• Structural Engineering and Mechanics
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• v.10 no.3
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• pp.245-262
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• 2000

The objective of this study is to analyze the deformational characteristics of a high-vacuum insulation panel that is evacuated to eliminate significant gas-phase conductance through its thickness. The panel is composed of a metal envelope and low thermal conductance spacers. The problem is very challenging because several nonlinearities are involved concurrently. Not only are various finite element models such as triangular, rectangular, beam and circular plate models used to simulate the panel, but also several finite element programs are used to solve the problem based on the characteristics of the finite element model. The numerical results indicate that the effect of the diameter of the spacer on the vertical deformation of the plate panel is negligibly small. The parameter that mainly influences the maximum sag is the spacing between the spacers. The maximum vertical deformation of the panel can be predicted for a practical range of the spacing between the spacers and the thickness of the plate. Compared with the numerical results obtained by the finite element models and the experimental tests, they have a good agreement. The results are represented in both tabular and graphical forms. In order to make the results useful, a curve fitting technique has been applied to predict the maximum deformation of the panel with various parameters. Moreover, the panel was suggested to be a "smart" structure based on thermal effect.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.12 no.1
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• pp.42-46
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• 2012

With the development of industry, more large-scale non-linear loads are added to existing power systems and they cause the serious power quality (PQ) problems to the nearby sensitive installations more and more. To protect the important loads and mitigate the impact of PQ disturbances on them, various compensating devices are installed. One of the most important control skills used in the compensating equipment at the load side is how fast they can recognize or detect the discontinuous abnormal PQ events from the normal voltage signal. This paper deals with two estimation methods for the fast detection and tracking of general PQ disturbances: Teager Energy Operator (TEO), which is a non-linear operator and used for a short time energy calculation, and Kalman Filter (KF), which is one of the most universally used estimation techniques. And it is also shown how to apply the TEO and the KF to detect the PQ disturbances such as voltage sag, swell, interruption, harmonics and voltage fluctuation.

• Journal of Power Electronics
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• v.13 no.5
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• pp.884-895
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• 2013

In this paper, the Fourier-based PLL (Phase-locked Loop) is introduced with a new structure, capable of selective harmonic detection in single and three-phase systems. The application of the FB-PLL to harmonic detection is discussed and a new model applicable to three-phase systems is introduced. An analysis of the convergence of the FB-PLL based on a linear model is presented. Simulation and experimental results are included for performance analysis and to support the theoretical development. The decomposition of an input signal in its harmonic components using the Fourier theory is based on previous knowledge of the signal fundamental frequency, which cannot be easily implemented with input signals with varying frequencies or subjected to phase-angle jumps. In this scenario, the main contribution of this paper is the association of a phase-locked loop system, with a harmonic decomposition and reconstruction method, based on the well-established Fourier theory, to allow for the tracking of the fundamental component and desired harmonics from distorted input signals with a varying frequency, amplitude and phase-angle. The application of the proposed technique in three-phase systems is supported by results obtained under unbalanced and voltage sag conditions.

• Proceedings of the KIEE Conference
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• summer
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• pp.351-353
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• 2004

In recent years, customers and power supplies are interested in power quality. Demands of customers are change from standard quality of distribution power system to various high quality of distribution power system. so, it is necessary to apply power quality compensator. in our project, we develop the UPQC(Unfied Power Quality Compensator of 45kVA which compensates power factor and voltage sag, interruption. it is very frequently occurred power quality $problems^{[1-3]}$ As a series and shunt compensator, UPQC consists of two inverters with common do link capacitor bank. It compensates the current quality in the shunt part and the voltage quality in the series part. In this paper, we present the design and control algorithm for 4SkVA UPQC system. As a control algorithm is implemented by digital controller, we consider sample-and-hold of signals. In this simulation, we use EMTDC/PSCAD V3.0 software which can simulate instantaneous voltage and current.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.180-183
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• 2000

The Battery Energy Storage System(BESS) has lots of advantages such as load levelling, quick response emergency power(spinning reserve), frequency and voltage control, improvement of reliability, and deferred generation and transmission construction. The economic feasibility requires justification from the customer side of meter to promoting the dissemination of BESS nationally. In this paper, we proposed the economic assessment model of customer owned Battery Energy Storage System(BESS) which is complemented and improved the existing model. The proposed model is applied to the typical customer type(light-industrial commercial, and residential) which are taken from the statistical analysis on the load profile survey of Korea Electric Power COmpany (KEPCO). The economic assessment performed for each customer type to justifying their economic feasibility of BESS installation from the economic measures such as payback period, overall benefits, ROI, and ROR. The results of this paper are useful to the customer investment decision making and the national energy policy & strategy.

