Research On The Position Sensorless Control System Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors(PMSM) are widely used in the fields of industry, health care, civil applications and national defense thanks to their advantages such as small size, high reliability, high power density and high efficiency. Recently, high-performance position sensorless control technologies of PMSM have always been the attractive research issues. This thesis studies and analyzes the position sensorless control technologies in high speed and low speed ranges based on the interior permanent magnet synchronous motor(IPMSM).Firstly, the mathematical model of PMSM and the principle of vector control are analyzed and the predictive current control for PMSM vector control system is studied in this thesis. Due to the traditional dead-beat predictive control algorithm based on Lagrange interpolation formula is sensitive to motor inductance mismatch. So an improved dead-beat predictive control algorithm is adopted in this thesis. The current offset constraint and output voltage prediction method are modified. The robustness of the algorithm is improved. This thesis mainly studies the position sensorless vector control system of PMSM based on traditional sliding mode observer. Theory analysis and simulation results show that traditional sliding mode observer has some problems such as chattering and delayed estimation of angle.Secondly, a second order non-singular terminal sliding mode observer is designed based on the extended state equation of IPMSM to solve the problems of traditional sliding mode observer. In this observer, the chattering signal can be filtered by flux equation without influencing the flux phase. There is no need of a low-pass filter and the problem of phase lag can also be avoided. By using non-singular terminal sliding mode, the convergence rate is increased, and the chattering of system is further suppressed by using high order sliding mode. Due to measuring errors and changes of working state, there may exist some errors for the observer parameters. This thesis mainly analyzes the effect of errors of stator resistance, cross-axis inductance and speed on the amplitude and phase of estimated flux. And the position and speed information of rotor are obtained from estimated flux by applying the Phase Locked Loop(PLL).Thirdly, carrier frequency component method(CFCM) is used to realize the position sensorless control of PMSM in the low-speed range. Compared with traditional high frequency signal injection method, CFCM adopts the carrier frequency signal of inverter as the high frequency signal. CFCM does not need inject extra high frequency signal and thus the shortcomings of high frequency signal injection method can be avoided. Under the three-phase triangular carrier modulation, mathematical models of carrier frequency component of PMSM in the α-β and γ-δ coordinate system are studied. The amplitude of carrier frequency component current can be extracted through SDFT and the position and speed information of rotor can be obtained by using PLL.Finally, based on the existing facilities of laboratory, a experimental platform for position sensorless control system of permanent magnet synchronous motor is established. The sliding mode observer experiments, CFCM experiments and closed-loop experiments of position sensorless control system are completed based on this platform. The experimental results verify the feasibility and validity of position sensorless control methods designed in this thesis.