Research On Electromagnetic Radiation Characteristics Of DC/DC Converter For Electric Vehicle Under Multi-directional Coupling

With the development of electronic information technology, electronic devices is taking a more and more important part in the vehicles. The electromagnetic environment inside the vehicles has also become very complicated. In order to ensure the normal operation of the electronic equipment, and avoid the interference, it is necessary to control the emission of electromagnetic radiation. The anti-interference ability of electronic components should also be improved. As the main method to solve the problem of electromagnetic interference, electromagnetic compatibility has been paid more and more attention, gradually become the focus of research.The DC/DC converter is a key component for the power system of the electric vehicle, and its input/output power lines may generate a large amount of electromagnetic radiation. Therefore, this thesis takes the DC/DC converter as the research object. And the simulation methods of the electromagnetic radiation characteristics and the restrain methods of the radiation for the DC/DC converter system is studied. The specific research contents are as follows:(1) Based on the transmission line matrix method, a modeling and simulation method for the electromagnetic radiation of the DC/DC converter system is proposed.Firstly, the electromagnetic radiation simulation model of the DC/DC converter system is established. And the transmission line parameters of each unit length are calculated by dividing the cables into grids. After that, each segment is transformed into an equivalent circuit. The excitation signals loaded into the cable flows through such an equivalent circuit, so that the distribution of current is calculated. Finally, the current distribution obtained by the circuit simulation is taken as the excitation source, and the 3D electromagnetic field is calculated by combining the established system three-dimensional model. The simulation analysis of the electromagnetic radiation characteristics of the DC/DC system is completed.(2) The electromagnetic compatibility test for the DC/DC system is carried out according to the national electromagnetic compatibility standard GB18655-2010. First,the test platform is built in the half wave anechoic chamber, and the radiation field value of the DC/DC system is obtained by test. Then, the simulation results are compared with the test results, which proves the correctness of the modeling and simulation methods.(3) In order to solve the problem of overproof radiation in DC/DC system, the methods of suppressing cable radiation are studied and some relevant suggestions are put forward. Firstly, the mechanism of cable radiation and cable shielding is studied.Then, the screening effectiveness of different shielding layer, different shielding mode,and different pitch of twisted pair cables are compared. And the method of reducing system radiation is put forward from the view of improving shielding effectiveness of cables. Thus, from the aspect of cable shielding, this paper put forward some solutions to reduce the radiation. In the end, the principle of using magnetic ring, filter and common mode choke to suppress cable radiation is studied, which provides theoretical guidance for engineering practice.