• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.347-349
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• 2005

본 논문에서는 가정용으로 사용하는 3kW 무변압기형 태양광 발전용 인버터에 대하여 설명한다. 지금까지 국내에서 생산되고 있는 태양광 발전용 인버터는 외산을 제외하고는 상용 주파수의 변압기를 장착한 형태로서 계통에 안정적이고 제어가 간단하지만 부피가 크고 무게가 무겁고, 또한 태양전지의 입력 전압 범위가 좁다는 단점을 가지고 있다. 이를 개선하기 위해서 승압형 DC-DC 컨버터를 추가하여, 변압기 없이 컨버터와 인버터로 구성된 시스템을 소개하고 구성 및 특성에 대해서 알아본다.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.102-105
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• 2005

For transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the contactless power supply system. However, the high frequency series resonant converter has the disadvantages such as the low efficiency, the high voltage gain characteristics and deviation of the phase angle in the overall load range. To improve this disadvantage, In this paper, the characteristics of the high efficiency and unit voltage gain as well as in phase are revealed in the proposed three-level LCLC ( Inductor - Capacitor - Inductor -Capacitor)resonant converter. The results are verified on the simulation based on the theoretical analysis and the 4kW experimental prototype.

• Nuclear Engineering and Technology
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• v.53 no.12
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• pp.4022-4032
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• 2021

In this study, machine learning (ML) techniques were used to model surveillance test data of nuclear power plants from an international database of the ASTM E10.02 committee. Regression modeling was conducted using various techniques, including Cubist, XGBoost, and a support vector machine. The root mean square deviation of each ML model for the baseline dataset was less than that of the ASTM E900-15 nonlinear regression model. With respect to the interpolation, the ML methods provided excellent predictions with relatively few computations when applied to the given data range. The effect of the explanatory variables on the transition temperature shift (TTS) for the ML methods was analyzed, and the trends were slightly different from those for the ASTM E900-15 model. ML methods showed some weakness in the extrapolation of the fluence in comparison to the ASTM E900-15, while the Cubist method achieved an extrapolation to a certain extent. To achieve a more reliable prediction of the TTS, it was confirmed that advanced techniques should be considered for extrapolation when applying ML modeling.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.9-10
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• 2014

최근 신재생에너지 및 전기자동차, 통신 IT 서버 전원 및 가전기기 등의 발전에 따라 고 전력밀도(High Power Density), 고 응답(Fast Transient Response) 및 고정밀(Tight Regulation) 출력제어를 위한 다 출력 절연형 DC/DC 컨버터가 개발 및 연구되고 있다. 본 논문에서는 개별적인 정밀제어를 요구하는 다 출력 DC-DC 컨버터에 대한 내용으로 위상천이(Phase-shift) DC-DC 컨버터와 LLC 공진컨버터 제어개념을 하나의 주회로를 사용하여 위상천이제어(Phase-shifted Modulation, PM)와 가변주파수제어(Variable Frequency Modulation, FM)를 통해서 개별적으로 정밀 제어할 수 있는 하이브리드 다 출력 3레벨 DC-DC 컨버터에 관한 내용이다.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.10
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• pp.35-41
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• 1992

Ultra-thin silicon nitride films were fabricated with ECR(Electron cyclotron Resonance) nitrogen plasma at room temperature. Film thickness was about 50$\AA$ after nitridation for 1min at microwave power of 1000W, RF power of 500W, and NS12T pressure of ${\times}10^{-3}$ torr. 50$\AA$ fo nitride film was grown within 1 min and no appreciable growth occured thereafter. Dielectric breakdown strength and leakage current density in Al/SiN/Si structure were measured to be about 7-11 MV/cm and ${\times}10^{-10}~5{\times}10^{-10}A/cm^{2}$, respectively. Observed linear relationship in 1n(J/E)-vs-E$^{1/2}$ and no polarity-dependence of the leakage current indicated that the Poole-Frenkel emission is mainly responsible for the conduction in this nitrided silicon films.

• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.600-602
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• 1995

The paper presents neural network control techniques for load frequency control of two area power system. Using learning algorithm of error back propagation after learning accept input on the optimal control $e_{i}$, $\dot{e}_{i}$, and $u_{i}$ frequency characteristic and tie-line load flow characteristic investigated dynamic. From result simulation, frequency deviation and tie-line load flow deviation have reduction remarkable.

• Nuclear Engineering and Technology
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• v.53 no.10
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• pp.3127-3132
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• 2021

Feasibility study of burn-up analysis and monitoring using delayed fast neutrons was investigated at Missouri University of Science and Technology Reactor (MSTR). Burnt and fresh fuel elements were used to collect delayed fast neutron data for different power levels. Total reactivity varied depending on the burn-up rate of fuel elements for each core configuration. The regulating rod worth was 2.07E-04 𝚫k/k/in and 1.95E-04 𝚫k/k/in for T121 and T122 core configurations at 11 inch, respectively. Delayed fast neutron spectrum of F1 (burnt) and F16 (fresh) fuel elements were analyzed further, and a strong correlation was observed between delayed fast neutron emission and burn-up. According to the analyzed peaks in burnt and fresh fuels, reactor power dependency was observed and it was determined that delayed neutron provided more reliable results at reactor powers of 50 kW and above.

• Korean Journal of Mathematics
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• v.31 no.4
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• pp.505-519
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• 2023

Let G = (V, E) be a graph. A subset S of V is called a dominating set of G if every vertex not in S is adjacent to some vertex in S. The domination number γ(G) of G is the minimum cardinality taken over all dominating sets of G. A dominating set S is called a connected dominating set if the subgraph induced by S is connected. The minimum cardinality taken over all connected dominating sets of G is called the connected domination number of G, and is denoted by γ_c(G). In this paper, we investigate the Nordhaus-Gaddum type results for the connected domination number and its derived graphs like line graph, subdivision graph, power graph, block graph and total graph, and characterize the extremal graphs.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.11
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• pp.532-537
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• 2006

Lightning induced faults accounts for more than 66% at the transmission lines of KEPCO. The lightning causes damages to power system equipments including transmission line, the blackout of electricity and the electro-magnetic interference. Because of this reason, we need the real time lightning information for the optimal operation of power system. And, it is required to obtain and accumulate the lightning current parameters for the insulation design. In 2005, KEPRI constructed a lightning detection network, the KLDNet (i.e. Kepco Lightning Detection & Information System) and launched a lightning information service for KEPCO customers. It is intended to provide data service on the operation of transmission lines and collect lightning-related data, which is the most important factor regulating power system design and operation. The new system will replace LPATS, the old detection system, which has been operating since 1995 and is rapidly failing in terms of both detection performance and location accuracy. The purpose of this paper is to explain the work performed and the results of that work in performing a site survey of several locations. The purpose of the site survey is to find locations acceptable for the installation of a lightning location receiver in support of a Lightning detection system(LDS). A restriction was placed on the surveyed locations, as they must belong to the Korea Electric Power Company. This requirement was made to facilitate the communication needs of the LDS network. Total of 15 sites were evaluated as possible LDS sensor sites. Some of the sites were rejected for physical reasons and therefore no electrical testing was performed. Of the 15 sites, total of 10 sites were considered acceptable and 5 sites were rejected for various reason. In this paper, we would like to explain the site survey and detection efficiency for LDS.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1550-1551
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• 2006

An L-band linear accelerator system for e-beam sterilization is under design for bio-technology application. The klystron-modulator system as RF microwave source has an important role as major components to offer the system reliability for long time steady state operation. A PFN line type pulse generator with a peak power of 71.5-MW, $7{\mu}s$, 285 pps is required to drive a high-power klystron. The high power pulse transformer has a function of transferring pulse energy from a pulsed power source to a high power load. The pulse transformer producing a pulse with a peak voltage of 275 kV is required to produce 30-MW peak and 60 kW average RF output power at the frequency of 1.3-GHz. We have designed the high power pulse transformer with 1:13 step-up ratio. The peak and average power capability is 71.5-MW (275 kV, 260 A at load side with $7{\mu}s$ pulse width) and 130 kW, respectively. In this paper, we present a system overview and initial design results of the high power pulse transformer.