Research On Position Sensorless Control Of High-Speed PMSM Based On SiC MOSFET Inverter

Because of small size,high efficiency,high power density and direct connection with high-speed loads,high-speed PMSM(permanent magnet synchronous motor)are widely used.As the third generation of wide bandgap semiconductor power switches,SiC MOSFETs have advantages of high temperature resistance,high thermal and fast switching speed.Sensorless control technology can enhance control system reliability while reducing system cost.Therefore,SMO(silding mode observer)is more suitable for high-speed motors control system because it takes less computing resources.In order to improve the control performance of high-speed PMSM,this thesis researched around SMO position sensorless control system of high-speed PMSM.The specific research contents are as following:(1)As some important parameters of the high-speed PMSM used in this thesis were unknown,a simple experimental measurement method based on the study of the mathematical model of SPMSM was designed in this thesis.This method can measure the dq axis inductance and rotor flux with an impedance analyzer and an oscilloscope.At last a double closed-loop control system of PMSM was built.(2)On the basis of the study of SMO position sensorless control,sliding mode chattering can be suppressed by using a saturation function instead of the sign function.A PLL(phase lock loop)was used to extract the rotor position information,which can decrease the errors caused by the parameters' changes of PMSM.By investigating the sampling sequence of digital controller,an optimization method of sampling sequence was proposed.(3)Based on the study of the complex vector model of PMSM,this thesis proposed a discrete complex vector model of PMSM and designed a new SMO based on the discrete complex vector model of PMSM,which can decrease the error between the estimated rotor position and the actual rotor position.Then,the stability condition of the designed SMO was obtained by using Lyapunov stability criterion.Finally,the parameters differences between two kinds of SMO was compared.(4)In order to improve the control performance of high-speed PMSM,this thesis built a digital controller with a more superior performance DSP and FPGA to increase the sampling frequency.SiC MOSFETs were chosen as the inverter power switching device to increase sampling frequency.Because of the increasing of switching speed,the crosstalk of bridge arm was aggravated.Therefore,a drive circuit to suppress crosstalk was proposed in this thesis.