Research On Sensorless Control Technology Of Permanent Magnet Synchronous Motor At Low Speed

Permanent magnet synchronous motor(PMSM)has been extensively used in the field of high-performance electric drives due to its laconic structure,high power factor,and fast dynamic response.The key to reliable control of motor is to know the position and speed information of rotor.The use of mechanical position sensor increases the volume and cost,limits the application occasions,and reduces the overall reliability of the motor system.Therefore,the use of sensorless control technology to replace mechanical sensors is the subject that has significant practical values,and deserves deep investigations.In low-speed sensorless control of permanent magnet synchronous motor,the salient pole effect of the motor is applied.This thesis is carried out around the surface-mounted permanent magnet synchronous motor without structure salient pole,the vector control method of id=0 is selected.Based on its basic mathematical model and coordinate transformation,a mathematical model for estimating high-frequency signal excitation in a rotating coordinate system is established.The saturation salient pole effect created by pulse high frequency voltage injection method are used to extract rotor position and speed information.However,with factors influenced such as inverter dead zone effect,motor parameter error and current detection error,the position estimation error signal is superimposed with 2 and 6 times the rotor electrical angular frequency harmonics.Then,it will lead to accuracy reduction of the estimated speed and position,which cause a series of problems such as high-frequency torque ripple,high-frequency noise and so on,and weaken the reliability of the sensorless control operation.To make the estimated speed and position accurately,two second-order generalized integrators are connected in series to eliminate specific harmonics and further optimize the position estimation error signal,which reduce the fluctuation of the rotor position and improve the stability of the motor system operation.A simulation model was built on Matlab/Simulink simulation platform and the simulation results were obtained,which verified that the proposed optimization scheme was feasibility;With the experimental platform built and the debugging experiment and sensorless control experiment with CCS software completed,the results show that the accuracy of motor speed and rotor position estimated by the optimization scheme is higher.