A new buck-and-boost ultracapacitor interface circuit for the HEVs

This paper presents a new buck-and-boost ultracapacitor interface circuit used between ultracapacitors and DC bus (batteries) in the hybrid electric vehicles. Ultracapacitors are electrochemical energy storage/conversion systems of high power applied in hybrid electric vehicles beside batteries. Since the voltage level of the DC bus differs from the ultracapacitor, it is necessary to utilize an interface circuit to balance (increase or decrease) the voltage between the DC bus and ultracapacitor. The operation of the proposed circuit is introduced and experimental results confirm the theoretical analysis.