• 전기학회논문지
• /
• 제65권7호
• /
• pp.1169-1175
• /
• 2016

As an Increased penetration level of renewable resources has caused concerns about primary frequency response, an increase in BESS(Battery Energy Storage System) capacity has been expected because of its fast response to the disturbances in the power system. This paper proposes the Integrated Control Strategy of multiple BESS for effectively providing the primary frequency control in the bulk power systems by coordinating the response, SOC and its recovery of BESS. The proposed strategy prevents multiple BESS from providing exceeding response and keeps the balance between SOC of multiple BESS. In addition, It would recover the SOC of BESS efficiently. The effectiveness of the proposed strategy is verified through various case studies employing Korean power system.

• 한국정보과학회논문지:시스템및이론
• /
• 제36권1호
• /
• pp.26-32
• /
• 2009

저장장치를 다단계로 구성하여 효율적으로 많은 사용자의 요청을 동시에 처리하는 다단계 저장장치의 활용은 점차 늘어나고 있다. 저장 장치가 다단계로 발전하여, 매우 많은 데이타를 효과적으로 처리할 수 있게 되었으나, 디스크에 접근하기 위한 단계가 늘어남으로써 성능이 저하되는 문제가 발생한다. 현재까지는 메모리와 프로세스에 비해 느린 디스크 접근 속도를 완충하기 위해 선반입 정책이 매우 효과적이었다. 그러나 기존의 선반입 기법은 대부분 다단계로 구성된 저장장치는 고려하지 않기 때문에 다단계 저장장치에서 기존의 선반입 기법을 사용할 경우 큰 성능향상을 기대 할 수 없다. 본 연구에서는 네트워크로 연결된 다단계 저장장치에서 상위 레벨의 선반입 기법에 의존하지 않는, 넓은 용도로 사용할 수 있는, Prefetching Strategy for Multi-level Storage system(PMS)라 칭하는 하위 레벨 선반입 기법을 제안하였다. 이는 시스템의 사용자, 어플리케이션 혹은 상위 시스템과 독립적으로 동작하기 때문에 단지 하위 시스템의 선반입 정책으로 적용함으로써 쉽게 높은 성능을 사용할 수 있다. 또한 PMS 정책의 성능을 측정하기 위해 본 연구에서는 실제 시스템을 정교하게 흉내 내는 시뮬레이터를 개발하여 널리 쓰이는 두가지 트레이스를 이용한 서로 다른 32가지의 실험을 하였고, 기존의 선반입 정책을 하위 레벨에 적용한 시스템에 비해 PMS 정책을 하위 레벨에 적용할 경우, 모든 경우에서 성능향상을 확인 할 수 있었고, 최대 35%, 평균 16.56%의 평균 응답시간이 좋아짐을 보였다.

• 전기학회논문지
• /
• 제63권11호
• /
• pp.1615-1621
• /
• 2014

A wireless tram which runs without catenary and instead uses batteries installed in the tram has been recently researched actively. This paper presents a new method maximizing absorption of regenerative energy of a wireless tram and extending life cycle of the energy storage device in the wireless tram by applying line-optimized charging and discharging scenario. Energy efficiency and life cycle of energy storage system (ESS) are highly dependent on the characteristic of operating conditions. For example, frequent charge and discharge with high power cause the problems that decrease the battery life cycles. Hybrid energy storage system (HESS) is combination of two ESSs which have complementary characteristics to each other. HESS can provide even better functionality and performance than the battery only ESS due to the synergy effect of two ESSs. This paper also provides a power distribution strategy and driving scenarios which increase the life cycle and energy efficiency of the HESS consisting of a battery and an ultra-capacitor. The developed strategy was tested and verified by a hardware-in-the-loop-simulation (HILS) system which emulates the a wireless tram.

• 한국멀티미디어학회논문지
• /
• 제4권6호
• /
• pp.543-553
• /
• 2001

본 논문에서는 기존 의료 영상 이동 방법에서 생기는 문제점을 해결하기 위해서 의료 영상 데이터의 관리기법을 제안하였다. 의료영상 데이터의 관리기법으로써 EAT(Expanded Average Transaction time) 데이터 이동 기법과 시간 연관성 기반 데이터 저장 방법을 제안하였다. EAT데이터 이동 기법에서는 각 저장 영역에 저장되는 개체 버전을 구분하는 경계값과 각 영역에 저장되는 개체 버전을 정의하였다 시간 연관성에 기반한 데이터 저장 방법에서는 임의 두 개체 버전에 대한 겹침의 정도와 간격의 정도를 정의하였고, 두 값을 통합하여 개체 버전을 저장 장치에 배치하는 방법을 보였다. 시간 질의의 비율을 변화시키면서 클러스터의 참조 회수를 비교한 실험에서 기존의 방법보다 제안한 방법의 클러스터 참조 회수가 적게 나타났다.

