考虑撬棒和直流卸荷保护的双馈电机电磁暂态过程分析

ELECTROMAGNETIC TRANSIENT ANALYSIS OF DFIG CONSIDERING CROWBAR AND CHOPPER PROTECTION

故障期间,撬棒(crowbar)保护和直流卸荷(chopper)保护的工作状态对双馈风电机组(DFIG)的暂态过程有重要影响。为此,针对三相故障不同严重程度下的双馈风力发电系统,综合考虑撬棒保护和直流卸荷保护的协调控制方式,通过分析转子电流、直流母线电压与机端电压跌落的关系,新建统一的保护动作分析判据;在此基础上,分析撬棒保护和直流卸荷保护在不同电压跌落深度下的状态,并建立统一的双馈电机故障后暂态等值模型。最后基于PSCAD/EMTDC提供的1 MW双馈电机标准模型,验证了所建DFIG暂态等值模型的准确性。

Crowbar protection and chopper protection operation state during fault have an important influence on the transient process of doubly-fed induction generator(DFIG).With the different voltage drop depths,the protection operation states are different,and the corresponding transient equivalent models of DFIG are also different.Therefore,for the doubly-fed wind turbines system with different severity of three-phase fault,the coordinated control mode of crowbar protection and chopper protection is comprehensively considered.Firstly,by analyzing the relationship between rotor current,DC bus voltage and terminal voltage drop,a unified protection action analysis criterion is established.Secondly,the operation states of crowbar protection and chopper protection under different voltage drop depths are analyzed,and a unified post fault transient equivalent model of DFIG is established.Finally,based on the standard model of 1 MW DFIG provided by the PSCAD/EMTDC,the accuracy of the DFIG transient equivalent model is verified.