Dynamic Matrix Control of Steam Temperature with Saturated Steam Prevention
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Solution Overview
Problem
Current steam temperature control methods in boiler systems, particularly in superheater and reheater sections, face challenges in managing short-term fluctuations, leading to stress on the system and reduced component lifespan due to reactionary control responses and varying operating conditions.
Innovation Solution
A dynamic matrix control system that generates a control signal based on the rate of change of disturbance variables, adjusting the temperature of intermediate steam by determining the difference between saturated and intermediate steam temperatures, and using a fuzzifier unit to modify the control signal for precise temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional reactionary control methods are used to maintain steam temperature, then the system responds to temperature deviations after they occur, but this causes stress on system components and reduces component lifespan due to delayed responses
Solution Approach 1:
The control system performs preliminary action by detecting trends in steam temperature and anticipating future deviations before they occur. The system uses predictive algorithms to calculate expected temperature changes based on current rates of change, then pre-adjusts control parameters to prevent deviations rather than reacting after they occur, thereby extending component lifespan while maintaining timely control.
Solution Approach 2:
The system applies dynamics by continuously adapting control parameters based on changing operating conditions. The control algorithm dynamically adjusts gain factors and prediction horizons according to the current state of the boiler system, allowing the controller to optimize its predictive capability in real-time and respond proactively to temperature trends without causing excessive stress on components.
2Productivity
If the steam temperature is controlled to be higher, then the efficiency of the steam turbine increases, but the steam may cause damage to the turbine blades due to excessive temperature
Solution Approach 1:
The control system uses feedback from multiple temperature measurement points within the boiler to continuously monitor steam temperature trends. This feedback is fed into the predictive control algorithm, which calculates the optimal control signal to maintain steam temperature within the safe operating range that maximizes turbine efficiency while preventing blade damage from excessive temperatures.
Solution Approach 2:
The system changes control parameters dynamically based on operating conditions. By adjusting fuel flow rates, air supply, and other combustion parameters in real-time, the system maintains steam temperature within the optimal range for turbine efficiency while preventing it from reaching levels that would cause blade damage, thus resolving the contradiction between productivity and harmful effects.
3Object-affected harmful factors
If the steam temperature is controlled to be lower, then the risk of turbine blade damage decreases, but the steam may contain water particles that cause damage to turbine components and decrease efficiency
Solution Approach 1:
The control system uses feedback from temperature sensors to continuously monitor steam conditions and adjust combustion parameters to maintain steam temperature above the dew point. This ensures complete evaporation of water particles while preventing temperatures from rising to damage levels, thus maintaining both turbine safety and efficiency through precise temperature control.
Solution Approach 2:
The system applies partial action by making small, precise adjustments to combustion parameters rather than large changes. This allows the system to maintain steam temperature within a narrow optimal range that prevents both water particle formation and excessive heating, thereby avoiding turbine damage while maintaining efficiency through subtle, continuous control adjustments.
Data Source
AI summary
A technique of controlling a steam generating boiler system using dynamic matrix control includes preventing saturated steam from entering a superheater section. A dynamic matrix control block uses a rate of change of a disturbance variable, a current output steam temperature, and an output steam setpoint as inputs to generate a control signal. A prevention block modifies the control signal based on a saturated steam temperature and an intermediate steam temperature. In some embodiments, the control signal is modified based on a threshold and/or an adjustable function g(x). The modified control signal is used to control a field device that, at least in part, affects the intermediate steam and output steam of the boiler system. In some embodiments, the prevention block is included in the dynamic matrix control block.