• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.395-399
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• 1996

The Clamp Mode(CM) Forward Zero Voltage Switching Multi Resonant Converter(ZVS-MRC) with self-driven synchronous rectifier in studied. The loss at the synchronous rectification stage of the converter is analyzed using MOSFET linear model and is compared with the loss at the conventional schottky diode rectification stage of the converter. From the results of the analysis, it is known that the use of MOSFETs as a synchronous rectifier reduces the loss at the rectification stage over the whole load range comparing the use of schottky diodes as a conventional rectifier in the converter. In order to verify the validity of the analysis, we have built a 33W(3.3V/10A) CM Forward ZVS-MRC with self-driven synchronous rectifier, in which switching frequency is 1MHz, and tested. From the experimental results, it is known that the synchronous rectification achieved about 1W improvement in the loss at the rectification stage and about 3% in the efficiency at the converter as compared with the conventional schottky diode rectification.

• 에너지공학
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• 제11권3호
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• pp.230-236
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• 2002

전력계통 실시간 제어에서는 전압, 전류, 유효전력, 무효전력, 역률, 시스템 주파수 등 전력계통 변수들을 측정하는 것이 중요하다. 이 변수들은 전압과 전류의 동기화된 페이저 정보부터 추출할 수 있다. 따라서 전압 및 전류의 동기화된 페이저 측정은 실시간 전력계통 제어에서 매우 중요한 역할을 한다. 이런 이유로 동기위상측정장치가 개발되었고 본 논문에서는 동기위상측정장치의 설계와 구현한 것을 제시하였고 제작된 시작품을 RTDS(Real-time Digital Simulator)와 실험실에 있는 380 V 3상 배전계통에 적용하여 측정된 실험결과를 통해 개발된 시작품의 성능을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.179-181
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• 2003

Conventional P/PI speed controller of today's servo drives should be manually tuned the controller switching set-point by trial-and-errors, which may translate the drive system down-time and loss of productivity. The adjustable drive performance is heavily dependent on the qualify of the expert knowledge and becomes inadequate in applications where the operating conditions change in a wide range, i.e., tracking command, cceleration/deceleration time, and load disturbances. In this paper, the demands on simple controls/setup are discussed for industry servo drives. Analyzing the frequency content of motor torque command, P/PI control mode switching is automatically peformed with some prior knowledge of the mechanical dynamics. The dynamic performance of the proposed scheme assures a desired tracking response curve with minimal oscillation and settling time over the whole operating conditions. For comprehensive comparison of traditional P/PI control scheme, extensive test is carried out on actual servo system.

• 생물환경조절학회지
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• 제23권3호
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• pp.174-180
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• 2014

Standard weather data available to greenhouse environmental design are limited in most regions of the country. So, instead of using standard weather data, in order to find the method to build design weather data for greenhouse heating and cooling, design outdoor weather conditions were analyzed and compared by TAC method and frequency analysis using climatological normal and thirty years from 1981 to 2010 hourly weather data provided by KMA and standard weather data provided by KSES. Average TAC values of outdoor temperature, relative humidity and insolation using thirty years hourly weather data showed a good agreement with them using standard weather data. Therefore, in regions which are not available standard weather data, we suggest that design outdoor weather conditions should be analyzed using thirty years hourly weather data. Average of TAC values derived from every year hourly weather data during the whole period can be established as environmental design standards, and also minimum and maximum of them can be used as reference data.

• 한국기계가공학회지
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• 제4권4호
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• pp.39-47
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• 2005

In this paper, a novel high power micropump using active check valves in place of conventional passive check valves employed at the inlet and outlet ports is presented. It actively controls open/close motion of check valves using piezoelectric actuator for expansion/contraction of pump chamber. A prototype micropump having an effective size of $17mm{\times}8mm{\times}11mm$ is fabricated. Frequency-dependent flow rate characteristics, bi-directional flow characteristics and load characteristics are experimentally investigated using a timing control method for valve closing motion. From the obtained experimental results, it is ascertained that optimal values of the phase shift compared to the voltage to drive pump chamber are $15^{\circ}$ for inlet check valve and $195^{\circ}$ for outlet. Based on the obtained results, a sheet-type active shuttle valve that has a unified valve-body for inlet and outlet check valves is proposed. A micropump with an effective size of $10mm{\times}10mm{\times}10mm$ is fabricated and the basic characteristics are experimentally investigated.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.133-135
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• 2004

