An improved energy control strategy for a dc microgrid including electric vehicle fast charging stations

The number of electric vehicles (EVs) on the road is expected to continue to increase during the next decades due to various factors such as the rapid progress in the EV technology and decreasing battery prices. The prolonged battery charging process, which is one of the main problems that affects the increased EV penetration, makes the fast charging units a more attractive and efficient option for the charging stations. Furthermore, the rapid development of EVs increases the power demand, putting additional burden on the public grid. The DC microgrid is supposed to be a feasible solution for reducing the negative effect of electric vehicle fast charging station (EVFCS) on the electric grid. In this study, a decentralized control strategy based on a low-voltage direct-current (LVDC) bus for a DC microgrid including EVFCS is presented. The charging station is part of a microgrid that includes a PV system, a diesel generator, a local grid connection and two fast charging units (FCUs). The immediate objective of this thesis is to examine the impacts of EVFCS on the grid as well as their potential contributions to the system operation in the case of considering the vehicle-to-grid (V2G) technology to provide ancillary services to the electrical grid. It is especially aimed to mitigate the voltage sag and swell problems by using the EV batteries as a DC source of a distribution static compensator (D-STATCOM) device with a combination of Proportional Integral (PI) control. Simulation studies in MATLAB Simulink/SimPowerSystems show that the decentralized controller provides good dynamic performance in terms of DC bus voltage stability and ensures that the considerable improvements can be achieved from the perspective of distribution system operation such as improved voltage quality and from the perspective of end users such as decreased charging durations. Keywords: Decentralized Control, Distributed Generation, Electric Vehicles, Fast Charging Stations, microgrid, V2G.