• Journal of Electrical Engineering and Technology
• /
• 제9권3호
• /
• pp.1089-1095
• /
• 2014

Innumerable microgrids would be operated independently by individual operators in a future smart grid. This kind of decentralized power system requires entirely different operation scheme in the actual power system and electricity market operation. Especially, frequency regulation is very important for successive energy trade in this multi-microgrid circumstance. This paper presents an optimal energy and reserve market participation strategy and operation strategy of energy storage system (ESS) by a microgrid operator (MGO). For definite evaluation of the proposed strategy, we postulate that the MGO should participate in the Power Exchange for Frequency Control (PXFC) market, which was devised by Maria Ilic and her coworkers and is suitable to the decentralized operation circumstances. In particular, optimal reserve capacity of the frequency control market and optimal market participation ratio of ESS between frequency control market and energy market are derived theoretically and evaluated by simulations utilizing Nordic Pool Elspot price data.

• Journal of Electrical Engineering and Technology
• /
• 제12권2호
• /
• pp.549-558
• /
• 2017

DC distribution has several differences compared to AC distribution. DC distribution has a higher efficiency than AC distribution when distributing electricity at the same voltage level. Accordingly, power can be transferred further with low-voltage DC. In addition, power flow in a DC grid system is produced by only a voltage difference in magnitude. Owing to these differences, operation of a DC grid system significantly differs from that of an AC system. In this paper, the power flow problem in a bipolar-type DC grid with unbalanced load conditions is organized and solved. Control strategy of energy storage system on a slow time scale with power references obtained by solving an optimization problem regarding the DC grid is then proposed. The proposed strategy is verified with computer simulations.

• 한국에너지공학회:학술대회논문집
• /
• 한국에너지공학회 2000년도 춘계 학술발표회 논문집
• /
• pp.69-74
• /
• 2000

This paper describes an operation strategy of ice storage systems for energy saving during building cooling. In this study, chiller is assumed not having function of part load control. Thus, it is needed to adopt on-off control with the objective function of summed energy consumption for minimum energy consumption. A conventional control strategy compared with the chiller-on-off control is chiller-priority control. in this control chiller operates as its full capacity and ice storage meets the rest of the cooling load.

• 정보저장시스템학회논문집
• /
• 제1권1호
• /
• pp.34-41
• /
• 2005

We report some recent results in the rewritable Blu-ray Disc with enhanced overwrite cyclability by using the growth dominant eutectic based Ge(Sb70Te30)+Sb recording layer, GeN interface layer and write strategy optimization. We have developed phase-change optical media with appropriate write strategy for 36(i.e., 1X)-72Mbps(i.e., 2X) dual speed Blu-ray Disc system and fur the future high speed optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so called Time-Shifted Multipulse (TSMP) write strategy where starting position of multipulse parts are shined from reference clock. With this write strategy, the jitter characteristics of the disc was improved and we found that leading edge jitter was improved much more than trailing edge jitter in 1X-2X speed recording. Finally, we investigated the higher speed feasibility of 144Mbps(i.e., 4X) by adopting some elemental doping to the eutectic based Ag-In-Sb-Te recording layer and structural optimization of constitution layers in Blu-ray Disc. In the paper, we report the effect of Sn addition for the feasibility of higher speed recording. The addition of Sn shows increases of the crystallization speed of phase change recording layer.

• Journal of Power Electronics
• /
• 제19권1호
• /
• pp.316-331
• /
• 2019

A practical application of a supercapacitor energy storage system in a polarization instrument is proposed on the basis of the energy storage requirements of an induced polarization (IP) transmitter for geophysical exploration. We focused on the energy storage system of a supercapacitor, the topology of the power converter, and the system control strategy as key technologies, and we performed theoretical research and experimental tests on the system and developed an experimental platform. The experiments validated the theoretical research on the key technologies of the supercapacitor energy storage system and demonstrated the effectiveness of the innovation. Results showed that the storage system is efficient and satisfies the energy storage needs of the IP transmitter.

• 한국데이타베이스학회:학술대회논문집
• /
• 한국데이타베이스학회 1998년도 국제 컨퍼런스: 국가경쟁력 향상을 위한 디지틀도서관 구축방안
• /
• pp.3-48
• /
• 1998

Drivers for Increased Need for Digital Content ■ Falling cost of computing -Multimedia capability at reasonable cost ■ Decrease in digital storage cost -Magnetic, optical and tape -Cost of digital storage decreases 40％ / year ■ World Wide Web users explosion and falling cost of communications -17M web servers(1/97) -Number of users doubles every 6 months - Network bandwidth triples every year(omitted)