Bi-switching Status Model Of DC-DC Converter Based On Mixed Logical Inequality

The model of power electronic converter is the basis of the research on the characteristics and control strategy of converter system.However,the power electronic converter is a switched system which contains continuous state variables and discrete switch variables.The main modeling methods for power electronic converters are state space averaging method and the discrete mapping modeling method.The converter model obtained by the state space averaging method is a reduced-order model.But it is an approximate model.The discrete mapping model is more accurate than the state space averaging model,but the modeling process is very complex if the converter contains multi-mode operations.Therefore,the converter modeling method is an important research direction of power electronics technology with far-reaching significance,and it depends on the new mathematical modeling method.According to the operating characteristics of the power electronic converter,it has important theoretical value and practical significance to carry out the research on the model of the power electronic converter.The following innovation points are carried out in this paper:(1)Bi-switching status modeling method for DC-DC converter modeling is proposed.Based on the mixed logical dynamical modeling method,the relationship between the equivalent transformation of the logical proposition and the mixed logical inequality is given.According to the characteristics of the operating mode of the power electronic converter,the constraint conditions of the DC-DC converter in different operation modes are transformed into mixed logical inequalities.Therefore,the model of DC-DC converter with 2,3 or multiple operating modes is constructed,named a bi-switching status model,which has only two operating modes.The proposed model has a unified representation form with clearly physical meaning,and no simplified assumption.It is also suitable for the large signal and small signal analysis of the DC-DC converter.(2)Bi-switching status model of the basic DC-DC converter with 2 or 3 operating modes is established.According to the modeling method of bi-switching status model,the constraint conditions of Buck and Boost converter in CCM and DCM operation modes are transformed into a mixed logical inequality.And the bi-switching status model of Buck and Boost converters operating in CCM and DCM are built.It is further verified that the modeling processes of the basic DC-DC converter in CCM and DCM via bi-switching status model are exactly the same and this model can accurately describe the characteristics of the converters.The correctness of bi-switching status model is testified by the simulations and experiments of Buck and Boost converters under different load conditions.Compared with the commonly used Simulink model,state space averaging model,improved averaging model and averaged switch model,bi-switching status model has higher accuracy.(3)Bi-switching status model of DC-DC converter with multiple operating modes is established.First,according to the working principle of the ZVRT Buck converter,the mixed logical inequalities for the constraints of the ZVRT Buck converter are given,and then the bi-switching status model is established.The simulation and experiment results show that the bi-switching status model of ZVRT Buck converter can accurately reflect the zero voltage switching process of the converter,and the dynamic process is consistent with that obtained by the experiment.Therefore,bi-switching status modeling method can be used for modeling the soft switching DC-DC converter.Second,bi-switching status model for three-level Buck converter is built.The analysis of simulation and experiment illustrates that the bi-switching status model of three-level Buck converter can accurately reflect the characteristics of multilevel converter.The consistence of dynamic process of the simulation and experiment indicates that bi-switching status modeling method can be used for modeling multilevel DC-DC converter.In this paper,the new proposed bi-switching status model of DC-DC converter is proved to be a kind of modeling method of power electronic converter based on the new mathematical method.And bi-switching status model can accurately describe the static and dynamic characteristics and operating characteristics of the DC-DC converter.Moreover,it can be further applied to model and analyze other types of power electronic converter.