STATOR-FLUX-ORIENTED SENSORLESS INDUCTION-MOTOR DRIVE FOR OPTIMUM LOW-SPEED PERFORMANCE

For high-performance ac drives, the speed-sensorless vector control of induction motors has received increasing attention from the standpoin ts of cost, size, noise immunity, and reliability. This paper presents the speed-and voltage-sensorless drive of vector-controlled induction motors for general-purpose drive applications, The rotor speed is det ermined by the difference between the synchronous angular frequency an d the estimated slip angular frequency, which is estimated by the dete cted stator current and the stator-flux reference, To improve the low- speed drive characteristics, accurate applied-voltage calculation is p roposed under considerations of the compensations for the quantization error in the digital controller, the forward voltage drop of switchin g devices, and the dead time of the inverter. The experimental studies show the improved drive characteristics.