• Title/Summary/Keyword: continuity and stability

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A Study on Optimal Sequential Reclosing to Improve Transient Stability in Transmission System (송전계통 과도 안정도 향상을 위한 최적 순차 재폐로에 관한 연구)

  • Gwon, Gi-Hyeon;Oh, Yun-Sik;Park, Ji-Kyung;Jo, Kyu-Jung;Sohn, Seung-Hyun;Kim, Chul-Hwan
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.10
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    • pp.1354-1360
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    • 2013
  • In transmission system, reclosing scheme is very useful method to improve continuity of power supply and reliability of system. Especially, high speed reclosing which is used generally in transmission systems has a benefit improving transient stability. However, the reclosing can jeopardize the stability under the condition having high difference of voltage phase angle between both ends. Thus, this paper proposes optimal sequential reclosing scheme to improve transient stability due to reclosing operation. The optimal sequential reclosing is that each phase is closed sequentially considering transient energy. In this paper, 345kV and 154kV transmission system is modeled using EMTP (ElectroMagnetic Transient Program) to verify the performance and effectiveness of optimal sequential reclosing on transient stability. Also, Integral Square Error(ISE) method is used to assess the transient stability.

Incompressible Viscous Flow Analysis Around a Three Dimensional Minivan-Like Body (3차원 미니밴 형상 주위의 비압축성 점성 유동 해석)

  • Jung Y. R.;Park W. G.;Park Y. J.;Kim J. S.
    • 한국전산유체공학회:학술대회논문집
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    • 1996.05a
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    • pp.46-51
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    • 1996
  • The flow field around a three dimensional minivan-like body has been simulated. This study solves 3-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system using second-order accurate schemes for the time derivatives, and third/second-order scheme for the spatial derivatives. The Marker-and-Cell concept is applied to efficiently solve continuity equation. The fourth -order artificial damping is added to the continuity equation for numerical stability. A H-H type multi-block grid system is generated around a three dimensional minivan-like body. Turbulent flows have been modeled by the Baldwin-Lomax turbulent model. The simulation shows three dimensional vortex-pair just behind body. And the flow separation is also observed the rear of the body. It has concluded that the results of present study properly agree with physical flow phenomena.

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Full flow analysis around a Car-like body using Chimera grid technique (Chimera 격자 기법을 이용한 Car-like body 주위의 전체 유동 해석)

  • Oh S. W.;Park W. G.
    • 한국전산유체공학회:학술대회논문집
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    • 1997.10a
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    • pp.86-91
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    • 1997
  • This paper describes analysis of complex flow around Car-like body using Chimera grid technique. As a computational algorithm, Pullboat and Chaussee's Diagonal algorithm is selected to reduce computational time. Introducing hole points flag to this Diagonal algorithm, an algorithm for Chimera grid is generated easily. This study solves 3-D unsteady incompressible Navier-Stokes equations on a non-orthogonal curvilinear coordinate system using second-order accurate schemes for the time derivatives, and third/second-order scheme for the spatial derivatives. The Marker-and-Cell concept is applied to efficiently solve continuity equation. The fourth-order artificial damping is added to the continuity equation for numerical stability, It has concluded that the results of present study properly agree with physical flow phenomena.

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CONVERGENCE AND STABILITY OF ITERATIVE ALGORITHM OF SYSTEM OF GENERALIZED IMPLICIT VARIATIONAL-LIKE INCLUSION PROBLEMS USING (𝜃, 𝜑, 𝛾)-RELAXED COCOERCIVITY

  • Kim, Jong Kyu;Bhat, Mohd Iqbal;Shaf, Sumeera
    • Nonlinear Functional Analysis and Applications
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    • v.26 no.4
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    • pp.749-780
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    • 2021
  • In this paper, we give the notion of M(., .)-𝜂-proximal mapping for a nonconvex, proper, lower semicontinuous and subdifferentiable functional on Banach space and prove its existence and Lipschitz continuity. As an application, we introduce and investigate a new system of variational-like inclusions in Banach spaces. By means of M(., .)-𝜂-proximal mapping method, we give the existence of solution for the system of variational inclusions. Further, propose an iterative algorithm for finding the approximate solution of this class of variational inclusions. Furthermore, we discuss the convergence and stability analysis of the iterative algorithm. The results presented in this paper may be further expolited to solve some more important classes of problems in this direction.

