A comprehensive finite-element model of a turbine-generator infinite-busbar system

Abstract

This paper shows the development of a two-dimensional finite-element magnetic model of a turbine generator coupled to an infinite busbar through a transmission line and a delta-star connected transformer. The finite-element equations of the machine are strongly coupled to the circuit equations of the transmission line and transformer. The circuit equations developed for the delta-star connection enable the simulation of several short circuit conditions at the transformer terminals with the aid of fault matrices. The calculation of electromagnetic torque is performed by surface integration of the Lorentz force, which leads to a unique result for the finite-element model used in this work. The coupling with the external controls of the machine (automatic voltage regulator and governor) is performed in a weak form. Nevertheless, any control model can be easily connected to the finite-element model. Since the use of this finite element model is meant for transient simulations, it is desirable to obtain some simplifications to speed up calculations. Hence, a three-phase current sheet is proposed in this work to avoid the explicit modelling of the stator coreback. This approach also leads to a simple approach to model motion, where remeshing is not necessary.