• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.233-235
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• 2000

SVC(Static Var Compensator) is commonly installed with conventional mechanically switched existing reactor or capacitor banks for wide range voltage control. The frequencies of switching of external banks have a great impact on the quality of voltage, but is limited since the life time of the external banks depends severely on the number of switching. So it is a complete multi-objective nonlinear optimization problem with conflicting objectives. This paper presents a method to determine the optimal coordination of SVC and external banks using genetic algorithm based on the multi-objective criteria. Optimal dead band and delay time of external banks is sought for reliable and efficient operation

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.159-162
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• 2002

A software, called touch-one, is developed about the determination of short-circuit values and protective co-ordination in power system. The used solution algorithm reviewed intensively, and the protective co-ordination determination technique presented by using the circuit-breaker's current-limitation characteristic. The protective coordination concerns the behaviour of two devices placed in series in an electrical network, with a short-circuit downstream circuit-breaker. It has two basic principles: First, discrimination which is an increasing requirement of low voltage electrical distribution systems. Second, which is less well known: cascading, which consists of installing a device, whose breaking capacity is less than the three-phase short-circuit current at its terminals and helped by main circuit-breaker. With this software, we can construct a electric-power system which is reliable and economic according to user's purpose.

• 전기학회논문지
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• 제64권1호
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• pp.176-181
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• 2015

In the DC electric railway system, the effective use of regenerative break energy is an important issue. Since regenerative break energy causes voltage rise or drop in the system, it should be also solved effectively. To solve the problems, applying electric double layer capacitor (EDLC) or voltage source converter (VSC) to the DC electric railway system has been studying. In this paper, the coordination of EDLC and VSC is proposed to solve the problem effectively with its coordinated control algorithm. The proposed method is tested to show its feasibility using Matlab/Simulink.

• Journal of Communications and Networks
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• 제12권1호
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• pp.43-51
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• 2010

IEEE 802.11 defines distributed coordination function (DCF), which is characterized by CSMA/CA and binary exponential backoff (BEB) algorithm. Most modifications on DCF so far have focused on updating of the contention window (CW) size depending on the outcome of own frame transmission without considering freezing periods experienced in the backoff interval. We propose two simple but novel schemes which effectively utilize the number of freezing periods sensed during the current backoff interval. The proposed schemes can be applied to DCF and its family, such as double increment double decrement (DIDD). Saturation throughput of the proposed schemes is analyzed by means of Bianchi's Markovian model. Computer simulation validates the accuracy of the analysis. Numerical results based on IEEE 802.11b show that up to about 20% improvement of saturation throughput can be achieved by combining the proposed scheme with conventional schemes when applied to the basic access procedure.

• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2004년도 봄 학술발표논문집 Vol.31 No.1 (A)
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• pp.505-507
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• 2004

IEEE 802.11 무선랜 표준에서 MAC(Media Access Control)은 동기와 비동기의 두 가지 타입의 서비스를 지원한다. 동기적 실시간 트래픽은 PCF(Point Coordination Function)에 의해서 폴링 엑세스 기법에 의해 처리된다. 비동기적 비실시간 트래픽은 CSMA/CA 프로토콜 기반의 DCF(Distributed Coordination function)에 의해 처리된다. 그래서 실시간 트래픽은 지연과 패킷손실에 민감하고 비실시간 트래픽은 에러와 처리율에 민감하기 때문에 적당한 트래픽 스케줄링 알고리즘이 설계되어질 필요가 있다. 하지만 IEEE 802.11 무선랜 표준은 실시간 트래픽을 효율적으로 서비스를 해주지 못하고 있다. 그래서 본 논문에서는 PCF 구간내에서 서비스를 받지 못한 실시간 트래픽 스테이션들을 DCF 구간에서 우선적으로 서비스함으로써 QoS를 향상시킬 수 있다.

• Journal of electromagnetic engineering and science
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• 제15권1호
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• pp.14-19
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• 2015

In multicellular wireless networks, intercell interference limits system performance, especially cell edge user performance. One promising approach to solve this problem is the intercell interference coordination (ICIC) scheme. In this paper, we propose a new ICIC scheme based on a resource partitioning approach to enhance cell edge user performance in a wireless multicellular system. The most important feature of the proposed scheme is that the algorithm is performed at each base station in a distributed manner and therefore minimizes the required information exchange between neighboring base stations. The proposed scheme has benefits in a practical environment where the traffic load distribution is not uniform among base stations and the backhaul capacity between the base stations is limited.

