Demagnetization Analysis Of Large Direct-drive Permanent Magnet Wind Power System In Fault Conditions

This thesis mainly focused on demagnetization of permanent magnet synchronousgeneration systems. Building a wind power system simulation model as a platform and usethis module to get the three-phase current of PMSG’s stator under fault working conditions.The aim is using the measured parameters to help us analysis the demagnetizationphenomenon of PMSG.In the first part, background of wind power technology is introduced and three kindsof main wind power generation system are mention. Then, we compare the advantages anddisadvantages of direct-drive permanent magnet wind power system.In the second part, introduce the basic theory of permanent magnetic materials andpermanent magnet synchronous motor. Then give out the equivalent magnetic circuit whichcan explain the necessity for demagnetization analysis theoretically.Third part introduce back-to-back wind power system simulation model. Explain thecontrol strategies and methods of the various components. Use the simulation model to getthe three-phase current of PMSG’s stator under fault working conditions. And compare thedifferent of three-phase short-circuit current with which has no VSR.In last part, discuss whether the different short time will cause differentdemagnetization phenomenon of PMSG or not. Then use the measured stator’s three-phasecurrent to do finite element analysis. Compare the demagnetization results of permanentmagnet motor in different fault conditions, assess whether there is risk of irreversibledemagnetization problem.