Research On Stochastic Pulse Width Modulation Technology With Chaotic Signal

As more and more high-power high-frequency power electronic devices are widely used in various fields,electromagnetic interference(EMI)problems become more and more serious.The random PWM modulation technique provides a new idea to solve this problem.The random modulation based on uniform distribution sequence and Chua's chaotic sequence shows different EMI suppression effects,but there are not many researches and analysis on the difference of modulation effects.In this paper,different Logistic chaotic sequences are obtained by changing the Logistic mapping parameters.Compared with the modulation effects of Chua's chaotic sequence and uniform distribution sequence,the research shows that the distribution law and variance of random sequences are the key factors affecting the random modulation effect.The logistic chaotic sequence has the largest variance and uniform numerical distribution,and have the best EMI suppression performance.Furthermore,the application of chaotic modulation in a wider frequency range is studied.At different switching frequencies,chaotic modulation exhibits better suppression of EMI performance,and the higher the frequency,the better the performance.Finally,the relevant experimental results verify the correctness of the research.The power density spectrum analysis of the random switching function theoretically demonstrates that the random modulation has the ability to suppress electromagnetic interference in the circuit,and this ability is related to the characteristics of the random sequence itself.In order to study the effect of random sequence on the random suppression of EMI performance,this paper uses Logistic chaotic sequence,Chua's chaotic sequence,uniformly distributed sequence and other random sequences with different distribution laws and numerical features to modulate and analyze the random modulation power spectrum of different sequences.Studies have shown that random sequences with larger variance generally have better EMI suppression,when the variance is the same,the random number distribution is more concentrated.In the high-frequency power electronic system with more obvious electromagnetic interference,the random modulation technique has been applied more,but the adaptability and effectiveness of the random modulation technique at relatively low switching frequency need to be further explored.This paper used the FFT analysis of random switching function to explain the causes of signal distortion caused by chaotic modulation at relatively low frequency and the solution is given.The characteristics of random modulation under different switching frequencies are studied.The results show that Logistic chaotic modulation still has good EMI suppression performance at low switching frequency,and its performance gradually increases with the increase of switching frequency.Finally,TMS320F2808 is used to generate multiple chaotic random PWM signals to be applied to single-phase inverter.The output signal power spectrum is analyzed.The experimental results are consistent with the theoretical and simulation results,which confirms the correctness of the conclusions.