• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.405-414
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• 2011

Recently, the development of several hundreds of kW scale PCS for fuel cell generation is required as commercialization process of distributed generation systems using high temperature fuel cells such as MCFC begins. This paper proposes and optimized topology suitable for MCFC fuel cell generation system and LCL filter design method considering voltage quality of local loads such as MBOP. An interleaving technique is applied to step-up DC-DC converter, optimized number of phases is determined considering efficiency and volume. Also, a LCL filter design method is proposed considering quality of current injected to the grid as well as that of voltage across the local load. The proposed PCS system is validated through reduced 1kW prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.1
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• pp.46-54
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• 2008

In this paper, a low-cost impedance spectroscopy system(LCISS) suitable for modeling the electrochemical power sources such as fuel cells, batteries and supercapacitors is designed and implemented. Since the developed LCISS is composed of simple sensor circuits, commercial data acquisition board and LabVIEW software, a graphic language with powerful HMI(Human-Machine Interface), it is expected ta be widely used in substitution of the expensive EIS instruments. In the proposed system, the digital lock-in amplifier is adopted to achieve the accurate measurements even in the presence of the high level of noises. The developed hardware and software is applied to measure the impedance spectrum of the Ballard Nexa 1.2kW proton exchange membrane fuel cell stack and an equivalent impedance model is proposed based on the measurement results. The validity of the proposed equivalent circuit and the developed system is proven by the measurement of the ac power losses of the PEM fuel celt stack by the ripple current.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.4
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• pp.339-356
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• 2018

Although fuel cell systems have advantages in terms of electric efficiency and environmental impact compared with conventional power systems, fuel cell systems have not been deployed widely due to their low reliability and high price. In order to guarantee the lifetime of 10 years, which is the commercialization goal of Polymer electrolyte fuel cells (PEFCs), it is necessary to improve durability and reliability through optimized operation and maintenance technologies. Due to the complexity of components and their degradation phenomena, it's not easy to develop and apply the diagnose and prognostic methodologies for PEFCs. The purpose of the paper is to show the current state on PEFC prognostic technology for condition based maintenance. For the prognostic of PEFCs, the model driven method, the data-driven, and the hybrid method can be applied. The methods reviewed in this paper can contribute to the development of technologies to reduce the life cycle cost of fuel cells and increase the reliability through prognostics-based health management system.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.6
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• pp.596-604
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• 2020

Solid oxide electrolysis cell (SOEC) attracts much attention because of its high energy efficiency among many water-electrolysis technologies. SOEC operates at temperatures above 700℃, so that the water required for water-electrolysis must be supplied in the form of steam. When the steam to be supplied to the SOEC is generated by the SOEC system itself, an enormous amount of latent heat is required to vaporize the water, so additional energy must be supplied to the SOEC system. On the other hand, if the steam can be supplied from the outside, a small amount of energy is required to raise the temperature of the low temperature steam, so that the SOEC system can be operated without additional energy supply from outside, which enables efficient water-electrolysis. In this study, we figure out the size of heat exchanger for various steam temperature and effectiveness of heat exchanger, and propose the energy efficiency of the system.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.2
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• pp.150-155
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• 2012

Polymer Electrolyte Membrane Fuel Cell (PEMFC) stack power output is needed to be approximately 100 kW to meet the requirements of automotive applications. In order to secure the electric safety for drivers, passengers and mechanics, it is very important to understand phenomena of an electric insulation in a fuel cell vehicle. In this study, we studied the electric insulation properties and the insulation resistance of stack, system and vehicle in the field of fuel cell was estimated at the applied voltage of 500 V, respectively. Also we discussed the insulation factors such as the conductivity of coolant, the element of vehicle design and the intrinsic resistance of the vehicle components.

• Journal of Magnetics
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• v.21 no.3
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• pp.405-412
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• 2016

In general, surface mounted PM synchronous motors (SPMSMs) are mainly adopted as a driving motor for high-speed applications, because they have high efficiency and high power density. However, the SPMSMs have some weak points such as the increase of magnetic reluctance and additional losses as a consequence of using a non-magnetic sleeve. Especially, the magneto-motive force (MMF) in the air-gap of the SPMSMs is weakened due to the magnetically increased resistance. For that reason, a large amount of PM is consumed to meet the required MMF. Nevertheless, it cannot help using the sleeve in order to maintain the mechanical integrity of a rotor assembly in high-speed rotation. Thus, in this paper, a multi-layer interior PM synchronous motor (IPMSM) not using the sleeve is presented and designed as an alternative of a SPMSM. Both motors are evaluated by test results based on a variety of characteristics required for an air blower system of a fuel cell electric vehicle.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.132-134
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• 2006

This paper presents the design and implementation of 1 kW prototype DC-DC power converter with bridge voltage-doubler suitable for small scale PEM fuel cell system and its associated control scheme. The operation principle of this converter is described using some operating waveforms and the switching mode equivalent circuits based on simulation results and a detailed circuit operation analysis and soft-switching conditions.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.503-512
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• 2012

There is a new power generation system such as direct coal fuel cell (DCFC) with a solid oxide electrolyte operated at relatively high temperature. In the system, it is of great importance to feed coal continuously into anodic electrode surface for its better contact, otherwise it would reduce electrochemical conversion of coal. For that purpose, it is required to improve the electrochemical conversion efficiency by using either rigorous mixing condition such as fluidized bed condition or just by recirculating coal particle itself successively into the reaction zone of the system. In this preliminary study, we followed the second approach to investigate how significantly particle recycle would affect the coal conversion efficiency. As a first phase, coal conversion was analyzed and evaluated from the thermochemical reaction of carbon with air under particle recirculating condition. The coal conversion efficiency was obtained from raw data measured by two different techniques. Effects of temperature and fuel properties on the coal conversion are specifically examined from the thermochemical reaction.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.193-195
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• 2008

As arising the cost and decreasing of gasoline and fossil fuel, renewable energy sources such as photovoltaics, wind and fuel cell have been interested. Among of them, PEM fuel cells are good energy sources to provide reliable power at steady state regardless of weather, time of day and location as long as the fuel and air are supplied, but they cannot respond to electrical load transients as fast as desired. This is mainly due to their slow internal electrochemical and thermodynamic responses. Therefore, to use the fuel cells with high efficiency, this paper finds characteristic curve and understand operation of PEMFC based on three theoretical approaches such as activation, ohmic and concentration and make the model using MATLAB. That result was compared with real system to certify.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.5
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• pp.403-409
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• 2008

Polymer electrolyte membrane fuel cell (PEMFC) is very interesting power source due to high power density, simple construction and operation at low temperature. But it has problems such as high cost, improvement of performance, effect of temperature and initial start at low temperature. These problems can be approached to be solved by using experiment and mathematical method which are general principles for analysis and optimization of control system for heat and hydrogen detecting management. In this paper, insulation vessel and control system for stable operation of fuel cell at low temperature were developed for experiment. The constant temperature capability and the heating time at sub-zero temperatures with insulation control system were studied by using a heating bar of 60W class. PEMFC stack which was made by 4 cells with $50\;mc^2$ active area in each cell is a thermal source. Times which take to reach constant temperature by the state of insulation vacuum were measured at variable environment temperatures. The test was performed at two conditions: heating mode and cooling mode. Constant temperature capability was better at lower environment temperature and vacuum pressure. The results of this experiment could be used as basis data about stable operation of fuel cell stack in low temperature zone.