Sensorless Control of SPMSMs Based on Nonlinear Flux Model and High Frequency Voltage Injection Method

For the sensorless control of surface-mounted permanent magnet synchronous motors (SPMSMs), the traditional pulsating high frequency square wave injection method exhibits poor position estimation accuracy under low-speed overload conditions, mainly due to neglecting the cross-coupling effects and nonlinear parameter variations of motor inductances in classical control models. To address this issue, this paper proposes a high-frequency injection method based on a nonlinear flux model. Firstly, a high-frequency square wave voltage signal is injected into the stator winding, and a high-frequency current response signal is separated. Then, the envelope of the high-frequency current response undergoes vector cross multiplication to compensate for terms related to cross-coupling effects. Finally, the position information of the rotor is obtained through the phase-locked loop. This paper also compares the traditional pulsating high frequency square wave injection method, the source of position estimation error and the reason of 'salient pole failure' are analyzed. Both simulation and experimental results validate the proposed method, which is simple and reliable, effectively reducing position estimation errors of SPMSMs under low-speed overload conditions.