换流变压器铁心饱和型不稳定性预测

Prediction of Core Saturation Instability at Converter Transformer

换流器交流侧二次谐波分量和直流侧基频分量通过交直流系统间的相互作用,会导致高压直流输电系统出现谐波不稳定现象,换流变压器的铁心饱和会进一步加剧这种不稳定。本文研究了换流变压器铁心饱和不稳定产生的机理,分析了系统交直流侧的频率阻抗特性,建立了铁心饱和型谐波不稳定等效电路,通过谐波传递矩阵推导出饱和稳定判定因子,提出预测铁心饱和不稳定现象的方法。最后在电力系统电磁暂态计算软件PSCAD/EMTDC中建立仿真回路验证了该方法的正确性。

Interactions between second harmonic quantities on the AC side of the converter and fundamental frequency quantities on the DC side of the converter will lead to a type of harmonic instability. The instability can be reinforced by saturation of the converter transformers.the generation mechanism of transformer core saturation instability and the impedance/frequency characteristics of the AC and DC system are researched . An equivalent circuit of core saturation instability is established and saturation stability factor is derived by the harmonic transfer matrix. The paper presents an analysis which can be used to predict where core saturation instability is likely to occur. The results are confirmed by using the digital transients simulation program PSCAD/EMTDC.