A double-stator permanent magnet brushless machine system for electric variable transmission in hybrid electric vehicles

In this paper, a totally brushless electric variable transmission (EVT) machine system is proposed for hybrid electric vehicles (HEVs). The key is to cascade a double-stator permanent-magnet brushless (DS-PMBL) machine with an induction motor to form a new EVT machine system. It not only provides the merits of power splitting as other EVT systems, but also offers the unique advantage that the whole machine system does not involve any carbon brushes or slip rings. Hence, throughout the whole driving profile of HEVs, the proposed machine system can enable the engine operating at its optimal operation area at which its efficiency is the maximum. The control strategy and operation modes of the proposed EVT machine system are elaborated. The validity of system operation is verified by computer simulation. Finally, a DS-PMBL machine prototype is tested to verify its functionality.