| New energy vehicle industry is growing rapidly and permanent magnet synchronous motors(PMSM)are widely used as an important power source for new energy vehicles.Due to the influence of dead time,inverters and other factors,there are abundant harmonic currents during the operation of PMSM,which greatly deteriorate the vibration and noise performance and spoil the driver’s experience.It is therefore of great significance to study the impact of harmonic suppression strategies on the vibration and noise of PMSM.(1)The control model and harmonic current characteristics analysis of the PMSM.Firstly,a control model is established on mathematical model of PMSM,the causes and influencing factors of harmonic current are investigated;then,the analytical model of air-gap magnetic field is established using the vector superposition method,the electromagnetic force wave under the harmonic current is calculated,the direct test of permanent magnet magnetic field was carried out.The results show that there are harmonic components with a frequency of(6h±1)f_c in the phase current,causing an electromagnetic force of even times the fundamental frequency of the current;the modulation process of PWM introduces harmonic components with a frequency of mf_s±nf_c,causing an electromagnetic force of mf_s±(n±1)f_c.Where f_s is the inverter switching frequency,f_c is the current fundamental frequency,h,m and n are positive integers.(2)Research on harmonic current suppression strategies for PMSM.Low harmonics are identified and extracted in a synchronous nth d-q axis coordinate system,and harmonic voltage compensation is carried out.The compensation weakens harmonic currents such as the 5th and 7th that satisfy the(6h±1)th law.For high-frequency harmonics,a combination of zero-vector assignment and switching frequency variation achieves spread-spectrum modulation.The harmonic currents in high frequency range at the switching frequency and its multiples are attenuated.Using harmonic weakened three-phase currents as excitation,the radial electromagnetic force wave after harmonic weakening is calculated.The results show that the radial electromagnetic force wave at 4times and 6 times the fundamental current frequency is well attenuated by the low-frequency suppression strategy.After the weakening of the high frequency harmonic current,the radial electromagnetic force waves around the switching frequency and its multiples are well weakened and dispersed.(3)Experimental study of vibration and noise of PMSM.Comparing the common control strategy and the proposed control strategy,the motor vibration and noise under different speed and different load conditions were tested.The test results show that under the control strategy proposed in this paper,there is a significant reduction in the peak vibration acceleration of the motor;the noise near the radial switching frequency,radial doubling switching frequency,axial switching frequency and axial doubling switching frequency all have a significant reduction.The effectiveness of the control strategy proposed in this paper is verified. |
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