Rotor Initial Position Detection On Permanent Magnet Synchronous Motor Sensorless Control

Permanent magnet synchronous motor(PMSM) has the advantages of smallcubage, good control characteristics, high power factor, high reliability and so on, forits use in the industrial field and civilian applications increasingly widespread. Theaccuracy of the PMSM rotor initial position is the decisive factor for startingtorque value and starting it successfully. And if the PMSM rotor initial position hasnot been detected accurate, it will cause the excessive current, rotor reverse and evenstart failure when start the PMSM. In traditional, the rotor position information inPMSM control system are usually acquired by mechanical sensor, however,mechanical sensor has some extent limit in terms of price, working environment,reliability and so on. So it has great engineering significance to study the rotor initialposition detection strategy in PMSM speed sensorless control system.This thesis has been studied the problem about the rotor initial position detectionfor surface mounted permanent magnet synchronous motor(SPMSM).At first, it has introduced the PMSM development and current state, and itscontrol theory, and the engineering significance of the rotor initial position detection.The essential theory related to PMSM control system has been studied. The vectorcontrol method and the speed sensorless control method, which is based on slidingmode observer, for PMSM have been analyzed.Then, the major study was the rotor initial position detection method for PMSMspeed sensorless control, which included the forced alignment method, the highfrequency signal injection method and the voltage vector injection met hod. Thoseprinciple and characteristic have been analyzed with mathematical model and relevanttheory. The study focused on the voltage vector injection method for the SPMSMrotor initial position detection. Based on the analysis of the validity of induct ancesaturation effect, this thesis proposed the voltage vector injection method for theSPMSM rotor initial position detection. To deal with the problem of low accuracy andunreliability in the traditional voltage vector injection method for SPMSM, it use dreverse direction inductance to add constraints when handling the second wave ofvoltage vector, and proposed increasing the action time of voltage vector to increasethe peak current after the second wave of voltage vector. By enhancing the effect ofdemagnetization and enlarging the differences of each current vector, it finallyimproved the accuracy and reliability of rotor initial position detection. At Last, built an experimental platform with TMS320F28335chip of TI as thecore, this thesis has shown the experimental data and result of the SPMSM rotorinitial position detection. The experiment has used the forced alignment method tovalidate the rotor position and analyzed the difference between the voltagevector injection detection method with and without improvement. The experimentalresults have verified the feasibility and effectiveness of the analysis and design. Theyhave been shown that the improved detection method can not only guarantee the rotorstatic, but also improve reliability greatly, and the detection accuracy has beenincreased from the7.5°to1.8°. So this method has the great value ofpractical engineering.