• Journal of the Korea Society for Simulation
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• v.32 no.3
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• pp.33-41
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• 2023

As carbon-free has been getting interest, renewable energy sources have been increasing. However, renewable energy is intermittent and variable so it is difficult to predict the produced electrical energy from a renewable energy source. In this study, digital-twin concept is applied to solve difficulties in predicting electrical energy from a renewable energy source. Considering that rotation of wind turbine has high correlation with produced electrical energy, a model which simulates rotation in the drivetrain of a wind turbine is developed. The base of a drivetrain simulation model is set with well-known state equation in mechanical engineering, which simulates the rotating system. Simulation based machine learning is conducted to get unknown parameters which are not provided by manufacturer. The simulation is repeated and parameters in simulation model are corrected after each simulation by optimization algorithm. The trained simulation model is validated with 27 real wind turbine operation data set. The simulation model shows 4.41% error in average compared to real wind turbine operation data set. Finally, it is assessed that the drivetrain simulation model represents the real wind turbine drivetrain system well. It is expected that wind-energy-prediction accuracy would be improved as wind turbine digital twin including the developed drivetrain simulation model is applied.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.1
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• pp.65-76
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• 2024

With the recent activation of the offshore wind power industry, there has been a development of power plants with a scale exceeding 400MW, comparable to traditional thermal power plants. Renewable energy, characterized by intermittency depending on the energy source, is a prominent feature of modern renewable power generation facilities, which are structured based on controllable inverter technology. As the integration of renewable energy sources into the grid expands, the grid codes for power system connection are progressively becoming more defined, leading to active discussions and evaluations in this area. In this paper, we propose a method for selecting optimal reactive power compensation capacity when multiple offshore wind farms are integrated and connected through a shared interconnection facility to comply with grid codes. Based on the requirements of the grid code, we analyze the reactive power compensation and excessive stability of the 400MW wind power generation site under development in the southwest sea of Jeonbuk. This analysis involves constructing a generation site database using PSS/E (Power System Simulation for Engineering), incorporating turbine layouts and cable data. The study calculates reactive power due to charging current in internal and external network cables and determines the reactive power compensation capacity at the interconnection point. Additionally, static and dynamic stability assessments are conducted by integrating with the power system database.

• Clinical and Experimental Pediatrics
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• v.51 no.2
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• pp.181-187
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• 2008

Purpose : Asthma is characterized by reversible airway obstruction and bronchial hyperresponsiveness result from airway inflammation. Fraction of nitric oxide in expired air (FeNO) has recently been investigated as a noninvasive measure of airway inflammation. FeNO has been reported to correlate with induced sputum eosinophilia and methacholine challenge test that it is represent severity of asthma. The purpose of this study was to analyze the relationship of FeNO with pulmonary function tests in patients with intermittent asthma. Methods : Eighty children included in this study were diagnosed as asthma from April through August, 2005 in Department of Pediatrics, College of Medicine, Kyunghee University. They aged from 4 to 15 years who were able to conduct spirometry and FeNO monitoring. They did not have upper respiratory tract infection and did not use an asthma controller which contain corticosteroids within 4 weeks. Pulmonary function test was done and FeNO was measured with online tidal breathing method using a chemiluminescence NO analyzer (CLD 88 sp, Eco Medics, Duernten, Switzerland). The correlations between pulmonary function test and FeNO were analyzed using Spearman correlation coefficient method. Results : The mean of FeNO of subject was 16.88 parts per billion (ppb). The mean of forced expiratory volume in 1 second ($FEV_1$) was $0.890{\pm}0.455L$ and forced vital capacity (FVC) was $1.071{\pm}0.630L$. The mean of predicted $FEV_1%$ ($FEV_1%pred$) was $98.39{\pm}34.27%$ and $FEV_1/FVC$ was $88.53{\pm}19.49$. FeNO was significantly correlate with $FEV_1$ (r=0.345, P<0.01) and FVC (r=0.244, P<0.05). FeNO did not correlate with $FEV_1%pred$ or $FEV_1/FVC$. Conclusion : The measurement of FeNO could be a useful marker in the management of childhood asthma and it is evolving to provide a complementary role alongside existing pulmonary function test. We propose that measuring technique and establishment of normal reference range are important area for future research.

