IEEE Transactions on Power Systems, vol. 28, pp. 3410-3419, Aug 2013
Branching processes can be applied to simulated cascading data to describe the statistics of the ... more Branching processes can be applied to simulated cascading data to describe the statistics of the cascades and quickly predict the distribution of blackout sizes. We improve the procedures for discretizing load shed data so that a Galton-Watson branching process may be applied. The branching process parameters such as average propagation are estimated from simulated cascades and the branching process is then used to estimate the distribution of blackout size. We test the estimated distributions with line outage and load shed data generated by the improved OPA and AC OPA cascading simulations on the IEEE 118-bus system and the Northeast Power Grid of China.
The authors describe two bifurcation instabilities of a thyristor controlled reactor (TCR) circui... more The authors describe two bifurcation instabilities of a thyristor controlled reactor (TCR) circuit in which switching times suddenly change and system stability is lost. The instabilities are unexpected because they are quite different from what might be expected from conventional theory in that they occur without the usual indications such as eigenvalues of a Jacobian matrix crossing the unit circle.
ICOPS 2000. IEEE Conference Record - Abstracts. 27th IEEE International Conference on Plasma Science (Cat. No.00CH37087), 2000
Summary form only given. Due to the increasing bandwidth of Traveling Wave Tube Amplifiers (TWTAs... more Summary form only given. Due to the increasing bandwidth of Traveling Wave Tube Amplifiers (TWTAs), broadband klystrons, and the possibility of electron-beam modulation using Field Emitter Arrays (FEAs), there has been a resurgence of interest in understanding the electron beam-wave interaction when the beam and wave initially have multifrequency content. In the case of the klystron, this corresponds to understanding how the electron beam propagates a multitonal velocity or density disturbance. In a distributed interaction device like the TWTA the beam dynamics, and hence radiation dynamics, are further complicated since a beam electron interacts with a forcing field on the circuit for its entire trip through the device. We choose the simpler device, an idealized broadband klystron model, to study harmonic and intermodulation distortions in the multifrequency beam-wave system. The beam dynamics are modeled by nonlinear fluid equations, and the question of how the beam propagates general (multitonal) input conditions is addressed. Although the question has been considered before in some generality, we simplify the beam model and consider specifically multitonal excitation as would be used in a communications application
Design techniques for sigma-delta modulators from communications are applied and adapted to impro... more Design techniques for sigma-delta modulators from communications are applied and adapted to improve the spectral characteristics of high frequency power electronic applications. A high frequency power electronic circuit can be regarded as a quantizer in an interpolative Σ∆ modulator. We review one dimensional sigma-delta modulators and then generalize to the hexagonal sigma-delta modulators that are appropriate to three-phase converters. A
IEEE Transactions on Power Systems, vol. 28, pp. 3410-3419, Aug 2013
Branching processes can be applied to simulated cascading data to describe the statistics of the ... more Branching processes can be applied to simulated cascading data to describe the statistics of the cascades and quickly predict the distribution of blackout sizes. We improve the procedures for discretizing load shed data so that a Galton-Watson branching process may be applied. The branching process parameters such as average propagation are estimated from simulated cascades and the branching process is then used to estimate the distribution of blackout size. We test the estimated distributions with line outage and load shed data generated by the improved OPA and AC OPA cascading simulations on the IEEE 118-bus system and the Northeast Power Grid of China.
The authors describe two bifurcation instabilities of a thyristor controlled reactor (TCR) circui... more The authors describe two bifurcation instabilities of a thyristor controlled reactor (TCR) circuit in which switching times suddenly change and system stability is lost. The instabilities are unexpected because they are quite different from what might be expected from conventional theory in that they occur without the usual indications such as eigenvalues of a Jacobian matrix crossing the unit circle.
ICOPS 2000. IEEE Conference Record - Abstracts. 27th IEEE International Conference on Plasma Science (Cat. No.00CH37087), 2000
Summary form only given. Due to the increasing bandwidth of Traveling Wave Tube Amplifiers (TWTAs... more Summary form only given. Due to the increasing bandwidth of Traveling Wave Tube Amplifiers (TWTAs), broadband klystrons, and the possibility of electron-beam modulation using Field Emitter Arrays (FEAs), there has been a resurgence of interest in understanding the electron beam-wave interaction when the beam and wave initially have multifrequency content. In the case of the klystron, this corresponds to understanding how the electron beam propagates a multitonal velocity or density disturbance. In a distributed interaction device like the TWTA the beam dynamics, and hence radiation dynamics, are further complicated since a beam electron interacts with a forcing field on the circuit for its entire trip through the device. We choose the simpler device, an idealized broadband klystron model, to study harmonic and intermodulation distortions in the multifrequency beam-wave system. The beam dynamics are modeled by nonlinear fluid equations, and the question of how the beam propagates general (multitonal) input conditions is addressed. Although the question has been considered before in some generality, we simplify the beam model and consider specifically multitonal excitation as would be used in a communications application
Design techniques for sigma-delta modulators from communications are applied and adapted to impro... more Design techniques for sigma-delta modulators from communications are applied and adapted to improve the spectral characteristics of high frequency power electronic applications. A high frequency power electronic circuit can be regarded as a quantizer in an interpolative Σ∆ modulator. We review one dimensional sigma-delta modulators and then generalize to the hexagonal sigma-delta modulators that are appropriate to three-phase converters. A
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Papers by Ian Dobson