3-Element Drum Level Control Simulation
Three-element boiler drum level control. A drum level controller trims the setpoint of a dedicated feedwater flow controller; a steam-flow feedforward term is added so feedwater tracks steam demand immediately. Based on Module 9 of Process Control: Modeling, Design, and Simulation by B. Wayne Bequette.
Variables are dimensionless deviation variables from the nominal operating point: level 0 is the desired operating level, flow 0 is the nominal feedwater flow, and ±1 represents a full-scale deviation. The feedwater valve icon displays 0 as 50% open (nominal), −1 as fully closed, and +1 as fully open.
Process Animation
Process Schematic (Module 9)
Figure from Bequette Module 9: LC + FC + steam-flow feedforward. The flow controller setpoint is the sum of the level controller output and the feedforward contribution from measured steam flow.
Closed-Loop Response
Level Loop — r / L / LC / d
Flow Loop — Fsp / Fw / V
Inputs & Disturbance
Controller Tuning
Process Model (Module 9)
Drum level to feedwater valve opening.
Feedwater valve dynamics.
Drum level to steam demand disturbance.
Three-element control structure:
where the flow controller tracks by adjusting the feedwater valve.