• Tuberculosis and Respiratory Diseases
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• v.51 no.1
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• pp.35-43
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• 2001

Background : The eosinophil chemotactic and activating effects of eotaxin and the known association of eosinophils with asthma suggest that eotaxin expression is increased during an asthma attack. This study was aimed to determine whether the plasma eotaxin levels are higher in patients during an asthma attack and to correlate the eotaxin levels with the disease activity, severity and response to therapy. Method : A case-control study of the plasma eotaxin levels was performed in 100 patients with exacerbated asthma and 48 age- and sex-matched subjects with stable asthma. Results : The plasma eotaxin levels were significantly higher in the 100 patients with exacerbated asthma($233{\pm}175\;pg/mL$) than in the 48 subjects with stable asthma($169{\pm}74\;pg/mL$). A trend toward higher eotaxin levels was observed in asthmatic subjects who were taking oral steroids ($332{\pm}225\;pg/mL$) than in those who were not ($214{\pm}159\;pg/mL$) and higher levels were found in those admitted to the hospital ($275{\pm}212\;pg/mL$) than in those discharged after receiving only emergency treatment ($190{\pm}115\;pg/mL$). The eotaxin levels inversely correlated with the $FEV_$ (r=-0.25, p<0.01). The eotaxin levels were higher in moderate persistent ($323{\pm}256\;pg/mL$) and severe persistent asthmatics ($276{\pm}170\;pg/mL$) than in mild intermittent asthmatics ($l60{\pm}60\;pg/mL$). Conclusion : Eotaxin expression is directly associated with asthma exacerbation, impaired pulmonary function and the disease severity.

• Tuberculosis and Respiratory Diseases
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• v.52 no.1
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• pp.24-36
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• 2002

Background: Bronchial reactivity is known to be a component of airway hyperresponsiveness, a cardinal feature of asthma, with bronchial sensitivity, and is increments in response to induced doses of bronchoconstrictors as manifested by the steepest slope of the dose-response curve. However, there is some controversy regarding methods of measuring bronchial reactivity and clinical impact of such measurements. The purpose of this study was to evaluate the clinical significance and assess the clinical use by analyzing the relationship of the bronchial sensitivity, the clinical severity and the changes in pulmonary function with bronchial reactivity. Method: A total of 116 subjects underwent a methacholine bronchial provocation test. They were divided into 3 groups : mild intermittent, mild persistent, moderate and cough asthma. Severe patients were excluded. Methacholine PC20 was determined from the log dose-response curve and PC40 was determined by one more dose inhalation after PC20. The steepest slope of log dose-response curve, connecting PC20 with PC40, was used to calculate the bronchial reactivity. Body plethysmography and a single breath for the DLCO were done in 43 subjects before and after methacholine test. Results: The average bronchial reactivity was 38.0 in the mild intermittent group, 49.8 in the mild persistent group, 61.0 in the moderate group, and 41.1 in the cough asthma group. There was a weak negative correlation between PC20 and bronchial reactivity. A heightened bronchial reactivity tends to produce an increased clinical severity in patients with a similar bronchial sensitivity and basal spirometric pulmonary function. There were significant correlations between the bronchial reactivity and the initial pulmonary function before the methacholine test in the order of sGaw, Raw, $FEV_1$/FVC, MMFR. There were no correlations between the bronchial sensitivity and the % change in the pulmonary function parameters after the methacholine test. However, there were significant correlations between the bronchial reactivity and the PEF, $FEV_1$, DLCO. Conclusion: There was weak significant negative correlation between the bronchial reactivity and the bronchial sensitivity, and the bronchial reactivity closely reflected the severity of the asthma. Accordingly, measuring both the bronchial sensitivity and the bronchial reactivity can be of assistance in assessing of the ongoing disease severity and in monitoring the effect of therapy.