• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.7
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• pp.380-388
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• 2006

In this paper, a novel control algorithm to minimize the power loss of the induction generator for wind power generation system is presented. The proposed method is based on the flux level reduction, where the flux level is computed from the machine model for the optimum d-axis current of the generator. For the vector-controlled induction generator, the d-axis current controls the excitation level in order to minimize the generator loss while the q-axis current controls the generator torque, by which the speed of the induction generator is controlled according to the variation of the wind speed in order to produce the maximum output power. Wind turbine simulator has been implemented in laboratory to validate the theoretical development. The experimental results show that the loss minimization process is more effective at low wind speed and that the percent of power loss saving can approach to 25%. Experimental results are shown to verify the validity of the proposed scheme.

• New & Renewable Energy
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• v.10 no.1
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• pp.41-49
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• 2014

For a proper valuation of wind power project, it is necessary to consider volatilities of key parameters such as annual energy production, electricity sales price, and long term interest rate. Real option methodology allows to calculate option values of these parameters. Volatilities to be considered in wind project valuation are 1) annual energy production (AEP) estimation due to meteorological variation and estimation errors in wind speed distribution, 2) changes in system marginal price (SMP), and 3) interest rate fluctuation of project financing which provides refinancing option to be exercised during a loan tenor for commercial scale projects. Real option valuation turns out to be more than half of the sales value based on a case study for a FIT scheme wind project that was sold to a financial investor.

• 한국신재생에너지학회:학술대회논문집
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• 2008.10a
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• pp.307-309
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• 2008

This study suggests a modeling of grid-connected wind turbine generation system that has induction generator, and aims to perform simulations for outputs by the variation of actual wind speed and for fault current of wind generation system by the transformer winding connection. This study is implemented by matlab&simulink. The simulation shall be performed by assuming single line to ground fault generated in the system. Generator power, generator rotor speed, generator terminal current and fault current shall be observed following the performance of simulation. The fault current change will be dealt through the simulation results for fault current of wind generation system following the grid-connected transformer winding connection and the simulation result by the transformer neutral ground method.

• Wind and Structures
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• v.1 no.2
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• pp.145-160
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• 1998

In recent years, the effects of a possible climate change have been discussed in regard to wind loading on buildings and structures. Simple scenarios based on the assumption of global warming suggest an increase of storm intensities and storm frequencies and a possible re-distribution of storm tracks. Among recent publications, some papers seem to verify these scenarios while others deny the influence of climatic change. In an introductory step, the paper tries to re-examine these statements. Based on meteorological observations of a weather station in Germany, the existence of long-term trends and their statistical significance is investigated. The analysis itself is based on a refined model for the wind climate introducing a number of new basic variables. Thus, the numerical values of the design wind loads used in modern codes become more justified from the probabilistic point of view.

• Journal of Electrical Engineering and Technology
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• v.7 no.2
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• pp.157-162
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• 2012

Wind energy is created in mega-sized wind farms situated kilometers off shore. In fact, two possibilities are considered for the transmission system between the offshore wind farm and the onshore grid: high-voltage direct current and high-voltage alternating current. From this point of view, the current paper aims to compare both systems for a 2 GW wind farm situated 80 km from the Point of Common Coupling on an economic basis using a discounted cash flow analysis. A tool is developed in Microsoft Excel to allow for quick insight in the variation of input parameters.

• Journal of Power Electronics
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• v.11 no.3
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• pp.342-349
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• 2011

We propose a torque and pitch control scheme for variable speed wind turbines with permanent magnet synchronous generator (PMSG). A torque controller is designed to maximize the power below the rated wind speed and a pitch controller is designed to regulate the output power above the rated wind speed. The controllers exploit the sliding mode control scheme considering the variation of wind speed. Since the aerodynamic torque and rotor acceleration are difficult to measure in practice, a finite time convergent observer is designed which estimates them. In order to verify the proposed control strategy, we present stability analysis as well as simulation results.

