A self-tuning voltage regulator for turbogenerators

The primary function of a turbogenerator automatic voltage regulator (AVR) is to maintain constant operating terminal voltage. This is achieved by adjusting the generator excitation to suit the varying operating conditions of the machine. Turbogenerators are nonlinear systems which are continuously subjected to load variations of random magnitude and duration. The changes in operating conditions of the machine thus cause considerable variations in the system dynamics. Hence, a conventional fixed-gain AVR becomes degraded in performance when the system operating conditions move away from the nominal point. This problem can be successfully tackled by the use of adaptive/self-tuning control. In self-tuning control, online recursive parameter estimation is usually employed to evaluate the unknown and slowly-varying parameters of a discrete-time plant model. In cases such as turbogenerators, changes in the system dynamics under normal conditions are slow, and the estimator is able to track parameter variations closely. Since these estimates are then used to derive the control signal, a self-tuning AVR can improve the control in such a way that it is possible to obtain desired performance over the complete operating range of the turbogenerator