• 농업과학연구
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• 제48권3호
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• pp.597-606
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• 2021

Due to the characteristics of the farmland in Korea, forward and reverse shift is the most used. The fatigue of farmers is caused by forward and reverse shifting with a manual transmission. Therefore, it is necessary to improve the convenience of forward and backward shifting. This study was a basic study on the development of a current control system for forward and reverse shifting of agricultural tractors using proportional control valves and a controller. A test bench was fabricated to evaluate the current control accuracy of the control system, and the stability of the controller was evaluated through CPU (central processing unit) load measurements. A controller was selected to evaluate the stability of the proportional valve controller. The stability evaluation was performed by comparing and analyzing the command current of the controller and the actual current measured. The command current was measured using a CAN (controller area network) communication device and DAQ (data acquisition). The actual current was measured with a current probe and an oscilloscope. The control system and stability evaluation was performed by measuring the CPU load on the controller during control operations. The average load factor was 12.27%, and when 5 tasks were applied, it was shown to be 70.65%. This figure was lower than the CPU limit of 74.34%, when 5 tasks were applied and was judged to be a stable system.

• 한국산업정보학회논문지
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• 제21권3호
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• pp.29-33
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• 2016

청정에너지 발전설비의 요구가 늘면서 태양광, 풍력, 연료 전지 등의 분산전원 개발이 급속도로 증가하고 있다. 반면에 이러한 증가로 인하여 배전시스템은 복잡해지고 있으며 무효전력으로 인한 역률 저감, 불평형 부하에 의한 불평형 전류 등의 문제점을 가지고 있다. 이러한 문제점들을 해결하기 위하여 본 논문에서는 태양광용 3상 4선 타입의 전력변환장치에 무효전력, 불평형 전류를 보상하는 알고리즘을 적용하였다. 제안한 태양광 전력변환장치는 기본 출력동작 뿐만 아니라 계통 전력 품질의 저해요소들에 대해서 보상이 가능하며 PSCAD/EMTDC를 이용한 시뮬레이션을 통하여 그 성능을 검증하였다.

• 한국항행학회논문지
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• 제26권1호
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• pp.35-45
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• 2022

본 논문에서는 PV 시스템에서 태양광 발전 시스템의 완전한 동작을 위해 DC-DC 벅-부스트 컨버터와 MPPT (Maximum Power Point Tracking)제어 시스템에 대한 완전한 동작 시스템에 대해 모델링하고 시뮬레이션을 수행하여 양호한 동작을 확인하고자 한다. 이를 위해 이중층 커패시터(EDLC:Electric double-layer capacitors )를 사용한 순간전압강하 보상장치가 개발되어 적용되고 있다. 따라서 태양광 발전의 ESS(Energy Storage System)를 고려한 PCS(Power Conditioning System)를 제안하여 부하평준화를 통한 전력의 안정적인 공급을 확인한다. 본 논문에서는 순간전압강하 보상장치(DVR :Dynamic Voltage Restorer)에 사용되는 전기 이중층 커패시터에 비해 동일 사이즈 대비 에너지 밀도가 높은 하이브리드 커패시터(hybrid capacitor)를 적용하는 연구를 하였고, 단상 3[kW] 계통 연계형 태양광 전력변환기를 제안하였다.

• 한국산학기술학회논문지
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• 제18권4호
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• pp.34-42
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• 2017

기존의 NIALM 연구들은 부하 식별을 위해 전압 변동은 무시할 수 있고 식별 결과에 영향을 주지 않는다고 가정하기 때문에 일반적으로 전압과 관련된 PF나, 고조파 신호는 부하 식별을 위한 매개 변수로 고려되지 않았으나, 실제 이러한 조건은 스마트 홈 분야에서 NIALM의 응용성이 제한되는 어려움이 만든다. 본 논문의 실험을 통해 부하 모니터링 시스템의 정확성과 신뢰성을 향상시키기 위해 전압과 관련된 매개 변수와 고조파의 특성을 사용해야 한다고 결론을 내렸다. 따라서, 본 논문에서는 홈 네트워크 환경에서 가전기기의 종류 및 전기 에너지 사용량을 효율적으로 분석할 수 있는 개선된 NIALM 방식을 제안한다. 제안된 방식은 가전기기 고유의 특징 및 동작 특성을 분석하고, 일부 가전기기가 가지고 있는 고조파 특성을 인식 매개변수로 활용함으로써 전력 에너지 사용 패턴 분석 및 추적할 수 있게 된다. 본 논문에서 제안된 방식을 통해 홈 네트워크에서 실제 운용되는 가전 에너지 효율성 증대와 스마트그리드 전력 수요관리 시장에 서비스를 제공할 수 있을 것으로 기대한다.

