交直流混杂环境下变压器漏电感参数分析方法

潘超 米俭 蔡国伟 王格万 韩涛 金明权

Abstract：The variation of inductance and current are obviously different from the traditional condition when the power transformer is impacted by DC disturbance. The characteristics of dynamic leakage inductance were studied in AC-DC hybrid transformer. The T-shape equivalent circuit was established based on the basic circuit principle. Identification matrix of the dynamic inductance is obtained， and the identification method of inductance was deduced. Then the electromagnetic characteristics of DC-injected transformer were simulated and analyzed through the time-domain field-circuit coupled method， and the varying rule of the key parameters was summarized. Furthermore， the variation characteristics of dynamic leakage inductance on both sides of transformer were analyzed to reflect the different DC disturbance level combined with T equivalent circuit. Finally， the simulation results were verified by the dynamic model test.

Keywords：equivalent circuit; DC disturbance; dynamic leakage inductance; transformer protection

0 引 言

电力变压器作为电力系统中至关重要的设备，在不同级别的电网互联和功率交换着关键作用[1-2]。研究发现，（准）直流电流可以出现在直流输电单极大地回路运行或地球磁暴条件下交流电网的接地变压器—输电线路—大地回路中[3-4]，同时大规模电力电子装置的应用与普及，使得线路中可能存在一定的直流分量[5]。因此，交流电网中的变压器存在交直流混杂的特殊运行环境，导致作为电磁装置的一类设备如变压器存在直流偏磁[6]。近年来，欧美地区多次发生由于变压器遭受直流扰动所导致的大规模停电事故[7]，我国各地区电网也频繁出现类似事故[8]。直流扰动时，会给变压器带来运行异常以及保护方面等问题，从而威胁电网及其主要设备的安全稳定运行。因此，研究直流扰动时相关参数的变化情况以及对设备和系统的安全性和保护设计具有重要意义。

直流扰动情况下的变压器，存在铁心饱和程度加深、励磁电流畸变以及谐波增加等现象，进一步带来相关电气参数的保护故障以及补偿装置跳闸等问题[9-10]。目前，依靠电感参数开展变压器保护的研究颇受关注[11-13]。文献[14-15]中以变压器漏感参数作为研究对象，利用漏感反映變压器遭受扰动时的内部电磁变化情况，从而保护短路等故障时的变压器。但是，上述方法没有将直流扰动考虑到变压器的运行状态中，而且变压器遭受直流扰动时采用该保护策略并没有对漏感参数进行处理。……