Bandwidth and Audible Noise Improvement of Sensorless IPMSM Drives Based on Amplitude Modulation Multirandom Frequency Injection

The high-frequency (HF) signal injection method has been widely used in sensorless control for IPMSM drives. However, the audible noise caused by HF injection restricts the sensorless application. Moreover, the control bandwidth of systems based on sinusoidal multifrequency injection or variable-frequency injection for audible noise reduction is limited due to the need for filters. This article proposes a novel amplitude modulation multirandom frequency injection (AMMRI) method to improve control bandwidth and reduce audible noise. First, the detailed message signal modulation, error extraction, position tracking, and position estimation error compensation based on amplitude-modulated voltage signal are derived and analyzed. Because the filters for HF current and error extractions are removed, the control bandwidth is improved. Second, in order to reduce audible noise, the proposed AMMRI is derived by selecting the message signal according to equal-loudness contour. The proposed method improves the control bandwidth compared to conventional multifrequency injection and reduces audible noise compared to conventional square wave injection. Finally, experimental results verify the proposed method on a 1.5-kW IPMSM platform.