An Improved Direct Instantaneous Torque Control of Two-Segment Twisted-Rotor Doubly Salient Motor for Torque Capability Enhancement

The direct instantaneous torque control (DITC) method is an effective way to suppress the torque ripple of doubly salient motor (DSM). However, there is the inevitable phase current peak in the conventional DITC method, which increases the current stress of the power switches and degrades the torque capability of the DSM. In this article, an improved DITC method is proposed based on the optimal torque sharing ratio. First, the maximum torque characteristics of two-segment twisted-rotor DSM are obtained through the finite-element method. The optimal torque sharing ratio and the ideal phase current waveform are deduced based on the maximum torque characteristics of two parts of two-segment twisted-rotor DSM, which have 180° electrical angle difference. Then, by sharing the total reference torque to two parts according to optimal torque sharing ratio, the operation principle of the proposed DITC method is derived. Finally, the proposed DITC method is implemented on the 12/8-pole two-segment twisted-rotor DSM drive system. The performance of the proposed DITC method under different commutation angle parameters, different speeds, and reference speed step change are demonstrated through experimental results. The experimental results indicate that the proposed DITC method can suppress the peak current and enhance the torque capability of two-segment twisted-rotor DSM while guaranteeing low torque ripple operation.