• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.161-164
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• 2022

부유식 라이다는 해상풍력단지 조성시 필수적으로 수행하고 있는 풍황관측 업무에 새로운 패러다임을 제공하고 있는 시스템으로, 전통적으로 풍황관측을 수행하고 있던 해상기상관측탑을 대체하여 사업 초기의 대규모 공사를 획기적으로 축소하여 시간과 비용을 절약하고, 환경적 영향을 최소화 하며, 지역사회의 반발 요소까지 줄일 수 있어 해당 업계의 표준으로 자리잡고 있는 중이다. 다만 부표식의 동요에 따른 외란적 요소가 관측자료의 신뢰성에 영향을 미치는 만큼 안정적인 플랫폼의 설계 및 검증이 매우 중요한 상황이며, 국내에서는 해당기술에 대한 늦은 진입으로 인해 다수의 외산장비 제조사들이 국내시장까지 선점하고 있는 상황이다. 한국의 서해안은 천해 환경으로 조석차가 매우 커 지역에 따라 강한 조류가 반복적으로 나타나며, 계절별로 상이한 강한 에너지의 파랑이 형성되는 등 플랫폼에 안정도에 많은 영향을 미치는 바다 환경을 갖고 있다. 본 논문에서는 이러한 복잡한 환경적 특성을 갖고 있는 우리나라의 해역에 라이다 운영에 적합한 부표식에 대한 연구를 수행하며, 우선적으로 적용하였던 선박형 부표식의 최적화 설계 및 검증 사례를 소개하고, 향후 다양한 플랫폼 개발에 토대가 되는 중요 개념을 도출하고자 한다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.4
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• pp.266-273
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• 2015

In this paper, annual wind data in 2014 at six locations(Seosudo, Gadaeam, Sibidongpa, Galmaeyeo, Haesuseo, Jigwido) are collected and analyzed in order to review optimal candidate site for offshore wind farm in the Western Seas of Korea. Observed wind data is fitted to Rayleigh and Weibull distribution and annual energy production is estimated according to wind frequency. GWE-3kH(3 kW-class) and GWE-10KU (10 kW-class) turbine are selected as wind turbine. Also, power curve are used to calculate wind energy potential. As a result, annual mean wind speed at six locations(Seosudo, Gadaeam, Sibidongpa, Galmaeyeo, Haesuseo, Jigwido) were calculated about 4.60, 4.5, 5.00, 5.13, 5.51, 5.90 m/s, respectively. In addition, annual energy production were estimated at 10,622.752, 11,313.05, 13,509.41, 14,899.55, 17,106.13, 19,660.85 kWh. Generally, annual mean energy density were between poor and marginal class and capacity factor at Jigwido was calculated at 22.44%. Its value is higher than the others.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.21-31
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• 2014

Recently, the research on renewable energy against depletion of fossil fuel have been actively carried out in the world. Especially, offshore wind turbines are very economical and innovative technology. However, offshore wind turbines experience large base moments due to the wind and wave loading, so the monopile with large diameter needs to be applied. For the economical design of the large diameter pile, it is important to consider the flexibility of the foundation to estimate the maximum moment accurately, based on studies conducted so far. In this paper, the foundation was modeled using the finite element method in order to better describe the large diameter effect of a monopile and the results were compared with those of p-y method. For the examples studied in this paper, the change in maximum moment was insignificant, but the maximum tilt angle from the finite element method was over 14% larger than that of p-y method. Therefore, the finite element approach is recommended to model the flexibility effect of the pile when large tilt angles may cause serviceability issues.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.846-855
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• 2021

Eco-friendly and renewable energy sources are actively being researched in recent times, and of shore wind power generation requires advanced design technologies in terms of increasing the capacities of wind turbines and enlarging wind turbine installation vessels (WTIVs). The WTIV ensures that the hull is situated at a height that is not affected by waves. The most important part of the WTIV is the leg structure, which must respond dynamically according to the wave, current, and wind loads. In particular, the wave load is composed of irregular waves, and it is important to know the exact dynamic response. The dynamic response analysis uses a single degree of freedom (SDOF) method, which is a simplified approach, but it is limited owing to the consideration of random waves. Therefore, in industrial practice, the time-domain analysis of random waves is based on the multi degree of freedom (MDOF) method. Although the MDOF method provides high-precision results, its data convergence is sensitive and difficult to apply owing to design complexity. Therefore, a dynamic amplification factor (DAF) estimation formula is developed in this study to express the dynamic response characteristics of random waves through time-domain analysis based on different variables. It is confirmed that the calculation time can be shortened and accuracy enhanced compared to existing MDOF methods. The developed formula will be used in the initial design of WTIVs and similar structures.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.72-77
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• 2011

