[TRNSYS-users] TRNSYS-users Digest, Vol 30, Issue 21

[David Bradley]

Ming,
   The first thing to do is to make sure that you are using a small 
enough time step. If you are making control decisions once per hour 
(1 hour time step) it is likely that your controller will be 
unstable. You might try a 5 minute time step. You might also try to 
increase the dead bands on your controller so that the pumps do not 
turn on until there is a bigger temperature difference between the 
outlet of the collector and the bottom of the storage tank. Lastly, 
you can delay the temperature signals into your controller by one 
time step. This, in essence adds a little bit more capacitance (time 
delay) into the system and can help stabilize things greatly.
Cheers,
  David


At 15:46 6/17/2007, Ming Qu wrote:
>Dear, TRNSYS users:
>I have used type 2 - differential controller to simulate my solar 
>system control. However I noticed that the output of controller is 
>not always same as I expected. I programmed the control logic in the 
>spreadsheet and compared the calculated control signal with TRNSYS 
>type 2 outputs. My control parameter is the outlet temperature of 
>solar field. Since the temperature is not very stable due to 
>unstable solar radiation, the controller seems confused by the 
>oscillated the temperature. Is there anybody experience similar 
>situation like me? How did you resolve it? Is that meaning that what 
>I got is the best effort of TRNSYS controller?
>
>Please let me know.
>
>Thanks
>
>Ming
>
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>TRNSYS-users mailing list
>TRNSYS-users at engr.wisc.edu
>https://www.cae.wisc.edu/mailman/listinfo/trnsys-users

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