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Publicações

Publicações por CPES

2013

Smart grid as way to reinvent the power system

Autores
Antunes, AF; Pissarro, J; Jesus, H; de Almeida, A; Baptista, J;

Publicação
CIGRE 2013 Lisbon Symposium - Smarts Grids: Next Generation Grids for Energy Trends

Abstract
The smart grids represent a new and attracting challenge for various research areas. The inclusion of information technologies across the entire electrical grid creates new capacities, with impact on the environment, science and technology, economy and lifestyle. Creation of a smart grid provides utilities and their customers a significant improvement in power reliability and services. This paper presents an overview of smart grid technologies focusing on its characteristics, benefits and challenges. Moreover, this paper reviews the reliability impacts of the major smart grid resources such as renewables, demand response and storage. The main differences between a traditional grid and a smart grid, the trends in the evolution of power distribution systems and the highlights of smart grid segments and applications are also presented. Smart Grids represent one of the great challenges at the global level. Under the effect of political and societal pressure due to climate change and pollution concerns, and enabled by availability of new technologies, the electrical power systems are undergoing reconsideration. Including the technology of information in the whole electric grid creates new capabilities with strong impact in the environment, science and technology, but also in the economy and life in general. The term "smart grid" describes the evolution of the electrical grids and reflects a change of paradigm in the electric market organization and management. Some changes are already on the way to be implemented, such as a growth of the renewable fraction of the generating power, some other are envisioned, such as the fully flexible energy routing or the consumer driven distribution. From a global perspective, implementing smart grids at a large scale will definitely improve the services that supply electrical energy in the future. In recent years, electrical grids have been faced with an increasing concentration of distortion loads that generate distortion, causing both current and voltage harmonic distortions. The impact of these loads increases as their power approaches the power capacity of the grid.

2013

Probabilistic Description of Model Set Response in Neuromuscular Blockade

Autores
Rocha, C; Lemos, JM; Mendonça, T; Silva, ME;

Publicação
Advances in Systems Science - Proceedings of the International Conference on Systems Science 2013, ICSS 2013, Wroclaw, Poland, September 10-12, 2013

Abstract
This work addresses the problem of computing the time evolution of the probability density function (pdf) of the state in a nonlinear neuromuscular blockade (NMB) model, assuming that the source of uncertainty is the knowledge about one parameter. The NMB state is enlarged with the parameter, that verifies an equation given by its derivative being zero and has an initial condition described by a known pdf. By treating the resulting enlarged state-space model as a stochastic differential equation, the pdf of the state verifies a special case of the Fokker-Planck equation in which the second derivative terms vanish. This partial differential equation is solved with a numerical method based on Trotter’s formula for semigroup decomposition. The method is illustrated with results for a reduced complexity NMB model. A comparison of the predicted state pdf with clinical data for real patients is provided. © Springer International Publishing Switzerland 2014.

2013

A Nonlinear Continuous-Discrete Filter with Model Parameter Uncertainty and Application to Anesthesia

Autores
Lemos, JM; Rocha, C; Mendonca, TF; Silva, ME;

Publicação
2013 IEEE 52ND ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC)

Abstract
This paper addresses the problem of joint estimation of the state and parameters for a deterministic continuous time system, with discrete time observations, in which the parameter vector is constant but its value is not known, being a random variable with a known distribution. Along time, the uncertainty in the parameter induces uncertainty in the plant state. The joint probability density function (pdf) satisfies the Liouville partial differential equation that is a limit case of the Fokker-Planck equation for vanishing diffusion. The continuous-discrete filter proposed operates as follows: Between two consecutive output sampling time instants, the pdf is propagated by solving the Liouville equation for an augmented state and is then corrected by using the last observation and Bayes law. An application to state estimation of the neuromuscular blockade of patients subject to general anesthesia, where parameter uncertainty is due to inter-patient variability, is described.

2013

Modelling neuromuscular blockade: a stochastic approach based on clinical data

Autores
Rocha, C; Mendonca, T; Silva, ME;

Publicação
MATHEMATICAL AND COMPUTER MODELLING OF DYNAMICAL SYSTEMS

Abstract
During surgical interventions, a muscle relaxant drug is frequently administered with the objective of inducing muscle paralysis. Clinical environment and patient safety issues lead to a huge variety of situations that must be taken into account requiring intensive simulation studies. Hence, population models are crucial for research and development in this field.This work develops a stochastic population model for the neuromuscular blockade (NMB) (muscle paralysis) level induced by atracurium based on a deterministic individual model already proposed in the literature. To achieve this goal, a joint Lognormal distribution is considered for the patient-dependent parameters. This study is based on clinical data collected during general anaesthesia. The procedure developed enables to construct a reliable reference bank of parametrized models that not only reproduces the overall features of the NMB, but also the inter-individual variability characteristic of physiological signals. It turns out that this bank constitutes a fundamental tool to support research on identification and control algorithms and is suitable to be integrated in clinical decision support systems.

2013

Smart Grid Market Using Joint Energy and Ancillary Services Bids

Autores
Soares, T; Morais, H; Faria, P; Vale, Z;

Publicação
2013 IEEE GRENOBLE POWERTECH (POWERTECH)

Abstract
The power systems operation in the smart grid context increases significantly the complexity of their management. New approaches for ancillary services procurement are essential to ensure the operation of electric power systems with appropriate levels of stability, safety, quality, equity and competitiveness. These approaches should include market mechanisms which allow the participation of small and medium distributed energy resources players in a competitive market environment. In this paper, an energy and ancillary services joint market model used by an aggregator is proposed, considering bids of several types of distributed energy resources. In order to improve economic efficiency in the market, ancillary services cascading market mechanism is also considered in the model. The proposed model is included in MASCEM - a multi-agent system electricity market simulator. A case study considering a distribution network with high penetration of distributed energy resources is presented.

2013

Dispatch of Distributed Energy Resources to Provide Energy and Reserve in Smart Grids using a Particle Swarm Optimization Approach

Autores
Faria, P; Soares, T; Pinto, T; Sousa, TM; Soares, J; Vale, Z; Morais, H;

Publicação
2013 IEEE SYMPOSIUM ON COMPUTATIONAL INTELLIGENCE APPLICATIONS IN SMART GRID (CIASG)

Abstract
The smart grid concept is a key issue in the future power systems, namely at the distribution level, with deep concerns in the operation and planning of these systems. Several advantages and benefits for both technical and economic operation of the power system and of the electricity markets are recognized. The increasing integration of demand response and distributed generation resources, all of them mostly with small scale distributed characteristics, leads to the need of aggregating entities such as Virtual Power Players. The operation business models become more complex in the context of smart grid operation. Computational intelligence methods can be used to give a suitable solution for the resources scheduling problem considering the time constraints. This paper proposes a methodology for a joint dispatch of demand response and distributed generation to provide energy and reserve by a virtual power player that operates a distribution network. The optimal schedule minimizes the operation costs and it is obtained using a particle swarm optimization approach, which is compared with a deterministic approach used as reference methodology. The proposed method is applied to a 33-bus distribution network with 32 medium voltage consumers and 66 distributed generation units.

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