Random-Phase Signal Injection Combined With Random PWM for Low-Noise IPMSM Sensorless Drives

High-frequency square-wave voltage injection (HFSVI) along the d-axis of an interior permanent magnet synchronous motor (IPMSM) allows for precise rotor position estimation by demodulating the HF current variation. However, the use of HFSVI is limited by significant HF vibrations and noise. These HF harmonics include both HFSVI and pulse width modulation (PWM) harmonics. The proposed method addresses this through the integration of random phase square-wave voltage injection (RPSVI) with random zero-sequence voltage (RZSV) to effectively reduce the harmonics from both HFSVI and PWM, thereby reducing noise and vibration. At last, the effectiveness is supported by both theoretical analysis and experimental evidence.