• 대한전기학회논문지:전력기술부문A
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• 제54권8호
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• pp.418-428
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• 2005

In this paper, a new probabilistic generation modeling method which can address the characteristics of changed electricity industry is proposed. The major contribution of this paper can be captured in the development of a probabilistic generation modeling considering generator maintenance outage and in the classification of market demand into multiple demand clusters for the applications to electricity markets. Conventional forced outage rates of generators are conceptually combined with maintenance outage of generators and, consequently, effective outage rates of generators are newly defined in order to properly address the probabilistic characteristic of generation in electricity markets. Then, original market demands are classified into several distinct demand clusters, which are defined by the effective outage rates of generators and by the inherent characteristic of the original demand. We have found that generators have different effective outage rates values at each classified demand cluster, depending on the market situation. From this, therefore, it can be seen that electricity markets can also be classified into several groups which show similar patterns and that the fundamental characteristics of power systems can be more efficiently analyzed in electricity markets perspectives, for this classification can be widely applicable to other technical problems in power systems such as generation scheduling, power flow analysis, price forecasts, and so on.

• 전기학회논문지
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• 제66권12호
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• pp.1712-1720
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• 2017

In South Korea, minimum reserve rate, which is to satisfy reliability standard, has been determined by simulation result using WASP. But, it is still controversial whether the level of minimum reserve rate is adequate. Thus, in this study, various analyses of minimum reserve rate are being conducted. WASP uses the probabilistic simulation technique to evaluate whether reliability standard is satisfied. In this process, forced outage rate and maintenance periods of each generator play important roles. Especially, the long-term plan can be varied depending on how maintenance periods deal with. In order to model maintenance periods in the probabilistic simulation technique, WASP uses derating method. However, broad analyses have to be conducted because there are various ways including derating method to model maintenance periods which result in different results. Therefore, in this paper, 3 different maintenance outage rate modeling methods are applied to arbitrarily modeled system based on the basic plan for long-term electricity supply and demand of South Korea. Results show impact of each modeling method on minimum reserve rate.

• Journal of Astronomy and Space Sciences
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• 제37권4호
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• pp.219-228
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• 2020

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.153-154
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• 2008

In this paper, we propose a diversity-enhancing scheme in a single link fading channel using repetition QPSK symbol code. The proposed scheme can be converted to rate outage formula and obtains enhanced diversity performance while guaranteeing the required data rate. Simulation result shows that the proposed scheme improves the rate outage performance compared to the conventional BPSK diversity schemes.

• ETRI Journal
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• 제32권1호
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• pp.139-141
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• 2010

In this letter, closed-form approximations for outage probability and symbol error rate are presented for a selective decode-and-forward relay network with partial channel information. An independent but not identically distributed Rayleigh fading environment is considered. Numerical and simulated results demonstrate the validity of the analytical results.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권6호
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• pp.1606-1626
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• 2012

This paper investigates the performance of an amplify-and-forward (AF) two-way relaying system with antenna correlation. The system consists of two multiple-antenna sources, which exchange information via the aid of a single-antenna relay. In particular, we derive the exact outage probability expression. Furthermore, we provide a simple, tight closed-form lower bound for the outage probability. Based on the lower bound, we obtain the closed-form asymptotic outage probability and the average symbol error rate expressions at high signal-to-noise ratio (SNR), which reveal the system's diversity order and coding gain with antenna correlation. To investigate the system's throughput performance with antenna correlation, we also derive a closed-form lower bound for the average sum-rate, which is quite tight from medium to high SNR regime. The analytical results readily enable us to obtain insight into the effect of antenna correlation on the system's performance. Extensive Monte Carlo simulations are conducted to verify the analytical results.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.195-198
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• 2004

In recent, the Importance and necessity of some studies on reliability evaluation of grid comes from the recent black-out accidents occurred in the world. The quantity evaluation of transmission system reliability is very important under competitive electricity environment. Accurate probabilistic reliability evaluation depends on assessment of forced outage rate of elements, generators, transmission lines. This paper describes basic theory of relationship between outage rates and reliability evaluation for assessing FOR(forced outage rate) of elements of power system. In case study, FORs assessed and supplied from Canada Electricity Association is introduced and FORs assessed from using actual historical data from 1997 to 2002 for transmission lines of KEPCO system.

