• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.63-68
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• 2002

In a utility interactive photovoltaic generation system, a PWM inverter is used for the connection between the photovoltaic arrays and the utility. The do current becomes pulsated when the conventional inverter system operates in the continuous current mode and dc current pulsation causes the distortion of the ac current waveform. To reduce pulsation of dc input current, This paper presents a Buck-Boost PWM power inverter and its application for residential photovoltaic system. The PWM power inverter is realized by combining two sets of a high frequency Buck-Boost chopper and by making it operate in the discontinuous conduction mode. In this paper, we show the Buck-Boost PWM power inverter circuit, its equivalent circuit and basic differential equations and the power flow characteristics are clarified when the proposed Inverter is interconnected with the utility lines. In conclusion, the proposed inverter system provides a sinusoidal ac current for domestic loads and the utility line with unity power factor

• Journal of Electrical Engineering and Technology
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• 제12권4호
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• pp.1484-1494
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• 2017

We present a two-stage inverter with high step-up conversion ratio engaging modified finite-set Model Predictive Control (MPC) for utility-integrated photovoltaic (PV) applications. The anticipated arrangement is fit for low power PV uses, the calculated efficiency at 150 W input power and 19 times boosting ratio was around 94%. The suggested high-gain dc-dc converter based on Cockcroft-Walton multiplier constitutes the first-stage of the offered structure, due to its high step-up ability. It can boost the input voltage up to 20 times. The 3S current-source inverter constitutes the second-stage. The 3S current-source inverter hires three semiconductor switches, in which one is functioning at high-frequency and the others are operating at fundamental-frequency. The high-switching pulses are varied in the procedure of unidirectional sine-wave to engender a current coordinated with the utility-voltage. The unidirectional current is shaped into alternating current by the synchronized push-pull configuration. The MPC process are intended to control the scheme and achieve the subsequent tasks, take out the Maximum Power (MP) from the PV, step-up the PV voltage, and introduces low current with low Total Harmonic Distortion (THD) and with unity power factor with the grid voltage.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제55권5호
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• pp.280-286
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• 2006

The paper proposes a new protection algorithm for reliable operation of grid-interfaced PV system, which can flexibly interact with conventional protective schemes of power utility grid not only to prevent damages to utility or public persons and utility apparatus caused by malfunction or failure in distribution network protection system, but also to protect a PV system itself from faults or abnormal conditions of the network. The proposed algorithm is based on reclosing characteristics of the distribution system. As a network fault occurs, the new scheme determines whether it is momentary or permanent and responds in a pre-programmed way to the fault. For permanent outage, the proposed algorithm shuts down inverter's operations but monitoring system voltage and frequency at the point of common coupling with grid. When it comes to the momentary outage, Inverter starts stand-by operation mode so that it can be automatically connected to the grid without start-up procedures as soon as the system voltage and frequency returns into the normal operation range. In order to investigate' and evaluate the PV system operation, simulation study based on PSCAD/EMTDC has been carried out to verify the performance of the proposed protection scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기설비전문위원
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• pp.227-230
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• 2004

The Co-Gen System which maximize energy efficiency was installed at the industrial plants at the initial stage. However Small Scale Co-Gen System was expanded even to the general end-users such as housing and building owing to ESCO business recently. For this SSC, inter-connected operation to the utility is desirable due to voltage and frequency fluctuation following to unbalance between power output and load. Then voltage unbalance with utility system, frequency, increase of short circuit capacity, reclosing, and ALTS etc. should be fully considered for the inter-connected operation. Voltage variation, protection coordination, Co-Generators single running, and short circuit capacity should also be solved. For Con-Gen users, the several protection relays are recommended to install at the user's main incoming panel by the guide lines and/or instructions of the interconnected utility Then user's main CB(Circuit Breaker) have the chance to be tripped by some of this recommended relays and users have to undergo the unexpected blackout. So the circuit breaker trip schemes targeted to trip with these protection relays are reconsidered and the study result is hereunder proposed.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1999년도 전력전자학술대회 논문집
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• pp.659-662
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• 1999

As utility pollution take a growing interest, ac/dc converter optimizing utility condition has been vigorously studied in decades. In this paper three phase DCM converter is analyzed and equations for average input currents are presented. Also relationships of voltage gain & duty according to angular velocity are presented and variable frequency controller is implemented using reset integrator which is designed in detail. In result power factor and THD characteristics of 3-stage and 4-stage operation ae compared respectively.

• 인터넷정보학회논문지
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• 제16권6호
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• pp.89-95
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• 2015

