Novel Electric Vehicle Traction Architecture With 48 V Battery and Multi-Input, High Conversion Ratio Converter for High and Variable DC-Link Voltage

A new architecture for electric vehicle (EV) traction system with multiple low voltage battery packs and high conversion ratio DC-DC converter is proposed here. In EV traction systems, higher voltage motors offer improved efficiency and power density. In some designs, a boost DC-DC converter is employed to accommodate large variation in battery voltage and provide a high DC link voltage, but the range of operation of DC-DC converter is limited. The proposed architecture with low voltage battery packs and integrated, multi-input, high conversion ratio converter (HCRC), can reduce the maximum voltage in the vehicle during emergencies, mitigate issues with large number of cells in series, and provide a wide variable DC link voltage. It enables independent charging/discharging control of the different low-voltage battery packs ensuring cell balancing and enhancing reliability. Four distinct configurations are analyzed and the configurations with interleaving are shown to improve performance and significantly reduce the filter inductor size. The proposed HCRC operation for EV application is verified experimentally through a 4-phase multi-input, 4kW hardware prototype. With the nominal input fixed to 48V, the output voltage is controlled to vary between 200V to 800V and the converter achieves a peak efficiency of 98.36% at 50kHz switching frequency.