• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.598-599
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• 2007

The electricity supply industry for which high stability and quality of power are the primary aim of power company and the first order of business target. As the facilities of generations, transmissions and substations are increased every year, power system becomes more complex and hard to control. The complexity of the power system causes harmful influence on its security and power facilities. Moreover, difficulty of predicting weather condition in these days with its complexity increases the level of uncertainty of energy demand. Wide area online monitoring of power system offers lots of informations and solutions which clear the causes of insecurity in power system. In this paper, we presents the development of synchrophasor data measurement and transmission system using satellite network for power system online monitoring.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.171-172
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• 2015

PMU (Phasor Measurement Unit)는 전력시스템의 노드에서 실시간으로 시간 동기화된 페이저 정보를 측정하여 전력계통 모니터링을 가능하게 하는 장치이다. 이 때, PMU가 모니터링 장치로서 활용되기 위해서는 고신뢰도의 페이저 정보 측정이 요구된다. 기본적인 페이저 추정기법은 푸리에 변환을 이용하여 정현파 신호의 기본주파수 성분을 분석하는 것으로 본 논문에서는 푸리에 변환 기반 페이저 추정기법과 웨이브렛 기반 페이저 추정기법의 성능을 분석하여 웨이브렛 기반 페이저 추정기법의 타당성을 검토하고자 하였다. 페이저 추정기법의 평가에는 IEEE 표준에 따른 TVE (Total Vector Error) 개념을 사용하며 정현파 신호의 진폭변화와 위상변화 및 잡음발생 환경의 진폭변화에 대하여 페이저 추정 기법들의 성능평가로 신뢰성을 확인하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.6
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• pp.584-591
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• 2000

Power Quality Compensator(PQC) has been installed to protect the sensitive loads against the voltage disturbances, such as voltage sag and interruption. In general, static switch is used for the purpose of link between utility and PQC. So transfer operation of the static switch play a important part in the PQC. Many studies on the structure and control of PQC have been progressed in active, but these researches have been rarely mentioned about any voltage-disturbances-detection method to start the PQC operation. In this paper, a new voltage-disturbances-detection algorithm for computer application loads using the CBEMA/ITIC curve is proposed for transfer operation of the static switch. The proposed detection algorithm is implemented to get fast detecting time through the comparison of instantaneous 3-phase voltage values transferred to DC values in the synchronous reference frame with the operating reference values. To get the robust characteristics against the noise, a first order digital filter is designed. The magnitude falling and phase delay caused by the filter are compensated through the error normalizing and numerical analysis using transfer function, respectively. Finally, the validity of the proposed algorithm is proved by ACSL simulation and experimental results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.104-111
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• 2018

The sensorless control of high efficiency air compressors using a permanent magnet type synchronous motor as an oil-free air compressor is quite common. However, due to the nature of the air compressor, it is difficult to install a position sensor. In order to control the permanent magnet type synchronous motor at variable speed, the inclusion of a position sensor to grasp the position of the rotor is essential. Therefore, in order to achieve sensorless control, it is essential to use a permanent magnet type synchronous motor in the compressor. The position estimation method based on the back electromotive force, which is widely used as the sensorless control method, has a limitation in that position errors occur due either to the phase delay caused by the use of a stationary coordinate system or to the estimated back electromotive force in the transient state caused by the use of a synchronous coordinate system. Therefore, in this paper, we propose a method of estimating the position and velocity using a rotation angle tracking observer and reducing the speed ripple through a disturbance observer. An experimental apparatus was constructed using Freescale's MPU and the feasibility of the proposed algorithm was examined. It was confirmed that even if a position error occurs at a certain point in time, the position correction value converges to the actual vector position when the position error value is found.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.49-57
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• 2009

The camera electronics in the KOMPSAT-3 payload provides the several control clocks in order to move the charges, which are converted from the light in the pixel, in the vertical and horizontal direction. Generally, the control clocks depend on the CCD internal design in the system. The KOMPSAT-3 payload uses the CCD controlled by 3-phase vertical clocks and 4-phase timing. The camera generates the various clocks such as the vertical clocks, the horizontal clocks, the summing clocks, the reset clocks and so on. The vertical clocks are deeply related to the camera performance and synchronized with satellite scan-rate even though they are relatively slow. Also, it gives the horizontal clocks without distortion under the very fast pixel-rate. This paper shows the design and simulation of the CCD clocks driver for the KOMPSAT-3 payload.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.371-379
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• 2016

