Mitigation of torque oscillations caused by dc injection-based resistance estimation through resonant controllers

Stator on-line resistance estimation is often used, among others techniques, for thermal monitoring, flux and torque estimation in induction motor high performance drives. Dc current injection methods are some of the most well succeeded techniques found in literature for this purpose. In spite of this, the dc component added gives rise to oscillation in the electromagnetic torque, which can disturb the driven load and the industrial process controlled by the drive. In order to attenuate this component, a second-order current harmonic injection can be used. However, when proportional-integral controllers are employed, four additional transformations are required. This paper proposed a control scheme based on adaptive resonant control, that presents the advantage of reducing computational requirements, since additional transformations are not required. The results show that similar performance with reduced complexity are accomplished.