• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.504-510
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• 2015

Because wind generators (WGs) in a wind power plant (WPP) produce different active powers due to wake effects, the reactive power capability of each WG is different. This paper proposes a hierarchical voltage control scheme for a WPP that uses a WPP controller and WG controller. In the proposed scheme, the WPP controller determines a voltage error signal by using a PI controller and sends it to a doubly-fed induction generator (DFIG). Based on the reactive current-voltage ($I_Q-V$) characteristic of a DFIG, the DFIG injects an appropriate reactive power corresponding to the voltage error signal. To enhance the voltage recovery capability, the gains of the $I_Q-V$ characteristic of a DFIG are modified depending on its reactive current capability so that a DFIG with greater reactive current capability may inject more reactive power. The proposed scheme enables the WPP to recover the voltage at the point of common coupling (PCC) to the nominal value within a short time after a disturbance by using the adaptive $I_Q-V$ characteristics of a DFIG. The performance of the proposed scheme was investigated for a 100 MW WPP consisting of 20 units of 5 MW DFIGs for small and larger disturbances. The results show the proposed scheme successfully recovers the PCC voltage within a short time after a disturbance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.739-748
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• 2013

In this study, analytical works for the induced winds due to traveling vehicles on highway have been conducted by Computation Fluid Dynamics (CFD). The traveling condition was considered in two cases: (a) single direction and (b) bi-direction. The analysis was focused on the effects of the induced winds on the upper part of a median strip while the aerodynamic characteristics of the vehicles were directly analyzed in the previous studies. From the analysis results, it has been found that the maximum magnitude of the induced winds was 2.2 m/s when the vehicles travel with the speed of 50 km/h. Additionally, 4.0 m/s and 5.3 m/s were obtained with the speed of 90 km/h and 120 km/h, respectively. Especially, the induced winds was generated about 84% of the vehicle speed at 1.0 m above from the median strip when the vehicles travel with the speed of 120 km/h. The induced winds was maintained during the very short period while the traveling. conclusively, it is noted that the wind power generation can be possible by using the small-sized wind power generators installed on median strips throughout the analytical results in this study.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.5
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• pp.487-494
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• 2019

A Small-Sat Power System Design and Development should be depend on space environment such as solar wind with Electromagnetic field by hurdle of techniques. It is surmount solution of trend that will unitize and converge with power module in these days. The level of modularize means that applying Universal Middleware for payload power module requirements. The scope of target system is a main power provider module and operational subunit that can be implemented with the final power module distribution loads to consume for continuous process. A Universal Middleware strengthen to build power module from satellite power system should be accuracy and consuming data. A Power Service Module and dynamic system drive interactive management between power distribution and consumer module by Range Control. Consequently, suggesting evaluation, unexpecting payload system power consumer that makes fine variable resources in the development design process and efficiency.

• Journal of Aerospace System Engineering
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• v.13 no.1
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• pp.11-17
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• 2019

In this paper, the performance of a small fixed wing unmanned aerial vehicle is predicted theoretically with the minimum specifications and a low Reynolds number. Based on the results, it was compared with the results of an actual flight test and simple electric motor wind tunnel test. As a result of the validity of the analysis, a 3.5 kilograms class fixed wing small UAV can predict aerodynamic performance by general theory analysis. However, the required thrust was analyzed as a possible design error. Based on the results of this study, this paper proposed a method to minimize the design error when developing small fixed wing UAV flying in a low Reynolds number.

• KIEAE Journal
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• v.3 no.3
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• pp.19-25
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• 2003

