• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.1988-1994
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• 2014

In a single-phase grid-connected power system consisting of a DC/DC converter and a DC/AC converter, the current drawn from renewable energy sources has a tendency to be pulsated and contains second-order frequency ripple components, which results in several drawback such as a power harvesting loss and a shortening of the energy source's life. This paper presents a new second-order harmonic current reduction scheme with a fast dc-link voltage loop for two-stage dc-dc-ac grid connected systems. In the frequency domain, an adequate control design is performed based on the small signal transfer function of a two-stage dc-dc-ac converter. To verify the effectiveness of proposed control algorithm, a 1 kW hardware prototype has been built and experimental results are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1005-1008
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• 2001

This paper presents average current-mode control AC/DC ZVT(Zero Voltage Transition) Boost Converter. This boost converter perceives feed forward signal of input and feedback signal of output for average current-mode control proposed converter employs active-clamp method for ZVT. This converter gives the good PFC(Power Factor Correction), low line current hormonic distortions and tight output voltage regulations. This converter also has a high efficiency by active-clamp method. The principle of operation, feature, and design considerations are illustrated and verified through the experiment with a 150W, 120kHz prototype converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.385-387
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• 1997

This paper deals with the relationships between discharge current wave form and the structure of AC PDP cells. The Paschen minimum can be found in the range of $200{\sim}300\;torr$ under the condition of electrode width of $300{\mu}m$ and $100{\mu}m$ electrode gap. Furthermore, the charge current does not vary with the gas pressure, whereas the time delay in the discharge inception voltage decreased both peak and r.m.s discharge current increase with gas pressure and electrode width.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1343-1344
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• 2008

This paper analyses current densities induced inside a worker using AC arc welder when he wears a protective cloth. Applying the boundary element method, we calculate current densities induced in organs inside a worker in case he was located at 1[cm], 15[cm], 20[cm] far from a power cable of AC arc welder. As results of study, we find a maximum current density induced in all organs may be lower than 10[$mA/cm^2$] if he wears a protective cloth. We also know high permeability materials can lower current density more than high conductivity materials.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.112-115
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• 2002

Previous AC/DC PFC Boost Converter perceives feed forward signal of input and feedback signal of output for average current-mode control. Previous Boost Converter, the quantity of input current will be decreased by the decrease of output current in light load, and also power factor comes to be decreased. Also the efficiency of converter will be decreased by the decrease of power factor. The proposed converter presents the good PFC(Power Factor Correction), low line current hormonic distortions and tight output voltage regulations using non-dissipative snubber. The proposed converter also has a high efficiency by non-dissipative snubber circuit. To show the superiority of this converter is verified through the experiment with a 640W, 100kHz prototype converter.

• 전기학회논문지
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• 제59권7호
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• pp.1265-1271
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• 2010

Power cable of an AC arc welder can surround a body of worker at the moment of welding. Applying the boundary element method, we calculated current densities induced in organs inside a worker to study the magnetic field reduction characteristics of shielding wear materials. We knew shielding wear with high permeability materials lowers current density more than high conductivity materials. We also found current density was lowest when high permeability materials were inside high conductivity materials in double layer shielding wear.

• 전기학회논문지
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• 제66권3호
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• pp.522-532
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• 2017

In this paper, a new method of SVPWM implementation for 3-Phase 3-Leg 3-Level AC/DC converter known as the Vienna converter is proposed. Also the performances of PI and PR controller used in AC input current controller are compared. To verify the proposed method, PSIM, a power electronics simulation program, is utilized. The performances of the proposed new method and the two existing methods are compared through simulation and experiment. Also PI and PR controller in AC input current controller are compared through 10[kW] Vienna converter system.

• Journal of Power Electronics
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• 제2권4호
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• pp.297-304
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• 2002

The paper identifies a severe form of core saturation instability in a DC/AC interaction system. It then seeks solutions to the problem by HVDC control means. This is achieved by a proper design of the Voltage Dependent Current Order Limiter (VDCOL), the Current Regulate. and Timing Pulse generator. Supplementary control loops have also been introduced to result in a satisfactory performance as compared to that obtained one with the use of uncharacteristic harmonic filter on the AC side. All the options have been demonstrated through recovery performance of the DC link in response to both 1-phase and 3-phase 5 cycle faults on both rectifier and inverter commutating buses.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.704-711
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• 2013

Data center is an information hub and resource for information-centric society. Since data center houses hundreds to ten thousands servers, networking and communication equipment, and supporting systems energy saving is one of the hottest issues for green data center. Among several solutions for green data center this paper introduces higher voltage direct current (DC) power feeding system. Contrary to legacy alternating current (AC) power feeding system equipped with Uninterruptible Power Supply (UPS), higher voltage DC power feeding system is reported to be a more energy efficient and reliable solution for green data center thanks to less AC/DC and DC/AC conversions. Main focus of this paper is on reliability issue for reliable and continuous operation of higher voltage DC power feeding system. We present different types of configuration of the power feeding systems according to the level of reliability. We analyze the reliability of the power feeding systems based on M/M/1/N+1/N+1 queueing model. Operation of the power feeding system in case of failure is also presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1410-1411
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• 2007

This paper analyses current densities induced inside a worker using AC arc welder. Applying the boundary element method, we calculate current densities induced in organs inside a worker in case he was located at 1[cm], 3[cm], 5[cm], 10[cm], 15[cm], 20[cm] far from a power cable of AC arc welder. As results of study, we find a maximum current density induces at a heart surface and may be higher than 10[$mA/m^2$] of ICNIRP guideline if he works within 15[cm] from a power cable.