Decomposition-aggregation stability analysis

This report presents the development and description of the decomposition aggregation approach to stability investigations of high dimension mathematical models of dynamic systems. The high dimension vector differential equation describing a large dynamic system is decomposed into a number of lower dimension vector differential equations which represent interconnected subsystems. Then a method is described by which the stability properties of each subsystem are aggregated into a single vector Liapunov function, representing the aggregate system model, consisting of subsystem Liapunov functions as components. A linear vector differential inequality is then formed in terms of the vector Liapunov function. The matrix of the model, which reflects the stability properties of the subsystems and the nature of their interconnections, is analyzed to conclude over-all system stability characteristics. The technique is applied in detail to investigate the stability characteristics of a dynamic model of a hypothetical spinning Skylab

The effect of inrush transients on pv inverter's grid impedance measurement based on inter-harmonic injection

This paper addresses a cause for false tripping of photovoltaic inverters with antiislanding protection based on impedance measurement with inter-harmonic injection. Earlier discussions about tripping problems happening when several devices are doing the measurement at the same time are supplemented with a problem caused by inrush transients of nearby devices. A series of experiments was conducted in the Power Quality laboratory of the TU/e, on a PV inverter which complies with the DIN VDE 0126 standard. Impedance measurement was done in parallel with the inverter and measurement results are presented. A criterion for false tripping caused by transients is explored. Also, influences of network impedance and grid harmonic pollution on false tripping were analyzed. In the end, some signal processing techniques are proposed to avoid this problem

KINEMATIC ANALYSIS OF SOME BACKWARD ACROBATIC JUMPS

The aim of our investigation was to determine kinematic parameters of some acrobatic jumps backward, related to the difficulty categories in the current men's FIG Code of points. Ten male gymnasts performed ten different acrobatic jumps backward during the European championship in 1996 in Koebenhaven (Denmark). The analyzed elements were stretched salto backward, stretched salto backward with 1/1 turn, stretched salto backward with 3/2 turn, stretched salto backward with 2/1 turn, double salto backward tucked, double salto backward tucked with 1/1 turn, double salto backward tucked with 2/1 turn, double salto backward stretched, double salto backward stretched with 1/1 turn and triple salto backward tucked. According to the results we can not define the difficulty categories, but the data are quite informative for further investigations, comparison with other similar types of sports and also for coaches for methodic purposes

Modelling, analyses and design of switching converters

A state-space averaging method for modelling switching dc-to-dc converters for both continuous and discontinuous conduction mode is developed. In each case the starting point is the unified state-space representation, and the end result is a complete linear circuit model, for each conduction mode, which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small-signal). While the method is generally applicable to any switching converter, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model. The insights that emerge from the general state-space modelling approach lead to the design of new converter topologies through the study of generic properties of the cascade connection of basic buck and boost converters

Magnetic regulator modeling

A method of providing regulation in a resonant power supply uses a device called a magnetic regulator which resembles an ordinary AC transformer. Through the use of additional control windings, the conversion ratio of the magnetic regulator can be electronically varied, thus achieving control. A circuit model for the magnetic regulator is derived and is shown to contain a current-controlled leakage inductance. Measurements made on an experimental device verify the model. Two additional structures are described

Momentum average approximation for models with electron-phonon coupling dependent on the phonon momentum

We generalize the momentum average (MA) approximation to study the properties of models with momentum-dependent electron-phonon coupling. As in the case of the application of the original MA to the Holstein model, the results are analytical, numerically trivial to evaluate, exact for both zero bandwidth and for zero electron-phonon coupling, and are accurate everywhere in parameter space. Comparison with available numerical data confirms this accuracy. We then show that further improvements can be obtained based on variational considerations, using the one-dimensional breathing-mode Hamiltonian as a specific example. For example, by using this variational MA, we obtain ground state energies within at most 0.3% error of the numerical data.Comment: 15 pages, 10 figure