Research On Modeling Method Of Converter Based On Harmonic State Space

The traditional average modeling method ignores the harmonics of the system,and therefore cannot accurately analyze the dynamic harmonics change and the interaction of harmonics.Thus,it is an important but difficult endeavor to establish an accurate model which accounts for the harmonics of the system in order to study the harmonics behavior and the harmonics interaction mechanism of the system.As a result,harmonic state space(HSS)modeling has gained greater attention because of its powerful harmonic analysis ability.However,the complex modeling process and large model size limit its application in power electronic systems.In order to solve this problem,this thesis is an in-depth study on converter topology and modeling methods,as well as the current status of harmonics research domestically and abroad.Through a comparative analysis of current common converter modeling methods,the superiority and necessity of converter modeling based on the principle of the HSS modeling methods are established and summarized.Furthermore,the problems and difficulties of HSS-based converter modeling is also studied.In addition,the theoretical basis of HSS modeling method is studied in detail,and a passive component modeling based on HSS is realized,which lays the foundation for the application and research of HSS modeling method.In this thesis,a three-phase voltage source converter based on SPWM is taken as an example,and a method to obtain the analytic model of switching function by calculating the switching time is proposed.Based on the analytic model of switching function,a HSS model of the converter is established.Based on the three-phase equilibrium relationship,the HSS model is simplified,and the HSS model is proposed to reduce the size of the model without affecting the modeling accuracy.By building the converter simulation in Simulink,the accuracy of the proposed switching function analytical model and HSS order reduction model is verified by comparing with the calculation results of the proposed switching function analytical model,HSS model and its order reduction model.The results show that the error between the proposed switching function analytical model and the actual switching function is less than 0.001%.The HSS order reduction model is completely consistent with the calculation results of the original HSS model.Under the maximum harmonic number set in this thesis,the calculation speed of the HSS order reduction model is nearly 220 times higher than that of the original HSS model.Moreover,with the increase of the maximum harmonic number considered by the model,the simplification effect of the HSS order reduction model will be more obvious.