Improved sensorless control scheme for PMSM based on high-frequency square-wave voltage injection considering non-linear change of inductance in D-Q axis

Aiming at the position sensorless control system of permanent magnet synchronous motor (PMSM), an improved high-frequency square wave (HFSW) signal injection scheme considering nonlinear inductance variation in d-q axis is proposed and implemented in this paper. Compared with the existing model, the modified scheme can take the dynamic variation of d-q axis inductance under different operation conditions into consideration by offsetting the resulting high-frequency incremental (HFI) current harmonic components, thus effectively suppressing the estimation error of the rotor position. The experimental results verify that the improved scheme proposed in this paper can not only improve the estimation accuracy of rotor position impaired by the non-linear variations of d-q axis inductance but also maintain the good steady-state and dynamic performance of traditional schemes.