Browsing by Author "Carvalho, Adriano"
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- Analysis and NN-based control of doubly fed induction generator in wind power generationPublication . Soares, Orlando; Gonçalves, Henrique; Martins, António A.; Carvalho, AdrianoWith the increasing size of wind power generation it is required to perform power system stability analysis that uses dynamic wind generator models. In this paper are presented all the wind power system components, including the turbine, the generator, the power electronic converter and controllers. The aim is to study the Doubly Fed Induction Generator (DFIG) operation and its connection to the power system, either during normal operation or during transient grid fault events. Two different control system design technologies are present, the first is performed by standard PI controllers and the second is based on artificial neural networks
- Analysis and NN-based control of doubly fed induction generator in wind power generationPublication . Soares, Orlando; Gonçalves, Henrique; Martins, António A.; Carvalho, AdrianoWith the increasing size of wind power generation it is required to perform power system stability analysis that uses dynamic wind generator models. In this paper are presented all the wind power system components, including the turbine, the generator, the power electronic converter and controllers. The aim is to study the Doubly Fed Induction Generator (DFIG) operation and its connection to the power system, either during normal operation or during transient grid fault events. Two different control system design technologies are present, the first is performed by standard PI controllers and the second is based on artificial neural networks.
- Assessment of PROFIBUS networks using a fault injection frameworkPublication . Carvalho, José Augusto; Carvalho, Adriano; Portugal, PauloIndustrial control systems architectures have been evolving to the decentralization of control tasks. This evolution associated with the time-critical nature of these tasks, increases the dependability requirements for one of their most critical components: the communica¬tion system. Therefore, this is an important aspect on the control system design which must be properly evaluated. In this paper the dependability of a PROFIBUS net-work is assessed. By using of a fault injection framework the network operation is disturbed with fault scenarios which are representative of industrial environments. From these experiments, the stability of the PROFIBUS logical ring is analyzed, the main outages causes are identified and their probabilities are obtained.
- Avaliação da orientação das fibras em BEDRF através de técnicas não destrutivasPublication . Azevedo, Diogo M.M.; Ribeiro, Filipe; Carvalho, Adriano; Rio, João; Nunes, SandraO presente artigo apresenta alguns resultados iniciais do projecto Betofibra – “Betões de elevado desempenho reforçado com fibras (BEDRF) em soluções inovadoras: concepção, caracterização e controlo de qualidade”. Foram realizados vários ensaios por métodos não destrutivos (NDT) para avaliar a distribuição e orientação das fibras numa laje de BEDRF. Foram aplicadas as técnicas dos ultra-sons, resistividade eléctrica e indutância elétrica e foi avaliado o desempenho de cada ensaio por si, assim como o seu desempenho relativamente aos restantes. Os resultados indicam preliminarmente que os três métodos de ensaio se mostraram sensíveis à distribuição e orientação das fibras com destaque para a indutância elétrica.
- Dependability validation techniques for electronic systemsPublication . Portugal, Paulo; Carvalho, José Augusto; Carvalho, AdrianoDependability has become an essential parameter on system design. The fulfillment of the system function, either in mission oriented or in continuous operation, requires knowledge about all possible failure modes. If a fault occurrence causes a mis-operation it should be approached a design for a dependable system. Some issues should be performed both at system design and development stages, in order to build a robust system, by evaluating correctly failure conditions and guaranteeing the fulfillment of the system function. The main one is the validation process as well as it conditions the modelling methods associated to and the techniques to be adopted. This paper presents an approach for analysis of validation techniques for electronic systems. The analysis points out two directions, verification techniques needed to support the design at different phases and fault forecasting techniques to assess systems behavior for modelling faults activation and occurrence.
- Experimental analysis of outage times for PROFIBUS networksPublication . Carvalho, José Augusto; Carvalho, Adriano; Portugal, PauloDistributed control systems operation strongly depends on the communication system performance. Therefore, their analysis becomes an important aspect to be considered, particularly in situations where communications have real-time constrains and the network operates on faulty environments. In this paper the behavior of PROFIBUS network in the pres-ence of faults is analyzed. This analysis is performed in an expe-rimental base supported by a real network. The network opera-tion is disturbed through a set of fault injection experiments from which performance metrics related with PROFIBUS out-age times are evaluated.
- Factory automation using OSI technologies: process automation in a transformers manufacturing plantPublication . Tovar, Eduardo; Oliveira, José Luís; Alves, Mário; Azevedo, Rui; Carvalho, Adriano; Sousa, Mário; Portugal, Paulo; Carvalho, José AugustoThis paper presents the work carried out in order to improve one of the areas of a factory plant, integrating it within the factory using different communication standards. The implementation described satisfies a set of data flow requirements and claims to be an example of different vendors and technologies integration. Distribution transformers have always been dried within ovens heated for the effect. This drying process has several drawbacks: a low efficiency dependence on the transformer volume and requiring a long time to complete. The new approach, presented in this paper, eliminates all those constraints.
- A framework for dependability evaluation of PROFIBUS networksPublication . Carvalho, José Augusto; Carvalho, Adriano; Portugal, PauloFieldbus networks have been assuming a high acceptance in the industrial environment, replacing the old centralized control architectures. Due to time critical nature of the tasks involved in these environments, the fulfillment of dependability attributes is usually required. Therefore the dependability is an important parameter on system design, which should be evaluated. Several factors can affect system dependability. The environmental ones are the most common and due to the particularity of the industrial environment this susceptibility is increased. In this paper it is proposed a framework based on fault injection techniques, supported by a hardware platform which emulates a fault set, representative of industrial environment scenarios, intending to disturb data communications on a PROFIBUS network. From these fault injection experiments, relevant data is gathered and a further analysis is carried out to evaluate dependability attributes.
- A modular cell controller architecture for a flexible manufacturing systemPublication . Carvalho, José Augusto; Carvalho, AdrianoThe need to optimize manufacturing systems operation has originated continuous effort in the developmeut of control system architectures. These have been freed from original rigid centralized structures evolving in such a way that attribute more autonomy to each control subsystem. The subsystems have then become specialized in the different tasks needed to control each manufacturing process. In the present work, an architecture for a cdl controller, composed of modules with a significant degree of autonomy, is presented.
- Neural networks based power flow control of the doubly fed induction generatorPublication . Soares, Orlando; Gonçalves, Henrique; Martins, António A.; Carvalho, AdrianoThis paper describes the models of wind power system, such as the turbine, the generator, the power electronics convertrs and the controllers,with the aim to control the generation of wind power in order to miximize the power generated with the lowest possible impact in the voltage and the frequency of the grid during normal operation and the under occurrency of faults. the present work considers a wind power system equipped with the Doubly Fed Induction Generator (DFIG) and a converter connected between the rotor and the grid. This system allows independent control of active and reactive power using neural networks based controllers.