Sensorless speed control of synchronous reluctance motor using a novel flux estimator based on Recursive Fourier Transformation

This paper proposes a sensorless control of SynRM (synchronous reluctance motor). It can calculate the motor flux from an armature voltage and a current directly. The proposed estimator is able to eliminate both the dc offset and harmonic component of the armature current which cause the estimation error. State observer based Fourier Transformation called RFT (Recursive Fourier Transformation) is effective to estimate the fundamental component of the flux. Also a block pulse approximation is used to convert a continuous time state equation to a difference equation to reduce the calculation time. The validity of the proposed method is shown in the experimental results.