• Title/Summary/Keyword: Steady-state operation

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State Estimation Method and MMI Format of KEPCO EMS (한전(韓電)EMS의 상태추정기법(狀態推定技法)과 MMI 형식(形式))

  • Lee, Kyung-Jae;Yu, Sung-Chul;Kim, Yeong-Han;Lee, Hyo-Sang
    • Proceedings of the KIEE Conference
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    • 1988.07a
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    • pp.866-869
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    • 1988
  • In the operation of a power system, the security of the system has acquired significant importance to supply electric power of better quality. The State Estimator, a part of security functions, provides a complete real time solution estimate of the steady-state conditions of the power system for use by the Real Time Network Analysis functions. This paper briefly introduces the Fast Decoupled Weighted Least Square State Estimator which is adopted in the KEPCO EMS with features of Man-Machine Interface.

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A study on the rotating machine characteristics drived by chopper (초퍼 회로를 사용한 회전기계의 특성해석에 관한 연구)

  • 이승원
    • 전기의세계
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    • v.29 no.6
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    • pp.393-400
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    • 1980
  • It is shown in this paper that it is possible to derive generalized state equations for computation of electrical circults constanining SCR and diode elements. Revankar's binary logic variable method is used for formulation of the state equation of chopper circuit. Advantage of this method is that the state equations can be set up without the exact knowledge of the circuit operaton. The different modes of operation of the circuit are identified by the computer itself. By applying this method, the steady state performances of separately excited chopper-fed dc motor considering the counter electromotive force of the motor are investigated and the results of the computer simulation are presented. There is a satisfactory agreement between the theoretical and experimental results.

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Analysis and Measurement of the Magnetic Fields Cause by Operation of Electromotive Installations (전동력설비의 운전에 의해 발생되는 자계의 측정과 해석)

  • 이복희;길경석
    • The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.9 no.2
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    • pp.58-67
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    • 1995
  • The paper describes the variation of magnetic fields caused by the operation of induction motors. The measuring system consists of the self-integrating magnetic field sensor, amplifier, and active integrator. From the calibration experiments, the frequency bandwidth of the magnetic field measuring system ranges from 20[Hz] to 300[kHz] and sensitivity is 0.234(mV/$\mu\textrm{T}$]. The magnetic fields generated under steady state and starting operations of duction motor are recorded by the proposed measuring system, and the fast Fourier transformation(FFT) of the measured data is performed to analyze the harmonic components. A single pulsed magnetic field is strongly caused by direct starting the induction motor, and its peak value is greater than 5 times as compared with the steady state value. The long transient duration and high intensity originates from the large inductance and dynamic characteristic of the induction motor, During the steady state operation of induction motor, subharmonics of magnetic field components, which depend on the pole number of induction motor, are observed. The lower order power-line harmonics can be inferred from the voltage flicker and current ripple which are derived from the torque fluctuation of induction motor. In the case of the induction motor drived by inverter, the harmonics of magnetic field are much more than those caused by direct starting method and are found generally to increase with decreasing the driving frequency.

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A Study on the Performance Enhancement of Blind Equalizer for CATV Receiver Using the Variable Step Size Algorithm (가변 스텝 크기 알고리즘을 이용한 CATV 수신기용 블라인드 등화기의 성능 향상에 관한 연구)

  • Lee, Hyeon-Cheol;Jo, Il-Jun;Jin, Hyeon-Su;Kim, Seong-Hwan
    • The Journal of the Acoustical Society of Korea
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    • v.15 no.6
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    • pp.33-40
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    • 1996
  • In this paper, we resolved a trade-off problem of the blind equalizer based on the stop-and-go algorithm that is commonly used for QAM demodulation in CATV receiver. The stop-and-go algorithm has used the LMS(least mean square) algorithm in the updating operation of tap weights so that the structure of equalizer is simple, but there is a trade-off between convergence speed and steady state error as in the typical LMS algorithm. We used the variable step size algrithm to improve the convergence speed with the steady state error in the constant level. With respect to the same level of the steady state error, the variable step size stop-and-go algortihm improved convergence speed by about $36%{\sim}56%$ as compared with that of the constant step size algortihm.

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Studies on the Steady State and Dynamic Characteristics of a Carbon Dioxide Air-Conditioning System for Vehicles (자동차용 이산화탄소 냉방 시스템의 정상상태 및 동적 특성에 관한 연구)

  • Park, Min-Su;Kim, Sung-Chul;Kim, Dal-Won;Kim, Min-Soo
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.31 no.6 s.261
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    • pp.531-538
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    • 2007
  • In this study, an air conditioning system using carbon dioxide as a refrigerant was developed for automotive cabin cooling. Experiments have been carried out to examine the steady state and dynamic characteristics of this system. The system consists of a compressor, a gas cooler, an evaporator, an expansion device, an internal heat exchanger and an accumulator. The compressor is a variable displacement type, driven by the electric motor, and the gas cooler and the evaporator are aluminum extruded heat exchangers of micro channel type. The $CO_2-refrigerant$ charge, the compressor speed, the air inlet temperature of the gas cooler, the air inlet temperature and the air flow rate of the evaporator and the cooling load are varied and the performance of the system is experimentally investigated. As the compressor speed increased, cooling capacity increased, but the coefficient of performance was deteriorated. As the cabin air temperature or the air flow rate to the cabin was set high, both the cooling capacity and the COP increased. In the cool down experiment with 1.0 or 2.0 kW of heat load, the dynamic characteristics of the air-conditioning system were investigated. For a given capacity of compressor, cool down speed was monitored, and the temperature change was acceptable fur low heat load condition.

