Modelling and identification of synchronous machines, a new approach with an extended frequency range

Correct modeling of turbogenerators is difficult, as currents are flowing during transients not only in the field and damper winding but also in the solid rotor iron. To model this effect, especially at high frequencies, new model structures called ladder networks are introduced. Their parameters are identified by combining the standstill frequency response measurements with the results of the standardized three-phase no-load short-circuit test. By means of this combination the errors in the standstill frequency responses, caused by the iron nonlinearity and the contact uncertainty of the slot wedges at standstill, are expected to be reduced. Both the new ladder networks and the standard models are used to simulate disturbances for comparison. In some cases (three-phase terminal fault out-of-phase synchronization) both models yield equivalent results, but in other cases (operation after a close-up fault) the results of the two models can differ considerably