Electromagnetic transient model and field-circuit coupling numerical calculation of Sen transformer based on finite-element method

Abstract

• A finite-element (FE) model of electromagnetic transient of Sen transformer (ST) with field-circuit coupling is proposed, and the proposed model can characterize the effects of core and winding topology on the internal magnetic field distribution. • The proposed FE model can characterize the electromagnetic field changes of the ST device under different conditions, such as short-circuit fault, injected harmonics, and dynamic power flow control in the external power system. • The electromagnetic transient field-circuit co-simulation of the ST device and external power system is realized. The conventional electromagnetic transient model of Sen transformer (ST) is mainly established by the magnetic equivalent circuit method, which can be used for the fast calculation of transient characteristics for ST. Unfortunately, this approach may lead to oversimplification and missing significant information in the modeling process. To accurately calculate the transient electromagnetic field and reveal the internal magnetic field distribution of the ST under different operating conditions, an electromagnetic transient model and field-circuit coupling numerical calculation of ST based on finite-element (FE) method is proposed in this paper. The proposed model can characterize the effects of core and winding topology on the internal magnetic field distribution, as well as the complex nonlinear property of core materials, such as saturation, eddy current, and hysteresis. The field-circuit coupling method enables the FE model to establish a connection with external networks and realize the electromagnetic transient field-circuit co-simulation of the ST device and external power system. The case studies are performed on a FE model of the ST and a two-machine transmission system. The corresponding winding voltage and current variations of the ST in the presence of short-circuit fault, injected harmonics, and dynamic power flow control in the external networks are analyzed. The numerical calculation and co-simulation results of the proposed FE model of the ST and the external networks are compared with the commercial FE software, which demonstrates the effectiveness of the proposed FE model of the ST. Moreover, the co-simulation results of dynamic power flow control show that the ST can adjust the power flow distribution of two transmission lines through changing compensation voltage.