换流变内部短路电流计算及动态模拟技术

Internal Short Circuit Current Calculation and Dynamic Simulation of Converter Transformer

研究换流变压器内部故障下不同位置的短路电流分布特征可以加深故障机理认识为其保护研究提供重要参考。换流变压器内部短路后轴向安匝分布不均匀,从而引起辐向漏磁场分量显著增加。提出以辐向短路电抗修正内部故障后绕组电感参数的变化,将短路绕组与剩余绕组进行等效处理,优化内部故障后的等效电路模型,并提出匝间短路电流的计算方法。所定义的空载运行匝间短路电抗比K可用于描述换流变匝间短路故障后,短路环内电流与网侧短路电流的比值。以工程产品为原型,提出了换流变压器物理模型的一致性技术指标。并通过与原型产品的仿真比对提出了匝间短路电流分布的规律,受故障发生位置影响,相同匝比的短路电流从线圈轴向上看呈现马鞍状分布特点,进一步研制了可以反映内部短路故障的换流变压器物理模型。最后,搭建全物理的换流变压器内部故障动态模拟试验平台,验证了所提出的内部短路电流计算方法的正确性,其K值计算误差控制在-1.70%~0.72%。

Studying the distribution characteristics of the short-circuit current in different positions under the internal fault of the converter transformer can deepen the understanding of the fault mechanism and provide an important reference for its protection research.The axial ampere-turns distribution of the converter transformer is not uniform,which causes a significant increase in the transverse leakage magnetic field component.In this paper,after the winding resistance parameters are corrected by the radial short circuit resistance of the internal fault,the short circuit winding and the remaining winding are treated equally,the equivalent circuit model after the internal fault is optimized,and the calculation method of inter-turn short-circuit current is proposed.The defined no-load running inter-turn short-circuit reactance ratio K can be used to describe the ratio of the current in the short-circuit circle to the short-circuit current at power grid side after the inter-turn fault of the converter transformer.The engineering products are taken as prototypes,and the consistent technical index of the physical model of the converter transformer is proposed.Through the simulation comparison with a prototype product,the law of the inter-turn short circuit current distribution is put forward.Affected by the fault location,the short circuit current with the same turn ratio presents the saddle-shape distribution characteristics from the coil axis.Furthermore,a physical model of the converter transformer is developed that can reflect the internal short circuit fault.Finally,a fully physical dynamic simulation test platform for the internal faults of the converter transformer is built to verify the correctness of the proposed internal short-circuit current calculation method,and the calculation error of its K value is controlled at-1.70%~0.72%.