Study on the Steady-State Stability Margin of a Weak Section by Using the Online Data of WAMS

2015 ◽  
Vol 738-739 ◽  
pp. 1289-1295
Author(s):  
Wen Chao Zhang ◽  
Xin Qiao Fan ◽  
Yu Long He ◽  
Yan Pan ◽  
Yong Lu
Keyword(s):  
Steady State ◽  
Security Analysis ◽  
Stability Margin ◽  
Static Stability ◽  
Area Measurement ◽  
Online Data ◽  
Wide Area Measurement System ◽  
Stability Limits ◽  
The Impact ◽  
Steady State Stability

To realize the on-line quick analysis of the steady-state stability margin for the weak section of a power grid, a method of dividing the important generator groups according to the impact of the system equivalent impedance on the static stability limits of the section is presented. By using the dynamic information provided by the Wide Area Measurement System (WAMS), the center of inertia (COI) of the section of the two sides system is determined. Then the steady-state stability limits of the transmission section and the static stability margin can be calculated. The algorithm is verified by taking the out-play cross-section of West Inner Mongolia as an example, the results show that the static stability power limit and the steady-state stability margin of the section can be obtained accurately according to the presented algorithm. This algorithm can provide an effective analytical method for the online static stability security analysis of a power system.

An Exercise for Teaching Transient Stability

1994 ◽  
Vol 31 (4) ◽  
pp. 357-361
Author(s):  
C. S. Indulkar
Keyword(s):  
Steady State ◽  
Transient Stability ◽  
Stability Limit ◽  
Synchronous Machine ◽  
Stability Limits ◽  
Steady State Stability

An exercise for teaching transient stability In this paper, the transient stability limits of a synchronous machine for various initial loadings have been determined in terms of its steady-state stability limit.

scholarly journals Stability Analysis and Augmentation Design of a Bionic Multi-Section Variable-Sweep-Wing UAV Based on the Centroid Self-Trim Compensation Morphing

2021 ◽  
Vol 11 (19) ◽  
pp. 8859
Author(s):  
Hang Ma ◽  
Yuxue Ge ◽  
Bifeng Song ◽  
Yang Pei
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Speed ◽  
Stability Margin ◽  
Static Stability ◽  
Sweep Angle ◽  
Stability Performance ◽  
Angle Change ◽  
Stability Change ◽  
The Impact

In this study, a design scheme for a high-aspect-ratio bionic multi-section variable-sweep wing unmanned aerial vehicle (UAV) that utilizes the reverse coordinated change in the sweep angle of the inner and outer wing sections is proposed, which improves the aerodynamic performance and realizes the self-trim compensation of the wing’s centroid. According to the layout characteristics of this type of UAV, a reasonable distribution design of the wingspan ratio of the inner and outer sections is explored, to reduce the impact of aerodynamic center movement and moment of inertia change. The calculation and analysis results show that the coordinated variable-sweep scheme can significantly improve the influence of sweep angle change on the longitudinal static stability margin of UAVs with a high aspect ratio. The coordinated sweep angle change in the inner and outer wing sections can not only reduce the drag during high-speed flight, but also play a significant role in improving the performance of the aircraft at different stages in the mission profile. Appropriately increasing the wingspan proportion of the inner section can reduce the trim resistance of the V-tail, reduce the thrust of the engine, and increase the range and duration of the UAV. From the perspective of stability change, the multi-section variable-sweep wing UAV with a wingspan ratio of the inner and outer sections that is between 1.41 and 1.78 has better dynamic stability performance. Among them, the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.41 has better longitudinal stability performance, while the UAV with a wingspan ratio of the inner and outer sections that is equal to 1.78 has better lateral/directional stability performance.

Aerodynamics analysis of rotor’s impact on the aircraft in the tandem wing configuration

2018 ◽  
Vol 92 (3) ◽  
pp. 336-344
Author(s):  
Marcin Figat
Keyword(s):  
Stability Margin ◽  
Static Stability ◽  
Complex Model ◽  
Numerical Code ◽  
Aerodynamic Coefficients ◽  
Sideslip Angle ◽  
Content Type ◽  
Aerodynamic Analysis ◽  
Stability Derivatives ◽  
The Impact

Purpose This paper aims to present the results of aerodynamic calculation of the aircraft in tandem wing configuration called VTOL. A presented vehicle combines the capabilities of the classic aircraft and helicopters. The aircraft is equipped with two pairs of tilt-rotors mounted on the tips of the front and the rear wing. The main goal of the presented research was to find the aerodynamic impact of both pairs of tilt-rotors on aerodynamic coefficients of the aircraft. Moreover, the rotors impact on the static stability of the aircraft was investigated too. Design/methodology/approach The CFD analysis was made for the complete aircraft in the tandem wing configuration. The computation was performed for the model of aircraft which was equipped with the four sub-models of the front and rear rotors. They were modeled as the actuator discs. This method allows for computing the aerodynamic impact of rotating components on the aircraft body. All aerodynamic analysis was made by the MGAERO software. The numerical code of the software was based on the Euler flow model. The used numerical method allows for the quick computation of very complex model of aircraft with a satisfied accuracy. Findings The result obtained by computation includes the aerodynamic coefficients which described the impact of the tilt rotors on the aircraft aerodynamic. The influence of the angle of attack, sideslip angle and the change of rotor tilt angle was investigated. Evaluation of the influence was made by the stability margin analysis and the selected stability derivatives computation. Practical implications Presented results could be very useful in the computation of dynamic stability of unconventional aircraft. Moreover, results could be helpful during designing the aircraft in the tandem wing configuration. Originality/value This paper presents the aerodynamic analysis of the unconventional configuration of the aircraft which combines the tandem wing feature with the tilt-rotor advantages. The impact of disturbance generated by the front and rear rotors on the flow around the aircraft was investigated. Moreover, the impact of rotors configuration on the aircraft static stability was found too.

Steady-state stability of the doubly fed synchronous machine

1968 ◽  
Vol 4 (1) ◽  
pp. 18-19 ◽  
Author(s):  
R.D. Jackson ◽  
B.W. Phillips
Keyword(s):  
Steady State ◽  
Synchronous Machine ◽  
Doubly Fed ◽  
Steady State Stability

scholarly journals Advanced Constitutive Modeling of the Thixotropic Elasto-Visco-Plastic Behavior of Blood: Steady-State Blood Flow in Microtubes

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Constitutive Model ◽  
Blood Plasma ◽  
Constitutive Modeling ◽  
Flow Direction ◽  
Momentum Balance ◽  
Plastic Behavior ◽  
Flow Investigation ◽  
The Impact

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.

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