• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.184.1-184.1
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• 2010

Floating wind turbines have been suggested as a feasible solution for going further offshore into deeper waters. However, floating platforms cause additional unsteady motions induced by wind and wave conditions, so that it is difficult to predict annual energy output of wind turbines by using conventional power prediction method. That is because sectional inflow condition on a rotor plane is varied by unsteady motion of floating platforms. Therefore, aerodynamic simulation using Vortex Lattice Method(VLM) were used to investigate the influence of motion on the aerodynamic performance of a floating offshore wind turbine. Simulation with individual motion of offshore platform were compared to the case of onshore platform and carried out according to the wave height and the wave angular frequency.

• Tribology and Lubricants
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• v.27 no.4
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• pp.204-208
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• 2011

Yaw brakes are used in wind turbines to control the orientation of blades to be perpendicular to the wind. These devices are very important machine elements because they are closely related to the overall efficiency of wind turbines. One unit of yaw brakes is composed of a friction pad and a caliper. In this study, a tangential force between the friction pad and the disk is calculated when the brake is acting in 750 kW wind turbine. Then, stress distribution and the deformation of the caliper are calculated using a finite element analysis. An experimental equipment is also developed to verify the exactness of calculated results. The analytical and experimental results are presented and discussed.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1068-1069
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• 2015

Wind turbines have an enormous potential for decentralized electricity generation. In recent years, there has been an increasing worldwide interest in small/medium wind systems. This paper presents the results of power performance testing conducted on a 50 kW turbine located in Yeonggwang test-bed. The turbine system is a pitch, active yaw, variable speed, upwind, three blade with a direct drive PMSG. This thesis covers the operation of variable speed wind turbines with pitch-yaw control. The system considered is controlled to generate maximum energy while minimizing loads. The data include power, wind speed, and direction from meteorological towers, and nacelle anemometer readings and output from turbine. The analysis concentrates on the effect of the load on the power-wind speed curve of the turbine.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.725-730
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• 2012

In this paper, flow noise characteristics of Savonius-type vertical-axis wind turbines are numerically investigated using hybrid CAA techniques. High frequency harmonics as well as BPF components are identified in the predicted noise spectra from a Savonius wind turbine. As the BPF components belong to infrasound, the higher harmonic components affects human response dominantly. Further analysis is performed to investigate the reason causing the higher frequency harmonic noise by changing operational conditions of a Savonius wind turbine. Based on this result, it is revealed that the frequency of higher harmonic components is determined by the radius of blades and angular velocity of Savonius wind turbine.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.3
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• pp.171-179
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• 2015

Usually, in case of wind turbines on land, there are a lot of constraints for installation such as the insufficient installation space and noise pollution. On March 11, 2011, a nuclear leakage accident occurred due to the tsunami caused by the earthquake in Japan and then there have been a rapidly growing interest in floating offshore wind turbines. In this study, an optimization of the substructure of a semi-submersible type floating offshore wind turbine was made. Design variables were set and design alternatives were fixed. UOU-FAST was used for motion analysis in combined environmental conditions of waves and wind. Response Amplitude Operators(RAOs) were compared between the design alternatives.

• Smart Structures and Systems
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• v.22 no.2
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• pp.139-150
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• 2018

A variable electromotive-force generator (VEG), which is a modified generator with an adjustable overlap between the rotor and the stator, is proposed to expand the operational range of a regular generator through a simple and robust active control strategy. It has a broad range of applications in hybrid vehicles, wind turbines, water turbines, and similar technologies. A mathematical model of the VEG is developed, and a novel prototype is designed and fabricated. The performance of the VEG with an active control system, which adjusts the overlap ratio based on the desired output power at different rotor speeds for a specific application, is theoretically and experimentally studied. The results show that reducing the overlap between the rotor and the stator of the generator results in reduced torque loss of the generator and an increased rotational speed of the generator rotor. A VEG can improve the fuel efficiency of hybrid vehicles; it can also expand operational ranges of wind turbines and water turbines and harness more power.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.186-192
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• 2014

Recently wind energy penetration into power systems has increased. Wind power, as a renewable energy source, plays a different role in the power system compared to conventional power generation units. As long as only single and small wind power units are installed in the power system, wind power does not influence power system operation and can easily be integrated. However, when wind power penetration reaches a significantly high level and conventional power production units are substituted, the impact of wind power on the power system becomes noticeable and must be handled. The connection of large wind turbines and wind farms to the grid has a large impact on grid stability. The electrical power system becomes more vulnerable to and dependent on wind energy production, and therefore there is an increased concern about the large wind turbines impact on grid stability. In this work, a new type of fuzzy logic controller for the frequency control of wind farms is proposed and its performance is verified using SimWindFarm toolbox which was developed as part of the Aeolus FP7 project.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1172-1173
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• 2008

At the moment, the control ability of wind farms is a prime research concern for the grid integration of large wind farms, due to their required active role in the power system. As more wind turbines are installed, the power from wind energy will start to replace conventional generation units and its influence on power systems cannot be neglected. Besides, because of the intermittent nature of wind the output power of wind turbines fluctuates according to wind speed variation. Especially an isolated power system with small capacity such like Jeju needs more systematic solutions and regulations(grid code). This paper presents the idea of approach for centralized operating wind farm strategy to regulate the wind farm power production to the reference power ordered by the system operator. The doubly fed induction generator(DFIG) can control active and reactive power in feasible range. So wind farm comprised of DFIG has the possibility of a controllable component in the power system. The presented wind farm control has a hierarchical structure with both a wind farm control level and a wind turbine control level.

• Journal of the Korean Solar Energy Society
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• v.31 no.5
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• pp.60-66
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• 2011

Selecting optimal wind turbine generators for wind farm sites in the capacity factor point of view is performed in this study. A program to determine the best wind turbine generator for the maximum capacity factor for a site was developed. The program uses both the wind characteristics of the site of interest and the power curves of the wind turbines. The program developed was applied to find out optimal wind turbine generators of three different sites in complex terrain and successfully yielded the best site dependent wind turbine generators. It was also used to determine the best wind turbine generator of the wind farm currently operating in Korea and proved its usefulness. The program and methodology developed in this study considered to be very useful at the initial design stage of the wind farm to determine the best wind turbine generators for the site of interest.

• New & Renewable Energy
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• v.16 no.2
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• pp.14-19
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• 2020

Recently, a project to build a carbon zero island with no carbon emissions has been carried out by replacing diesel generators with renewable energy sources in island areas where diesel generators supplied local loads as independent systems. To minimize damage to the lives of islanders, low noise wind generators should be installed by adjusting the rated speed. In islands with low loads, wind turbines that are more efficient than medium-sized wind turbines should be installed. In this study, the generator field analysis and characteristics were analyzed to develop 230 kW-class low wind medium-wind turbine technology. The electromagnetic field analysis program used Maxwell. As a result, the cogging torque was reduced, and the initial maneuver wind speed and loss value were lowered. Hence, the output amount was increased with high efficiency.