A Study of the Impacts Caused by Unbalanced Voltage (2%) in Isolated Synchronous Generators

This paper presents an analysis of the oscillations caused by unbalanced loads in salient pole synchronous generators that operate in isolation under steady state. The oscillatory disturbances, arising from the second-order harmonics, may have or have the potential to cause electromechanical damage to the salient pole synchronous generator. In this paper, the goal is to identify and quantify the magnitude of the electromagnetic torque, which assumes an oscillatory form due to the current component from the negative sequence, caused by unbalanced currents. The self-same analysis was included for second-harmonic voltage oscillations in the qd0 domain, the currents induced on the damper windings together with the oscillation of the load angle and on the field current. These oscillations situated on the synchronous generator are analyzed for a degree of voltage unbalance close to 2% which is an acceptable value according to international regulations for power supply from distribution networks, and this same degree of tolerated voltage unbalance will be used herein for isolated synchronous generators.