Method for preventing surge in a dynamic compressor using adaptive preventer control system and adaptive safety margin
A method of preventing surge in a dynamic compressor is disclosed. The method includes providing an anti-surge valve having an adjustable opening for increasing the flow through a dynamic compressor. The next step is sensing process conditions in the dynamic control to determine a compressor load variable. A control system estimates a process disturbance model using the compressor load variable. The control system then adjusts a safety margin using a rate limited response and initiates a closed loop response using process feedback based on the process disturbance model. The control system adjusts the opening of the anti-surge valve according to the safety margin and closed loop response.
1. A method of preventing surge in a dynamic compressor, the method comprising the steps of:
providing a surge valve having an adjustable opening for increasing a flow through the dynamic compressor;
sensing process conditions in the dynamic compressor to determine a compressor load variable;
estimating a process disturbance model using the compressor load variable; and
initiating a closed loop control response to open the surge valve based on the process disturbance model wherein the closed loop control response is initiated by opening the surge valve as a function of a compressor dynamic operating point distance from a surge limit line wherein the surge valve is opened in a step response.
2. The method of claim 1 wherein the compressor load variable is determined based on a compressor driver power.
3. The method of claim 2 wherein a compressor driver is selected from the group consisting of a motor, steam turbine and gas turbine.
4. The method of claim 1 wherein the compressor load variable is based on compressor driver rotating speed.
5. The method of claim 1 wherein the compressor load variable is determined based on a system process variable.
6. The method of claim 5 wherein the system process variable is a header pressure or flow of a process associated with the compressor.
7. The method of claim 1 wherein the compressor load variable is determined based on mathematical modeling of a system component.
8. The method of claim 1 wherein the process disturbance model is estimated by using a digital derivative of the compressor load variable.
9. The method of claim 1 wherein the process disturbance model is estimated by using a delayed response of the compressor load variable.
10. The method of claim 1 wherein the process disturbance model is estimated by using a filter response of the compressor load variable.
11. The method of claim 1 wherein a surge model response of the compressor load is determined when a rate of change of the compressor load variable exceeds a defined limit.
12. The method of claim 11 wherein the compressor load variable is a flow of the compressor.
13. The method of claim 11 wherein the compressor load variable is a temperature measurement associated with the compressor.
14. The method of claim 11 wherein the compressor load variable is a pressure measurement associated with the compressor.
15. The method of claim 11 wherein the compressor load variable is a distance of the compressor operating point from the surge limit line.
16. The method of claim 11 wherein the compressor load variable is a power of a compressor driver.
17. The method of claim 11 wherein the compressor load variable is a speed of the compressor.
18. The method of claim 1 further comprising the step of differentiating a steady state response from process disturbance upsets.
19. The method of claim 1 wherein the step opening is a fixed rate of opening.
20. The method of claim 1 wherein the step opening is a varied rate of opening based upon the response of the process disturbance model.
21. The method of claim 1 wherein the surge valve is opened if a distance from the compressor dynamic operating point of the compressor to the surge limit line is at a distance less than a predetermined set point.
22. The method of claim 1 wherein the surge valve is closed using a rate limited response once a predetermined set point is exceeded.
23. The method of claim 22 wherein a rate of closure of the surge valve is adjusted based on the closed loop response.
24. The method of claim 22 wherein a rate of closure of the surge valve is adjusted based on the distance of the compressor dynamic operating point from the surge limit line.
25. The method of claim 1 wherein the compressor load variable is determined from at least two of a group consisting of the operating point as a function of the surge limit, power of a compressor driver, rotating speed of the compressor driver, and a system process variable.
26. A method of preventing surge in a dynamic compressor, the method comprising the steps of:
providing a surge valve having an adjustable opening for increasing flow through the dynamic compressor;
sensing process conditions in the dynamic compressor to determine a compressor load variable;
estimating a process disturbance model using the compressor load variable; and
initiating a closed loop control response to open the surge valve based on the process disturbance mode wherein the closed loop control response is initiated by opening the surge valve as a function of a compressor dynamic operating point distance from a surge limit line wherein the surge valve is opened in a ramp response.
27. The method of claim 26 wherein the ramp rate of response is a fixed rate of opening.
28. The method of claim 26 wherein the ramp rate of response is a varied rate of opening based upon the response of the process disburbance model.