• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.194-195
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• 2010

This paper describers a bidirectional DC/DC converter for charging and discharging of a supercapacitor. Simulations are carried out to see the operation and performance of the 3kW-rated converter. Simulation results show that the charging/discharging characteristics is sufficient for the compensation of the response delay of a fuel cell.

• Journal of ILASS-Korea
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• v.27 no.3
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• pp.126-133
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• 2022

The objective of this is to experimentally investigate the effect of mixed jet on the oxygen transfer characteristics with the primary nozzle area ratio of an annular nozzle ejector for the application of a microbial fuel cell. A direct visualization method with a high speed camera system was used to capture the horizontal mixed jet images, and a binarization technique was used to analyze the images. The clean water unsteady state technique was used for the oxygen transfer measurement. The air-water mixed jet discharging into a water tank behaved similar to a buoyancy or horizontal jet with the primary nozzle area ratio. It was found that an optimum primary nozzle area ratio was observed where the oxygen transfer performance reached its maximum value due to the decrease of air volume fraction and the increase of jet length and air bubble dispersion.

• Clean Technology
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• v.10 no.1
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• pp.9-17
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• 2004

Direct methanol fuel cell(DMFC) with proton exchange membrane (PEM) has advantages over the conventional power source (e.g. vehicle). DMFC, however, has a problem to be solved such as methanol crossover, high anodic overpotential and limiting current density, etc. The physicochemical phenomena in DMFC can be described by coupled PDEs (partial differential equations), which can be solved by a PDE solver. In this paper, we utilized a commercial software FEMLAB to solve the PDEs. The FEMLAB is one of the software programs available which are developed as a solver for building physics problems based on PDEs and is designed to simulate systems of coupled PDEs which may be 1D, 2D, 3D, non-liner and time dependent. We performed simulation using the Tafel equation as an electrochemical reaction model to analyze methanol concentration profile in DMFC system. We confirm that the rapid decrease of methanol concentration at anodic catalyst layer with the increase of the current density is a main reason of the low performance in DMFC through simulation results.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2336-2338
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• 2000

고효율, 무공해의 신발전 기술인 연료전지 발전은 발전 용량 및 스택구성에 따라 차이가 있으나 기본적으로 저전압, 대전류 특성과 부하에 따라 발전 전압이 크게 변동하는 특성을 갖는 직류전원으로써 이를 상용으로 이용하기 위해서는 연료전지 발전 전력을 안정된 전력으로 변환하여 주는 장치가 필요하며, 이러한 전력 변환장치가 연료전지 발전의 최종 출력 전원의 질을 결정한다. 연료전지 전력변환장치는 전압조절기능, 승압 기능을 가져야 하고, 연료전지 본체와 부하를 안정하게 운전하기 위해 전력변환장치 뿐만 아니라 부하와 연료전지 본체의 운전상태 감지 기능, 각종 장치의 보호와 제어기능을 가져야 한다. 본 논문의 목적은 자동차용 연료전지 출력 전력변환장치의 종합제어장치의 설계를 위해 연료전지 스택시뮬레이터를 개발하는 것이다. 연료전지 스택 시뮬레이터는 연료전지 발전 특성과 일치하는 전력을 출력해 주는 직류전원 공급장치로써 이를 이용하여 연료전지 출력 전력변환장치의 종합제어장치를 충분한 예비실험과 수정, 보완함으로써 연료전지용 전력변환 시스템의 성능개선, 안정성 향상 등을 가질 수 있다.

• Journal of the Korean Solar Energy Society
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• v.31 no.4
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• pp.128-135
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• 2011

일반적으로 PEM 연료전지에서는 수분 균형이 시스템의 효율에 결정적으로 영향을 미치기 때문에, 이에 대한 균형(balance)을 잡는 것이 매우 중요하다. 특히, 촉매 층에서 물이 넘치는 익수현상(flooding)이나 건조현상(drying)이 발생하게 되면 연료전지의 효율이 급격하게 저하하므로, 항상 수분의 균형이 잡히도록 시스템을 제어하는 것이 일반적이다. 이 때,수분의 익수현상이나 건조현상은 PEM 연료전지의 용량과 주위의 환경, 즉 온도와 습도에 많은 영향을 받게 된다. 금번 논문에서는 가정용 규모인 3kW급에서 10kW급까지의 PEM 연료전지를 설치하였을 때, 주위의 환경(온도와 습도)이 수분 이동에 어떠한 영향을 미치는 지를 시간에 따라서 시뮬레이션(simulation)한 결과를 보여주고 있다. 결과에서 유입공기의 온도가 $50^{\circ}C$ 이하일 경우, 고정부하가 5kW급 이하이면 대부분이 건조현상이 발생하였으나, 고정부하가 6kW급 이상이 되면 익수현상이 운전시간이 20분 이내에서 발생하였다. 또한 고정부하를 최고 10kW급까지 올린 경우, 유입공기의 온도가 $50^{\circ}C$까지는 익수현상이 발생하였으나 $60^{\circ}C$ 이상인 경우에는 거의 건조현상이 발생함을 알 수 있었다.

