Torque Ripple Minimization Using Online Estimation of the Stator Resistances With Consideration of Magnetic Saturation

The tolerances and limitations in design and manufacturing of both electrical motors and inverters lead to parasitic resistances in the phases. Therefore, the phase resistances are asymmetric, which causes an asymmetry among the phase currents and a resulting increase in torque ripple. This paper proposes a novel scheme for torque ripple minimization using online estimation of unbalanced stator resistances of a permanent-magnet synchronous motor. The identifiability of the stator resistances in a nonlinear model is investigated by employing a sensitivity analysis. The phase resistances are estimated by recursive least squares in the rotating reference frame in real time. Using the estimated resistances, torque ripple reduction is achieved by a compensation scheme in the stationary reference frame. The effectiveness of the proposed scheme is verified in both simulation and test-bench experiments. Results with and without consideration of magnetic saturation are compared.