• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.320-321
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• 2018

A non-isolated high voltage gain bidirectional DC-DC converter for battery storage system has been presented in this paper. The topology is composed of boost converter and traditional SEPIC converter. The proposed converter can achieve higher voltage conversion ratio with reduced voltage and current stresses in the switches. In additional, a reduced number of components are included in this topology. The PSIM simulation is carried to validate the analysis and operation of the converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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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.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.163-164
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• 2015

본 논문에서는 고승압비를 갖는 단일스위치 ZCS 병렬 공진 컨버터를 제안한다. 제안하는 컨버터는 단일스위치를 사용하여 구조가 간단하며 병렬 공진회로를 이용하여 고승압이 가능하다. 또한, 별도의 클램프 회로 없이 전 부하영역에서 스위치의 ZCS 턴온 및 턴오프와 다이오드의 ZCS 턴오프를 성취한다. 제안하는 컨버터는 250W 시작품을 제작하여 타당성을 검증하였다.

• Journal of Power Electronics
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• 제16권6호
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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.

• 한국지능시스템학회논문지
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• 제13권4호
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• pp.461-468
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• 2003

In a sequence of images obtained by surveillance cameras, facial regions appear very small and their colors change abruptly by lighting condition. This paper proposes a new face detection scheme, robust on complex background, small size, and lighting conditions. The proposed method is consisted of three processes. In the first step, the candidates for the face regions are selected using face color distribution and motion information. In the second stage, the non-face regions are removed using face color ratio, boundary ratio, and average of column-wise intensity variation in the candidates. The face regions containing eyes and mouth are segmented and classified, and then they are scored using their topological relations in the last step. To speed up and improve a performance the above process, a block based image segmentation technique is used. The experiments have shown that the proposed algorithm detects faced regions with more than 91% of accuracy and less than 4.3% of false alarm rate.

• 한국전자통신학회논문지
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• 제11권9호
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• pp.893-900
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• 2016

극점의 위치와 제동비의 변화에 따른 출력응답을 해석하였다. RLC 회로의 시스템 모델링과 출력응답을 단위계단함수와 정현파 입력에 따라 해석하였다. 프로그램으로 확인한 내용들이 이론을 이해하는데 도움이 되었는지를 설문으로 평가하였다. 조사에서 시스템의 전달함수를 해석하는 능력은 이해도가 높게 나타났다. 또한 매개변수 변화에 따른 출력응답 파형을 이해하는 능력도 높게 나타났다. 시간영역의 출력응답을 계산할 수 있다는 응답이 다소 낮게 나왔으며, 이는 부분분수의 조합이 어려웠던 것으로 분석된다.

• 전력전자학회논문지
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• 제13권2호
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• pp.79-87
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• 2008

연료전지의 낮고 변동폭이 큰 전압을 안정된 높은 전압으로 승압시키기 위하여 부스트 컨버터가 사용되고 있다. 전기적인 절연이 요구되지 않는 응용에서는 손실, 가격 및 부피 상승의 원인이 되는 고주파 변압기가 없는 무변압기형의 부스트 컨버터가 장점을 갖는다. 본 논문에서는 새로운 무변압기형 부스트 컨버터를 제안한다. 제안한 컨버터는 $6{\sim}8$배의 실제 사용가능 한 승압비를 가지며 입 출력 전류 리플이 매우 작아 연료전지 응용에 적합하다. 이에 대한 이론적 해석과 시뮬레이션 및 실험파형을 통해 타당성을 검증하였다.

• 전력전자학회논문지
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• 제13권2호
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• pp.119-127
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• 2008

본 논문에서는 모듈형 계통연계 태양광 PCS (photovoltaic power conditioning system)를 제안하였다. 능동-클램프 회로와 듀얼 직렬-공진 정류 회로를 이용하여 높은 입출력 전압 비를 효과적으로 구현하고 효율을 높인 승압형 DC-DC 컨버터를 제안하였다. 최대 전력점 추종 특성을 개선한 IncCond (incremental conductance) 방식의 MPPT (maximum power point tracking) 알고리즘을 사용하였다. 이 때 DC 전류 센서를 사용하지 않고 태양전지 모듈 (PV module)의 전류를 예측한다. 선형화 기법을 사용한 출력 전류 제어기로 인버터를 제어하여 단위 역률을 실현하였다. 모든 알고리즘과 제어기를 하나의 마이크로컨트롤러로 구현하고 제안된 DC-DC 컨버터와 제어기의 우수성을 실험을 통해 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.238-243
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• 2003

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. The output power of solar cell is DC, therefore it is necessary to install an inverter among electric power converts. The inverter have to supply a sinusoidal current and voltage to the load and the interactive utility line. In the paper, the proposes a photovoltaic system designed with a step up chopper and single phase PWM voltage source inverter. Synchronous signal and control signal was processed by microprocessor for stable modulation. The step up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature because solar cell has typical dropping character. The single phase PWM voltage source inverter consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be developed continuously by connecting with the source of electric power, from 10 to $20\%$. The single phase PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Journal of Power Electronics
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• 제18권3호
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• pp.662-671
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• 2018

This paper presents a new structure for a step up dc-dc converter, which has several advantageous features. Firstly, the input dc source and the clamped capacitor are connected in series to transfer energy to the load through dual voltage multiplier cells. Therefore, the proposed converter can produce a very high voltage and a high conversion efficiency. Secondly, a double voltage clamped circuit is introduced to the primary side of the coupled inductor. The energy of the leakage inductance of the coupled inductor is recycled and the inrush current problem of the clamped circuits can be shared equally by two synchronous clamped capacitors. Therefore, the voltage spike of the switch tube is solved and the current stress of the diode is reduced. Thirdly, dual voltage multiplier cells can absorb the leakage inductance energy of the secondary side of the coupled inductor to obtain a higher efficiency. Fourthly, the active switch turns on at almost zero current and the reverse-recovery problem of the diodes is alleviated due to the leakage inductance, which further improves the conversion efficiency. The operating principles and a steady-state analysis of the continuous, discontinuous and boundary conduction modes are discussed in detail. Finally, the validity of this topology is confirmed by experimental results.