Modeling Of Conducted Electromagnetic Interference In Power Converter

This thesis devoted to research on modeling of conducted electromagnetic interference of power converter. At first, this thesis studies the converter conduction mechanism of electromagnetic interference from two aspects of the interference sources and interference path; establishes the relevant model of EMI. The main works of this thesis are:1. Models to predict the common mode (CM) and the differential mode (DM) noise source of PWM converter is presented with asymmetric regular sampling modulation. A direct calculation method in frequency domain is proposed for the deduction of frequency spectrum of noise source. The distribution of CM and DM noise around the switching frequency and its multiple has been summarized to compare the changing relation of the interference between different modulation ration. Some patterns of such change have been found. In addition, with software, the time domain simulation along with its Fourier transform of the conducted Electromagnetic Interference of a three-phase rectifier verifies the correctness of the analysis results of proposed predictive model using the frequency domain theory. The modeling method described can be readily extended to a three-phase PWM inverter.2. The the thesis presents a new approach for modeling of the conducted electromagnetic interference prediction for widely used converter systems. Coupling paths and mechanism of differential mode interference and common mode interference have been analyzed. Models to predict the high-frequency noise of PWM converter system are created. A direct calculation method in frequency domain is proposed for the deduction of frequency spectrum. A method is given for obtaining the parasitic parameters and topological structure of the model.3. On the basis of predecessors’research conclusion, simplified DM and CM EMI models on high frequency coupling paths had been established. Based on the preceding section about the conclusion of precision high-frequency coupling paths model, the rule of the whole EMI under multiple parameters’variation. Range of variation was found when the whole parameters within certain scope. Each parasitic parameters were analyzed respectively reference to this standard, and "impact factors" were summaried. Due to the influence of different frequency range and different paremeters is different from one another, dividited the parameters into groups, through rule table of impact factor. The results of the study show that the impact factor of DM EMI is different under different parasitic parameters, and the main parasitic parameters have big difference between eachother. Based on the corresponding quantitative analysis, a more accurate simplified interference prediction model set up finally.An experimental investigation of conducted emission from an actual high-power rectifier system is described.The experimental results show that the accurate of the model with parasitic parameters is higher than that of the model without parasitic parameters; And relative to the accurate model, reduce ratio of the calculation amount of the simplified model is higher than the loss ratio of calculation accuracy.