17,279 research outputs found
Modal Analysis of Grid Connected Doubly-Fed Induction Generators
This paper presents the modal analysis of a gridconnected doubly fed induction generator (DFIG). The change in modal properties for different system parameters, operating points, and grid strengths are computed and observed. The results offer a better understanding of theDFIG intrinsic dynamics,which can also be useful for control design and model justification. Index Terms—Doubly fed induction generator, eigenvalue analysis, nonlinear dynamic model, small-signal stability.Published versio
How the global structure of protein interaction networks evolves
Two processes can influence the evolution of protein interaction networks:
addition and elimination of interactions between proteins, and gene
duplications increasing the number of proteins and interactions. The rates of
these processes can be estimated from available Saccharomyces cerevisiae genome
data and are sufficiently high to affect network structure on short time
scales. For instance, more than 100 interactions may be added to the yeast
network every million years, a substantial fraction of which adds previously
unconnected proteins to the network. Highly connected proteins show a greater
rate of interaction turnover than proteins with few interactions. From these
observations one can explain ? without natural selection on global network
structure ? the evolutionary sustenance of the most prominent network feature,
the distribution of the frequency P(d) of proteins with d neighbors, which is a
broad-tailed distribution. This distribution is independent of the experimental
approach providing nformation on network structure
Partonic Effects in Heavy Ion Collisions at RHIC
Effects of partonic interactions in heavy ion collisions at RHIC are studied
in a multiphase transport model (AMPT) that includes both initial partonic and
final hadronic interactions.It is found that a large parton scattering cross
section is needed to understand the measured elliptic flow of pions and
two-pion correlation function.Comment: 10 pages, 5 figures, Workshop on Quark and Hadron Dynamics, Budapest,
Hungary, March 3-7, 200
The adequacy of the present practice in dynamic aggregated modelling of wind farm systems
Large offshore wind farms are usually composed of several hundred individual wind turbines, each turbine having its own complex set of dynamics. The analysis of the dynamic interaction between wind turbine generators (WTG), interconnecting ac cables, and voltage source converter (VSC) based High Voltage DC (HVDC) system is difficult because of the complexity and the scale of the entire system. The detailed modelling and modal analysis of a representative wind farm system reveal the presence of several critical resonant modes within the system. Several of these modes have frequencies close to harmonics of the power system frequency with poor damping. From a computational perspective the aggregation of the physical model is necessary in order to reduce the degree of complexity to a practical level. This paper focuses on the present practices of the aggregation of the WTGs and the collection system, and their influence on the damping and frequency characteristics of the critical oscillatory modes. The effect of aggregation on the critical modes are discussed using modal analysis and dynamic simulation. The adequacy of aggregation method is discussed
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