A measurement method of the exact variations of the self and mutual inductances of a buried permanent magnet synchronous motor and its application to the reduction of torque ripples

In this paper, a new measurement method of the variations of the self and mutual inductances of a buried permanent magnet synchronous motor is proposed. This method allows the calculation of the inductance variations in the Concordia's reference frame without resorting to Park's assumption of sinusoidal pattern. Afterwards, these parameters are used to develop a new nonlinear torque control strategy. This controller simultaneously achieves accurate torque control (in fact the torque ripples are reduced to zero) and copper losses minimization. To reach this goal, the authors apply input-output linearization techniques where the inputs are the stator voltages and the outputs are the provided torque and a judiciously chosen output linked to the copper losses in such a way that, when forced to zero, it leads to the maximum machine efficiency. The performance of the measurement method and of the control strategy is demonstrated by simulations. The results are compared to the ones obtained with a controller based on Park's assumptions.