151 research outputs found
Stability and Control of Power Systems using Vector Lyapunov Functions and Sum-of-Squares Methods
Recently sum-of-squares (SOS) based methods have been used for the stability
analysis and control synthesis of polynomial dynamical systems. This analysis
framework was also extended to non-polynomial dynamical systems, including
power systems, using an algebraic reformulation technique that recasts the
system's dynamics into a set of polynomial differential algebraic equations.
Nevertheless, for large scale dynamical systems this method becomes
inapplicable due to its computational complexity. For this reason we develop a
subsystem based stability analysis approach using vector Lyapunov functions and
introduce a parallel and scalable algorithm to infer the stability of the
interconnected system with the help of the subsystem Lyapunov functions.
Furthermore, we design adaptive and distributed control laws that guarantee
asymptotic stability under a given external disturbance. Finally, we apply this
algorithm for the stability analysis and control synthesis of a network
preserving power system.Comment: to appear at the 14th annual European Control Conferenc
Stochastic Model for Power Grid Dynamics
We introduce a stochastic model that describes the quasi-static dynamics of
an electric transmission network under perturbations introduced by random load
fluctuations, random removing of system components from service, random repair
times for the failed components, and random response times to implement optimal
system corrections for removing line overloads in a damaged or stressed
transmission network. We use a linear approximation to the network flow
equations and apply linear programming techniques that optimize the dispatching
of generators and loads in order to eliminate the network overloads associated
with a damaged system. We also provide a simple model for the operator's
response to various contingency events that is not always optimal due to either
failure of the state estimation system or due to the incorrect subjective
assessment of the severity associated with these events. This further allows us
to use a game theoretic framework for casting the optimization of the
operator's response into the choice of the optimal strategy which minimizes the
operating cost. We use a simple strategy space which is the degree of tolerance
to line overloads and which is an automatic control (optimization) parameter
that can be adjusted to trade off automatic load shed without propagating
cascades versus reduced load shed and an increased risk of propagating
cascades. The tolerance parameter is chosen to describes a smooth transition
from a risk averse to a risk taken strategy...Comment: framework for a system-level analysis of the power grid from the
viewpoint of complex network
BUILDING THE NEW DIMENSION OF STRATEGIC CORPORATE SOCIAL RESPONSIBILITY: ENVIRONMENTAL LEADERSHIP
The paper aims to emphasize the role of environmental leadership as main option for combining the Corporate Social Responsibility (CSR) policy with the business goals and targets in order to satisfy both shareholders’ interests and social interests, in terms of profit, productivity and social awareness. Under these circumstances, the paper describes the way environmental leadership is being built and introduced in the organizational culture of a company, regardless of its size, becoming a very efficient and effective philosophy of managing people and achieving performance targets. Nowadays.environmental leadership, corporate social responsibility, strategy, business performance
Study of population by domicile and residence. Natural movement and imbalances
The evolution of the Romanian population is one that has to attract interest, especially
from the point of view of the decrease in the birth rate, which will further determine the reduction
from year to year of the population, both resident and domicile in Romania. Against the background
of the increase of the death-birth rate, i.e. the ratio of deceased to newborn in favor of the deceased,
the age pyramid will be changed in the sense that, at the base, the younger generations will be
reduced to the middle and especially towards the peak of the pyramid being net contingents over
previous periods. In this context, we can speak with certainty about a phenomenon of aging of the
population, i.e., of increasing the number of older people on the background of the decrease of the
birth rate. In this article, the authors study the evolution of the population over time, presenting
tables and graphs that highlight this aging phenomenon. In summary, we can say that birth rates
are decreasing, mortality increases, marriage decreases, divorcement increases, and emigration of
a part of the population, especially from younger generations and with more special training.
Birthplaces are highlighted, in the context of the couples breaking up or not, in order to have an
image that the generation of young children does not have an immediate or long-lasting perspective.
There are many births outside marriages, especially in rural areas and less in urban areas. The age
at which the marriages are made is advanced, and on this complex background we come to the
conclusion of a certain aging process of the Romanian population. At the same time, we also
appreciate that the population resident or domiciled in Romania will also gradually decrease. There
are predictions that, in 2050, the population of Romania, if this trend of the main demographic
indicators is maintained, will reach about 17 million inhabitants
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