The Short Circuit Protection Research On Direct-drive Permanent Magnet Wind Power Generator

With the increase of the capacity of the wind turbine generator and the increase of the number of operation,and with the development of wind power industry,wind power as a new type of energy in the proportion of China’s energy structure is growing.In recent years,because of the small fault of wind turbine,the large area unit is cut off,and the large area network removal occurs.The internal circuit is one of the typical internal faults of wind turbine generator,the generator will produce short circuit current with great harm in the event of an internal short circuit,which will directly or indirectly to the power system and the people’s life caused great economic damage,so the internal short circuit of wind power generator with the appropriate main protection is necessary.Research on wind power generator winding short circuit protection scheme can effectively improve the security of the unit operation,reduce the occurrence of wind turbine faults,improve the efficiency of wind power generation field,has an important significance to promote the development of wind power industry and the adjustment of energy structure.First of all,the mathematical model of permanent magnet generator,this paper summarizes the winding structure of direct drive permanent magnet synchronous wind power generator and three-phase static coordinate system,the establishment of direct drive permanent magnet wind generator finite element mathematical model.On the basis of the model with the external circuit simulation of interturn and single-phase grounding short circuit,ANSOFT MAXWELL simulation waveform of winding current before and after fault and analyzes its characteristics based on the stator current according to the characteristics,find out the fault feature.Secondly,analysis of the permanent magnet generator with different number of turns of winding short circuit fault,1.5MW direct drive permanent magnet wind generator winding as the research object,using the ANSOFT MEXWEL0 L simulation that each phase current effective value obtained after a short circuit,when the stator inter turn short circuit occurs,thestator phase current distribution is asymmetric,with the deepening of the degree of fault increase,and amplitude of the fault phase current is obviously higher than that of non fault phase.The third,the generator winding single-phase grounding fault is simulated,compared and analyzed the trend of current change before and after the fault,and on this basis to explore the fault characteristics,according to the analysis results of single-phase grounding short circuit,summed up the changes of short-circuit current,the winding single-phase grounding fault occurs,the phase short-circuit current threat the generator winding is more serious.Finally,the winding and single-phase ground fault of permanent magnet wind turbines are analyzed,and the main protection scheme of "one longitudinal and two horizontal" is set up,so as to change the status of direct drive permanent magnet wind turbine without effective protection.Through the data analysis of different short circuit faults of internal windings,for the inter turn short circuit fault,the transverse current difference is obviously larger than the longitudinal,and the sensitivity of transverse differential protection is better than the sensitivity of incomplete differential protection.