Analysis And Suppression Of Electromagnetic Interference In DC/DC Convertor Systems Of Parallel-series PHEV

At the present stage of rapid economic development,the energy issue is getting more and more serious.New energy sources have gradually became the strategic goal of China's energy.At present,a lot of fuel cars are used in China for a long time.Exacerbated the problem of non renewable energy consumption and environmental pollution.In order to relieve the pressure of non renewable energy,new energy sources vehicle to become the main direction for future development of vehicles.Parallel-series PHEV(Plug-in hybrid electric vehicle)as the most used new energy vehicle,which not only makes full use of the power resources of our country,but also improves the environmental pollution remarkably.It has a broad market application background.Compared with traditional internal combustion engine vehicles,a large number of power electronic devices are added to the parallel-series PHEV,which brings serious electromagnetic compatibility problems while improving the efficiency of electric energy utilization and reducing the practical cost.DC/DC convertor system is an important energy conversion system in PHEV.The EMI(Electromagnetic Interference)generated during operating seriously affects the normal operation of electrical system and electronic components,and safe driving of the vehicle is planned.In this thesis,the EMI problem in DC/DC convertor system of parallel-series PHEV was studied,mainly from the following aspects:(1)The system structure and working principle of DC/DC convertor are analyzed,the mechanism of EMI generation and source of electromagnetic interference are studied.Partial circuit topology and EMI coupling path in PHEV are analyzed,the impact of coupling path on electromagnetic interference was researched theoretically.(2)The DC/DC convertor system is replaced by module processing and establi-shed high frequency equivalent circuit model such as LISN(Line Impedance Stabilization Network),input cable and parasitic capacitance,and the related parameters of the model are calculated.The high frequency model is integrated to build the system conducted EMI simulation prediction model and simulate under MATLAB/Simulink,the obtained transmission interference spectrum map is analyzed.(3)The suppression method of conducting EMI in the DC/DC convertor system is studied.From considering electromagnetic interference source,a phase-shifted ZVS-DC/DC full-bridge convertor with active clamp is designed.Passive compensation circuit structure that based on the principle of passive compensation is devised,which can compensate for the common mode interference current which passing through the parasitic capacitance in the system.Thus,the propagation of common mode interference is suppressed.The conducted electromagnetic interference suppression is simulated and the correctness of the suppression measures is explained.(4)The cause of radiation EMI and the sources of radiation interference in the DC/DC convertor system are analyzed.On the basis of the unit dipole,the double-loop model of radiated interference of the convertor system is established and simulated.The shielding principle of electromagnetic interference is introduced.Using shielding and floating point grounding measures to suppress parallel-series PHEV DC/DC convertor system radiation electromagnetic interference,the whole model is built and simulated in HFSS,and the effect of electromagnetic shielding is verified by simulation analysis.