• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1052-1053
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• 2015

풍력발전기의 대용량화와 전력변환장치를 이용한 출력 안정화로 인하여 그리드 코드에서는 상정 사고 시 풍력발전기를 탈락시키지 않고 전압제어에 참여하도록 요구하고 있다. 풍력발전단지의 전압제어참여는 크게 단지 레벨과 발전기 레벨로 나누어지며, 개별풍력발전기가 단지 급 제어기로부터 무효전력 지령신호를 받아 필요량을 출력하는 구조이다. 따라서 풍력발전단지와 기존발전기 및 FACTS 설비와의 협조제어 알고리즘 연구에 앞서 개별풍력발전기의 전압제어특성에 대한 선행연구가 필요하다. 풍력발전기는 상정사고 시 전압강하가 크게 발생하는 경우 전압제어 Slope 특성을 이용하여 무효전력출력량을 산정하여 제어하도록 구성되어있다. 본 논문에서는 서로 다른 무효전력 출력 전압제어 Slope를 갖는 영구 자석형 풍력발전기의 출력특성에 대하여 모의하였으며, 해외 독일 Grid Code인 E.ON 및 SDLWindV에서 제안하는 전압데드밴드 변경 및 K_slope 변경을 통해 풍력발전기가 전압제어에 효과적으로 참여하여 전압강하가 개선됨을 증명하였다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 추계학술대회
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• pp.241-244
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• 2006

The present paper describes the scale effect correction method for wind turbine by using CFD(computational fluid dynamics). For the correct ions of wind turbine scale effect, various researches on the helicopter rotor scale effect were Investigated and feasibility study of methods was performed to correct wind turbine scale effect The present paper also introduces new scale effect correction method based on two dimensional lift slope modification. In order to test the Present method, performance analyses of NREL Phase VI wind turbines under various scale conditions were carried out by using CFD. The present method showed reasonable results when applied to NREL Phase VI wind turbine.

• Wind and Structures
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• 제5권1호
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• pp.1-14
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• 2002

Artificial Neural Networks (ANN) have the capability to develop functional relationships between input-output patterns obtained from any source. Thus ANN can be conveniently used to develop a generalised relationship from limited and sometimes inconsistent data, and can therefore also be applied to tackle the data obtained from wind tunnel tests on building models with large number of variables. In this paper ANN model has been developed for predicting wind induced pressures in various zones of a Gable Building from limited test data. The procedure is also extended to a case wherein interference effects on a gable roof building by a similar building are studied. It is found that the Artificial Neural Network modelling is seen to predict successfully, the pressure coefficients for any roof slope that has not been covered by the experimental study. It is seen that ANN modelling can lead to a reduction of the wind tunnel testing effort for interference studies to almost half.

• Journal of electromagnetic engineering and science
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• 제18권2호
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• pp.136-140
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• 2018

We propose an improved semi-empirical scattering model for X-band radar backscattering from rough sea surfaces. This new model has a wider validity range of wind speeds than does the existing semi-empirical sea spectrum (SESS) model. First, we retrieved the small-roughness parameters from the sea surfaces, which were numerically generated using the Pierson-Moskowitz spectrum and measurement datasets for various wind speeds. Then, we computed the backscattering coefficients of the small-roughness surfaces for various wind speeds using the integral equation method model. Finally, the large-roughness characteristics were taken into account by integrating the small-roughness backscattering coefficients multiplying them with the surface slope probability density function for all possible surface slopes. The new model includes a wind speed range below 3.46 m/s, which was not covered by the existing SESS model. The accuracy of the new model was verified with two measurement datasets for various wind speeds from 0.5 m/s to 14 m/s.

• 대한원격탐사학회지
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• 제37권6_2호
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• pp.1837-1847
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• 2021

본 연구는 지리정보시스템과 전산유체역학 모델을 이용하여 수원시 전역을 대상으로 바람길을 조사하였다. 최근 10년간 수원 종관기상관측소(ASOS 119)에서 측정한 평균 풍속을 이용하여 16방위의 유입 풍향에 대한 수치 모의를 수행하였다. 수원시는 산악 지형으로 둘러싸인 분지에 위치하고, 수원시 서부와 남부에는 장애물이 적은 농경지와 호수 평지가 넓게 분포하고 있다. 수원시 중부에는 낮은 산과 언덕이 곳곳에 산재하고 있고, 넓은 도로들과 하천이 길게 형성되어 있다. 서풍(주풍)과 동풍(평균 풍속이 강한 풍향) 경우를 상세하게 분석하고 16방위 풍향 빈도수를 가중치로 사용하여 평균한 풍속 분포 특성을 분석하였다. 수원시의 상세 바람특징을 다음과 같이 요약할 수 있다. (1) 수원 북부 지역은 높은 산악 지형에 의해 복잡한 흐름이 형성되었고, 풍상측(풍하측) 산사면에서 강한(약한) 바람과 상승(하강)기류가 모의되었다. (2) 풍하측 산사면에서는 골짜기를 따라 바람길이 형성되어 주거지역으로 비교적 강한 기류가 유입되었다. (3) 강풍 지역이 수원 서부와 남부의 장애물이 없는 넓은 지역에서 모의되었다. (4) 도심지에서는 건물에 의한 마찰과 흐름 차단으로 인해 풍속이 감소하고 복잡한 흐름장이 형성되었다. 도심지 주거 지역의 바람길은 넓은 도로와 하천, 호수, 저수지 등 장애물이 적은 지역을 따라 형성되었다.

