Model predictive control based field-weakening strategy for traction EV used induction motor

In typical traction Electric Vehicle applications, the DC-link voltage varies during transient accelerating and decelerating process in field-weakening region. The calculated reference voltages of current PI regulators tend to be larger than the one in steady state, which will result in the undesired flux-producing current oscillations. This further deteriorates the electromagnetic torque performance. To solve this issue, a model predictive control (MPC) based field-weakening algorithm is proposed for traction EV used low-voltage induction motor (IM). n this paper, the DC-link voltage utilization, which is usually set as high as possible to output maximum torque, is decreased temporarily to keep the flux-producing current unchanged during the braking process. The model predictive control is adopted for the voltage loop, in which the steady voltage is calculated with steady flux equation. The influence of overlarge voltage calculated from PI regulator is decreased. The simulation and experimental results provide the evidence of improvements of the proposed field-weakening algorithm.