双馈异步风力发电机低高电压连锁故障暂态特性精确分析及穿越方案

Accurate Analysis of Transient Characteristics and Ride-through Scheme Under DFIG Low and High Voltage Cascading Fault

双馈异步风力发电机(doubly-fed induction generator,DFIG)单一电压骤变故障穿越技术广受关注,而连锁故障同样对DFIG的不脱网连续运行带来严峻挑战。现有研究大多忽视了低高电压连锁故障中低电压阶段对后续电压骤升的影响,对连锁故障暂态过程进行详细推导,指出高电压阶段的转子感应电动势中存在着表征低电压阶段的影响量,这使得暂态冲击比单一故障情况更为严重,从而揭示了连锁故障与单一故障暂态特征的本质差异。在此基础上,给出一种基于转子暂态感应电动势抑制的低高电压连锁故障穿越方案。通过理论推导得到了定子电流微分能准确反映低高电压连锁故障各阶段转子暂态感应电动势这一规律,并给出了将其作为转子电压参考值补偿项来直接抑制暂态感应电动势的控制策略,一方面在通过快速抵消低电压阶段暂态感应电动势达到降低转子过电流的前提下,对电压骤升带来的暂态冲击起到抑制作用,另一方面有效限制了高电压阶段的转子电流,提高了整个连锁故障穿越性能。仿真验证了连锁故障暂态分析的正确性和穿越方案的有效性。

The research on fault ride-through technology of doubly-fed induction generator(DFIG)is becoming mature,and cascading fault also poses severe challenges to the continuous operation of DFIG.Current research mostly ignores the influence of low voltage stage in voltage cascading fault on subsequent voltage swells.This paper derived the transient process of cascading fault in detail,and pointed out that the rotor induced electromotive force in the high-voltage phase has an influence that characterizes the low-voltage phase,making the transient impact more serious than the single fault situation.It reveals the essential difference in their transient characteristics.A cascading fault ride-through scheme based on rotor transient induced electromotive force suppression was presented.After deduction,it is known that the stator current differential can reflect the rotor transient induced electromotive force at each stage of the cascading fault.On the one hand,by canceling the transient induced electromotive force in the low voltage stage to reduce the rotor overcurrent,it can suppress the transient impact caused by the voltage swell.On the other hand,it effectively limits the rotor current in the high voltage stage and improves the entire cascading fault ride-through performance.The simulation verifies the correctness of the cascading fault transient analysis and the effectiveness of the traversal scheme given in this paper.