Flow level cascade control and conventional level control systems
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What are the advantages of flow-level cascade control compared to conventional level control systems? What’s the difference?
In cascade control, both the amplitude of level changes and flow rate variations are very small, resulting in good stability. With ordinary level control, the control process experiences large fluctuations.
Cascade control is a complex control method that consists of a primary and a secondary regulator; it offers strong suppression of control disturbances, resulting in stable and reliable control, whereas conventional control performs much worse in this regard.
If feeding is to be controlled, then cascade control of level and flow is better for controlling the mass ratio than a single-loop control based on level alone. If it is used to control discharge, then the control objectives for the two approaches are different. In a single-level control system, it is sufficient that the liquid level remains stable; whereas in a cascade control system for both level and flow, both parameters need to be taken into account simultaneously, with no distinction between primary and secondary aspects, which sets it apart from ordinary cascade control.
Since two parameters have been added, it is obvious that both the liquid level and the flow rate need to remain relatively stable. This is the greatest advantage. The difference is that one is a complex loop, while the other is a single closed-loop loop.