An improved sensorless speed control of indirect stator flux-oriented induction motor drives

A new method for implementation of a sensorless indirect stator flux oriented control (ISFOC) of induction motor drives with stator resistance tuning is proposed in this paper. The proposed method for estimation the speed and stator resistance is based only on measurement of stator currents. The error of the measured q-axis current from its reference value feeds proportional plus integral (PI) controller and the output of which is the estimated slip frequency. It is subtracted to the synchronous angular frequency, which is obtained from the output integral plus proportional (IP) rotor speed controller, to have the estimated rotor speed. For current regulation, we propose a conventional PI controller with feedforward compensation terms in the synchronous frame. Owing to its advantages, an IP controller is applied to the rotor speed regulation. 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. 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. Digital simulation and experimental results are carried out to show the improvement performance of the proposed method.