Development of a digital excitation control system

Since 1985, NEI Parsons have been supplying digital governor control systems for the safe and reliable operation of new and refurbished turbogenerator plant. The techniques evolved for the digital governor, and subsequently proven in service, have been further developed into a unified range of microprocessor based control systems for flexible high-integrity control. The turbine is controlled by the electro-hydraulic governor, the generator is controlled by the automatic voltage regulator and both benefit by a sequence and monitoring system which provides automatic run-up and loading, on-load valve testing and thermal stress monitoring. The authors describe the important features of the digital automatic voltage regulator (AVR) control system. Triplex modular redundant (TMR) architecture is used in conjunction with majority voting of the outputs of three control channels to provide a high level of redundancy. Computer aided software engineering (CASE) tools were used with in-house software quality assurance procedures to develop the software