Statistical Analysis on Residuals from No-Fault Reference Models of a Residential Heat Pump System in Normal Cooling Operation (가정용 열펌프 시스템의 정상냉방 운전조건에서 기준모델에 의한 잔차의 통계적 분석)

  • Kim, Min-Sung;Yoon, Seok-Ho;Baik, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.12
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    • pp.1351-1358
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    • 2011
  • To approximate the threshold of the fault detection and diagnosis (FDD) system, validation of the measurements is mandatory. Naturally, the system shows uncertainties due to measuring sensors - mostly thermocouples or RTDs - and due to repeatability. The uncertainty of a thermocouple comes from natural variation or a drift of the thermocouple measurement. Considering the natural variation behaves like zero-mean white noise, its natural variation can be characterized closely by the steady-state standard deviation. However, residuals between measurements and no-fault references in FDD systems show a statistical distribution with various uncertainties. In this paper, steady-state variations of measurement residuals were investigated by utilizing built-in temperature sensors in a heat pump for the model development and the final application.

Dynamic Performance Simulation of OTEC According to Seawater Temperature Change (해수온도변화에 따른 온도차발전시스템의 동적 성능 시뮬레이션)

  • Lim, Seung-Taek;Lee, Ho-saeng;Kim, Hyeon-Ju
    • Journal of Power System Engineering
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    • v.22 no.1
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    • pp.34-40
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    • 2018
  • In this paper, Performance of 1MW OTEC system using R32 with varying seawater temperature range is studied. Steady state cycle is designed and its output and generation efficiency were 1,014kW and 2.72%, respectively. Compared to dynamic cycle, system performance and change during long term operation is studied. The simulation is performed by decreasing surface seawater temperature from $29^{\circ}C$ to $25^{\circ}C$ with 20 minute of reaction time. Dynamic cycle with same condition applied to steady state cycle and it showed output and efficiency of 1,020kW and 2.75% respectively. Seawater temperature decreased from $29^{\circ}C$ and the vapor fraction of refrigerant decreased below 1 at $28^{\circ}C$. While the vapor fraction was above 1, the turbine output decreased by 0.017kW per second. After the seawater temperature reached $26.2^{\circ}C$, the turbine output decreased by 1.03kW per second. However, Driving the turbine below the saturation temperature caused the occurrence of surging and the influx of liquid refrigerant. When the liquid separator having a capacity of 1.0 m3 was used, the flow into the turbine was confirmed after 5 minutes from the first liquid refrigerant coming into the separator.

Development of LNG Terminal Flow Rate Data Reconciliation Method (LNG 터미널 유량 보정 방법 개발)

  • Lee, Sang-Ho;Lee, Chul-Jin;Lim, Young-Sub;Park, Chan-Saem;Han, Chong-Hun
    • Journal of the Korean Institute of Gas
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    • v.14 no.6
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    • pp.21-26
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    • 2010
  • Especially in Korea, LNG terminals commonly have huge scale because of the high demand of natural gas, and for the safe operation of terminal wide observation on temperature is necessary. That is the reason why the terminal has thermometer all over the facility but another information, flow rate, is insufficient. By the way, in pipeline, temperature difference is highly related with flow rate and with some simple assumptions, we can estimate flow rate. And through the steady state data reconciliation, the flow rate data become more reliable. In this research, we will study about flow rate data reconciliation method for LNG terminal and case study.

Investigation on transient characteristics of current leads for superconducting magnet (초전도 자석에 사용되는 전류 도입선의 과도 특성에 관한 연구)

  • 인세환;정상권
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2002.02a
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    • pp.50-55
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    • 2002
  • The transient numerical analysis was performed for vapor cooled current leads. The present numerical modeling considered that there is temperature difference between the copper lead and the helium vapor flow. This numerical modeling was compensated and validated by the experiment with commercially available 100 A current leads. The numerical modeling in this paper described thermal characteristics of overloaded current leads more accurately than the conventional steady state analysis. Proper design of overloaded current leads was suggested by indicating the appropriate overloading factor in the pulse mode operation.

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Analysis of Resonant Characteristics in Asymmetrical Control Half Bridge Converter (하프 브리지 컨버터의 비대칭 제어 공진 특성 분석)

  • Ahn J.R.;Kwon M.I.;Jang D.H.
    • Proceedings of the KIPE Conference
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    • 2003.07a
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    • pp.58-61
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    • 2003
  • In this paper, resonant Characteristics of the soft switched asymmetrical half bridge converter is analysis. The operation principle for proposed converter is explained in steady state and its circuit is analyzed by means of equivalent circuit. Experimental results carried out on a system prototype are included in this paper.

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