• 한국통신학회논문지
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• 제30권4B호
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• pp.226-234
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• 2005

유비쿼터스 컴퓨팅에서 컨텍스트-인식은 사용자에게 개인화된 최적의 서비스를 제공하기 위하여 서비스 추론을 위한 입력 데이터를 획득하는 중요한 과정이다. 기존 연구는 사용자와 주변 환경 정보를 컨텍스트 인식의 주요대상으로 간주하고, 이를 위한 센싱 기반의 미들웨어나 공간 내의 대상에 식별자를 부여하여 이를 관리하는 서버를 제시하고 있다. 가정이나 사무실, 혹은 자동차와 같이 사용자가 많은 시간을 보내는 동일한 공간에서는 사용자에게 제공되었던 서비스의 일련적인 상황 정보가 개인화된 최적의 서비스를 추론하기 위한 중요한 요소가 될 수 있다. 본 논문은 사용자와 사용자에게 제공된 서비스 간에 일련의 상황 정보를 사용자의 휴대용 디바이스에 저장하고, 이를 컨텍스트-인식의 대상으로 확장하는 자생적 컨텍스트 모델을 제안한다. 제안 모델은 컨텍스트-인식 단계에서 발생하는 중복된 센싱과 불필요한 검색을 최소화하고 사용자의 익명성을 최대한 보장하며 미들웨어의 컨텍스트 관리를 비용을 줄인다.

• 대한전기학회논문지:전력기술부문A
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• 제50권8호
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• pp.388-394
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• 2001

This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.158-161
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• 2003

KERI simulator is a analog simulator for power system at KERI power system division lab. It consist of many power system components, which are a 380V 5kVA generators, scale-downed transmission line modules, transformers, switches, PACTS(Flexible AC Transmission System) devices. As a FACTS device module, 20kVA TCSC(Thyristor Controlled Series Compensator) module was designed and implemented. In this paper, we present the design and implementation of TCSC control hardware for KERI simulator

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.154-157
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• 2003

In this study, we design and implement the 20kVA TCSC(Thyrister Controlled Series Compensator) simulator It was tested on the KERI simulator The KERI simulator is a analog simulator for power system at the KERI power system division lab. It consist of many power system components, which are a 380V 5kVA generators, scale-downed transmission line modules, transformers, switches, FACTS(Flexible AC Transmission System) devices. In this paper, we present the design and implementation of 20kVA TCSC simulator and its basic test results.

• 한국정밀공학회지
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• 제14권4호
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• pp.15-21
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• 1997

Pneumatics is widly used in the industrial implementation, in the operation of air-powered actuators and the control devices needed in their operation. However, there are many empirical factors in pneumatics design, it might cause excessive design of pneumatic components. For that reason, we developed VDES(Vacuum Design Expert System) for the economic design of pneumatic vacuum equipment. VDES is achieved with CLIPS(C Language Integrated Production System) and knowledge base that contains a number of facts and rules for pneumatic vacuum design. Forward chaining and depth first search technique are used in this system. Appling VDES to the actual field, this system is verified to be a good efficiency and could be applied to the field of pneumatic vacuum equipment design.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 추계학술대회 논문집 전력기술부문
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• pp.217-219
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• 2008

Among the Flexible AC Transmission Systems (FACTS) devices, Unified Power Flow Controller (UPFC) is considered as the most powerful and versatile one as it provides simultaneous, real time control of the transmission parameters, voltages, impedances, and phase angles which determine the power flow in AC transmission systems. This paper presents modelling of UPFC and describes its characteristics. The UPFC implemented in this paper is based on Sinusoidal Pulse Width Modulation (SPWM) and Electro-Magnetic Transients Program (EMTP)/ATPDraw is used to model and analyze it. The simulation results confirm advantages of UPFC in operational performance with respect to the steady state Power flow regulation and the transient stability control.

• 조명전기설비학회논문지
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• 제24권12호
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• pp.193-200
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• 2010

In this paper, the eigenvalue sensitivity analysis is calculated in the power system which is including both generator controllers such as Exciter, PSS and thyristor controlled FACTS devices in transmission lines such as TCSC. Exciter and PSS are continuously operating controllers but TCSC has a switching device which operates non-continuously. To analyze both continuous and non-continuous operating equipments, the RCF method one of the numerical analysis method in discrete time domain is applied using discrete models of the power system. Also the eigenvalue sensitivity calculation algorithm using state transition equations in discrete time domain is devised and applied to a sampled system. As a result of simulation, the eigenvalue sensitivity coefficients calculated using discrete system models in discrete time domain are changed periodically and showed different values compared to those of continuous system model in time domain by the effect of periodic switching operations of TCSC.

• 전기학회논문지
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• 제56권5호
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• pp.829-833
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• 2007

In this paper, the RCF method is applied to analyze small signal stability of power systems including GTO controlled parallel FACTS equipments such as STATCOM. To apply the RCF method in power system small signal stability problems, state transition equations of generator, controllers and STATCOM are presented. In eigenvalue analysis of power systems, STATCOM is modelled as the equivalents voltage source model and the PWM switching circuit model. As a result of simulation, the RCF method is very powerful to calculate the oscillation modes exactly after the switching operations, and useful to analyze the small signal stability of power systems with periodically operated switching devices such as STATCOM.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.25-27
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• 2000

The unified flow controller(UPFC) is one of the most effective devices among the FACTS device family. In principle the UPFC is capable of controlling active and reactive power as well as the voltage magnitude can. Comparisons are made between the proposed and the existing UPFC models, which demonstrate the improvement in both flexibility and efficiency.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.332-334
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• 2005

This paper presents a dynamic simulation of the unified power flow controller (UPFC) using a current injection method. Flexible AC Transmission System (FACTS) devices give more flexibility of control for security and economic operation of power systems. Diffculties of modeling UPFC in the conventional dynamic simulation programs arise from the fact that the injected voltage by the series inverter is superimposed on the shunt inverter side voltage. A solution can be a current injection method, in which a serial part of UPFC is converted to a parallel equivalent circuit using source transformation, and two current sources affect each other at every time step. To verify efficiency of this method, the proposed model is applied for the transient analysis of an example power system.