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

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.