Torque and Current Ripple Suppression in Integrated Chargers for Synchronous Reluctance Machines

The automotive industry is increasing the voltage level of electric vehicles from 400 V to 800 V to reduce charging time without increasing the current levels. The vehicle wiring and the connectors that link the external DC fast charger to the internal battery impose limits on the maximum charging current for thermal, mechanical, and reliability reasons. Despite the advent of 800 V vehicles on the market, only a few charging stations support this higher voltage level. Consequently, electric vehicles must be designed to be compatible with 400 V DC charging stations, albeit with a slight increase in both the cost and weight of the powertrain components. The solution outlined in this study involves reconfiguring the electric motor and the inverter into a DC/DC boost converter to adapt the high-voltage battery to the voltage level of the off-board charger. During the charging process, several constraints should be considered for both the machine and off-board charger. These aspects include generating a zero-mean torque independently of the rotor position, minimizing the torque ripple, and minimizing the output-current ripple of the off-board charger. The analysis presented in this paper focuses on synchronous machines without permanent magnets.