Torque Ripple Suppression Method based on FOC for SRM without FEM analysis

This paper proposes a torque ripple suppression method for a switched reluctance motor (SRM) with only measurable parameters. A large third-order torque ripple is generated by a conventional method with constant dq0-axis current, which is dq-axis current and zero-phase current converted from the three phase current of SRM. Moreover, the conventional method assumes an inductance profile constant regarding a change in the current. In the magnetic saturation region, the inductance decreases at an aligned position. Thus, an effect of the torque ripple suppression method becomes low and the average torque cannot be controlled in the magnetic saturation region. The proposed method derives the zero-phase current with the third-order harmonic in order to suppress the torque ripple from a torque equation considering spatial harmonics of the inductance profile up to the forth order and torque/current ratio in whole region. In addition, an average torque control is proposed for the magnetic saturation region. The average torque equation is derived from the inductance expressing the magnetic co-energy at the magnetic saturation. As a result, the experiments demonstrated that the torque ripple is reduced by 76.1% in the linear region and by 73.4% in the magnetic saturation region compared to the conventional method with the constant dq0-axis current. Moreover, the derived average torque equation agrees with the experimental results including the error of 3.9%.