• Title/Summary/Keyword: Stable Operation

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The Development of Feed-Water Flow Controller of Boiler Feed-Water Pump in 500MW Class Coal-Fired Power Plant (500MW급 석탄화력발전소 보일러 급수펌프 유량 제어기 개발)

  • Lim, Geon-Pyo;Choi, In-Kyu;Park, Doo-Yong;Jeong, Tae-Won;Kim, Gun-Jung
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.9
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    • pp.1663-1672
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    • 2010
  • The boiler feed-water pump controllers which can be applied to 500MW class coal fired power plants was developed. The validity of the developed controllers was shown via the applied test result in a power plant. It is expected that the developed controllers are used to retrofit the existing controllers that have surpassed their expected service life and have limited spare parts, and contributes to the stable operation of plants. Based on the collected data and analysis, new control schemes were developed and implemented during the overhaul period in the new control systems. During normal operation, feed water could be supplied to the boiler with the capability of the 1600t/h flow without any problems in automatic mode of controllers. In this study, the feed-water pump controllers were developed successfully. In addition, it is expected that the developed controllers can make the plant operation more stable and can be applied to a lot of power plants.

SSR (Simple Sector Remapper) the fault tolerant FTL algorithm for NAND flash memory

  • Lee, Gui-Young;Kim, Bumsoo;Kim, Shin-han;Byungsoo Jung
    • Proceedings of the IEEK Conference
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    • 2002.07b
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    • pp.932-935
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    • 2002
  • In this paper, we introduce new FTL(Flash Translation Layer) driver algorithm that tolerate the power off errors. FTL driver is the software that provide the block device interface to the upper layer software such as file systems or application programs that using the flash memory as a block device interfaced storage. Usually, the flash memory is used as the storage devices of the mobile system due to its low power consumption and small form factor. In mobile system, the state of the power supplement is not stable, because it using the small sized battery that has limited capacity. So, a sudden power off failure can be occurred when we read or write the data on the flash memory. During the write operation, power off failure may introduce the incomplete write operation. Incomplete write operation denotes the inconsistency of the data in flash memory. To provide the stable storage facility with flash memory in mobile system, FTL should provide the fault tolerance against the power off failure. SSR (Simple Sector Remapper) is a fault tolerant FTL driver that provides block device interface and also provides tolerance against power off errors.

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Design of a control scheme for applying DC power sources to a distribution system (배전시스템에 DC 전력원을 적용하기 위한 제어 기법 설계)

  • Hwang, Chul-Sang;Kim, Gyeong-Hun;Byeon, Gilsung;Jeon, Jin-Hong;Jo, Chang-Hee;Park, Minwon;Yu, In-Keun
    • Proceedings of the KIEE Conference
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    • 2015.07a
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    • pp.1056-1057
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    • 2015
  • A common DC bus is a useful connection for several DC output sources such as photovoltaic (PV), fuel cells, and batteries. Operation of the common DC power system with more than two DC output sources, especially in a stand-alone mode, requires a control scheme for the stable operation of the system. In this paper, a control scheme has been developed for applying DC power sources to the distribution system. The purpose of the control scheme is to make the best use of the DC power sources. The DC power system consists of PV, two energy storage systems and a DC-AC inverter with the control scheme. A distribution system was modeled in PSCAD/EMTDC. As the results, the control scheme is applied to the DC-AC inverter and the DC-DC converter for transfer operations between the grid-connected and the stand-alone mode to keep the DC bus and the AC voltage constant. The results from the simulation demonstrate the stable operation of a grid connected DC power system.

