• Title/Summary/Keyword: Power-feeding

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Reliability Modeling of Direct Current Power Feeding Systems for Green Data Center

  • Choi, Jung Yul
    • Journal of Electrical Engineering and Technology
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    • v.8 no.4
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    • pp.704-711
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    • 2013
  • Data center is an information hub and resource for information-centric society. Since data center houses hundreds to ten thousands servers, networking and communication equipment, and supporting systems energy saving is one of the hottest issues for green data center. Among several solutions for green data center this paper introduces higher voltage direct current (DC) power feeding system. Contrary to legacy alternating current (AC) power feeding system equipped with Uninterruptible Power Supply (UPS), higher voltage DC power feeding system is reported to be a more energy efficient and reliable solution for green data center thanks to less AC/DC and DC/AC conversions. Main focus of this paper is on reliability issue for reliable and continuous operation of higher voltage DC power feeding system. We present different types of configuration of the power feeding systems according to the level of reliability. We analyze the reliability of the power feeding systems based on M/M/1/N+1/N+1 queueing model. Operation of the power feeding system in case of failure is also presented.

A Study on the Loop Current Induced by Voltage Phase Difference Substations during Parallel Feeding under the Alternating Current AT Electric Power Feeding Method (교류 AT급전방식에서 병렬급전시 변전소간 전압위상차에 의한 루프전류에 관한 연구)

  • Park, Jae-Seok;Song, Joong-Ho
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.1997-2004
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    • 2011
  • The $2{\times}25kv$ AT electric power feeding method in the A.C. electric train adopts the one-phase power feeding method as the standard due to a voltage phase difference, and the distance between the two neighboring substations is 50km due to voltage drop. The one-phase power feeding method makes the system operation feasible, while making it unfavorable for power supply. Moreover, railroad involves large-capacity single-phase load, and if it is expected to continue to rise, it is necessary to research on measures to stabilize the supply of power to railroad cars with the existing facilities. In this study, a parallel power feeding method between neighboring substations is proposed to stabilize the supply of electric power to electric railroad cars under the 2*25kv AT power feeding method and the loop current induced by voltage phase difference between the two neighboring substations during parallel power feeding is investigated.

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A Power Losses Analysis of AC Railway Power Feeding Network using Adaptive Voltage Control (능동형 전압제어를 통한 교류 전기철도 급전망에 대한 전력손실 분석)

  • Jung, Hosung;Kim, Hyungchul;Shin, Seongkuen;Kim, Jinho;Yoon, Kiyong;Cho, Yonghyeun
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.11
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    • pp.1621-1627
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    • 2013
  • This paper compares power losses between voltage controlled before and after using power conversion device in AC feeding system. For this purpose we present voltage control procedures and criteria and model high speed line and train using PSCAD/EMTDC to compare power losses in various feeding condition. Power losses of the simulation result in power control before and after in single point feeding system was reduced maximum 0.37 MW(23.8 %) and average 0.23 MW(20.5 %) when one vehicle load operates maximum load condition. When three vehicles operate maximum load condition in one feeder section, power losses after voltage control was reduced 1.03 MW(49.5%) compared to before voltage control. And, power loss of parallel feeding system is reduced the average 0.08 MW(7.2 %) compared to the single feeding system. In conclusion, adaptive voltage control method using power conversion device can reduce power losses compared with existing method.

Inductive Disturbance Reduction Method for Electric Railway (전기철도해서의 유도장해 경감책에 관한 연구)

  • Lee, Kyo-Sung;Kim, Do-Hun;Lee, Yong-Jae;Kim, Yang-Mo
    • Proceedings of the KIEE Conference
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    • 2002.11d
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    • pp.369-371
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    • 2002
  • The railway power feeding system is divided into AC power feeding system and DC power feeding system. In downtown area. DC power feeding system is used and AC power feeding system is used in intercity railway system. AC power feeding system raises a inductive disturbance that is divided into electrostatic induction and electromagnetic induction. Especially, it has a bad effect on communication lines. So inductive disturbance reduction method has been adopted in many system. In this paper, we deals with the inductive disturbance reduction method of railway power feeding system and of sides affected by inductive disturbance.

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The comparison and investigation of power supply capability according to feeding schemes in AC electric railway system (교류전기철도시스템에서 급전계통 구성에 따른 급전성능 비교검토)

  • Lee, Chang-Mu;Oh, Kwang-Hae;Chang, Sang-Hun;Han, Mun-Seub
    • Proceedings of the KIEE Conference
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    • 2001.07b
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    • pp.1236-1238
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    • 2001
  • The electrified railway has various power supply schemes. Although the identical trains are operated in same condition and the impedance of track are equal, the genealogy impedance of track is changed according to composition method of feeding scheme. So, the collection voltage of train and supplying power from railway substation are greatly unlike. For simulation of collection voltage and power supply according to feeding scheme, using 6-port network analysis proposed previously simulate collection voltage and supply power according to feeding scheme(Parallel Post feeding system, normal feeding system and tie feeding system) and compare and investigate each characteristics.

