MRAS rotor resistance estimators for EV vector controlled induction motor traction drive: Analysis and experimental results

The Field Oriented Control algorithm needs accurate estimation of motor state variables in order to ensure full torque performances and good efficiency. On electric vehicle traction drives, Induction motor Field Oriented Control is widely adopted. Good control results are strongly related to parameter values used by observers or estimators, which vary according to machine working conditions and temperature. The most important parameter is the rotor resistance. The paper shows and compares two different MRAS rotor resistance estimators, based on reactive power and motor torque, studied by means of a sensitivity analysis for different load and speed operating conditions. A nonlinear correction algorithm has been proposed in order to assure a good rotor resistance estimation convergence also under dynamic conditions. Sensitivity analysis, simulation and experimental results are reported for the proposed methods. The estimation algorithm has been also experimentally tested on a prototypal electric vehicle to demonstrate its validity under dynamic condition during a real driving cycle.