Dynamic Matrix Control for Steam Temperature Stability
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Solution Overview
Problem
Current steam temperature control in boiler systems, particularly in steam generating systems, faces challenges in managing short-term fluctuations and reactive control responses, leading to stress on components and reduced efficiency due to the reactionary nature of cascaded PID controllers.
Innovation Solution
Implementing a dynamic matrix control (DMC) technique that uses feed forward control, which receives signals for the rate of change of disturbance variables and actual/ setpoint values to generate control signals, eliminating radical swings and overshoots, and optionally incorporating a derivative dynamic matrix control block for enhanced response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If cascaded PID controllers are used for steam temperature control, then the system can maintain stable temperature over time, but the control response is reactive and causes radical swings and overshoots that stress boiler components
Solution Approach 1:
The dynamic matrix control block receives signals indicative of the rate of change of disturbance variables and generates control signals in advance before temperature errors occur. This predictive action prevents radical swings and overshoots, reducing stress on boiler components while maintaining temperature stability.
Solution Approach 2:
The control system uses feedback from actual temperature measurements and disturbance variable rates to continuously adjust control signals. The dynamic matrix control block processes this feedback along with predictive information to generate optimal control actions that maintain stability without causing component stress.
2Ease of operation
If traditional feedback control is used, then the system responds to temperature errors, but the reactive nature causes temperature fluctuations and reduces control precision
Solution Approach 1:
By receiving signals indicative of the rate of change of disturbance variables, the dynamic matrix control block predicts future temperature trends and generates control signals before errors occur. This preliminary action eliminates the lag inherent in traditional feedback control, providing both responsiveness and precision.
Solution Approach 2:
The patent replaces traditional mechanical PID control mechanisms with a dynamic matrix control system that uses computational algorithms to process disturbance variables and generate optimal control signals. This substitution enables predictive control that maintains precision while improving responsiveness.
3Temperature
If the firing rate to feedwater ratio is changed to regulate steam temperature, then the primary temperature control is achieved, but short-term fluctuations cannot be controlled effectively
Solution Approach 1:
The dynamic matrix control block receives signals of the rate of change of disturbance variables and generates control signals in advance, enabling the system to respond to short-term temperature fluctuations before they develop into significant deviations. This predictive approach maintains effective temperature regulation while improving response speed.
Solution Approach 2:
The control system transitions from static PID parameters to dynamic matrix control that adapts to changing operating conditions. The dynamic nature of the control block allows it to respond effectively to both primary temperature regulation and short-term fluctuations across varying load levels.
Data Source
AI summary
A technique of controlling a steam generating boiler system includes using a rate of change of disturbance variables to control operation of a portion of the boiler system, and in particular, to control a temperature of output steam to a turbine. The technique uses a primary dynamic matrix control (DMC) block to control a field device that, at least in part, affects the output steam temperature. The primary DMC block uses the rate of change of a disturbance variable, a current output steam temperature, and an output steam temperature setpoint as inputs to generate a control signal. A derivative DMC block may be included to provide a boost signal based on the rate of change of the disturbance variable and/or other desired weighting. The boost signal is combined the control output of the primary DMC block to more quickly control the output steam temperature towards its desired level.