Sensorless speed and direct torque control of surface permanent magnet synchronous machines using stochastic filtering techniques

The paper describes the development of a sensorless speed and direct torque control system for surface permanent magnet synchronous machines (SPMSM). An extended Kalman filter (EKF) is used for the stator flux and mechanical state estimation of the SPMSM. The observer was developed based on a nonlinear model of the synchronous machine that employs α-β stationary reference frame. The torque controller was designed taking into consideration a model of the machine in the rotating reference frame attached to the stator flux space vector. The electromagnetic torque and stator flux, are controlled by nonlinear hysteresis controllers; their output signals are used for generating the control signals of inverter, based on a switching table. The angular speed controller is linear of I + PI type.