Numerical Calculation for Transient and Sub-Transient Parameters of Dual-Excited Synchronous Generator Based on Time-Stepping Finite Element Model

The Dual-Excited Synchronous Generator (DESG) has two sets of field windings on the rotor, thus it has better stability and reliability than the traditional synchronous generator. However, the transient parameters of the DESG are different from those of the traditional synchronous generator due to the different rotor structure of the two generators. In this paper, a three-dimensional electromagnetic field model in the end region of a 300-MW DESG is established and the magnetic density and energy density in the end region of DESG are calculated and compared under the different operating conditions. The stator and rotor end leakage reactances are calculated by the energy method. Under the different operating conditions, the end leakage reactance of q-axis field winding varies by 11%, which is the largest compared to those of the d-axis field winding and stator winding. Based on that, the end leakage reactances are substituted into the two-dimensional field-circuit coupled time-stepping finite element model (FCCTSFEM), which is used to calculate the frequency characteristic of the DESG. The transient and sub-transient parameters of the DESG are calculated by combining the FCCTSFEM and the frequency domain method. The influence of the slot wedge material on the transient and sub-transient parameters are studied. Along with the increase of the rotor slot wedge conductivity, the transient and sub-transient reactances are reduced and the transient and sub-transient time constants are increased. The results can provide a theoretical basis for the parameter calculation of the DESG.