In the ship design process, ship motion and propulsion performance in sea waves became very important issues. Especially, prediction of ship propulsion performance during real operation is an important challenge to ship owners for economic operation in terms of fuel consumption and route-time evaluation. Therefore, it should be considered in the early design stages of the ship. It is thought that the averaged value and fluctuation of effective inflow velocity to the propeller have a great effect on the propulsion performance in waves. However, even for the nominal velocity distribution, very few results have been presented due to some technical difficulties in experiments. In this study, flow measurements near the propeller plane using a stereo PIV system were performed. Phase-averaged flow fields on the propeller plane of a KVLCC2 model ship in waves were measured in the towing tank by using the stereo PIV system and a phase synchronizer with heave motion. The experiment was carried out at fully loaded condition with making surge, heave and pitch motions free at a forward speed corresponding to Fr=0.142 (Re=2.55×106) in various head waves and calm water condition. The phase averaged nominal velocity fields obtained from the measurements are discussed with respect to effects of wave orbital velocity and ship motion. The low velocity region is affected by pressure gradient and ship motion.

• Journal of the Korea Society of Computer and Information
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• v.14 no.2
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• pp.157-168
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• 2009

In this paper, a photovoltaic system is designed with a step up chopper and single phase PWM(Pulse Width Modulation) voltage source inverter. Where proposed Synchronous signal and control signal was processed by one-chip microprocessor for stable modulation. The step up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature because solar cell has typical voltage and current dropping character. The single phase PWM voltage source the inverter using inverter consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be developed continuously by connecting with the source of electric power for ordinary use. It can cause the effect of saving electric power. from 10 to 20[%]. The single phase PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. In order to enhance the efficiency of photovoltaic cells, photovoltaic positioning system using sensor and microprocessor was design so that the fixed type of photovoltaic cells and photovoltaic positioning system were compared. In result, photovoltaic positioning system can improved 5% than fixed type of photovoltaic cells. In addition, I connected extra power to the system through operating the system voltage and inverter power in a synchronized way by extracting the system voltage so that the phase of the system and the phase of single-phase inverter of PWM voltage type can be synchronized. And, It controlled in order to provide stable pier to the load and the system through maintaining high lurer factor and low output power of harmonics.

• Journal of the Korean Society of Radiology
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• v.4 no.3
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• pp.31-37
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• 2010

In this paper, a photovoltaic system is designed with PWM(Pulse Width Modulation) voltage source inverter. Proposed synchronous signal and control signal was processed by 56F8323 microprocessor for stable modulation. The PWM voltage source inverter using inverter consists of complex type of electric power converter to compensate for the defect, that is solar cell cannot be developed continuously by connecting with the source of electric power for ordinary use. It can cause the effect of saving electric power, from 10 to 20[%]. The PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. In addition, I connected extra power to the system through operation the system voltage and inverter power in a synchronized way by extracting the system voltage so that the phase of the system and PWM voltage inverter can be synchronized. In the system of this research showed good results after being controlled in order to provide stable power to the load and the system through maintaining and low output power of harmonics.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.85-87
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• 2000

In real-time power system control, it is essential to measure the power system variables which are voltage. current, real and reactive power, power factor, system frequency and etc. this variables can be estimated or calculated by the synchronized phasor informations of voltage and current. Therefore, the synchronized phasor measurement of voltage and current is very important to real-time power system control. So, we develop SPMD(Synchronized Phasor Measurement Device) for synchronized phasor measurement of voltage and current. In this paper, we present the design and implementation of SPMD for real-time phasor measurement and prove its performance by the test results.

• Journal of Yeungnam Medical Science
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• v.6 no.2
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• pp.217-222
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• 1989

In this study, high frequency oscillatory ventilator was designed and constructed. Using designed by phase-lock loop system, in order to accurately and easily treat both the outlet volume and rpm. A system has been designed and is being evaluated using CD4046A PLL IC. We use this PLL IC for the purpose of motor controls. The device consists of PLL system, pumping mechanism, piston, cylinder, and special crank shaft are required. This system characteristics were as follows : 1) Frequency : 20-1800rpm. 2) Outlet air volume : 1-50cc.