Steam Turbine Startup Control via Release Points
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Solution Overview
Problem
The rapid startup of large steam turbines is challenging due to critical thermal stresses and mechanical limitations, and existing methods lack a stable and robust control mechanism to efficiently manage startup processes in response to fluctuating electrical power demands.
Innovation Solution
A method of controlling a steam turbine by selecting predefined startup sequences based on the turbine's status and operator-defined modes, using a steam turbine controller to manage directly controllable parameters like rotor speed and load, while indirectly controlling steam temperature and pressure through a separate controller, with strategically placed release points to ensure thermal stress management and deterministic startup timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the startup procedure is accelerated to respond to fluctuating electrical power demand, then productivity and adaptability improve, but thermal stresses and mechanical risks increase
Solution Approach 1:
The startup procedure is divided into multiple discrete phases (cold startup, hot startup, startup from trip) with predefined sequences of setpoints. Each phase has specific control strategies tailored to its characteristics, allowing optimized startup speed for each condition while managing thermal stresses appropriately.
Solution Approach 2:
Predefined startup sequences and setpoints are prepared in advance for different operating conditions. The system pre-establishes control parameters and procedures before actual startup occurs, enabling rapid response to power demand fluctuations without ad-hoc decision-making delays.
2Reliability
If feedback control is used to manage thermal stresses during startup, then reliability improves, but control complexity increases
Solution Approach 1:
The control system dynamically adapts its behavior based on the selected startup phase and current operating conditions. Different control strategies are applied automatically depending on whether the system is in cold startup, hot startup, or startup from trip mode, optimizing reliability without requiring a single complex universal controller.
Solution Approach 2:
The system continuously monitors actual parameters against predefined setpoints and adjusts control actions accordingly. Release points are defined where actual values must agree with predefined values before proceeding, ensuring thermal stress limits are respected while maintaining systematic control.
3Adaptability or versatility
If direct control of steam generator is implemented by steam turbine controller, then adaptability improves, but system stability may deteriorate
Solution Approach 1:
Control authority is segmented between the steam turbine controller and boiler controller based on the startup phase. The steam turbine controller has authority over turbine-specific parameters, while the boiler controller manages steam generator parameters. This segmentation allows each controller to optimize its domain without causing system-wide instability.
Solution Approach 2:
Predefined startup sequences and release points act as intermediaries between the steam turbine controller and boiler controller. These predefined protocols mediate the interaction between the two controllers, ensuring coordinated action that maintains system stability while achieving the desired 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 a stable, robust, and efficient startup process that reduces thermal stress risks and allows for accurate prediction of startup time, enhancing the flexibility of steam power plants to respond to electrical power fluctuations.
Implementation Method 1
axial steam turbines comprising radially arranged fixed stator blades or vanes alternating with radially arrangements of moving rotor blades force-coupled by a flow of steam through the turbine
Implementation Method 2
a steam turbine controller controlling at least the position of a steam inlet valve located in a steam conduit between the steam generator and the steam turbine to control the mass flow into the steam turbine
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A method of controlling a steam turbine receiving steam from a steam generator and having a rotor linked to a power generator and a steam turbine controller controlling at least the position of a steam inlet valve located in a steam conduit between the steam generator and the steam turbine to control the mass flow into the steam turbine is described including the steps of before beginning of the startup selecting a predefined set of startup sequences of setpoints based on a status of the steam turbine at the beginning of the startup and/or a startup mode chosen by the operator wherein the set of startup sequences of setpoints includes parameters not (directly) controlled by the steam turbine controller and parameters (directly) controlled by the steam turbine controller; using the steam turbine controller to control the parameters controlled by the steam turbine controller so as to progress the steam turbine from setpoint to setpoint in accordance with the predefined set of startup sequences until reaching a release point; and at the release point delaying the move to the next setpoint until actual setpoint values agree with the predefined setpoint values at the release point for the parameters not (directly) controlled by the steam turbine controller.