• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.199-206
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• 2008

The introduction of competition in electricity markets emphasizes the importance of sufficient transmission capacities to guarantee effective power transactions. Therefore, for the economic and stable electric power system operation, transmission security constrains should be incorporated into the dispatch scheduling problem. With the intent to solve this problem, we decompose a dispatch scheduling problem into a master problem(MP) and several subproblems(SPs) using Benders decomposition. The MP solves a general optimal power flow(OPF) problem while the SPs inspect the feasibility of OPF solution under respective transmission line contingencies. If a dispatch scheduling solution given by the MP violates transmission security constraints, then additional constraints corresponding to the violations are imposed to the MP. Through this iterative process between the MP and SPs, we derive an optimal dispatch schedule incorporating the post-contingency corrective rescheduling. In addition, we consider interruptible loads as active control variables since the interruptible loads can participate as generators in competitive electricity markets. Numerical examples demonstrate the efficiency of the proposed algorithm.

• Journal of Electrical Engineering and Technology
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• 제12권3호
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• pp.1046-1052
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• 2017

The load on the power grid of South Korea is expected to grow continuously until the late 2020s, and it is necessary to increase the transfer capacity from the Eastern grid to the Seoul-Gyeonggi region by reinforcing the transmission network for the electric power system to remain stable. To this end, the grid reinforcement by two bipole LCC HVDC transmission systems have been considered on account of the public acceptability and high growth of the fault current level, even though an additional 765kV system construction is more economical. Since the probability of the existing 765kV double circuit transmission line trip is extremely low, a dynamic simulation study was carried out to estimate the efficient HVDC capacity able to stabilize the transient stability by utilizing the HVDC overload capability. This paper suggests the application plan to reduce the HVDC construction capacity with ensuring the transient stability during the 765kV line trip.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2098-2117
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• 2012

This paper jointly investigates the bandwidth allocation, transmission strategy and relay positions for two-way transmission aware cellular networks with network coding (NC). Our goal is to minimize the transmission power of mobile terminals (MTs). Consider a cellular system, where multiple MTs exchange information with their common base station, firstly, we propose an efficient bandwidth allocation method and then give a transmission strategy for each MT to determine whether to use relay stations (RSs) for its two-way transmission with the BS or not. To further improve the system performance, the optimal positions of RSs are also jointly discussed. A GA-based algorithm is presented to obtain the optimum positions for RSs. Besides, the impacts of frequency reuse on MT's transmission power and system spectral efficiency (SE) under different number of relays are also discussed in our work. Numerical results show that the proposed NC aware scheme can extend MTs' battery life at least 6% more than traditional method.

• Journal of Electrical Engineering and Technology
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• 제11권1호
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• pp.192-199
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• 2016

With changes in insulated defects, the environment, and so on, new partial discharge (PD) data are highly different from the original samples. It leads to a decrease in on-line recognition rate. The UHF signal and pulse current signal of four kinds of typical artificial defect models in gas insulated switchgear (GIS) are obtained simultaneously by experiment. The relationship map of ultra-high frequency (UHF) cumulative energy and its corresponding apparent discharge of four kinds of typical artificial defect models are plotted. UHF cumulative energy and its corresponding apparent discharge are used as inputs. The support vector machine (SVM) incremental method is constructed. Examples show that the PD SVM incremental method based on simulated annealing (SA) effectively speeds up the data update rate and improves the adaptability of the classifier compared with the original method, in that the total sample is constituted by the old and new data. The PD SVM incremental method is a better pattern recognition technology for PD on-line monitoring.

• 방송공학회논문지
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• 제15권6호
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• pp.868-875
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• 2010

AT-DMB 는 지상파 DMB를 기반으로 하며, 기존의 지상파 DMB와 역호환성을 유지하면서 전송용량을 증대시키기 위해 개발이 되었다. AT-DMB 관련 전송방식 및 계층적비디오서비스 기술개발 및 표준 제정이 완료되었으며, 데이터 서비스를 포함한 응용서비스 기술들이 개발 중에 있다. 본 논문에서는 AT-DMB 시스템에서 성상비 변화에 따른 전송 신호들의 전력변화를 고찰하고 이를 감소시켜 전송 성능을 개선하기 위한 방법을 제시한다. 이 방법을 적용하여 AT-DMB의 B 모드 및 Q 모드 모두에서 계층 변조된 신호들의 전력을 균일하게 유지시킬 수 있음을 확인하였다.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.339-343
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• 2006

We observed the application possibility of inductive coupler for the underground high-voltage power line communication by means of analysis of signal transmission characteristics and magnetic properties on annealing temperatures for high-permeability Fe-base amorphous alloys. The best electromagnetic and transmission characteristics were shown in nano-crystalline precipitated alloy annealed at temperature $510^{\circ}C$. The transmission characteristics in the low-frequency band depend on permeability of magnetic core materials and its properties of high-frequency band can be improved by impedance matching. Using the high pass filter embedded in the coupler, other noise signal band except for communication signals could be cut off.

