特高压变压器空载直流偏磁电磁特性与涡流损耗计算

发布时间：2019-06-14 12:11

【摘要】：近年来,超、特高压直流输电线路在国内快速铺开,在实现电力输送方便快捷的同时,直流输电线路导致交流系统中接地变压器出现直流偏磁的问题日益频繁和严重。特高压变压器作为特高压电网的核心元件之一,其运行的可靠性和安全性对整个电网的正常运行至关重要。本文从场路耦合法计算偏磁电流的思路出发,分析场路耦合计算的过程和特高压变压器的结构特点,针对场路耦合算法应用在特高压变压器直流偏磁计算中出现的问题,按照特高压变压器实际参数,建立变压器铁心绕组模型,采用规则网格划分,建立直流偏磁计算场模型,有效减少场模型节点单元规模;根据特高压变压器电气连接图,通过串联电阻和电压补偿来解决路模型求解过渡过程长问题;在利用四阶龙格库塔法求解每一步电流的过程中,将中间时刻的电流预估值也返回场模型进行修正电感,以此降低电感波动,提高计算准确性。通过这三个步骤来搭建适合特高压变压器空载直流偏磁计算的场路耦合模型,并进行了偏磁电流计算。本文在该模型的基础上进一步简化计算流程,提高计算效率,通过获取特高压变压器的电感-电流曲线和偏磁情况下空载电流峰值-直流偏磁电流曲线,提出了一种特高压变压器直流偏磁空载电流实时计算方法。通过与场路耦合算法对比,对其计算结果进行验证。通过选择最优迭代算法和一种变步长策略,实现了在发生直流偏置时,能够实时跟踪该偏置量对应的电流波形,为防止变压器保护拒动或误动、变压器直流偏磁电气参数扰动在线评估、避免无功补偿电容器谐波电流过大等方面提供参考。建立了特高压变压器直流偏磁涡流损耗计算模型,利用实时算法得到的偏磁电流波形,计算特高压变压器在不同偏置直流下的涡流效应,研究了特高压变压器中间拉板、旁柱拉板、夹件、铜屏蔽和箱体的涡流损耗,为进一步研究特高压变压器直流偏磁温升效应和制定特高压变压器直流偏磁评价指标提高参考。
[Abstract]:In recent years, ultra-high voltage (UHVDC) transmission lines have been rapidly spread out in China. While the power transmission line is convenient and fast, the DC bias problem of grounding transformers in AC system is becoming more and more frequent and serious. As one of the core components of UHV power grid, the reliability and safety of UHV transformer is very important to the normal operation of the whole power grid. Based on the idea of calculating bias current by field circuit coupling method, this paper analyzes the process of field circuit coupling calculation and the structural characteristics of UHV transformer. Aiming at the problems existing in the application of field circuit coupling algorithm in DC bias calculation of UHV transformer, according to the actual parameters of UHV transformer, the transformer core winding model is established, and the DC bias field model is established by regular grid division. Effectively reduce the size of node elements in the field model; According to the electrical connection diagram of UHV transformer, the long transition process problem is solved by series resistance and voltage compensation. In the process of solving each step current by using the fourth-order Runge-Kutta method, the estimated current at the middle time is also returned to the field model to modify the inductance, so as to reduce the inductance fluctuation and improve the accuracy of the calculation. Through these three steps, a field-circuit coupling model suitable for no-load DC bias calculation of UHV transformer is built, and the bias current is calculated. On the basis of this model, this paper further simplifies the calculation flow and improves the calculation efficiency. By obtaining the inductance-current curve of UHV transformer and the no-load current peak-DC bias current curve of UHV transformer under the condition of magnetic bias, a real-time calculation method of DC bias no-load current of UHV transformer is proposed. Compared with the field-circuit coupling algorithm, the calculation results are verified. By selecting the optimal iterative algorithm and a variable step size strategy, the current waveform corresponding to the bias can be followed in real time when DC bias occurs, which provides a reference for preventing transformer protection from rejection or misoperation, on-line evaluation of transformer DC bias electrical parameters disturbance, and avoiding excessive harmonic current of reactive power compensation capacitors. The calculation model of DC bias eddy current loss of UHV transformer is established. The Eddy current effect of UHV transformer under different bias DC is calculated by using the partial magnetic current waveform obtained by real-time algorithm. The eddy current loss of UHV transformer intermediate drawing plate, side column drawing plate, clamp, copper shield and box body is studied. It provides a reference for further study of DC bias temperature rise effect of UHV transformer and improvement of DC bias evaluation index of UHV transformer.
【学位授予单位】：华北电力大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41

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