ze ; Wei, Jiong-Quan ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 519~526
DOI : 10.5370/JEET.2011.6.4.519
An investigation of the mechanism of period-doubling bifurcation in a voltage mode controlled buck-boost converter operating in discontinuous conduction mode is conducted from the viewpoint of nonlinear dynamical systems. The discrete iterative model describing the dynamics of the close-loop is derived. Period-doubling bifurcation occurs at certain values of the feedback factor. Results from numerical simulations and experiments are provided to verify the evolution of perioddoubling bifurcation, and the results are consistent with the theoretical analysis. These results show that the buck-boost converters exhibit a wide range of nonlinear behavior, and the system exhibits a typical period-doubling bifurcation route to chaos under particular operating conditions.
Optimization of Powder Core Inductors of Buck-Boost Converters for Hybrid Electric Vehicles
You, Bong-Gi ; Kim, Jong-Soo ; Lee, Byoung-Kuk ; Choi, Gwang-Bo ; Yoo, Dong-Wook ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 527~534
DOI : 10.5370/JEET.2011.6.4.527
In the present paper, the characteristics of Mega-Flux
, amorphous and ferrite cores are compared to the inductor of buck-boost converters for Hybrid Electric Vehicles. Core losses are analyzed at the condition of 10 kHz sine wave excitations, and permeability fluctuations vs. temperature and magnetizing force will be analyzed and discussed. Under the specifications of the buck-boost converter for 20 kW THS-II, the power inductor will be designed with Mega-Flux
, and informative simulation results will be provided with respect to dc bias characteristics, core and copper losses.
Measurement of III-V Compound Semiconductor Characteristics using the Contactless Electroreflectance Method
Yu, Jae-In ; Choi, Soon-Don ; Chang, Ho-Gyeong ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 535~538
DOI : 10.5370/JEET.2011.6.4.535
The electromodulation methods of photoreflectanceand the related technique of contactless electroreflectance(CER) are valuable tools in the evaluation of important device parameters for structures such as heterojunction bipolar transistors, pseudomorphic high electron mobility transistors, and quantum dots(QDs). CER is a very general principle of experimental physics. Instead of measuring the optical reflectance of the material, the derivative with respect to a modulating electric field is evaluated. This procedure generates sharp, differential-like spectra in the region of interband (intersubband) transitions. We conduct electric-optical studies of both GaAs layers and InAs selfassembled QDs grown by molecular beam epitaxy. Strong GaAsbandgap energy is measured in both structures. In the case of lnAs monolayers in GaAs matrices, the strong GaAsbandgap energy is caused by the lateral quantum confinement.
Effect of oxygen on the threshold voltage of a-IGZO TFT
Chong, Eu-Gene ; Chun, Yoon-Soo ; Kim, Seung-Han ; Lee, Sang-Yeol ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 539~542
DOI : 10.5370/JEET.2011.6.4.539
Thin-film transistors (TFTs) are fabricated using an amorphous indium gallium zinc oxide (a-IGZO) channel layer by rf-magnetron sputtering. Oxygen partial pressure significantly changed the transfer characteristics of a-IGZO TFTs. Measurements performed on a-IGZO TFT show the change of threshold voltage in the transistor channel layer and electrical properties with varying
ratios. The device performance is significantly affected by adjusting the
ratio. This ratio is closely related with the modulation generation by reducing the localized trapping carriers and defect centers at the interface or in the channel layer.
A Study on Optimum Spark Plasma Sintering Conditions for Conductive SiC-ZrB
Lee, Jung-Hoon ; Ju, Jin-Young ; Kim, Cheol-Ho ; Shin, Yong-Deok ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 543~550
DOI : 10.5370/JEET.2011.6.4.543
composites were produced by subjecting a 40:60 (vol%) mixture of zirconium diboride (ZrB2) powder and
-silicon carbide (SiC) matrix to spark plasma sintering (SPS). Sintering was carried out for 5 min in an argon atmosphere at a uniaxial pressure and temperature of 50 MPa and
, respectively. The composite sintered at a heating speed of
/min and an on/off pulse sequence of 12:2 was denoted as SZ12L. Composites SZ12H, SZ48H, and SZ10H were obtained by sintering at a heating speed of
/min and at on/off pulse sequences of 12:2, 48:8, and 10:9, respectively. The physical, electrical, and mechanical properties of the SiC-
composites were examined and thermal image analysis of the composites was performed. The apparent porosities of SZ12L, SZ12H, SZ48H, and SZ10H were 13.35%, 0.60%, 12.28%, and 9.75%, respectively. At room temperature, SZ12L had the lowest flexural strength (286.90 MPa), whereas SZ12H had the highest flexural strength (1011.34 MPa). Between room temperature and
, the SiC-
composites had a positive temperature coefficient of resistance (PTCR) and linear V-I characteristics. SZ12H had the lowest PTCR and highest electrical resistivity among all the composites. The optimum SPS conditions for the production of energy-friendly SiC-
composites are as follows: 1) an argon atmosphere, 2) a constant pressure of 50 MPa throughout the sintering process, 3) an on/off pulse sequence of 12:2 (pulse duration: 2.78 ms), and 4) a final sintering temperature of
at a speed of
/min and sintering for 5 min at
Design of the Crab label tag with a loop matching feed and a modified dipole structure at 900 MHz
Choi, Eui-Sun ; Lee, Hak-Yong ; Lee, Jin-Seong ; Lee, Kyoung-Hwan ; Lee, Sa-Won ; Lee, Young-Hie ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 551~555
DOI : 10.5370/JEET.2011.6.4.551
The Crab label tag with a loop matching feed and a modified dipole antenna structure was proposed. The antenna impedance is conjugated easily to a radio frequency identification IC chip impedance by a loop matching feed. The reading range of the crab structure tag is 0.9-1.0 m from the upper side of the formula milk can lid. The fabricated label tag size is
. The operating frequency at -3 dB return loss is 861.0-929.0 MHz, and the maximum reading range at the anechoic chamber is 1.5 m.
