Study On Vibration And Noise Reduction Strategy Of Induction Motor Based On The Random Modulation

With the rapid development of society, the inverter is dominant in motor control,therefore, more and more people pay attention to PWM technology of controling inverter. This control is based on the fixed switching frequency controling frequency inverter, so a high harmonic component is generated at the integral multiple of the switching frequency, the amplitude of these harmonic component is larger, this can cause the problem of motor electromagnetic noise, and then produces the high frequency noise, inconvenience to people’s lives. To solve this problem, the social majority scholars have given different solutions in these years.This thesis mainly studies the inverter fed induction motor as the control object, and control of asynchronous motors by applying different control strategies, the best control method to suppress the vibration noise is compared, and by adjusting the parameters in the control method, making the effect of the control strategy optimal, that is to say the amplitude of the output current is the smallest, so as to achieve a better effect of vibration and noise reduction. In this paper, the arrangement of contents are as follows:Firstly, this thesis introduces the development history of the variable frequency speed regulation motor and the causes and characteristics of vibration noise generated by the motor under the control of frequency converter, the common practice and deficiency of suppressing the vibration and noise of the frequency conversion motor are given, then detailed analysis of the basic principles of the traditional PWM technology and the development of improved random PWM technology based on the traditional PWM technology.Secondly, according to the different principle, including random switching PWM control strategy, random pulse position PWM and random switching frequency PWM control strategy,and technical principle of these control strategies were analyzed and compared, as well as the development of random modulation strategy in recent years, it is concluded that the random switching frequency control strategy is the most widely used random modulation strategy, and explains the advantages compared with the traditional SPWM control strategy.Thirdly, the methods of generating random numbers of software are introduced, and using Matlab programming generates random numbers, by comparing and analyzing gives themethod of generating optimal random numbers. Several methods for checking the random performance of random number are also analyzed in detail, and it explains the basic principle of Markov process and the Markov chain. and according to the principle building a Simulink simulation model, including the SVPWM module, motor module, inverter module, Markov chain module,and output spectrum analysis module etc. The traditional SVPWM and random SVPWM control strategy is analyzed by simulation, the analysis results show that adding two state Markov chain controling of asynchronous motor can achieve the effect of vibration and noise suppression.Finally, parameters of the Markov chain and random modulation strategy would be optimized, and writing Matlab main program, the optimal solution of the given parameter range is calculated by the simulation analysis, the harmonic of the current output spectrum is uniformly distributed in the whole frequency band, and the peak is reduced to the minimum.Compared with the traditional control strategy, optimizing the parameters of the control strategy to the control of asynchronous motor would be better in vibration and noise reduction.