• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.297-298
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• 2014

현재 제동장치(Brake system)는 운동에너지를 열에너지로 바꾸어 공기 중으로 발산시킴으로서 제동 작용을 하는 마찰형 Brake가 대부분이다. 이러한 제동장치 속에는 리터더라는 제동력을 유발하는 장치가 있는데 이중 빠른 응답특성을 띄는 전기식 리타더의 단점인 전기에너지 소비 측면을 극복하기 위하여 제동에너지를 전기에너지로 회생하여 에너지를 절감 할 수 있는 기술이 선진국에서는 이미 진행이 되고 있다. 본 논문에서는 리타더에서 발생되는 3상 전압을 정류하여 받은 DC전압을 입력으로 받아 24V로 강압시키고 배터리를 충전하는 DC-DC 컨버터를 제작하고 이에 따른 보완점 및 타당성을 실험을 통하여 검증하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.6
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• pp.788-793
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• 2014

In this study, the electrical power consumption saving effect is studied through installing an inverter which is able to control the R.P.M. of marine sea water pump by effective flow control. The study looks at how sea water pump's flow control influences on the system without the Marine Growths Protection System(MGPS). Auxiliary sea water pump and refrigerator sea water pump in training ships, which are always operated not only in harbor but also in navigation, was used in the experiment and the experiment was conducted by dividing into harbor and navigation. As a result of research, in the case the sea water temperature is under $18^{\circ}C$, the operation was possible with a 58.3 % decrease in pump R.P.M. and electric power consumption was saved by 50 %. In spite of the sea water temperature increasing upto $34^{\circ}C$, pump R.P.M. at 91.6 % was sufficient to operate with a 20 % electric power consumption saving effect. In the pipelines without MGPS, lowering R.P.M. along with lowering pressure results in the attachment of various marine growths.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1583-1584
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• 2015

최근 철도차량의 고속화와 전력회생을 하는 전기차로 인하여 부하전류와 고장전류 간의 큰 차이가 없으므로 이를 구분할 수 있는 고성능 보호시스템의 중요성이 날로 증대되고 있다. 본 논문은 실계통에서의 전차선로 임피던스를 이용하여 AT급전시스템을 모델링하였으며 변전소와 보조급전구분소사이 단락사고의 과도특성을 분석하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.627-633
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• 2004

Downlink beamforming is very important in recent mobile communications which requires wireless internet, VOD(Video-On-Demand), multimedia services. This paper addresses and analyzes the essential considerations fur downlink beamforming of smart antenna system to provide wanted characteristics. Major considerations in this paper are HPA power allocation for downlink beamforming, received power at mobile terminal, concept and performance of auxiliary pilot channel, importance and moth of array calibration, and throughput comparison of downlink and uplink. All above mentioned items are investigated in this paper.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.01a
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• pp.1-3
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• 2016

낸드 플래시 메모리는 저 전력, 빠른 동작 속도, 높은 신뢰성, 가벼운 무게와 같은 특성을 가지는 비휘발성 메모리로써 폭넓은 분야에서 사용이 증가하고 있다. 그러나 낸드 플래시 메모리는 기존의 보조 기억 장치와 달리 쓰기 전 소거와 낮은 수명에 대한 문제가 존재한다. 기존의 많은 연구에서는 가비지 컬렉션을 통해 수명을 연장하기 위해 노력하였다. 본 논문에서는 낸드 플래시 메모리에 삭제 구간 정보를 활용한 가비지 컬렉션 기법을 제안한다. 제안하는 기법은 "N 삭제 구간 정보"를 이용하여 효과적인 희생블록을 선정하는 특징이 있다. 제안하는 기법은 GA 기법과 비교하여 평균 페이지 이주비용은 최대 50.1% 감소하였으며, 블록 당 소거 횟수의 표준 편차는 최대 233% 감소하였다. 또한, 낸드 플래시 메모리 시스템의 첫 번째 배드 블록 발생 시간은 최대 22.7% 연장하였고, 시스템 수명은 최대 16.7% 연장하였다.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.481-483
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• 2008