전통적인 빈발 패턴 마이닝은 데이터베이스로부터 사용자 정의 최소 임계치 이상의 빈도수를 가지는 유효 패턴들을 식별한다. 적절한 임계치 설정은 해당 도메인에 대한 사전 지식을 요구하므로 쉬운 작업이 아니다. 따라서 임계치 설정을 통한 마이닝 결과의 정밀한 제어 불가능으로 인해 도메인 지식을 기반으로 하지 않는 패턴 마이닝 방법이 필요하게 되었다. 상위 K 빈발 패턴 마이닝은 이러한 문제를 해결하기 위해 제안되었으며, 임계치 설정 없이 상위 K개의 중요 패턴들을 마이닝 한다. 사용자는 이를 적용함으로써 데이터베이스에 상관없이 가장 높은 빈도수의 패턴부터 K번째로 높은 빈도수의 패턴까지 찾아낼 수 있다. 비록 상위 K 빈발 패턴 마이닝이 임계치 설정 없이 상위 K개의 중요 패턴들을 마이닝 하지만, 트랜잭션 내 아이템 수량과 데이터베이스 내 서로 다른 아이템 중요도를 고려하지 못하여 많은 실세계 응용의 요구에 부합하지 못한다. 하이 유틸리티 패턴 마이닝은 아이템 중요도가 포함된 비 바이너리 데이터베이스의 특성을 고려하기 위해 제안되었으나 최소 임계치를 필요로 한다. 최근 임계치 설정 없는 하이 유틸리티 패턴 마이닝을 위한 상위 K 하이 유틸리티 패턴 마이닝이 개발되었으며, 이를 통해 사용자는 사전 지식 없이 원하는 수의 패턴을 마이닝 할 수 있다. 본 논문은 상위 K 하이 유틸리티 패턴 마이닝을 위한 알고리즘을 분석한다. 최신 알고리즘에 대한 성능분석을 통해 개선사항 및 발전 방향에 대해 고찰한다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권4호
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• pp.366-373
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• 2005

This paper presents two new circuit topologies of the dc busline side active resonant snubber assisted voltage source high frequency link soft switching PWM full-bridge dc-dc power converters acceptable for either utility ac 200V-rms or ac 400V-rms input grid. These high frequency switching dc-dc converters proposed in this paper are composed of a typical voltage source-fed full-bridge PWM inverter, high frequency transformer with center tap, high frequency diode rectifier with inductor input filter and dc busline side series switches with the aid of a dc busline parallel capacitive lossless snubber. All the active switches in the full-bridge arms as well as dc busline snubber can achieve ZCS turn-on and ZVS turn-off transition commutation with the aid of a transformer leakage inductive component and consequently the total switching power losses can be effectively reduced. So that, a high switching frequency operation of IGBTs in the voltage source full bridge inverter can be actually designed more than about 20 kHz. It is confirmed that the more the switching frequency of full-bridge soft switching inverter increases, the more soft switching PWM dc-dc converter with a high frequency transformer link has remarkable advantages for its power conversion efficiency and power density implementations as compared with the conventional hard switching PWM inverter type dc-dc power converter. The effectiveness of these new dc-dc power converter topologies can be proved to be more suitable for low voltage and large current dc-dc power supply as arc welding equipment from a practical point of view.

• 패션비즈니스
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• 제6권1호
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• pp.1-19
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• 2002

The purpose of this study was to suggest the most appropriate design concepts for sportive fashion product based on the analysis of consumers' acceptance of the recent sportive fashion trends according to their lifestyle. The subjects consisted of 295 males and females, between 17 and 35 year-old. A self-report questionnaire with 4 stimuli was employed for data gathering, and the data were analyzed by the methods of frequency, factor analysis, cluster analysis, and Pearson's correlation coefficient. The results of this study were summarized as follows: For the First, the recent sportive fashion trends were categorized into four groups; 'street- sportive' trend, 'futuristic-sportive' trend, 'ethnic-sportive' trend and 'urban-utility sportive' trend. Secondly, based on the result of cluster analysis on consumers' lifestyle, total four consumer groups were identified; 'pursuing sense' group, 'pursuing culture' group, 'pursuing utility' group, and 'indifference' group. Thirdly, the consumers relatively preferred two sportive styles among the four groups, typically representing 'urban-utility' trend and 'street' trend. The typical 'urban-utility' style was particularly preferred by the consumers who desired to express themselves as urban, modern, and luxurious. The typical 'street' style was preferred by the consumers who tried to express themselves as active and fashionable. Finally, preferences of the sportive trends according to consumers' lifestyle were interpreted as follows: the 'pursuing sense' group relatively preferred 'urbanutility' style and 'street' style, the 'pursuing culture' group preferred 'street' style and the 'pursuing utility' group preferred 'urban-utility' style, meaningwhile the 'indifference' group preferred 'street' style and 'urban- utility' style.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.203-206
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• 2004

An islanding occurs when the utility grid is removed but distributed sources continuo to operate and provide power to local loads and grid. This can cause a significant risk to safety and equipment. This report present a novel anti-islanding method to prevent an islanding phenomenon. The proposed method changes the reactive power of the load. Therefore the phase difference between output voltage and current is periodically changed within decided value. When the utility-grid is removed, the frequency of output voltage and current will increase or decrease. And the proposed system will detect the change of frequency and shut down the distributed source. While the conventional methods have some difficulties in detecting particular islanding condition such as a small change in loading, the proposed method can detect most conditions. The performance was verified through experiments.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.129-137
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• 2002

Elastomers, which are used engine mounts and body mount rubbers, are traditionally designed for NVH use in vehicles, and for vibration isolation in specific frequency range. According to the measurement of the characteristics of the SUV's engine mounts, there are variability in same engine mount properties. Static and dynamic stiffness of the SUV's engine mounts are changed due to the driving miles accumulated. The pre-load of body mount rubbers are changed due to the empty vehicle weight, passenger's weight and gross vehicle weight. And the dynamic stiffness of body mount rubbers are changed very hard above 150Hz frequency range.