27,937 research outputs found
Oscillation energy based sensitivity analysis and control for multi-mode oscillation systems
This paper describes a novel approach to analyze and control systems with
multi-mode oscillation problems. Traditional single dominant mode analysis
fails to provide effective control actions when several modes have similar low
damping ratios. This work addresses this problem by considering all modes in
the formulation of the system kinetic oscillation energy. The integral of
energy over time defines the total action as a measure of dynamic performance,
and its sensitivity allows comparing the performance of different
actuators/locations in the system to select the most effective one to damp the
oscillation energy. Time domain simulations in the IEEE 9-bus system and IEEE
39-bus system verify the findings obtained by the oscillation energy based
analysis. Applications of the proposed method in control and system planning
are discussed.Comment: Conference paper, IEEE PESGM 201
Further studies on relic neutrino asymmetry generation I: the adiabatic Boltzmann limit, non-adiabatic evolution, and the classical harmonic oscillator analogue of the quantum kinetic equations
We demonstrate that the relic neutrino asymmetry evolution equation derived
from the quantum kinetic equations (QKEs) reduces to the Boltzmann limit that
is dependent only on the instantaneous neutrino number densities, in the
adiabatic limit in conjunction with sufficient damping. An original physical
and/or geometrical interpretation of the adiabatic approximation is given,
which serves as a convenient visual aid to understanding the sharply
contrasting resonance behaviours exhibited by the neutrino ensemble in opposing
collision regimes. We also present a classical analogue for the evolution of
the difference in and number densities which, in the
Boltzmann limit, is akin to the behaviour of the generic reaction with equal forward and reverse reaction rate constants. A
new characteristic quantity, the matter and collision-affected mixing angle of
the neutrino ensemble, is identified here for the first time. The role of
collisions is revealed to be twofold: (i) to wipe out the inherent
oscillations, and (ii) to equilibrate the and number
densities in the long run. Studies on non-adiabatic evolution and its possible
relation to rapid oscillations in lepton number generation also feature, with
the introduction of an adiabaticity parameter for collision-affected
oscillations.Comment: RevTeX, 38 pages including 8 embedded figure
Using Effective Generator Impedance for Forced Oscillation Source Location
Locating the sources of forced low-frequency oscillations in power systems is
an important problem. A number of proposed methods demonstrate their practical
usefulness, but many of them rely on strong modeling assumptions and provide
poor performance in certain cases for reasons still not well understood. This
paper proposes a systematic method for locating the source of a forced
oscillation by considering a generator's response to fluctuations of its
terminal voltages and currents. It is shown that a generator can be represented
as an effective admittance matrix with respect to low-frequency oscillations,
and an explicit form for this matrix, for various generator models, is derived.
Furthermore, it is shown that a source generator, in addition to its effective
admittance, is characterized by the presence of an effective current source
thus giving a natural qualitative distinction between source and nonsource
generators. Detailed descriptions are given of a source detection procedure
based on this developed representation, and the method's effectiveness is
confirmed by simulations on the recommended testbeds (eg. WECC 179-bus system).
This method is free of strong modeling assumptions and is also shown to be
robust in the presence of measurement noise and generator parameter
uncertainty.Comment: 13 page
Energy Conservative Limit Cycle Oscillations
This paper shows how globally attractive limit cycle oscillations can be induced in a system with a nonlinear feedback element. Based on the same principle as the Van der Pol oscillator, the feedback behaves as a negative damping for low velocities but as an ordinary damper for high velocities. This nonlinear damper can be physically implemented with a continuous variable transmission and a spring, storing energy in the spring when the damping is positive and reusing it when the damping is negative. The resulting mechanism has a natural limit cycle oscillation that is energy conservative and can be used for the development of robust, dynamic walking robots
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