• Proceedings of the KIEE Conference
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• 2002.11b
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• pp.91-93
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• 2002

자가발전기가 운전되는 산업체 전력계통에서 대형 유도전동기 기동 특성을 안정도 해석 프로그램을 이용하여 해석하고 과도한 기동전류로 발생하는 전압 강하 문제를 해결하기 위해 기동방안을 모의하여 적정성을 검증한 실계통 적용 연구사례이다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.2
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• pp.175-181
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• 2009

In this paper, it is suggested that the selection method of parameter of Power System Stabilizer(PSS) with robustness in low frequency oscillation for Static VAR Compensator(SVC) using a self tuning fuzzy controller for a synchronous generator excitation and SVC system. The proposed parameter self tuning algorithm of fuzzy controller is based on the steepest decent method using two direction vectors which make error between inference values of fuzzy controller and output values of the specially selected PSS reduce steepestly. Using input-output data pair obtained from PSS, the parameters in antecedent part and in consequent part of fuzzy inference rules are learned and tuned automatically using the proposed steepest decent method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.10
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• pp.21-28
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• 2009

Power capacitor has been used to compensate for the low power factor of inductive load and to reduce harmonics generated by the power conversion device with reactor. Power quality is mainly referred to the voltage quality and it is very important for the stable operation of load. But if voltage rms is temporary changed, it acts on capacitor as an electrical stress. In this paper, we analyzed that capacitor can be given by voltage, current and capacity's variance under the sag and swell condition. If reactor is connected at capacitor, sag can be aside from the question. But it can act an amount of stress on capacitor in the swell region.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.179-180
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• 2016

본 논문은 차량 시동 시 발생하는 급격한 배터리 전압강하를 예측하여, SLI용 리튬이온 배터리의 시동가능 여부를 판단하는 SOF 추정 알고리즘을 제안한다. 제시하는 알고리즘은 전압강하를 묘사하는 배터리 등가 저항을 분석하고, 주파수 분석을 이용한 실시간 파라미터 추정을 통해 추정 정확도를 향상시킨다. 알고리즘 정확도는 MATLAB 시뮬레이션으로 검증한다.

• Proceedings of the KIEE Conference
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• 2007.11b
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• pp.40-42
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• 2007

본 논문은 전기기기에 순간전압저하를 발생 하였을 경우 응동특성에 대한 영향을 계측하였다. 실험 방법은 AVR에서 Sag 발생기인 IPC에 입력한 후, IPC에서 전압의 크기와 시간을 조정하여 실험기기에 순간전압 강하를 발생하였다 실험기기는 PLC, 전자접촉기, 400[W]고압방전램프를 시험하였다. PLC시험에서 무부하와 정격부하에 따라 특성 의 변화가 생겼으며, 정격부하에서 Voltage Sag의 영향을 더 받았다 전자접촉기의 시험은 위상을 $0^{\circ},\;30^{\circ},\;60^{\circ},\;90^{\circ}$로 변화하여 Voltage Sag 발생시켜 계측하였으며, 위상의 변화에 따라 특성곡선이 변화하였다. 고압방전램프시험은 고압나트륨램프와 수은램프, 메탈헬라이드에 Voltage Sag를 발생시켰다. 방전램프의 시험결과 고압나트륨램프의 특성곡선이 가장 안정적으로 나타났다. 본 실험을 통해 순간전압저하에 대한 저압기기의 특성을 실험적으로 입증하여 전력시스템의 설계에 영향을 미칠 것이라 기대된다.

• Proceedings of the KIEE Conference
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• 2005.11c
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• pp.83-86
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• 2005

본 논문은 대단위 아파트를 주 대상으로 서울 7개소, 경기도 7개소, 강원도 10개소, 충청도 6개소, 총 30개소에 대한 승강기설비 전원품질을 측정하고 역률 변화, 고조파, 전압변동, 전압강하 등을 분석하였다. 분석결과 승강기설비 제어반 인입구에서의 실제역률(TPF)과 기본역률(DPF)의 차이가 고조파로 인하여 크게 나타나는 것을 확인하였고, 역률의 변화는 전원측(변압기)에 가까워질수록 작아지는 것을 확인하였다. 전압 종합왜형률(VTHD)은 안정적이지만 전류 종합왜형률(CTHD)은 기준치 이상의 매우 높은 수치가 발생되었고, 전원측(변압기)에 가까워질수록 작아지는 것을 확인하였다. 승강기설비 제어반 인입구에서의 전압강하율은 기준치 5%를 상회하고 있으나, 전압변동률은 최대 5.1%로서 기준치 10% 범위에 포함되었다.

