| Safety and reliability of power electronic system has become an important purpose of power electronics system research,as power electronic technology is now developing toward higher power and higher integration.In the research of sneak circuit of power electronic converter,the topology and combination mechanism of the switch circuit are first discussed based on graph theory,a new approach to reliability analysis of power electronic system based on topological operation rules is presented.It is found that the study of sneak circuits of power electronic converters can not only be applied to the analysis of power electronic converters with lumped parameters,but also can be applied to the study of power electronic converters with parasitic parameters.Therefore,in order to adapt to the increasingly complex operating environment of power electronic systems and circuit design needs,improve the reliability of the system effectively,the sneak circuti mechanism and characteristics of DC-DC converter caused by parasitic parameters are discussed is this thesis.The main contributions of this thesis are listed as follows:(1)Taking several basic DC-DC converters as the research object,build their parasitic parameter topologies.The concept of dynamic characteristics of sneak circuit is introduced after analysis and comparison of the lumped parameters topology and parasitic parameters topology of DC-DC converter.Hence,lay the groundwork for the sneak circuit mechanism and characteristics analysis of DC-DC converter with parasitic parameters.(2)The sneak circuit phenomena caused by parasitic parameters in DCM Boost converter is studied.The sneak circuit modes caused by parasitic parameters are analyzed.The state equation which includes both normal operating mode and the potential operating mode is established,then the excitation conditions of sneak operating cases are obtained.The mechanism and characteristics of sneak circuit caused by parasitic parameters are analyed.It is found that the parasitic parameter is the primary inducement of the sneak circuit in Boost DC-DC converter,it affect the normal operation and operating characteristics of the converter.(3)In order to suppress the negative effects caused by sneak circuits,the optimized circuit parameter design method and component selection based on the sneak circuit analysis method are proposed.It is found that oscillation caused by sneak circuits can be suppressed effectively by optimizing the parameter design and reasonable selection of components.Thus reduce the parasitical effects.It is a new method to sup provides a new method to suppress sneak circuit phenomena.(4)The above analysis method is extended to other types of DC-DC converters,such as Buck,Zeta,flyback converters.Sneak circuit effects,the corresponding suppression methods are proposed and verified.The results show that the parasitic parameter also is the primary inducement of the sneak circuit in Buck,Zeta,flyback DC-DC converters,the proposed method is a method with general applicability.(5)The sneak circuit analysis method considering parasitic parameters is used to the topology optimization of soft switching converter.Taking ZVT-PWM-Boost converter as the research object.The sneak circuit mechanism and characteristics of the converter considering parasitic parameters is analyzed,meanwhile,the corresponding sneak circuit suppression strategy is proposed,and combines the characteristics of the converter,topology optimization method is derived by removing or building new sneak circuit paths.Simulation and experiment results shows that the sneak circuit phenomena is suppressed effictivly based on the method obtained above,hence,the soft switching environment and the distortion degree of circuit waveform are greatly improved.Therefore,this method not only has a guiding significance for the topology optimization of power electronic converters,but also provides a new research idea for the construction of new power electronic converter topology. |
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