Sensorless Control of IPMSM in Zero- and Low-Speed Regions Using Dual Random High-Frequency Square-Wave Voltage Injection to Reduce Audible Noise

To accurately estimate the rotor position of an interior permanent magnet synchronous motor (IPMSM), high-frequency square-wave voltage injection (HFSVI) method has been widely used in position sensorless IPMSM drives at zero-low speed domain. However, dominant HFSVI harmonics and PWM harmonics will generate audible HF noises, which limits the practical application of the HFSVI method. Therefore, a dual random scheme proposed in this article simultaneously performs random phase signal injection (RPSI) and random N-state space vector modulation with nine segments (RNSVM9) to significantly disperse HFSVI harmonics and PWM harmonics. Since the HFSVI signal and PWM scheme are ultimately reflected on the three-phase output pulses, this article applies two-dimensional Fourier analysis to the output pulses. The principle of HF harmonics cancellation is intuitively explained by extracting the harmonic dispersion coefficient from the derivation results. Mathematical analysis shows that the proposed RPSI-RNSVM9 scheme can significantly disperse HFSVI harmonics and PWM harmonics at the same time. Finally, experimental results verify that RPSI-RNSVM9 significantly disperses all HF harmonics and has a smooth spectrum.