A Novel ROGI-PNSS Flux Observer Based Sensorless Control for PMSM Considering Negative-Sequence Disturbance

Sensorless control of permanent magnet synchronous machine (PMSM) not only is susceptible to DC offset, high-order harmonics and inverter nonlinearity, etc., but also affected by the negative-sequence disturbance, which is rarely considered in conventional rotor flux observers. To deal with these issues, a reduced-order generalized integrator (ROGI) flux observer with positive and negative sequence separation (PNSS) is proposed to reduce the influences of those undesired disturbances and thereby improve the position estimation accuracy. First, the frequency response of ROGI-PNSS to different components is analyzed through bode diagrams. Then, the flux observer based on ROGI-PNSS is structured to eliminate the negative-sequence fundamental disturbances and achieve smooth estimation of rotor flux considering the speed reversal operation. In addition, an adaptive frequency-locked loop (FLL) with integrated speed estimation is introduced, which not only can work under both positive and negative speeds, but also exhibit better speed estimation accuracy. Finally, the feasibility and effectiveness of the proposed sensorless control method are verified through experiments on a PMSM prototype.