Multivariable Control Algorithm for HRSG Water Level and Steam Pressure
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Solution Overview
Problem
Heat recovery steam generators (HRSGs) face challenges in controlling multiple interdependent properties, such as liquid water level and steam pressure, as separate control algorithms can lead to undesired changes in related properties, making it difficult to achieve desired target values.
Innovation Solution
A multivariable control algorithm is implemented in the HRSG system, using error signals from measured properties to generate control signals for adjusting feed-water flow, steam flow, and heat input, considering the interdependencies between properties like liquid water level and steam pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate control algorithms are used for different HRSG properties, then each property can be controlled independently, but undesired changes in related properties occur making it difficult to attain target values
Solution Approach 1:
The patent combines multiple separate control algorithms into a unified multivariable control algorithm that simultaneously manages multiple interdependent properties (water level, steam pressure, gas flow rate) of the HRSG system. This integration allows the controller to coordinate adjustments across all properties, preventing undesired changes in one property when another is being controlled, thereby achieving target values for all properties simultaneously.
2Reliability
If multiple properties are controlled simultaneously with separate algorithms, then each property receives dedicated control attention, but the interdependence between properties causes control conflicts
Solution Approach 1:
The patent implements a feedback mechanism where the multivariable control algorithm continuously monitors multiple HRSG properties and adjusts control signals based on the interrelationships between them. The controller uses feedback from all monitored properties to make coordinated adjustments, ensuring that controlling one property does not destabilize another, thereby maintaining overall system stability while providing dedicated control attention to each property.
3Manufacturing precision
If a multivariable control algorithm is implemented to control multiple properties simultaneously, then target values for all properties can be attained, but the control system complexity increases
Solution Approach 1:
The patent employs a universal multivariable control algorithm that can handle multiple interdependent properties (water level, steam pressure, gas flow rate) within a single control framework. This multi-functional algorithm replaces the need for multiple separate control systems, achieving precise control of all properties simultaneously while actually reducing overall system complexity compared to having multiple independent control algorithms that must be coordinated.
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 allows for simultaneous and precise control of multiple HRSG properties, improving the system's ability to reach target values while minimizing undesired changes, enhancing operational stability and efficiency.
Implementation Method 1
hot gas flows across an evaporator, which converts liquid water in the evaporator to steam
Implementation Method 2
hot gas flows across an evaporator, which converts liquid water in the evaporator to steam
Data Source
AI summary
A method of controlling a heat recovery steam generator (HRSG) includes measuring a first regulated output of the HRSG and a second regulated output of the HRSG. The method includes comparing the first regulated output to a first setpoint defining a first target output to generate a first error signal and comparing the second regulated output to a second setpoint defining a second target output to generate a second error signal. The method also includes generating, by a controller implementing a multivariable control algorithm having as inputs the first error signal and the second error signal, control signals to control the HRSG to adjust values of the first regulated output and the second regulated output.