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- Improvement of DC microgrid voltage regulation based on bidirectional intelligent charging systemsPublication . Santos, Pedro; Fonte, Pedro M; Luís, RicardoIn several cities, there are existing DC tram/subway grids. These existing grids in some cases cover a big part of the city and create the opportunity to install EV charging infrastructures. Such implementation could be built in order to contribute to the DC grid stability, enhancing the DC grid voltage regulation, through vehicle-to-tram concept. This can be reached with bidirectional DC/DC converters which enable energy transfer from vehicles to the DC grid to support such starts. Hereafter, the energy may flow normally from the grid to the vehicles. However, these improvements come with certain challenges in terms of power conversion, voltage regulation, grid coordination and intelligence. This paper defines the design principles of a tram DC-microgrid, which enables fast-charging, supported by fuzzy controllers that follow dynamically the overhead line voltages and the charging/discharging conditions of the proposed EV charging infrastructure. A discussion and conclusion about the practical applicability of the tram DC microgrid and its the complementarity with the EV charging infrastructure are demonstrated evaluating the results of DCmicrogrid voltage regulation with the proposed methodology.
- ESS design and management considering solar PV to fed off-grid EV chargerPublication . Santos, Diogo; Fonte, Pedro M; Pereira, Rita; Barata, Filipe; Almeida, Paulo; Cordeiro, Armando; Luís, Ricardo; Fernao Pires, VitorThe increase of electric vehicles creates several challenges to the electric grid, mainly in those with weak power or off-grid. DC microgrids are becoming more and more important in the context of renewable energy sources, where solar PV systems are dominant. In this paper is proposed the design of a DC system to charge electric vehicles using PV generation and a battery storage system. A single DC-DC converter is used to operate the solar PV array with maximum power point tracking method and controls power flow from PV to storage battery and to the EV, operating as DC EV charger. The operation under various loading conditions is discussed. The performance of the proposed solution was simulated using MATLAB/Simulink software.