Modeling And Predict Conducted Noise Cumulative Effect In Parallel Inverters

The current power system always has multiple different power electronic converters inevitably.And when they are connected in parallel to the common bus,there will be a new problem: when multiple converters are connected in parallel,how the interference in the system is added together.This means that those power electronic converter producers whose products are uesd in power system,not only need to consider the electromagnetic emission of a single inverter,some times should also consider the influence of a group of converters' superimposed interference in the grid.In addition,some studies in the European Union have found that the random components of the system have an impact on its EMI.For example,the number of power electronic converters,the operation state of the grid or other factors will lead to the randomness of the interference.So,this paper takes the typical grid connected inverter as the research background.Considering the main random factors of the system,select an appropriate method of random simulation to study the rules and prediction method of the superposition of multiple inverters' conducted interference.Firstly,in this paper,the random characteristics modeling process of common mode interference of the system with multiple parallel inverters is analysed.And,MC method as a kind of random simulation method which is widely used and has the highest accuracy is uesd for simulation.Then,the main factors that affect the randomness of the interference in the system are analyzed.And through the combination of measurement and simulation,these factors are quantified and their random distribution are obtained.Then,the pridiction model of random common mode interference of parallel inverters are established in MATLAB.And do many times simulation according to MC method.After,through FFT,the probability distribution of common mode interference's spectrum is statistical analysed.Then,Effects of partial and all stochastic factors on interference characteristics are analysed.Futher more,observe the distribution of the interference at several selected frequency points,and analysis the results with the method of probability theory and mathematical statistic in detail.Next,investigate the stochastic characteristics of common mode interference in a system with multiple parallel inverters.Finally,in this paper,two grid connected inverters are designed.And,their overlay common mode interference is measured.Then,after changing some parameters,observe the change of its common mode interference and get its distribution to compare it with the predicted results to verify the simulation analysis.The background of this research is voltage type inverter that is widely used in power system,and the objection is its transient common mode interference.Through measurement and analysis,a parametric,hierarchical,accurate and flexible superimposed common mode interference prediction model is established systematically for a system with multiple parallel inverters.The development of the subject has a new attempt on the analysis of the propagation characteristics and the prediction of electromagnetic interference,and has a certain theoretical innovation and application value.