Drive Cycle-Based Loss Minimization Strategies for Induction Motor Drives in Electrified Vehicles

A wide range of speed and torque demands are imposed on the electric motor drive systems for automotive traction applications. Reduction of losses in the traction motor is a key to enhancing the overall efficiency of the e-drive system. However, loss reduction becomes a challenge under such widely varying conditions, due to operating point dependencies. Particularly, drive cycles comprising of rapidly varying vehicle load patterns pose additional difficulty in the design of loss reducing algorithms. A model-based, offline loss minimization method is presented in this paper, by performing a constrained optimization of the operating point-dependent loss function. A control strategy using a varying motor flux approach is adopted. Detailed simulation studies are carried out on a rotor-field orientation-controlled induction motor drive system, to demonstrate the performance of the loss minimization method for various load patterns. Results indicate that the control algorithm works effectively for drive cycles involving modal behavior but exhibits limited performance in drive cycles consisting of dominantly transient behavior. Further, use of this algorithm is restricted to a speed limit in the flux-weakening region which curtails the motor flux to a maximum permissible profile.