• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.3
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• pp.206-211
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• 2004

In phase controlled rectifier, it's been known that a fast response is achieved by predictive current control without any overshoot. The frequent sampling period is essential to improve the firing accuracy in conventional predict current control. However, improving the firing accuracy if difficult to reduce the period of sampling efficiently because current sampling and predictive current control is carried out in every period and the ON-OFF current control is performed by comparing two different one. To improve the firing accuracy at the predictive current control, the calculated firing angle is loaded into the high-accuracy hardware timer. So the calculation of exact crossing point between the predictive and actual current is the most important. In this paper, the flow chart for proposed firing angle calculation algorithm is obtained for the fastest current control performance in transient state. The performance of proposed algorithm is verified through simulations and experiments.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1225-1230
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• 2004

The effects of substrate material on the local heating performance of microheaters are studied by both numerical analysis and experiment. Transient conduction analysis shows that the substrate material with low thermal conductivity is critical to the local heating and fast response. A measurement technique for surface temperature field in microscale is newly proposed, which uses temperature sensitive fluorescent dye coated on the surface. The measured surface temperature fields on microheater arrays fabricated on different substrates are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.201-208
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• 2002

In this paper, the control strategy of ratio changing system for a metal belt CVT adopting primary pressure regulation is developed, and the shirting performance of pressure regulating type CVT with the suggested control strategy is investigated. The control strategy suggested in this study is composed of 2 feedback loop, one is speed ratio feedback and the other is primary pressure feedback. The pressure feedback is adopted to ensure prohibiting a belt slip during transient period in a fast downshift mode. Simulation results show that the system with suggested control strategy gives appropriate response time and tracking Performance for upshift and also gives a proper primary pressure which can prohibit the belt slip. In addition, it is fecund that the given system has an acceptable servo property in tracking the target speed ratio and robustness for the disturbance of line pressure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1108-1112
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• 1999

In this paper, we propose an efficient ABR multicast algorithm for ATM networks. In ABR multicast algorithim, the feedback consolidation is necessary to avoid excessive backward resource management (BRM) cells and to aggregate the information from BRM cells received from each branch. The proposed scheme is shown to achieve fast transient response to the congestion status on a branch as well as effectively eliminate the consolidation noise through system simulation.

• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.529-538
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• 2015

Due to the high efficiency and compact mechanical structure, direct drive variable speed generators are used for power conversion in wind turbines. The wind energy conversion system (WECS) considered in this paper consists of a permanent magnet synchronous generator (PMSG), uncontrolled rectifier, dc-dc boost converter controlled with maximum power point tracking (MPPT) and adaptive hysteresis controlled voltage source inverter (VSI). For high utilization of the converter's power capability and stabilizing voltage and power flow, constant DC-link voltage is essential. Step and search MPPT algorithm which senses the rectified voltage ($V_{DC}$) alone and controls the same is used to effectively maximize the output power. The adaptive hysteresis band current control is characterized by fast dynamic response and constant switching frequency. With MPPT and adaptive hysteresis band current control in VSI, the DC link voltage is maintained constant under variable wind speeds and transient grid currents respectively.

• Proceedings of the KIPE Conference
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• 2014.11a
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• pp.9-10
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• 2014

최근 신재생에너지 및 전기자동차, 통신 IT 서버 전원 및 가전기기 등의 발전에 따라 고 전력밀도(High Power Density), 고 응답(Fast Transient Response) 및 고정밀(Tight Regulation) 출력제어를 위한 다 출력 절연형 DC/DC 컨버터가 개발 및 연구되고 있다. 본 논문에서는 개별적인 정밀제어를 요구하는 다 출력 DC-DC 컨버터에 대한 내용으로 위상천이(Phase-shift) DC-DC 컨버터와 LLC 공진컨버터 제어개념을 하나의 주회로를 사용하여 위상천이제어(Phase-shifted Modulation, PM)와 가변주파수제어(Variable Frequency Modulation, FM)를 통해서 개별적으로 정밀 제어할 수 있는 하이브리드 다 출력 3레벨 DC-DC 컨버터에 관한 내용이다.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1670-1672
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• 2001

In compared with air insulated switchgear GIS has a high efficiency and confidence. Insulation method using $SF_6$ gas has a very excellent insulation characteristics for high voltage equipment but has a characteristics that insulation heredity is changed for internal unequal electric field. So analysis of electromagnetic field in GIS is very important basic data for structure design and trouble diagnosis process. In compared with established method, SNM in this paper observes variation of the electromagnetic field with real time and get result very similar to measurement. In order to know the variation of electromagnetic field distribution for transient response for time and position, variations are observed when metal particles are moving fast.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.174-176
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• 2000

In this paper, a high speed distance relay, using a digital signal processor(DSP) is presented. The idea of the protective algorithm is based on the least square method using minimum data window to minimize the relay operating time. A new disign concept for a low-pass filter is proposed. This analog low pass filter has minimum transient response time. The main processor of the relay is TMS320C31. According to a series of real time tests, the proposed protective relay shows reliable and fast operating characteristics.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.155-156
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• 2015

Recently, electricity consumption has rapidly increased along with economic growth. The operating strategy using emergency generator is aimed, to resolve a demand response management. For strategy of peak shedding using emergency generator, it is essential to introduce the fast transfer switching device. One of the most effective solutions is to use a static transfer switch (STS) based on thyristor. However, the characteristic of natural commutated SCR thyristor should anticipate short duration voltage sag. STS system thus requires more than a quarter cycle to successfully complete transfer process. This paper proposes the operation scheme of the STS system using the forced-commutation technique to mitigate instantaneous voltage sag during peak transfer process. Proposed STS system improved turn-off characteristic thus accomplishes the peak load shedding satisfied power quality. Performance of the proposed STS system is evaluated using electromagnetic transient program (EMTP) to confirm the effectiveness.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.498-501
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• 1998

This paper deals with the design and evaluation of the robust controller for a synchronous generator excitation system to improve the steady state and transient stability. The nonlinear characteristics of the system is treated as model uncertainties, and then the robust control techniques are introduced into the power system stability design to take into account these uncertainties at the controller design stage. The performance of the designed controller is examined by extensive non-linear time domain simulation. It is shown that the performance of the robust controller is superior to that of the conventional PI controller.