• Journal of KIISE
• /
• v.42 no.5
• /
• pp.566-572
• /
• 2015

We proposed a novel energy optimization technique for smartphone GPUs, more aggressively lowering the GPU frequency while obtaining higher energy efficiency with a negligible negative impact on the GPU performance. In order to achieve the Quality of Service (QoS) specified by the smartphone application, the proposed optimization technique employed the minimal acceptable GPU frequency based on average Frames per Second (FPS) for each GPU frequency level. Our experimental results on a smartphone development board showed that the proposed technique can reduce the GPU energy consumption by up to 23% over the default DVFS algorithm with only a 0.45 frame drop.

• KIPS Transactions on Computer and Communication Systems
• /
• v.3 no.9
• /
• pp.279-292
• /
• 2014

Energy aware server cluster aims to reduce power consumption at maximum while keeping QoS(quality of service) as much as energy non-aware server cluster. In the existing methods of energy aware server cluster, they calculate the minimum number of active servers needed to handle current user requests and control server power mode in a fixed time interval to make only the needed servers ON. When loads change rapidly, QoS of the existing methods become degraded because they cannot increase the number of active servers so quickly. To solve this QoS problem, we classify load change situations into five types of rapid growth, growth, normal, decline, and rapid decline, and apply five different thresholds respectively in calculating the number of active servers. Also, we use a flexible scheme to adjust the above classification criterion for multi threshold, considering not only load change but also the remaining capacity of servers to handle user requests. We performed experiments with a cluster of 15 servers. A special benchmarking tool called SPECweb was used to generate load patterns with rapid change. Experimental results showed that QoS of the proposed method is improved up to the level of energy non-aware server cluster and power consumption is reduced up to about 50 percent, depending on the load pattern.

• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.433-434
• /
• 2016

전력계통은 안정된 전압과 주파수의 전력수급이 요구되는 가운데 발전기의 안정성은 주요 요소이다. 그런데 수차발전기 운전 중 부하 탈락 시 급격한 주파수 상승에 의한 발전기 과전압발생은 발전기 여자시스템의 제어신호인 전압실효값 오차에 기인한 것이다. 이런 오차를 최소화하고 발전기 전압을 안정시키기 위해 ZCP(Zero Crossing Point)와 FPGA를 이용한 주파수 검출영역 확장과 DFT(Discrete Fourier Transform) 알고리즘을 이용하여 안정된 전압실효값을 계산하는 기법을 설계하였다. 실험결과, 기존 57~63Hz 주파수 영역의 DFT 대비 확장된 30~90Hz 대역의 전압실효값 오차는 최대 24.68%에서 0.22%로 대폭 개선되었다.

• Proceedings of the KIPE Conference
• /
• 2019.11a
• /
• pp.218-219
• /
• 2019

본 논문은 모드 유지 알고리즘이 적용된 직류 배전용 에너지 저장 장치(Energy Storage System, ESS)의 모듈형 운전 제어 기법에 관해 제안한다. 모드 유지 알고리즘은 설정된 방전 깊이(Depth of Discharge, DoD) 내에서 계통의 전력 수요 및 공급의 변화가 생긴 경우에 수시로 변화하는 충/방전 모드의 변경을 제한하는 알고리즘이다. 이를 통해 ESS의 가용 용량을 최대한 사용 가능하며, 계통의 전력 공급 및 부하 수요에 따라 계통의 동작 상태를 결정할 때 도움을 줄 수 있다. 제안한 알고리즘은 PSIM 시뮬레이션을 통해 검증하였다.

• Journal of IKEEE
• /
• v.22 no.3
• /
• pp.613-618
• /
• 2018

In this paper, an active snubber type flyback converter was applied to a 60W class adapter and its test results are reported by producing a prototype. Especially, the prototype of the adapter was designed for both input voltage of 110V and 220V. The output voltage was designed for 60W with 19V class which is the most commonly used in laptops. The prototype was designed to a volume of about $50cm^3$ and a power density of about $1.22W/cm^3$ to minimize the size and verify portability. The maximum efficiency of the prototype was 90.88% at its maximum load of 60W against input voltage change and 91.04% was observed at 60W under input voltage of 220V. Furthermore, the stability of the output voltage against load power was observed to be within about 0.07%.

