• 설비공학논문집
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• 제12권11호
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• pp.1004-1011
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• 2000

Experimental and computational studies were carried out to confirm the turbulent enhancement of the cooling system of nuclear reactor by large scale vortex generation in nuclear fuel bundle. The large scale vortex motions were generated by rearranging the inclination angles of mixing vanes to the coordinate directions. Axial development of mean and turbulent velocities in the subchannels were measured by the 2-color LDV system. Eddy diffusivity heat flux model and $k-varepsilon$ model were employed to analyze the turbulent heat and fluid flows in the subchannel. The turbulence generated by split mixing vanes has small length scales so that they maintain only about $10 D_H$ after the spacer grid. On the other hand, the turbulences generated by the large scale vortex continue more and remain up to $25 D_H$after the spacer gird.

• 한국초전도ㆍ저온공학회논문지
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• 제13권3호
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• pp.14-18
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• 2011

Electrical system is changing to smart grid which includes the distributed generations with reusable energy sources in these days. The distributed generations are environmentally friendly and have no concern with depletion problem. But dispatching distributed generations can cause an increase of the fault current. Resistive type super conducting fault current limiter is one of the candidates of solution for the large fault problem in smart grid. In this paper, a design method for the wire length of fault current limiter and the result of short circuit test for small scale modules considering system resistance are introduced.

• 전기학회논문지
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• 제63권10호
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• pp.1402-1411
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• 2014

In this paper, the Maximum Power Point Tracking(MPPT) control of the small scale wind power generation system with a three-phase diode rectifier and the grid-connected inverter is studied. Without the need for the converter circuits to control speed of the generator, it is economical and the structure is simple. Compared with existing systems, it can be to reduce the power semiconductor switches and passive elements, and to implement the MPPT control with only DC-Link voltage control of the grid-connected inverter. In order to allow MPPT control without the characteristic information of the wind turbine, the P&O algorithm is applied, and these are verified by the simulation and experiment.

• Journal of Electrical Engineering and Technology
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• 제9권1호
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• pp.60-70
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• 2014

This paper discusses the impacts of large scale grid-connected wind farm equipped with permanent magnet synchronous generator (PMSG) on power system small signal stability (SSS) incorporating wind generation uncertainty and volatility. Firstly, a practical simplified PMSG model with rotor-flux-oriented control strategy applied is derived. In modeling PMSG generator side converter, the generator-voltage-oriented control strategy is utilized to implement the decoupled control of active and reactive power output. In modeling PMSG grid side converter, the grid-voltage-oriented control strategy is applied to realize the control of DC link voltage and the reactive power regulation. Based on the Weibull distribution of wind speed, the Monte Carlo simulation technique based is carried out on the IEEE 16-generator-68-bus test system as benchmark to study the impacts of wind generation uncertainty and volatility on small signal stability. Finally, some preliminary conclusions and comments are given.

• Journal of Magnetics
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• 제16권4호
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• pp.379-385
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• 2011

This paper presents an optimal design of a direct-drive permanent magnet synchronous generator for a small-scale wind energy conversion system. An analytical model of a small-scale grid-connected wind energy conversion system is presented, and the effects of generator design parameters on the payback period of the system are investigated. An optimization procedure based on genetic algorithm method is then employed to optimize four design parameters of the generator for use in a region with relatively low wind-speed. The aim of optimization is minimizing the payback period of the initial investment on wind energy conversion systems for residential applications. This makes the use of these systems more economical and appealing. Finite element method is employed to evaluate the performance of the optimized generator. The results obtained from finite element analysis are close to those achieved by analytical model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1058-1059
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• 2015

This paper describes a low-voltage ride-through method for the permanent magnet synchronous generator (PMSG) wind turbine system at a grid fault. The generator side converter regulates the DC link voltage instead of the grid side converter by storing the surplus active power in the rotor inertia during grid fault by the sliding mode controller. The grid side converter controls the grid active power keeping a maximum power point tracking. Simulation results for small scale PMSG wind turbine verify the efficiency of the control method.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1163-1170
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• 2014

