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Energy storage system for grid connection and island operation

In this paper an Energy Storage System (ESS) allowing grid connected and island operation is designed, and the transitions between these operation modes are presented. The proposed ESS has the capability to supply a LV grid after an interruption of the mains, and the ability to reconnect when the mains are restored. The ESS is sized and the controllers are designed. A supervisor for the whole system setting the operating states and the transition between them is developed. The obtained results show that the proposed ESS is able to operate connected and isolated from the grid, changing from different operating states with minimum impact on the grid voltages.