Lower Speed Range Drive for Sensorless Vector Controlled Induction Machines with Stator Voltage Offset Compensation Method

The vector control method is widely used for induction machine drives. Recently, sensorless vector control for induction machine has been investigated and proposed. The speed range for the drives is limited to about 1:100 in industry. The main reason for this limitation is the inaccuracy of stator voltage measurement. The lower rotor speed becomes, the lower stator voltage is. Therefore, it is difficult to detect the stator voltage accurately in the lower speed region, and difficult to control motor speed and motor torque precisely. This paper presents a method of improving the lower speed performance of sensorless vector controlled induction machine drives using offset compensation of stator voltage. The offset is compensated by using the fluctuation of the estimated rotor flux. The validity of the proposed method is verified by experimentation.