Flux-weakening Analysis And Control Strategy For Permanent Magnet Synchronous Motor

With the power electronic and magnetic materials development, permanet magnetsynchronous motor(PMSM) servo system are more and more widely used. Theexcitation of PMSM is unable adjusted, and the d-axis inductance is small due topresence of permanent magnet in d-axis magnetic circuit is found. Based on the abovereasons, the flux-weakening level of PMSM is poor. In order to improve the PMSMflux-weakening capability, the research from the structure design and control strategyto solve the high speed problem is necessary.Based on the actuality of weak magnetic extender speed and control strategy, thispaper analyses the flux-weakening of PMSM from electromagnetic structuralcombined the control system, main content includes:First, the key factor of flux-weakening is no-load permanent magnet chains andd-axis inductance by anslyzing, to get the most effective way to improve theflux-weakening capability is increase d-axis inductance. On this basis, specificanalyse the relation of flux-weakening capability and parameter of electric machine,such as permanent magnet material and size, gap length, stator slit width and armaturewinding.Secondly, analyzing the flux-weakening performance of the interior permanentmagnet synchronous with different rotor magnetic circuit structure(radial andtangential). Finite element analysis results show that the radial type has better torqueperformance, the tangential type has higher speed range. Calculate the leakagemagnetic coefficient, permanent magnetic flux and armature reaction circuitreactances of PMSM under considering saturation of magnetic route. Radial structurehas smaller permanent magnetic flux and leakage magnetic, and inductanceparameters variety low. The d-axis inductance of tangential type will change even influx-weakening control due to high saturation magnetic circuit.Finally, based on the principle of vector control, this paper puts forward a newflux-weakening control method. Analysis flux-weakening control of PMSM undervoltage coordinates system has some advantages such as simpler control model, fasterdynamic response and higher flux-weakening level. Control system simulations basedon MATLAB are performed for two rotor structure models. The results show thattangential type has extender speed capacity, as the same as finite element analysisresults.