中文摘要：

大容量风电并网面临的主要问题之一是风力发电机的低电压穿越问题。为从馈线保护的角度提高风电场的低电压穿越能力,分析了风力发电机并网点感受到的电压跌落特性,探讨了不同过渡电阻和接地程度系数下故障点电压相量的变化特性,量化分析了风力发电机并网点电压跌落畸变极值及产生条件,指出相间短路故障时存在超越状态,对保护的动作特性影响较大,接地故障时电压跌落的畸变极值受接地程度系数的影响严重。

英文摘要：

The low voltage ride through（LVRT） capability is one of the most important problems in the large-scale wind generators connecting to the distribution grid.Since the most voltage sags in the system are caused by faults in feeders,the voltage sags propagation characteristics is key to the design of control strategy of LVRT for wind turbines.In order to enhance the LVRT capacity of wind farm by shortening fault duration from the point of the feeder protection,the profiles of line voltage variations at the fault point are presented with different un-balance fault situations.The extreme voltage aberration and the occurrence conditions in different earthing resistance and residual situations are quantified.The uncommon extreme sags with phase-phase faults is discovered,which may cause the mis-operation of relay.It is also found that the main factors causing extreme sags with phase-ground fault is the value of residual degree factor.