새로운 DC-DC 컨버터에 관한 연구

곽동걸,이현우 경남대학교 신소재연구소 1993 論文集 Vol.3 No.-

전력변환 시스템에서 전기적 절연이 요구될 때 절연에 대해 가장 적합한 부위는 직류 링크부이다. 직류부에서의 변압기는 높은 반복주파수이므로 소형화 할 수 있다. 더욱이 최근의 전력 초퍼와 스위칭 조절기 기술의 진보는 고속도, 고정밀성하게 직류전압의 제어가 가능하게 되었다. 본 논문은 전기적 절약의 양방향 DC-DC 컨버터에 대하여 논한다. 또한 컨버터에 대한 새로운 제어기술을 제어한다. 동작 되어지는 전력용 스위치들은 전류방향의 검출 없이 자동적으로 선택된다. When a n electric isolation in the power conversion system is required, the most suitable position for the isolation is the DC-Link part. A transformer in the DC part is minimized because of a high repetition frequency. Moreover, recent progress in the power chopper and the switching-regulator technique has enabled the control of the DC voltage with high speed and high accuracy. This paper deals with a bidirectional DC-DC converter with electric isolation, A mew control strategy for the converter is proposed. The power-switches which should be operated is selected automatically without a detection of the current-direction.

부분공진기법에 의한 승압형 DC-AC 인버터에 관한 연구

곽동걸,이현우 慶南大學校 附設 工業技術硏究所 1998 硏究論文集 Vol.16 No.-

제안되는 승압형 DC-AC 인버터는 승압과 소프트 스위칭이 동시에 이루어지는 회로구조를 가진다. 인버터부에 구동되는 스위치들은 부분공진 회로부의 스위치들과 서로 동기화 되어 소프트 스위칭으로 동작하여 스위칭 손실이 저감되고, 스위칭 제어기법도 간단하다. 그리고 제안된 회로는 기존의 인버터에서 발생하는 각 상의 스위칭 아암 단락에 의한 소자 소손을 제거하는 장점도 얻게 된다. A large number of soft swithing topologies included a resonant circuit have been proposed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose power conversion system, DC-AC inverter of high effciency and high power factor with soft switching mode by partial resonant method. The switching devices in a proposed circuits are operated with soft switching by the partial resonant method, that is PRS²MPC (Partial Resonant Soft Switching Mode Power Converter). The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in partial resonant circuit makes charging energy regenerated at input power source for resonant operation.

A Study on Isolated DCM Converter for High Efficiency and High Power Factor

Dong-Kurl Kwak 대한전기학회 2010 Journal of Electrical Engineering & Technology Vol.5 No.3

This paper is studied on a novel buck-boost isolated converter for high efficiency and high power factor. The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit makes use of a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuit and reduces a number of control components. The input ac current waveform in the proposed converter becomes a quasi sinusoidal waveform in proportion to the magnitude of input ac voltage under constant switching frequency. As a result, it is obtained by the proposed converter that the switching power losses are low, the efficiency of the converter is high, and the input power factor is nearly unity. The validity of analytical results is confirmed by some simulation results on computer and experimental results.

A Study on Isolated DCM Converter for High Efficiency and High Power Factor

Kwak, Dong-Kurl The Korean Institute of Electrical Engineers 2010 Journal of Electrical Engineering & Technology Vol.5 No.3

This paper is studied on a novel buck-boost isolated converter for high efficiency and high power factor. The switching devices in the proposed converter are operated by soft switching technique using a new quasi-resonant circuit, and are driven with discontinuous conduction mode (DCM) according to pulse width modulation (PWM). The quasi-resonant circuit makes use of a step up-down inductor and a loss-less snubber capacitor. The proposed converter with DCM also simplifies the requirement of control circuit and reduces a number of control components. The input ac current waveform in the proposed converter becomes a quasi sinusoidal waveform in proportion to the magnitude of input ac voltage under constant switching frequency. As a result, it is obtained by the proposed converter that the switching power losses are low, the efficiency of the converter is high, and the input power factor is nearly unity. The validity of analytical results is confirmed by some simulation results on computer and experimental results.