• Journal of Bio-Environment Control
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• v.1 no.1
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• pp.28-36
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• 1992

The wind pressure distributions were analyzed to provide fundamental criteria for the structural design on e single-span arched house according to the wind directions through the wind tunnel experiment. In order to investigate the wind force distributions, the variation of the wind force coefficients, the mean wind force coefficients, the drag force coefficients and the lift force coefficients were estimated by using the experimental data. The results obtained are as follows: 1. When the wind direction was normal to the wall, the maximum positive wind pressure along the height of the wall occurred approximately at two-thirds of the wall height because of the effects of boundary layer flow. 2. When the wind direction was 30$^{\circ}$ to the wall, the maximum positive wind force occurred at the windward edge of the wall. When the wind direction was parallel to the wall, the maximum negative wind force occurred at the windward edge of the wall. 3. The maximum negative wind force along the width of the roof appeared around the width ratio, 0.4, and that along the length of the roof appeared around the length ratio, 0.5. 4. According to the results of the mean wind force coefficients analysis, the maximum negative wind force occurred on the roof at the wind direction of 30$^{\circ}$. 5. The wind forces at the wind direction of 30$^{\circ}$ instead of 0$^{\circ}$ are recommended in the structural design of supports for a house. 6. To prevent partial damage of a house structure by wind forces, the local wind forces should be considered to the structural design of a house.

• Atmosphere
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• v.22 no.1
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• pp.97-107
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• 2012

To investigate variation of aerosol number concentration at each different size with three-dimensional (3D) wind components in ocean area, aerosol particles and 3D wind components were measured in the Ieodo Ocean Research Station, which is located to 419 km southwest from Marado, the southernmost island of Korea, from 25 June to 8 July 2010. The Laser Particle Counter (LPC) and ultrasonic anemometer were used to measure the size of aerosol particles and 3D wind components (zonal (u), meridional (v), and vertical (w) wind) respectively. Surface weather chart, NCEP/NCAR reanalysis data and sounding data were used to analyze the synoptic condition. The distribution of aerosol number concentration had a large variation from bigger particles more than 1.0 ${\mu}m$ in diameter by wind direction during precipitation. In the number concentration of aerosol particles with respect to the weather conditions, particles larger than 1.0 ${\mu}m$ in size were decreased and sustained to the similar concentration at smaller particles during precipitation. The increase in aerosol number concentration was due to the sea-salt particles which was suspended by southwesterly and upward winds. In addition, the aerosol number concentration with vertical wind flow could be related with the occurrence and increasing mechanism of aerosol in marine boundary layer.

• Wind and Structures
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• v.31 no.1
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• pp.59-73
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• 2020

Wind fragility analysis (WFA) of concrete chimney is often executed disregarding temperature effects. But combined wind and temperature effect is the most critical limit state to define the safety of a chimney. Hence, in this study, WFA of a 70 m tall RC chimney for combined wind and temperature effects is explored. The wind force time-history is generated by spectral representation method. The safety of chimney is assessed considering limit states of stress failure in concrete and steel. A moving-least-squares method based dual response surface method (DRSM) procedure is proposed in WFA to alleviate huge computational time requirement by the conventional direct Monte Carlo simulation (MCS) approach. The DRSM captures the record-to-record variation of wind force time-histories and uncertainty in system parameters. The proposed DRSM approach yields fragility curves which are in close conformity with the most accurate direct MCS approach within substantially less computational time. In this regard, the error by the single-level RSM and least-squares method based DRSM can be easily noted. The WFA results indicate that over temperature difference of 150℃, the temperature stress is so pronounced that the probability of failure is very high even at 30 m/s wind speed. However, below 100℃, wind governs the design.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.1-10
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• 2012

This paper proposes a modeling and controller design approach for a wind-diesel hybrid system including dump load. Wind turbine depends on nature such as wind speed. It causes power fluctuations of wind turbine. Excessive power fluctuation at stand-alone power grid is even worse than large-scale power grid. The proposed control scheme for power quality is fuzzy PI controller. This controller has advantages of PI and fuzzy controller. The proposed model is carried out by using Matlab/Simulink simulation program. In the simulation study, the proposed controller is compared with a conventional PI controller. Simulation results show that the proposed controller is more effective against disturbances caused by wind speed and load variation than the PI controller, and thus it contributes to a better quality wind-diesel hybrid power system.