Cost Effective High Power MV Charger Concepts for Highway Charging Stations

Abstract:
Rising demand for shorter charging times to further drive the transition from combustion engines towards more environmental friendly electric vehicles is lifting the power levels of electric vehicle charging applications. Charging powers of up to 400kW and even more will be state of the art in modern chargers, especially for infrastructural areas like highways, where immense recharging rates are desirable for public as well as commercial transportation. Due to the tremendous charging power levels, the design of EV charging stations is challenging and direct connection to the medium voltage grid is required. In this paper, a holistic approach for cost effective, robust as well as highly efficient charging stations is proposed and discussed. Special focus is paid on insulation requirements when connecting the chargers to the medium voltage grid. In order to keep cost and complexity as small as possible, passive rectifier stages are proposed for the input stage of the individual chargers and multi-level resonant LLC converters are considered for the DC/DC converter stage of the charger. For concept verification, a charging station with 10 chargers, each showing a power level of 400kW is contemplated. The station is connected to the 20 kV medium voltage grid and especially the resulting grid side current waveforms are analyzed using PLECS simulation software.