Sensorless speed and direct torque control of interior permanent magnet synchronous machine based on extended Kalman filter

The application of vector control techniques in AC drives demands accurate position and speed feedback information for the current control and servo-control loops. The paper describes a digital sensorless speed control system for interior permanent magnet synchronous machines (IPMSM). A Kalman filter is used to estimate the mechanical state of the motor. The observer was developed using a nonlinear model of the synchronous motor based on a d-q rotating reference frame attached to the rotor. The stator flux and electromagnetic torque are controlled by nonlinear hysteresis controllers; their outputs are used to generate the control signals for the inverter, based on a switching table. The angular speed controller is linear, of integral + proportional integral (I + PI) type. The paper studies the interaction between the observer and the closed loop control system. The simulation shows that the dynamic behaviour of the Kalman filter based control system is good even if the electric and mechanical parameters of the machine are different from the rated values used for the design of the controllers and the Kalman filter and also if there is an incorrect initialization of the estimated position.