Steady-state stability of synchronous generators as affected by regulators and governors

Voltage and power-angle regulation can be used to improve the steady-state stability of synchronous alternators, whereas speed governors and tie-line power controllers often introduce instability. In the paper, methods of determining the effects of voltage and angle regulation on the steady-state stability limit are discussed, and they are extended to allow for the control of the prime-mover torque by means of governors and power controllers. The machine analysis is based on the general equations for synchronous machines. A complete analysis of actual problems is rather tedious, and a differential analyser has been found most suitable for detailed investigations. Results, as obtained for typical alternators, are presented in the form of stability contour diagrams, which are very convenient for design purposes, since optimum control parameters can be read off directly.