Research On CR400BF Vehicle-mounted Isolated Inverter Based On SiC Devices

In recent years,China’s high-speed railway industry is booming.In order to reduce the weight of the EMUs,lithium batteries with the advantages of lightweight,pollution-free and long life are applied to the auxiliary standby 110 V battery pack of"Fuxing"EMUs in the design of standard EMUs.Due to the special operation environment,high working temperature,dense distribution of various electrical equipment and narrow space on the train,the high-speed railway industry is facing a new challenge,It has higher requirements for the volume,efficiency and reliability of single-phase inverter.Aiming at the problems of large volume and low efficiency of the current vehicle single-phase inverter,combined with the narrowing of the input voltage range of the inverter caused by the lithium battery as the backup power supply,this paper improves the DC boost circuit of the traditional two-stage inverter with phase-shifting full bridge structure to a full bridge LLC resonant circuit,and introduces a new generation of power device SiC,which is easy to be used in high-frequency applications An experimental prototype of isolated single-phase inverter is developed based on MOSFET.Firstly,the overall architecture of the inverter system is designed,and then the modeling analysis,design,simulation verification,software and hardware system design of the front and back stages of the inverter are completed.Finally,the whole machine test of the experimental prototype is completed.The details are as follows:(1)Firstly,the steady-state modeling of the front-stage full-bridge LLC resonant converter is carried out,and then the steady-state DC gain characteristics and working process of the converter are analyzed,and the switch tube is deduced to achieve zero voltage turn-on(ZVS)in the full load range.Based on the boundary conditions,a design process of resonant cavity parameters was proposed.Finally,a simulation model was built on the Matlab/Simulink platform and the rationality and correctness of the design were verified.(2)The equivalent transfer function and equivalent block diagram of the main circuit are derived,and the output LC filter is designed.The double closed-loop control model based on inductor current sampling and output voltage sampling is adopted.Aiming at the problems of low output voltage precision,high harmonic content and poor dynamic characteristics of the double closed-loop control based on traditional PI controller,the control strategy is proposed A double closed-loop control strategy based on voltage outer loop of improved PR multiple composite controller and current inner loop of fractional order PI~λcontroller is proposed,and the controller design is completed.Finally,the simulation model is built in Matlab/Simulink platform,and the control effect is compared and analyzed,which verifies the advantages of the double closed-loop control strategy based on improved PR multiple composite control and fractional order PI~λcontrol.(3)Complete the design of hardware circuit and software system of the inverter,build the experimental platform to test the isolated single-phase inverter.The test results show that the isolated single-phase inverter designed has good steady-state characteristics,dynamic characteristics and high efficiency,which can meet the requirements of vehicle isolated inverter and has practical value.