Power electronic interface circuits for batteries and ultracapacitors in electric vehicles and battery storage systems

A battery load leveling arrangement for an electrically powered system in which battery loading is subject to intermittent high current loading, the system including a battery coupled to supply electric power to a DC link, a load, and a system controller coupled in circuit between the DC link and load for controlling application of power to the load, said battery load leveling arrangement comprising:

• a passive energy storage device;
• a first bidirectional converter coupled in circuit with the passive energy storage device and the DC link for transferring electrical power between the DC link and the energy storage device;
• a second bidirectional converter coupled in circuit between the battery and the DC link for transferring electrical power between the battery and DC link;
• and
• unidirectional conducting means coupling the battery to the energy storage device and poled to conduct conventional current from the battery to the energy storage device whereby battery current can be coupled to the DC link through each of the first and second converters when battery terminal voltage is greater than voltage on said passive energy storage device by an amount at least equal to a voltage drop across said unidirectional conducting means.