Self-Sensing Torque Control of an IM Drive with Instantaneous Phase-Voltage Sensing

Self-sensing torque control of induction machine drives without dedicated speed transducer is based on detecting the voltage induced by the rotating magnetic field into the stator windings. Due to the inverter voltage distortion, stable operation is only possible above a certain field angular frequency where a sufficient signal-to-noise ratio is present. The stable operating region can be extended to lower frequencies by application of dedicated phase-voltage sensing instead of using the inverter reference voltage. In this paper, a gate-driver-integrated instantaneous phase-voltage sensing circuit is used for precise detection of the stator flux-linkage vector at very low stator frequency. Experimental results show improved self-sensing torque control of an induction machine for automotive traction applications. The direct field-oriented torque controller is stably operated down to zero rotor speed.