Regenerative Braking for EVs Using PMSM with CHB as Bidirectional Traction Converter

Permanent-magnet synchronous motor (PMSM) is broadly adopted in electric vehicles (EVs) due to its superior advantages like providing high efficiency and excellent torque-speed characteristics. Regenerative braking (RB), which is the recovery of the kinetic energy during deceleration, is an efficient method to restore the kinetic energy into the battery to extend the battery and hence the driving range. In this paper, an RB strategy is proposed where the drive shaft's torque is estimated using a detailed analysis of all the forces acting on an EV along an inclined road. To achieve the maximum electromagnetic torque, the d-axis component of the stator current is set to zero. Then, the three-phase voltages are generated and applied to the stator windings based on the EV demand. To improve the harmonic performance, the multilevel cascaded half-bridge (CHB) converter is used as the bidirectional traction converter. The proposed RB strategy is verified in the operating modes of acceleration, deceleration (braking), and constant speed using MATLAB/Simulink computer simulations and tested with a small-scale experimental rig controlled by TMSF28335 Digital Signal Processor.