• 전기학회논문지
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• 제59권5호
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• pp.841-846
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• 2010

Reliability in electrical power system refers to normal operation for schedule time in some system that action consists. It means that if there is no contingency of electric power supply decrease or load curtailment, reliability of the system is high. In this paper, a method for evaluation of transmission capability is proposed considering reliability standards. Deterministic and probabilistic methods for evaluation of transmission capability has been studied. These researches considered uncertainty of system components or N-1 contingency only. However, the proposed method can inform customers and system operators more suitable transmission capability. Well-being method using state probabilities of system components proves to be a more effective method in this paper comparing with calculation of LOLE(Loss of Load Expectation). The length of calculation is shorter but it can give more practical information to the exact system operators. Well-being method is applied to IEEE-RTS 24bus system to evaluate reliability in case study. The result is compared with a existing way to evaluate reliability with LOLE and it shows that transmission capability connected with adjacent networks. This paper informs system operators and power suppliers of reliable information for operating power system.

• 한국통신학회논문지
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• 제27권6B호
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• pp.559-568
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• 2002

본 논문에서는 이산적인 전송률 집합을 가진 실제 시스템에서 구현 가능한 가변 전송률 제어 및 전력 제어를 결합하는 알고리즘에 대하여 연구하였다. 이와 같은 연구는 문헌 [1]에서 선택적 전력 제어 (SPC)라는 알고리즘으로 제시되었지만, 사용자의 최소 전송률 보장과 신호대 간섭비의 변화에 따라 전송률 변화가 빈번하게 발생한다는 문제점을 가지고 있다. 본 논문에서는 전송률 적응을 고려하여 기존의 선택적 전력 제어 방법의 문제점을 해결하기 위한 새로운 모델과 반복 연산 알고리즘을 제시하였다. 그리고 수치 해석 및 모의 실험을 통해 보다 안정되고 낮은 전송 전력으로 향상된 효율을 가짐을 증명하였다.

• KEPCO Journal on Electric Power and Energy
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• 제1권1호
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• pp.85-91
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• 2015

전력선 통신에서 사용되는 비접촉식 커플러의 신호 전달 특성을 향상시키기 위한 비접촉식 커플러의 구조와 자기장 결합에 대한 연구를 수행하였다. 비접촉식 커플러의 결합 구조를 분석하였고, Rogowski 코일을 이용한 커플러와 자성체 코어를 이용한 커플러를 제작하여 구조에 따른 신호 전달 특성을 분석하였다. 집중 정수 소자와 임피던스 트랜스포머를 이용한 임피던스 매칭법을 제안하여 협대역과 광대역에서 신호 전달 특성을 향상시켰고 전달 신호의 크기는 대역폭과 트레이드오프가 있음을 보였다. 본 연구는 추후 부하 변동에 따른 임피던스 매칭 연구에 도움을 줄 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권9호
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• pp.4390-4407
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• 2019

The paucity of pilot signals in Massive MIMO system is a vital issue. To accommodate substantial number of users, pilot signals are reused. This leads to interference, resulting in pilot contamination and degrades channel estimation at the Base Station (BS). Hence, mitigation of pilot contamination is exigency in Massive MIMO system. The proposed Time Shifted Pilot Signal Transmission with Pilot signal Hopping (TSPTPH), addresses the pilot contamination issue by transmitting pilot signals in non-overlapping time interval with hopping of pilot signals in each transmission slot. Hopping is carried by switching user to new a pilot signal in each transmission slot, resulting in random change of interfering users. This contributes to the change in channel coefficient, which leads to improved channel estimation at the BS and therefore enhances the efficiency of Massive MIMO system. In this system, Uplink Signal Power to Interference plus Noise Power Ratio (SINR) and data-rate are calculated for pilot signal reuse factor 1 and 3, by estimating the channel with Least Square estimation. The proposed system also reduces the uplink Signal power for data transmission of each User Equipment for normalized spectral efficiency with rising number of antennas at the BS and thus improves battery life.