The electric vehicles are fast developed as the demand for energy conservation and environment protection. The permanent magnet synchronous motors (PMSM) are widely used in electric vehicles because of their high efficiency. However, due to the DC/AC inverter with fixed switching frequency was used to drive the PMSM, high-frequency vibration and acoustic noise were generated in the PMSM. And the frequency at which vibration and noise are generated is related to the switching frequency of the inverter and its integral multiple. Spread spectrum theory shows that the energies of a fixed high-frequency spectrum can be distributed into a wide range of frequencies. Therefore the concentrated energies can be weakened. This theory can be complied with the PMSM control strategy to help to reduce the high-frequency vibration and noise.

This paper presents control strategies with changing the switching frequency in order to reduce the vibration and noise of the electric motor. Firstly, four control strategies with different switching frequency: fixed switching frequency (FSF), periodic switching frequency (PSF), random switching frequency (RSF) and hybrid switching frequency (HSF) are modeled and simulated by MATLAB-Simulink. During this process of simulation, the influence from the modulate rate and spread width to the reduction of harmonic amplitude was detailedly analyzed. Secondly, these four control strategies are implemented by the dSPACE MicroAutoBoxⅡfor the rapid control prototyping (RCP) test. Thirdly, the vibration and noise tests of the PMSM are complied in the semi-anechoic chamber using software and devices from the LMS Test. Lab. Finally, the results of simulation and tests are compared and analyzed. Based on the simulation and test results, these three optimized control strategies can suppress the high frequency current harmonic amplitude significantly and the noise and vibration reduction difference among them are not apparently. Comprehensive analysis shows that the random and hybrid switching frequency control strategy proves to achieve better the goal of reducing the amplitude of high-frequency vibration and noise.

Ms. Lulu Wei, Jilin University, CHINA; Prof. Fangwu Ma, Jilin University, CHINA; Dr. Hongbin Yin, Shandong University of Technology, CHINA; Dr. Liang Wu, Jilin University, CHINA; Mr. Hui Gao, China Automotive Technology and Research Center Co., Ltd., CHINA