A Novel Dual Random Scheme in Signal Injection Sensorless Control of IPMSM Drives for High-Frequency Harmonics Reduction

By injecting a high-frequency square-wave voltage (HFSV) signal into the d-axis in the estimated rotor reference frame of an interior permanent magnet synchronous motor (IPMSM), the rotor position can be accurately extracted at the zero-low speed domain. However, since the voltage expected to be applied to IPMSM must be modulated by the pulsewidth modulation (PWM) technology, two types of HF harmonics, i.e., HFSV injection (HFSVI) harmonics and PWM harmonics will generate HF audible noise in low-switching-frequency applications. Therefore, this article proposes a novel dual random scheme in the HFSVI sensorless control of IPMSM drives to significantly reduce HFSVI harmonics and PWM harmonics. The proposed dual random scheme performs random phase signal injection (RPSI) and N-state random zero-vector distribution (NSRZVD) at the same time. By applying 2-D Fourier analysis, it is found that RPSI significantly reduces HFSVI harmonics, and NSRZVD reduces both PWM and HFSVI harmonics, respectively. When performing RPSI and NSRZVD at the same time, almost all HF harmonics are significantly reduced, thereby reducing HF vibration and audible noise. Experiments conducted on an IPMSM sensorless control system verify the effectiveness of the proposed dual random scheme at last.