A new stator resistance estimation method for high performance stator-flux oriented sensorless induction motor drives

This paper deals with a novel method for implementation of a sensorless stator flux oriented control (SFOC) of induction motor drive with stator resistance tuning. The rotor speed is determined by the difference between the synchronous angular frequency and the estimated slip angular frequency which is estimated from the measured and reference q-axis stator current. The stator resistance updating is based on the measured and reference d-axis stator current of an induction motor on d-q frame synchronously rotating with the stator flux vector. The proposed method for estimation of speed and stator resistance is based only on measurement of stator currents and dc-bus voltage. Digital simulation is carried out to show that the proposed method can overcome the problem of performance degradation due essentially to changes in stator resistance. Robust sensorless speed control at nominal, low and zero speeds is introduced, with load torque applied, in order to show the robustness of the proposed method. Experimental results for a 3-kW induction motor are presented and analyzed by using a dSpace system with DS1102 controller board based on the digital signal processor (DSP) TMS320C31.