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Publications

2007

Hierarchical frequency control scheme for islanded multi-microgrids operation

Authors
Gil, NJ; Lopes, JAP;

Publication
2007 IEEE LAUSANNE POWERTECH, VOLS 1-5

Abstract
This paper presents a new hierarchical approach to deal with the problem of controlling frequency and active power generation of a medium voltage network comprising several microgrids and distributed generation sources operated in islanded mode. The hierarchical approach described here should be cost effective and capable of dealing with large numbers of distributed microsources and performing tasks related to coordinated frequency control.

2007

A fuzzy dynamic programming approach for evaluation of expansion distribution cost in uncertainty environments

Authors
Schweickardt, GA; Miranda, V;

Publication
LATIN AMERICAN APPLIED RESEARCH

Abstract
This paper presents a new Fuzzy Dynamic Programming model that calculates the optimum solution of problems with uncertainties in data defined by fuzzy sets. The result includes the determination of an Intrinsic Risk Threshold of the solution. Extrinsic Risk Thresholds may also be set by a Decision Maker, in order to obtain more robust solutions. The technique is applied to the calculation of Distribution System expansion costs to serve the objectives of a Regulatory Authority (Regulator) in fixing levels of efficiency, targets and penalties to a regulated market.

2007

Image segmentation using region merging combined with a multi-class spectral method

Authors
Monteiro, FC; Campilho, A;

Publication
Proceedings of IAPR Conference on Machine Vision Applications, MVA 2007

Abstract
In this paper we propose an image segmentation algorithm that combines region merging with spectral-based techniques. An initial partitioning of the image into primitive regions is produced by applying a region merging approach which produces a chunk graph that takes in attention the image gradient magnitude. This initial partition is the input to a computationally efficient region segmentation process that produces the final segmentation. The latter process uses a multi-class partition that minimizes the normalized cut value for the region graph. We have efficiently applied the proposed approach with good visual and objective segmentation quality results.

2007

Learning paraphrases from WNS corpora

Authors
Cordeiro, J; Dias, G; Brazdil, P;

Publication
Proceedings of the Twentieth International Florida Artificial Intelligence Research Society Conference, FLAIRS 2007

Abstract
Paraphrase detection can be seen as the task of aligning sentences that convey the same information but yet are written in different forms. Such resources are important to automatically learn text-to-text rewriting rules. In this paper, we present a new metric for unsupervised detection of paraphrases and apply it in the context of clustering of paraphrases. An exhaustive evaluation is conducted over a set of standard paraphrase corpora and real-world web news stories (WNS) corpora. The results are promising as they outperform state-of-the-art measures developed for similar tasks. Copyright

2007

A Metric for Paraphrase Detection

Authors
Cordeiro, J; Dias, G; Brazdil, P;

Publication
2007 International Multi-Conference on Computing in the Global Information Technology (ICCGI'07)

Abstract

2007

Use of simulated an-healing for optimizing capacity and location of STATCOM in grids with large scale wind generation

Authors
Marques, PJF; Lopes, JAP;

Publication
POWERENG2007: INTERNATIONAL CONFERENCE ON POWER ENGINEERING - ENERGY AND ELECTRICAL DRIVES PROCEEDINGS, VOLS 1 & 2

Abstract
This paper describes a new approach for the dimensioning and location of STATCOMs in Grids with large scale integration of wind energy. The approach developed uses as criterion the reduction of the loss of wind generation due to the operation of under voltage relays following a grid disturbance. The methodology adopted exploits Simulated Annealing in the identification of the problem solution. The approach has been tested in Iberian electrical system and results obtained show also its effectiveness regarding the global dynamic behaviour of the system.

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