Mitigation of Torque Ripple and Vibration in Switched Reluctance Motor Drives: A Switching Optimization

Abstract

Switched reluctance motor (SRM) drives represents an attractive solution for industrial, transportation and domestic applications due to their rugged structure, independence from rare earth metals, modular design, wide speed range, and tolerance to harsh environments. Despite these advantages, the adequacy of SRM drives for many applications has been overshadowed by its relative high levels of torque pulsation and vibration/acoustic noise. This research aims to investigate and propose control strategies to mitigate these adverse features. To reach this goal the current shaping and switching optimization have been proposed. Two modeling methods were used in this process: i) field reconstruction method (FRM) to model the electromagnetic behavior; and ii) mechanical impulse response to model the structural behavior. This two-modeling procedure are the key innovative tools in this dissertation, since those are techniques recently proposed in the literature. Moreover, these two methods have been combined to simultaneously mitigation of torque ripple and radial vibration. Firstly, the structural vibration was investigated in detail for an 8/6 SRM. The modal analysis is carried out experimentally and through finite element model in ANSYS. Then, the mechanical impulse response concept was applied to develop a vibration prediction model that, after validated, was introduced in an optimization algorithm developed in MATLAB to design the precise switching instants to have active vibration cancellation. The method is focused on SRM operating under current control (low speed region). The experimental results show a significantly reduction. This technique is sensitive to timing without adverse impact on productivity and efficiency of the SRM drive. Moreover, the vibration mitigation also has contributed to acoustic noise reduction. In a second approach, an optimization based on the SRM model using the FRM is used to find the optimal current profile that mitigates the torque ripple. The percentage reduction reached is about 44%. Furthermore, the effect of the new current profile in the structural response is also investigated and a negative impact in the vibration has been observed. To deal with this shortcoming, an adaptive hysteresis band is implemented over the optimized current profile for torque ripple mitigation. The obtained results demonstrated a good compromise between the torque ripple and vibration mitigation.