Braking energy recuperation characteristics of hydraulic hybrid powertrain with dual-planetary gear sets

Hydraulic hybrid powertrain has more energy saving potential than that of hybrid electric powertrain under urban driving cycle characterized as higher braking energy ratio and frequent stop-and-start operation. A new type of compound power split hybrid powertrain scheme with dual-planetary was developed in the paper. The characteristics of system power flow under braking condition were analyzed and basis control strategy was proposed. Power flow modes of hydraulic units were analyzed. The dynamic mathematic model was set up to simulate performance of the hydraulic hybrid vehicle under UDDS based on the basic control strategy. The results showed that 28% energy saving on average could be achieved.