• Journal of Power Electronics
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• v.10 no.4
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• pp.388-395
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• 2010

An active boost converter for a single phase SRM using series-parallel connected capacitors is proposed in this paper. The proposed active boost converter has two diodes and one power switch with an anti-parallel diode and one additional boost capacitor. The additional boost capacitor could be series or parallel connected to the dc-link capacitor to produce proper excitation and demagnetization voltage. The proposed active boost converter can easily achieve a fast excitation and demagnetization from the capacitor connection. In this paper, series and parallel connected converters are reviewed, and the detailed operating modes as well as the voltage characteristics of the proposed converter are analyzed. The simulation and experimental results shows the effectiveness of the proposed active boost converter.

• Journal of Power Electronics
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• v.11 no.1
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• pp.1-9
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• 2011

This paper describes a two quadrant bidirectional soft switching converter for ultra capacitor interface circuits. The total efficiency of the energy storage system in terms of size and cost can be increased by a combination of batteries and ultra capacitors. The required system energy is provided by a battery, while an ultra capacitor is used at high load power pulses. The ultra capacitor voltage changes during charge and discharge modes, therefore an interface circuit is required between the ultra capacitor and the battery. This interface circuit must have good efficiency while providing bidirectional power conversion to capture energy from regenerative braking, downhill driving and the protecting ultra capacitor from immediate discharge. In this paper a fully soft switched two quadrant bidirectional soft switching converter for ultra capacitor interface circuits is introduced and the elements of the converter are reduced considerably. In this paper, zero voltage transient (ZVT) and zero current transient (ZCT) techniques are applied to increase efficiency. The proposed converter acts as a ZCT Buck to charge the ultra capacitor. On the other hand, it acts as a ZVT Boost to discharge the ultra capacitor. A laboratory prototype converter is designed and realized for hybrid vehicle applications. The experimental results presented confirm the theoretical and simulation results.

• Journal of Drive and Control
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• v.16 no.3
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• pp.16-22
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• 2019

Due to the rise in energy consumption and natural resource prices, the demand to improve energy efficiency in the construction machine has been highlighted. Even though many researchers have contributed to the development of the technology, CO2 gas emissions of heavy machinery remains high. One of the most significant problems of the novel excavator with internal combustion engines is the emission of harmful gas. To reduce emissions in the construction machine, it is necessary to replace the internal combustion engines with the alternative one. To overcome those problems, this paper focuses on the adoption of PEMFC hybrid engine for the excavator system. An internal combustion engine is replaced by new structures with fuel cell, battery and ultra capacitor. The proposed system has been designed and modeled using Simcenter Amesim software and compared with the conventional one through simulation results.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.459-462
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• 2019

This work presents methods for reducing overshoot voltages across the drain-source of silicon carbide (SiC) MOSFETs in grid-connected hybrid active neutral-point-clamped (ANPC) inverters. Compared with 3-level NPC-type inverter, the hybrid ANPC inverter can realize the high efficiency. However, SiC MOSFETs conduct its switching operation at high frequencies, which cause high overshoot voltages in such devices. These overshoot voltages should be reduced because they may damage switching devices and result in electromagnetic interference (EMI). Two major strategies are used to reduce the overshoot voltages, namely, adjusting the gate resistor and using a snubber capacitor. In this paper, advantages and disadvantages of these methods will be discussed. The effectiveness of these strategies is verified by experimental results.

• Journal of Power System Engineering
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• v.22 no.1
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• pp.41-47
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• 2018

This paper analyzes the output characteristics of a self excited induction generator with isolated mode according to change of its speeds and loads for building a hybrid electric propulsion system in special purpose ships by using power take off. The induction generators are being considered as an alternative choice to the well-developed generators because of their lower unit cost, inherent ruggedness, operational and maintenance simplicity. However, the generator working by stand alone has a few problems that the reactive power is required to establish the air gap magnetic flux, and the induced voltage and magnetizing current fluctuate when the load is varied. In spite of its advantages, basic design data of the capacitor bank and behaviors of the output characteristics of the generator are not sufficient for the system. Based on the operating condition(speed range of main engine) of the target boat, a reduced experimental equipment system was constructed to analyze the output characteristics of the SEIG. And a suitable capacitor bank of a stand-alone generator and its output characteristics under various loads was investigated in detail through these experiments. According to the experimental result, it was confirmed that the capacitor bank should be $70{\mu}F{\sim}100{\mu}F$, and the proper SEIG induced voltage should be DC 80 V ~ 250 V in order to storage electrical energy into a battery.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.75-76
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• 2013

최근 산업 및 경제의 급속한 발전으로 컴퓨터를 비롯한 전기 및 전자 장비, 통신기기, 반도체 장비 등 전기적 외란에 민감한 부하 설비의 사용이 급증하면서 전력 품질에 대한 관심이 고조되고 있다. 그 이유는 정밀 부하 장비들이 전압의 순간적 변동에 대하여 민감하여 이 문제로 인하여 파생되는 경제적 피해가 매우 크기 때문에 지속적인 관리가 필요하다. 이러한 문제 중에서 가장 빈번하게 발생하는 순간 전압 강하를 보상하기 위한 장치로 전기 이중 층 커패시터 (EDLC: Electric Double Layer Capacitor)를 에너지 저장장치로 사용한 순간전압강하 보상장치 (DVR: Dynamic Voltage Restorer) 시스템이 개발 되어 적용되고 있다. 본 논문에서는 현재 순간전압강하 보상장치에 사용되는 DVR 시스템에서 주로 사용되는 에너지 저장장치인 EDLC 보다 동일 사이즈 대비 에너지 밀도가 높은 하이브리드 커패시터를 적용하는 연구를 하고자 한다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.108-108
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• 2005

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.145-152
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• 2003

Capacitance of a hybrid capacitor that has characteristics of both electrolyte capacitor and supercapacitor is determined by anode surface covered with oxide layer. In this study, optimal condition processes for anode to fabricate a high voltage hybrid capacitor was investigated. We mixed aluminum powder having mean particle size of $40{\mu}m$ with NaCl powders at weight ratio of 4 : 1 and prepared a disk type electrode after annealing at various temperature. After dissolving NaCl in $50^{\circ}C$ distilled water, heat treatment, eletropolishing, chemical treatment, and the first and the second etching of Al disk were conducted. In each process, capacitances and resistances of the disk measured by ac-impedance analyzer were compared to find its optimum treatment condition. Also, the surface morphology of treated disks were observed and compared by SEM. After the second etching, the Al disk was anodized at 365V to make an anode of hybrid supercapacitor that can be operated at 300V, Capacitance and resistance of the anodized Al disk electrode was compared with those of commercialized conventional aluminum electrolytic capacitor at different frequencies.

• 한국전기화학회:학술대회논문집
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• 2002.10a
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• pp.37-37
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• 2002

• 한국전기화학회:학술대회논문집
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• 2002.10a
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• pp.36-36
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• 2002