Damper Currents Simulation of Large Hydro-Generator Using the Combination of FEM and Coupled Circuits Models

A high-order model is required for an accurate simulation of the synchronous alternator spatial harmonic content. However, some hydro-generators have fractional slot per pole per phase windings, and carrying transient simulations of these machines with finite-element software often leads to unacceptable computation time. This paper details a large alternator modeling method that provides an excellent compromise between accuracy and speed. It is a combination of magnetostatic finite element method and coupled circuits model. The paper details the construction of this model and explains the procedures to identify several model parameters from experimental data as the standstill frequency response and open and short circuit tests. The effectiveness of this modeling method is validated by the study of a large 109-MVA hydrogenerator having an instrumented rotor pole. We compare transient and steady-state simulation waveforms of the damper bar currents during sudden two- and three-phase short-circuit to the experimental measures.