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Turbidity Treatment of TiO2 Wastewater by Electrocoagulation/flotation Process (전기응집/부상 공정을 이용한 TiO2 폐수의 탁도 제거)

  • Park, Young-Seek
    • Journal of Environmental Science International
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    • v.19 no.1
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    • pp.89-96
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    • 2010
  • The separation of $TiO_2$ wastewater carried out by an electrocoagulation/flotation process, which had various operating parameters. The effect of electrode material (aluminum and four dimensionally stable electrode), applied current (0.07~0.5 A), electrolyte concentration (0~1 g/L), solution pH (3~11), initial turbidity (1000~20000 NTU) and suspended solid concentration (5000~25000 mg/L) were evaluated. Turbidity removal efficiency of the soluble anode (aluminum), which could produce metal ions, was higher than that of the dimensionally stable electrode. Considering operation time, turbidity removal and electric power, optimum current was 0.19 A. The more NaCl dosage was high, the less electric power was required. However, optimum NaCl concentration was 0.125 g/L considered removal efficiency, operation time and cost. Initial $TiO_2$ concentration did not affected turbidity removal on the electrocoagulation/flotation operation. The electrocoagulation/flotation process was proved to be a very effective separation method in the removal of $TiO_2$ from wastewater.

Controller Design of a Novel Power Conditioning System with an Energy Storage Device for Renewable Energy Sources under Grid-Connected Operation

  • Park, Sun-Jae;Lee, Hwa-Seok;Kim, Chan-In;Park, Joung-Hu;Jeon, Hee-Jong;Ryeom, Jeongduk
    • Journal of Power Electronics
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    • v.13 no.3
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    • pp.390-399
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    • 2013
  • As a result of the depletion of fossil fuels and environmental contamination, it has become important to use renewable energy. For the stable utilization of renewable energy sources, energy storage devices must be used. In addition, renewable and distributed power sources with energy storage devices must operate stably under grid-connected mode. This paper proposed dynamic response modeling for renewable power generation systems including a charger/discharger with an energy storage device in order to derive a method to guarantee stable operation while fully utilizing the energy from the energy storage device. In this paper, the principle operation and design guidelines of the proposed scheme are presented, along with a performance analysis and simulation results using MATLAB and PSIM. Finally, a hardware prototype of a 1kW power conditioning system with an energy storage device has been implemented for experimental verification of the proposed converter system.

A Study on Self-Excited characteristic for stable operation of Three-Phase Induction Generator (3상유도발전기의 안정된 동작을 위한 자기여자현상에 대한 연구)

  • Cho, Y.R.;Maeng, I.J.;Baek, S.H.;Lee, K.Y.;Kim, C.J.
    • Proceedings of the KIEE Conference
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    • 2005.10c
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    • pp.26-28
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    • 2005
  • Induction generator is the most common generator in wind energy systems because of its simplicity, ruggedness, little maintenance, price and etc. But the main drawbacks in induction generator is its need of reactive power means to build up the terminal voltage. This drawback is not an obstacle today where PWM inverters can accurately supplies the induction generator with its need from reactive power. For a insurance of three-phase induction generator requires capacitive reactance of the terminal. Most of previous work uses numerical iterative method to determine this minimum capacitor. But the numerical iteration takes long time and divergence may be occurs. In this paper is presented the design methods of the minimum self-excited capacitor required for induction generator operation. And a new formula from the equivalent circuit for stable generation operation of self-excited induction generator calculates the proper capacity to obtain the terminal voltage of the load stage. The validity of proposed design methods is confirmed by experimental and computed results.

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Initial Operation and Preliminary Results of the Instrument for the Study of Stable/Storm-Time Space (ISSS) on Board the Next Generation Small Satellite-1 (NEXTSat-1)

