Adaptive control system for continuity of supply using dispersed generators

The opportunity to maintain continuity of supply using dispersed generation when the network becomes disjointed and the grid connection is lost, is becoming realisable given the increasing penetration of these units in distribution networks. A rule-based system is presented which provides the necessary switching between the control strategies required for operation in parallel with the grid and when islanded. It consists of an expert system technique for selecting the control of the generator´s excitation system and the automatic governor control system. The control strategy is such that when operating in parallel with the grid, the excitation and governor systems are operated to control the power factor and to regulate active power generation. In islanded operation these systems are operated to regulate the voltage and frequency of the islanded network. An advantage of this system is that it does not use communications to determine which control strategy is appropriate and instead relies on local measurements. Simulation studies are used to demonstrate the effectiveness of the adaptive control system under a variety of operating conditions