Affecting factors of grid-connected wind power on fault current and impact on protection relay

The electromagnetic transient models are developed with PSCAD/ EMTDC for three kinds of wind turbine:squirrel-cage wind turbine,DFIG wind turbine and D-PMSG wind turbine.The validity of the electromagnetic transient model for D-PMSG wind turbine is verified by comparing its simulative results with the results of digital-analog hybrid experiments under different fault conditions and control strategies.The validity of the electromagnetic transient model for DFIG wind turbine is verified by comparing its simulative results with the results of short-circuits experiment for real wind farm.Based on these models,the electromagnetic transient characteristics of wind turbines under different fault conditions are analyzed,which show that,the type,working status and adopted control strategy of fan,the fault type and the characteristics of weak power source are the main factors affecting on the fault current of grid-connected wind farm.The research lays the foundation for improving existing protection relay and developing new protection principles.