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Controlo do fluxo de potência em redes de transporte com reatores saturáveis supercondutores
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Esta dissertação tem como objetivo o estudo e análise da introdução de um reator de núcleo saturável com supercondutores numa linha de transporte de energia elétrica para controlo do fluxo de potência que percorre a mesma. O reator é um dispositivo de núcleo magnético, composto por uma coluna central e seis externas, que perfazem um total de três fases, para o caso trifásico. O enrolamento central é percorrido por corrente DC e os externos por AC, estando os últimos em série com a linha.
O controlo do fluxo de potência tem por objetivo evitar situações de sobrecarga nas linhas de transporte de energia elétrica, assim como, de desequilíbrio entre as mesmas. Com a introdução do reator de núcleo saturável existe a possibilidade de minimizar estes cenários, o que resulta em redes mais fiáveis.
São ensaiados dois reatores, em que um deles é monofásico e o outro trifásico, sendo o último ensaiado com um sistema de controlo de corrente. O sistema de controlo, através de cálculos, apresenta a corrente da linha e, consoante a corrente máxima admis-sível na linha este calcula o valor de indutância que os enrolamentos AC devem apresen-tar. Para o valor de indutância desejado é necessário calcular a corrente DC de ajuste a ser injetada por uma fonte externa.
De forma simplificada, pretende-se ajustar a corrente injetada no enrolamento DC do reator, de onde resulta uma alteração do valor de permeabilidade relativa do material, sendo esta não-linear. Os ajustes de corrente realizam-se entre as zonas linear e de satu-ração magnéticas do núcleo. Assim da variação da indutância nos enrolamentos AC re-sulta a alteração da reactância indutiva. Com o aumento ou diminuição da reatância do núcleo magnético resulta um aumento ou diminuição da impedância, respetivamente, o que, por sua vez, gera uma variação da queda de tensão e da potência na linha de trans-porte de energia elétrica. A inclusão de supercondutores tem como finalidade diminuir as perdas por efeito de Joule no circuito de controlo.
Dos ensaios realizados com o reator de núcleo saturável, trifásico, e o sistema de controlo alcança-se o objetivo de implementar um sistema que permite calcular a corrente que percorre a linha e, simultaneamente, gera uma tensão, a injetar na entrada da fonte externa, que corresponde a uma corrente DC a injetar na bobina supercondutora.
In this thesis is studied and analyzed the coupling of a saturable reactor, with supercon-ductors, in an electric transmission system, in which is pretended to control the power flow. A saturable reactor is a magnetic core device, that has one central column and six externals, for the case of a three-phase device. In the central winding flows DC current, on the other hand the external windings are traversed by AC current. By controlling the power flow is possible to avoid overload situations in the trans-mission lines and unbalances between them. With the coupling of the saturable reactor situations like this can be managed and avoided, resulting in more reliable transmission systems. There are two types of reactors to be tested, one of them is a single-phase and the second one is a three-phase, which is tested with a control system to conclude about the controllable current range. The control system, through calculations, presents the line current, and according to the maximum allowable current it can calculate the inductance that must exist in the AC windings. To obtain a desirable value of inductance there as to be the injection of a DC current, in the superconductive coil, by an external DC source. In this way, it is desired to adjust the current that is injected in the DC windings of the saturable reactor, this results in a change of the relative permeability of the core, which is non-linear. The current must be adjusted between the linear and magnetic saturation regions of the core. By doing this it is possible to vary the AC windings inductance, in which results the change in the inductive reactance. The decrease or increase in the in-ductive reactance of the magnetic core results in a decrease or increase of the line imped-ance, respectively, which varies the voltage drop and the power flow level in the electric transmission system. The use of a superconductive material, in the DC windings, as the advantage to decrease the power losses. From the laboratory tests with the three-phase saturable core reactor and the control system it is achieved the main objective of implementing a system that measures the cur-rent that flows through the line and, simultaneously, generates a voltage, to be injected in the external DC source 25 pin Analog Control connectors input, that corresponds to a DC current to be injected in the superconductive coil.
In this thesis is studied and analyzed the coupling of a saturable reactor, with supercon-ductors, in an electric transmission system, in which is pretended to control the power flow. A saturable reactor is a magnetic core device, that has one central column and six externals, for the case of a three-phase device. In the central winding flows DC current, on the other hand the external windings are traversed by AC current. By controlling the power flow is possible to avoid overload situations in the trans-mission lines and unbalances between them. With the coupling of the saturable reactor situations like this can be managed and avoided, resulting in more reliable transmission systems. There are two types of reactors to be tested, one of them is a single-phase and the second one is a three-phase, which is tested with a control system to conclude about the controllable current range. The control system, through calculations, presents the line current, and according to the maximum allowable current it can calculate the inductance that must exist in the AC windings. To obtain a desirable value of inductance there as to be the injection of a DC current, in the superconductive coil, by an external DC source. In this way, it is desired to adjust the current that is injected in the DC windings of the saturable reactor, this results in a change of the relative permeability of the core, which is non-linear. The current must be adjusted between the linear and magnetic saturation regions of the core. By doing this it is possible to vary the AC windings inductance, in which results the change in the inductive reactance. The decrease or increase in the in-ductive reactance of the magnetic core results in a decrease or increase of the line imped-ance, respectively, which varies the voltage drop and the power flow level in the electric transmission system. The use of a superconductive material, in the DC windings, as the advantage to decrease the power losses. From the laboratory tests with the three-phase saturable core reactor and the control system it is achieved the main objective of implementing a system that measures the cur-rent that flows through the line and, simultaneously, generates a voltage, to be injected in the external DC source 25 pin Analog Control connectors input, that corresponds to a DC current to be injected in the superconductive coil.
Descrição
Palavras-chave
Fluxo de potência Reator de núcleo saturável (RNS) Supercondutor Sistema de Controlo Sistema de monitorização