• Title/Summary/Keyword: Dynamics of SVC

Search Result 7, Processing Time 0.019 seconds

Simulation of Reactive Power Compensation in Grid-Connected Wind Power Generation System (계통연계 풍력발전시스템의 무효전력 보상에 대한 시뮬레이션)

  • Ro, Kyoung-Soo;Jang, Bo-Kyoung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
    • /
    • v.25 no.6
    • /
    • pp.82-89
    • /
    • 2011
  • Reactive power support is considered to be necessary for dealing with a voltage stability issue with wind turbine system employing squirrel-cage induction generator(SCIG). This paper analyses steady-state characteristics of the SCIG wind turbine system by simulating torque-slip characteristics of SCIG with respect to variations of interconnecting network strength and generator terminal voltage. It also presents dynamics analysis of SCIG wind turbine system on Simulink to investigate the impact of static var compensator(SVC) and static synchronous compensator(STATCOM) on transient stability enhancement. It analysed transient stability with varying fault duration times and compared the transient stability characteristics with varying rated capacities of SVC and STATCOM. It is shown that the STATCOM has a better performance and reactive power support compared to SVC.

Fluid Dynamic Efficiency of an Anatomically Correct Total Cavopulmonary Connection: Flow Visualizations and Computational Fluid Dynamic Studies

  • Yun, S.H.;Kim, S.Y.;Kim, Y.H.
    • International Journal of Vascular Biomedical Engineering
    • /
    • v.1 no.2
    • /
    • pp.36-41
    • /
    • 2003
  • Both flow visualizations and computational fluid dynamics were performed to determine hemodynamics in a total cavopulmonary connection (TCPC) model for surgically correcting congenital heart defects. From magnetic resonance images, an anatomically correct glass model was fabricated to visualize steady flow. The total flow rates were 4, 6 and 8L/min and flow rates from SVC and IVC were 40:60. The flow split ratio between LPA and RPA was varied by 70:30, 60:40 and 50:50. A pressure-based finite-volume software was used to solve steady flow dynamics in TCPC models. Results showed that superior vena cava(SVC) and inferior vena cava(IVC) flow merged directly to the intra-atrial conduit, creating two large vortices. Significant swirl motions were observed in the intra-atrial conduit and pulmonary arteries. Flow collision or swirling flow resulted in energy loss in TCPC models. In addition, a large intra-atrial channel or a sharp bend in TCPC geometries could influence on energy losses. Energy conservation was efficient when flow rates in pulmonary branches were balanced. In order to increase energy efficiency in Fontan operations, it is necessary to remove a flow collision in the intra-atrial channel and a sharp bend in the pulmonary bifurcation.

  • PDF

A Hybrid Scheme of the Transport Error Control for SVC Video Streaming (SVC 비디오 스트리밍을 위한 복합형 전송 오류 제어 기법)

  • Seo, Kwang-Deok;Moon, Chul-Wook;Jung, Soon-Heung;Kim, Jin-Soo
    • Journal of KIISE:Information Networking
    • /
    • v.36 no.1
    • /
    • pp.34-42
    • /
    • 2009
  • In this paper, we propose a practical hybrid transport error control scheme to provide SVC video streaming service over error-prone IP networks. Many error control mechanisms for various video coding standards have been proposed in the literature. However, there is little research result which can be practically applicable to the multilayered coding structure of SVC(the scalable extension of H.264/AVC). We present a new hybrid transport error control scheme that efficiently combines layered Forward Error Correction(FEC) and Automatic Repeat Request(ARQ) for better packet-loss resilience. In the proposed hybrid error control, we adopt ACK-based ARQ instead of NACK-based ARQ to maximize throughput which is the amount of effective data packets delivered over a physical link per time unit. In order to prove the effectiveness of the proposed hybrid error control scheme, we adopt NIST-Net network emulator which is a general-purpose tool for emulating performance dynamics in IP networks. It is shown by simulations over the NIST-Net that the proposed hybrid error control scheme shows improved packet-loss resilience even with much less number of overhead packets compared to various conventional error control schemes.

