Hello,
What is reset windup?
I am reading books online for PID and I am not sure I understand what this means :
"You connect BKCAL_OUT to an upstream block's BKCAL_IN to prevent reset windup and provide bumpless transfer to closed loop control."
"
The behavior of the reset component depends on the FRSIPID_OPTS option Dynamic Reset Limit. If this option is selected, the BKCAL_OUT value of a downstream block is input to the reset calculation. Thus, if the downstream block(s) cannot act on the PID block output, the reset contribution is automatically limited, eliminating windup. If the option is not selected (the default) the reset contribution is clamped if a limit condition is indicated by the BKCAL_IN status and the calculated change in output will drive the output further into the limit."
Can someone help me understand what the above statement means with an example?
I have the following control strategy
1. Flow is controlled with pump (VFD driven)
2. The flow loop (module) is the master and pump VFD( in another module) is the slave. Flow is normally in AUTO and VFD in CAS (bypass mode, the flow output goes straight to VFD output).
3. The pump is independent from the flow and VFD setup. We just turn it on and off.
Problem:
When the pump is turned off (unexpectedly or manually), the flow-vfd is still trying to control flow setup and the VFD speed eventually goes too 100% trying to meet flow set point. But flow is 0 because pump is turned off.
When pump is turned on again, the flow instantly increases because VFD is at 100%.
Can windup help me with this problem? Of course, I can implement a process action to drive VFD to 0% each time pump is off, just curious about if winding can help.
Thank you kindly.