Residential Solar Cell System by driving of High Efficiency Inverter

Kwak Dong-Kurl,Lee Hyun-Woo 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10

With today's global environmental and energy problems, high expectations exist for solar power generation to reduce carbon dioxide generated by the consumption of fossil fuels. On the other hand, power consumption in residential homes is increasing every year Among the many household appliances, the power demand for air conditioners increases dramatically during the summer, particularly in the afternoons. As this pattern closely matches the output pattern of solar cells, it should be possible to combine a photovoltaic array with an air conditioner to decrease the energy consumption within the home. We Have developed a residential solar-powered air conditioner that operates through a combination of photovoltaic array and commercial power. In this paper, the configuration and specification of the residential solar-powered system are described to a novel high efficiency inverter using a ZVCS boost converter And the performance evaluations of the solar-powered air conditioner are examined by the analysis of a new tracking controller with a maximum power P_max detection of solar cell.<br/>

Novel Soft-Switching DC-DC Converter of High Efficiency

Dong-Kurl Kwak,Kyung-Jin Lee,Ki-Young SUH,Soon-Kurl KWON,Hyun Woo LEE 전력전자학회 1995 ICPE(ISPE)논문집 Vol.1995 No.10

In this paper, the authors propose a novel soft switching DC-DC converter of a high efficiency. The switching devices in a pro­posed circuit are operated with soft switching by the partial resonant method. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. The result is that switching loss is very low and efficiency of system is high. Also the proposed converter is deemed the most suitable for high power applications where the power switching devices are used.<br/> Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

PRS2M Three-Phase High Efficiency Converter

Dong Kurl Kwak,Hyung Woo Lee,Jung Ham Jun,Hyun Woo Lee 대한전자공학회 1998 ITC-CSCC :International Technical Conference on Ci Vol.- No.-

A Study on Novel Buck-Boost AC-DC Converter of High Performance by Partial Resonance Technique

Dong-Kurl Kwak,Bong-Seob Lee,Choon-Sam Kim,Jae-Sun Shim 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

The system efficiency of the proposed buck-boost AC-DC converter is increased by soft switching method. The converter includes to merit of power factor correction (PFC) from sinusoidal control of input current. The switching behavior of control switches operates with soft switching by partial resonance technique, and then the proposed converter has high system efficiency with decrement of switching power loss. The input current waveform in proposed converter is got to be a sinusoidal form of discontinuous quasi-pulse row in proportion to magnitude of AC input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity. The output voltage of the converter is regulated by PWM control technique. The discontinuous mode action of current flowing into inductor makes to simplify control method and control components. The proposed novel buck-boost AC-DC converter is analyzed to compare with the conventional PFC buck-boost converter. Some computer simulative results and experimental results confirm to the validity of the analytical results.

A Study on the Dynamic Image-Based Dark Channel Prior and Smoke Detection Using Deep Learning

Kwak Dong-Kurl,Ryu Jin-Kyu 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1

The detection of smoke in a fi re is a very important research topic because a large amount of carbon monoxide, which is potentially lethal, can be generated and released in the early stages of a fi re. In particular, if a fi re occurs in the form of smoldering combustion, it produces a glowing combustion without fl ames on the surface of the heat source, and the temperature is over 1000 °C. In this study, the dark channel prior, an algorithm previously used for haze removal, is used to detect areas where smoke may exist. The dark channel characteristic makes it possible to eff ectively detect the smoke area included background interference or noise. Additionally, in order to detect the characteristic that the smoke generated from the fi re rises due to the density diff erence at high temperatures, the area of the smoke was detected using the optical fl ow technique based on the Lucas–Kanade method. Image pre-processing using the dark channel prior and the optical fl ow technique can eff ectively detect the smoke areas and signifi cantly reduce false positive rate. Through this, in order to accurately determine the fi ltered region as smoke or non-smoke, a Convolutional Neural Network was employed. As a result, it was confi rmed that accuracy and precision were improved by 4% and 7%, respectively, compared to object detection models that performed detection without image pre-processing.

A Study on Fire Detection Using Deep Learning and Image Filtering Based on Characteristics of Flame and Smoke

Kwak Dong-Kurl,Ryu Jin-Kyu 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.5

When a fire breaks out, damage to human health is more often caused by poisoning and suffocation related to the occurrence of smoke than by a direct cause such as exposure to flame. In addition, fire that is in the condition of smoldering has fatal potential for the human body because it shows a high rate of production of carbon monoxide rather than carbon dioxide due to an incomplete combustion process. Therefore, this study sought to achieve early image-based detection not only of flames but also of smoke in the event of a fire. To this end, a flame area was pre-processed using color and corner detection, while smoke could be detected using dark channel prior characteristics and optical flow. For the pre-processed region of interest, a deep learning-based convolutional neural network was used to infer whether the region was a fire. Through this approach, it was possible to improve accuracy by lowering the error detection rate compared to when a fire was detected through an object detection model without separate pre-processing. To evaluate the performance of the proposed method, inference was conducted through a directly photographed image. As a result, the an accuracy level of 97.0% in the case of flames and 94.0% in the case of smoke could be confirmed.