• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2388-2392
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• 2013

Wind generation systems are very different in nature from conventional generation systems. Therefore it is necessary to research dynamic characteristics of wind generation systems connected to a power system. The stability analysis of wind turbine generator is an important issue in the operation of the power system. The result of angular stability of the power system that consists of only synchronous generators is different from that of the power system including wind turbine generators. This is due to the fact that generators connected to wind turbines are generally induction generators. The angular stability assessing synchronization of generators is determined by its corresponding critical clearing time(CCT). Wind turbine models for the analysis of power system are varied and difficult to use, but now these are standardized into four types. In this paper, the analysis of the CCT of the power system connected to wind farm considering the location and capacity is performed by using DFIG(Doubly-Fed induction Generator) wind turbine built-in type3 model in PSS/E-32.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.254-259
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• 2014

In this paper, we describe construction of a wind stabilization demo-site and effects of output power control of wind turbines for suppression of ramp rate using ESS (Energy Storage System). It is difficult to control the output power of distributed generator such as wind turbine which of variation is very large. If the large capacity wind farm be interconnected into power system may cause blackout due to Power Quality. For these reasons, the international standards such as Grid-Code is limited to less than 10 [%/min] of renewable energy ramp rate. The case of Korea, government actively conducts propagating large-scale renewable energy for green growth policy, to interconnecting more renewable energy into power system is necessary for stabilization technology. For these reasons, the POSCO consortium has constructed a wind stabilization demo-site that is configured as 500 [kWh] battery energy storage systems can output up to 3 [C-Rate] and two wind turbines rated 750 [kW]. In POSCO consortium, which implements various methods stabilizing output power of wind turbine such as smoothing, section firming and ramp control, we derive the results of long-term demonstration that can be controlled to satisfy to the international standard about ramp rate [%/kW] of wind turbine output power.

• Journal of the Korean Solar Energy Society
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• v.36 no.1
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• pp.27-37
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• 2016

A simple but practical Ensemble Prediction System(EPS) for wind power forecasting was developed and evaluated using the measurement of the offshore meteorological tower, HeMOSU-1(Herald of Meteorological and Oceanographic Special Unite-1) installed at the Southwest Offshore in South Korea. The EPS developed by the Korea Institute of Energy Research is based on a simple ensemble mean of two Numerical Weather Prediction(NWP) models, WRF-NMM and WRF-ARW. In addition, the Kalman Filter is applied for real-time quality improvement of wind ensembles. All forecasts with EPS were analyzed in comparison with the HeMOSU-1 measurements at 97 m above sea level during Typhoon Bolaven episode in August 2012. The results indicate that EPS was in the best agreement with the in-situ measurement regarding (peak) wind speed and cut-out speed incidence. The RMSE of wind speed was 1.44 m/s while the incidence time lag of cut-out wind speed was 0 hour, which means that the EPS properly predicted a development and its movement. The duration of cut-out wind speed period by the EPS was also acceptable. This study is anticipated to provide a useful quantitative guide and information for a large-scale offshore wind farm operation in the decision making of wind turbine control especially during a typhoon episode.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.45-52
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• 2012

Along with global warming, ever intensifying weather events have increased damages to agricultural farms and facilities. The objective of this study was to investigate the spatial distribution and regional characteristics of agricultural damages by extreme weather events. Agricultural disaster statistics provided by the National Emergency Management Agency were summed over for a 13-year period from 1998 to 2010 and used for the spatial analysis. Two indices of damage area ration and property damage per unit area were introduced to quantify regional agricultural damages. As the results, farm inundation accounted for the largest area primarily damaged by typhoons with heavy rainfalls. Most property damages to farm lands originated from farm erosion in the alpine regions by localized guerrilla rains. The two major causes of damages to greenhouse and livestock facilities were typhoon with strong wind and winter blizzards. Gangwon was the province of the largest property loss mostly from farm land erosion losses, followed by Gyeongnam, Jeonnam, and Chungnam where losses to greenhouse and livestock facilities were relatively greater. Property loss per unit area was also the greatest for the Gangwon province (4.91 M\/ha), followed by Gyongnam and Chungnam of 2.20 and 1.50 M\/ha, respectively. Unit loss for greenhouse and livestock facilities was 13.3 M\/ha, approximately 13 times greater than that for farm land (1.06 M\/ha). The study findings indicated the importance of reducing highland farm erosion and reinforcing farming facilities structures for agricultural disaster management.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.4
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• pp.75-83
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• 2017