  • Kim, Eojin;Yoo, Ji-Hyeon;Kim, Hee-Eun;Seo, Hoonkyu;Ryu, Kwangsun;Sohn, Jongdae;Lee, Junchan;Seon, Jongho;Lee, Ensang;Lee, Dae-Young;Min, Kyoungwook;Kang, Kyung-In;Lee, Sang-Yun;Kang, Juneseok
    • Journal of Astronomy and Space Sciences
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    • v.37 no.3
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    • pp.209-218
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    • 2020
  • This paper describes the initial operations and preliminary results of the Instrument for the study of Stable/Storm-time Space (ISSS) onboard the microsatellite Next Generation Small Satellite-1 (NEXTSat-1), which was launched on December 4, 2018 into a sun-synchronous orbit at an altitude of 575 km with an orbital inclination angle of 97.7°. The spacecraft and the instruments have been working normally, and the results from the observations are in agreement with those from other satellites. Nevertheless, improvement in both the spacecraft/instrument operation and the analysis is suggested to produce more fruitful scientific results from the satellite operations. It is expected that the ISSS observations will become the main mission of the NEXTSat-1 at the end of 2020, when the technological experiments and astronomical observations terminate after two years of operation.

An Empirical Study on Machine Learning based Smart Device Lithium-Ion Cells Capacity Estimation (머신러닝 기반 스마트 단말기 Lithium-Ion Cell의 잔량 추정 방법의 실증적 연구)

  • Jang, SungJin
    • The Journal of the Convergence on Culture Technology
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    • v.6 no.4
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    • pp.797-802
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    • 2020
  • Over the past few years, smart devices, including smartphones, have been continuously required by users based on portability. The performance is improving. Ubiquitous computing environment and sensor network are also improved. Due to various network connection technologies, mobile terminals are widely used. Smart terminals need technology to make energy monitoring more detailed for more stable operation during use. The smart terminal which is light in small size generates the power shortage problem due to the various multimedia task among the terminal operation. Various estimation hardwares have been developed to prevent such situation in advance and to operate stable terminals. However, the method and performance of estimating the remaining amount are not relatively good. In this paper, we propose a method for estimating the remaining amount of smart terminals. The Capacity Estimation of lithium ion cells for stable operation was estimated based on machine learning. Learning the characteristics of lithium ion cells in use, not the existing hardware estimation method, through a map learning algorithm using machine learning technique The optimized results are estimated and applied.

Optimal Path Planning of a Tractor-implement for Precision Farming (정밀농업을 위한 트랙터-작업기의 최적 경로계획)

  • 정선옥;박우풍;장영창;여운영
    • Journal of Biosystems Engineering
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    • v.24 no.4
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    • pp.301-308
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    • 1999
  • Path planning for field operation of agricultural machinery is an indispensible part for precision farming or autonomous field operation. In this study, two algorithms (I, II) of generating a time-based shortest operation path were suggested to plan an optimal operation of an agricultural tractor-implement in a rectangular shaped field. The algorithms were based on modification of a minimum spanning tree algorithm, and applied for tractor-implement operations. the generated path was consisted of round operation and returning operation sections. The number of round operation was determined from the condition that a tractor can turn smoothly at headlands. The performance of the algorithms was evaluated by the calculation number for path generation and the total path length generated. Their stability was affected by the number of returning operation, but the algorithm II was considered to be more stable. In addition, the performances of the developed algorithms were compared with those of the conventional field operations at selected field sizes and shapes. The results showed that the algorithms could reduce field operation time greatly. For a 100m$\times$40m field, the reduced path length was 78m. The study also included an user interface program for implementing the algorithms and generating GPS coordinates that could be used in GIS softwares for precision farming.

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Characteristics of 5 kW Class Proton-Exchange-Membrane Fuel Cell(PEMFC) Stack according to the Long-Term Operation (장기운전에 따른 5 kW급 고분자 전해질 연료전지 스택의 특성)

  • Kim, Jae-Dong;Lee, Jung-Woon;Park, Dal-Ryung
    • Journal of the Korean Institute of Gas
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    • v.11 no.3
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    • pp.40-43
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    • 2007
  • The performance of PEMFC stack can be improved significantly by optimizing the design and operating conditions. As a result, the performance of daily operation showed slight deviation (0.02-0.9%) after accumulated DSS operation for 500 hrs but the stack performance was stable. Therefore, it is confirmed that it would be improved the life-time of stack and operation reliability for the commercialization of PEMFC system.

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