Indirect Instantaneous Torque Control for Switched Reluctance Motor Based on Improved Torque Sharing Function

Abstract

Switched reluctance motors (SRMs) have recently gained notable interest in industrial applications. Yet, their inherent torque ripple poses a significant impediment, limiting the adoption of SRM in high-performance applications. Instantaneous Torque Control (ITC) based on conventional Torque Sharing Function (TSF) is considered a promising technique for torque ripple reduction of SRMs at low speeds. However, the back electromotive force is increased with speed escalation, reducing torque tracking ability to its reference in the ITC based on conventional TSF, especially in the demagnetizing period. The high inductance value in this period opposes phase-current decaying, generating considerable torque ripple, making the ITC unsuitable at medium and high speeds. This paper proposes the indirect ITC based on an improved TSF to address the torque ripple over extended speed for SRM drive. The improved TSF relies on predicting the outgoing phase torque in the demagnetizing period and compensating for the difference between the predicting and reference torque in the next excitation phase by reshaping the incoming phase torque, minimizing the torque ripple. Moreover, simple analytical formulas are used to regulate the control angles to gain further improvements and extended speed. An accurate nonlinear motor model is created based on static magnetic characteristics estimated by the finite element analysis. Several simulated results are conducted to evaluate the effectiveness of the proposed controller. The proposed method offers higher torque ripple mitigation with the speed increase, decreasing the torque ripple by 10% to 45%. Furthermore, the proposed control reduces copper losses and enhances efficiency and torque/current ratio.

Keywords

• Indirect instantaneous torque control
• switched reluctance motors
• torque sharing function
• finite element analysis