• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.268-270
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• 2002

본 논문에서는 댐핑이 고려된 전력계통에서 동요시 안정도를 향상시킬 수 있는 확장된 PI제어를 이용한 조속기 제어기를 제안하였다. 전력계통에서의 동요는 대부분 고장기간 동안에 발전기에 저장된 과잉운동에너지에 의해 발생한다. 계통이 안정하도록 하기 위해서 과잉에너지를 효과적으로 다루려면 보통 직접법을 사용된다. 과잉에너지를 제어하기 위한 직접적인 방법으로는 LFC(Load Frequency Control)의 궤한이 활용된다. 확장된 PI제어 방식이 적용된 제어기는 지역내에서와 지역사이에서의 동요를 감쇄시키기 위한 조속기에 적용될 수 있다 또한 제안된 제어기는 조속기에 스팀밸브 제한 조건이나 발전율 제약조건(Generation Rate Constraint; GRC)과 같은 특이점이 존재할 때에도 우수한 성능을 보여주었다. 시뮬레이션은 두지역의 다기계통에서 부하를 변화시켜가며 실시하였다. 시뮬레이션 결과는 제안된 PI 제어기를 기존의 PI 제어기와 비교하여 매우 향상된 성능을 보여주었다.

• Journal of Biosystems Engineering
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• 제11권2호
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• pp.77-87
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• 1986

This study was carried out to design the optimal systems of diversified farming by the mathematical model developed. In order to achieve this goal, a computer program named DFSDINGP was developed by the nonlinear goal programming(NGP), and for testing its effectiveness, the optimal systems of diversified farming were designed for three regions surveyed and compared them with those of the conventional. DFSDINGP was programmed with FORTRAN 77 and it could handle the NGP problem having 25 independent variables and 75 constraint functions. The study results showed that the developed models and DFSDINGP could design the optimal systems of diversified farming satisfying two goals which are maximum agricultural income and maximum power inputs of agricultural machinery. The agricultural incomes and power inputs of farm machinery of the optimal systems were more than those of the conventional as much as 29-62% and 9-134%, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권7호
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• pp.3171-3191
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• 2016

Due to growing demand on wireless data traffic, a large number of different types of base stations (BSs) have been installed. However, space-time dependent wireless data traffic densities can result in a significant number of idle BSs, which implies the waste of power resources. To deal with this problem, we propose an active state control algorithm based on semi-Markov decision process (SMDP) for a heterogeneous network. A MDP in discrete time domain is formulated from continuous domain with some approximation. Suboptimal on-line learning algorithm with a random policy is proposed to solve the problem. We explicitly include coverage constraint so that active cells can provide the same signal to noise ratio (SNR) coverage with a targeted outage rate. Simulation results verify that the proposed algorithm properly controls the active state depending on traffic densities without increasing the number of handovers excessively while providing average user perceived rate (UPR) in a more power efficient way than a conventional algorithm.

• 대한전기학회논문지
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• 제33권3호
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• pp.91-99
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• 1984

Time-optimal control for dmping a one-dimensional xenon-induced spatial power oscillations in pressurized water reactor is studied. Linearized system equations describing the spatial xenon oscillations have been derived based on lambda mode analysis. Optimal control strategies, eventually bang-bang controls, have been drawn applying Pontryagins Minimum Principle, subject to a band constraint on available contros strength. Validity of the linearized system equations and optimal control strategies derived has been demonstrated through conputer simulations which incorporate the finite difference method for one dimensional axial geometry, for the soulution of the two-group neutron diffusion equations. The results obtained through computer simulations show that xenon-induced transients can be suppressed successfully with bang-bang control.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.113-116
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• 1996

The drain current of the MOSFET in the off state(i.e., Id when Vgs=0V) is undesired but nevertheless important leakage current device parameter in many digital CMOS IC applications (including DRAMs, SRAMs, dynamic logic circuits, and portable systems). The standby power consumed by devices in the off state have added to the total power consumed by the IC, increasing heat dissipation problems in the chip. In this paper, hot-carrier-induced degra- dation and gate-induced-drain-leakage curr- ent under worse case in P-MOSFET\`s have been studied. First of all, the degradation of gate-induced- drain-leakage current due to electron/hole trapping and surface electric field in off state MOSFET\`s which has appeared as an additional constraint in scaling down p-MOSFET\`s. The GIDL current in p-MOSFET\`s was decreased by hot-electron stressing, because the trapped charge were decreased surface-electric-field. But the GIDL current in n-MOS77T\`s under worse case was increased.

