Practical implementation on a 5 kVA synchronous generator of an adaptive excitation controller strategy for a wide range of operating conditions

The feasibility of implementing an adaptive-control strategy to the excitation of a synchronous generator is examined in the laboratory. The aim of this work, which extends previously reported investigations based on an optimal-control strategy, is to design a practical controller that is not only suitable for continuous operation, but also meets tight steady-state and dynamic performance criteria over a wide range of leading power-factor steady-state operating conditions. Optimal-control theory is used as a means of determining ‘off-line’ the required feedback gains, use being made of a linearised model of the system for specific operating conditions. A minicomputer, which acts as the real-time controller, estimates the ‘pseudo’ steady-state operating point at any instant and selects the appropriate feedback gains from a ‘look-up’ table stored in memory. The experimental system is tested for a wide range of disturbances of a significant magnitude, and the results compared with predicted responses based on a nonlinear machine model. Good agreement is obtained, and performance criteria are achieved.