汽轮发电机暂态分析中计及励磁电流集肤效应的时步有限元模型

An Improved Time-stepping Finite Element Model Considering Skin Effect of Excitation Current for Turbo-generator Transient Analysis

在利用场路耦合时步有限元方法对汽轮发电机暂态过程进行仿真计算时,对励磁绕组模型的考虑,往往通过列写整个回路的电路方程表示;该方法无法准确描述励磁绕组中涡流的分布及其对损耗的影响等问题;为了准确的反映电机暂态过程下励磁绕组中涡流的影响,该文先对励磁绕组中各导体单独列写方程,再利用整个回路的电压方程将其联系起来,同时施加串联约束条件;最终得出考虑串联约束条件下计及涡流分布的励磁绕组新模型及基于该模型下的场路耦合时步有限元方程。以一台300MW汽轮发电机定子三相突然短路情况为例,采用不同的励磁绕组模型进行时步有限元计算,通过对比分析励磁绕组中的电流分布与瞬时损耗等,说明该方法的合理性。

When simulating turbo-generator transient process by field-circuit coupled time-stepping finite element method （T-S FEM）, the model of excitation winding was often represented by the circuit equation towards entire loop; however, this method cannot accurately describe the eddy current distribution in the excitation winding and its effect to the loss. In order to reflect the effect of eddy current in the excitation winding during the transient process in electrical machine accurately, the paper firstly present the equations about excitation conductor separately, and then integrate all of them by using the entire loop circuit voltage equation considering the series constraint. Finally a new excitation winding model and its relative finite element equation are proposed. After that, the T-S FEM based on different excitation winding model is utilized to calculate the transient process which is three phases sudden short-circuit of a 300 MW turbo-generator. And the feasibility of the method was verified through analysis of the current distribution and instantaneous loss in excitation winding.