• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.73-75
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• 1993

In this paper, the transient shielding characteristics of slitted electrothermal shield of superconducting alternator is studied. The field current and the armature currents variations during three phase short circuit fault are calculated and compared to those of the conventional one. And the response of the armature current due to step-up of the excitation voltage showes the feasibility of the quick response excitation system available for improving the transient stability.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.339-340
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• 2010

본 논문에서는 배터리를 이용한 직류전원 백업장치, HID 램프, 연료전지 시스템 등 고승압이 요구되나 절연이 필요 없는 응용을 위한 새로운 비절연 컨버터를 제안한다. 제안한 컨버터는 인터리빙이 적용되고 CCM에서 모든 스위치의 ZVS 턴온과 다이오드의 ZCS 턴온 턴오프가 가능하며, 최적의 소자 선택이 되도록 배압회로의 수를 적절히 선정하여 회로구성이 가능한 장점이 있다. 1kW 시작품으로 동작원리를 확인하였으며 최고효율 96.1%를 달성하였다.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.343-345
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• 2005

In comparison to general purpose step-up/down transformer, welding transformer for resistance spot welding requires strict design criteria. The major significant specifications include duty cycle, arm length and its geometric configuration(window area) as well as various current/voltage conditions and material properties. This interactive program propose new promising procedure for weldling transformer. Users can input design variables and modify in accordance with graphic Output.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1982-1983
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• 2001

직류 100 kV 까지 고전압의 국가 측정표준을 확립하기 위하여 저항형 분압기의 비율을 정밀 측정하는 방법을 고안하였다. 일반적으로 저항형 분압기의 비율은 사용 전압에 따라 변하므로 저항과 전압비율을 동시에 측정하는 기술이 요구된다. 본 발표에서는 고안된 binary step-up 방법의 원리를 설명하고 실제 적용 시 예상되는 불확도를 계산하고자 한다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.197-198
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• 2012

본 논문에서는 배전압셀을 이용한 비절연 고승압 컨버터의 최적설계기법을 제안한다. 제안한 컨버터는 배전압셀 수를 적절히 선정하여 소자의 전압정격을 줄일 수 있으며 작은 듀티로도 높은 승압비를 얻을 수 있다. 제안한 컨버터의 ZVS 영역 분석, 주요 수동소자 설계를 통하여 모든 스위치의 ZVS 턴온을 달성시킬 수 있는 설계기법을 제시한다. 1kW급 시작품으로 제안한 설계기법의 타당성을 검증하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.5
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• pp.395-401
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• 2015

This paper proposes a new bidirectional DC-DC converter with high efficiency. The proposed converter is composed of a flyback and a tapped-inductor boost converter to satisfy extreme operating conditions with low cost. The outputs are connected in series to achieve a high-voltage step-up. In the reverse direction, the proposed converter has an extreme step-down voltage. In this study, the proposed converter was employed with a 100 W hardware prototype. To design the controller, a small-signal transfer function of the proposed converter is derived. For PV power conditioning systems, a maximum power point tracking method is applied with perturb and observe method. To verify the operation of the bidirectional power flow, the current controller is applied. All of the controllers are employed with a digital signal processor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.2
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• pp.75-81
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• 2015

At the end of the 19th century, Edison's DC power system and Tesla's AC power system was debated in power market. Finally, AC system became the primary system of the power market because both step-up and step-down of voltage by using transformer and long-distance power transmission are easily possible. However, nowadays the power market takes some action for introducing DC system. Both domestic and foreign researchers are conducting the study on the DC system as well. Some researchers have conducted the studies on power quality and economic evaluation of the DC distribution system but DC distribution system is still controversial in terms of the effectiveness and reliability. In this paper, we calculate the reliability indices of the Low Voltage Direct Current(LVDC) distribution system considering arrangement of power electronics, layout of the distribution system, and distance between load points.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.76-82
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• 2017

Since the introduction of electronically controlled engines and electric propulsion ships, the need for an uninterruptible power supply for emergency power supply devices that use batteries has gained importance. The bidirectional converter in such emergency power supply devices is a crucial component. This paper proposes, a topology for an improved DC-DC bidirectional converter that is characterized by a high voltage conversion ratio and low voltage stress of switches. To confirm the performance of the converter, a computer simulation was executed with PSIM software. The conversion ratio of the proposed converter was found to be four times higher than the conventional boost converter in step-up mode and one-fourth that of the conventional buck converter in step-down mode, and the voltage stress of the switches was one-fourth of the high-side voltage. Moreover, the proposed converter was confirmed to be able to distribute equal currents between two interleaved modules without using any extra current-sharing control method because of the charge balance of its blocking capacitors.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2035-2044
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• 2016

In order to match the voltages between high voltage battery stacks and low voltage super-capacitors with a high conversion efficiency in hybrid energy sources electric vehicles (HESEVs), a high ratio bidirectional DC-DC converter with a synchronous rectification H-Bridge is proposed in this paper. The principles of high ratio step-down and step-up operations are analyzed. In terms of the bidirectional characteristic of the H-Bridge, the bidirectional synchronous rectification (SR) operation is presented without any extra hardware. Then the SR power switches can achieve zero voltage switching (ZVS) turn-on and turn-off during dead time, and the power conversion efficiency is improved compared to that of the diode rectification (DR) operation, as well as the utilization of power switches. Experimental results show that the proposed converter can operate bidirectionally in the wide ratio range of 3~10, when the low voltage continuously varies between 15V and 50V. The maximum efficiencies are 94.1% in the Buck mode, and 93.6% in the Boost mode. In addition, the corresponding largest efficiency variations between SR and DR operations are 4.8% and 3.4%. This converter is suitable for use as a power interface between the battery stacks and super-capacitors in HESEVs.

• Journal of Sensor Science and Technology
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• v.7 no.4
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• pp.293-299
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• 1998

An objective of this study is to develop a voltage measuring device that uses a gas-filled switch (GS) on 22.9 kV-y extra-high voltage distribution lines. The voltage measuring device proposed in this paper is a kind of capacitive divider which consists of a detecting electrode attached outside of the bushing of GS, an impedance matching circuit, and a voltage buffer. It can be easily installed in an established GS without changing the structure. For the calibration and application investigations, the voltage measuring device was set up in the 25.8 kV 400 A GS, and a step pulse generator having 5 ns rise time is used. As a result, it was found that the frequency bandwidth of the voltage measuring device ranges from 1.35 Hz to about 13 MHz. The error of voltage dividing ratio which is evaluated by the commercial frequency voltage of 60 Hz was less than 0.2%. In addition, voltage dividing ratio in the commercial frequency voltage and in a non-oscillating impulse voltage were compared, and their deviation were less than 0.7%.