考虑撬棒保护的双馈风力发电机定子短路电流计算

摘要

It is known that doubly fed induction generator (DFIG) is widely used in wind generation system,and when the grid voltage drops,the crowbar circuit of DFIG should be put into operation to prevent the overcurrent of rotor circuit,which may threaten the safety of the converter.By taking into account the influences of pre-fault active power,reactive power and crowbar circuit on the transient characteristics of DFIG,the vector forms of DFIG equivalent circuit are analyzed in different coordinate systems,and the expressions of stator short-circuit current are deduced under symmetric and asymmetric faults,which can avoid solving complex differential equations.Besides,the factors influencing the stator short-circuit current after faults and the effect of crowbar circuit on the steady stator short-circuit current are analyzed.Finally,simulations are carried out in Matlab/Simulink to verify the validity and accuracy of the expressions of stator short-circuit current.%双馈风力发电机目前被广泛应用于风力发电系统.电网电压发生跌落时,需要在双馈风力发电机投入撬棒电路,防止转子回路产生过电流,威胁变流器的安全.在考虑故障前有功、无功功率以及撬棒电路投入对双馈风力发电机暂态特性影响的基础上,通过分析不同坐标系下矢量形式的双馈风力发电机等效电路,推导出对称和不对称故障情况下双馈风力发电机定子短路电流的表达式,避免了求解复杂的微分方程,计算过程简便.同时,分析了故障后定子短路电流的影响因素以及撬棒电路对定子稳态短路电流的影响.最后,利用Matlab/Simulink验证了定子短路电流表达式的正确性.