Browsing by Author "Scotta, Isabella Cristina"
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- Circuitos de proteção contra sobretensão para turbinas pico-hídricas e eólicas ligadas à rede elétrica através de inversores eletrónicosPublication . Scotta, Isabella Cristina; Ferreira, Ângela P.; Leite, VicenteO uso de energias renováveis, nomeadamente, fotovoltaica, eólica e hídrica, é uma alternativa para reduzir a emissão de poluentes e aumentar a produção dispersa de energia e a sua integração na rede elétrica ou em microrredes. A presente dissertação tem como objetivo implementar e validar um sistema de proteção eletrónico que permite acoplar turbinas eólicas e pico-hídricas com inversores eletrónicos. O sistema é constituído por circuitos eletrónicos que retificam e filtram a tensão de saída dos geradores acoplados às turbinas e protegem a entrada dos conversores eletrónicos, de ligação à rede, contra sobretensão. Na ausência desse sistema, caso seja aplicado um valor de tensão superior ao máximo suportado na entrada dos conversores, estes são danificados, já que a velocidade da turbina e, consequentemente a tensão de saída do gerador aumentam se trabalharem em vazio, ou seja, sem carga. A validação do sistema desenvolvido foi realizada em duas etapas e consiste em verificar os instantes em que as proteções atuam para dois casos: em vazio, quando não existe carga na saída do gerador; em excesso de potência, quando os inversores não conseguem processar toda a potência disponível no gerador. Na primeira etapa, três sistemas picohídricos reais são testados para observar o comportamento do circuito de proteção em vazio. O primeiro sistema consiste numa roda d’água ligada em um gerador que pode ir até os 300 W, os restantes referem-se a duas turbinas pico-hídricas, uma Pelton e outra Turgo, conectadas a geradores que podem fornecer até 1200 W. Na segunda etapa, testes adicionais são desenvolvidos em uma bancada com um aerogerador, a fim de simular o comportamento de uma pico-hídrica que fornece potência superior ao valor que o inversor fotovoltaico consegue processar. Além disso, oito modelos de inversores distintos foram testados e, independente de terem sido sincronizados com a rede elétrica, os circuitos de proteção projetados mostraram-se eficientes em todos os testes, pois limitaram o valor da tensão e da potência parametrizadas para cada inversor.
- Over-voltage protection for pico-hydro generation using PV microinvertersPublication . Scotta, Isabella Cristina; Ribeiro, Gabriela Moreira; Maidana, Wellington; Leite, V.Innovative, low-cost, environmentally friendly and renewable resource-based solutions are emerging to meet growing global energy demand. Hydroelectric technology is quite old and mature. Despite its importance, it is associated with large plants, with environmental impact. On contrary, small-scale systems, called pico-hydro systems (up to 5 kW) are not yet explored. Anyway, the exploration of pico-hydro systems has been increasing consistently, from the first off-grid applications in remote places to distributed generation, with the injection of the generated energy in the main grid or microgrids. Very recently, there have been advances in grid connection of these small-scale systems, using off-the-shelf components. Indeed, pico-hydro systems can be connected to the grid using off-the-shelf components, namely photovoltaic inverters. Thus, grid-connected pico-hydro systems have gained an enormous potential in distributed production. However, in situations of over-power, or whenever the generator is under no load, there is a need for effective over-voltage protection, unlike photovoltaic systems. The goal of this paper is to propose an over-voltage protection circuit, designed to ensure the integration of low-power pico-hydro systems connected to the grid using conventional photovoltaic microinverters. Extensive tests were performed on an experimental platform using three microinverters easily found on the market and a low power generator (300 W) developed for small wind turbines. The experimental results, demonstrated the performance of the proposed over-voltage protection circuit in four different situations, presented in this work, thus avoiding irreversible damages of generators and microinverters, in the context of the above described grid connection approach.
- Overvoltage protection for grid-connected picohydro generation using photovoltaic invertersPublication . Scotta, Isabella Cristina; Maidana, Wellington; Leite, VicenteVery small-scale hydropower plants are environmentally friendly and renewable resource-based innovative solutions. The interest in pico-hydro systems (up to 5 kW) has increased significantly from the first stand-alone applications, at remote sites, to the distributed generation, with the injection of generated energy into the grid. Recently, there have been advances in the grid connection of these systems using off-the-shelf components, namely photovoltaic inverters. Therefore, pico-hydro systems have gained an enormous potential in distributed generation, particularly in the context of microgrids. However, in situations of over-power, or whenever the generator is under no load, e.g. when the grid fails, there is a need for effective over-voltage protection, as in small wind turbines. This paper proposes two over-voltage protection circuits, designed to ensure the integration of pico-hydro turbines connected to the grid using conventional photovoltaic microinverters and string inverters, for power ranges of 300 W and some kW, respectively. Extensive tests were performed on an emulation platform and a workbench using these two different over-voltage protection circuits. One is designed to connect the generators of water wheels to the grid and the other to connect 1,500 W generators of water turbines. The experimental results demonstrated the performance of the proposed over-voltage protection circuits in four different situations. Both avoid irreversible damages of generators, photovoltaic microinverters and string inverters in the context of the above-described grid connection approach.