Design Of Power Unit Of Motor Controller Based On Silicon Carbide

The third-generation wide-bandgap semiconductor material SiC has received more attention and research due to its excellent physical properties.Because of its high withstand voltage,high switching frequency,and low on-resistance,it is more suitable to replace Si-based devices as power conversion devices,so that the loss of the drive system is reduced,and the efficiency and reliability are improved.With the increase of switching frequency,the quality of the output current of the system can be improved,the harmonic content can be reduced,and the use of filters can be avoided,which can not only reduce the torque ripple and loss of the motor but also reduce the complexity of the system.Because of this,this thesis studies the application technology of SiC MOSFET as the power conversion unit of the drive system at the high switching frequency.Firstly,the equivalent model of SiC MOSFET and the equivalent model of the driving circuit is established,and the influence of parameters on the switching process is analyzed.The key parameters of the driving circuit are simulated and analyzed.On this basis,the crosstalk problem and terminal voltage oscillation problem which greatly affect the stable operation of the device at the high switching frequency are analyzed.Because of the crossing problem,by comparing the effect of each scheme,considering comprehensively,by increasing the power supply of double power supply,using the method of negative pressure off and improved Miller clamp circuit to suppress,and the simulation verification.To solve the problem of voltage oscillation at the end,an absorbing capacitor circuit is added,and the influence of capacitance value and capacitance position on the suppression effect is analyzed.In the protection circuit,based on the gate driver’s oversaturation detection function,the SiC MOSFET short circuit protection.Secondly,the loss of the SiC MOSFET device is calculated.In order to make the calculation result more accurate and closer to the actual situation,the influence of important parameters in the circuit on the loss is comprehensively considered,and a heat dissipation system is designed on this basis,using an aluminum heat sink combined with Heat dissipation by air cooling.The thermal resistance equivalent model is established for the SiC MOSFET and the heat dissipation system,and the simulation software is used to simulate,and it is verified that the junction temperature of the SiC MOSFET does not exceed the maximum temperature and can work normally when it meets the output design requirements.Finally,experiments are carried out on the inverter platform built with SiC MOSFET as the power device.Through the analysis of the experimental results,it is verified that the drive circuit designed in this paper can make the SiC power device work stably at the high switching frequency,and can effectively reduce the output current harmonic content.