As a result of the recent advances in magnetic materials, the Magnetic Amplifier(Magamp) technique is one of the reliable and cost-effective postregulation method for multiple-output power supply. This is true for high-current postregulated output since at highter output current the efficiency of linear postregulation is unacceptably low, while the complexity of more efficient switch mode postregulator is associated with a significant cost. Magamp have some advantages of higher power density, simple control circuit, good regulation, high frequency and high performance. In this paper, Operation principle of proposed approach and a performance of magamp control circuit with TL431 is described. The comparative analysis of magamp circuit and buck regulator circuit with 20W load condition is conducted. Experimental verifications on multi-output flyback converter are conducted. Simulations and experimental results show that the proposed approach is efficiency and voltage regulation of the auxiliary output is excellent.

• 한국자동차공학회논문집
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• 제16권3호
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• pp.23-29
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• 2008

It is necessary to develope the active safety system in terms of driver's safety and convenience. In this paper, we were developed the non-contact type of safety window system operated by the initial value of feedback control such as the output signal of photo sensor. It was designed based on the control algorithm with an improved load sensitivity. Therefore, compared with the existing system, it is possible to prevent the occurrence of a mull-function. Also, it has a convenient functions of the window such as an auto up/down and closing, and has a response times better. It can be installed the various types of common vehicles that have the different movement distance and speed of window. In conclusion, the developed system may be adapted the vehicle commercially.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.197-208
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• 2010

Unified power flow controller (UPFC) is the most reliable device in the FACTS concept. It has the ability to adjust all three control parameters effective in power flow and voltage stability. In this paper, a linearized model of a power system installed with a UPFC has been presented. UPFC has four control loops that by adding an extra signal to one of them, increases dynamic stability and load angle oscillations are damped. In this paper, after open loop eigenvalue (electro mechanical mode) calculations, state-space equations have been used to design damping controller and it has been considered to influence active and reactive power flow durations as the input of damping controller, in addition to the common speed duration of synchronous generators as input damper signal. To increase stability, further Lead-Lag and LQR controllers, a novel on-line adaptive controller has been used analytically to identify power system parameters. Closed-loop calculations of the electro mechanical mode verify the improvement of system pole placement after controller designing. Suitable operation of adaptive controller to decrease rotor speed oscillations against input mechanical torque disturbances is confirmed by the simulation results.

• 전력전자학회논문지
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• 제19권4호
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• pp.303-311
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• 2014

This paper shows the test result of 2MVA BESS(Battery Energy Storage System) with wind-turbine in micro-grid of the Gapado. To implement of micro-grid with BESS, characteristics of generator and customer load in grid are considered. Also, to operate of 2-parallel PCU(Power Conversion Unit) in BESS, the droop control is adopted with operating mode of grid independent. Performances of BESS with wind-turbine were verified by analysis of power quality such as voltage harmonics, ratio of voltage and frequency regulation, and by measurement of waveform such as output voltage and current.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4469-4474
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• 2014

본 논문에서는 유한요소법을 사용하여 자기부상열차용 선형 유도 전동기의 효율적인 운전곡선 도출 방법을 제안한다. 긴 시간의 동특성 해석을 위해 선형유도기 모델을 선형에서 회전형 타입으로 변환하고, 제어시 필요한 슬립 파라미터를 전자장 해석을 통하여 효과적으로 도출하였다. 견인용 선형유도전동기는 인버터에 의해 저속의 정토크 영역에서는 전압/주파수 (V/f) 일정제어를 수행하고, 고속에서의 정출력 영역에서는 전압을 고정시키고 주파수를 증가시키면서 제어한다. 따라서 논문에서는 정토크 및 정출력 영역의 운전 특성을 도출하기 위해 각 구간에서 일정한 스텝으로 슬립특성 곡선을 도출하고, 차량의 운전 상태에 따른 슬립 및 주파수를 특성곡선의 보간법에 의해 결정한다. 본 방법을 이용하면 차량의 임의의 부하상태에 따라 최적의 운전 지령을 제시할 수 있다.