• 전력전자학회:학술대회논문집
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• 전력전자학회 1996년도 창립기념 전력전자학술발표회 논문집
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• pp.117-120
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• 1996

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. In this paper, the authors propose a DC-DC boost converter of high power by partial resonant switch method (PRSM). The switching devices in a proposed circuit are operated with soft switching and the control technique of those is simplified for switch to drive in constant duty cycle. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. Also the circuit has a merit which is taken to increase of efficiency, as it makes to a regeneration at input source of accumulated energy in snubber condenser without loss of snubber in conventional circuit. The result is that the switching loss is very low and the efficiency of system is high. The proposed converter is deemed the most suitable for high power applications where the power switching devices are used.

• 한국압력기기공학회 논문집
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• 제15권1호
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• pp.33-39
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• 2019

An 1,500MW advanced power reactor required the standard design approval by a Korean regulatory body in 2014. The reactor has been designed to have a 4-train independent safety concept and a passive auxiliary feedwater system (PAFS). The full power risk or core damage frequency (CDF) of 1,500MW advanced power reactor has been reduced more than that of APR1400. However, the risk during the low power and shutdown (LPSD) operation should be reduced because CDF of LPSD is about 4.7 times higher than that of internal full power. The purpose of paper is to analysis design alternatives to reduce risk during the LPSD. This paper suggests design alternatives to reduce risk and presents sensitivity analysis results.

• 동력기계공학회지
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• 제18권6호
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• pp.51-57
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• 2014

High pressure common rail injection technology has revolutionized the diesel industry. Over the last decade it has allowed engine builders to run higher injection pressures as much as above 1,300bar in order to increase engine efficiency, while reducing emissions. This common rail system has low pressure circuit which is consist of low pressure pump, cascade overflow valve and flow metering unit. The low pressure pump's purpose is to feed fuel oil to the high pressure pump. The cascade overflow valve keeps pressure in front of the metering unit constant and provides lubrication for the high pressure pump. The metering unit, known as the MPROP or fuel pressure regulator, regulates the maximum flow rate delivers to the rail. In this paper, we have investigated the performance characteristics of each components and total low pressure circuit of common rail system.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권5호
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• pp.235-240
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• 2000

A low cost lighting system for line-scan cameras has been developed with 3-phase power. When exposure time of line-scan camera is shorter than fluctuation period of illumination, the average gray value of each acquired 1-D image varies. Detecting defects on the objects's surface under such illuminating environment is very difficult. The proposed lighting system is composed of low-cost fluorescent lights based on 3-phase power. The specially designed lighting pack and the properly selected lighting position enable to get the rippleless lighting. The principle of the proposed lighting system has been explained analytically. The lighting system has been tested for fabric inspection with line-scan camera and it's efficacy has been proved.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.939-941
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• 2003

High Speed permanent magnet machines are currently being developed for a number of applications including gas turbine power plants, air conditioning systems, machine tools, gas pumps, high performance vacuum pumps, flywheel energy storage systems, aircraft fuel pumps, and so on. Using a high-speed machine eliminates the necessity of the mechanical gearbox and could certainly increase the system efficiency and reduce the total cost. In addition, a high-speed machine has the advantage of small dimension and low weight, i.e. low weight to power and volume to power ratio. This paper presents a review of some important applications (mostly still under development) where high-speed machines arc used, highlighting the advantages of the technology in each case.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.397-401
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• 1991

Low frequency oscillations have been observed in KEPCO system. This paper represents how to analyze the power system by using the AESOPS program and analyze the various factors affecting the damping characteristics of these oscillations in KEPCO system of 1986. The characteristics of load, the amount of power flow on the transmission line and the gain of exciter have a significant effects on the damping of the system while the governing system has only a minor one. With the Power System Stabilizers, the stability of the power system has been increased.

• 전기학회논문지P
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• 제65권3호
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• pp.178-182
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• 2016

FIDVR(Fault Induced Delayed Voltage Recovery) is a phenomenon that recovery of the system voltage level delays after the fault. Cause of FIDVR phenomenon is motor load characteristic about voltage and reactive power. In low voltage condition, the motor go to stall state that consume large amount of reactive power. As a result, the voltage recovery problem is that of repeated occurrences of sustained low voltage following faults on the system. In this paper, analysis the characteristics of the motor load. And using the korean power system actual data, perform a case studies to voltage delay recovery phenomenon alleviation method. Change of each parameters by analyzing the effect on system and selecting an influence parameter. In addition, dynamic characteristic analysis of the resulting difference in the proportion by the motor load in power systems, considering the effect on the voltage stability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1148-1150
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• 2003

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. To improved these, a large number of soft switching topologies included a resonant circuit has been prosed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose a high power factor and high efficiency DC-DC converter using single-pulse soft switching by partial resonant switching node. The switching devices in a prosed circuit are operated with soft switching by the partial resonant method, that is, Partial Resonant Switch Mode Power Converter. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. Also the proposed converter is deemed the most suitable for high power applications where the power switching devices are used. Some simulative results on computer results are included to confirm the validity of the analytical results.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권10호
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• pp.501-507
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• 2001

In this paper, new high-efficiency zero voltage switching (ZVS) AC-DC boost converter is proposed to achieve power factor correction by simplifing energy recovery circuit. A lot of high power factor correction circuits have been proposed and applied to increase input power factor and efficiency. Most of these circuits may obtain unity power factor and achieve sinusoidal current waveform with zero voltage or/and zero current switching. However, it is difficult for them to obtain low cost, small size, low weight, and low noise. The topology proposed to improve these problems can compact the devices in circuit and can achieve high efficiency ZVS AC-DC boost converter. Simulation and experimental results show that this topology is capable of obtaining high power factor and increasing the efficiency of the system.

• 전력전자학회논문지
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• 제16권2호
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• pp.182-190
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• 2011

본 논문은 계통 전압 사고 상황에서 계통 연계형 풍력 발전 시스템이 만족시켜줘야 할 LVRT(Low Voltage Ride Through) 제어 전략을 제안한다. LVRT 규정은 계통 전압 사고 시 풍력 발전 시스템이 지켜야 할 부분들을 전압 감소율과 사고 시간에 대해 나타내고 있다. 특히 전압 감소율이 10% 이상일 경우에는 풍력 발전 시스템은 규정된 무효 전류를 전력 계통에 제공하여 계통 전압 확보에 이바지해야 한다. 본 논문에서의 LVRT 규정은 세계적으로 가장 엄격한 규정인, 독일 계통 연계 규정(German Grid Code)을 기준으로 하고 풀 스케일(Full-scale) 가변 속도 전력 변환 시스템을 고려하여 제어 전략을 수립한다. 본 LVRT 제어 전략은 계통 사고 시 LVRT 규정을 모두 만족시킴과 동시에 직류단 전압 제어의 추가적인 알고리즘으로 직류단 전압의 제어를 통하여 전체 풍력 발전 시스템의 전력 균형을 기할 수 있다. 3상 전압 지락 사고의 경우 계통으로의 전력 제어가 불가능하여 계통 측 컨버터가직류단 전압을 제어할 수 없으므로, 전력 제어의 기능을 발전기 측 인버터로 이행 시켜 상황에 따라 유연한 직류단 전압 제어가 가능함을 보였다. 시뮬레이션과 실험을 통해 LVRT 제어 전략의 타당성을 검증하였다.