Ultra-fast charging station for electric vehicles with integrated split grid storage

This paper presents the detailed analysis, optimisation and hardware realisation of an ultra-fast charging station with a split grid storage battery which enables to recharge electric vehicles (EVs) in less than 10 minutes. The station consists of a T-type AC-DC grid interface connected to the 400 V low voltage AC grid, a DC-DC dual active bridge (DAB) isolation stage, a stationary storage battery and a high power multi-phase interleaved buck converter for charging operation. The operating principle of the converter systems is briefly explained and the analytical loss models of the components are derived which are used in an optimisation procedure to evaluate the pareto front limits in terms of efficiency and power density for the DAB isolation stage and the high power charger. By introducing a split storage battery, beneficial conditions for the semiconductor devices are achieved so that the losses of the high power charger can be reduced by approximately 35 % with respect to a standard solution without a split as will be shown in the paper.