• Journal of the Korean Ceramic Society
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• v.38 no.6
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• pp.545-550
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• 2001

본 연구에서는 분사연소합성(SCS)을 위한 기초단계로서 용액연소합성에 대한 거동을 살펴보고자 알루미나 합성을 모델로 하였으며 이를 위해 전구체에 대한 열분해거동, 그리고 각 온도에서의 평형종 분압 계산 및 합성과정을 조사하였다. 각각의 열중량 분석(TGA) 결과 산화제와 환원제(연료)의 열분해 이력이 서로 다르게 나타났으며, 열역학 응용 프로그램인 ChemSag에 의한 평형종 분압의 계산에서 연소속도를 저하시킬 수 있는 $CO_2$와 수증기 가스 분압이 상당부분 존재하였다. 산화제/환원제 혼합물의 열분석(DTA/TG) 결과 산화제와 환원제의 열분해 거동의 차이, 그리고 매우 작은 시료의 양으로 인해 263$^{\circ}C$에서 발열피크가 매우 작게 나타났다. 열분석 시료에 비해 발열 에너지를 높이기 위해 산화제와 환원제 혼합 전구체를 비이커에서 증기압을 조절하며 가열시켜 본 결과 27$0^{\circ}C$에서 $\alpha$-Al$_2$O$_3$생성물을 얻을 수 있었다. 따라서 분사연소합성 반응을 통해 세라믹 원료를 합성하기 위해서는 연소과정 중 열분해 거동과 평형종의 분압을 고려하여야 한다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.134-139
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• 2013

When the accident occurred in power distribution system, it needs to control efficiently the fault current according to the fault angle and location. The flux-lock type superconducting fault current limiters (SFCL) can quickly limit when the short circuit accidents occurred and be made the resistance after the fault current. The flux-lock type SFCL has a single triggering element, detects and limits the fault current at the same time regardless of the size of the fault current. However, it has a disadvantage that broken the superconductor element. If the flux-lock type SFCL has separated structure of the triggering element and the limiting element, when large fault current occurs, it can reduce the burden of power and control fault current to adjust impedance. In this paper, this system is composed by triggering element and limiting element to analyze operation of limiting current. When the fault current occurs, we analyzed the limiting and operating current characteristics of the two triggering current level, and the compensation characteristics of bus-voltage sag according to the fault angle and location.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1315-1322
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• 2015

This paper proposes an active islanding detection method for the BESS (Battery Energy Storage System) with 3-phase inverter which is connected to the AC grid. The proposed method adopts the DDSRF (Decoupled Double Synchronous Reference Frame) PLL (Phase Locked-Loop) so that the independent control of positive-sequence and negative-sequence current is successfully carried out using the detected phase angle information. The islanding state can be detected by sensing the variation of negative-sequence voltage at the PCC (Point of Common Connection) due to the injection of 2-3% negative-sequence current from the BESS. The proposed method provides a secure and rapid detection under the variation of negative-sequence voltage due to the sag and swell. The feasibility of proposed method was verified by computer simulations with PSCAD/EMTDC and experimental analyses with 5kW hardware prototype for the benchmark circuit of islanding detection suggested by IEEE 1547 and UL1741. The proposed method would be applicable for the secure detection of islanding state in the grid-tied Microgrid.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1297-1305
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• 2015

This paper proposes a power feedforward technique for the performance improvement of DC-link voltage control in the dynamic voltage restorer (DVR). The DC-link Voltage is able to be unstable for an instant owing to any change in the load and voltage sag. The distortion of the DC-link voltage leads to the negative influence on the performance of DVR. To mitigate the distortion of the DC-link voltage, the power feedforward component is calculated by the load power and the grid voltage, and then it is added to the reference current of the conventional DC-link voltage controller. By including output power feedforward component on the DC-link controller, the DC-link voltage can settle down more quickly than when the conventional DC-link voltage controller applied. The proposed technique was validated through the simulation and experimental results.

• Journal of the Korean Society of Costume
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• v.53 no.7
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• pp.47-55
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• 2003

The purpose of this study was to provide information on how to improve the comfort and fit of womens swimsuits through analysis of the present wearing conditions and users complaints. In order to compile the information about dissatisfaction with the appropriateness of the fit of breast cap for swimsuits, a questionnaire was administered to 364 females (over 20 years old under 60 years old). The contents of the questionnaire consisted of questions such as the reasons for selecting to wear breast cap for swimsuits or not, size of brassiere and swimsuits, dissatisfaction with material, dissatisfaction with function of breast cap. The collected data were analyzed using the descriptive statistics value of frequencies and percentile value, mean, and so on by means of the SPSS WIN.10.0 program. The differences among age groups, body type groups by rohrer index, cup size and so on were compared using the chi-square test. Results of the survey responses about swimsuits breast caps: Most women have worn swimsuits with caps. According to the results, women who are older or overweight, or have larger breasts, or breasts which sag, as well as those who have had the experience of giving birth responded that they feel uncomfortable because of the slope of their breasts. Concerning complaints about the caps, 61% of respondents complained about the cap size and lack of correspondence with breast size, 56.8% expressed concern about the cap gap. There is significant difference in wearing reason of breast caps forswimsuits among age groups and many kinds of groups.