Three-pulse control for drum liquid level?

Water level control using three impulses: 1) In abnormal situations, such as when the water level deviates significantly from the normal value, rule-based control is employed to quickly restore the water level and ensure the safe and stable operation of the boiler. 2) When there is a conflict between water level control and main steam temperature control, coordinated control of the two can be carried out based on the primary aspect of the conflict. 3) It comprises two control loops: a feedwater flow control loop and a drum level control loop; essentially, it is a composite control system consisting of a steam flow feedforward control and a level-flow cascade system. When the steam flow rate changes, the feedwater flow control circuit in the boiler drum level control system can rapidly adjust the water supply volume to carry out coarse adjustment, after which the drum level regulator handles the fine adjustment of the level

Well, for example, if the effect of changes in steam flow on the output value of the water flow regulator is 2, and the effect of the level-flow cascade control system on that same output value is 3, then is there a system that can adjust this effect if I think that the influence of steam flow changes on the output value of the water flow regulator is too large or too small? I’m not referring to the tuning of the regulator’s PID parameters, but rather an interface similar to those used in advanced control, where the correlation values between various disturbances and the controlled variable can be modified

A three-impulse control system refers primarily to a boiler drum level control system in which signals corresponding to the drum level, steam flow rate, and feedwater flow rate are introduced. After certain calculations, these signals are used together to control a single control valve – the feedwater valve. The liquid level signal is the controlled variable of this system; it is the main process parameter that reflects the operating condition of the boiler’s drum, and it is also an essential indicator to ensure the safe operation of the boiler. The purpose of introducing the steam flow signal is to promptly counteract the impact of steam flow fluctuations on the drum level, and to effectively prevent malfunctioning of the control system caused by the \"false level\" phenomenon. The purpose of introducing the feedwater flow rate signal is to use the feedwater flow rate as a secondary variable, and take advantage of the rapid ability of the secondary loop in a cascade control system to overcome disturbances, thereby addressing in a timely manner the impact of changes in feedwater pressure on the drum level.

When these three signals enter the control system, it is possible to selectively amplify a certain signal, such as the steam flow rate, in order to enhance the influence of the steam flow rate on the water supply control valve. Is it the adjustment interface on DCS? You ask this because, with a cascade control system based solely on level and flow rates, it is easy to tune the PID parameters for each of the primary and secondary loops in order to achieve both sensitivity and stability in controlling the water flow rate. However, when a third parameter is introduced, things probably won’t be that simple. So, a question.

All of these are descriptions related to the three-momentum principle; could someone provide a specific practical example? That would make it more practical and experience-based; simulations will always differ from the actual conditions on site, right? At the same time, when there are changes in my steam generation volume, with the three impulses being primarily focused on steam production, how are the other two quantities coordinated?

Support the view from the second floor. Under normal circumstances, using this as a reference for operations is sufficient.

Using three impulse control for regulating the water level in the boiler drum is currently the best method for level control. However, when selecting the level gauge, steam flow meter, and feedwater pump flow meter, it is necessary to consider various factors carefully; for example, determining which type of steam flow meter offers the highest accuracy, as well as taking into account the pipe friction losses associated with those flow meters； Additionally, for the inside of the boiler drum, since it is normally filled with a mixture of steam and water, careful consideration must be given when selecting a level gauge.

I have a question here: Three-impulse control uses the liquid level, steam flow rate, and feedwater flow rate to control the control valve. But is fixed drainage taken into account in this system? How is the water volume from such drainage included in the three-impulse control system, and how are the feedback signals set?； Because if this issue is ignored, the amount of steam output will definitely be less than the amount of water input, and the data fed back into the three-element control system will be inaccurate, leading to control errors. Who can help solve this problem?

Three-input regulation for boiler level is well-established, and there are many discussions on this topic in relevant journals

In three-impulse control, the steam flow rate is used as a feedforward signal, which is added to the output of the outer-loop PID calculation based on the liquid level (via an adder). The signal resulting from this addition is then compared with the water volume to serve as the inner-loop PID signal, which is used to adjust the water volume. More specifically, when the bubble level rises and the signal increases compared to the set level, the outer-loop PID will output a signal to increase the valve position. This signal, when added to the steam flow rate (which remains constant at this point), results in an increased output signal. In turn, when this is compared to the set water volume, it causes the inner-loop PID to reduce the valve position. So after some time, the bubble level will drop. Stable control is achieved. When the drum load increases, that is, when the steam flow rate rises, the output of the adder also increases (with the liquid level remaining constant); as a result, the feedwater valve opens wider, thereby increasing the amount of feedwater supplied. When the steam load increases suddenly, resulting in a \"false level,\" the increase in liquid level becomes greater, but the steam flow decreases; therefore, the output of the adder remains unchanged, the control valve stays the same, and the system remains stable.