Electrohydraulic control with throttle pressure compensator

Claim 2

In a steam turbine power plant having valve means and a turbine, the combination of: a. control means for positioning said valve means in response to a first electrical signal representing a desired steam flow through said valve means; and b. first means for modifying the effect of said first signal on the valve means, said first means responsive to instantaneous throttle pressure and operable to modify said first signal so as to adjust the gain of said valve means in a manner inversely proportional to the instantaneous throttle pressure.

Claim 3

The device according to claim 1 with second means to furnish an electrical feedback signal to said control means for further modifying the effect of said first electrical signal on the valve means, said electrical feedback signal representing turbine stage pressure.

Claim 4

The device according to claim 2 with the addition of third means for reducing the overall gain of the control means in response to the failure of one or more critical components of said first or second means.

Claim 5

A device according to claim 1 with the addition of electrical ''''cam'''' means to compensate for valve position versus steam flow nonlinearities.

Claim 6

In a steam power plant having valve means and electrohydraulic control means including a load control unit which supplies a load control signal to a valve positioning unit, the improvement comprising: a. means for supplying to the electrohydraulic control means a signal representing the instantaneous throttle pressure of the power plant; and b. means for modifying the load control signal so that the gain of the valve means is varied inversely with respect to the magnitude of said signal representing the instantaneous throttle pressure.

Claim 7

In a steam power plant having valve means and electrohydraulic control means including a load control unit which supplies a load control signal to a valve positioning unit, the improvement comprising: a. means for supplying to the electrohydraulic control means a signal representing the instantaneous throttle pressure of the power plant; and b. means for modifying the load control signal so that the gain of the valve means is varied inversely with respect to the magnitude of said signal representing the instantaneous throttle pressure.

Claim 8

A device according to claim 5 wherein the means for supplying a signal representing instantaneous throttle pressure comprises a high value gate device and means for supplying redundant throttle pressure signals to said high value gate device, said high value gate device operable to prevent an erroneously low throttle pressure signal from passing to said electrohydraulic control means.

Claim 9

An electrohydraulic control system for controlling a stEam power plant comprising: a. a speed control unit; b. means for supplying a speed reference signal representing desired speed to said speed control unit; c. means for supplying an actual speed signal to said speed control unit; d. said speed control unit operable to compare said speed reference signal and said actual speed signal to provide a first error signal; e. a load control unit; f. means for supplying a load reference signal representing a desired load to said load control unit; g. feedback circuit means for supplying a signal corresponding to the magnitude of first stage pressure to said load control unit; h. said load control unit operable to compare said first error signal, said load reference signal and said signal corresponding to the magnitude of first stage pressure to produce a second error signal; i. a throttle pressure compensator; j. means for supplying to said throttle pressure compensator a signal corresponding to the magnitude of instantaneous throttle pressure; k. said throttle pressure compensator operable to modify said second error signal in response to the magnitude of said signal corresponding to instantaneous throttle pressure, so that the magnitude of said second error signal is modified in a manner inversely proportional to the magnitude of said signal corresponding to instantaneous throttle pressure; l. steam control valves for controlling the steam flow in the steam power plant; and m. a valve positioning unit for positioning said steam control valves in response to said modified second error signal.

Claim 10

An electrohydraulic control system for controlling a stEam power plant comprising: a. a speed control unit; b. means for supplying a speed reference signal representing desired speed to said speed control unit; c. means for supplying an actual speed signal to said speed control unit; d. said speed control unit operable to compare said speed reference signal and said actual speed signal to provide a first error signal; e. a load control unit; f. means for supplying a load reference signal representing a desired load to said load control unit; g. feedback circuit means for supplying a signal corresponding to the magnitude of first stage pressure to said load control unit; h. said load control unit operable to compare said first error signal, said load reference signal and said signal corresponding to the magnitude of first stage pressure to produce a second error signal; i. a throttle pressure compensator; j. means for supplying to said throttle pressure compensator a signal corresponding to the magnitude of instantaneous throttle pressure; k. said throttle pressure compensator operable to modify said second error signal in response to the magnitude of said signal corresponding to instantaneous throttle pressure, so that the magnitude of said second error signal is modified in a manner inversely proportional to the magnitude of said signal corresponding to instantaneous throttle pressure; l. steam control valves for controlling the steam flow in the steam power plant; and m. a valve positioning unit for positioning said steam control valves in response to said modified second error signal.

Claim 11

A device according to claim 5 with the addition of electrical ''''cam'''' means connected with said valve positioning unit to compensate for valve position versus flow nonlinearities.

Claim 12

A device according to claim 5 with the addition of lead/lag network means connected in said feedback circuit means to stabilize transient fluctuations in the signals passing therethrough.

Claim 13

A device according to claim 5 with the addition of safety means for causing the gain of said load control to go to 1.0 and the gain of said feedback circuit means to go to zero when the signal in said feedback circuit means reaches a predetermined low value.

Claim 14

A device according to claim 5 wherein said feedback circuit means comprises a high value gate device and means for supplying redundant first stage pressure signals to said high value gate device, said high value gate device operable to prevent an erroneously low first stage pressure signal from passing to said load control unit.