A methodology for determining electromagnetic parameters of a synchronous machine based on analysis of transient waveforms obtained by the finite element method under no-load conditions

The paper presents the method for determining electromagnetic parameters of a high power synchronous machine based on analysis of transient waveforms caused by small disturbances in the field winding under no-load condition. The waveforms were calculated by the time-stepping finite element method when using a two-dimensional field-circuit model of the machine worked out in the Maxwell program of Ansoft Corporation. The model takes into account non-linear B-H characteristics of magnetic cores, eddy current action in solid parts of the rotor, the rotor motion, as well as the power supply of machine windings from voltage sources. The transient state was initiated by a change in the field voltage of several percents in the form of a step or pseudorandom signal (PRBS) at no load and constant rotor speed. Basing on the determined transient waveforms in the field-circuit model, the parameter estimation of the selected mathematical circuit models of the machine was performed using the least square method. An optimisation algorithm from the Matlab/Simulink package was applied to minimise the mean square error