Temperature Field Calculation And Heat Dissipation Optimization Design Of High Frequency Transformer

HVDC system uses bidirectional active bridge DC-DC converter to realize bidirectional flow of DC power.Among them,high frequency transformer is an important electrical component of DC-DC converter,and its high internal temperature will accelerate insulation aging.Accurate prediction of temperature distribution of high frequency transformer is helpful to its structure optimization and heat dissipation design.The main research work and achievements are as follows:(1)Taking a single-phase three winding high-frequency transformer with a working frequency of 5 kHz as the research object,considering the influence of temperature on the magnetic characteristics of nanocrystalline core,the co simulation of Maxwell and Icepak is realized by ANSYS Workbench,and the bidirectional coupling calculation of electromagnetic temperature fluid field of high-frequency transformer under rated working condition is carried out.Under the condition of natural air cooling,the hot spot of high frequency transformer is located on the center of the core column,and the hot spot temperature is 108.5℃.(2)According to the heat dissipation path of high-frequency transformer,the equivalent thermal circuit model is established,and the steady-state temperature distribution is calculated.By comparison,the results of the equivalent thermal circuit method are consistent with those of the multi physical field coupling numerical analysis method,which verifies the feasibility and accuracy of the equivalent thermal circuit model method to calculate the temperature distribution of high frequency transformer.(3)Aiming at the high frequency transformer in Zhangbei flexible DC converter station,COMSOL Multiphysics simulation software is used to calculate the temperature field fluid field and optimize the heat dissipation of multi high frequency transformer common box with SF6 gas filling.The influence of different vent layout and high frequency transformer stacking mode on heat dissipation is analyzed,and the heat dissipation structure of SF6 gas insulated high frequency transformer is optimized.Considering the power density and heat dissipation of multi high frequency transformers,the hot spot temperature and the average temperature difference between the inlet and outlet of two,three and four high frequency transformers are calculated respectively under different inlet velocities,and the most reasonable inlet velocity range is found.In addition,the optimization design of the external plate radiator is carried out,and the accuracy of the design scheme is verified by the finite element simulation.