Stable And Passive Observer-Based V/Hz Control For Induction Motors

According to an aspect, there is provided an apparatus for a drive for driving an induction motor. The apparatus comprising means for performing the following. The apparatus obtains a stator current vector of the induction motor and estimates, using a state observer for the stator and/or rotor flux linkage vector of the induction motor, the stator and/or rotor flux linkage vector based on the stator current vector, a voltage reference vector and a stator angular frequency reference. The state observer is a speed-sensorless reduced-order state observer based on a mathematical model of the induction motor. The apparatus performs speed-sensorless state-feedback control based on the estimated stator and/or rotor flux linkage vector, the stator current vector, a stator flux linkage reference vector and the stator angular frequency reference for calculating the stator voltage reference vector. The apparatus applies the stator voltage reference vector to an inverter of the drive.