A Smooth Switchover Method for Hybird Sensorless Control of IPMSM

A hybrid rotor position estimation strategy, consisting of a rotating high frequency (HF) injection technique applied in low speeds and a back electromotive force (EMF) based technique applied in high speeds, is designed in this paper for an interior permanent magnet synchronous machine (IPMSM). By this combination, the rotor position of IPMSM is allowed to be estimated from standstill to high speeds. To improve the operation performance during the switchover region from the low speeds to the high, a single phase locked loop (PLL) approach as well as a method switching in/out the high frequency signal are presented. The position error signal obtained from the high frequency injection scheme is combined with that from the back-EMF scheme to form a hybrid error signal driving the common PLL shared by these two schemes. In addition to the merit of smooth switchover, the observation accuracy is increased as well as the HF injection detrimental effects are relieved to some extent. The effectiveness is validated through experiments, and the improved performance is confirmed by comparisons.