Synchronous generator stability as affected by tie-line reactance

The paper describes various approaches to overcoming the stability problems encountered when a synchronous generator feeds power to a busbar via a tie-line of appreciable reactance. The study uses linearised state-variable equations for the generator, with added voltage regulation and speed governing control systems and stability considerations based on the eigenvalues of the overall system matrix. The corresponding transient performance is demonstrated by the time response following a small system disturbance. Additional system damping, provided by various stabilizing signals derived from the generator output, is shown to be ineffective in extending the range of tie-line reactance over which the system is stable. However, a control law resulting from the application of linear optimal control with a suitable performance index leads to a wider range of tie-line reactance for good and stable operation. Further performance improvements are shown to be possible using either a controller designed using modal control theory or a 2-input optimal controller