Research On Regenerative Braking Characteristics Of Series-parallel Hybrid Electric Vehicle

Currently, researchers pay more attention to hybrid technology, because hybrid electric vehicle has the merits of traditional fuel vehicle and pure electric vehicle. Regenerative braking technology can recycle a portion of the kinetic energy of braking. The regenerative energy is stored in the battery or other energy storage device. The supply of regenerative braking technology can improve the utilization of energy and the driving distance greatly. In China, the regenerative braking technology has become a hot spot of the hybrid technology.With Geely hybrid electric vehicle technical research projects and the national"863program" as background, this paper researched the regenerative characteristic of series-parallel hybrid electric vehicle which also called SPHEV. The topic of this paper included the braking force distribution, the design of braking mode, the optimization control of dual motors, the modeling of regenerative braking system, the simulation of regenerative characteristic, the chassis dynamometer test and road test.The power systems and hydraulic braking systems were modeled using Matlab/Simulink software, after the research on the characteristic of the power systems and hydraulic braking systems.Three factors were analyzed, including the braking force distribution coefficient, the available maximum charging power of the battery, the maximum generative torque and efficiency of motor. Considering the limitation of ECE braking regulations and the available maximum torque of planetary output ring gear, the braking force distribution coefficient and control strategy of regenerative braking torque and mechanical braking torque which supplied on the front wheels were designed. This paper also designed the regenerative braking mode and the optimization of the available maximum torque of planetary output ring gear for each braking mode.The regenerative braking strategy model was also built using the Matlab/Simulink software, and was linked with the power system model and hydraulic braking system to form regenerative braking system simulation model. The simulation of regenerative characteristic was made through setting different initial braking speed, different initial SOC, different braking strength. This paper has analyzed the status of dual motors and the battery and how this several factors affect the regenerative braking. The results of simulation confirmed that the control strategy can regenerate the braking energy effectively.The vehicle chassis dynamometer test under NEDC driving cycle and road test also made to verify the practicability and effectiveness of control strategy in this paper. The results of chassis dynamometer test noted that the average percentage of regenerative braking can be25.97. The road test showed that the percentage of regenerative braking was more than20.