Patent ID: 7595597

Claim:
A vehicle propulsion system comprising: an alternating current (AC) traction drive system; a bi-directional boost converter comprising a high voltage side and a low voltage side, said bi-directional boost converter electrically coupled to said AC traction drive system; a first energy storage system including a direct current (DC) link electrically coupling said first energy storage system to said AC traction drive system, said first energy storage system comprising at least one of a first ultracapacitor and a first high specific power battery coupled on said high voltage side; a second energy storage system electrically coupled to said AC traction drive system such that a voltage output from said second energy storage system is decoupled from said DC link using said bi-directional boost converter; an energy management system configured to control said first and second energy storage systems when a vehicle is operating in at least one of a pre-charge mode and a normal operation mode with said AC traction drive system enabled; and a pre-charge circuit configured to at least partially charge said first ultracapacitor.