Tracking means for a steam electric generating plant automatic control system

Claim 1

In a steam electric generating plant comprising a steam generator, a turbine generator having power operated governor valves controlling steam admission, interconnecting steam conduits between said steam generator and said governor valves, automatic control means for said steam generator and said turbine generator comprising means to generate a load reference, to measure actual generation, to generate an automatic mode first operating error from one difference between a function of said load reference as set point and a function of said measure of actual generation, to develop a feedforward demand for said governor valve position as a function of said load reference, to generate a set point or demand for said turbine stage pressure as a function of said load reference, to measure actual turbine stage pressure, to generate an automatic mode second operating error from the difference between said stage pressure set point and said actual measure of stage pressure, for integrating said automatic mode second operating error as a trim signal and combining said trim signal with said feedforward demand, for converting said combined demand to turbine governor valve position, said means being characterized to close said governor valves as said actual stage pressure increases above said set point and vice versa, further means for integrating said automatic mode first operating error, for modifying the differential relationship between said set point and said actual measure of turbine stage pressure as a function of said automatic mode first operating error integration and characterized to increase or decrease said automatic mode second operating error to open or close said governor valves until said first operating error is zero, the invention comprising tracking means for said control means when said turbine governor valve positioning means is in the manual mode including means to measure governor valve position, to develop a first tracking error from another difference between a function of said measure of actual generation as set point and a function of said load reference, to integrate said first tracking error as an alternative tracking trim signal, to vary said load reference as a function of the difference between said gOvernor valve position and said alternative tracking trim signal, said difference being a measure of the required value for said load reference, said first tracking error integration being adapted to develop equivalence between said load reference and said measure of actual generation, further means to develop a second tracking error from the difference between said measure of actual stage pressure as set point and said demand for stage pressure, to integrate said second tracking error, for modifying said one differential relationship between said load reference and said measure of actual generation as a function of said second tracking error integration and characterized to increase or decrease the working values of said differential relationship, said differential relationship generating a third tracking error, means to integrate said third tracking error and for modifying the differential relationship between said measure of actual stage pressure and demand for stage pressure as a function of said third tracking error integration, said third tracking error integration being adapted to develop equivalence between said measure of actual stage pressure and said demand for stage pressure, and finally means for establishing an equivalence between said first tracking error and said automatic mode second operating error integrator outputs and between said third tracking error and said automatic mode first operating error integrator outputs at time of transfer from said tracking to said automatic control mode.