Fluid Dynamic Efficiency of an Anatomically Correct Total Cavopulmonary Connection: Flow Visualizations and Computational Fluid Dynamic Studies

  • Yun, S.H.;Kim, S.Y.;Kim, Y.H.
    • International Journal of Vascular Biomedical Engineering
    • /
    • v.2 no.1
    • /
    • pp.11-16
    • /
    • 2004
  • Both flow visualizations and computational fluid dynamics were performed to determine hemodynamics in a total cavopulmonary connection (TCPC) model for surgically correcting congenital heart defects. From magnetic resonance images, an anatomically correct glass model was fabricated to visualize steady flow. The total flow rates were 4, 6 and 8L/min and flow rates from SVC and IVC were 40:60. The flow split ratio between LPA and RPA was varied by 70:30, 60:40 and 50:50. A pressure-based finite-volume software was used to solve steady flow dynamics in TCPC models. Results showed that superior vena cava(SVC) and inferior vena cava(IVC) flow merged directly to the intra-atrial conduit, creating two large vortices. Significant swirl motions were observed in the intra-atrial conduit and pulmonary arteries. Flow collision or swirling flow resulted in energy loss in TCPC models. In addition, a large intra-atrial channel or a sharp bend in TCPC geometries could influence on energy losses. Energy conservation was efficient when flow rates in pulmonary branches were balanced. In order to increase energy efficiency in Fontan operations, it is necessary to remove a flow collision in the intra-atrial channel and a sharp bend in the pulmonary bifurcation.

  • PDF

Hybrid Voltage Stability Analysis (혼합형 전압안정도 해석)

  • Kim, Won-Gyeom;Kim, Geon-Jung;Ju, Un-Pyo;Lee, Sang-Jung
    • The Transactions of the Korean Institute of Electrical Engineers A
    • /
    • v.49 no.2
    • /
    • pp.43-49
    • /
    • 2000
  • It is a complex process to analyze power system voltage stability problems with all of the dynamics of a system, because a large power network system sophisticatedly consists of generators, lines, loads and so forth. So we considered the dynamics of loads so as to analyze voltage stability method- by carrying out an analysis of steady state voltage stability and dynamic voltage stability simultaneously. To perform a steady state voltage stability program in advance makes it possible to cut down on laborious calculations so that an analysis of dynamic voltage stability becomes concise. The validity and efficiency of the method presented in this paper were verified by applying the IEEE 14 bus system.

  • PDF

PROPAGATION OF SURFACE WAVES ON IRREGULAR BED TOPOGRAPHY

  • WARKE A. S.;DAS S. K.;DEBNATH L.
    • Journal of applied mathematics & informatics
    • /
    • v.20 no.1_2
    • /
    • pp.197-208
    • /
    • 2006
  • This paper deals with the exact solution of surface gravity waves in an ocean with irregular bed topography. In order to obtain water surface elevation and run-up of infra-gravity waves when the bed is either wavy or exponential, closed form solutions are obtained. Numerical computations indicate that when solitary wave or sinusoidal wave conditions are applied at the boundary, water surface elevation attains near Gaussian profile.

Blood Flow Changes by Anastomotic Method in Fontan Operation (폰탄 수술에서 문합방법에 따른 혈류 변화)

  • Kim, S.H.;Park, Y.H.;Cho, B.K.;Kim, J.H.;Hong, Y.S.;Kim, Y.H.;Kim, S.S.
    • Proceedings of the KOSOMBE Conference
    • /
    • v.1996 no.05
    • /
    • pp.203-206
    • /
    • 1996
  • To understand the local fluid dynamics for different desists of Fontan operation, five models were made out of Pyrex glass to facilitate in-vitro study. Model I, II and III have same position of the center of the anastomosis of the IVC( inferior vena cava) with that of the SVC(superior vena cava), but Model IV and V have 10 mm offset between them. Also the anastomotic junction angles are different(Model I and $IV:90^{\circ}$, Model II and $V:70^{\circ}$, Model $III:45^{\circ}$). These models were then connected to a flow loop for flow visualization study. In Model I any dominant vortex was not seen in the central region of the juntion, but a large unstable vortex was created in the Model II and III. In Model IV and V a significant stagnation region was created in the middle of the offset region. It also showed that the flow direction from the IVC and SVC to the LPA(left pulmonary artery) and RPA(right pulmonary artery) highly depends on the offset of the junction rather than the anastomotic junction angle.

  • PDF