A Variable Gain Control Scheme of Digital Automatic Voltage Regulator for AC Generator

The voltage control characteristic of synchronous generation system in power plant is dependent on the performance of the excitation control. AVR (automatic voltage regulator) adjusts the excitation voltage and current for the control of synchronous generation system. The AVR controller must have capabilities to acquire the demanded transient response that is able to over come the time-delay of exciter and to damp out the inherent instability of generator and prime mover. This paper presents a variable gain control scheme of DAVR (digital automatic voltage regulator) for AC brushless generator. In order to improve dynamic response and steady state performance, a PID controller with a simple gain adjuster is used. And the gains of PID controller are updated by the terminal voltage and load current in order to improve dynamic response and stability. The structure of the proposed gain adjuster is designed by a a simple linear function and the gain is increased in- proportional to load current and terminal voltage. The proposed control scheme is verified by experiments.