Integration of Improved Flux Linkage Observer and I–f Starting Method for Wide-Speed-Range Sensorless SPMSM Drives

This article aims to improve the sensorless control performance of surface-mounted permanent magnet synchronous machine drives in the whole speed range. Based on the thought of speed partition optimization and smooth transition, a hybrid sensorless control strategy integrating with an improved flux linkage observer and the current-frequency (I-f) starting method is proposed. At zero-low speed, the I-f control method is utilized for the stable startup and strong antijamming capability. At medium-high speed, an improved flux linkage observer based on the sliding-mode compensator is designed for the closed-loop sensorless operation. Taking advantage of the sliding-mode compensator, not only the position estimation errors caused by the adopted filter can be compensated effectively without any speed iteration to improve the system stability, but also the suitable cutoff frequency of the filter can be selected for the fast system dynamic response. Meanwhile, the influence of machine parameter variations on the rotor-position estimation accuracy is discussed. Furthermore, in order to achieve the smooth operation between two different control schemes, an adaptive transition algorithm is described in detail. Experimental results indicate that the proposed hybrid sensorless control strategy can show an excellent performance for both steady-state and dynamic operations during full-speed range.