Stator Resistance Estimation using DC Injection with Reduced Torque Ripple in Induction Motor Sensorless Drives

In this article, the torque ripple of an induction motor due to dc injection for the stator resistance estimation is analyzed. In 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 synchronous reference frame, flux and torque fluctuation due to injected dc and arbitrary second harmonic current is calculated. Furthermore, the current reference that nullifies the fundamental frequency torque ripple in the whole operating condition is proposed. An integral-based average filter is applied to extract dc signals in phase voltage and current. Simulations and experiments are carried out to verify the performance of the proposed methods.