• Journal of KIISE
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• v.44 no.6
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• pp.601-606
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• 2017

Recently, we have frequently encountered flying drones with the growth of drone industry. However, it is difficult for a driver to stabilize the motor speed of drones, since the voltage of a Lithium polymer battery used in drones may suddenly drop or rise when its power is exhausted. The instability of the motor speed precludes the drone from maintaining a flight altitude, so that the fuselage of a drone performs ascending and descending repeatedly. For solving this problem, existing techniques either add a compensator considering voltage drop of battery or change the control model. Since these techniques use hardware-implemented modules or depend on motor type and experimental results, there is a problem that new suitable modules should be implemented in accordance with the used motor of the fuselage. For solving this problem, in this paper, we implement a motor speed controller in the firmware of drones by considering voltage drop of battery to enhance drone flight stability.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.137-138
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• 2006

2005년 3월에 개시된 개성시범공단에 대한 남한으로부터의 전력공급은 우선 22.9kV 배전 방식으로 최대 15MW까지 확보되고 있으며 금년 말까지 154kV송전선이 건설되어 100MW 전력을 개성공단의 완공에 대비하여 공급할 것으로 알려지고 있다. 한편 정부는 작년 7월에 중대발표를 통하여 2GW의 대북 송전을 제안해 놓고 있으나 6자회담의 교착상태로 논의가 중단된 상태에 있다. 본 연구에서는 이상의 두 가지 경우를 연관시켜 기술적/경제적 측면에서 가장 현실적으로 타당하다고 판단되는 몇 개의 대안에 대하여 조류계산, 전압강하, 과도안정도 및 전압안정도 문제 등을 분석하여 주로 남한의 수도권 전력수급 안정에 미치는 영향을 검토하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.4
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• pp.1-8
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• 1985

Stability analysis of the embankment as to water level varation is the most important problem in the safety of the slope because the stress of embankment inside varies as to drawdown of seepage line. Especially when the water level is rapidly drawdown, because the flow direction of the free surface changes the toe of embankment, the factor of safety comes to small, therefore the embankment is dangered. For the purpose of studing these phenomena, the experimental models are built with sand in the laboratory. In the experimental consideration, the falling seepage line and the shape of failure are measured. This paper intends to study the failure slip surface, the relationship between the factor of safety and drawdown velocity, and hydraulic gradient. The results of the experimental study are summarized as follows; 1. Owing to the drawdown of free surface, sliding failure occurred in the upstream fill, the height of failure is 5~10, 9~15, and 13~21(cm) in each model. 2. In consideration of the distribution of pore water pressure Table-5 shows each factor of safety. In the relationship between the drawdown velocity and the factor of factor it's velocity should be limited to 0.21~0.28 (cm/sec), according to each models. In the relationship between the factor of safety and the hydraulic gradient within the upstream slope, it's gradient must be below 0.36~0.43.

• Korean Journal of Environment and Ecology
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• v.34 no.3
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• pp.191-197
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• 2020

The purpose of this was to examine the differences of large whopper swan (Cygnus cygnus) in wintering habitat preference among bridge sections of the lower Nakdong River of the Nakdong River Estuary, the largest whopper swan's wintering habitat in Korea. This species is designated and protected as Natural Monument in Korea. The survey was conducted in six time-series during the 2018~2019 wintering season, and it found up to 500 whopper swans were wintering in the lower Nakdong River. For the survey, a seven sections were set up based on the bridges across the river. Whopper swans were rarely observed in five narrow sections where the distance between bridges was less than 2 km. The stable population of the whopper swan was observed only in two broader sections where the distance between bridges was is over 4 km. As these sections were relatively little affected by artificial interference, the distance from the mouth of the Nakdong River was not a factor. Securing a stable space is considered as one of the most important factors for wintering of whopper swans, which are an endangered species. The survey results indicate that the distance between bridges should be at least 4 km to secure the whopper swan's stable habitat. These results are expected to be a reference to the development or restoration of the river ecosystems, especially bridge construction.