Improvement of Sensorless Control for Permanent Magnet Synchronous Motors with Simultaneous Identification of Inductance Based on Pseudo-Random Square Wave Injection

As for sensorless control of permanent magnet synchronous motors, various methods based on high-frequency signal injection have been widespread studied. However, with the increasing switching frequency, as well as the injection frequency for better control performance, sharp acoustic noise and electromagnetic interference becomes an issue that cannot be ignored, since the frequency of the signal concentrates on a narrow audible region. Therefore, a novel injection method using high-frequency pseudo-random square wave is proposed in this paper, aiming to effectively decrease high-frequency noises, while maintaining the accuracy and dynamics of sensorless control. Simultaneously, d-axis incremental inductance can be identified in real-time during this process. The corresponding signal demodulation realizes estimation of rotor speed and position by means of a Luenberger observer in stationary reference. Finally, the proposed sensorless control method is verified by simulation. And the power spectra density in fixed frequency and pseudo-random frequency injection schemes are compared.