Steam Drum Level Control Using Sliding Setpoint Prediction
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Solution Overview
Problem
Current heat recovery steam generation systems face challenges in accurately controlling the water level in steam drums, particularly during transient changes, which can lead to plant trips and inefficiencies due to the limitations of existing level control systems.
Innovation Solution
A method and controller that predict transient changes in water level or pressure in the steam drum using plant characteristics, such as steam flow, drum pressure, and gas turbine load, and generate a sliding setpoint to adjust the water level, combining data-based and physics-based models to improve control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional level control systems are used in HRSG, then the system structure is simple, but the control accuracy during transient changes is poor leading to plant trips
Solution Approach 1:
The controller predicts future water level changes by analyzing current transient conditions (steam flow, drum pressure, gas turbine load) and proactively adjusts the feedwater valve position before the actual level deviation occurs. This anticipatory control prevents plant trips by maintaining water level within acceptable ranges during transient operations.
Solution Approach 2:
The system continuously monitors multiple parameters (steam flow, drum pressure, water level, gas turbine load) and uses this feedback to dynamically adjust the feedwater valve position. The controller compares actual water level with predicted level and modifies control actions to maintain accuracy during transient changes.
2Speed
If a sliding setpoint is generated based on transient prediction, then the responsiveness to water level changes is improved, but the computational complexity increases
Solution Approach 1:
The sliding setpoint is generated by predicting future water level behavior based on current transient conditions. This predicted setpoint is calculated in advance and used to guide feedwater valve adjustments, enabling the system to respond proactively to anticipated level changes rather than reactively to actual deviations.
Solution Approach 2:
The setpoint is not fixed but dynamically adjusted as a sliding setpoint that changes with transient conditions. The controller continuously updates the predicted water level trajectory and adjusts the setpoint accordingly, allowing the system to adapt rapidly to changing operating conditions while maintaining computational efficiency.
Data Source
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AI summary
A method of controlling a water level in a steam drum includes predicting a transient in the steam drum based on plant characteristics including steam flow from the steam drum, drum pressure in the steam drum, and one or both of a gas turbine load and a position of a bypass valve configured to control the steam flow from the steam drum to two or more steam flow conduits. The method further includes generating a sliding setpoint to control the water level based on predicting the transient in the steam drum.