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I have a set of 4 pumps i.e. two VFD pumps and two AC fixed speed pumps. The two VFD speed are controlled via one flow PID controller. The controller output feeds both VFD pumps to control the speed at the same time (whichever VFD is running).
the problem is whenever operation is switching between the two VFD pumps or putting a new pump online, the flow spikes up before the PID brings it back down to the set point. The flow overshoot violates some water downstream filters capacity and creates water quality violations.
The PID is tuned to act very slow since the setpoint doesn't changed often.
I am using Schneider Electric PIDP function block (PID in the parallel form).
What is your thoughts of the control scheme and how can I prevent this flow overshoot when switching between the VFD pumps or putting a new pump online. Is it a tuning issue, which I don't think so, or is it a control scheme issue.
the problem is whenever operation is switching between the two VFD pumps or putting a new pump online, the flow spikes up before the PID brings it back down to the set point. The flow overshoot violates some water downstream filters capacity and creates water quality violations.
The PID is tuned to act very slow since the setpoint doesn't changed often.
I am using Schneider Electric PIDP function block (PID in the parallel form).
What is your thoughts of the control scheme and how can I prevent this flow overshoot when switching between the VFD pumps or putting a new pump online. Is it a tuning issue, which I don't think so, or is it a control scheme issue.