Ultracapacitor Plus Battery Energy Storage System Sizing Methodology for HEV Power Split Electronic CVT's

The power split architecture has become the gold standard of hybrid propulsion systems because the global OEM's have converged to the electronic-continuously variable transmission, or e-CVT in two different configurations. For Toyota and Ford the single epicyclic gear set, THS and FHS respectively e-CVT. For GM-DCX and others to the dual epicyclic gear set, AHS designs possessing 2- modes of operation. Regardless of architecture, power split transmissions require a pair of electric motor-generators in order to deliver their intended function. This paper explores several techniques of incorporating ultracapacitors into the power split system and proposes a novel configuration in which the battery is downsized and power constrained by its interface dc-dc converter whereas the ultracapacitor is directly tied to the power split electric path floating bus. Different signal processing techniques are introduced for the decomposition of driveline power into command signals to control engine power and battery power levels while the ultracapacitor responds autonomously to the residue of propulsion power demand. Relative battery and ultracapacitor sizes are presented for the proposed configuration.