• 한국산학기술학회논문지
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• 제22권1호
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• pp.768-776
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• 2021

LVDC 배전계통에서 DC전원의 공급을 위한 컨버터나 DC차단기의 보호동작은 AC 보호기기 보다 훨씬 빠르기 때문에, 기존의 T-C곡선의 반 한시특성에 의한 보호기기간의 보호협조 운용이 어려운 문제점을 가지고 있다. 따라서, 본 논문에서는 LVDC 배전계통에서 사고지점에 따라 다양하게 나타날 수 있는 사고전류의 경사각 개념에 대하여 정의하고, 이를 바탕으로 컨버터와 보호기기간의 협조동작을 신속 정확하게 수행하고, 정전구간의 범위를 최소화할 수 있는 LVDC 배전계통의 사고구간분리 보호협조 알고리즘을 제안한다. 즉, LVDC 배전계통에서의 사고전류가 선로정수에 의해 사고지점에 따라 비례적으로 변하는 경사각의 특성을 이용하여 메인 컨버터가 탈락되기 전에 사고구간을 선택적으로 분리하도록 한다. 또한, 본 논문에서는 배전계통 상용해석 프로그램인 PSCAD/EMTDC를 이용하여 배전용 변전소, LVDC용 컨버터 그리고 LVDC 배전선로로 구성된 1.5kV급 LVDC 배전계통 모델링을 수행한다. 이를 바탕으로 사고지점에 따른 경사각 특성 및 보호협조 운용알고리즘을 분석한 결과, 메인 컨버터가 탈락하기 전 사고구간만을 2ms 이내에 분리하고 건전구간의 수용가에 미치는 영향을 최소화 할 수 있어, 본 논문에서 제안한 사고구간분리 보호협조 운용 알고리즘이 유용함을 확인하였다.

• Journal of Electrical Engineering and Technology
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• 제12권1호
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• pp.110-116
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• 2017

This paper proposed a new real-time parameter tracking algorithm. Unlike the convenience algorithms, the proposed real-time parameter tracking algorithm can estimate parameters through three-phase voltage and electric current without coordination transformation, and does not need information on magnetic flux. Therefore, it can estimate parameters regardless of the change according to operation point and cross-saturation effect. In addition, as the quasi-real-time parameter tracking technique can estimate parameters through the four fundamental arithmetic operations instead of complicated algorithms such as numerical value analysis technique and observer design, it can be applied to low-performance DSP. In this paper, a new real-time parameter tracking algorithm is derived from three phase equation. The validity and usefulness of the proposed inductance estimation technique is verified by simulation and experimental results.

• 전기학회논문지
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• 제59권5호
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• pp.854-859
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• 2010

Distribution Automation System(DAS) is designed to improve operational efficiency by acquisition and control of remote data using its components such as central computation units, communication network and feeder remote terminal units. A conventional human machine interface of the DAS adopts a schematic diagram which is made by drawing power equipments on the geographic information system map. The single line diagram is more useful than the schematic diagram for the main tasks of distribution system operation such as protective relay coordination, service restoration and loss minimization. Since the configuration of the distribution line is changed according to the relocation of the open tie switches, the auto-drawing algorithm based on the connection between the sections and the switches is an essential technique. This paper proposes a new auto-drawing algorithm for a single line diagram of distribution systems based on tertiary tree and collision avoidance method. The feasibility of the proposed algorithm has been testified for various cases using practical distribution system with 12 feeders.

• ETRI Journal
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• 제34권2호
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• pp.159-167
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• 2012

In this paper, a new distributed resource allocation algorithm is proposed to alleviate the cross-tier interference for orthogonal frequency division multiplexing access macrocell and femtocell overlay. Specifically, the resource allocation problem is modeled as a non-cooperative game. Based on game theory, we propose an iterative algorithm between subchannel and power allocation called distributed resource allocation which requires no coordination among the two-hierarchy networks. Finally, a macrocell link quality protection process is proposed to guarantee the macrocell UE's quality of service to avoid severe cross-tier interference from femtocells. Simulation results show that the proposed algorithm can achieve remarkable performance gains as compared to the pure waterfilling algorithm.