• Title/Summary/Keyword: Line flow sensitivity

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A Study on Evaluating of Voltage Stability Considering Line Flow Sensitivity (선로조류 감도계수를 고려한 전압안정도 평가에 관한 연구)

  • Kim, Sae-Young;Choi, Sang-Kyu;Song, Kil-Yeong
    • Proceedings of the KIEE Conference
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    • 1997.07c
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    • pp.1118-1120
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    • 1997
  • This paper presents a simple method for evaluating of voltage stability using the line flow equation. Line flow equations ($P_{ij}$, $Q_{ij}$) are comprised of state variable, $V_i$, ${\delta}_i$, $V_j$ and ${\delta}_j$, and line parameter, r and x. Using the feature of polar coordinate, these becomes one equation with two variables, $V_i$ and $V_j$. Moreover, if bus j is slack or generater bus, which is specified voltage magnitude, it becomes one equation with one variable $V_i$, that is, may be formulated with the second-order equation for $V_i^2$. Therefore, multiple load flow solutions may be obtained with simple computation, and the formulated equation used for approximately evaluating of voltage stability limit considering line flow sensitivity. The proposed method was validated to 2-bus and IEEE 6-bus system.

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A Study on Efficient Calculation of Effective Reactive Power Reserves Using Sensitivity Analysis

  • Bae, Moonsung;Lee, Byongjun
    • Journal of Electrical Engineering and Technology
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    • v.12 no.5
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    • pp.1689-1696
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    • 2017
  • In recent academic and industrial circles of the Republic of Korea, the securement of available reactive power reserve against the line faults is at issue. Thus, simulations have been performed for the securing of effective reactive power reserve (effective Q) to prepare for the line faults and improve reactive power monitoring and control methods. That is, a research has been conducted for the fast-decoupled Newton-Raphson method. In this study, a method that distinguishes source and sink regions to carry out faster provision of information in the event of line fault has been proposed. This method can perform quantification with the formula that calculates voltage variations in the line flow. The line flow and voltage changes can be easily induced by the power flow calculation performed every second in the operation system. It is expected that the proposed method will be able to contribute to securement of power system stability by securing efficient reactive power. Also, the proposed method will be able to contribute to prepare against contingencies effectively. It is not easy to prepare quickly for the situation where voltage drops rapidly due to the exhaustion of reactive power source by observing voltage information only. This paper's simulation was performed on the large scale Korean power system in steady state.

Study on the Security-Constrained Optimal Power Flow (상정사고를 고려한 최적조류계산 연구)

  • Choi, Kil;Won, Jong-Ryul
    • Proceedings of the KIEE Conference
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    • 2002.11b
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    • pp.381-383
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    • 2002
  • This paper proposes a MATLAB program for solving security-constrained optimal power flow using linear programming. Security-constrained optimal power flow can find an optimal generation satisfying bus voltage limits, line flow limits, reactive generation limits, even if contingency occurs. Sensitivity matrixes are obtained based on power flow solutions with and without single line contingency. This program is tested for an IEEE 14bus system with 5 generators Results shows good ability of finding optimal solution in case of a single line contingency.

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A Study on an Algorithm of Line Switching and Bus Separation for Alleviating Overloads by the Use of Line Power Tracing and Sensitivity (선로유효전력 Tracing과 민감도를 활용한 선로 과부하 해소 스위칭 및 모선분리 알고리즘에 관한 연구)

  • Lee, Byung-Ha;Hwang, Sung-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.11
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    • pp.2007-2016
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    • 2011
  • In this paper, a new algorithm for alleviating overloads in power networks by the use of line power tracing and sensitivity is proposed to perform line switching and bus separation effectively. Also, a new bus separation index based on line power tracing is presented to find the bus to be separated for relieving overloads effectively. By applying the sensitivity of the line flow with respect to the change of the line impedance, both switching-on and switching-off of the lines for alleviating overloads in power networks are performed systematically at once. The number of the considered cases for line switching and bus separation can be greatly reduced and the best combination of line switching and bus separation can be acquired efficiently by the use of the sensitivity and the bus separation index. In order to show the effects of this algorithm, it is applied to a small scale power system of IEEE 39-bus system and practical power systems of KEPCO.

The Enhancement of Power System Security Using flexible AC Transmission Systems (FACTS) (FACTS 기기를 이용한 전력시스템의 안전도 향상)

  • 송성환;임정욱;문승일
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.52 no.3
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    • pp.165-172
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    • 2003
  • This paper presents an operation scheme to enhance the power system security by applying FACTS on Power systems. Three main generic types of FACTS devices are suggested an illustrated. Flow congestions over lines have been solved by controlling active power of series-compensated FACTS devices and low voltages at buses have been solved by controlling reactive power of shunt-compensated FACTS devices. Especially, Especially, UPFC has been applied in both line congestion and low voltages. Two kinds of indices which indicate the power system security level related to line flow and bus voltage are utilized in this paper. They have been minimized to enhance the power system security level through the iterative method and the sensitivity vector of security index is derived to determine the direction to minimum. The proposed algorithm has been tested on the IEEE 57-bus system with FACTS devices in a normal condition and a line-faulted contingency.

