Design Of SiC Based Electric Vehicle Inverter

Silicon carbide(SiC)power devices have excellent performance.The application of SiC power devices in electric vehicle inverters can significantly reduce the weight,volume and cost of the inverters,and improve the efficiency and performance of electric vehicle inverters.This paper designs and manufactures a high efficiency and high power density electric vehicle inverter based on SiC MOSFET.The main research contents include three aspects: selection and calculation of key components of SiC inverter,the design of DC busbar and the design of water-cooled radiator.Firstly,according to the actual requirements of the project,the important performance such as power level,power density and peak efficiency of the inverters in this paper are defined;secondly,five SiC power modules that meet the requirements are selected according to the power level for comparative analysis of loss,junction temperature rise,driving power and other dimensions,finally the one which is named as CAS300M12BM2 is used in this paper;Then,based on the analysis of the role of DC bus capacitor,the type,voltage withstand value,capacity of bus capacitor are selected and calculated;finally,according to the characteristics of high switching speed of SiC MOSFET,the driver chip selection and driver circuit design are carried out.The mechanism of switching oscillation and switching off voltage overshoot of SiC MOSFET in application is analyzed,which highlights the importance of low parasitic inductance DC bus design.Secondly,by comparing the parasitic inductance of different types of DC bus,it is determined that the DC bus of inverters in this paper is a stacked busbar;secondly,the relationship between parasitic inductance and the configuration size of stacked busbar is deduced.The relationship between parasitic inductance and connection point of capacitive electrodes on bus is analyzed by ANSYS Q3 D software.The conclusion that parasitic inductance of bus is lower when the arrangement direction of connection point of capacitive electrodes on bus is parallel to the current direction on bus is drawn.Based on this conclusion,the optimal DC stacked busbar scheme is designed and simulated.The basic heat transfer principle and the heat exchange process of the inverter system are studied;the form of water-cooled radiator in this paper is determined by comparing different heat dissipation modes;then the thermal resistance network ofthe inverter heat dissipation system is modeled,and the thermal resistance limitation of the water-cooled radiator is obtained;furthermore,the thermal resistance of the radiator is deduced theoretically and deduced on the basis of the deduction.The appropriate size of water-cooled radiator is determined,and the optimal cooling fluid flow rate is determined by ICEPAK software.Finally,the thermal simulation of junction temperature proves that the water-cooled radiator designed in this paper is reliable.At last,the key components designed above are assembled into a prototype with complete functions.The experimental results show that the prototype of the inverter has completed the design targets,the power density is 30 kW/L,the peak efficiency is98.65%,and the working effect of each component is good,which verifies the correctness of the design.