• Proceedings of the KIEE Conference
• /
• 2015.07a
• /
• pp.635-636
• /
• 2015

한전에서는 전력계통과 연계한 대용량 배터리 에너지저장장치(Energy Storage System)에 전력을 저장하였다가 전력계통의 최대 부하 보상, 주파수 조정, 신재생에너지 출력 평준화 등에 이용하고 있다. 배터리를 이용한 에너지저장장치의 실용성을 확인하기 위하여 한국전력공사 전력연구원 ESS연구사업단에서는 제주시 조천변전소에 4MW급 실증단지를 건설하여 시험을 진행하여 왔다. 최근에는 52MW 배터리 에너지저장장치를 전력계통의 주파수 조정용으로 사업화하고 있으며, 이와 관련된 연구도 진행하고 있다. 한국전력공사 전력연구원에서는 서안성, 신용인 변전소에 건설을 완료하여 시운전 중인 52MW 배터리 에너지저장장치 사업에 관련된 기술개발을 위하여 전력연구원에 24MW용 제어시스템, 조천변전소에 28MW용 제어시스템을 개발하여 관련기술을 서안성, 신용인 변전소 에너지저장장치에 적용하여 자동제어 시운전을 수행하였다. 본 논문에서는 주파수조정용 52MW 배터리 에너지저장장치의 시운전 내용을 소개하고자 한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.23 no.12
• /
• pp.217-223
• /
• 2009

This paper shows a reasonable contract power conversion factor, that was made by the systematic and statistical way considering actual conditions, such as investigated contract power and peak power for the last 5 years of each customer for 461 general customers as to AMR. In this dissertation, it is necessary to analyze the key features and general trend from the investigated data. It made an analysis of the feature parameters, such as average, standard deviation, median, maximum, minimun and thus it was carried by the linear and nonlinear regression analysis. Therefore, this paper compared characteristics for a contract power conversion factor which is applied to estimate contract power with characteristics for a regression model for customers(office, store, hotel, hospital, wedding hall) which maximum utilization factor of transformer is more than 60[%].

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.14 no.1
• /
• pp.102-108
• /
• 2000

This paper presents a result of practical study about the adjustment of load correlation equation for the load management of pole transformer. For adjusting the load correlation equation, we analyze the correlative relation between working electric energy[kWh] and peak load[A]. To enhance the accuracy of correlation equation, we classify the 12 representative area patterns. And then, we select the 24 sample pole transformer for each area pattern. For the reliability of the data using the load correlation equation, load management equipment is utilized for each sample pole transformer. Through the on-line data acquisition, we construct the database. For adjusting the load correlation equation, we consider the two points. One is the goodness of fitness for load correlation equation and the other is prevention of pole transformer damage due to the overload. Finally, we propose the correlation equation using the linear and quadratic equation all at once. Through the case studies, we verify that the proposed load correlation equation is reduced the error ratio than conventional correlation equation.

• Journal of the Korea Society of Computer and Information
• /
• v.19 no.4
• /
• pp.25-33
• /
• 2014

This paper proposes a power-efficient scheduling scheme that stochastically minimizes the power consumption of real-time tasks while meeting their deadlines on multicore processors. In the proposed scheme, uncertain computation amounts of given tasks are translated into probabilistic computation amounts based on their past completion amounts, and the mean power consumption of the translated probabilistic computation amounts is minimized with a finite set of discrete clock frequencies. Also, when system load is low, the proposed scheme activates a part of all available cores with unused cores powered off, considering the leakage power consumption of cores. Evaluation shows that the scheme saves up to 69% power consumption of the previous method.

• Proceedings of the KIPE Conference
• /
• 2010.07a
• /
• pp.85-86
• /
• 2010

최근 신.재생 에너지를 이용하는 분산전원 시스템의 증가로 인하여 직류발전량이 증가하고 있다. 직류 배전 시스템은 전력변환 시 교류 배전 시스템 보다 에너지 변환 효율이 높은 장점을 갖는다. 본 논문에서는 직류 배전 계통을 갖는 빌딩에서 보조전원인 배터리의 개선된 운용 기법을 통하여 설비 용량을 줄일 수 있는 개선된 보조전원 운용기법을 제안하였다. 시뮬레이션을 통하여 최대 부하시 보조전원의 에너지를 계통에 보상함으로써 수전설비의 용량을 낮출 수 있음을 검증 하였다.