Optimal Transient Removal in a Power System

After a transient disturbance in a power system, some of the generators will have advanced in phase and some will have been retarded in phase. The deviation from steady-state operation can be removed in minimum time by optimal nonlinear bang-bang control. For each generator whose phase has advanced, the optimal control consists of exciting the field with maximum voltage, followed by a period of reversed voltage on the generator field, a period of maximum positive voltage on the generator field, and then a return to normal excitation. This sequence is controlled by nonlinear decision functions which obtain their information from the state of the system. The most desirable state variables are shaft angle, shaft velocity, and field current. Experimental tests have shown significant increases in transient stability [1]-[3].