Abstract
This paper introduces a novel design of an electric vehicle (EV) fast charging station, consisting of a battery energy storage system (BESS) with reconfigurable cell topology. The BESS comprises two battery strings that decouple the power flow between EV and grid, to enable charging powers above the grid capacity. The reconfigurable design is achieved by equipping the battery cells with semiconductor switches and serves two main purposes. First, it aims at solving cell unbalance issues to increase safety, reliability, and lifetime of the battery. Second, it enables the BESS to actively control the EV charging process by changing its cell configuration in a real-time fashion, making a DC-DC converter redundant. The paper presents a modelling approach that captures the reconfigurable design including the controlling algorithm used for cell engagement. The simulation results show that the BESS is able to fulfil the EV request with sufficient accuracy for most of the fast charging process. However, the switching of cells leads to variations in the charging current that can potentially exceed the tolerance band defined in IEC61851-23. Therefore, complementary measures are suggested to achieve a suitable current control during all phases of the charging process. The estimated BESS efficiency during the EV fast charging process is 93.3%. The losses caused by the reconfigurable design amount to 1.2% of the provided energy. It is demonstrated that the proposed design has a competitive efficiency compared to a battery buffered fast charging station with DC-DC converter.
Highlights
Introduction iationsThe transportation sector is currently experiencing a paradigm shift as gasolinepowered vehicles are being gradually replaced with electric vehicles (EVs)
The results suggest that a reconfigurable battery is generally able to control the power transfer to an EV without the need of a DC-DC converter interconnected between the two units
The present work introduces a novel design of a double-string battery energy storage system (BESS) with reconfigurable cell topology, that is operated as an EV fast charging station
Summary
The transportation sector is currently experiencing a paradigm shift as gasolinepowered vehicles are being gradually replaced with electric vehicles (EVs). Driven by global ambitions to phase out fossil fuels, the integration of EVs in the electricity network offers the opportunity for a future mobility powered by renewable energy sources such as wind and solar [1]. While the number of EVs has been increasing in recent years, typical concerns of potential costumers remain range anxiety, long charging times, and insufficient charging infrastructure [2,3]. It is expected that an increased deployment of fast charging stations will help to mitigate those concerns and enable the widespread adoption of EVs [3,4]. The optimal placement of fast chargers is Copyright: c 2021 by the authors
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