• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1110-1122
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• 2018

This paper proposes an alternative method to evaluate the effect of wind power to the power system stability with small disturbance. Alternatively, available techniques for stability analysis of a power system based on deterministic methods are less accurate for high penetration of wind power. Numerical simulations of random behaviors are computationally expensive. A stochastic stability index (SSI) is proposed for the power system stability evaluation based on the theory of stochastic stability and energy function, specifically the stochastic derivative of the relative well-defined energy function and the critical energy. The SSI is implemented on the modified nine-bus system including wind turbines under different conditions. A doubly-fed induction generator (DFIG) wind turbine is characterized and modeled using measured wind data from several sites in Thailand. Each of the obtained wind power data is analyzed. The wind power effect is modeled considering the aggregated effect of wind turbines. With the proposed method, the system behavior is properly predicted and the stability is quantitatively evaluated with less computational effort compared with conventional numerical simulation methods.

• 전기전자학회논문지
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• 제22권3호
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• pp.829-835
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• 2018

기존의 전력 시스템에서 불필요하게 생성되거나 낭비되는 예비전력을 감소시키고 에너지 사용 효율을 개선하기 위한 연구가 최근 활발히 진행되고 있다. 본 연구에서는 전기기기들의 전원 제어를 통한 에너지 사용 효율을 개선하기 위해 스마트그리드의 요소 기술 중 하나인 스마트미터기를 개발하며, 실시간으로 측정된 전력 사용량을 딥 러닝을 통해 전력 사용량의 트렌드를 분석 및 예측한다. 이후 예측된 전력 사용량과 실시간 전력 사용량을 비교하여 전기기기들의 전원을 제어하는 알고리즘을 제안 및 개발한다. 제안한 딥 러닝 기반의 스마트미터기의 성능을 확인하기 위해서 실제 전력 소비 환경을 구축하였고, 실시간으로 전력 사용 데이터를 확보하여 딥 러닝 모델에 학습시킨 뒤 전력 사용량을 예측하였다. 예측된 값과 실제 사용량을 실시간으로 비교하여 예측을 벗어난 기기들의 전원을 제어하여, 전력 사용량을 감소시키고 에너지 사용 효율이 개선되는 결과를 확인하였다.

• 한국철도학회논문집
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• 제20권5호
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• pp.595-601
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• 2017

전철화 확대의 영향으로 전차선로 변의 고장발생 빈도는 지속적으로 증가하여, 고장위치를 표정하는 시스템의 중요도는 향상되고 있다. 그럼에도 전차선로의 정확한 고장위치 표정은 매우 어려운 현실이다. 본 논문에서는 기존 회로방정식으로 제안된 전차선로 임피던스 계산이론에 대해 현장실측 데이터를 활용하여 보편화 정리하고 변전소 및 운행차량의 전압, 전류 데이터를 동기화 실측하여 전차선로의 임피던스를 예측 하였다. 또한 예측된 전차선로 임피던스값의 유효성 확인을 위해 동일지점에서 열차전류에 따른 임피던스 변화 정도를 시뮬레이션으로 확인하였다. 끝으로 측정 데이터와 지락시험을 통한 데이터를 비교 분석하였다. 본 기법은 강제지락시험, 인공지락시험을 통해 임피던스를 예측하는 현행 방식 대비 열차운행 중단 없이 다수의 데이터를 확보할 수 있고 시간경과에 따른 임피던스 변화에 대해서도 신속하고 편리하게 대응할 수 있는 장점이 있는 것으로 판단된다.

• 한국BIM학회 논문집
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• 제9권3호
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• pp.19-29
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• 2019

Currently, BIPV (Building Integrated Photovoltaic) design technology lacks analysis function at the planning stage, and there is a lack of understanding and reliability of BIPV design method and system for building designers. To design and consider various building integrated solar design alternatives, the color of building integrated solar is often monotonous or does not match the design direction of the building. In this study, architectural designers can select various color modules in the planning and design process of the building and analyze the characteristics of color module solar cells and compare and analyze the actual solar radiation and predicted solar radiation in Republic ofKorea Seoul to reduce the confusion of design methods. By building a BIM design integrated system that can prove the quality of the building and analyze the shading analysis and power generation performance architecturally, it can improve the reliability of color module solar cell applicability that can express aesthetics in buildings and the predicted solar power generation capacity of each region. In the initial design stage, based on the empirical data of the BIPV system, it is possible to analyze the power generation performance for each installation angle and installation direction by analyzing the surrounding environment and the installation area, and accurately determine the appropriateness of the design accordingly.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제12권6호
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• pp.251-258
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• 2023

안정적으로 전력을 공급하고 전력계통을 운영하기 위해서는 최대전력을 정확히 예측해야 한다. 특히, 최대전력이 높게 발생하는 겨울과 여름에는 그 중요성이 매우 커진다. 최대전력을 실제 수요보다 높게 예측하면 발전소 기동 비용이 증가하여 경제적 손실이 발생하고, 최대전력을 실제 수요보다 낮게 예측하면 기동이 가능한 발전소가 부족하여 정전이 발생할 수 있다. 최대전력의 예측 오차를 최소화함으로써 경제적 손실과 정전을 예방할 수 있다. 본 논문에서는 최대전력 예측의 오차를 최소화하기 위하여 최신 딥러닝 모델인 TCN을 이용한다. 딥러닝 모델은 하이퍼 파라미터를 어떻게 설정하느냐에 따라 성능 차이가 발생하므로, TCN의 하이퍼 파라미터를 최적화하는 방법을 제안한다. 2006년부터 2021년까지의 데이터를 입력하여 모델을 훈련하고, 2022년의 데이터를 이용하여 예측 오차를 실험하였다. 실험을 수행한 결과 본 논문에서 제안한 최적화 방법을 이용한 TCN 모델의 성능이 다른 딥러닝 모델보다 성능이 우수한 것을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제13권4호
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• pp.1566-1577
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• 2018

