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Publications

Publications by CPES

2011

A computer tool for harmonic distortion prediction in low voltage power systems

Authors
Baptista, J; Moura, AM;

Publication
Proceeding of the International Conference on Electrical Power Quality and Utilisation, EPQU

Abstract
Power-Quality (PQ) is a crucial competitive and developing factor to all economic areas. The economic impact resulting from a bad PQ will be drastic to all consumers. Computers, uninterruptible power supplies (UPS), commuted power sources and fluorescent lamps/tubes are examples of nonlinear loads that have for main drawback the consumption of non-sinusoidal current. This paper presents a useful computer tool that can simulate and predict the behavior of non-linear loads and LV power systems with main focus on residential electrical grids. The paper also reviews some of the basic concepts and techniques related with power quality parameters and how they can be computed and presented in the simulation tool. The tool has an easy-to-use, friendly interface, and can be used as a tool to teach design techniques or as a laboratory to study the applicability of methods to real situations. The students can do simulations with their own data on Microsoft™ Windows® based platforms. © 2011 IEEE.

2011

Double permanent magnet vibration power generator for smart hip prosthesis

Authors
Morais, R; Silva, NM; Santos, PM; Frias, CM; Ferreira, JAF; Ramos, AM; Simoes, JAO; Baptista, JMR; Reis, MC;

Publication
SENSORS AND ACTUATORS A-PHYSICAL

Abstract
Ever since the first studies about biomedical implantable devices, the problem of how to energize them has stood out as both important and notoriously difficult to solve. In order to extend the lifetime of implants, it is imperative to develop power generators that are autonomous, safe and maintenance-free. Energy harvesting is a natural way of meeting these requirements. First, the energy source is theoretically everlasting, a fact that helps to guarantee the autonomy. Second, the energy is obtained from the environment of the application itself, contributing to its safety. Finally, a properly designed energy harvesting system is very unlikely to ever require maintenance. This paper follows this line and describes an electromagnetic power transducer that harvests electrical energy from the human gait and stores it. An efficient power management module uses the stored energy to energize the telemetric system of a smart hip prosthesis implant, enabling the early detection of loosening, the target application of this work. The system is able to extract a total 1912.5 mu J of usable energy under normal walking conditions.

2011

A Low-Cost System to Detect Bunches of Grapes in Natural Environment from Color Images

Authors
Reis, MJCS; Morais, R; Pereira, C; Contente, O; Bacelar, M; Soares, S; Valente, A; Baptista, J; Ferreira, PJSG; Bulas Cruz, J;

Publication
ADVANCED CONCEPTS FOR INTELLIGENT VISION SYSTEMS

Abstract
Despite the benefits of precision agriculture and precision viticulture production systems, its adoption rate in the Portuguese Douro Demarcated Region remains low. One of the most demanding tasks in wine making is harvesting. Even for humans, the environment makes grape detection difficult, especially when the grapes and leaves have a similar color, which is generally the case for white grapes. In this paper, we propose a system for the detection and location, in the natural environment, of bunches of grapes in color images. The system is also able to distinguish between white and red grapes, at the same time, it calculates the location of the bunch stem. The proposed system achieved 97% and 91% correct classifications for red and white grapes, respectively.

2011

Automatic Detection of White Grapes in Natural Environment Using Image Processing

Authors
Reis, MC; Morais, R; Pereira, C; Soares, S; Valente, A; Baptista, J; Ferreira, PJSG; Cruz, JB;

Publication
SOFT COMPUTING MODELS IN INDUSTRIAL AND ENVIRONMENTAL APPLICATIONS, 6TH INTERNATIONAL CONFERENCE SOCO 2011

Abstract
The rate of adoption of Precision Agriculture and Precision Viticulture production systems in the Douro Demarcated Region remains low. We believe that one way to raise it is to address challenging real-world problems whose solution offers a clear benefit to the viticulturist. For example, one of the most demanding tasks in wine making is harvesting. Even for humans, the detection of grapes in their natural environment is not always easy. White grapes are particularly difficult to detect, since their color is similar to that of the leafs. Here we present a low cost system for the detection of white grapes in natural environment color images. The system also calculates the probable location of the bunch stem and achieves 91% of correct classifications.

2011

Energy and ancillary services joint market simulation

Authors
Soares, T; Morais, H; Canizes, B; Vale, Z;

Publication
2011 8th International Conference on the European Energy Market, EEM 11

Abstract
In order to develop a flexible simulator, a variety of models for Ancillary Services (AS) negotiation has been implemented in MASCEM a multi-agent system competitive electricity markets simulator. In some of these models, the energy and the AS are addressed simultaneously while in other models they are addressed separately. This paper presents an energy and ancillary services joint market simulation. This paper proposes a deterministic approach for solving the energy and ancillary services joint market. A case study based on the dispatch of Regulation Down, Regulation Up, Spinning Reserve, and Non-Spinning Reserve services is used to demonstrate that the use of the developed methodology is suitable for solving this kind of optimization problem. The presented case study is based on CAISO real AS market data considers fifteen bids. © 2011 IEEE.

2011

Multistage transmission expansion planning alleviating the level of transmission congestion

Authors
Dehghan, S; Kazemi, A; Neyestani, N;

Publication
2011 IEEE PES Trondheim PowerTech: The Power of Technology for a Sustainable Society, POWERTECH 2011

Abstract
This paper presents a multistage transmission expansion planning (TEP) which alleviates the level of transmission congestion during the planning horizon. Due to the combinatorial nature of the proposed TEP model, a Benders decomposition approach intertwined with a manipulated disjunctive model is applied to decompose the original TEP problem into a master problem and two sub-problems standing for system security and optimal operation. The security sub-problem applying the N-1 contingency criterion to assess the transmission system security. Besides, the optimal operation sub-problem makes it possible for the proposed TEP model to fulfill the optimal operation as well as to calculate the difference between system lacational marginal prices (LMPs) for all buses. Also, this model appends a specific term into the TEP objective function as the congestion level (CL) reflecting the degree of market competitiveness. Therefore, the proposed TEP model minimizes the total costs comprising the investment cost of candidate transmission lines as well as the level of transmission congestion. The proposed approach is applied to the northeastern area of the Iranian power grid. © 2011 IEEE.

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