The purpose for installation of offshore weather station is a measurement of wind resources and so on. If weather station is operated, it will be possible to analysis for wind resource and arrangement of wind farm by using measured data. In this paper, we carried out the development of offshore wind resource measurement system for measuring offshore wind resource. Also, In order to monitor for real-time wind data with 1 Hz, we installed the wireless transmission system. All wind characteristic data are sent to the server PC through the this system is connected outport of DataLogger. Transmitted wind data were used in order to look at in the Web-page and tablet PC on a real time basis in a graph. In this paper, we will introduce about the wind resource measurement and remote monitoring system that is the result of study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.1-8
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• 2015

Wind power systems have gained much attention due to the relatively high reliability, good infrastructures and cost competitiveness to the fossil fuels. Advances have been made to increase the power efficiency of wind turbines while less attention has been focused on structural integrity assessment of structural sub-systems such as towers and foundations. Among many parameters for integrity assessment, the most perceptive parameter may be the induced horizontal displacement at the hub height although it is very difficult to measure particularly in large-scale and high-rise wind turbine structures. This study proposes an indirect displacement estimation scheme based on the combined use of inclinometers and accelerometers for more convenient and cost-effective measurements. To this end, (1) the formulation for data fusion of inclination and acceleration responses was presented and (2) the proposed method was numerically validated on an NREL 5 MW wind turbine model. The numerical analysis was carried out to investigate the performance of the propose method according to the number of sensors, the resolution and the available sampling rate of the inclinometers to be used.

• Journal of Wind Energy
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• v.14 no.2
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• pp.26-33
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• 2023

In this study, the global response characteristics of floater and mooring for floating offshore wind turbine with a detachable mooring system are performed. Global motion and structural response result extracted from the coupled motion analysis of 10MW DTU floating offshore wind turbine with detachable mooring system modeled by high-order boundary element model and finite element mesh, were used to study the characteristics of tension on mooring lines subjected to three different types of ocean loads. Breaking limit of mooring line characterized by wind, current and wave load has a major effect on the distribution of mooring tension found in time domain analysis. Based on the numerical results of coupled motion analysis, governing equation for calculating the motion response of a floater under ocean loads, and excitation force and surge motion and tension respectively are presented using excursion curve. It is found that the response of floater is reliable and accurate for calculating the tension distributions along the mooring lines under complex loadings. This means that the minimun breaking limit of mooring system satisfied a design criteria at ultimate ocean environmental loading condtions.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.56.2-56.2
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• 2011

As rotor blade of a wind turbine becomes larger to satisfy the economic efficiency for offshore wind farm, the numerical analysis considering wind profile is getting emphasized. In this paper, the study for the power characteristic of a wind turbine is carried out using NREL phase VI wind turbine applied wind profile. The experimental data of NASA Ames wind tunnel for inflow velocity 7m/s is used and the numerical result is obtained by using CFD commercial solver(FLUENT).

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.423-426
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• 2007

Pohang Wind Energy Research Center (PoWER-C) is developing a 3 MW Radial Flux Permanent Magnet (RFPM) Synchronous Generator for offshore Wind Energy Converter (WEC). The rotor rpm is 15.7 and the gear ratio is set to be 92.93. The nominal generator rpm at the rated load is about 1459. To reduce the switching loss in the power electronics, the maximum frequency is limited to 100 Hz. This requirement limits the number of pole to six or eight. Permanent magnet excitation is assumed for higher energy yield and higher efficiency. In this report, the requirements and the first efforts for the physics design are described.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.161-162
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• 2015

최근 세계적으로 전력계통의 대륙 간 연계나 신재생에너지, 분산전원의 계통 연계를 위해 HVDC(High voltage Direct Current)에 대한 연구가 활발히 진행되고 있다. 대용량, 장거리 송전이 필요한 경우 HVAC에서의 전력손실과 송전거리의 한계를 극복하기 위하여 HVDC가 새로운 대안으로 떠오르고 있으며, LCC(Line commutated Converter)와 VSC(Voltage Source Converter)의 기술발전이 비약적으로 이뤄지고 있다. 특히, DC Grid화를 위해서 유럽에서는 해상풍력을 연계한 Windfarm을 DC Grid화 하는 프로젝트가 활발히 진행되고 있다. 이러한 신재생 에너지의 계통 연계를 위해서 DC Grid가 본격적으로 논의가 되고 있고 관련분야에서는 기술개발을 앞다퉈 진행하고 있는 상황이다. DC Grid 구현을 위해 VSC HVDC가 최근 주목받고 있으며, VSC로 연계된 DC Grid의 AC 계통과의 연계를 위해 가장 필요한 것이 바로 DC 차단기라고 할 수 있겠다. 본 논문에서는 DC Grid의 고장분석을 위한 기초연구로써 MMC(Modular Multilevel Converter) VSC를 기반으로 한 Point-to-Point HVDC Grid에서의 DC 고장에 대한 분석을 실시하였으며 그 특징을 분석하였다.