| In the traction power converter system, the junction temperature of the power device is an important factor affecting the performance of the converter and even the whole system. In this paper, taking the engineering application as the background, the job is to calculate the junction temperature changes of the traction converter power device combined with the actual operation data of the train. It is of great significance for the selection of converter power devices, life assessment, the thermal design of converters and so on. The specific research contents are as follows:Firstly, the basic theory of the heat transfer is introduced, and the structure and working principle of the heat dissipation system of the traction converter are systematically classified and summarized. And the calculation formula of its thermal resistance is deduced for the different structure of the traction converter radiator, based on the definition of the heat transfer equation and the unit division method.Secondly, the method of’ calculating the power loss based on the interpolation method of the power device data manual is introduced in detail. Combined with four-quadrant pulse rectifier bipolar sinusoidal carrier modulation (SPWM) algorithm, the calculation process of the power loss of the power device is analyzed and its formula is deduced. Combined with the two-level traction inverter’s all-speed and multi-mode space vector pulse width modulation (SVPWM) algorithm, the calculation process of the power loss of the power device is analyzed and its formula is deduced. According to the parameters of the traction converter system in a domestic EMU, the relationship between the power loss of the power device and the train speed is given.Then, the junction temperature of the power device is analyzed and studied. The definition of transient-state junction temperature is given which is different from its steady-state junction temperature. Based on the method of the equivalent thermal path, the steady-state junction temperature model of the converter power device is established. The relationship between the steady-state junction temperature of the power device and the train speed is given according to the parameters of the traction converter system in a domestic EMU. Based on the method of centralized parameter, the transient-state junction temperature calculation model of the power device is established. The relationship between the transient-state junction temperature of the power device and the running time of the train is given according to the details of the operation of a city rail in Xi’an.Finally, this paper analyzes the simulation model based on PLECS software. The validity, feasibility of the calculation method and correctness of the calculation results is verified by the simulation results. |
