Design methodology of a series-series inductive power transfer system for electric vehicle battery charger application

Contactless battery charging can be safer and more convenient than the plug-in charging of electric vehicles (EVs). Different compensation topologies have been studied for contactless power transfer systems depending on the applications and in consideration of the stability of the configuration. However, the conventional voltage supply mandates the use of an extra voltage-to-current converter stage for EV charging. Alternatively, switching of converter topologies has been reported to satisfy the battery charging profile. This paper proposes a design methodology using a series-series (S-S) contactless power transfer system for EV battery charger with two fixed operating frequencies. The converter operates at one of the fixed frequencies for a load-independent current output and the other operating frequency for a load-independent voltage output. With proper design of transformer inductance and primary compensation capacitor, zero voltage switching (ZVS) can be achieved to improve efficiency. Since the system is operating at two fixed frequencies for the whole charging profile of the EV battery, the proposed charging method simplifies the controller and improves the system reliability significantly.