Torque Performance Improvement of Doubly Salient Synchronous Reluctance Machines by Current Harmonic Injection

In this paper, a current harmonic injection method is proposed for torque ripple reduction and/or average torque enhancement in 3-phase, 12-slot/8-pole single layer mutually coupled switched reluctance machines (MCSRMs), which are essentially doubly salient synchronous reluctance machines with sinewave current supply. Initially, the torque generation mechanism with pure sinewave current supply of MCSRMs is analyzed based on some analytical torque models with both self- and mutual- inductances consideration. These analytical models can accurately predict which inductance harmonic(s) contribute to average torque and which contribute to torque ripple and to which extent their contribution will be. Using similar analytical torque models, the current harmonics (3rd, 5th, 7th, etc.) can be injected to reduce the torque ripple and/or to increase the average torque. In addition, the harmonic order, the amplitude and also the phase angle compared to the fundamental component can be calculated for achieving the minimum torque ripple or the maximum average torque. Both finite element simulations and static as well as dynamic tests have been carried out to prove the efficiency of the proposed current harmonic injection method.