Power Plant Startup Schedule Control for Thermal Stress Limits
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Solution Overview
Problem
Existing methods for optimizing power generation plant startup schedules to achieve the shortest startup time are hindered by discrepancies between predicted and actual thermal stress values, often requiring gentle startup curves to avoid thermal stress constraints, which can lead to prolonged startup times.
Innovation Solution
A startup control device and method that includes a determination unit to assess whether observed thermal stress values exceed predicted values during startup, with a speed adjustment unit instructing the startup timer to adjust the startup speed accordingly, allowing for real-time adjustment of the startup schedule to manage thermal stress within constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a sharp increase in fuel input is used to shorten startup time, then productivity is improved, but thermal stress constraints are violated
Solution Approach 1:
The patent applies dynamics by making the startup schedule adjustable and adaptable during the startup process. The control device dynamically modifies the predetermined startup schedule based on real-time comparisons between observed and predicted thermal stress values, allowing the system to transition from a static to a dynamic control approach that optimizes both startup time and thermal stress management.
Solution Approach 2:
The patent implements feedback by continuously monitoring observed thermal stress values during startup and comparing them with predicted values from the numerical model. This feedback mechanism enables the system to detect deviations between actual and predicted behavior and adjust the startup schedule accordingly, ensuring thermal stress constraints are not violated while minimizing startup time.
2Reliability
If a gentle startup curve is used to satisfy thermal stress constraints, then reliability is improved, but startup time increases
Solution Approach 1:
The system transitions from a static gentle startup curve to a dynamic schedule that adjusts in real-time. By making the startup schedule adaptable based on actual thermal stress observations, the system can maintain reliability through constraint satisfaction while reducing unnecessary time loss from overly conservative predetermined schedules.
Solution Approach 2:
The feedback mechanism allows the system to distinguish between cases where thermal stress is actually approaching constraints and cases where the numerical model predictions are overly conservative. This enables selective acceleration of the startup curve where safe, maintaining reliability while reducing startup time.
3Manufacturing precision
If numerical model predictions are used to determine startup schedule, then manufacturing precision is improved, but measurement precision of actual thermal stress is insufficient
Solution Approach 1:
The patent uses feedback to bridge the gap between numerical model predictions and actual thermal stress measurements. By continuously comparing observed values with predicted values and using this information to adjust the startup schedule, the system compensates for inaccuracies in both the numerical model and measurement capabilities, achieving better overall precision in startup schedule optimization.
Solution Approach 2:
The patent replaces direct thermal stress measurement with an indirect estimation approach using a numerical model that calculates thermal stress from measurable parameters like steam temperature and flow rate. This substitution enables precision in thermal stress assessment without requiring direct measurement capabilities that do not currently exist.
4Adaptability or versatility
If external influences and plant changes are considered, then adaptability is improved, but device complexity increases
Solution Approach 1:
The feedback mechanism provides adaptability by enabling the system to respond to actual thermal stress conditions and deviations from predictions. This relatively simple feedback loop allows the system to adapt to external influences and plant changes without requiring complex predictive models or control algorithms, maintaining device simplicity while improving adaptability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the power generation plant to start up as quickly as possible while ensuring thermal stress constraints are not exceeded, potentially achieving shorter startup times than traditional methods by dynamically adjusting the startup curve based on actual conditions.
Implementation Method 1
converts thermal energy of high-temperature and high-pressure steam into power to turn a generator
Implementation Method 2
a temperature difference occurs between the surface and the inside of the impeller, and thermal stress is generated in the impeller because of the difference in thermal elongation due to the temperature difference
Data Source
AI summary
A startup control device for adjusting a startup schedule during startup of a power generation plant, the device includes: a determining unit which determines, on the basis of a predicted value of a physical quantity corresponding to the elapsed time from startup when the power generation plant has started up on the basis of a prescribed optimal startup schedule, and an observed value of the physical quantity acquired during the startup of the power generation plant, whether the observed value will exceed the predicted value. The device also includes a speed adjusting unit which, if the determining unit determines that the observed value will exceed the predicted value, issues an instruction to decelerate the speed of progress of elapsed time from the startup in the optimal startup schedule; and a startup timer which progresses the elapsed time from the startup at a speed based on the instruction.