ENGR: Clarification about droop and frequency control

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==> Automation List post by Mik...
To view or reply to this thread: http://www.control.com/thread/1253097292#1257102589


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Re: ENGR: Clarification about droop and frequency control
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CSA, you didn't comment previous post. I wonder if you have seen that control concept before. There is one more thing if anyoone can clarify it.

Droop control is a pure proportional-only control. Recently I have found out that steam pressure control by turbine controller is PI (proportional plus integral) control. Can anyone explain, why PI control is necessary in this case?

I can understand that integral component of a controller is needed every time when steady state response experiences offset. If that is not desired, then integral component must be added to integrate error and thus eliminate steady state error.
However, I don't fully uderstand why this is important when controlling steam pressure.
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