Effect of a Concentrated Mass on the Dynamic Stability of Spinning Free-Free Beam Subjected to a Thrust (회전하는 양단자유보의 동적 안정성에 대한 추력과 집중질량의 영향에 관한 연구)

  • Yoon, Seung-Joon;Kim, Ji-Hwan
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.695-700
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    • 2000
  • The dynamic stability of spinning beam with free boundary conditions for both edges subjected to a tip follower force $P_0+P_1cos{\Omega}t$ is analyzed. It is studied that the beam has a concentrated mass. and then the effects of the axial locations of the mass are studied. The beam is modelled with the Timoshenko type shear deformations. The Hamilton's principle is used to derive the equations of motion, and the critical spinning speed of a beam subjected to a follower force with various non-dimensional parameters is investigated. The finite elements are used with $C^0$ continuity to analyze the spinning beam model, and the method of multiple scales is tried to investigate the dynamic instability regions. The governing equations of motion involve periodic coefficients, which are not in the form of standard Mathieu-Hill equations. The result shows that the concentrated mass increases the dynamic stability of the spinning free-free beam subjected to a thrust.

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Stabilization of pressure solutions in four-node quadrilateral elements

  • Lee, Sang-Ho;Kim, Sang-Hyo
    • Structural Engineering and Mechanics
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    • v.6 no.6
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    • pp.711-725
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    • 1998
  • Mixed finite element formulations for incompressible materials show pressure oscillations or pressure modes in four-node quadrilateral elements. The criterion for the stability in the pressure solution is the so-called Babu$\check{s}$ka-Brezzi stability condition, and the four-node elements based on mixed variational principles do not appear to satisfy this condition. In this study, a pressure continuity residual based on the pressure discontinuity at element edges proposed by Hughes and Franca is used to study the stabilization of pressure solutions in bilinear displacement-constant pressure four-node quadrilateral elements. Also, a solid mechanics problem is presented by which the stability of mixed elements can be studied. It is shown that the pressure solutions, although stable, are shown to exhibit sensitivity to the stabilization parameters.

Dynamic Stability and Response Analysis of Piping System with Internal Flow (내부에 유체가 흐르는 파이프계의 동적안정성 및 응답해석)

  • 이우식;박철희;홍성철
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.1861-1871
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    • 1991
  • In this study, the piping system conveying unsteady flow is considered. The effects of coupling between the pipe motion and the velocity and pressure of fluid are included for the dynamic stability and response analysis of the piping system. The dynamic equations for a piping system are derived by Newtonian dynamics. For the momentum and continuity equations, the concept of moving control volume is applied. Thus, the governing equations derived herein are valid for the applications to the vibration problems occurred when a piping system starts up or shuts down and also when the valves and pumps operate. For a simply supported straight pipe, the stability analysis is conducted for various nondimensional parameters. The dynamic responses, in both stable and unstable region of stability chart, are numerically tested by the use of central difference method.

β-G-BICONTINUOUS, β-G-COMPACTNESS AND β-G-STABLE IN DITOPOLOGICAL TEXTURE SPACES

  • Ibrahim, Hariwan Z.
    • The Pure and Applied Mathematics
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    • v.26 no.1
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    • pp.35-47
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    • 2019
  • The purpose of this paper is to introduce and study new notions of continuity, compactness and stability in ditopological texture spaces based on the notions of ${\beta}$-g-open and ${\beta}$-g-closed sets and some of their characterizations are obtained. Finally, the relationships between these concepts and the other related concepts are investigated.

A Tracking Controller for Robot Manipulator Using Sliding Mode Control (슬라이딩 모드를 이용한 로봇 메니플레이터의 추적제어기)

  • 이정훈;이주장;윤명중;권우현
    • Proceedings of the KIPE Conference
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    • 1996.06a
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    • pp.5-12
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    • 1996
  • In this paper, we design a Continuous Variable Structure Controller which can control robot manipulators to follow the desired planned trajectory with accuracy and robustness, and improve continuity and robustness of variable structure control, based on disturbance observer. We also analyze the stability the proposed algorithm and then verify the usefulness and performance through simulation stuies.

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Three-dimensional simplified slope stability analysis by hybrid-type penalty method

  • Yamaguchi, Kiyomichi;Takeuchi, Norio;Hamasaki, Eisaku
    • Geomechanics and Engineering
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    • v.15 no.4
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    • pp.947-955
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    • 2018
  • In this study, we propose a three-dimensional simplified slope stability analysis using a hybrid-type penalty method (HPM). In this method, a solid element obtained by the HPM is applied to a column that divides the slope into a lattice. Therefore, it can obtain a safety factor in the same way as simplified methods on the slip surface. Furthermore, it can obtain results (displacement and strain) that cannot be obtained by conventional limit equilibrium methods such as the Hovland method. The continuity condition of displacement between adjacent columns and between elements for each depth is considered to incorporate a penalty function and the relative displacement. For a slip surface between the bottom surface and the boundary condition to express the slip of slope, we introduce a penalty function based on the Mohr-Coulomb failure criterion. To compute the state of the slip surface, an r-min method is used in the load incremental method. Using the result of the simple three-dimensional slope stability analysis, we obtain a safety factor that is the same as the conventional method. Furthermore, the movement of the slope was calculated quantitatively and qualitatively because the displacement and strain of each element are obtained.