Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 39 for “"stability margin"”.
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A generalizable methodology for stability assessment of walking aid users
Walking aids (WAs) aim to improve stability and are used by up to 50% of older Europeans. Paradoxically, their use has been linked to a 2-3-fold increase in the risk of falling. The reasons of this association are unknown, indeed WA use remains poorly understood as clinicians have no objective …
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Probabilistic analysis of compression system stability using importance sampling
The probability of instability is computed via a new approach based on Importance Sampling and a dynamic compression system model. In contrast to ordinary Monte Carlo methods Importance Sampling offers reduced confidence intervals, reduced number of samples and reduced model execution times. The …
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The robustness of H-infinity control
… A norm was introduced called the parametric stability margin, to serve as a measure of this robustness. A fragile controller is defined as a controller that is very sensitive to changes in its controller coefficients and any small change from the nominal controller will result in closed loop …
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Effectiveness of a Serpentine Inlet Duct Flow Control Scheme at Design and Off-Design Simulated Flight Conditions
… (AIP) was then used to predict the resulting stability for a compression system. This study was conducted using a model of a compact, low observable, engine inlet duct developed by Lockheed Martin. A flow control technique using air injection through microjets at 1% of the inlet mass flow rate …
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Distortion Tolerant Fan Design
… mechanical integrity, aerodynamic efficiency and stability. The aim of this thesis is to understand the impact of strengthening rotor blades on aerodynamic performance, investigate how the performance can be improved by modifying the fan rotor radial work profile and explain the mechanism that …
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Voltage collapse prediction for interconnected power systems
… modal analysis method is used to investigate the stability of the power system. Q-V curves are used to confirm the obtained results by modal analysis method and to predict the stability margin or distance to voltage collapse based on reactive power load demand. The load characteristics are …
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Advanced Control Schemes for High-Bandwidth Multiphase Voltage Regulators
… approach. However, it is found that the stability margin of current-mode control in high-BW design is very sensitive to operating conditions and component tolerance, depending on the performance of the current-sensing techniques, modulation schemes, and interleaving approaches. The …
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Stability analysis of natural circulation in BWRs at high pressure conditions
… of this work is to assess the characteristics of stability in a NCBWR at rated conditions, and the sensitivity to design and operating conditions in comparison to previous BWRs. Two kinds of instabilities, namely Ledinegg flow excursion and Density Wave Oscillations (DWO), have been studied. The …
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Spillover stabilization in the control of large flexible space structures
… modal controllers with improved spillover stability properties. It is based on the premise that the structural dynamicist will be able to predict more vibration modes than would be practical to include in the design of the controller. The proposed method calls for designing the observer so …
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Qualitative insights into the voltage stability problem
… of the bus indicators for the problem of voltage stability. The purpose is to learn more about the behavior and to observe the factors that cause mis-ranking in estimating the stability margin. Three indicators are examined, the L-index, the coupled-port method, and the P-index. it found that the …
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Avaliação da estabilidade a pequenos sinais em sistemas CA/CC em paralelo
… AC systems from the perspective of small-signal stability of electric power systems. We present aspects related to linear and nonlinear representation of the DC link controls. The studies are performed using modal analysis techniques for power systems, as well as linear and nonlinear time domain …
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Online Voltage Stability Monitoring and Control Using Limited Synchrophasor Measurements
… can be operated close to the verge of voltage instability. With the application of Phasor Measurement Units (PMUs), dispatchers are able to monitor long term voltage stability in a real time operational environment. This research addresses the critical issues by proposing three different methods. …
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Multiple Swing Out-of-Step Relaying
The reduced stability margin, at which power systems are being operated these days, has encouraged the power industry to come up with new ideas to guarantee a continuous and reliable operation of the bulk interconnected system. The development of the synchronized Phasor Measurement technology, and …
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Rough-terrain mobile robot planning and control with application to planetary exploration
… rover kinematic structure to optimize tipover stability margin is presented. Both methods utilize models developed earlier in the thesis.
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Design of secondary voltage and stability controls with multiple control objectives
… research is to design a Decentralized Voltage/Stability Monitoring and Control System to counteract voltage violations and the impact of disturbances/contingencies on power system voltage stability. A decentralized voltage and stability control system is designed to coordinate the controls of …
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Axisymmetric equilibrium and stability analysis in Alcator C-Mod, including effects of current profile, measurement noise and power supply saturation
… of identifying which variables affect vertical stability and which ones are not directly controlled/controllable; identifying the physical region of these variables, and the corresponding most unstable equilibria; and designing the control system to stabilize all equilibria with sufficient …
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DQ-Frame Small-Signal Stability Analysis of AC Systems with Single-Phase and Three-Phase Converters
… and data centers has introduced significant stability challenges. This dissertation presents a novel approach to modeling and comprehensive stability analysis for both single-phase and three-phase converters, addressing vital gaps in the existing literature. The first part of the dissertation …
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Robustness and Stability Analysis with a Heavily-Meshed Distribution Network
… is compared using an index called static stability breakdown margin parameter of circuit elements. For this study, a low-voltage heavily-meshed distribution test system is also proposed. Additionally, a study is conducted to show how reliable the meshed test system is against any fault in …
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Effect of DERs on the Voltage Stability of Transmission Systems using a Voltage Stability Index
… on the impact on a transmission system's voltage stability. When the voltage stability at a point in the system is compromised, it can affect the entire power system's overall security, quality, and reliability. Therefore, this work aims to assess the system's stress due to increased loading …
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A three-dimensional turbine engine analysis compressor code (TEACC) for steady-state inlet distortion
… generally reduces the engine compressor stability margin and may induce compressor surge at high rotational speeds, or rotating stall at lower rotational speeds. Therefore, a computational fluid dynamics (CFD) based compressor simulation would be very useful in the design, test, and …
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