Pump load sharing, PID for pumps

Dear Friends,

In my project, 4 pumps connected with one common header. I want to maintain the required pressure in that common header. In first cycle P1 is on, Actual pressure is not matched with required pressure P2 is on, if it is not matched then P3 . I have a VFD for speed control. How can i make a load sharing between pumps? explain about this PID control

note: components are AC500 PLC+ VFD+ CP600 HMI


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vigneshwaran92rce   

asked 2 months ago
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Answers

0

Hi

If you have a 4-20 mA pressure transducer, you can optimize PID directly inside VFD, for example ACS/Q 580 series by ABB.

Particulary, ABB have PFC macro developed specially for pump control.


Of course the PID regulation could be realize with PLC.


Hope this help you

Flavio Mussolin   

answered 2 months ago


 


By vigneshwaran92rce on 9/28/2017 | Like (0) | Report

That's not a abb vfd, that is altivar VFD . Kindly give a suggestion related to abb plc


By Flavio Mussolin on 9/28/2017 | Like (0) | Report

You can create inside PLC one routine based on time of functioning, for example, to create a work time in rotation for every pump.

The output to the drive need connect to every pump with a different contactor, in this case the PLC pid is used with a single pump. If you have to use two or more pumps due to a decrease in pressure, you must activate it directly by a contactor (power relay) the 2nd pump, the third....
The above is the short description that PFC macro can give by ABB drive.

Here is a little complicated to provide more precise details, because I do not know much about your project


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1

As Flavio recommended, the easiest way is to use Pump Control functions in VFD, they are already prepared for that kind of tasks.

In case you want to realize pump control trough PLC, that means you have to create similar logic in the PLC.

You have to send a speed setpoint from PLC to each VFD, from one PID in the PLC, with process variable = common header, and output 70-100%. You have to take in consideration MIN and MAX permissable setpoint for the pumps (usually min=70 max=100% of nominal speed of the pumps, when they produce something - check with the pump people).

Lets assume only P1 is working, output of the PID is going directly as a setpoint for P1. When the demand increases, PID will increase the setpoint to P1.

When the PID output is nearly 100%, you will need to start P2 also (by additional logic with limit value and hysterezis for example).

After P2 is started, you have to divide PID output by 2 and send it to P1 and P2.

For example P1 and P2 will receive 100-70=30/2=15+70=85% (have to check pump characteristics and ensure approx. the same flow after the transfer from P1 to P1+P2)

That is for me load sharing (otherwise you fix P1 to 100% and start P2 from 70%, but no load sharing here)

In same logic you are going up for P3..., => divide the setpoint by 3. Also down when demands decreases.

For more advanced load sharing, you have to read the current of each pump, and make a correction in speed reference for each pump, in order to equalize the pump's currents too (as you may be know, even the same pumps have a different characteristics, especially when work on the same header).

Of course, this description is like idea only.

You will need to precize it during programming and commissioning.

kstoilov   

answered 2 months ago


 


By vigneshwaran92rce on 9/28/2017 | Like (0) | Report

Thank you so much kstoilov


By kstoilov on 9/28/2017 | Like (0) | Report

Hope to understand my idea !
Good luck


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