Highly efficient and compact DC-DC converter for ultra-fast charging of electric vehicles

The range of electric vehicles is still limited due to long charging times. With fast charging stations that enable to recharge a vehicle battery in a few minutes, the range limitation can be overcome in principle. For such fast charging stations, compact and efficient DC-DC converters with a high output power are required. Therefore, a multi-phase half-bridge DC-DC converter, which is part of an ultra fast charging station capable of charging a vehicle battery in less than 5 min, is presented in this paper. The ultra fast charging station utilises an intermediate storage battery, in order to avoid power pulsations at the grid and to provide additional functionality as e.g. energy storage for renewables. By splitting the intermediate storage battery, the voltage ratings of the semiconductor devices used in the high power DC-DC converter can be reduced, which increases the system efficiency. For further increasing the efficiency, a triangular current modulation (TCM) scheme is applied, which allows zero voltage switching (ZVS) for all semiconductor devices. To achieve a high power density as well as to implement ripple cancelation on the output current, several power electronic modules are parallel interleaved. A detailed analysis of the proposed system and simulation results are provided in this paper. Based on the above mentioned means the DC-DC converter achieves a system efficiency above 99.5% over a wide operating range.