59,572 research outputs found
Nonlinear Control of a DC MicroGrid for the Integration of Photovoltaic Panels
New connection constraints for the power network (Grid Codes) require more
flexible and reliable systems, with robust solutions to cope with uncertainties
and intermittence from renewable energy sources (renewables), such as
photovoltaic arrays. The interconnection of such renewables with storage
systems through a Direct Current (DC) MicroGrid can fulfill these requirements.
A "Plug and Play" approach based on the "System of Systems" philosophy using
distributed control methodologies is developed in the present work. This
approach allows to interconnect a number of elements to a DC MicroGrid as power
sources like photovoltaic arrays, storage systems in different time scales like
batteries and supercapacitors, and loads like electric vehicles and the main AC
grid. The proposed scheme can easily be scalable to a much larger number of
elements.Comment: arXiv admin note: text overlap with arXiv:1607.0848
Asynchronous Networks and Event Driven Dynamics
Real-world networks in technology, engineering and biology often exhibit
dynamics that cannot be adequately reproduced using network models given by
smooth dynamical systems and a fixed network topology. Asynchronous networks
give a theoretical and conceptual framework for the study of network dynamics
where nodes can evolve independently of one another, be constrained, stop, and
later restart, and where the interaction between different components of the
network may depend on time, state, and stochastic effects. This framework is
sufficiently general to encompass a wide range of applications ranging from
engineering to neuroscience. Typically, dynamics is piecewise smooth and there
are relationships with Filippov systems. In the first part of the paper, we
give examples of asynchronous networks, and describe the basic formalism and
structure. In the second part, we make the notion of a functional asynchronous
network rigorous, discuss the phenomenon of dynamical locks, and present a
foundational result on the spatiotemporal factorization of the dynamics for a
large class of functional asynchronous networks
On Delay-independent Stability of a class of Nonlinear Positive Time-delay Systems
We present a condition for delay-independent stability of a class of
nonlinear positive systems. This result applies to systems that are not
necessarily monotone and extends recent work on cooperative nonlinear systems.Comment: 9 page
Collective stability of networks of winner-take-all circuits
The neocortex has a remarkably uniform neuronal organization, suggesting that
common principles of processing are employed throughout its extent. In
particular, the patterns of connectivity observed in the superficial layers of
the visual cortex are consistent with the recurrent excitation and inhibitory
feedback required for cooperative-competitive circuits such as the soft
winner-take-all (WTA). WTA circuits offer interesting computational properties
such as selective amplification, signal restoration, and decision making. But,
these properties depend on the signal gain derived from positive feedback, and
so there is a critical trade-off between providing feedback strong enough to
support the sophisticated computations, while maintaining overall circuit
stability. We consider the question of how to reason about stability in very
large distributed networks of such circuits. We approach this problem by
approximating the regular cortical architecture as many interconnected
cooperative-competitive modules. We demonstrate that by properly understanding
the behavior of this small computational module, one can reason over the
stability and convergence of very large networks composed of these modules. We
obtain parameter ranges in which the WTA circuit operates in a high-gain
regime, is stable, and can be aggregated arbitrarily to form large stable
networks. We use nonlinear Contraction Theory to establish conditions for
stability in the fully nonlinear case, and verify these solutions using
numerical simulations. The derived bounds allow modes of operation in which the
WTA network is multi-stable and exhibits state-dependent persistent activities.
Our approach is sufficiently general to reason systematically about the
stability of any network, biological or technological, composed of networks of
small modules that express competition through shared inhibition.Comment: 7 Figure
Nonlinear Control of an AC-connected DC MicroGrid
New connection constraints for the power network (Grid Codes) require more
flexible and reliable systems, with robust solutions to cope with uncertainties
and intermittence from renewable energy sources (renewables), such as
photovoltaic arrays. A solution for interconnecting such renewables to the main
grid is to use storage systems and a Direct Current (DC) MicroGrid. A "Plug and
Play" approach based on the "System of Systems" philosophy using distributed
control methodologies is developed in the present work. This approach allows to
interconnect a number of elements to a DC MicroGrid as power sources like
photovoltaic arrays, storage systems in different time scales like batteries
and supercapacitors, and loads like electric vehicles and the main AC grid. The
proposed scheme can easily be scalable to a much larger number of elements.Comment: IEEE IECON 2016, the 42nd Annual Conference of IEEE Industrial
Electronics Society, October 24-27, 201
Futures Studies in the Interactive Society
This book consists of papers which were prepared within the framework of the research project (No. T 048539) entitled Futures Studies in the Interactive Society (project leader: Éva Hideg) and funded by the Hungarian Scientific Research Fund (OTKA) between 2005 and 2009. Some discuss the theoretical and methodological questions of futures studies and foresight; others present new approaches to or
procedures of certain questions which are very important and topical from the perspective of forecast and foresight practice. Each study was conducted in pursuit of improvement in futures fields
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