Advanced Control Method for a Single-Winding Bearingless Switched Reluctance Motor to Reduce Torque Ripple and Radial Displacement

Because of the current commutation and the double-salient pole structure of single-winding bearingless switched reluctance motors (SWBSRMs), the torque and radial forces have large ripples when present control methods are used. In order to solve those problems, a novel solution is proposed in this paper, which can achieve direct torque control (DTC) and direct force control (DFC) simultaneously. With the hysteresis-loop control of torque and flux linkage, the power switches of converter can be directly controlled based on the proposed space voltage vectors. First, the basic space voltage vectors are transformed correspondingly to realize DTC for BSRMs. After that, considering the generation principle of levitation forces, the basic space voltage vectors are transformed into equivalent space voltage vectors to facilitate the implementation of DFC. As a result, the torque and levitation forces can be controlled at the same time only with the developed equivalent space voltage vectors. The complicated current control algorithm is not needed, which is necessary for conventional methods. Moreover, the levitation performance is improved with the proposed method. Experimental results show that the torque ripple and radial displacements of SWBSRMs can be reduced approximately by 80% and 29%, respectively.