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- Pico-hydro systems: microgrid-connection approachesPublication . Leite, V.; Ferreira, Ângela P.; Couto, José; Batista, JoséSmall hydropower systems are considered an environmentally friendly energy option. They have a huge untapped potential which allows them to make a more significant contribution to future energy demand with many advantages. The integration of pico-hydro systems into microgrids is an emerging solution for the electrification of remote areas and for self-sustainable power systems. This paper presents and discusses the three main grid connection approaches for pico-hydro systems focused on the integration in small microgrids: using specifically designed power converters, using standard wind inverters and using standard photovoltaic inverters. These latest approaches based on conventional inverters are able to explore a large amount of feasible sites with low-head and very low-head. They improve efficiencies, reduce costs and environmental impacts and improve reliability. Experimental evaluation of the performance in steady-state and in dynamic conditions proves the feasibility of these innovative approaches.
- Implementation of a smart microgrid in a small museum: the silk housePublication . Figueiredo, Luís Guilherme Aguiar; Maidana, Wellington; Leite, V.Microgrids are an alternative approach for the supply of energy integrating decentralized power sources, electrical loads, energy storage, and management in a local grid. The system has the capability of power control and energy management using communications’ network between all devices, and is known as smart microgrid. This paper presents the implementation of a smart microgrid in the Silk House, a museum dedicated to dissemination of science located in Bragança, Portugal. It was funded by the Foundation for Science and Technology of Portugal under the SilkHouse Project. The goal is to transform the House of Silk in a self-sustainable museum contributing to the dissemination of renewable sources and new technologies for future buildings in smart cities. This work presents the context and requirements for the microgrid and describes the implementation of the renewable sources (photovoltaic and pico-hydro) and the SMA Flexible Storage System based on Sunny Island and Sunny Home Manager. This work also presents and analysis the first operating results since the start of operation at the end of July 2019.
- Improving the storage capability of a microgrid with a vehicle-to-grid interfacePublication . Leite, V.; Ferreira, Ângela P.; Batista, JoséIn the emergent deployment of microgrids, storage systems play an important role providing ancillary services, such as backup power and reactive power support. This concept becomes crucial in the context of microgrids with a high penetration of renewable energy resources, where storage systems may be used to smooth the intermittency and variability of most of them. Plug-in electric vehicles provide an enormous distributed storage capability, which favours the technical and economical exploitation of such systems. This paper presents a comprehensive implementation and control of a bidirectional power converter for Vehicle-to-Grid integration, based on a bidirectional DC/DC converter followed by a full bridge DC/AC converter. The evaluation of the adopted topology and its control is performed through MATLAB/Simulink simulation.
- On the implementation of a microgrid project with renewable distributed generationPublication . Leite, V.; Ferreira, Ângela P.; Batista, JoséThis paper describes the on-going implementation of a microgrid project with renewable distributed generation under the context of an initiative with demonstration purposes in an university campus. In the actual context of the electrical energy demand increase and limited conventional resources, along with the consciousness of the climate changes and the need to invest in clean energies, microgrids allows the integration of dispersed energy sources, mainly renewable, which make them cost effective, providing a viable alternative to centralized production, transmission and distribution system for remote community areas. The design concept of the microgrid and a description of the base equipment and energy sources already integrated are presented. From the on-going projects to be integrated on the microgrid, it is presented the Grid-to- Vehicle and Vehicle-to-Grid concept, which will provide a second energy storage element using the battery of an electric vehicle. To accomplish this objective, a bi-directional power converter is being developed and simulation results of its power structure and control are presented.
- 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.