Voltage controller for flux weakening operation of interior permanent magnet synchronous motor in automotive traction applications

In electric automotive traction drives an optimal utilization of the DC-bus voltage in the wide flux weakening range is crucial. At the same time a voltage margin is required to ensure the stability of the inner current control loop. An adequate trade-off between these conflicting objectives is obtained by employing a superimposed voltage controller that is activated during flux weakening operation. In this paper, the design of such a voltage controller is presented. A simplified voltage controller plant model is identified from step response measurements. Due to variations of the plant parameters, the voltage controller is designed as a gain-scheduling controller with sufficient robustness towards plant model inaccuracies. The performance of the voltage controller is demonstrated by test-bench measurements based on an electric traction motor typically employed in sub-compact electric vehicles.