Research on the Regenerative Braking Control Strategy Considering Battery/Motor/CVT Joint High Efficiency for CVT Hybrid Electric Vehicle

Abstract

The traditional regenerative braking control strategies for hybrid electric vehicle just only considers to ensure motor to work along with the battery/motor joint optimal efficiency curve, but not consider CVT efficiency, yet in fact that the CVT efficiency varies with the operating condition between 70% and 95% variation and can not be neglected. Based on the analysis of the relationship among the synthesis efficiency and the efficiency of the NiMH battery, ISG motor and CVT, the battery/motor/CVT joint high efficiency are calculated, then the joint high efficiency optimum working curve is drawn, finally the regenerative braking control strategy adopted with the joint high efficiency optimum working curve is proposed. Compared to the offline simulation and HIL test results adopted with the battery/motor joint high efficiency optimum working curve, the motor average generating efficiency increases by 2.23%, braking energy recovery rate increases by 4.09% through offline simulation, and the average generating efficiency increases by 1.13% through HILS test. Both results show that the proposed regenerative braking control strategy can realize the battery, motor and CVT to work with joint high efficiency which fatherly enhances braking energy recovery rate under guaranteeing entire vehicle braking security condition.