Steam Turbine Valve Feed-Forward Compensation During Online Testing
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Solution Overview
Problem
Steam turbine systems face challenges during online valve testing due to increased operational parameters and hindered control schemes caused by frequent valve closure, opening, and reopening, which disrupts the flow demand and efficiency of the turbine.
Innovation Solution
A controller system that uses feed-forward valve flow compensation techniques to maintain total flow demand by recalibrating remaining valves during operational testing, either by adding or subtracting the flow demand contribution of the tested valve, and adjusting valve strokes to minimize flow disturbance, applicable to both partial and full arc admission configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If online valve testing is performed by frequently closing, opening, and reopening turbine valves, then valve operational characteristics can be tested, but the pressure of the steam turbine increases and flow demand is disrupted
Solution Approach 1:
The controller pre-calculates compensation values for remaining valves based on the tested valve's characteristics and operating conditions before the valve test begins. This preliminary calculation enables the controller to quickly adjust remaining valves during testing without causing pressure fluctuations, as the compensation strategy is prepared in advance.
Solution Approach 2:
The system continuously monitors the actual pressure and flow conditions during valve testing and dynamically adjusts the compensation signals sent to remaining valves. This real-time feedback mechanism ensures that any deviations from expected behavior are corrected immediately, maintaining stable turbine pressure throughout the testing process.
2Reliability
If online valve testing is performed with frequent valve operations, then valve performance can be evaluated, but control schemes are hindered and flow demand is disrupted
Solution Approach 1:
The controller extracts the tested valve from the normal control scheme during testing operations, isolating it from the active control loop. The compensation mechanism then calculates and applies equivalent control actions through remaining valves, effectively removing the tested valve's disruptive influence while maintaining overall system control integrity.
Solution Approach 2:
The system dynamically changes control parameters for remaining valves based on the tested valve's position and characteristics. By adjusting stroke positions, flow coefficients, and compensation factors in real-time, the controller maintains smooth operation despite the tested valve being outside the normal control scheme.
3Reliability
If a valve is decoupled for testing, then the valve can be tested independently, but the total flow demand value changes
Solution Approach 1:
The controller calculates compensation signals for remaining valves that counterbalance the flow change caused by the decoupled tested valve. By applying equal and opposite flow adjustments through remaining valves, the system maintains constant total flow demand to the turbine despite the tested valve being removed from service.
Solution Approach 2:
The controller merges the control functions of the tested valve with remaining valves during testing. By combining the compensation capabilities of multiple remaining valves to replace the single tested valve's flow contribution, the system maintains total flow demand while enabling independent valve testing.
Data Source
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AI summary
A system (10) includes a controller (18) including a processor (24) configured to execute a program stored in a memory of the controller to generate and transmit a first output (68) comprising a total flow demand value (30) to a plurality of valves (26,27,28,29) communicatively coupled to the controller. Each of the plurality of valves (26,27,28,29) is configured to receive a respective portion of the total flow demand value (30). The processor (24) is configured to receive an input indicative of a decoupling of a first valve (27) of the plurality of valves and to generate a second output (69) based at least in part on the first output (68) and a first operational characteristic of the first valve (27). The second output (69) is configured to vary a second operational characteristic of a second valve (26,28,29) of the plurality of valves to maintain the total flow demand value (30).