• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.221-224
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• 2005

This paper discribes the nonlinear distortion of a pHEMT power amplifier. In the paper, we have used some commercially available power amplifiers for analyzing the relationship between the $IMD_3$ and ACPR for wireless LAN. And the $IMD_3$ results using two-tone test have been compared with ACPR to satisfy the requited 802.11g standard ACPR value. Measurement result shows that $IMD_3$ of 20MHz tone-spacing need to be more than 18.45dBc for power amplifiers. The WCDMA signal is fed into the power amplifier, for analyzing relationship between the asymmetrical $IMD_3$ and ACLR. With measurement result, the asymmetrical $IMD_3$ characteristic has increased with the increase of two-tone spacing. $IMD_3$ measurement result with maximum 20MHz of the two-tone spacing, shows that the difference between $IMD_3(lower)$ and $IMD_3(upper)$ is about 7dB. And the measured ACLR shows 5dB difference at -4MHz and +4MHz offset from center frequency.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.423-424
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• 2016

Recently, the mass production of Energy storage system (ESS) is actively perform around world. Energy storage system is a technique that stores power to energy storage device to supply energy into grid and load at peak-load. Therefore, the efficient energy management is available by using ESS system. The life of Lithium-ion battery is varied corresponding to the power usage, especially selected depth of discharge (DOD). The lifetime of battery is the one of the most issue of the ESS system because of its stability and reliability. Therefore, lifetime management of battery and power converter of ESS module is required. In this paper, the battery lifetime management method estimating residual power and lifetime of lithium ion battery of ESS system is proposed. Also, total avenue prediction of ESS system is simulated considering the total lifetime of battery.

• The KSFM Journal of Fluid Machinery
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• v.9 no.2 s.35
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• pp.7-12
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• 2006

This study is to develop a system of electric power generation utilizing the wind resources available in the domestic wind environment. We tested drag-type vortical wind turbine models, which have two different types of blades: a flat plate and circular arc shape. Through a performance test, conditions of maximum rotational speed were found by measuring the rpm of wind turbine. The rotational speed was measured by a tachometer in a wind tunnel and the tunnel wind speed was by using a pilot-static tube and a micro manometer. The performance test for a prototype was accomplished by calculating power, power coefficient, torque coefficient from the measurement of torque and rpm by a dynamometer controller From the measurements for miniature turbine models with two different blades, the circular arc shape was found to Produce a maximum rotational speed for the same wind velocity condition. Based on this result, the prototype with the circular arc blade was made and tested. We found that it produces 500W at the wind velocity of 10.8 m/s and the power coefficient was 20%.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1400-1401
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• 2011

RPS(Renewable Portfolio Standard) recently with the introduction of a new solar power development as the market expands, land shortage of solar power as an alternative site for installing solar water development has emerged. Solar water dams, reservoirs and water by taking advantage of available solar power development a new concept of private forest land in a way does not involve destruction of the forest land and water resources through efficient use of environmentally friendly energy production and water quality improvement There are a variety of benefits. This paper won the nation's first solar power to enforce the selection of the optimal location for solar power's award for planning theory and research techniques are intended to establish. Award of the solar system through the analysis of a few research-related materials and renewable energy systems project implementation process to establish an initial investigation techniques as well as the existing dam located about fitness will be assessed. In this study, solar water conducting business in the current analysis with considerable planning and installation of solar installation for the economic and environmental cost of the evaluation period and is expected to be able to give you one.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.10
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• pp.126-133
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• 2007

This paper proposes information technology based data mining to forecast short term power demand. A time-series analyses have been applied to power demand forecasting, but this method needs not only heavy computational calculation but also large amount of coefficient data. Therefore, it is hard to analyze data in fast way. To overcome time consuming process, the author take advantage of universally easily available information technology based data-mining technique to analyze patterns of days and special days(holidays, etc.). This technique consists of two steps, one is constructing decision tree, the other is estimating and forecasting power flow using decision tree analysis. To validate the efficiency, the author compares the estimated demand with real demand from the Korea Power Exchange.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.9
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• pp.89-98
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• 2014

