Simple formulas for voltage-regulator gains for best alternator stability

Simple formulas are derived for the calculation of the optimum loop gain and damping gain of a certain class of voltage regulators, for good alternator steady-state stability. A generalised Mitrovic method leads to a simple set of curves which apply to all alternators and to all regulators of a given class. A transformation of the parameters of these curves then leads to the required formulas. The method has been applied to specific 350MW units and the results verified by detailed digital computation. Experimental verification on a model power system has also been carried out. It is suggested that these formulas could be used to calculate the gain settings of regulators during commissioning. This would overcome the often encountered problem of obtaining the best step response when it is actually not permissible to apply a step input to the system with the alternator fully loaded.