正如图6 所示,对应于图2 中的磁链轨迹,电压跌落引起在定子磁链上频率为50Hz 的振荡。如果使用传统控制,振荡衰减缓慢。传统去磁和改进后的鲁棒去磁控制方案都能够加速定子自然磁链的衰减。时间常数相同时,两种去磁控制方法的效果是一样的。不知道定子电阻大小时,对比在Rs _ estimated = 0.8Rs情况下两种去磁控制方法的效果,仿真结果如图7。传统去磁无法完全衰减定子自然磁链,而鲁棒去磁控制不会受到影响。传统去磁控制之所以效果欠佳,是因为在这种控制中错误地将定子电阻估测时当做了实际值。这组仿真让我们明显看到了鲁棒去磁控制的优势。
5.总结
本文提出了一种鲁棒去磁控制方法,并阐述了在电网故障时对定子直流磁链的影响。与传统去磁控制方法相比,改进后的方案不需要依赖系统本身的参数。同时讨论了传统和改进后的去磁控制方案的联系与它们对定子电流的影响。这两种去磁控制方法在本质上是一致的。仿真证实了改进后方案的有效性和优势。
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