Analysis on compound-split configuration of power-split hybrid electric vehicle

In a power-split hybrid electric vehicle (HEV), the power-split device (PSD) can be classified into input-split, output-split and compound-split types. A systematic analysis methodology is proposed to find out all the suitable schemes for power-split HEV from a variety of compound-split configurations. Based upon the characteristics of mechanical point and PSD itself, three reasonable 4-node lever models are confirmed. In addition, the range of its lever lengths is achieved according to the motor torque and speed characteristics and the electric power ratio characteristic. Then the 4-node lever model is split backward into two single lever models to identify the inner connection of compound-split configurations. Using this analysis method proposed, it is proved that compound-split configuration is suitable for high-speed mode in power-split HEV and the compound-split configuration can be selected easily by setting two mechanical points at the desired transmission ratios. A dual-mode power-split hybrid powertrain system is obtained by adding clutches and the third planetary gear set to the compound-split configuration selected.