Research On Low Voltage AC Servo Driver Based On SiC MOSFET

With the development of society,AC servo system with permanent magnet synchronous motor as control object has been widely used in people's daily life,industrial production and national defense construction.However,high voltage AC power supply can not be supplied to the servo system as power source,only 24V DC power supply can be provided,in the case of field operations.When the low-voltage power supply is used,the AC servo system will have the problems of large tube voltage drop,high loss and big size.Compared with Si IGBT;the SiC MOSFET has the advantages of short switching time,high switching frequency,low on-state voltage drop and low loss.In this paper,the study of SiC MOSFET power module substitutes for Si IGBT power module is done to overcome the technical difficulties existed in low voltage AC servo system.Especially the high switching frequency,the loss advantage of low-voltage AC servo system densigned by SiC MOSFET is more obvious,it is of realistic meaning and practical value for the study of high-performance low-voltage servo system.Firstly,the structure and characteristics of SiC MOSFET are introduced,the functional model of SiC MOSFET is established and some simulations are done,the switching characteristics,tube pressure drop and switching loss of SiC MOSFET are analyzed.Theoretically,the tube voltage drop and loss of SiC MOSFET are lower than Si IGBT in the same power level,the higher the switching frequency,the greater the difference in switching losses between SiC MOSFET and IGBT..Secondly,the working principle of the main circuit is analyzed,the main circuit is built with SiC MOSFET and IGBT model respectively.Using the SPWM signal as the trigger signal and the sine wave as the modulation wave,the voltage drop and loss is simulated during the main circuit operation.Through the comparison and analysis of the simulation results,it is proved that the main circuit based on the SiC MOSFET has lower voltage drop and the loss,especially the high switching frequency,the loss advantage of the main circuit by SiC MOSFET is more obvious,and is more suitable for low voltage AC servo drive application.Finally,the hardware and software of the low voltage AC servo system are designed with TMS320F2812 as the control core,CCS050M12CM2 of CREE and PM 100RLA120 of Mitsubishi Co.as main circuit,and then the experimental platform of low voltage AC servo system is set up.The servo drivers based on the two power modules are tested for on-state voltage drop and loss.The experimental results show that the on-state voltage drop and loss of the low voltage AC servo driver based on the SiC MOSFET are lower than on the IGBT,especially the high switching frequency,the loss advantage of low-voltage AC servo driver based on SiC MOSFET is more obvious.It is significant to improve the voltage utilization of low-voltage servo drives,reduce the volume of low-voltage servo drives,and increase the power density of low-voltage servo drives.