Main steam temperature reducing and water spraying control method and system for power station boiler

Abstract

The invention provides a main steam temperature reducing and water spraying control method and system for a power station boiler, and the method comprises the steps: carrying out the preprocessing ofa main steam temperature deviation, and obtaining a main steam temperature deviation after preprocessing; taking the main steam temperature deviation as an input variable after preprocessing, and combining a differential algorithm with the quick return characteristic to calculate and obtain main control output; subtracting the leading temperature by the value of the main control output to obtain aleading temperature control deviation; enabling a sub-modulation PI controller to output the subcontrol control output to a temperature reducing and water spraying adjustment valve for control through the leading temperature control deviation, and monitoring the leading temperature control deviation; triggering a tracking enabling signal to enable the output of the sub-modulation PI controller tobe forced to be unchanged if the leading temperature control deviation exceeds a preset threshold and the state that the leading temperature control deviation is greater than the preset threshold remains for a preset time period; and setting the main control output of a main modulation PID controller as a leading temperature value. The method improves the response sped of the system adjustment, and can remarkably improve the adjustment quality of the system.

Description

technical field [0001] The invention relates to the fields of electric power technology and thermal power generating set technology, in particular to a method and system for controlling the temperature reduction and water spraying of main steam of a power station boiler. Background technique [0002] With the development of science and technology, the automation control technology of thermal power plants is becoming more and more perfect, and the degree of automation of thermal power plants is getting higher and higher. However, at the same time as automatic control, the control technology of thermal power plants is also constantly improving, and the technical problems of unstable and inaccurate control that existed in the past have gradually been solved, such as boiler control technology in thermal power plants. [0003] The main steam temperature of the boiler is controlled by spraying cold water into the steam through the spray desuperheater, which is one of the most crit...

AI Technical Summary

Problems solved by technology

Almost all boiler main steam temperature control adopts the cascade control scheme, but when the cascade control scheme is adopted, the auxiliary controller cannot adopt the pure proportional control method due to the need to design the tracking function, and still adopts the PI controller. The auxiliary adjustment is not a follow-up system of pure proportional adjustment. When the deviation of the auxiliary adjustment is large and cannot be eliminated in time, when the main adjustment needs to reduce the temperature and spray water, the water spray control valve will immediately spray water in the opposite direction to the auxiliary adjustment. However, under the integral action of the secondary adjustment PI controller, sometimes the desuperheating and spraying control valve will still move in a direction that is not expected by the main adjustment, resulting in a delay in the response of the main steam temperature, thus affecting the response speed of the system adjustment , which reduces the regulation quality of the system

In addition, when the main steam temperature still fails to reach the set value after the desuperheating and water spraying regulating valve is completely closed, there will be an integral saturation phenomenon in the auxiliary regulator, which may cause serious overheating of the main steam temperature, which is not conducive to the safe operation of the unit , if the integral saturation technical measures are adopted, although the integral saturation phenomenon can be solved, when the temperature of the main steam rises when the temperature is very low, it will immediately cause the desuperheating and water spraying regulating valve to open, while the temperature of the main steam is still Very low, sprinkler control system opens prematurely

In addition, there is a desuperheating and spraying water regulating valve, which is not conducive to the recovery of steam temperature, and is also not conducive to the economical operation of the unit.

[0004] In order to improve the operating efficiency of the unit, the temperature of the main steam is usually operated close to the upper limit of the metal material of the pipeline. If the existing technology is used to reduce the temperature and spray water, it is easy to cause the temperature of the main steam to overheat, resulting in various overtemperature question

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