Application of an extended Kalman filter for high-performance current regulation of a vector-controlled induction machine drive

Variable frequency AC drives using voltage-source inverters to supply induction motors are increasingly used in industry for high-performance speed response. Such a drive usually employs a vector-controller at the outer speed-loop which will generate the required torque-current signal. An inner current control loop is incorporated to ensure that an appropriate reference current is impressed on the stator circuit. However, due to nonlinearity and time varying characteristics of the machine circuit, a fixed-parameter regulator cannot give good current control performance in the transient state. The paper presents a model-based predictive current regulator for a vector-controlled induction motor drive. An extended Kalman filter is employed to estimate the back-EMF of the machine stator circuit model used by the inner current regulator loop. This also estimates The voter resistance for slip angular velocity calculation in the outer speed-loop. The adaptive feature of this controller leads to improved speed-response performance from the induction machine.