• 한국통신학회논문지
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• 제40권12호
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• pp.2443-2449
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• 2015

단말이 망에서 제공받는 데이터 전송율은 단말과 셀 사이의 SINR 뿐만 아니라 셀이 단말에게 할당하는 무선 자원양에 의해서도 결정된다. 따라서 단말이 SINR만을 기준으로 접속할 셀을 선택하면 비록 최대 SINR을 제공하는 셀에 접속한다고 하더라도 최대 서비스율을 제공받지 못할 수도 있다. 또한 네트워크의 입장에서는 SINR을 기준으로 접속 셀이 선택되므로 일부 셀들은 다수의 단말이 접속하는 반면 주변의 다른 셀들은 접속 단말의 수가 적게 되어 셀간 부하 불균형 상태가 발생될 확률이 커지고 이로 인해 이동 통신 시스템의 자원 이용율이 낮아지게 된다. 이에따라 본 논문에서는 SINR뿐만 아니라 셀의 부하를 고려한 접속 셀 선택 방법을 제안한다. 이를 위해 접속 셀 선택 지표로 SINR 대신에 최대 데이터 전송율과 최소 전송율 단절 확률을 제시한다. 제안 기법의 성능 평가를 위한 모의실험 결과 최대 데이터 전송율을 이용한 셀 선택 방법은 타 기법에 비해 시스템 효율과 셀간 부하 균등 측면에서 향상된 성능을 보였으며 최소 전송율 단절 확률을 이용한 셀 선택 방법은 타 기법에 비해 단말의 평균 전송율 단절 확률 측면에서 향상된 성능을 보였다.

• 전기전자학회논문지
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• 제23권1호
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• pp.188-192
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• 2019

전기저장장치가 주파수조정예비력 자원으로써 전력계통 운영에 대한 기여도가 증가됨에 따라 전기저장장치 설비용량의 신뢰성 확보가 요구되고 있으며, 이를 위해서는 전기저장장치의 가용용량에 고장률을 고려할 필요가 있다. 그러나 기존의 전기저장장치 고장률 산정방안은 전기저장장치 설비의 구조적 특징을 정확히 고려하지 못해 전기저장장치의 가용용량을 정확히 반영하지 못하고 있다. 본 논문에서는 전기저장장치 설비의 특징을 분석하고 이를 반영한 전기저장장치의 고장률 산정방안을 제안하였고 사례연구를 통하여 제안된 방안의 유효성을 검토하였다.

• 조명전기설비학회논문지
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• 제22권10호
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• pp.118-125
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• 2008

송전선로에 발생하는 정전은 산업계에 큰 영향을 미치고 있다. 특히 낙뢰에 의한 송전선로의 사고는50[%]를 넘고 있다. 송전선로에 발생하는 낙뢰에 의한 정전을 줄이기 위해서는 경제적인 관점을 고려하여 보강대책을 수립하는 것이 중요하다. 송전선로의 신뢰도는 보통 연간 100[km]당 몇 건의 낙뢰에 의한 사고가 발생하는가에 의해 결정되므로, 낙뢰에 대한 보호 대책을 수립하기 위해서는 뇌 사고율을 정확하게 예측하는 것이 필요하다. 낙뢰에 의한 절연물의 섬락현상은 대단히 복잡한 전기자기적 현상이다. 또한 송전선로의 뇌 사고율을 계산하기 위해서는 수많은 반복계산이 요구된다. 따라서 프로그램의 개발이 요구되며, 본 논문에서는 송전선로 뇌 사고율 계산을 위한 기본개념 및 개발된 프로그램을 검증하였다.