This paper presents a stability analysis of AC-DC power system feeding a speed controlled DC motor in which this load behaves as a constant power load (CPL). A CPL can significantly degrade power system stability margin. Hence, the stability analysis is very important. The DQ and generalized state-space averaging methods are used to derive the mathematical model suitable for stability issues. The paper analyzes the stability of power systems for both speed control natural frequency and DC-link parameter variations and takes into account controlled speed motor dynamics. However, accurate DC-link filter and DC motor parameters are very important for the stability study of practical systems. According to the measurement errors and a large variation in a DC-link capacitor value, the system identification is needed to provide the accurate parameters. Therefore, the paper also presents the identification of system parameters using the adaptive Tabu search technique. The stability margins can be then predicted via the eigenvalue theorem with the resulting dynamic model. The intensive time-domain simulations and experimental results are used to support the theoretical results.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2006년도 제33회 KOSCO SYMPOSIUM 논문집
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• pp.187-195
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• 2006

In this work, we introduce a newly constructed arc-jet device of 150 kW input power. The design of this device is a Huels type with a narrow downstream electrode. General features of this device are first described. From the measured values of electrical power input, heat discharged into cooling water, gas flow rate, and settling chamber pressure, average enthalpy was determined using the heat balance and sonic throat methods. Using the settling chamber pressure and average enthalpy values, the flow properties in the nozzle and the heat transfer rate to the stagnation point of a blunt body are calculated accounting for thermochemical nonequilibrium. The envelope of enthalpy, pressure, degree of dissociation, and heat transfer rate are presented. Stagnation temperature is predicted to be between 4630 to 6050 $^{\circ}K$, and the stagnation point heat transfer rate is predicted to be between 175 and 318 W/$cm^{2}$ for a blunt body of 3 mm nose radius. Degree of dissociation in the stagnation region of the blunt body exceeds 30%.

• 전기학회논문지
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• 제57권3호
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• pp.375-383
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• 2008

This paper deals with reduction and analysis of cogging torque for permanent magnet synchronous generators with multi-pole rotor for wind power applications. Open-circuit field solutions are derived using a magnetic vector potential and a two-dimensional (2-d) polar coordinate systems. On the basis of derived open-circuit field solutions and 2-d permeance functions, we also derive open-circuit field solutions considering stator slotting effects. By using open-circuit field solutions considering stator slotting effects and energy variation methods, this paper analytically predicts the cogging torque considering skew effects. All analytical results are shown in good agreement with those obtained from finite element (FE) analyses. In order to reduce the cogging torque, by predicting the variation of the cogging torque according to pole arc/pitch ratio using analytical and FE methods, pole arc/pitch ratio which makes the cogging torque minimum are determined. However, we confirm that measured value for cogging torque of the PMG with determined pole arc/pitch ratio is twice higher than predicted value. Therefore, the reason for an error between measured and predicted cogging torque is discussed in terms of a shape of PMs and is proved experimentally.

• 한국대기환경학회지
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• 제13권6호
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• pp.427-437
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• 1997

Complex terrain which is rather typical topographic character in Korea would greatly influence the dispersion of air pollutant. In this study, we investigated how the complex terrain in the vicinity of the coal-fired plant affects the air dispersion modeling results by using several US EPA models: SCREEN, CTSCREEN, ISCLT3, ISCST3, and RTDM. Screening analysis was followed by long-term analysis, and the plume movement over the terrain was precisely tracked for selected cases. Screening analysis revealed that the highest concentration of sulfur dioxide occurs at the downwind distance of 1.3 km under the unstable conditions with weak winds. However, this highest level of $SO_2$ could be raised by 4 times even in the presence of a hill of 170 m at a distance of 2 to 3 km. Seasonal and annual average concentrations predicted with the ISCLT3, ISCST3, and RTDM models showed a rapid incrase of $SO_2$ levels in front of the high mountains which are located more than 15 km away fromt the source. The highest concentrations predicted with ISCST3 were significantly higher than those with ISCLT3 and RTDM mainly because ISCST3 chooses simple-terrain model calculations for receptors between stack height and plume height. Although the highest levels under the stable conditions were usually found in the areas beyond 15 km or more, their absolute values were not so high due to enough dispersion effects between the source and the receptors.

• Journal of Biosystems Engineering
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• 제35권1호
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• pp.1-9
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• 2010

A mathematical model was developed to predict the fuel consumption rate consumed by agricultural tractors under arbitrary loaded conditions. The model utilizes the measured data on the fuel consumptions at the full load and at the rated engine speed with partial loads, which can easily be obtained from the official OECD tractor test reports. It was found from the analysis of the measured fuel consumption data that the fuel consumptions at two different speeds does not change with power. The model was developed based on this fact and validated with the measured data of the 159 tractor test reports. The fuel consumptions predicted by the model were compared with those measured under the partially loaded conditions specified in the official OECD tractor test code II. The percent errors of the predicted fuel consumptions were in a range from 0.36 to 2.86% which assured that the developed fuel consumption model can be used practically to predict the fuel consumptions at any speed and power combinations. It was also shown that the developed model predicts the fuel consumption rate better than the Grisso's model.