单相特高压自耦变压器直流偏磁电磁特性研究

发布时间：2018-04-25 04:04

本文选题：特高压变压器 + 直流偏磁　；参考：《华北电力大学(北京)》2017年博士论文

【摘要】：高压直流输电和磁暴现象引起的变压器直流偏磁效应严重影响变压器的安全运行。特高压电网采用八分裂导线,电阻小,更易遭受直流扰动的侵害。特高压变压器作为特高压电网的关键设备,其运行的可靠性与安全性直接关乎整个电网的正常运行。为此,本文针对特高压变压器的直流偏磁问题进行了计算与分析。主要研究内容和取得的成果如下:基于特高压变压器铁心材料的高导磁性和强非线性特性,提出了基于空载简化电路模型下的分段解析法,进行直流偏磁条件下计算结果准确性问题的研究与分析。继而以解析解的计算结果为基准,对比分析四阶龙格库塔法的数值计算结果。结果表明,在特高压变压器的直流偏磁数值计算中,可通过人为增大串联电阻和适当减小计算时间步长来获得较为准确的直流偏磁特性。该研究结果为实际特高压变压器进行基于场路耦合法的直流偏磁计算提供了一种有效解决方法。根据特高压变压器实际的结构参数和电气连接方式,建立变压器的场路耦合模型,分析串联电阻值和时间步长对直流偏磁计算结果的影响。人为增加一个串联电阻,改变了变压器本身的电路结构,导致串联电阻后侧的电压偏离所施加的额定交流电压。因此,提出电压补偿原理,进行电压补偿的迭代计算。计算结果表明,电压补偿可有效消除串联电阻值导致的电流计算偏差。在此基础上,进行特高压变压器不同直流偏磁电流下的空载直流偏磁仿真计算,获得励磁电流和磁场特性。为提高特高压变压器空载直流偏磁计算效率,提出了一种基于动态电感-励磁电流曲线的空载直流偏磁快速计算方法,该方法避免了不同直流偏磁电流情况下重复进行磁场模型的动态电感的求解。通过与场路耦合算法计算结果的对比,验证了该方法的正确性和有效性。同时,该方法大大节省了计算时间,提高了计算效率,为变压器的直流偏磁计算提供了一种快速简便的计算方法。针对特高压变压器负载运行方式下的直流偏磁问题进行研究与分析。增大原边串联电阻,可使原边电流中直流分量的计算结果接近于直流偏磁电流理论值,提高计算结果的准确性。分析直流偏磁情况下不同负载电阻对特高压变压器高、中压绕组电流的影响,获得了负载由过载到额定,再到轻载直至空载运行状态下高、中压绕组中电流的变化规律。进行不同直流偏磁电流时负载运行方式下的直流偏磁计算和电流特性分析。基于不同直流偏磁电流下计算得到的空载与负载电流,进行无功功率和涡流损耗计算及其特性分析,为特高压变压器耐受直流偏磁能力的评估提供参考。本文所开展的研究工作为进行特高压变压器直流偏磁条件下的温升计算奠定了计算基础。
[Abstract]:The DC bias of transformers caused by HVDC transmission and magnetic storm seriously affects the safe operation of transformers. UHV power grid adopts eight-split conductors with low resistance and is more vulnerable to DC disturbance. As the key equipment of UHV power network, UHV transformer's reliability and safety are directly related to the normal operation of the whole power network. In this paper, the DC bias of UHV transformer is calculated and analyzed. The main research contents and achievements are as follows: based on the high conductance magnetic and nonlinear characteristics of UHV transformer core material, a piecewise analytical method based on no-load simplified circuit model is proposed. The accuracy of calculation results under DC bias is studied and analyzed. Then the numerical results of the fourth order Runge-Kutta method are compared and analyzed on the basis of the analytical solution. The results show that in the numerical calculation of DC bias of UHV transformers, the more accurate DC bias characteristics can be obtained by artificially increasing the series resistance and appropriately reducing the calculation time step. The results provide an effective solution for DC bias calculation of UHV transformers based on field-circuit coupling method. According to the actual structure parameters and electrical connection mode of UHV transformer, the field circuit coupling model of transformer is established, and the influence of series resistance and time step on the calculation result of DC bias magnetic field is analyzed. Artificially adding a series resistor changes the circuit structure of the transformer itself and causes the voltage at the rear side of the series resistance to deviate from the rated AC voltage applied. Therefore, the principle of voltage compensation is put forward, and the iterative calculation of voltage compensation is carried out. The calculation results show that voltage compensation can effectively eliminate the current calculation deviation caused by series resistance. On this basis, the simulation calculation of no-load DC bias magnetic field of UHV transformer under different DC bias current is carried out, and the excitation current and magnetic field characteristics are obtained. In order to improve the efficiency of no-load DC bias calculation of UHV transformer, a fast calculation method of no-load DC bias based on dynamic inductor-excitation current curve is proposed. This method avoids repeated calculation of the dynamic inductance of the magnetic field model under different DC bias current. The correctness and validity of the method are verified by comparing with the results of the field circuit coupling algorithm. At the same time, this method greatly saves calculation time and improves calculation efficiency. It provides a fast and simple calculation method for DC bias calculation of transformer. The DC bias of UHV transformer under load operation mode is studied and analyzed. The calculation results of DC component in the primary edge current can be close to the theoretical value of DC bias current and the accuracy of the calculation result can be improved by increasing the primary edge series resistance. This paper analyzes the influence of different load resistance on the current of UHV transformer under the condition of DC bias magnetic field, and obtains the variation rule of the load from overload to rating, from light load to high running state of no-load, and middle voltage winding. The calculation of DC bias and the analysis of current characteristics under different load operation modes are carried out. Based on the calculation of no-load and load current under different DC bias magnetoelectric current, the reactive power and eddy current loss are calculated and their characteristics are analyzed, which provides a reference for the evaluation of DC bias resistance of UHV transformer. The research work in this paper lays a foundation for the calculation of temperature rise of UHV transformer under DC bias.
【学位授予单位】：华北电力大学(北京)
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM411.3

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