Transmotor-Flywheel Powertrain Assisted by Ultracapacitor

Abstract

Battery electric vehicles (BEVs) can recuperate the kinetic energy of the moving vehicle by the process of regenerative braking. However, this feature is limited by the battery recharge power rating that is often significantly less than the BEV propulsion power rating. This study proposes a powertrain for BEVs that is capable of improving regenerative braking significantly by utilizing a lightweight flywheel and small ultracapacitor pack as power buffers. In order to connect the flywheel and ultracapacitor to the drive shaft effectively and more efficiently, a two-shaft electric motor called the transmotor is utilized. Further, the proposed powertrain, transmotor–flywheel assisted by ultracapacitor, enables us to reduce the power rating of the battery pack to the extent that it only be used for low power demand loads such as cruising. A braking scenario simulation followed by an emulation test is presented to demonstrate the above enhancement.