• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.549-556
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• 2014

This study proposes a parallel operation strategy for small wind turbine systems. A small wind turbine system consists of blade, permanent magnet synchronous generator, three-phase diode rectifier, DC/DC buck converter, and the battery load. This configuration has reliability, simple control algorithm, high efficiency, and low cost. In spite of these advantages, the system stops when unexpected failures occur. Possible failures can be divided into mechanical and electrical parts. The proposed strategy focuses on the failure of electrical parts, which is verified by numerical analysis through equivalent circuit and acquired general formula of small wind power generation systems. Simulation and experimental results prove its efficiency and usefulness.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.55 no.4
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• pp.183-189
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• 2006

In this work, the digital simulator for testing of digital protective relay is presented. The proposed simulator software has EMTP simulation data file conversion, sequence waveform generation, user define simulation data generation, communication engine, data analysis engine and measurements function etc. The simulator hardware is designed using 32bit floating point DSP architecture to achieve flexibility and high speed operation. This simulator is tested to evaluate the performance of relay simulator by using a output data of simulation model on EMTP.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.907-908
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• 2006

The energy storage systems are being widely researched for the electric power. The operations running in a vacuum chamber mainly consists of a composite flywheel rotor, superconductor bearings, a motor/generator and its controller. Among composed the apparatus, the floating magnet bearing consists of the ring-type permanent magnets with epoxy resin impregnation for reinforcement and surface protection. In order to storage as much energy as possible, the flywheel is supposed to be rotated with very high speed. The magnetic field is analyzed by using the Maxwell 2D/3D for the simulations.

• Journal of ILASS-Korea
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• v.25 no.1
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• pp.15-20
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• 2020

This study aims to investigate injection rate and microscopic spray characteristics of diesel fuel containing fine air bubble (FBD). fine bubble was generated by cavitation theory using bubble generator. Fuel spray was injected into constant volume chamber and visualized by high speed camera. The injection rate data was acquired with bosch tube method. Injection rate of finebubble diesel was very similar with that of diesel. It showed slightly faster injection start by 5 ㎲ attributed to the low viscosity characteristics. In microscopic spray visualization, fine bubble diesel spray showed unsymmetric spray shape compared with diesel spray. It also showed very vigorous spray atomization performance during initial spray development. Improved atomization was also attributed to the low viscosity and surface tension of finebubble diesel fuel.

• Corrosion Science and Technology
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• v.10 no.4
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• pp.151-155
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• 2011

The iron oxide particles could be resulted from the corrosion of the circulating water system of a power plant. Because it may be one of the trouble materials which affect the power generation efficiency due to the deposition on steam generator tube and turbine blade, the continuous observation of its concentration is very important. The laser induced break-down detection (LIBD) technology was applied to monitor continuously the concentration of corrosion products with the detection limit of ppb level. The measurement system consists of a Nd:YAG pulsed laser, a polarizing beam splitter, a flow-type sample cell, an acoustic emission sensor, a high speed data acquisition board, a personal computer, etc.. The performance test results confirmed that this technology can be effective to monitor the corrosion product concentration of the circulating water system of a power plant.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.605-606
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• 2006

Voltage Controlled Oscillator(VCO) plays an important role in today's communication systems. Especially, a Clock Generator(CG) in phase-locked loop(PLL) is usually realized by the VCO. This paper proposes a new VCO with a controllable duty cycle buffer, that can be adopted in low-power high-speed communication systems. Delay cell of the VCO is implemented with gilbert cell. Frequency dynamic range of the VCO is in the range of approximately $50MHz{\sim}500MHz$. Parameters with N-well CMOS 0.18-um process with 1.8V supply voltage was used for the simulations.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.200-204
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• 1996

It is a great number of problem for the man to perform maintenance and repairing work owing to radioactive effusion for a nuclear fuel and the pollution of an related equipment in nuclear power plants. Therefore, the vision processing system presented in this research requires to maintain the good performance under the radioactive circumstances and to safety the real time processing system presented in this research requires to maintain the good performance under the radioactive circumstances and to safety the real time processing. The proposed vision scheme adapts the gradient and Laplacian operator to perform the high speed processing in an edge detection and the centroid formula at each direction to obtain the center position of a holes using DSPs

• Journal of Electrical Engineering and Technology
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• v.5 no.1
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• pp.28-35
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• 2010

This paper presents new Adaptive Linear Combination Structure (ADALINE) for tracking/estimating voltage-current phasor and frequency of power system. To estimate the phasors and frequency from sampled data, the algorithm assumes that orthogonal coefficients and speed of angular frequency of power system are unknown parameters. With adequate sampled data, the estimation problem can be considered as a linear weighted least squares (LMS) problem. In addition to determining the phasors (orthogonal coefficients), the procedure estimates the power system frequency. The main algorithm is verified through a computer simulation and data from field. The proposed algorithm is tested with transient and dynamic behaviors during power swing, a step change of frequency upon islanding of small generators and disconnection of load. The algorithm shows a very high accuracy, robustness, fast response time and adaptive performance over a wide range of frequency, from 10 to 2000 Hz.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1015-1016
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• 2007

원격 전력 시스템의 요구 증가로 인해 작고 효율적이며 경제성도 우수한 풍력 발전기의 시장이 확대되고 있다. 이러한 응용 분야를 위해서 최근 들어 직접 구동 영구자석 발전기에 많은 관심을 가지게 되었다. 본 논문에서는 유한요소해석을 이용한 저속, 고토크의 외전형 직접 구동 영구자석 풍력발전기 개발을 위한 설계 모델을 제안하였다. 여기서 발전기의 코깅 토크의 분석을 통하여 기동 토크를 최소화하는데 대한 연구를 수행하였다. 또한 역기전력과 동기리액턴스, 효율을 계산하였다. 설계 모델을 토대로 3kVA, 90rpm의 풍력발전기 시제품을 제작하였다. 마지막으로 시제품의 성능 시험 결과를 통하여 해석모델의 정확성을 증명하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.369-372
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• 2002

In this research, a vision system for detecting tool breakage which is hardly detected by such indirect in-process measurement method as acoustic emission, cutting torque and motor current was developed and embedded into a PC-NC system. The vision system consists of CMOS image sensors, a slit beam laser generator and an image grabber board. Slit beam laser was emitted on the tool surface to separate the tool geometry well from the various obstacles surrounding the tool. An image of tool is captured through two steps of signal processing, that is, median filtering and thresholding and then the tool is estimated normal or broken by use of change of the centroid of the captured image. An air curtain made by the jetting high-pressure air in front of the lens was devised to prevent the vision system from being contaminated by scattered coolant, cutting chips in cutting process. To embed the vision system to a Siemens PC-NC controller 840D NC, an HMI(Human Machine Interface) program was developed under the Windows 95 operating system of MMC103. The developed HMI is placed in a sub window of the main window of 840D and this program can be activated or deactivated either by a soft key on the operating panel or M codes in the NC part program. As the tool breakage is detected, the HMI program emit a command for automatic tool change or send alarm to the NC kernel. Evaluation test in a high speed tapping center showed the developed system was successful in detection of the small-radius tool breakage.