• Elastomers and Composites
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• v.47 no.4
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• pp.310-317
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• 2012

A jute fiber surface was modified with argon gas in a cylinder type RF plasma generator to enhance the interfacial bond strength and to optimize the plasma treatment condition. The plasma power, gas pressure, and treat time were varied to figure out any effect of those parameters on the morphology and mechanical strength of jute fibers, and the interfacial bond strength for a model composite with polypropylene resin. As the severity of plasma treatment was increased, the surface of jute fibers became rougher. Gas pressure was less effective in roughening of the surface compared with those of treat time and plasma power. Approximately 25% drop in tensile strength of jute fibers was observed for the parameters of treat time and plasma power, while little deterioration was found for gas pressure, with increasing the severity. Based on the interfacial shear strength (IFSS), the optimum plasma treatment condition was determined to be treat time of 30 s, plasma power of 40 W, and gas pressure of 30 mTorr.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.81-83
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• 2009

가정용 연료전지의 상용화를 위해서는 시스템의 신뢰성과 경제성 향상이 중요한 문제이며, 경제성 향상은 시스템의 가격 절감과 컨버터의 효율 향상을 통해서 달성될 수 있다. 본 논문은 1kW급 가정용 연료전지 시스템을 위한 새로운 고효율 푸쉬풀 컨버터의 토폴로지를 제안한다. 제안된 컨버터는 2차측을 낮은 정격 전압을 가진 정류 다이오드를 사용한 2단 정류구조로 구성하여 다이오드의 손실을 저감시키고, 다이오드의 접합 커패시턴스와 변압기의 누설 인덕턴스의 상호작용에 의해 발생하는 공진 전압의 크기를 저감시킴으로써 스너버에서 소모되는 전력을 줄여 효율을 향상시켰다. 실험에서는 일반적인 형태의 푸쉬풀 컨버터 1차측 회로와 고주파 변압기는 공유하고, 2차측회로만 변경하는 방법으로 효율을 측정하여 비교함으로써 제안된 방식의 우수함을 증명하였다. 제안된 방식의 푸쉬풀 컨버터는 기존방식에 비해 특히 경부하에서 높은 효율을 나타내었으며, 전 부하 구간에서 효율의 변화가 크지 않아 부하가변 방식의 운전에 유용하게 사용될 수 있을 것으로 판단된다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.289-290
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• 2012

This paper proposes a new active snubber boost PFC converter to provide a zero-voltage-switching (ZVS) turn-on condition and reduce electromagnetic interference (EMI) noise in home appliances and renewable energy applications, including solar or fuel cell electric systems. The proposed active snubber circuit enables a main boost switch of the boost-type PFC or grid converter to turn on under a ZVS condition and reduce the switching losses of the main boost switch. Moreover, for the purpose of a specialized intelligent power module (IPM) fabrication, the proposed boost circuit is designed to satisfy some design aspects such as space saving, low cost, and easy fabrication. Simulation and experimental results of a 2kW IPM boost-type PFC converter are provided to verify the effectiveness of the proposed active snubber boost circuit.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.11-13
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• 2019

This paper proposes a novel high step-up non-isolated DC-DC converter, suitable for regulating dc bus in various inherent low voltage micro sources especially for photovoltaic (PV) and fuel cell sources. This novel high voltage Non-isolated Boost DC-DC converter topology is best replacement, where high voltage conversion ratio is required without the transformer and also need continuous input current. Since the proposed topology utilizes the stack-based structure, the voltage gain, and the efficiency are higher than other conventional non-isolated converters. Switches in this topology is easier to control since its control signal is grounding reference. Also, there is no need of extra gate driver and extra power supply for driver circuit, which reduces the cost and size of system. In order to show the feasibility and practicality of the proposed topology principle operation, steady state analysis and simulation result is presented and analyzed in detail. To verify the performance of proposed converter and theoretical analysis 360W laboratory prototype is implemented.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.18-20
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• 2008

An electrical balance of plant(EBOP) of a 600kW molten carbonate fuelcell (MCFC) has to transit from grid-connected(GC) mode to grid-independent(GI) mode when a grid is in a fault conditions. A minimum transition time is limited by four cycle for a 600kW MCFC to ride through a grid fault. In this paper, we propose a control algorithm of a 600kW EBOP for a MCFC system. The EBOP has three operation modes, i.e., GC mode, GI mode, and grid-synchronized(GS) mode. The EBOP controls output currents in a GC mode and regulates output voltages in GI or GS mode. GS mode is defined as an interface between GC mode and GI mode to make a mode transition smooth, i.e., limitation of inrush currents, regulation of output voltages within ANSI standard. Simulations and experiments carried out to verify the effectiveness of the proposed control algorithm.