Investigation on the Electrical Discharge Characteristics of a Unipolar Corona-Wire Aerosol Charger
Intra, Panich ; Yawootti, Artit ; Vinitketkumnuen, Usanee ; Tippayawong, Nakorn ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 556~562
DOI : 10.5370/JEET.2011.6.4.556
In the present study, a simple corona-wire charger for unipolar diffusion charging of aerosol particles is designed, constructed, and characterized. Experimental characterizations of the electrostatic discharge in terms of current-voltage relationships of positive and negative coronas of the corona-wire charger are also presented and discussed. The charging current and ion concentration in the charging zone increased monotonically with corona voltage. The negative corona showed higher current than the positive corona. At the same corona voltages, the current in the discharge zone is about 600 times larger than the charging current. The ion number concentrations ranged within approximately
in the discharge and charging zones, respectively. A numerical model is used to predict the behavior of the electric potential lines. Numerical results of ion penetration through the inner electrode are in good agreement with the experimental results.
GPS Integrity Monitoring Method Using Auxiliary Nonlinear Filters with Log Likelihood Ratio Test Approach
Ahn, Jong-Sun ; Rosihan, Rosihan ; Won, Dae-Hee ; Lee, Young-Jae ; Nam, Gi-Wook ; Heo, Moon-Beom ; Sung, Sang-Kyung ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 563~572
DOI : 10.5370/JEET.2011.6.4.563
Reliability is an essential factor in a navigation system. Therefore, an integrity monitoring system is considered one of the most important parts in an avionic navigation system. A fault due to systematic malfunctioning definitely requires integrity reinforcement through systematic analysis. In this paper, we propose a method to detect faults of the GPS signal by using a distributed nonlinear filter based probability test. In order to detect faults, consistency is examined through a likelihood ratio between the main and auxiliary particle filters (PFs). Specifically, the main PF which includes all the measurements and the auxiliary PFs which only do partial measurements are used in the process of consistency testing. Through GPS measurement and the application of the autonomous integrity monitoring system, the current study illustrates the performance of the proposed fault detection algorithm.
High-Performance Korean Morphological Analyzer Using the MapReduce Framework on the GPU
Cho, Shi-Won ; Lee, Dong-Wook ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 573~579
DOI : 10.5370/JEET.2011.6.4.573
To meet the scalability and performance requirements of data analyses, which often involve voluminous data, efficient parallel or concurrent algorithms and frameworks are essential. We present a high-performance Korean morphological analyzer which employs the MapReduce framework on the graphics processing unit (GPU). MapReduce is a programming framework introduced by Google to aid the development of web search applications on a large number of central processing units (CPUs). GPUs are designed as a special-purpose co-processor. Their programming interfaces are typically formulated for graphics applications. Compared to CPUs, GPUs have greater computation power and memory bandwidth; however, GPUs are more difficult to program because of the design of their architectures. The performance of the Korean morphological analyzer using the MapReduce framework on the GPU is evaluated in comparison with the CPU-based model. The proposed Korean Morphological analyzer shows promising scalable performance on distributed computing with the GPU.
Accurate Corner Detection using 4-directional Edge Labeling and Corner Positioning Templates
Park, Eun-Jin ; Choi, Doo-Hyun ;
Journal of Electrical Engineering and Technology, volume 6, issue 4, 2011, Pages 580~584
DOI : 10.5370/JEET.2011.6.4.580
Corner positioning templates are proposed in order to detect the accurate positions of corners that are extracted using 4-directional edge labeling. Top-down and bottom-up directional labeling are used to label the edge segments with four kinds of labels according to their directions. The points whose labels have changed are then determined as corners. The exact positions of the missing corners due to the disconnected edges are detected through the corner positioning templates that are determined according to the labels of start-points and end-points after the two-pass edge labeling. Experiment results show that the proposed method can detect the exact positions of the real corners.