Design and Analysis of Electrical Braking Torque Limit Trajectory for Regenerative Braking in Electric Vehicles with PMSM Drive Systems

In this paper, an electrical braking torque limit trajectory is designed to improve the regenerative braking of electric vehicles based on a regenerative power analysis. Even though electric motors generally regenerate electric energy from kinetic energy, the drive system dissipates electric energy under certain low-speed operation conditions. This phenomenon has been addressed in many previous works and most of them compensate for this power dissipation region by modifying the electrical braking torque limit trajectory of the motor. However, the torque limit trajectory has never been considered based on a regenerative power analysis even though an inaccurate torque limit trajectory causes energy loss to the drive system. In this paper, the regenerative power analysis for two major kinds of permanent magnet synchronous motor is performed. Afterward, torque limit trajectories are set based on this analysis so that batteries in electric vehicles can harvest the maximum regenerative energy in any circumstance. To verify the analysis and proposed torque limit trajectories, simulations and experiments are performed.