The Address No.0 of Eco-friendly Architecture offers unique experience for those who visit the place to envisage the future architecture where nature, human and building exist in harmony. It is open to the general public including the students of elementary and secondary schools. This house has been built to provide opportunities for the general public to experience eco-friendly architecture. It's floor area is 42 pyung($140m^2$) and the overall site has the area of 180 pyung($600m^2$). The following illustrates some of its prominent features : ${\bullet}$ Remodeling of a traditional Korean residence ${\bullet}$ Application of passive solar systems ${\bullet}$ Use of clerestory windows and daylighting systems(washroom and machine room) ${\bullet}$ Operation of solar water heaters with flat plate collectors ${\bullet}$ Construction of Biotop(small ecological world) ${\bullet}$ Water circulation for Biotop by photovoltaic(150W) and wind power(400W) generation ${\bullet}$ Outdoor hot water supplied by all-glass evacuated solar tubes. Through this Address No.0 of Eco-friendly Architeture conclusions are as followings. 1. The array of tubes in collector has the best nice in that the number of tube is nine and the tilt angle is the latitude $+20^{\circ}$. 2. The thermal performance of the all-glass solar vacuum collector was excellent than of the flate-plate solar collector. 3. The adaption of new small wind power systems to buildings were proved to produce a profit if it is considered the expense of environment improvement and the wind speed increasing according to rise of building hight.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.101-112
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• 2015

Renewable energy resources play an important part in the world's future. Renewable energy sources have the following components: biomass, geothermal, solar thermal, directs solar, wind, tidal and hydropower. Hydropower is still the most efficient way to generate electricity worldwide. Hydropower projects can contribute as a cheap energy source, as well to encourage the development of small industries across a wide range of new technology; furthermore hydropower systems use the energy in flowing and falling water to produce electricity or mechanical energy. Hydropower systems are classified as large, medium, small, mini and micro according to their installed power generation capacity, as do the following components: water turbines, control mechanisms and electrical transmissions. In this article a review of small hydropower systems has been done on the principles surrounding the fundamentals of hydraulic engineering, the fundamentals of hydrology, identification of sites and economic analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.2
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• pp.335-338
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• 2012

Recently, the energy has been used much more than ever, but there has been many problems including atmospheric pollution. So we need alternative energy resources, which are solar heat, solar light, wind power, small water power, etc. The field, which is most popular these days, is the energy source by solar light which transform electric energy using the solar cell and it is available with many researches. In this paper, we manufactured the solar power generation system over 90W using solar module which was 9.90V for Voc, 0.93 A for Isc, 8.64 V for Vmp, 0.75 A for Imp, 6.5 W for power. System was controlled by step motor with worm gear to operate optimum condition between $0^{\circ}{\sim}70^{\circ}$ angle. This system was very effective in tracking space use because it need less space than general solar module.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.6
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• pp.566-572
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• 2013

In the present study, structure analysis has been performed to understand the deflection and stress distribution for a hybrid street-lamp having a vertical-axis wind turbine and a photovoltaic panel. Modal analysis is also evaluated to avoid resonance gerenerated by sychronism between a turbine and a lamppost. To analyze deflection, stress and frequency, general analysis code(ANSYS-Mechanical 13) is employed in the present work. Throughout structure analysis in the hybrid street-lamp, maximum stress is observed at the connecting position between a turbine blade and a blade supporter. Campbell diagram which is combined the natural frequency of turbine blades and blade passing frequency is presented to analyze a system resonance. It is found that the resonance of the system having a rotating turbine blade and a lamppost can avoid by the optimal selection of geometric parameters of a wind turbine.

• Journal of the Korean Society of Visualization
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• v.10 no.1
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• pp.27-33
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• 2012

This paper describes a new design of small-scale horizontal wind blade, called spiral wind turbine blade. Theoretical and numerical approaches on the prediction of aerodynamic performance of the blade have been conducted. A theoretical equation is successfully derived using the angular momentum equation to predict aerodynamic characteristics according to the design shape parameters of spiral blade. To be compared with the theoretical value, a numerical simulation using ANSYS CFX v12.1 is performed on the same design with the theoretical one. Large scale tip vortex is captured and graphically presented in this paper. The TSR-$C_p$ diagram shows a typical parabolic relation in which the maximum efficiency of the blade approximately 25% exists at TSR=2.5. The numerical simulation agrees well with that of the theoretical result except at the low rotational speed region of 0~20 rad/s.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.117-124
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• 2012

In this paper, an analysis of the joint that transmits power from the blades to the generator is performed using the FEM (finite element method). The mode shapes and natural frequencies were extracted using experimental modal analysis in order to establish the FEM model. Then, the model was verified by comparing the mode shapes and natural frequencies to those obtained from the ANSYS modal analysis. Dynamic stress analysis was performed at the rated and limited wind speeds considering the wind load and gravity.