Drum level control system

Abstract

The invention discloses a drum level control system comprising a main PID1 (Portion Integration Differentiation) control loop, an auxiliary PID2 control loop and an output correction module, wherein the main PID1 control loop takes a drum level as a target set value, the auxiliary PID2 control loop takes vapor output as a target set value, the main PID1 control loop and the auxiliary PID2 controlloop operate in parallel to calculate the opening value of a steam drum feed valve; the output correction module comprises a drum level change rate correction submodule and a water feed adjusting valve opening self learning submodule and is used for correcting the opening output of a water feed adjusting valve by tracing and judging the drum level fluctuation slope with the assistance of the opening self learning results of the water feed adjusting valve. The drum level control system can effectively maintain the stable drum level, and can response the condition of large water level fluctuation positively, so that a steam drum system can operate more safely and water level control become more stable. The drum level control system can be widely applied to drum level control in electric power, metallurgy and other industries.

Description

technical field [0001] The invention relates to an automatic water supply control system for a steam drum in a boiler. Background technique [0002] The steam drum is a device for steam-water separation. There is a large amount of steam-water mixture in the steam drum. The steam drum water level system is a nonlinear system with large lag. When the volume of the steam drum is constant, the larger the evaporation, the smaller the water capacity, and the less water storage that is allowed to fluctuate, so the requirements for the control of the water level of the steam drum are higher. At present, there are mainly single-impulse single-PID automatic control, three-impulse single-PID automatic control and cascade control schemes for steam drum water level control. [0003] The water level single-pulse single-PID automatic control scheme takes the steam drum water level as the PID control target, and realizes the control of the water level through the automatic adjustment of th...

AI Technical Summary

Problems solved by technology

In actual operation, there are many factors affecting the drum water level, and the dynamic characteristics of the drum water level are very complex. Due to the "false water level" characteristic in the drum water level system, the dynamic characteristics of the relevant parameters such as the water level when the drum load rises and falls The curve is asymmetrical, and the system parameters have time-varying characteristics, which brings difficulties to the automatic control of the drum water level

The conventional three-impulse single-PID or cascade control system cannot find control parameters that can adapt to various disturbances, and it is still unable to quickly restore the flow balance and water level balance of the medium in and out of the steam drum when the large water level fluctuates, thus affecting the control effect and safety of the water level and lack of prediction of the water level trend, taking passive measures to suppress and eliminate the existing water level deviation will easily lead to a long time for the system to restore stability, overshooting of the steam drum water level, frequent alarms, unstable oscillation of the system, and even divergence of control deviations

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