Apparatus for the prevention of critical process variable excursions in one or more turbomachines
AssigneeCompressor Controls Corporation
InventorsKrishnan Narayanan, Paul F Fisher
Life of this patent
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Abstract
Many variables in processes such as those using turbocompressors and turbines must be limited or constrained. Limit control loops are provided for the purpose of limiting these variables. By using a combination of closed loop and open loop limit control schemes, excursions into unfavorable operation can be more effectively avoided. Transition between open loop and closed loop may be enhanced by testing the direction and magnitude of the rate at which the limit variable is changing. If the rate of change indicates recovery is imminent, control is passed back to the closed loop limit control function.
Claims15
An apparatus for providing limit control, not antisurge control, of a compression process having a limit variable, L, values of said limit variable being divided into a first region wherein closed loop limit control is used and a second region in which open loop limit control is used, the apparatus comprising:
- (a) a first calculator for calculating the value of the limit variable, L, based on parameters associated with a turbocompressor;
- (b) a closed loop limit controller in effect when the value of the limit variable, L, is in the first region;
- and
- (c) an open loop limit controller in effect when the value of the limit variable, L, is in the second region.
A apparatus for providing limit control of a process having a limit variable, L, values of said limit variable being divided into a first region wherein closed loop limit control is used and a second region in which open loop limit control is used, the apparatus comprising:
- (a) an open loop limit controller, in effect when the value of a limit variable, L, is in the second region;
- (b) a derivative calculator for calculating a value of a first temporal derivative, dL/dt, of the limit variable, L;
- and
- (c) a closed loop limit controller in effect if the value of the first temporal derivative, dL/dt, has a sign indicating the value of L is changing toward the first region.
Dependencies are inferred from the claim text.