Electromagnetic Spectrum Quantization And Performance Analysis Method Of Power Converters With Continuous Chaotic Pulse Width Modulation

With the increasing of power density of power electronic devices,electromagnetic interference(EMI)caused by power converters has become a key problem of the development of power electronic technology.Chaotic pulse width modulation(PWM)can suppress EMI noises in EMI sources,which has been widely concerned and studied.However,there are some problems in the application of chaotic PWM in the power converters.On the one hand,chaotic spectrum analysis and chaotic signals selection are still insufficient.There is no standard that can accurately measure the characteristics of spectrum distribution,which is not conducive to the selection of chaotic signals.On the other hand,there is still a gap in the research on the performance analyisis of power converters with chaotic PWM.The stability modeling and analysis,loss analysis and other problems related to the safe and stable operation of the converters have not been analyzed and solved.In view of the above problems of chaotic PWM,the following work were carried out in this paper.A spectrum quantization method for power converters with chaotic PWM is proposed.Firstly,the generation mechanism and conducted paths of conducted EMI in power converters are analyzed,and the equivalent circuit of conducted EMI is established to determine the voltage of interference sources.Secondly,the general realization method of chaotic PWM and the mechanism of EMI suppression are introduced.Then,based on the modulation principle of chaotic PWM and Fourier decomposition principle,the spectrum quantization method of EMI source is proposed,and the factor of influencing the spectrum distribution in chaotic PWM are analyzed based on the analytical expression of spectrum quantization.Finally,the correctness of the spectrum quantization method is verified by simulation and experimental results.An optimization method of EMI suppression with multi-scroll chaotic PWM is proposed based on the multi-scroll chaotic system.In order to solve the problem of spectrum spreading over a wide range with traditional chaotic PWM,a chaotic PWM based on multi-scroll chaotic system is proposed.Firstly,based on the chaos theory,the generation of multi-scroll chaotic attractor is realized.By sampling the chaotic attractor,the chaotic modulation signals are obtained,and the multi-scroll chaotic PWM is realized.Secondly,based on the analytic expression of spectrum quantization,the effect of chaotic signal characteristics on spectrum distribution is revealed.On this basis,a selection method of chaotic modulation signal is proposed for multi-scroll chaotic PWM.Finally,simulation and experimental results verify the EMI suppression effect with the proposed multi-scroll chaotic PWM in power converters,and the effectiveness of the chaotic modulation signal selection method is also verified.The proposed multi-scroll chaotic PWM can not only reduce the peaks of EMI more effectively,but also ensure the spectrum spreading range within the set frequency,thus the purpose of better suppression of EMI is achieved.A stability modeling and analyzing method for the power converters with chaotic PWM is proposed based on the describing function method.To solve the system modeling and stability analyzing problem of the power converters with chaotic PWM,a stability modeling and analyzing method is proposed based on describing function.Firstly,based on the principle of the describing function,a describing function model considering the chaotic change of switching frequency and the nonlinear characteristics of switching process is established.Based on this model,the critical stable state of the converter from stable state to unstable state is determined according to the stability criterion of the describing function method.Then,the stability range of chaotic PWM and traditional PWM is analyzed.Furthermore,based on the proposed stability analysis method,the influence of switch frequency offset on the stability range is revealed from the mechanism.Finally,the correctness of the proposed stability analysis method is verified by simulation and experiment.A loss estimation method for switching devices in the power converters with chaotic PWM is proposed.Based on the discrete loss calculation model,the loss of switching devices with chaotic PWM is calculated theoretically.Firstly,based on the loss calculation model and chaotic PWM principle,a loss calculation model for chaotic PWM is proposed.Secondly,according to the loss calculation model,the loss and temperature rise of chaotic PWM and traditional PWM with different switching frequencies and converter topologies are compared to reveal the influence rule of chaotic PWM on switching devices loss.Finally,the correctness of the loss calculation model is verified by experiments.The analysis results show that the influence of chaotic PWM on switching devices loss is very small,and the introduction of chaotic PWM control in the power converters does not require additional consideration of thermal design.To sum up,this paper is devoted to solving the key theoretical and technical problems in the application of chaotic PWM in the power converters,providing comprehensive theoretical guidance and technical support for the design and control of the power converters from the aspects of chaotic spectrum quantization,EMI suppression,stability modeling and analysis,loss analysis and so on.