• 동력기계공학회지
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• 제15권1호
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• pp.5-10
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• 2011

The spatial fuel vapor distribution of the homogeneous charge by a 6-hole injector was examined in a optically accessed single cylinder direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF (Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played a little more effective role in the spatial fuel vapor distribution than the swirl flow during the compression stroke at 10 mm and 2 mm planes under cylinder head gasket and the increased fuel injection pressure activated spatial distributions of the fuel vapor. In additions, richer mixtures were concentrated around the cylinder wall by the increase of the coolant temperature.

• Journal of Electrical Engineering and Technology
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• 제12권6호
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• pp.2208-2218
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• 2017

To resolve overload in a distribution system, a distribution system operator (DSO) often performs a load transfer using normally open tie points and switches in the distribution line. During this process, the distribution system is momentarily operated in closed-loop operation. A closed-loop current in the distribution system can cause a power failure due to excess breaking current in the circuit breakers and reclosers. Therefore, it is necessary to calculate the closed-loop current exactly. However, if there are a large number of distributed generation (DG) systems in the distribution system, such as energy storage systems (ESS), they might obstruct the closed-loop operation based on bidirectional power flow. For quick and precise operation of a closed-loop system, the ESS has to regulate the power generation while satisfying closed-loop operation in the worst cases. We propose a strategy for balanced power regulation of an ESS. Simulations were carried out using PSCAD/EMTDC, and the results were compared with calculation results.

• 조명전기설비학회논문지
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• 제13권4호
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• pp.127-133
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• 1999

본 논문은 배전계통에 전지전력저장시스템(Battery Energy Storage System: BESS)를 연계하여 운전하는 경우 BESS의 유.무효전력 제어에 대하여 연구하였다. BESS을 배전계통에 연계하는 경우, 이의 유.무효전력 출력을 제어함으로써 배전계통에 일정 전력을 공급, 첨두 부하를 삭감하고 전압을 보상할 수 있다. 본 논문에서는 배전계통과 전지전력저장시스템을 등가 모델링 하였고 전지전력저장시스템의 유.무효 전력제어를 위한 전력 조류 방정식을 제시하였다. 본 논문에서는 BESS의 유.무효전력을 제어하기 위하여 $P-\delta$와 Q-V 제어를 사용하였고 이를 입증하기 위하여 BESS의 유.무효전력 제어를 PSCAD/EMTDC 프로그램을 이용하여 시뮬레이션 하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.861-863
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• 2005

LMP based congestion management method is suggested as an effective tool, because network congestion can be handled by energy price. It is now being widely used in the North American Electricity Markets. Among them, FGR(Flow-gate rights) is considered to be appropriate for our system, as power flow through the congested line is unidirectional and congestion occurs in the known place. In the CBP market, hedging through transmission right is not necessary even though location pricing system is adopted, because there are no risks in the energy price. Rut, transmission rights should be adopted in the advanced market. Key issue when implementing FGR is how to decide transmission right issuance quantify. This paper deals with a method to decide transmission right issuance quantity by using power. Transfer Distribution Factor(PTDF).

• 조명전기설비학회논문지
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• 제23권2호
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• pp.53-61
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• 2009

현재의 배전계통의 전압은 변전소에서 단방향 조류를 고려하여 LCD에 의한 전압조정방법으로 ULTC 변압기의 탭을 변환하여 공급전압을 적정범위 내에서 유지되도록 운전하고 있다. 그러나 현재의 배전계통 운용은 소용량에서 대규모 용량에 이르기까지 다양한 용량의 PV 시스템이 배전계통에 연계되어 운전되는 것을 반영하지 못하고 있는 실정이다. 때문에 다수의 PV 시스템이 계통에 연계되어 양방향 조류가 발생하고 이로 인해 연계점의 전압변동이 발생하여도 이를 효과적으로 조정하지 못하여 계통의 전압이 적정범위 내에서 운용되지 못하는 경우가 발생할 수 있다. 따라서 본 논문에서는 다수 PV 시스템의 연계에 따른 양방향 조류의 발생을 고려하고 연계점의 전압변동에 따른 계통의 전압을 효과적으로 제어할 수 있도록 실시간 감시가 이루어지는 PV 시스템의 특징을 이용하고 기존의 LDC 전압조정방법을 개선하여 PV 시스템 연계 시에도 변전소에서 계통의 전압을 적정범위 내에서 조정할 수 있는 개선된 전압조정방법을 제안하였다.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1851-1859
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• 2022

