Abstract: An analog control system and a digital system are provided with an integrated interface for the input/output signals used in monitoring and controlling an electric power plant. Plant analog and digital inputs are processed through circuitry which provides input signals compatible for use in both the analog and the digital systems. Analog and digital outputs are similarly processed through circuitry which provides compatible signals. Output signals are directly applied from the analog control to the digital system or vice versa without need for buffering.

Abstract: In a combined cycle plant, a process flow demand signal is applied to multiple sequentially operated boiler feedwater valves through a single manual/automatic (M/A) station. Each valve is positioned in accordance with its position/flow characterization so that the total feedwater flow to the boiler satisfies the flow demand. To provide for bumpless manual to automatic transfer, valve position signals are characterized with the inverse of the respective valve characterizations in the flow region not covered by a lower order valve. The characterized outputs are set to zero in flow regions covered by a lower order valve. A high selection of the characterized outputs is performed and the selected signal corresponds to the process flow demand value which will enable a manual to automatic transfer without causing an upset in steam generator process flow or electric power generation.