Implementation of a digital AVR for small alternators

Deregulation of the electric utilities has created unprecedented opportunities for growth in the market for diesel generator sets (of sizes up to 5 MVA). Until recently such plants were used, almost exclusively, for emergency stand-by purposes; but this is no longer the case. In order to extract the maximum benefit from this situation improvements must be made in the control and protection features incorporated in these gensets. The automatic voltage regulator (AVR) has a key role in these future developments. This paper describes the development of a digital AVR which can replace the existing analogue AVRs traditionally used. Further, it describes the application of a fuzzy tuning scheme as an approach to resolving conflicting control requirements. Results of step demand, load acceptance and rejection tests are provided for the comparison of the performance of the digital AVR with that of the traditional analogue devices.