• ETRI Journal
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• 제38권5호
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• pp.934-940
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• 2016

In this paper, secure multicasting with the help of cooperative decode-and-forward relays is considered for the case in which a source securely sends a common message to multiple destinations in the presence of a single eavesdropper. We show that the secrecy rate maximization problem in the secure multicasting scenario under an overall power constraint can be solved using semidefinite programing with semidefinite relaxation and a bisection technique. Further, a suboptimal approach using zero-forcing beamforming and linear programming based power allocation is also proposed. Numerical results illustrate the secrecy rates achieved by the proposed schemes under secure multicasting scenarios.

• Journal of Communications and Networks
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• 제18권3호
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• pp.320-326
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• 2016

In existing literature on multiple-input multiple-output (MIMO) relaying communication systems, antenna selection is often implemented by maximizing the channel capacity or the output single-to-noise ratio (SNR). In this paper, we propose an energy-efficient low-complexity antenna selection scheme for MIMO relaying communication systems. The proposed algorithm is based on beamforming and maximizing the Frobenius norm to jointly optimize the transmit power, number of active antennas, and antenna subsets at the source, relaying and destination. We maximize the energy efficiency between the link of source to relay and the link of relay to destination to obtain the maximum energy efficiency of the system, subject to the SNR constraint. Compared to existing antenna selection methods forMIMO relaying communication systems, simulation results demonstrate that the proposed method can save more power in term of energy efficiency, while having lower computational complexity.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1038-1045
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• 2017

To address mounting concerns over global warming, the Paris Agreement was reached in December 2015, which aims to limit the increase in global average temperature. South Korea has set a highly ambitious target to reduce emissions and submitted an Intended Nationally Determined Contribution (INDC). Based on the INDC, we investigated the impact of limiting carbon emissions on the power system and the electricity market in Korea. Through detailed simulations on assumed plausible scenarios, this work highlights a) the effects of different carbon emission targets on the annual carbon emission volumes, generation costs, and carbon price; b) the generation mix changes induced by carbon emission limits; and c) the difference in system marginal price and payments for generator owners that carbon emission constraint creates in electricity markets under three different pricing rules.

• 대한전기학회논문지:전력기술부문A
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• 제54권12호
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• pp.597-602
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• 2005

The introduction of competition in electricity market emphasizes the importance of sufficient transmission capacities to guarantee various electricity transactions. Therefore, when dispatch scheduling, transmission security constraints should be considered for the economic and stable electric power system operation. In this paper, we propose an optimal dispatch scheduling algorithm incorporating transmission security constraints. For solving these constraints, the dispatch scheduling problem is decomposed into a master problem to calculate a general optimal power flow (OPF) without transmission security constraints and several subproblems to inspect the feasibility of OPF solution under various transmission line contingencies. If a dispatch schedule given by the master problem violates transmission security constraints, then an additional constraint is imposed to the master problem. Through these iteration processes between the master problem and subproblems, an optimal dispatch schedule reflecting the post-contingency rescheduling is derived. Moreover, since interruptible loads can positively participate as generators in the competitive electricity market, we consider these interruptible loads active control variables. Numerical example demonstrates efficiency of the proposed algorithm.

• 한국산학기술학회논문지
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• 제19권5호
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• pp.632-639
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• 2018

최근 플러그인 전기자동차에 대한 적극적인 보급 정책이 추진되고 있으나 플러그인 전기자동차는 전력계통에 직접 연계되어 충전수요를 공급받기 때문에 충전수요의 집중도에 따라서는 전력계통의 설비확충이 요구될 수도 있다. 반면 전력계통의 설비확충은 많은 시간과 투자가 소요되어 현실적으로 제한될 수밖에 없기 때문에 기존의 전력망을 효율적으로 이용하여 플러그인 전기자동차의 충전수요를 안정적으로 공급하는 것은 플러그인 전기자동차의 보급 확대에도 중요한 요소라고 할 수 있다. 따라서 본 논문에서는 주어진 전력계통에서 선로조류와 모선전압과 같은 제약조건을 만족하면서 플러그인 전기자동차의 충전수요를 공급하기 위한 충전계획 수립방안을 제안한다. 이를 위해 자동차의 주행 패턴과 충전 요금제를 기준으로 플러그인 전기자동차 충전수요의 요구량과 충전 시작시간을 전기자동차별로 모델링 한 후 이를 전력계통 모델에 연계하여 조류계산을 계산하여 전력계통의 운전 상태를 모의하였다. 또한 선로의 전력조류와 모선의 전압에 대한 제약 조건의 만족 여부를 확인하며 제약조건에 위반이 발생하는 경우 이를 완화하기 위해 제약조건에 직접 관련된 플러그인 전기자동차의 충전수요를 조정하여 계통제약의 만족여부를 재확인하는 과정을 반복함으로써 주어진 전력계통의 제약조건을 만족할 수 있는 플러그인 전기자동차의 충전계획을 수립하였다.