Combined Cycle Power Plant Block Loading via Islanding Mode
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Solution Overview
Problem
Combined cycle power plants face challenges in efficiently adjusting power output to meet variable electrical grid demands, particularly after a blackout, due to the need for independent operation of gas and steam turbines and limitations in flexible loading paths.
Innovation Solution
A control system and methodology that allows a combined cycle power plant to operate in islanding mode, with independent control of gas turbine fuel flow and airflow, enabling temperature matching of gas turbine exhaust with steam turbine conditions, and using a heat recovery steam generator to manage steam production for concurrent block loading of the electrical grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the combined cycle power plant operates with both gas turbine and steam turbine systems synchronized, then the power output is stable and efficient, but the response time for grid restoration is slow due to interdependence
Solution Approach 1:
The patent segments the combined cycle power plant into independent gas turbine and steam turbine systems. The gas turbine can operate independently in islanding mode to provide immediate power output, while the steam turbine system remains offline or operates separately. This segmentation eliminates the interdependence that normally requires synchronized operation, enabling rapid grid restoration without compromising eventual stable operation when both systems work together.
2Productivity
If the gas turbine operates at high load to quickly restore grid power, then the response speed is improved, but the steam turbine cannot be properly loaded due to temperature mismatch
Solution Approach 1:
The patent implements dynamic control of the gas turbine operating parameters, specifically adjusting fuel flow and air flow to control exhaust temperature. This dynamic adjustment allows the gas turbine to operate at high load for rapid power restoration while simultaneously controlling exhaust temperature to match steam turbine requirements. The system transitions from static operating conditions to dynamic control, enabling both high productivity and loading flexibility.
Solution Approach 2:
The patent changes key operating parameters of the gas turbine, particularly exhaust temperature, fuel flow rate, and air flow rate. By controlling these parameters, the system can deliver high power output while ensuring the exhaust temperature matches the steam turbine's thermal requirements. This parameter control enables the gas turbine to adapt its operation to simultaneously satisfy power delivery needs and steam turbine loading requirements.
3Stability of the object's composition
If the steam turbine is warmed up using traditional methods, then the thermal conditions are stable, but the overall block loading process takes longer
Solution Approach 1:
The patent applies preliminary action by using the gas turbine to preheat the steam turbine system before full synchronization. The gas turbine operates first, generating power while its exhaust or dedicated heating system warms up the steam turbine components. This preliminary thermal conditioning prepares the steam turbine for rapid loading without requiring traditional slow warmup procedures, reducing overall startup time while maintaining thermal stability.
Solution Approach 2:
The patent ensures continuous useful action by having the gas turbine operate continuously during the steam turbine warmup process. Rather than idle waiting periods, the gas turbine continuously generates power to restore the grid while simultaneously providing thermal energy to warm the steam turbine. This continuous dual-purpose operation eliminates wasted time and maintains both power output and thermal stability throughout the process.
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 rapid and flexible electrical grid restoration by allowing the gas and steam turbines to operate independently, reducing startup times, and ensuring stable grid frequency and steam operational conditions, thereby enhancing the power plant's output and response to variable loads.
Implementation Method 1
The steam turbine system includes a heat recovery steam generator, the method further includes flowing gas turbine exhaust gas to the heat recovery steam generator of the steam turbine system
Implementation Method 2
controlling gas turbine exhaust fed to the steam turbine system and the gas turbine exhaust temperature heats the steam turbine system and to meet temperature matching conditions of the steam turbine system
Data Source
AI summary
A method for block loading an electrical grid with a combined cycle power plant (CCPP) includes operating a gas turbine system of the CCPP in an islanding mode with a steam turbine system of the CCPP off line with turning gear rotating only; loading the steam turbine system accordingly to temperature matching conditions of the steam turbine system, the loading of the steam turbine system includes controlling gas turbine exhaust fed to the steam turbine system and the gas turbine exhaust temperature heats the steam turbine system and to meet temperature matching conditions of the steam turbine system; wherein controlling gas turbine exhaust includes controlling fuel flow and air flow to the gas turbine system; and operating at least one of the gas turbine system and steam turbine system to block load the electrical grid from a load on at least one of gas turbine system and steam turbine system.