Torque Ripple Reduction in Stator Resistance Estimation using DC Current Injection for Induction Motor Sensorless Drives

In this paper, the flux and torque ripple of an induction motor due to DC current injection for the stator resistance estimation is analyzed. For the analysis, the fundamental component of rotor flux is used for rotor flux orientation to avoid the perturbation issue in synchronous reference speed. On the reference frame aligned to the rotor flux, flux fluctuation due to arbitrarily injected DC and 2nd harmonic current is calculated. And based on the calculated flux fluctuation, the current reference which nullifies torque ripple is proposed. The proposed method is applicable to the induction motor sensorless control in low-speed region, where the torque ripple cannot be filtered out by the inertia of the drive system. Simulations and experiments are conducted to verify the performance of the proposed method.