Noise Reduction Research On High Frequency Injection Based Sensorless Drive Technique Of Permanent Magnet Synchronous Motor

The permanent magnet synchronic motors(PMSM)play an important role in industry and household appliance field due to the high efficiency and high power density.In the field-orientated control technique,the rotor position is required for decoupling.The rotor position sensors increase the cost and reduce the reliability.Thus a series of sensorless drive schemes of PMSM have been proposed in the last decades.High frequency signal injection(HFSI)based sensorless drive method is effective in low-speed region.However,it also introduces acoustic noise and electromagnetic compatibility problems,which limits its practical application.In this paper,the noise reduction research has been made as follows.First,the mechanism of conventional HFSI method is analyzed.The high frequency model of PMSM is introduced,the motor can be regarded as inductors.The HF current contains rotor position because of the salient structure.The rotor position can be extracted through signal processing techniques.In this paper,the high frequency square-wave injection and the high frequency sinusoidal-wave injection is analyzed.These two methods are verified via Matlab/Simulink simulation platform.Based on the analysis results above,the random frequency injection method is researched in this paper.The conventional method uses fixed frequency signals,thus the power spectra density(PSD)concentrates at a single point,which leads to shrill noise.The random frequency injection method can extend the PSD distribution and reduce the spectra peaks.Based on this principle,the method to extract rotor position information from random frequency current is researched.In addition,the digital system time delay effect to the HF signal is introduced.The corresponding solution is proposed.The comparison between conventional fixed frequency injection and the proposed random frequency injection method is made in terms of the current PSD.Although the proposed method can extend the PSD distribution,some discrete component still exists in the spectra.A theoretical analysis regarding the discrete peaks is made in this paper and an optimization strategy is introduced.Both theoretical analysis and experimental results are provided,which can agree with each other well.The comparison of the spectral performance shows that half-period-switch injection scheme has continuous spectra and the electromagnetic and acoustic noises can be suppressed significantly.Finally,the method is verified via a 2.2-k W ARM based IPMSM drive platform.The experimental results shows that the proposed random frequency injection method can reduce the noise caused by HF signal effectively.This sensorless drive technique also has good control performance.