Parametric analysis of the stability of VSC-HVDC converters

A frequency-domain approach for direct parametric analysis of limit points (LPs) of nonlinear dynamical systems is presented in this paper. Instead of computing responses curves for several values of a given system parameter, the direct tracking of LPs is performed. The whole numerical procedure is based on the harmonic balance method (HBM) and can be decomposed in three distinct steps. First, a response curve is calculated by HBM combined with a continuation technique until an LP is detected. Then this starting LP is used to initialize the direct tracking of LPs which is based on the combination of a so-called extended system and a continuation technique. With only one computation, a complete branch of LPs is obtained, which provides the stability boundary with respect to system parameters such as nonlinearity or excitation level. Several numerical examples demonstrate the capabilities and the performance of the proposed method.

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A Method for Parametric Analysis of Stability Boundaries for Nonlinear Periodic Vibrations of Structures With Contact Interfaces

Volume 7C: Structures and Dynamics ◽

10.1115/gt2018-76545 ◽

2018 ◽

Author(s):

E. P. Petrov

Keyword(s):

Parametric Analysis ◽

Large Scale ◽

Contact Stiffness ◽

Stability Loss ◽

Forced Response ◽

Scale Model ◽

Design Parameters ◽

Stability Boundaries ◽

Analysis Of Stability ◽

The Stability

A method for parametric analysis of the stability loss boundary has been developed for periodic regimes of nonlinear forced vibrations for a first time. The method allows parametric frequency-domain calculations of the stability loss together with the vibration amplitudes and design parameter values corresponding to the stability boundaries. The tracing algorithm is applied to obtain the trajectories of stability loss points as functions of design parameters. The parametric stability loss is formulated for cases when: (i) the design parameters characterise the properties of nonlinear contact interfaces (e.g. gap, contact stiffness, friction coefficient, etc.) and (ii) the design parameters describe linear components of the analysed structure (e.g. parameters of geometric shape, material, natural frequencies, modal damping etc.) and (iii) these parameters describe the excitation loads (e.g. their level, distribution or frequency). An approach allowing the multiparametric analysis of stability boundaries is proposed. The method uses the multiharmonic representation of the periodic forced response and aimed at the analysis of realistic gas-turbine structures comprising thousands and millions degrees of freedom. The method can be used for the effective search of isolated branches of the nonlinear solutions and examples of detection and search of the isolated branches are given: for relatively small and for large-scale finite element models. The efficiency of the method for calculation of the stability boundaries and for the search of isolated branches is demonstrated on simple systems and on a large-scale model of a turbine blade.

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A Method for Parametric Analysis of Stability Boundaries for Nonlinear Periodic Vibrations of Structures With Contact Interfaces

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4040850 ◽

2018 ◽

Vol 141 (3) ◽

Author(s):

E. P. Petrov

Keyword(s):

Parametric Analysis ◽

Large Scale ◽

Contact Stiffness ◽

Stability Loss ◽

Forced Response ◽

Scale Model ◽

Design Parameters ◽

Stability Boundaries ◽

Analysis Of Stability ◽

The Stability

A method for parametric analysis of the stability loss boundary has been developed for periodic regimes of nonlinear forced vibrations for a first time. The method allows parametric frequency-domain calculations of the stability loss together with the vibration amplitudes and design parameter values corresponding to the stability boundaries. The tracing algorithm is applied to obtain the trajectories of stability loss points as functions of design parameters. The parametric stability loss is formulated for cases when (i) the design parameters characterize the properties of nonlinear contact interfaces (e.g., gap, contact stiffness, and friction coefficient); (ii) the design parameters describe linear components of the analyzed structure (e.g., parameters of geometric shape, material, natural frequencies, and modal damping); and (iii) these parameters describe the excitation loads (e.g., their level, distribution or frequency). An approach allowing the multiparametric analysis of stability boundaries is proposed. The method uses the multiharmonic representation of the periodic forced response and aimed at the analysis of realistic gas-turbine structures comprising thousands and millions degrees-of-freedom (DOF). The method can be used for the effective search of isolated branches of the nonlinear solutions and examples of detection and search of the isolated branches are given: for relatively small and for large-scale finite element (FE) models. The efficiency of the method for calculation of the stability boundaries and for the search of isolated branches is demonstrated on simple systems and on a large-scale model of a turbine blade.

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Experimental study and parametric analysis on the stability behavior of 7A04 high-strength aluminum alloy angle columns under axial compression

Thin-Walled Structures ◽

10.1016/j.tws.2016.08.029 ◽

2016 ◽

Vol 108 ◽

pp. 305-320 ◽

Cited By ~ 11

Author(s):

Y.Q. Wang ◽

Z.X. Wang ◽

X.G. Hu ◽

J.K. Han ◽

H.J. Xing

Keyword(s):

Experimental Study ◽

Aluminum Alloy ◽

Axial Compression ◽

Parametric Analysis ◽

High Strength ◽

Stability Behavior ◽

High Strength Aluminum Alloy ◽

The Stability

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Parametric Analysis of an Embankment Dam’s Stability

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.3180 ◽

2019 ◽

Vol 9 (6) ◽

pp. 5016-5020

Author(s):

A. H. Bhutto ◽

S. Zardari ◽

G. S. Bhurgri ◽

M. A. Zardari ◽

R. Bhanbhro ◽

...

Keyword(s):

Parametric Analysis ◽

Friction Angle ◽

Soil Conditions ◽

Embankment Dam ◽

Strength Parameters ◽

Sandy Gravel ◽

Embankment Dams ◽

The Stability

This paper presents a stability parametric analysis of a 59m high embankment dam. The analysis was performed in order to evaluate the minimum values of strength parameters that satisfy the stability requirements of the dam. The parametric analysis was conducted for three main zones of the dam: upstream shell, core, and downstream shell, which consisted of sandy gravel, clay, and random fill respectively. The friction angles of these materials were gradually decreased in order to represent different soil conditions. It was observed that stability requirements for the end of construction and after the filling of the reservoir could be satisfied if friction angle values of the sandy gravel and the random fill are 34º and 32º, instead of 37º and 34º. However, the value of the core’s cohesion could be utilized as 30º without any reduction so that the dam could be safe after the filling of the reservoir. The results of this study could be beneficial to practicing engineers for the design of safe and economical embankment dams.

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Open discussion

Symposium - International Astronomical Union ◽

10.1017/s0074180900029533 ◽

1982 ◽

Vol 99 ◽

pp. 605-613

Author(s):

P. S. Conti

Keyword(s):

Buenos Aires ◽

Large Mass ◽

List Type ◽

Common Phenomenon ◽

Open Discussion ◽

The Stability ◽

Ring Nebulae

Conti: One of the main conclusions of the Wolf-Rayet symposium in Buenos Aires was that Wolf-Rayet stars are evolutionary products of massive objects. Some questions:–Do hot helium-rich stars, that are not Wolf-Rayet stars, exist?–What about the stability of helium rich stars of large mass? We know a helium rich star of ∼40 MO. Has the stability something to do with the wind?–Ring nebulae and bubbles : this seems to be a much more common phenomenon than we thought of some years age.–What is the origin of the subtypes? This is important to find a possible matching of scenarios to subtypes.

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