A New Method to Evaluate the q-Axis Saturation Characteristic of Cylindrical-Rotor Synchronous Generator

It has been observed that the values of the magnetizing reactances in both d- and q-axis are reduced significantly from their corresponding unsaturated values as a result of nonlinearities introduced by saturation under both steady-state and transient operations. In the round rotor synchronous machine, q-axis magnetic circuit saturates appreciably more than that along the d-axis because of the presence of the rotor teeth. In the second section, a new method to calculate the q-axis saturation characteristic from the existing d-axis saturation characteristic has been presented. We have next calculated the saturated values of the d- and q-axis self magnetizing reactances and mutual cross magnetizing reactances between the two orthogonal axes under the steady-state operation. Finally, the effect of saturation, particularly the effect of q-axis saturation, on the power system transient stability has been presented. Index Terms--Cross-Saturation, q-axis saturation, saturated reactances, saturation, synchronous machine, transient stability.