Experimental research on flow characteristics of open natural circulation system was performed, to figure out the mechanism of the open natural circulation behaviors. The influence factors, such as the heating power, the inlet subcooled and the level of cooling tank on the flow characteristics of the system were examined. It was shown that within the scope of the experimental conditions, there are five flow types: single-phase stable flow, flash and geyser coexisting unstable flow, flash stable flow, flash unstable flow, and flash and boiling coexisting unstable flow. The geyser flow in flash and geyser coexisting unstable flow is different from classic geysers flow. The flow oscillation period and amplitude of the former are more regular, is a newly discovered flow pattern. By drawing the flow instability boundary diagram and sorting out the flow types, it is found that the two-phase unstable flow is mainly characterized by boiling and flash, which determine the behavior of open natural circulation respectively or jointly. Moreover, compared with full liquid level system, non-full liquid level system is more prone to boiling phenomenon, and the range of heat flux density and undercooling degree corresponding to unstable flow is larger.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부A
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• pp.211-213
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• 1998

This paper introduces the additional remote monitoring and remote setting functions needed to operate the distribution automation system effectively. we compare the additional functions with the old functions. The remote setting of minimum trip value of fault indicator is an example of additional function. It saves time and line-man's power. Also this paper describes the data transmission flow diagram for operation of distribution automation system using wireless communication method.

• 동력기계공학회지
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• 제13권3호
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• pp.27-32
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• 2009

Numerical analysis information of a complex discharge-passage will be very useful to improve hydrogen compression system. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including pressure and turbulence kinetic energy distribution of hydrogen gas from cylinder going to the chamber of a reciprocating compressor are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows pressure and turbulence kinetic energy are not distributed uniformly along the passage of the hydrogen compressing system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement should be done. Consequently, development of the better hydrogen compressing system will be achieved.

• 한국산학기술학회논문지
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• 제10권8호
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• pp.1802-1809
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• 2009

기존의 배전계통은 전원 측인 배전용변전소에서 부하 측인 수용가로 전력을 단 방향으로 공급하는 것이 일반적이지만, 태양광과 풍력 등과 같은 분산전원이 배전계통에 연계되는 경우에는 분산전원에서 발생하는 전력이 계통으로 공급되는 역 조류가 발생하여 기존의 시스템과 달리 양방향으로 전력이 공급되게 된다. 이러한 양방향 전력공급은 기존의 시스템에 악 영향을 끼칠 수 있는데, 배전선로에 설치되어 있는 보호협조기기에 심각한 문제점을 발생시킬 수 있다. 특히 기존의 구간 개폐기는 주 전원 측의 전력만 감지할 뿐, 분산전원 측의 역 조류 감지 및 보호를 하지 못해 오동작을 일으킬 가능성이 존재한다. 이러한 경우 분산전원의 단독 운전뿐만 아니라 배전계통과 분산전원의 비동기 투입에 의하여 배전계통에 악영향을 끼칠 수도 있다. 따라서 본 논문에서는 이에 대한 대책으로서 역 조류를 감지하는 구간 개폐기의 양방향 동작 알고리즘을 제시하고, 이에 대한 성능을 확인하기 위하여, 배전계통의 대표적인 해석 S/W인 PSCAD/EMTDC를 이용하여 시뮬레이션을 수행하였다. 또한 보호기기 모의시험 장치를 제작하여 하드웨어적인 시험 결과를 분석하여, 본 논문에서 제안한 구간개폐기의 양방향 동작 알고리즘에 대한 효용성과 타당성을 확인하였다.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1514-1524
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• 2019

Hydrogen-steam gas mixture may be injected into containment with flow regime varying both spatially and transiently due to wall effect and pressure difference between primary loop and containment in severe accidents induced by loss of coolant accident. Preliminary CFD analysis is conducted to gain information about the helium flow regime transition process from jet to buoyancy plume for forthcoming experimental study. Physical models of impinging jet and wall condensation are validated using separated effect experimental data, firstly. Then helium transportation is analyzed with the effect of jet momentum, buoyancy and wall cooling discussed. Result shows that helium distribution is totally dominated by impinging jet in the beginning, high concentration appears near gas source and wall where jet momentum is strong. With the jet weakening, stable light gas layer without recirculating eddy is established by buoyancy. Transient reversed helium distribution appears due to natural convection resulted from wall cooling, which delays the stratification. It is necessary to concern about hydrogen accumulation in lower space under the containment external cooling strategy. From the perspective of experiment design, measurement point should be set at the height of connecting pipe and near the wall for stratification stability criterion and impinging jet modelling validation.