Research On Sensorless Control Technology For Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor is widely used in the field of defense,aerospace and etc, because of its small volume, light weight, high power density andsmall torque ripple. Rotor position which is needed for closed-loop control can beobtained by using encoders or resolvers. To get rid of the disadvantages of mechanicalsensors and improve system reliability, a variety of sensorless control methods areproposed.PMSM researched in this paper is used in underwater electric propulsion system.Because of worse environment, mechanical sensor fails easily.It will cause underwaterpropeller unable to rise above water, and lead to catastrophe.This paper researchedhigh frequency rotating voltage injection method, and realize the goal that sensorlesscontrol system will replace original system when mechanical sensor fails.According to the survey, high frequency rotating voltage injection is ofadavantage in sensing rotor postion for PMSM researched in this paper which is ofsaliency and low speed. Rotor position can be calculate from high frequency responsecurrent.The present paper studied the choosing of amplitude and frequency of injectedvoltage, filtering process and the design of phase lock loop observer. In theconventional filtering method, the use of BPF can take serious problem ofphase-shifting.So this paper proposed a new filtering method of all HPF, because ahigh-pass filter has zero amplitude for DC signal and low-pass filter has zerophase-shifting for DC signal.On the basis of all-digital vector control system, the rotor position sensingmodule was established. The high frequency rotating voltage injection method is usedfor the simulation analysis.When the motor speed is stable, the rotor positionobservation outputs an electric angle error of±2°.It’s approved that the designedsystem can satisfy the requirement of rotor position detecting and is of good dynamicand static performance.