大型水轮发电机多回路模型的合理简化

适用于分析电机定子绕组内部不对称的多回路模型已成功用于发电机的主保护设计。多回路模型一般表达为含有时变系数的微分方程组，需要借助计算机求得数值解，其计算时间会随方程维数的增加而急剧增长。而大型水轮发电机由于极数多，多回路模型中的阻尼回路数目很大，造成方程维数过高，短路计算耗时过长而无法满足内部短路主保护设计的需要，必须对其多回路模型进行合理的简化。本文对阻尼回路的2种简化方法进行了深入分析和仿真计算，指出等效d轴和q轴阻尼绕组模型应用于电机内部短路计算时，物理概念上存在缺陷，且会造成过大的误差、在工程上无法容许；而近似阻尼笼的处理方法既能满足工程精度要求，又可节省计算时间。

Reasonable Simplification of the Multi-loop Model of the Large Hydro Generators

The Multi-Loop Model adopted in analyzing the internal unsymmetries of the stator windings of electrical machines has been applied in designing the main protection for generators.Since the model usually takes the form of a differential equation group with time-varying coefficients, computer aid is needed to reach the numerical solutions,and the computation time increases rapidly as the order of the equations increases.Large hydro generators,due to their large number of poles,introduce many damper loops in the multi-loop model and high order equations.The computation time is thus too long to satisfy the requirements of internal short circuit main protection design,and reasonable simplifications must be made to these multi-loop models.The in-depth analyses and simulation calculations of two simplification methods are carried out in this paper.Then it is pointed out that the equivalent d- and q-axes damper winding model is not suitable for calculating the internal short circuits because the concept is not applicable in this situation,and the errors caused by it are too obvious to be accepted in electrical engineering; while the approximate damper cage model is acceptable since it not only meets the accuracy requirement of electrical engineering but also saves calculating time for computers.