What is single-impulse adjustment and three-impulse adjustment of boiler water level?

In the process of boiler water level control, the adjustment method in which the drum water level is used as the feedback signal is called the single-impulse adjustment of the boiler water level.Single-impulse water level control is the simplest and most basic form of automatic control of boiler drum water level.

The three-impulse water level adjustment is in the process of automatic water level control, according to the three impulses of the drum water level, feed water flow, and steam flow through PID calculation to adjust the opening of the feed water valve, so as to achieve the purpose of automatic control of the feed water flow.Three-impulse regulation is actually a cascade control system with a feedforward signal.The liquid level controller and the flow controller constitute a cascade control system.Drum level is the primary variable and feed water flow is the secondary variable.The introduction of secondary variables enables the system to have a strong ability to overcome fluctuations in feedwater pressure (flow).The signal of the steam flow is introduced as a feedforward signal.Because the fluctuation of the steam flow is a factor that causes the change of the liquid level of the steam drum, it is a disturbance. When the steam flow fluctuates, the flow controller is introduced through the measurement to make the feed water flow change accordingly, so this is controlled according to the amount of disturbance. is feedforward.