The Optimal Operating Points of Multiple UPFCs for Enhancing Power System Security Level (전력시스템 안전도 향상을 위한 다기 UPFC의 최적 운전점 결정)

  • 임정욱;문승일
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.50 no.8
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    • pp.388-394
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    • 2001
  • This paper presents how to determine the optimal operating points of Unified Power Flow controllers (UPFC) the line flow control of which can enhance system security level. In order to analyze the effect of these devices on the power system, the decoupled model has been employed as a mathematical model of UPFC for power flow analysis. The security index that indicates the level of congestion of transmission line has been proposed and minimized by iterative method. The sensitivity of objective function for control variables of and UPFC has been derived, and it represents the change in the security index for a given set of changes in real power outputs of UPFC. The proposed algorithm with sensitivity analysis gives the optimal set of operating points of multiple UPECs that reduces the index or increases the security margin and Marquart method has been adopted as an optimization method because of stable convergence. The algorithm is verified by the 10-unit 39-bus New England system that includes multiple FACTS devices. The simulation results show that the power flow congestion can be relieved in normal state and the security margin can be guaranteed even in a fault condition by the cooperative operation of multiple UPECs.

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Determination of Reactive Power Compensation Considering Large Disturbances for Power Flow Solvability in the Korean Power System

  • Seo, Sang-Soo;Kang, Sang-Gyun;Lee, Byong-Jun;Kim, Tae-Kyun;Song, Hwa-Chang
    • Journal of Electrical Engineering and Technology
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    • v.6 no.2
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    • pp.147-153
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    • 2011
  • This paper proposes a methodology using a tool based on the branch-parameter continuation power flow (BCPF) in order to restore the power flow solvability in unsolvable contingencies. A specified contingency from a set of transmission line contingencies is modeled, considering the transient analysis and practice in the Korean power system. This tool traces a solution path that satisfies the power flow equations with respect to the variation of the branch parameter. At a critical point, in which the branch parameter can move on to a maximum value, a sensitivity analysis with a normal vector is performed to identify the most effective compensation. With the sensitivity information, the location of the reactive power compensation is determined and the effectiveness of the sensitivity information is verified to restore the solvability. In the simulation, the proposed framework is then applied to the Korean power system.

Neck Formation in Drawing Processes of Fibers

  • Chung, Kwansoo;Yoon, Hyungsop;Youn, Jae Ryoun
    • Fibers and Polymers
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    • v.2 no.1
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    • pp.140-143
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    • 2001
  • To better understand the formation of necking in drawing processes of fibers, strain distributions during drawing processes have been analyzed. For simplicity, one-dimensional incompressible steady flow at a constant temperature was assumed and quasi-static model was used. To describe mechanical properties of solid polymers, non-linear visco-plastic material properties were assumed using the power law type hardening and rate-sensitive equation. The effects of various parameters on the neck formation were matematically analyzed. As material property parameters, strain-hardening parameter, visco-elastic coefficient and strain-rate sensitivity were considered and, for process parameters, the drawing ratio and the process length were considered. It was found that rate-insensitive materials do not reach a steady flow state and the rate-sensitivity plays a key role to have a steady flow. Also, the neck formation is mainly affected by material properties, especially for the quasi-static model. If the process length changes, the strain distribution was found to be proportionally re-distributed along the process line by the factor of the total length change.

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Investigation of Oxidation Sensitivity with Temperature of Steel Plate Type (강판 종별 온도에 따른 산화 민감도 조사)

  • KIM, JUHAN;LEE, KEEMAN
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.5
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    • pp.455-464
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    • 2019
  • Experiments were conducted to investigate the sensitivity of steel plate oxidation with temperature in a simulated furnace. Used steel plates were a general steel and a high tensile steel. Porous media burner (PM burner) used in model furnace was made for uniform temperature profile. The surrounding temperature was controlled by adjusting the flow rate of the mixture in the combustor. Oxide layer analysis was performed using SEM image analysis and EDS line scanning. Both steel sheets showed a tendency to increase the thickness of the steel sheet surface oxide layer as the temperature increases, and it was confirmed that the flaking phenomenon in surface oxidation layer appeared when the temperature was above a certain temperature.

Dynamic Stall Control Using Aerodynamic Sensitivity Analysis (민감도 해석을 이용한 동적실속 제어)

  • Ahn, Tai-Sul;Kim, Hyoung-Jin;Kim, Chong-Am;Rho, Oh-Hyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.8
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    • pp.10-20
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    • 2002
  • The present paper investigates methods to control dynamic stall using an optimal approach. An unsteady aerodynamic sensitivity analysis code is developed by a direct differentiation method from a two-dimensional unsteady compressible Navier-Stokes solver including a two-equation turbulence model. Dynamic stall control is conducted by minimizing an objective function defined at an instant instead of integrating for a period of time. Unsteady sensitivity derivatives of the objective function are calculated by the sensitivity code, and optimization is carried out using a linear line search method at every physical time step. Numerous examples of dynamic stall control using control parameters such as nose radius, maximum thickness of airfoil, or suction show satisfactory results.