• 한국융합학회논문지
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• 제4권4호
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• pp.49-57
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• 2013

The lightning shielding of different 500 kV HVAC-TL high voltage AC transmission lines was analyzed. The studied transmission lines were horizontal flat single circuit and double circuit transmission lines. The lightning attractive areas were drawn around power conductors and shielding wires. To draw the attractive areas of the high voltage transmission lines, transmission line power conductors, shielding wires and lightning leader were modeled. Different parameters were considered such as lightningslope, ground slope and wind on lightning attractive areas. From the calculated results, the power conductors voltages affected on attractive areas around power conductors and shielding wires. For negative lightning leader, the attractive area around the transmission line power conductor increased around power conductors stressed by positives voltage and decreased around power conductors stressed by negative voltage. In spite of this, the attractivearea of the transmission line shielding wire increasedaround the shielding wire above the power conductor stressed by the positive voltage and decreased around the shielding wire above the power conductor stressed by negative voltage. The attractive areas around power conductors and shielding wires were affected by the surrounding conditions, such as lightning leader slope, ground slope. The AC voltage of the transmission lines made the shielding areas changing with time.

• Wind and Structures
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• 제19권2호
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• pp.219-232
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• 2014

The characteristics of turbulent boundary layers over hilly terrain depend strongly on the hill slope and upstream condition, especially inflow turbulence. Numerical simulations are carried out to investigate the neutrally stratified turbulent boundary layer over two-dimensional hills. Two kinds of hill shape, a steep one with stable separation and a low one without stable separation, two kinds of inflow condition, laminar turbulent, are considered. An auxiliary simulation, based on the local differential quadrature method and recycling technique, is performed to simulate the inflow turbulence be imposed at inlet boundary of the turbulent inflow, which preserves very well in the computational domain. A large separation bubble is established on the leeside of the steep hill with laminar inflow, while reattachment point moves upstream under turbulent inflow condition. There is stable separation on the side of low hill with laminar inflow, whilw not turbulent inflow. Besides increase of turbulence intensity, inflow can efficiently enhance the speedup around hills. So in practice, it is unreasonable to study wind flow over hilly terrain without considering inflow turbulence.

• 신재생에너지
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• 제7권2호
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• pp.43-50
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• 2011

The only practical way to measure wind resource at high-altitude over 100 m above ground for a feasibility study on a high-rise building integrated wind turbine might be ground-based remote sensing. The remote-sensing campaign was performed at a 145 m-building roof in Jamsil where is a center of metropolitan city Seoul. The campaign aimed uncertainty assessment of Leosphere WindCube LIDAR and Scintec MPAS SODAR through a mutual comparison. Compared with LIDAR, the data availability of SODAR was about 2/3 at 550 m altitude while both showed over 90% under 400 m, and it is shown that the data availability decrease may bring a distortion of statistical analysis. The wind speed measurement of SODAR was fitted to a slope of 0.92 and $R^2$ of 0.90 to the LIDAR measurement. The relative standard deviation of wind speed difference and standard deviation of wind direction difference were evaluated to be 30% and 20 degrees, respectively over the whole measurement heights.

• 한국태양에너지학회 논문집
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• 제31권2호
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• pp.63-71
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• 2011

The remote-sensng campaign was performed at the Pohang Accelerator Laboratory where is located in a basin 6km inland from Yeongil Bay. The campaign aimed uncertainty assessment of Remtech PA0 SODAR through a mutual comparison with WindCube LIDAR, the remote-sensing equipment for wind resource assessment. The joint observation was carried out by changing the setup for measurement heights three times over two months. The LIDAR measurement was assumed as the reference and the uncertainty of SODAR measurement was quantitatively assessed. Compared with LIDAR, the data availability of SODAR was about half. The wind speed measurement was fitted to a slope of 0.94 and $R^2$ of 0.79 to the LIDAR measurement. However, the relative standard deviation was about 17% under 150m above ground level. Therefore, the Remtech PA0 SODAR is judged to be unsuitable for the evaluation of wind resource assessment and wind turbine performance test, which require accuracy of measurement.

• Wind and Structures
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• 제36권2호
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• pp.75-90
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• 2023

Turbulent wind flow over hilly terrains has been extensively investigated in the scientific literature and main findings have been included in technical standards. In particular, turbulent wind flow over nominally two-dimensional hills is often adopted as a benchmark to investigate wind turbine siting, estimate wind loading, and dispersion of particles transported by the wind, such as atmospheric pollutants, wind-driven rain, windblown snow. Windblown sand transport affects human-built structures and natural ecosystems in sandy desert and coastal regions, such as transport infrastructures and coastal sand dunes. Windblown sand transport taking place around any kind of obstacle is rarely in equilibrium conditions. As a result, the modelling of windblown sand transport over complex orographies is fundamental, even if seldomly investigated. In this study, the authors present a wind-sand tunnel test campaign carried out on a nominally two-dimensional sinusoidal hill. A first test is carried out on a flat sand fetch without any obstacle to assess sand transport in open field conditions. Then, a second test is carried out on the hill model to assess the sand flux overcoming the hill and the morphodynamic evolution of the sand sedimenting over its upwind slope. Finally, obtained results are condensed into a dimensionless parameter describing its sedimentation capability and compared with values resulting from other nominally two-dimensional obstacles from the literature.