Dynamic Standby Load Control for Combined Cycle Plant Startup
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Solution Overview
Problem
Combined cycle plants face prolonged startup times due to fixed standby load settings for gas turbines based on steam turbine metal temperatures, leading to inefficient load increase rates, especially when temperature differences are minor, resulting in increased startup times.
Innovation Solution
Implementing a control system that dynamically adjusts the standby load and increasing load rate of the gas and steam turbines in response to steam turbine metal temperature, with varying rates in different temperature regions to optimize performance and reduce thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the standby load for the gas turbine is set to a low value (e.g., 10%) for cold start-up, then thermal stress on the steam turbine is reduced, but the time required to increase the load to full capacity is extended
Solution Approach 1:
The patent applies dynamics by transitioning from fixed standby load settings to dynamic adjustment based on steam turbine metal temperature. The control device continuously monitors metal temperature and adjusts the standby load accordingly, enabling the system to adapt between conservative low-load mode (when temperature is low) and aggressive high-load mode (when temperature is high), thereby resolving the contradiction between thermal stress reduction and startup time minimization
Solution Approach 2:
The patent changes the parameter of standby load from a fixed value to a variable that depends on metal temperature. By establishing a functional relationship where standby load = f(metal temperature), the system optimizes the balance between thermal stress management and load increase speed, directly addressing the technical contradiction
2Productivity
If the standby load for the gas turbine is increased to reduce startup time, then power generation capability is improved, but thermal stress on the steam turbine increases
Solution Approach 1:
The patent implements feedback control where the metal temperature of the steam turbine is continuously measured and fed back to the control device. Based on this feedback, the control device adjusts the standby load of the gas turbine in real-time, ensuring that high power generation capability is achieved only when thermal conditions permit, thus resolving the contradiction between productivity and thermal stress
3Device complexity
If fixed standby load settings are used for different metal temperature ranges, then control simplicity is maintained, but startup time increases due to abrupt changes at temperature boundaries
Solution Approach 1:
The patent transitions from static, fixed standby load settings to dynamic adjustment based on continuous metal temperature monitoring. This allows smooth transitions between different operating modes rather than abrupt changes at fixed temperature boundaries, reducing startup time while maintaining manageable control complexity through automated temperature-based decision logic
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 reduces the load zone for simultaneous gas and steam turbine load increases, shortening startup times and optimizing power generation by aligning load settings with temperature changes, while minimizing thermal stress.
Implementation Method 1
a heat recovery steam generator recovers exhaust gas of the gas turbine and generates steam
Data Source
Figure 1
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Figure 4~5
AI summary
A combined cycle plant, a device for controlling a combined cycle plant, and a method for activating a combined cycle plant, wherein the time for starting up the combined cycle plant can be shortened by providing: a gas turbine (11) having a compressor (21), a combustor (22), and a turbine (23); a waste heat recovery boiler (12) for producing steam using the waste heat of exhaust gas from the gas turbine (11); a steam turbine (13) driven by the steam produced by the waste heat recovery boiler (12); and a control device (50) that implements settings so that the standby load when the gas turbine (11) is started up continuously changes in accordance with changes in the metal temperature of the steam turbine (13).