An improved stator flux estimation for a variable structure direct torque controlled IPM synchronous motor drive using a sliding, observer

This paper presents improvements of the stator flux estimation for a variable structure direct torque controlled (DTC) interior permanent magnet (IPM) synchronous motor drive. A variable structure observer is proposed to estimate the stator flux linkage based on the IPM motor current model. Compared to open-loop estimator, the observer improves the performance of the IPM motor drive. The experimental results demonstrate that the proposed observer is able to deliver more accurate estimation than open-loop estimator both in the steady state and during transients. Performance of encoder-less operation at very low speed is enhanced significantly.