The Modeling And Simulation Of Regenerative Braking System For Mild Hybrid Electric Vehicle

Hybrid Electric Vehicle (HEV) is a new style vehicle, which combines the excellent performance of conventional vehicle with low mission and high efficiency of Electric Vehicle. HEV will be the most feasible clean vehicle in the near future. Regenerative braking (energy recovery braking) is one of key techniques for HEV, which has a direct impact on fuel economy, emission and vehicle security. When HEV is braking, regenerative braking system will make the motor become a generator for generating electricity through the power train system and supplying the whole braking forces or partial braking forces at the same time. Finally, electric energy is saved into the battery pack. Regenerative braking not only realizes the braking and deceleration, but also recovers the kinetic energy. The focus of this paper is on Mild Hybrid Electric Vehicle with ISG. The deeply theoretical researching, system simulation and experiment are completed. The main achievements are listed below: 1. Two kinds of strategies for the braking force distribution and control of HEV is proposed, which based on the dynamics analysis of the vehicle and braking force distribution of conventional vehicle. Both strategies can assure the vehicle security and high efficient energy recovery. 2. Through the analysis of composition characteristics and working feature, a modeling method is proposed which based on energy transfer, and mainly adapted a backward simulation assisting by forward simulation idea. Finally, a model for the regenerative braking system of HEV is built. 3. A performance index is proposed for the energy recovery results based on the working feature of regenerative braking system on HEV. System simulations is completed in different velocity, severity of braking and typical city drive cycles. 4. The simulation results in different drive cycles show that regenerative braking force distribution control strategy can assure the braking security and high efficient energy recovery. The coefficient of recovery reach 10%～25%. 5. Based on ISG hybrid electric rig, a Hardware In the Loop Simulation (HILS) platform is built in dSPACE environment. An entire connection is completed in MATLAB/Simulink/RTW, dSPACE/RTI and ControlDesk. 6. HILS is completed in different velocity, severity of braking, shifts and clutches states with the ISG hybrid electric rig. The test results show that regenerative braking force distribution control strategy can assure the braking security and high efficient energy recovery on the ISG hybrid electric rig. 7. Through comparative tests, influencing factor is found for the coefficient of energy recovery, which lays a foundation for the optimization of regenerative braking control strategy for HEV.