Many parts of problems in livestock industry today are associated with organic dust. Endotoxin and toxic gasses on the surface of dust and dust itself can cause aesthetic displeasure and respiratory disease. It also reduces livestock productivity by suppressing immunity of animals and carrying microbes causing animal disease. However, dust level of cattle farm was rarely reported in Korea, and regulation for cattle farm worker does not exist. In this paper, dust concentration and environmental condition were regularly monitored in a commercial Korean native cattle farm. The measurement was conducted according to location and working activities. From the measurement, distribution of dust concentration was affected by wind environment, as the result of natural ventilation. TMR mixer was a major source of dust in target cattle house. The maximum inhalable dust concentration was 637.8 times higher than exposure limit as feed dropped into the TMR mixer. It was expected that dust generation could be affected by particle size and drop height of feed. This study suggests potential risk of dust in cattle farm, and necessity for latter study. Effect of aerodynamic condition and TMR processing should be investigated for dust reduction study.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.947-952
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• 2015

To supplement energy needs and take advantage of renewable energy sources, many wind farms are currently being built in mountainous areas under the supervision of the Korean government. However, operation of these wind farms can cause serious threats to national security due to Doppler modulation from the wind turbines causing interference with military radar operating in the vicinity. Therefore it is necessary to develop methods to analyze the Doppler frequency during the operation of wind turbines and the effect on radar signals. Based on modeling of the mountainous region, blockage analysis, turbine motion and the radar signals, this paper proposes a signal processing method to extract and analyze the Doppler frequency. Simulation results showed the change of Doppler frequency over time caused by the geometry of the mountainous area and the wind turbine.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.238-248
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• 2016

In this study, an automatic command mode transition strategy of direct power control (DPC) is proposed for permanent magnet synchronous generators (PMSGs) medium-voltage (MV) offshore wind turbines (WTs). Benchmarking against the control methods are performed based on a three-level neutral-point-clamped (NPC) back-to-back type voltage source converter (VSC). The ramping rate criterion of complex power is utilized to select the switching vector in DPC for a three-level NPC converter. With a grid command and an MPPT mode transition strategy, the proposed control method automatically controls the generated output power to satisfy a grid requirement from the hierarchical wind farm controller. The automatic command mode transition strategy of DPC is confirmed through PLECS simulations based on Matlab. The simulation result of the automatic mode transition strategy shows that the proposed control method of VOC and DPC achieves a much shorter transient time of generated output power than the conventional control methods of MPPT and VOC under a step response. The proposed control method helps provide a good dynamic performance for PMSGs MV offshore WTs, thereby generating high quality output power.

• Journal of Power System Engineering
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• v.16 no.5
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• pp.63-69
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• 2012

This paper presents an analysis on the induction heating of ring flange for wind farm. Ring flange is used for the connection of poles when building a column of wind power plant. Heat treatment of ring flange with the diameter of ${\O}1,000mm$ has been considered. For analysis on the induction heating, FEA is used. Firstly, electromagnetic filed analysis was performed to get the induction current distribution on the steel, After that, heat transfer analysis was performed using the magnetic filed analysis results. for more precise analysis, some measurement for permeability has been performed and the measurement data was used during the analysis. From the analysis, we get the temperature distribution on the ring flange.

• Structural Engineering and Mechanics
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• v.36 no.5
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• pp.599-624
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• 2010

Offshore wind turbines are relatively complex structural and mechanical systems located in a highly demanding environment. In the present paper the fundamental aspects and the major issues related to the design of these special structures are outlined. Particularly, a systemic approach is proposed for a global design of such structures, in order to handle coherently their different parts: the decomposition of these structural systems, the required performance and the acting loads are all considered under this philosophy. According to this strategy, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessments in various sub-problems, which can be solved by means of sub-models at different levels of detail, for both structural behavior and loads simulation. Specifically, numerical models are developed to assess the safety performances under aerodynamic and hydrodynamic actions. In order to face the problems of the actual design of a wind farm in the Mediterranean Sea, in this paper, three schemes of turbines support structures have been considered and compared: the mono pile, the tripod and the jacket support structure typologies.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.5
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• pp.597-607
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• 2014

This paper proposes active power control and frequency support control schemes of wind turbine generation system by using modified Maximum Power Point Tracking(MPPT) of Permanent Magnet Synchronous Generator(PMSG). Most wind turbine generation system is completely decoupled from the power system and power output control with pitch control. According to the frequency deviation, however, MPPT control can not contribute to the frequency change of the power system due to its active power output control. For solving this, the de-loaded(DL) control scheme is constructed for the frequency support control, which is based on applying the active power output control in the rotor speed control of PMSG. The rotor speed by used in the proposed DL control scheme is increased more than the optimal rotor speed of MPPT, and then this speed improvement increases the saved kinetic energy(KE). In order to show the effectiveness of the proposed control scheme, the case studies have been performed using the PSCAD/EMTDC. The results show that the proposed active power output control scheme(DL control and KE discharge control) works properly and the frequency response ability of the power system can be also improved with the frequency support of wind farm.