| Electric vehicles are widely used in the world,the related technical requirements of electric vehicles are also improved.The power source of the electric vehicle is the driving motor.During the driving process,the driving motor produces different levels of vibration and noise,which inevitably has a negative impact on the vehicle.Nowadays,inverter is widely used in driving control of electric vehicle.The research shows that when PWM inverter is used to drive PMSM,there will be concentrated harmonic voltage and harmonic current around its switching frequency and its integral times.The harmonic current caused by inverter makes the motor produce vibration and noise.In order to optimize the motor vibration and noise caused by inverter operation,this paper studies a new modulation technology,namely periodic frequency modulation technology.In this paper,the periodic frequency modulation technology is applied to the permanent magnet synchronous motor to study the influence of the technology on the harmonic current and vibration noise of the motor.In this paper,firstly,the causes of the current harmonics of permanent magnet synchronous motor(PMSM)with fixed switching frequency PWM modulation are analyzed theoretically,and the relationship between harmonic current and switching frequency is deduced;secondly,the periodic frequency modulation technology is introduced,the influence of periodic frequency modulation technology on current harmonics is studied,and the relationship between the modulation ratio of periodic frequency modulation and the spread spectrum width and current harmonics is deduced.Secondly,the simulation model of permanent magnet synchronous motor drive system is built to analyze the frequency spectrum of three-phase current modulated by fixed switching frequency PWM;the test platform of motor drive system is built to test,collect motor phase current signal and analyze the frequency spectrum.The comparison between the test results and simulation results shows that the current harmonics obtained by the test and simulation have the same characteristics and are consistent with the characteristics of theoretical analysis,which verifies the accuracy of the model.Then through simulation and experiment,the effect of periodic frequency modulation on current harmonic suppression is analyzed.The harmonic current modulated by sine wave,triangle wave,sawtooth wave and square wave periodic frequency is simulated,their spread spectrum effect is analyzed and compared,and the sawtooth periodic frequency modulation technology with the best harmonic current suppression effect is selected.On this basis,the current harmonic suppression by sawtooth periodic frequency modulation with different modulation ratio is compared.After that,the spread spectrum effect of sawtooth periodic frequency modulation in different spread spectrum width is analyzed,and the spread spectrum width with the best spread spectrum effect is determined.Then,based on the simulation optimization of motor harmonic current,the verification test is designed.The current harmonics obtained from the experiment are compared with the current harmonics obtained from the simulation,and the comparison results verify the accuracy of the simulation model.Finally,the vibration and noise test of motor is carried out,and the vibration and noise of fixed switch frequency PWM modulation and periodic frequency modulation are analyzed.The vibration and noise of fixed switching frequency PWM modulation and periodic frequency modulation with different modulation functions are compared and analyzed,and the vibration and noise of sawtooth periodic frequency modulation with different modulation ratio and spread spectrum width are compared.The test results show that the optimization scheme of periodic frequency modulation can effectively reduce the high-frequency noise of the motor and restrain the vibration of the motor. |
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