Comparison of common DC and AC bus architectures for EV fast charging stations and impact on power quality

Abstract

Abstract This work covers the comparative analysis of common DC and AC bus architectures for grid-connected Electric Vehicle Fast Charging Stations (EVFCS) and addresses the relevant power quality issues. In this manuscript, Unipolar Common DC Bus and Common AC bus topologies are proposed for FCS. Two-level Voltage Source Converter (VSC) is used to connect the EVFCS to the grid through DC and AC buses in both the methods. Converters are connected to the grid through a Distribution Transformer (DT), and the output side is connected to the EV battery chargers. Grid-connected FCS are examined in terms of harmonic generation, and their impact on the host electric grid is evaluated. Voltage and current harmonics of both the topologies with different transformer configurations are compared, and an optimum transformer configuration is proposed. The Unit Template-based Control (UTC) algorithm is also proposed in this work, and the Constant Current-Constant Voltage (CC-CV) strategy is used for the charging control of the batteries. The work is focused on feasibility and comparison of common DC and AC bus FCS and impacts of harmonics generated due to EV charging on the grid power quality. The proposed architectures are then evaluated as per IEC and IEEE Power Quality standards. Power quality impacts are studied by varying the number of EV charging bays. The charging profile of both the architectures is examined by performing steady-state and dynamic analysis. Furthermore, a comparative analysis is also performed by considering different transformer configurations.