Acoustic Noise Reduction Using Half-Period- Switching Pseudorandom Sinusoidal Injection With External Tangent Demodulation for Sensorless PMSM Drives

High-frequency (HF) acoustic noise is unavoidable when HF injection is adopted for sensorless permanent magnet synchronous motor (PMSM) drives, which limits the application on some occasions. This article proposes a novel acoustic noise reduction method using half-period-switching pseudorandom sinusoidal injection (HPS-PRSI) with external tangent demodulation. The superiority of HPS-PRSI on acoustic noise reduction over the conventional PRSI is comparatively evaluated in terms of the power spectral density of the HF current. Furthermore, a system-delay-tolerant external tangent demodulation method is proposed to remove the demodulation signal and filters. Therefore, enhanced acoustic noise reduction with higher injection frequency can be achieved. Finally, experiments are carried out on a platform of 2.2-kW PMSM drive to verify the feasibility and effectiveness of the proposed method.