Research On All SiC Auxiliary Converter Of Metro Train Based On Input-Series And Out-Parallel Structure

The auxiliary power supply system is an important part of the metro vehicles.With the rapid development of domestic rail transit industry,higher requirements are put forward for the power density and efficiency of auxiliary converters.However,traditional auxiliary converters based on silicon devices are difficult to achieve new breakthroughs in the above indicators.Silicon carbide devices have higher switching speed and lower switching loss and other electrical characteristics,which can greatly improve the power density and efficiency of the system when applied in the Metro Auxiliary Converter,and help to achieve the development goals of high efficiency and light weight of the auxiliary converter.This research focuses on the design of a high-power auxiliary converter prototype based on all SiC devices,aiming to optimize the system topology,improve the system power density and efficiency,and realize the successful application of all SiC devices in auxiliary converters.Firstly,in order to apply the 1700 V all SiC module to the 1500 V high-voltage auxiliary converter,the input series output parallel phase-shifting full bridge structure is adopted to reduce the voltage stress of the device and increase the output capacity of the system.According to the working characteristics of the phase-shifting full bridge soft switch,the principle of voltage oscillation of the rectifier is analyzed,and the combination suppression method of the primary side diode clamp and the secondary side RCD absorption is proposed.In order to realize the soft switch of the phase-shifting full bridge converter,the dead time calculation model is established,and the voltage oscillation model of the switch without the soft switch is established,which is verified by the PSIM simulation platform It is reasonable.Secondly,the control strategy of the current ISOP combined converter is compared and analyzed.According to the complex and tedious characteristics of the current control strategy,the dual loop control strategy of the input voltage sharing to understand the coupling is proposed,which reduces the design difficulty of the closed-loop controller,and the algorithm of the output current minimum ripple is introduced to ensure that the output current keeps the minimum ripple at all times,which increases the practicability of the control strategy The PSIM simulation platform completes the closed-loop simulation,and verifies the reliability and stability of the control strategy.Finally,according to the current development trend of the auxiliary converter,the performance index requirements of the system are put forward,and the hardware parameters of the prototype are designed.A full SiC auxiliary converter prototype is successfully developed.The reliable control of input voltage and output voltage of the ISOP system is achieved by the input voltage sharing double loop decoupling control strategy,and the control objective of minimum output current ripple is achieved.The soft switch of the system is realized by using the dead time calculation model proposed above.Under the input voltage of 1500 V,the efficiency of 70 kw DC converter is increased to 95.1%,the efficiency of 40 k W auxiliary inverter is increased to 99.2%,and the overall efficiency of the system is over 94%.The development and commissioning of the auxiliary converter prototype are completed.