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Reactive Power P&O Anti-Islanding Method for a Grid-Connected Inverter With Critical Load
Park, Sungyoul,Kwon, Minho,Choi, Sewan Institute of Electrical and Electronics Engineers 2019 IEEE transactions on power electronics Vol.34 No.1
<P>A grid-connected inverter with critical loads should be able to supply a stable voltage to critical loads at the instant of a mode change as well as during clearing time while quickly detecting unintentional islanding. The indirect current control has been proposed to provide not only a stable voltage to critical loads during clearing time but also a seamless transfer of inverters at the instant of a mode change. However, the conventional islanding detection methods cannot be applied to the indirect current control based inverter since the magnitude and frequency of voltage do not vary when an islanding occurs. This paper proposes a reactive power P&O anti-islanding method for the indirect current control. The proposed islanding detection method generates a small reactive power perturbation at the output of the inverter and detects the islanding by observing reactive power mismatch during the islanding. Using the proposed method, the inverter can supply high quality power to critical loads without distorting the output current during the clearing time. The proposed anti-islanding method is validated through simulation and experimental results.</P>
A Seamless and Autonomous Mode Transfer Method of Grid-connected Inverter with Critical Load
Sungyoul Park,Sewan Choi,Minho Kwon 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
A grid-connected inverter with critical loads should be able to supply a stable voltage to critical loads at the instant of a mode change as well as during clearing time while detecting unintentional islanding. This paper proposes a mode transfer method for a grid connected inverter with the critical loads. The proposed method, which integrates grid-connected mode control loop and islanded mode control loop into one control block, provides autonomous and seamless mode transfer from the current control to voltage control. Therefore, the proposed schemes can supply a stable voltage to critical loads at the mode change instant as well as during the clearing time. To validate the proposed method, experimental results are provided.
대학의 실시간 온라인수업에서 학습성취도와 학습만족도에 대한 촉진요인 분석
박성열(SungYoul Park),주민호(Min-Ho Joo),이대영(DaeYeong Lee) 학습자중심교과교육학회 2021 학습자중심교과교육연구 Vol.21 No.11
목적 본 연구는 대학의 실시간 온라인수업에서 학습성과에 영향을 미치는 요인들을 파악하고, 변인 간 차이를 분석함으로써 향후 전개될 실시간 온라인수업의 효과적인 대응 전략을 수립하고 시사점을 제시하는 데 목적이 있다. 방법 이를 위하여 K대학 재학생 354명을 대상으로 이러닝 자기효능감, 실재감, 지각된유용성, 혁신저항, 시스템품질, 학습만족도, 학습성취도에 대해서 설문조사를 실시하였다. 수집된 자료는 데이터 코딩 후 SAS version 9.4를 이용하여 기술통계, 신뢰도, 상관관계 및 다중회귀분석을 실시하였다. 결과 첫째, 학습만족도에 대한 다중회귀분석 결과 모든 변인이 정적인 회귀계수로 촉진요인임을 확인하였으며, 이들 중 유의한 변인은 지각된유용성, 혁신저항, 시스템품질로 밝혀졌다. 둘째, 학습성취도에 대한 다중회귀분석 결과 모든 변인이 정적인 회귀계수로 촉진요인임을 확인하였으며, 이들 중 유의한 변인은 실재감, 지각된유용성, 혁신저항, 시스템품질로 밝혀졌다. 셋째, 학습만족도와 학습성취도의 다중회귀식을 비교한 결과 이러닝 자기효능감은 두 회귀식에서 모두 유의하지 않은 변인이었으나, 실재감의 경우 학습성취도에서만 유의하였다. 마지막으로 모든 연구결과에서 지각된유용성 변인이 실시간 온라인수업의 학습성과에 미치는 영향력이 가장 큰 촉진요인으로 드러났다. 결론 따라서 학습자의 지각된유용성을 증진시키기 위한 전략을 모색할 필요성이 있을 것으로 보인다. Objectives The purpose of this study is to verify the factors affecting learning outcomes in synchronous online classes, to analyze the differences between variables to establish effective response strategies for synchronous online classes at colleges. Methods A questionnaire survey was conducted on 354 students at K University for e-learning self-efficacy, presence, perceived usefulness, innovation resistance, system quality, learning satisfaction, and learning achievement. After data coding, the collected data were statistically analyzed by descriptive statistics, reliability, correlation analysis, and multiple regression analysis using SAS version 9.4. Results First, it was proven that all variables were facilitating factors, among which significant variables were identified to be perceived usefulness, innovation resistance, and system quality through the multiple regression analysis results of learning satisfaction. Second, it was identified that all variables were also facilitating factors, among which significant variables were identified to be the presence, perceived usefulness, innovation resistance, and system quality through the multiple regression analysis results of learning achievement. Third, in the result of comparing the multiple regression equations of learning satisfaction and achievement, e-learning self-efficacy was not a significant variable in both regression equations, but the presence was only significant in learning achievement. Lastly, of all the results, the perceived usefulness was identified as the biggest facilitator affecting learning outcomes. Conclusions It seems to find strategies to enhance the perceived usefulness of learners.
레이저 스캐너 기반 건설장비 작업환경 모니터링 기술 개발
박성렬(Sungyoul Park),오광석(Kwangseok Oh),박진선(Jin Sun Park),김진균(Jin-Gyun Kim),서자호(Jaho Seo),이근호(Geun Ho Lee),이경수(Kyongsu Yi) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Currently, the interests on safety of heavy machinery operation is highly increasing due to growth of construction accidents caused by inexperienced operator, worker’s carelessness, and so on. Therefore, the demand of the automation technology on construction machinery comes to the fore. This paper presents an environment monitoring technology of working site for construction machinery based on laser scanner. The proposed monitoring systems consists two parts. The first part is environmental perception based on one-layer laser scanner processing which estimates object states and classifies. The second part is working area estimation and prediction by analyzing position and velocity kinematics of excavator. It is shown that the proposed working area monitoring technology enhances environment perception performance and safety of construction site.