본 논문은 다양한 종류의 전원을 구비해야 하는 다중출력 전원 시스템을 위한 영전류 스위칭 LLC 공진형 Post-regulator를 제안한다. 기존의 LLC 공진형 컨버터는 정밀한 다중 출력을 얻기 위해 추가의 DC/DC 컨버터가 구성되었고, 이는 전력 변환 효율 감소 및 제조 원가 상승의 단점을 갖고 있다. 제안된 컨버터는 각 소자의 내압 및 전류 스트레스가 작고, 요구되는 출력 당 1 개의 보조 스위치만으로 구현되므로 저가격화에 유리하다. 또한 전력이 전달되는 시점의 공진 전류의 초기값을 가변함으로서 정밀하게 제어되는 다중 출력 전압을 획득할 수 있고, 각 전압의 출력 순서 제어도 가능한 장점이 있다. 뿐만 아니라, 독립된 공진탱크를 이용하기 때문에 공진탱크 설계가 용이하며, 최근 전자 제품의 추세인 슬림화의 요구에 부응할 수 있다. 또한, 제안된 Post-regulator의 모든 전력 스위치는 ZCS가 가능하므로 스위칭 손실을 최소화 할 수 있다. 최종적으로 본 논문에서 제안한 영전류 스위칭 LLC 공진형 Post-regulator를 제작하고, 고찰된 실험결과를 제시하여 제안된 컨버터 및 전원시스템의 우수성과 이론적 분석의 타당성을 검증한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.202-207
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• 2016

An auxiliary real-time train communications system among drivers, train-traffic controllers and field workers is necessary to share hazard information (i.e. rockfall detection, track maintenance) in low visibility zones (long tunnels and steep curved track). To develop the appropriate communication system, this paper proposes a new way of power line communication using the rail track (Rail - PLC), which has little noise and distortion of attenuation. Therefore, it is important to measure the impedance of the rail and to apply an impedance matching technique to increase the transmission characteristic of the Rail - PLC. This study would evaluate the reflection and the transmission characteristics of the rail using a network analyzer and an impedance matching transformer. The suitable impedance matching ratio was 1:3.28 from the result of back-to-back testing. The results confirmed that the transformer can improve the performance of the transmission signal in Rail - PLC using an impedance matching technique.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.46-53
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• 2009

A new zero-current switching LLC resonant post-regulator for multi-output power system is proposed in this paper. A conventional LLC resonant converter employs extra non-isolated DC/DC converters to obtain tight-regulated multi-slave output voltages. Therefore, it has several serious problems such as a poor efficiency and high cost of production. The proposed post-regulator features low voltage and current stress across the output rectifier diodes and power switches. Moreover, the proposed post-regulator requires only one power switch instead of the bulky and expensive non-isolated DC/DC converter. Therefore, it features a simple structure and lower cost. Especially, since the proposed post-regulator can ensure the ZCS of all power switches, it has very desirable advantages such as more improved EMI characteristics and reduced switching losses. Finally, to confirm the operation, validity, and features of the proposed circuit, experimental results from a proposed zero-current LLC resonant post-regulator are presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.121-128
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• 2002

A new high-efficient energy-recovery circuit is proposed to drive a plasma display panel (PDP) and compared with the conventional circuit. The proposed circuit uses only two inductors and no auxiliary circuit to recover the energy stored in the equivalent intrinsic capacitance of PDP. Therefore it features a simpler structure, less mass, lower cost of production, higher efficiency, and fewer power devices. The very stable and uniform light emitted from PDP proves the high quality of screen. It is suitable for wall-hanging color TVs. The proposed circuit, operating at 200kHz, is verified to be applicable on a 42-inch PDP by experimental results.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.7
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• pp.317-326
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• 2002

In this paper, a methodology for optimal PI supplementary controller using the modified genetic algorithm has been proposed to the oscillation damping in HDVC transmission system. These study processes are summarized as the formulation for load flow calculation in HVDC transmission system with SVC, the investigations on the basic control in HVDC system, the mathematical modeling for dynamic characteristics analyses, and the optimal design of MGA based PI controller generation the supplementary control signal of SVC. Its properties were verified through a series of computer simulations including dynamic stability. It means that the application of MGA-PI controller in HVDC transmission system can contribute the propriety to the improvement of the stability in HVDC transmission system and the design of MGA-OI controller has been proved indispensible when applied to HVDC transmission system.