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A Phase-shifter for Regulating Circulating Power Flow in a Parallel-feeding AC Traction Power System

  • Choi, Kyu-Hyoung
    • Journal of Electrical Engineering and Technology
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    • v.9 no.4
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    • pp.1137-1144
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    • 2014
  • A parallel-feeding AC traction power system increases the power supply capacity and decreases voltage fluctuations, but the circulating power flow caused by the phase difference between the traction substations prevents the system from being widely used. A circuit analysis shows that the circulating power flow increases almost linearly as the phase difference increases, which adds extra load to the system and results in increased power dissipation and load unbalance. In this paper, we suggest a phase shifter for the parallel-feeding AC traction power system. The phase shifter regulates the phase difference and the circulating power flow by injecting quadrature voltage which can be obtained directly from the Scott-connection transformer in the traction substation. A case study involving the phase shifter applied to the traction power system of a Korean high-speed rail system shows that a three-level phase shifter can prevent circulating power flow while the phase difference between substations increases up to 12 degrees, mitigate the load unbalance, and reduce power dissipation.

A Study on Verification of PowerRail based on Voltage Drop under Extended Feeding Condition (연장급전 전압강하 계산을 위한 전기철도 급전 시뮬레이터의 검증에 관한 연구)

  • Kim, Joorak
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.64 no.2
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    • pp.331-337
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    • 2015
  • The power flow analysis of electrified railway is required complicated calculation, because of variable load. Train runs trough rail supplied by electric power therefore, the load value in electrified railway system fluctuates along time. The power flow algorithm in electrified railway system is different from general power system, and the power flow simulation is peformed by the particular simulation software. Powerail is simulation software for analysis of traction power supply system developed by KRRI, in 2008. This consists of load forecasting module, including TPS and time scheduling, and power flow module. This software was verified by measured current under normal feeding condition, however, has not been verified by voltage on the condition of extended feeding. This paper presents the verification of PowerRail based on voltage drop under extended feeding condition. This is performed by comparing simulation result with field test. Field test and simulation is done in commercial railway line.

Modeling and Simulation Reactive Power Compensator using Multi-port Network Algorithm in Electrified Railway (다단자망 알고리즘을 이용한 급전시스템의 무효전력 보상 모델링 및 시뮬레이션)

  • Kim, Joorak
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.65 no.5
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    • pp.883-887
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    • 2016
  • The power supply system in Korean electrified railway has adopted AT feeding. If a fault occurs in some substation for any reason, the vicinity substation must feed electric power on the outage substation through catenary. So, the feeding distance grows twice of the normal state at extended feeding condition. If substation's feeding distance is longer than normal condition, the catenary impedance and train to supply electric power from the substation. Therefore, the severe voltage drop can occur and power supply shall be not allowed. This paper presents the model of compensator against voltage drop using multi-port network algorithm. Whole traction power supply system can be analyzed with this model. Computer simulation including this model is performed based on real train schedule and increased schedule in case studies.

Comparison of Some Antioxidative Activities of Feeding Honey from the Mixture of Extract of Rubus Coreanus Miquel and Sugar with Three Types of Honeys on the Market (복분자 추출액 급이 사양꿀과 일부 시판꿀의 항산화활성 비교)

  • Oh, Hae-Sook
    • The Korean Journal of Community Living Science
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    • v.21 no.4
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    • pp.641-649
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    • 2010
  • To make sure of the usefulness of extract of Rubus coreanus Miquel for producing functional feeding honey, we compared some antioxidative indicators of feeding honey using extract of Rubus coreanus Miquel with acacia honey, SueBee Clover honey(USA), feeding honey on the market. The water content of four honeys were 16.6~26.5%, pH were 3.18~3.70, and titratable acidity ranged 0.018~0.022%. The phenolic compound contents of SueBee Clover honey and feeding honey using extract of Rubus coreanus Miquel were 8.3 mg/100 g and 7.3 mg/100 g, respectively, and were significaltly higher thgheacacia honey and feeding honey on the market. The flavonoid contents per 100 g of honey ranged from 2.3 mg(acacia honey) to 15.0 mg(SueBee Clover honey). DPPH anion scavenging activity of four honeys were not high. 0.5~2.0 g/ml of feeding honey using extract of Rubus coreanus Miquel was 16~36% and showed a concentration-reliant figure. At the concentration of 0.25~0.75 mg/ml, the reducing power of four honeys increased concentration-dependently, and the power of 0.25 mg/ml of feeding honey using extract of Rubus coreanus Miquel was corresponding to thgt of $150{\mu}g$/ml of a vitamin C solution. ABTS radical scavenging activity of feeding honey using extract of Rubus coreanus Miquel was 43.3~68.4%; the highest activity amongst all samples. When plotting the dose-response curve, ABTS radical scavenging activity also increased as their concentration increased from 62.5 mg/ml to 500 mg/ml. The heat treatment reduced the phenolic compound contents of acacia honey and feeding honey using extract of Rubus coreanus DPPH anion scavenging activity of feeding honey on the market and feeding honey using extract of Rubus coreanus Miquel did not changed significaltly after heating for 20 min, and the three honey except SueBee Clover honey maintained the reducing power with the same treatment.

Analysis of Catenary impedance characteristics in the extended power feeding conditions of AC traction system (교류급전방식에서의 연장급전에 따른 선로임피던스 특성 분석)

  • Jung, Hosung;Kim, Joorak;Chang, Sanghoon
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.1617-1618
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    • 2015
  • This paper analyzed catenary impedance characteristics of relays installed in substation and sectioning post to protect power feeding circuit in the extended power feeding conditions. For this, we modelled AT feeding system using PSCAD/EMTDC and calculated catenary impedance. The relay installed in substation calculated catenary impedance of the extended power feeding area adding catenary impedance of self protection zone. But, the relay installed in sectioning post calculated catenary impedance of the only protection area. Therefore, we confirmed that the more reliable protection way can be utilized using the relay installed in sectioning post.

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