Control Strategy Of Regenerative Braking For Electric Vehicles

Faced with the problems of today’s energy shortage and environmental issues, electric vehicles have become a trend in the auto industry. Due to the current vehicle battery technology is still a bottleneck, driving range still cannot meet the demand to some extent, regenerative braking based on the existing structural components of electric vehicles, produce brake torque while controlling the motor power and achieve braking and recover part of the braking energy, it can make up the defect of pure electric vehicle driving range insufficient. How to improve the efficiency of energy recovery is one of the key issues of electric vehicle braking technology research.In this paper the braking structure of the electric vehicle was discussed briefly. Then the mild, moderate and emergency braking modes and factors influence electric vehicle braking systems were analyzed. A mathematical model of electric vehicle braking system was established, including brake kinetics model, motor model and battery models, lay the foundation for the establishment and simulation of vehicle models. Focused on the vehicle induction motor braking control strategy, the mathematical model of the induction motor with a stator iron loss was built, which combines efficiency optimization with speed sensorless control as strategies to increase the driving range of electric vehicles.Based on MATLAB/Simulink, a direct torque control was adopted as framework, control strategy model with optimum efficiency of induction motor and speed sensorless control was provided. From flux observation, motor loss, speed tracking and several aspects to verify the correctness and accuracy of the control strategy, the simulation results show that electric cars can realize the motor process of tracking rotor speed and stator flux is maintained at the optimum flux run. Moreover the motor efficiency is increased from 75% to 84%. Therefore the driving range of electric vehicles increases.Finally, by means of simulation software ADVISOR, the vehicle dynamics, electronic brake force distribution, battery model was established. Selected a typical Chinese city drive cycle and Chinaurban 1015 drive cycle, during the vehicle braking process, the battery SOC, energy recovery situation were analyzed to verify the feasibility of the proposed control strategy.