A diagnostic fluoroscopy X-ray system uses a 32kW or greater X-ray generator for obtaining real-time moving images and high-resolution images. Fluoroscopy X-ray systems have to use a high-capacity AC power source to perform long-time low-power fluoroscopy and short-time high-power spot exposure. In this paper, we propose a hybrid type X-ray generator for fluoroscopy X-ray system which can perform fluoroscopy and spot exposure with a low-capacity AC power source and an energy storage device. The characteristics of energy storage devices are compared and each energy storage device is modelled to equivalent circuit. And the characteristics of available energy are analyzed as a function of output voltage and power. A 32kW class hybrid X-ray generator with EDLC as an energy storage device for fluoroscopy X-ray system was constructed, and its validity was verified by means of simulations and experiments.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.2
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• pp.143-151
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• 2015

Recently, tidal current energy conversion is a promising way to harness the power of tides in order to meet the growing demands of energy utilization. A new concept of tidal current energy conversion device, named Vane Tidal Turbine (VTT), is introduced in this study. VTT has several special features that are potentially more advantageous than the conventional tidal turbines, such as propeller type tidal turbines. The purpose of this study on VTT is to analyze the possibility of extracting the hydrokinetic energy of tidal current and converting it into electricity, and evaluate the performance of turbines for various numbers of blades (six, eight and twelve) using Computational Fluid Dynamics (CFD). At various tip-speed ratios (TSR), the six-bladed turbine obtains the highest power and torque coefficients, power efficiency is up to 28% at TSR = 1.89. Otherwise, the twelve blade design captures the smallest portion of available tidal current energy at all TSRs. However, by adding more blades, torque extracted from the rotor shaft of twelve-bladed turbine is more uniform due to the less interrupted generation of force for a period of time (one revolution).

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1125-1131
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• 2013

Wireless power transmission technology has been studied variety. Recently, wireless power transmission technology used by resonance and magnetic induction field is applied to various fields. However, magnetic resonance and inductive coupling are have drawbacks - power transmission distance is short. Microwave transmission and accept techniques have been developed to overcome short distance. However, improvement in efficiency is required. This paper, propose a high-efficiency microwave energy acceptor IC(EAIC). Suggested EAIC is consists of RF-DC converter and DC-DC converter. Wide Input power range is -15 dBm ~ 20 dBm. And output voltage is boosted up to 5.5 V by voltage boost-up circuit. EAIC can keep the output voltage constant. Available efficiency of RF-DC converter is 95.5 % at 4 dBm input. And DC-DC efficiency is 94.79 % at 1.1 mA load current. Fully EAIC efficiency is 90.5 %.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.7
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• pp.2530-2547
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• 2015

In the recent years, femtocell technology has received a considerable attention due to the ability to provide an efficient indoor wireless coverage as well as enhanced capacity. However, under the spectrum sharing between femtocell user equipment (FUEs) and the owner of spectrum macrocell user equipment (MUEs), both may experience higher uplink interference to each other. This paper proposes a novel distributed power control algorithm for the interference management in two-tier femtocell networks. Due to the assignment of licensed radio frequency to the outdoor macrocell users, the access priority of MUEs should be higher than FUEs. In addition, the quality of service (QoS) of MUEs that is expressed in the target signal-to-interference-plus-noise ratio (SINR) must always be achieved. On the other hand, we consider an efficient QoS provisioning cost function for the low-tier FUEs. The proposed algorithm requires only local information and converges even in cases where the frontiers of available power serve the target SINRs impossible. The advantage of the algorithm is the ability to implement in a distributed manner. Simulation results show that the proposed algorithm based on our cost function provides effective resource allocation and substantial power saving as compared to the traditional algorithms.

• Wind and Structures
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• v.23 no.6
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• pp.577-594
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• 2016

In this paper a practical modelling methodology is presented for a series of aero- servo- elastic- coupled numerical analyses of small wind turbine operation, with particular emphasis on variable speed generator modelling in various wind speed conditions. The following characteristics are determined using the available computer tools: the tip speed ratio as a function of the generator constant (under the assumption of constant wind speed), the turbine coefficient of power as a function of the tip speed ratio (the torque curve is modified accordingly and generator speed and power curves are plotted), turbine power curves and coefficient of power curve as functions of the incoming wind speed. The last stage is to determine forces and torques acting on rotor blades and turbine tower for specific incoming wind speeds in order to examine the impact of the stall phenomena on these values (beyond the rated power of the turbine). It is shown that the obtained results demonstrate a valuable guideline for small wind turbines design process.