João Murta Pina

Inductive superconducting fault current limiters have already demonstrated their technical viability in electrical networks. Its architecture and robustness make them potentially adequate for distribution networks, and this type of devices is considered as an enabling technology for the advent of embedded generation with renewable energy sources. In order to promote the growth and maturity of these superconducting technologies, fast design tools must be developed, allowing simulating devices with different materials in grids with diverse characteristics. This work presents advances in the development of such tool, which, at present stage, is an effective alternative to software simulations by finite elements methods, reducing dramatically computation time. The algorithms are now compared with experimental results from a laboratory scale prototype, showing the need to refine them.

The invention consists in a polyphase motor and operating system thereof that allows obtaining an arbitrary relation of the number of magnetic poles without mechanical commutations within the stator. The number of slots of the latter is ideally given by the least common multiple between the required pole relations. The stator is polyphasic, and the rotor is that of an induction or hysteresis motor. The motor is designed for applications where a large range of operation requiring maximum yield and?or smooth speed?torque (or force, depending on whether the motor is rotary or linear) transitions. This is the case of electric vehicle traction. The operating system receives control references via a controller that compares them with the signals read by the sensor(s). The control action feeds a polyphase inverter for generating the voltages or currents that feed the stator. The speed, torque, or position values are measured in the rotor.

An architecture for the operation of a recuperative-type glass furnace is introduced in this paper. It is based on a hierarchical scheme, with two main parts: process optimisation and process modelling. Process optimisation is carried out by an expert controller, and uses genetic algorithms to solve a multiobjective optimisation problem. Process modelling is performed by a learning system, based on a fuzzy learning-by-examples algorithm. Results of real and simulated experiments with the glass manufacturing process are presented.

This paper presents the design of a test rig for an all HTS linear synchronous motor. Although this motor showed to have several unattractive characteristics, its design raised a number of problems which must be considered in future HTS machines design. HTS electromagnetic properties led to the development of new paradigms in electrical machines and power systems, as e. g. in some cases iron removal and consequent assembly of lighter devices. This is due to superconductor's ability to carry high currents with minimum losses and consequent generation in the surrounding air of flux densities much higher than the allowed by ferromagnetic saturation. However, severe restrictions in HTS power devices design that goes further beyond cryogenic considerations must be accounted in. This is usually the case when BSCCO tapes are used as conductors. Its bending limitations and the presence of flux components perpendicular to tape surface, due to the absence of iron, have to be considered for it may turn some possible applications not so attractive or even practically unfeasible. An all HTS linear synchronous motor built by BSCCO tapes as armature conductors and two trapped-flux YBCO bulks in the mover was constructed and thrust force measurements are starting to be performed. Although the device presents severe restrictions due to the exposed and other reasons, it allowed systematising its design. A pulsed-field magnetiser to generate opposite fluxes for both YBCO bulks is also detailed. Thrust force numerical predictions were already derived and presented.

Amongst applications of high temperature superconductors, fault current limiters are foreseen as one of the most promising in power systems. Several topologies have been developed in the last years, taking advantage of different superconductors? properties. Increasing distributed generation (DG) penetration, based on renewable energy, adds new short-circuit sources to electrical grids, which brings several energy quality and protection issues. Superconducting fault current limiters can obviate these problems, representing thus an enabling technology for DG penetration. In this paper current limiter topologies are presented, its operations principles, strengths and weaknesses, in the context of these DG grids. In the end, future trends are discussed.

One potential advantage of the application of superconducting materials in electrical machines is the possibility to build lighter and compact devices by removing iron. These machines find applications, e.g., in systems where cryogenics is already available, or in naturally cryogenic environments. The design of motors with high temperature superconductors (HTS) presents issues unconsidered in classical machines, besides considerations on cryogenics, such as HTS brittleness or mechanical restrictions. Moreover, HTS' electromagnetic properties also degrade due to flux density components, which arise if there is no iron to guide magnetic flux. Several aspects must thus be considered in the design stage, as applications may turn less attractive or even unfeasible. In this paper these issues are detailed, and a numerical methodology for the design of an all superconducting (without iron or conventional conductors) linear synchronous motor is presented.

A presente Dissertação consiste num estudo do comportamento competitivo de entidades, produtoras e comercializadoras de energia eléctrica, num período de tempo antes e após a entrada em vigor do Mercado Ibérico de Electricidade (MIBEL). Esse período de tempo engloba os meses entre Abril de 2007 e Abril de 2008, sendo que o MIBEL teve início a 1 de Julho de 2007. O estudo incide principalmente no grau de competitividade ou ausência da mesma, que as referidas entidades adoptaram após o começo do MIBEL. Para poder efectuar essa avaliação, recorre-se a uma abordagem baseada em variações conjecturais, que constituem um indicador desse grau de competitividade. Ou seja, as variações conjecturais representam a convicção que determinada empresa X tem face ao comportamento que outra empresa Y adoptará após uma acção efectuada pela empresa X. Por acção depreende-se, por exemplo, uma redução ou um aumento da quantidade de produção de uma empresa. Se o valor da variável conjectural for 0, as empresas encontram-se a concorrer à Cournot. Caso seja -1, as empresas encontram-se em concorrência perfeita. Por outro lado, se o valor da variação conjectural for superior a 0 pode existir uma situação de conluio entre as empresas. De modo a obter estes valores das variações conjecturais, utiliza-se e readapta-se um simulador de mercado diário, denominado SiMEC - Simulador do Mercado Eléctrico e do Carbono. Este simulador, que anteriormente simulava apenas períodos temporais precedentes ao MIBEL, foi reajustado de modo a incluir dados pós MIBEL. Finalmente, são então realizados gráficos comparativos e retiradas conclusões acerca do comportamento das entidades face a alterações na estrutura do mercado de electricidade.