A sensorless speed estimator for application in a direct torque controller of an interior permanent magnet synchronous motor drive, incorporating compensation of offset error

This paper presents a sensorless technique for speed estimation of a direct torque controlled (DTC) interior permanent magnet (IPM) synchronous motor drive. The proposed method uses a new speed estimator from the stator flux linkage vector and the torque angle δ. It is shown that by including the torque angle in the estimation process results in a more accurate transient speed estimator than what is reported in the existing literature. The offset error causes the torque of a motor to oscillate and these torque ripples deteriorate the performance of the speed estimator. In order to eliminate ripples in the estimated speed, compensation has been made using a programmable cascaded low pass filter. Results from modeling and experiment verify the effectiveness of the sensorless speed estimator and offset error compensator.