• Progress in Superconductivity
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• 제14권2호
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• pp.122-127
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• 2012

Current leads are one of the important components for carrying the current to the coil in the superconducting magnet system. Heat leakage through the current lead is the major factor of entire heat load in the cryogenic system because current leads carry the current from room temperature to near 4 K, connecting thermally each other. Therefore, minimization heat load through current lead can reduce the operating temperature of superconducting magnet. The semi-retractable current lead, composed of multi-contact connector and HTS element, is one of good options. Comprehension of Multi-contact connector's structure, contact resistance and heat generation is essential for estimating heat generation in current leads. Multi-contact connector has several louvers inside of socket and the shape, number, size of louvers are different with the size of connector. Therefore contact area, current path and contact resistance are also different. In this study, the contact resistance in multi-contact connector is measured using the electrical power as a function of connector's size and temperature. Also, the unique correlation of electrical contact resistance is derived and heat generation is estimated for superconducting magnet application.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.221-223
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• 2008

This paper presents a maximum power point tracking(MPPT) of Photovoltaic system with chopping ratio of DC-DC converter considered load. A variation of solar irradiation is most important factor in the MPPT of PV system. That is nonlinear, aperiodic and complicated. The paper consists of solar radiation source, DC-DC converter, DC motor and load(cf, pump). NN algorithm apply to DC-DC converter through an adaptive control of neural network, calculates converter-chopping ratio using an adaptive control of NN. The results of an adaptive control of NN compared with the results of converter-chopping ratio which are calculated mathematical modeling and evaluate the proposed algorithm. The experimental data show that an adequacy of the algorithm was established through the compared data.

• 한국조명전기설비학회지:조명전기설비
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• 제11권3호
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• pp.88-96
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• 1997

본 논문은 배전시스템에서의 파라미터에 따른 과도현상을 분석하였다. 재투입에 의한 순간전압강하와 개폐서지를 분석하였으며, 이를 위해서 22.9[kV] 배전시스템의 실 데이터를 이용하여 다중접지된 모델 시스템을 구성하였다. EMTP 시뮬레이션을 통하여 주상변압기 2차측 수용가에서의 재투입 영향을 분석하였으며, 사고선로와 인근선로에서의 과도현상을 나타냈었다. 또한 사고위치, 부하크기, 부하역률, 캐패시터뱅크의 크기, 재투입 위상각에 대한 파라미터 분석을 하였고, 이들 요소와 재투입에 의한 과도 현상과의 관계를 나타내었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1272-1275
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• 2007

The HDD (hard disk drive) using Load/Unload (L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop (CSS). Dynamic L/UL has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. Main design objectives of the L/UL mechanisms are no slider-disk contact or no media damage even with contact during L/UL, and a smooth and short load and unload process. In this paper, we focus on state matrix, pitch static attitude (PSA), roll static attitude (RSA), loading/unloading contour (LC/ULC), impact force and contact. Stability of slider is mainly determined by PSA and RSA. State matrix by PSA and RSA is also important indicator. Therefore we analyze state matrix of SFF HDD suspension through the LC/ULC.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.609-612
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• 2007

The HDD (hard disk drive) using Load/Unload (L/UL) technology includes the benefits which are increased areal density, reduced power consumption and improved shock resistance than those of contact-start-stop (CSS). Dynamic L/UL has been widely used in portable hard disk drive and will become the key technology for developing the small form factor hard disk drive. The main design objectives of the L/UL mechanisms are no slider-disk contact or no media damage even with contact during L/UL, and a smooth and short unloading process. In this paper, we focus on lift-off force, pitch static attitude (PSA), roll static attitude (RSA) and dimple point. The "lift-off" force, defined as the minimum air bearing force, is another very important indicator of unloading performance. A large amplitude of lift-off force increases the ramp force, the unloading time, the slider oscillation and contact-possibility. PSA and RSA are also very important parameters in L/UL system and stability of slider is mainly determined by PSA and RSA. Dimple point by PSA and RSA is also important indicator. Therefore we find the optimal dimple point of SFF HDD suspension for improving the unloading performance.

• Journal of Electrical Engineering and Technology
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• 제3권3호
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• pp.354-362
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• 2008

In this paper, a new algorithm of optimal voltage control is proposed for the Distribution Automation System (DAS) based on constants of four terminal network modeling. In the proposed method, the voltage profiles along feeders are estimated from the measurement of the current and power factor by a Feeder Remote Terminal Unit (FRTU) installed at each node. Whenever the voltage profile violates the restriction, the voltage control strategy is applied to keep the voltage levels along the feeders within the pre-specified range through the modification and coordination of the transformer under-load tap changers (ULTC), step voltage regulator (SVR), as well as shunt condenser. In the case studies, the estimation and control of the voltages have been testified in a radial distribution system with 11 nodes.