Performance of a 5 kVA synchronous generator with an optimal excitation regulator

The feasibility of applying optimal control to the excitation of a synchronous generator is examined in the laboratory, using a 5 kVA 3-phase alternator connected through line reactors to an infinite busbar. The regulator is a small digital computer, which monitors the states of the system and computes the control signal applied to an electronic amplifier exciting the alternator field. The feedback gains of the optimal regulator satisfy a simple quadratic cost function. These are calculated offline for a grid of operating points in the complex power plane, and stored in the controlling computer. The gains used at any particular operating point are those corresponding to the nearest gridpoint. Comparisons of predicted and actual small-disturbance responses are made for leading-power-factor operation well beyond the open-loop stability limit, and, for low real power, beyond the closed-loop limit with voltage feedback alone.