Due to global environmental regulations and policies with rapid advancement of renewable energy technologies, the development type of renewable energy sources (RES) in power systems is expanding from small-scale distributed generation to large-scale grid-connected systems. In the near future, it is expected that RES achieves grid parity which means the equilibrium point where the power cost of RES is equal to the power costs of conventional generators. However, although RES would achieve the grid parity, the cost related with development of large-scale RES is still a big burden. Furthermore, it is hard to determine a suitable capacity of RES because of their output characteristics affected by locations and weather effects. Therefore, to determine an optimal capacity for RES becomes an important decision-making problem. This study proposes a method for determining an optimal installed capacity of RES from the business viewpoint of an independent power plant (IPP). In order to verify the proposed method, we have performed case studies on real power system in Incheon and Shiheung areas, South Korea.

• 한국환경과학회지
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• 제4권2호
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• pp.159-168
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• 1995

To predict reasonably the movement and the concentration of the pollutants in the coastal area. A simulation model should be prepared considering detail topography with land-sea and the urban effects, and the resolution near the source. The explicit method can not be applied due to the instability of the numerical calculation in high horizontal-grid resolution, while the ADI scheme satisfied with the high horizontal grid resolution and can be used in the fine mesh system which shows the detail topography, atmospheric flow The ADI method which studied the high horizontal grid resolution was excellent. The two dimensional model used in the study using ADI method is proved as a reasonable model to predict the wind field in any small scale area including mountainous coastal urban area.

• 융합신호처리학회논문지
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• 제25권2호
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• pp.94-99
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• 2024

최근 들어 풍력 발전은 신재생 에너지 중에서 높은 효율을 가진 에너지원으로 주목받고 있으며, 이에 따라 전 세계적으로 다양한 기술 개발이 진행되고 있다. 일반적으로 풍력 발전은 풍력 자원이 풍부한 지역에 많은 풍력터빈을 설치하여 운영하는 대형 풍력 농장(Big Wind Farm) 형태로 운영되고 있으나 개발 도상국이나 전력망에서 고립된 지역에서는 오프-그리드(Off-Grid) 형태의 소형 풍력 발전 시스템이 효율적인 솔루션으로 부상하고 있다. 오프-그리드(Off-Grid) 형태의 소규모 발전 시스템을 효율적으로 운영하고 확산시키기 위해서는 실시간 모니터링 시스템의 개발이 요구된다. 소규모 풍력 발전 시스템 구성을 위해 과다한 풍속으로 인한 손상 방지 체계 및 다양한 환경적 요소에 능동적으로 대처하기 위한 실시간 발전소 운영 모니터링 체계 그리고 생산된 전력을 안정적으로 소규모 지역이나 시설에 공급하기 위한 ESS(Energy Storage System) 시스템에 대해 연구하였다. 구현된 시스템은 터빈의 RPM, 발전량, 브레이크 동작, 발전량 등을 모니터링하여 최적 운영환경이 조성되도록 하였다. 구현된 소형 풍력발전 체계는 격오지 도로 조명, 해양 레저 시설, 모바일 통신 기지국 등에 활용될 수 잇으며 RE100 산업 생태계 발전에 기여할 수 있을 것이다.

• 한국측량학회지
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• 제17권2호
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• pp.97-104
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• 1999

수치표고모델(DEM)은 정사영상 제작을 위한 중요한 기초 자료이며, 품질은 대상 점 또는 선형요소의 기하학적 정확도에 의존하게 된다. 따라서 본 연구에서는 격자의 간격과 스캐닝 해상도를 달리하며 상관매칭에 의해 수치표고모델 생성을 시도하였다. 실험결과 추출점의 격자간격이 작을수록 표준편차가 가장 작게 나타났으며 스캐닝의 해상도는 큰 영향이 없는 것으로 나타났다. 또한 수치표고모델에 대한 편이량 분석결과 소축척에 비해 대축척의 항공사진에서 편이가 크게 발생되었으며 이는 폐쇄영역이 가장 큰 영향 요소임을 알 수 있었다. 이러한 패쇄영역을 줄이기 위하여 다축척 영상의 이용과 종 중복도를 증가시키며 실험한 결과 한 쌍의 입체영상보다 다중영상을 이용한 경우 음영 및 폐쇄영역의 크기를 대폭 감소시킬 수 있는 것으로 나타났다.