换流变压器极性反转瞬态电场仿真计算分析

发布时间：2018-03-29 18:26

本文选题：换流变压器　切入点：极性反转　出处：《华北电力大学》2014年硕士论文

【摘要】：目前世界上许多电力大国都采用高压直流输电技术来解决高电压、远距离、大容量送电和电网互联问题。直流输电系统中一次设备故障是引起直流系统强迫停运的首要因素,其中,以换流变压器故障引起的直流系统被迫停运次数最多。在运行中,作用在换流变压器上的除了有高幅值的直流和交流工作电压,以及雷电过电压等各种过电压外,还要承受启动、停运和极性反转等动态直流电压。由于电导率会随着温度、电场强度等的变化而在很大范围内发生改变,而静态和瞬态直流电场的分布情况又与电导率密切相关,所以这种不确定性为直流绝缘的设计带来了很大的困难。故深入研究换流变压器极性反转瞬态电场分布特征对换流变压器的设计、制造和维护具有重要意义。本文首先在电准静态场条件下,利用罚函数法整合边界条件,建立了以节点电位为变量的有限元状态方程,同时对比分析了求解有限元状态方程的几种数值方法。针对一台实际换流变压器,通过将有限元数值计算方法与Ansoft商用软件结合使用对其铁芯及绕组损耗的情况进行了计算,随后又利用Gambit软件对该变压器(包括周围油纸绝缘结构)建立了可用于数值计算的模型,对模型进行了参数设置,并将计算所得的损耗数据作为面积热源对应施加到换流变压器铁芯和绕组上,用Fluent软件仿真计算得到了该换流变压器的二维分布云图。计算结果为后续考虑温度梯度对换流变压器极性反转过程的影响提供了数据支撑。最后讨论并分析了一台实际的换流变压器及其出线套管在考虑电场强度-电导率,温度-电导率等非线性条件下的极性反转瞬态电场分布,并与线性情况的计算结果进行了对比分析,考察了非线性对换流变压器及其出线套管极性反转电场分布的影响,为进行换流变压器及其出线套管的绝缘结构设计提供依据。
[Abstract]:At present, many power countries in the world adopt HVDC technology to solve the problems of high voltage, long distance, large capacity power transmission and power network interconnection. The primary equipment failure in HVDC transmission system is the primary factor that causes the forced outage of DC system. The DC system caused by converter transformer fault is forced out of operation. In operation, in addition to DC and AC operating voltages with high amplitude and various overvoltages such as lightning overvoltages, those acting on converter transformers are also subject to start-up. Dynamic DC voltage such as outage and polarity reversal. The electrical conductivity changes in a large range with the change of temperature and electric field intensity, and the distribution of static and transient DC field is closely related to the conductivity. Therefore, it is very difficult to design DC insulation because of this uncertainty, so it is very important for the design, manufacture and maintenance of converter transformers to deeply study the characteristics of transient electric field distribution of polarity reversal in converter transformers. In this paper, a finite element equation of state with node potential as a variable is established under the condition of electric quasi static field and the penalty function method is used to integrate the boundary condition. At the same time, several numerical methods for solving the finite element equation of state are compared and analyzed. For a practical converter transformer, the loss of its core and winding is calculated by combining the finite element numerical method with Ansoft commercial software. Then a numerical model of the transformer (including the surrounding oil-paper insulation structure) is established by using Gambit software, and the parameters of the model are set up. The calculated loss data is applied to the core and winding of converter transformer as the corresponding area heat source. The two-dimensional distribution cloud diagram of the converter transformer is obtained by using Fluent software, and the results provide data support for the subsequent consideration of the effect of temperature gradient on the polarity reversal process of converter transformer. Finally, the polarity reversal transient electric field distribution of an actual converter transformer and its outlet bushing under nonlinear conditions such as electric field intensity-conductivity, temperature-conductivity and so on is discussed and analyzed. The results are compared with the linear results, and the influence of nonlinearity on the polarity reversal electric field distribution of converter transformer and its outlet bushing is investigated, which provides the basis for the insulation structure design of converter transformer and its outlet bushing.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM721.1

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